JPH0821216A - Engine valve - Google Patents

Abstract

PURPOSE:To provide an engine valve wherein abrasion of a valve shaft part to a valve guide is a little, and the processing cost is low. CONSTITUTION:In a titanium alloy-made engine valve wherein a valve head 3 is continuously provided on a valve shaft 2, oxidation layers 8 from which scale oxide is removed are formed on at least a valve face surface part 3A of the valve head 3, a shaft end surface part 2B of the valve shaft 2, the upper slide-contact range 5b with which the upper end of the valve guide is brought in slide-contact, and the lower slide-contact range 5a with which the lower end of the valve guide is brought in slide-contact out of the slide-contact range with which the valve guide of the outer peripheral surface part 2a of the valve shaft 2 is brought in slide-contact, and a small diameter part 6 is provided on the valve shaft 2 part between the upper slide-contact range 5b and the lower slide-contact range 5a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine valve used as an intake valve or an exhaust valve in an internal combustion engine.

[0002]

2. Description of the Related Art Generally, as an intake / exhaust valve of an internal combustion engine, a mushroom type engine valve having a valve shaft connected to a valve shaft is used, and conventionally, heat resistant steel is generally used as a material thereof. Recently, a titanium alloy, which is lighter in weight and has better heat resistance than this heat-resistant steel, has come to be used in engine valves of lacing specification vehicles and the like. However, this titanium alloy needs to be subjected to a surface treatment for imparting abrasion resistance to the sliding surface portion and the like. As this method, for example, a finished product is disclosed as disclosed in JP-A-62-256956. There has been proposed a surface treatment method in which an oxide surface treatment layer having high hardness is formed on the surface of a product by heating the product in a furnace containing oxygen.

[0003]

However, in the above surface treatment method, since the surface treatment layer having a hard and brittle oxide scale on the surface portion is formed over the entire length of the valve shaft portion having the same diameter, the surface treatment layer before the oxidation treatment is formed. It takes time and effort to finish the valve shaft, and since the top surface of the surface treatment layer has a hard and brittle oxide scale layer, it is extremely aggressive to the valve guide with which the valve shaft slides, and the valve guide It is liable to cause early wear, and in order to prevent this, it is necessary to perform finishing such as superfinishing over the entire length of the valve shaft portion after the oxidation treatment, which increases the processing cost. Further, there is a problem that the oxide scale peels off during the operation of the engine valve to cause wear and seizure of the valve guide.

The present invention solves the above-mentioned problems of the prior art, and it is an object of the present invention to provide an engine valve made of titanium alloy in which the valve shaft portion and the valve guide are less worn and the processing cost is low. .

[0005]

An engine valve of the present invention is a titanium alloy engine valve in which a valve stem is connected to a valve shaft, at least a valve face surface portion of the valve shaft and a shaft end surface of the valve shaft. Part, and of the sliding contact range in sliding contact with the valve guide on the outer peripheral surface of the valve shaft, an upper sliding contact range in which the upper end of the valve guide slides, and a lower sliding contact range in which the lower end of the valve guide slides, An oxide layer is formed by removing the oxide scale, and a small diameter portion is provided in the valve shaft portion between the upper sliding contact area and the lower sliding contact area.

The titanium alloy used in the present invention is T
i-6Al-4V, Ti-5.5Al-4Sn-1Nb
-0.3Mo, Ti-6Al-2.75Sn-4Zr-
0.4Mo, Ti-6Al-2Sn-4Zr-2Mo,
Titanium alloys of various compositions such as Ti-6Al-2Fe-0.1Si can be used.

The oxide layer in the present invention means a compound layer mainly composed of TiO ₂ which is a compound of a titanium alloy component, oxygen and nitrogen in the air, and has a hardness of Vickers hardness of 500 or more. It is a layer. By heat treatment in an oxidizing atmosphere, an oxide layer 8 is formed on the valve body material 7 as shown in FIG. 2, and its surface is covered with an oxide scale 9 made of a hard and brittle titanium oxide.
In the present invention, the oxide scale 9 is removed to expose the oxide layer 8 to obtain a product.

Regarding the surface roughness of the outer peripheral surface of the valve shaft of the present invention which is in sliding contact with the valve guide of the valve shaft and the oil seal lip, a ten-point average roughness of less than 0.1 μmRz is expensive to machine and 5.0 μmRz. If it exceeds the above range, abrasion of the valve guide and the oil seal lip is likely to proceed, so 0.1 to 5.0 μmRz is preferable. This surface roughness is usually obtained by finishing the large diameter portion of the valve shaft of the valve body material before the oxidation treatment to the above surface roughness, and the oxidation scale depends on the degree of formation of the oxidation scale during the oxidation treatment. -If the surface roughness deteriorates after the removal of the solder, it can be obtained by performing a finishing process such as buffing again.

[0009]

In the engine valve of the present invention, when the valve shaft portion is inserted into the valve guide and incorporated in the engine, the oxidation layers provided in the upper sliding contact range and the lower sliding contact range of the outer peripheral surface of the valve shaft are The valve shaft is prevented from being worn by sliding contact with the guide, and since the oxide layer is not covered with the oxide scale layer, rapid wear of the valve guide is not caused.

Further, the oxide layer formed on the valve face surface is
The progress of beating wear due to the collision of the valve face surface portion with the valve sheet during engine rotation is suppressed, and the oxide layer formed on the shaft end surface portion of the valve shaft has a rocker arm or a shaft end surface portion during engine rotation. Suppresses the progress of knocking wear due to collision with the lifter.

Further, there is a small-diameter portion between the upper sliding contact area and the lower sliding contact area of the valve shaft, and since finishing processing is not required for this small-diameter portion, the valve is formed before the oxidation treatment and, if necessary, after the oxidation treatment. Finishing the shaft in a short time. In the intake valve,
If abrasion powder of the valve shaft or valve guide is generated at the upper part of the valve guide, or if carbon contained in blow-by gas is generated, these foreign matters are generated between the inner peripheral surface of the valve guide and the small diameter part. Since it enters the empty space, sticking accidents between the valve shaft and the valve guide are prevented. In addition, in the exhaust valve, when abrasion powder of the valve shaft or the valve guide is generated in the upper part of the valve guide, or combustion products are generated in the combustion chamber where the valve umbrella opens and closes, these foreign matters are also released in the same manner as the intake valve. Since it enters the space between the inner peripheral surface of the guide and the small diameter portion, sticking accidents between the valve shaft and the valve guide are prevented.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2, reference numeral 1 denotes a valve body of an intake valve, which has a mushroom shape in which a valve umbrella 3 is integrally connected to one end of a valve shaft 2 and is made of a titanium alloy. Diameter (diameter of large diameter part) 6mm
The upper end portion 12b of the valve guide 12 is slidably attached to the valve shaft 2 of the valve guide 12 in a sliding contact range 5 (described later) in which the valve shaft 2 is slidably contacted with the valve guide 12 (see FIGS. 3 and 4) by the reciprocating opening / closing motion when the valve shaft 2 is installed in the engine. Upper sliding contact area 5b in contact with the valve guide 1
A small-diameter portion 6 having a diameter of 5.5 mm is provided between the lower end portion 12a of the second member 2 and a lower sliding contact area 5a (both of which will be described later) in sliding contact.

FIGS. 3 and 4 show a state in which the valve body 1 is incorporated in a cylinder block 11 portion of an engine. In FIG. 3, reference numeral 12 is a metal valve guide fixed to the cylinder block 11. The large-diameter portion 2 of the valve shaft of the body 1 is fitted with a small clearance. 13 is an oil seal attached to the upper end of the valve guide 12 by a ring 13a.
The oil seal lips 13b are in sliding contact with the outer peripheral surface portion 2A (outer peripheral surface portion of the large diameter portion) of the valve shaft 2. Reference numeral 15 is an intake passage, 16 is a valve seat on which the valve umbrella 3 is seated, 17 is a retainer fitted to the shaft head of the valve body 1 by a cotter 18, 19
Is a valve spring.

FIG. 3 shows the valve fully closed state in which the valve face surface portion of the valve umbrella 3 is seated on the valve sheet 16, and FIG. 4 shows that the shaft head 4 portion is pushed down by a cam shaft (not shown) so that the valve body 1 is closed. Shows the state where the valve reaches the lower end position and is fully opened. Then, from the position a on the valve shaft 2 corresponding to the lower end surface of the valve guide 12 in FIG. 3 (valve fully closed state) to the valve shaft 2 corresponding to the upper end surface of the valve guide 12 in FIG. 4 (valve fully open state). The range up to the position b is the sliding contact range 5 that is in sliding contact with the valve guide 12 of the valve shaft 2. In this sliding contact range 5, a range from a position c on the valve shaft 2 near the end of the valve shaft 2 by a predetermined distance Q (1 mm in this embodiment) from the lower end surface of the valve guide 12 in FIG. 4 to the position a. Is the lower sliding contact range 5a, and the range from the position d on the valve shaft 2 closer to the valve umbrella to the position b by a predetermined distance R (1 mm in this embodiment) from the upper end surface of the valve guide 12 in FIG. In the upper sliding contact range 5b, the small diameter portion 6 may be provided between the upper sliding contact range 5b and the lower sliding contact range 5a, but in this embodiment, the lower end position of the upper sliding contact range 5b. over the entire range 21 between d and the upper end position c of the lower sliding contact range 5a,
A small diameter portion 6 is provided.

The outer peripheral surface portion 2A of the valve shaft 2 of the valve body material 7 before the oxidation treatment of the valve body 1 having the above-mentioned shape is provided with the small diameter portion 6 so that the surface roughness becomes about 1.5 μmRz by the grinding process. Except for 2 parts of the valve shaft, the entire length is finished. In addition, this finishing process is performed at least in the lower sliding contact area 5a and FIG.
Oil seal lip 13b when the valve is fully open
The sliding contact range 10 from the position e on the valve shaft 2 to the position d (i.e., the upper sliding contact range where the valve shaft 2 is in sliding contact with the valve guide 12 and the oil seal lip 13b) may be performed.

The surface of the valve body material 7 which has been finished into the above-mentioned shape is subjected to an oxidation treatment described later, and an oxide layer 8 is provided on the entire surface of the valve body 1. If the thickness of the oxide layer 8 is less than 5 μm, the oxide layer (hardened layer) is thin and the wear resistance of each part is insufficient, and if it exceeds 100 μm, the fatigue strength and toughness are greatly reduced, and the valve is not operated during engine operation. Since the shaft 2 may be cut off or the valve head 3 may be damaged by fatigue, the above 5 to 1
The thickness is preferably 00 μm.

The oxide layer 8 is formed as follows. First, the valve body material 7 is subjected to a heat treatment at a temperature of 600 to 900 ° C. for several minutes to several hours in an oxidizing atmosphere furnace such as an atmospheric furnace to give a thickness of 5 to 100 μm as shown in FIG.
The oxide layer 8 is formed on the entire surface of the valve body 1. On the surface of the oxide layer 8, there is formed an oxide scale 9 having a thickness of about 1 to 10 μm and made of titanium oxide which is hard, brittle and easily peeled off. If the valve body 1 is used with the oxide scale 9 left, the valve guide portion may be worn or seized. Therefore, according to the present invention, the oxide scale 9 is removed to expose the oxide layer 8. And Shot blasting, buffing, and the like are available as the removing method. Further, after the oxide scale 9 is removed, the oxide layer 8 on the outer peripheral surface portion 2A of the valve shaft 2 is removed.
If the surface roughness is deteriorated, finish processing such as buffing is performed to obtain the product.

The thickness of the above-mentioned oxide layer 8 is determined by the temperature and the treatment time of the above-mentioned heat treatment, but when the temperature exceeds 900 ° C., the valve shaft 2 is bent or deformed, which is preferable. Further, if the temperature is less than 600 ° C., a passive film is formed, which is inefficient in forming the oxide layer 5, which is not preferable. Within the range of 600 to 900 ° C, 85
If the temperature exceeds 0 ° C, the oxide scale 9 increases, and if the temperature is lower than 800 ° C, it takes too long to form the thin oxide layer 8. Therefore, the temperature is most preferably 800 to 850 ° C.

When the valve shaft 2 portion of the valve body 21 is used by inserting it into the valve guide 12, the upper sliding contact range 5b and the lower sliding contact range 5a, which are the large diameter portions of the valve shaft 2, are in contact with the valve body 1. Despite the vertical movement of the valve guide 12, the valve guide 12 is always slidably in contact with the inner surfaces of the upper end 12b and the lower end 12a of the valve guide 12 to keep the valve shaft 2 at a predetermined position without misalignment, and the oxide layer 8 reduces the abrasion of the valve shaft 2. The outer peripheral surface portion 2A which is not covered with the oxide scale 9 and exposes the oxide layer 8 suppresses abrasion of the inner peripheral surface of the valve guide 12 and the oil seal lip 13b to a small amount. Further, the oxide layer 8 formed on the valve face surface portion 3A of the valve umbrella 3 suppresses the progress of beating wear of the valve face surface portion due to the collision with the valve sheet 16, and the shaft end surface portion 2 of the valve shaft 2 is suppressed.
The oxide layer 8 formed on B suppresses the progress of knocking wear of the shaft end surface due to collision with a rocker arm or a lifter.

Further, abrasion powder of the valve shaft 2 or the valve guide 12 is generated above the valve guide 12, carbon contained in blow-by gas or the like is generated, and combustion products are generated in a combustion chamber in which the valve umbrella is opened and closed. When foreign matter occurs (in the case of an exhaust valve) and enters the valve guide 12, these foreign matters enter the space (clearance) 22 between the inner peripheral surface of the valve guide 12 and the small diameter portion 6, so that the valve shaft It is possible to prevent the sticking accident between the valve guide 12 and the valve guide 12.

The present invention is not limited to the above-described embodiment. For example, the small-diameter portion 6 of the valve shaft 2 has a partial range between positions c and d like the valve body 31 shown in FIG. 21 may be provided. In addition, like the valve element 32 shown in FIG.
The valve shaft portion above the sliding contact range 10 including the upper sliding contact range 5b and the valve shaft portion below the lower sliding contact range 5a may also have a small diameter. The processing range (large diameter range) is particularly small, and finish processing can be done in a shorter time. In these figures, the same parts as those in FIG. 1 are designated by the same reference numerals.

In the above embodiment, the oxide layer 8 is formed on the entire surface of the valve body 1, but the oxide layer 8 is in contact with the mating member of the valve body 1, that is, the shaft end surface portion 2B of the valve shaft 2. The valve face 3A of the valve umbrella 3, the lower sliding contact area 5a of the valve shaft 2,
And the upper sliding contact range 5b (the sliding contact range 10 from the positions e to d is more preferable because abrasion due to the sliding contact of the oil seal lip 13b can be reliably prevented). In this case, the oxide layer 8 is formed by, for example, a partial oxidation method in which irradiation of high-density energy such as a laser or spraying of a flame burner is performed only on a necessary portion of the valve body in an oxidizing atmosphere. be able to. According to this partial oxidation method, since the amount of heat input during the oxidation treatment is small, the distortion of the valve body, particularly the distortion of the valve shaft 2 is very small, the frictional resistance with the valve guide 12 is small, and the operating response of the engine valve is small. improves.

The present invention can also be applied to an exhaust valve of an internal combustion engine.

[0024]

As described above, according to the present invention,
Since the oxide layer is exposed in the upper sliding contact area and the lower sliding contact area of the outer peripheral surface of the valve shaft without being covered by the oxide scale, wear of the valve shaft due to sliding contact with the valve guide and valve guide Little wear.

Since there is a small-diameter portion between the upper sliding contact area and the lower sliding contact area of the valve shaft, the finishing work of the valve shaft can be completed in a short time and the processing cost can be reduced, and the valve can be installed above the valve guide. When abrasion powder of the shaft or valve guide is generated, carbon contained in blow-by gas, etc. is generated or combustion products are generated, these foreign matters are generated between the inner peripheral surface of the valve guide and the small diameter portion. Since it will enter the empty space, the accident of sticking the valve shaft and the valve guide is prevented, and the malfunction of the engine when restarting the vehicle after being left for a long time is also eliminated.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view of an engine valve showing an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a valve body surface portion showing a process of forming an oxide layer in FIG.

FIG. 3 is a vertical cross-sectional view of a valve fully closed state of an incorporated portion in which the engine valve of FIG. 1 is incorporated in an engine.

FIG. 4 is a vertical cross-sectional view of an assembled portion of the engine valve of FIG. 1 assembled into an engine in a fully opened state.

FIG. 5 is a partially cutaway front view of an engine valve showing another embodiment of the present invention.

FIG. 6 is a partially cutaway front view of an engine valve showing still another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Valve body, 2 ... Valve shaft, 2A ... Outer peripheral surface part, 2B ... Shaft end surface part, 3A ... Valve face surface part, 5 ... Sliding contact range, 5a ... Lower sliding contact range, 5b ... Upper sliding contact range, 6 ... small diameter part, 8 ... oxide layer, 12 ... valve guide, 12a ... lower end, 12b ... upper end, 13b ... oil seal lip, 31 ... valve body, 32
… Valve disc.

Claims (2)

[Claims] 1. A titanium alloy engine valve in which a valve stem is connected to a valve shaft, at least a valve face of the valve umbrella.
Of the upper end of the valve guide and the lower end of the valve guide in the sliding contact range of the outer peripheral surface of the valve shaft and the valve guide of the outer peripheral surface of the valve shaft. An engine in which an oxide layer from which an oxide scale has been removed is formed in a lower sliding contact range in sliding contact, and a small diameter portion is provided in the valve shaft portion between the upper sliding contact range and the lower sliding contact range. valve. 2. The surface roughness of the outer peripheral surface portion which is in sliding contact with the valve guide of the valve shaft and the oil seal lip is 0.1 to 5.0.
The engine valve according to claim 1, wherein the engine valve is μmRz.