JP3192879B2 - Ceramic butterfly valve and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic butterfly valve and a method of manufacturing the same.

[0002]

2. Description of the Related Art A valve body, a valve shaft and a valve body are formed of ceramics, and the valve shaft is supported by a valve shaft insertion hole formed in the valve body so as to be slidable about the axis of the valve shaft. Ceramic butterfly valves are well known (Jpn.
No. 175663). In this butterfly valve, the durability and chemical resistance of the butterfly valve are improved as much as possible by forming the valve body, valve stem and valve body from ceramics. Also, in this butterfly valve, a ceramic cylindrical member is arranged in the valve shaft insertion hole, and the valve shaft is supported by inserting the valve shaft into this cylindrical member, so that fluid flowing through the butterfly valve is as small as possible. We do not leak to the outside.

[0003]

However, in the above-mentioned butterfly valve, when the gap between the sliding surface of the valve shaft and the sliding surface of the cylindrical member is reduced to prevent the fluid from leaking further to the outside, the opening / closing operation of the valve is performed. Therefore, a large valve opening force is required to perform the operation, and there is a problem that abnormal noise is generated between the sliding surface of the valve shaft and the sliding surface of the cylindrical member when the butterfly valve is opened and closed. In order to prevent the generation of the abnormal noise, it is conceivable to perform processing to reduce the surface roughness of each sliding surface, but in this case, there is a problem that the cost is increased.

[0004]

According to a first aspect of the present invention, at least a valve body and a valve shaft are formed of ceramics, and a valve shaft insertion hole is formed in the valve body. In a ceramic butterfly valve adapted to slidably support the valve shaft around the axis of the valve shaft, at least one of a sliding surface of the valve shaft and a sliding surface of the valve shaft insertion hole. A boron nitride layer comprising a group of boron nitride particles adhered on the surface of the valve shaft;
For the gap between the moving surface and the sliding surface of the valve shaft insertion hole,
The ratio of the thickness of the initial layer for forming the boron nitride layer to 0.
It is set in the range of 1 to 0.8 . Second departure
According to the first invention, in the first aspect, the sliding surface of the valve shaft is
The above-described nitriding method for the gap between the sliding surfaces of the valve shaft insertion holes
The ratio of the average particle diameter of elementary particles is set to 0.4 or less.
According to a third aspect of the present invention, a mixed solution obtained by mixing boron nitride particles with alcohol, pure water, and a binder is used to slide a valve shaft constituting a ceramic butterfly valve. The entire surface is coated on at least one of a moving surface and a sliding surface of a valve shaft insertion hole formed in the valve body of the butterfly valve, and boron nitride particles are temporarily coated on the sliding surface. After forming the initial layer to be held temporarily, heating is performed to form a boron nitride layer composed of boron nitride particles , and the sliding surface of the valve shaft and the sliding of the valve shaft insertion hole are formed.
The ratio of the thickness of the initial layer to the gap between the moving surfaces is 0.1
It is set in the range from 0.8 to 0.8 . In the third invention according to the fourth invention, the ratio of the average particle diameter of the particles of the boron nitride for the gap between the sliding surfaces of the sliding surface and the valve shaft insertion hole of the valve shaft 0.4 It is set as follows.

[0005]

According to the first aspect of the invention, the boron nitride particle layer is provided on at least one of the sliding surface of the valve shaft and the sliding surface of the valve shaft insertion hole. As the operation is repeatedly performed, the shearing force is applied to the boron nitride particles due to the relative rotation between the sliding surface of the valve shaft and the sliding surface of the valve shaft insertion hole, and the sliding gradually occurs in the boron nitride particles, And the respective slices partially overlap each other and sequentially displace in the circumferential direction, so that the sliding surface of the valve shaft and the sliding surface of the valve shaft insertion hole are nitrided over the entire surface. Uniformly covered with elemental flakes. here,
Initial clearance between the sliding surface of the valve shaft and the sliding surface of the valve shaft insertion hole
The thickness ratio of the initial layer is such that the boron nitride layer separates from the sliding surface.
Ideal for forming a uniform boron nitride layer while preventing cracking
It is determined in the range. In the third aspect of the present invention, the alcohol is contained in the mixture, so that the boron nitride particles are well dispersed in the mixture, and the mixture contains pure water, so that the concentration of the mixture is maintained substantially constant. The initial layer is formed by temporarily holding the boron nitride particles over the entire sliding surface on the sliding surface by the binder in the mixed solution, and then a boron nitride particle group through a heating process is formed. Is formed. Again, the valve stem
Initial layer for the gap between the sliding surface of the valve and the sliding surface of the valve shaft insertion hole
The thickness ratio of the boron nitride layer
The optimal range for forming a uniform boron nitride layer while blocking
It is determined in the box. In the second or fourth invention, the ratio of the average particle diameter of the boron nitride particles to the gap between the sliding surface of the valve shaft and the sliding surface of the valve shaft insertion hole is determined by the following formula. The range is set to an optimum range for forming a uniform boron nitride layer while preventing the formation.

[0006]

1 and 2, reference numeral 1 denotes a butterfly.
A valve, 2 is a cylindrical valve body, 3 is formed on the valve body 2
For example, slide around the axis KK in the pair of valve shaft insertion holes 4.
The movably supported valve shaft 5 is joined to the valve shaft 3 and is circular.
Each shows a plate-shaped valve element. In this embodiment,
The valve body 2, valve stem 3, and valve body 5 are made of silicon nitride (Si) _ThreeN
_Four), Silicon nitride such as SIALON
It is formed from a sintered body. The valve shaft 3 has a circular cross section.
However, the valve element joint 3 to which the valve element 5 is joined
b has a semicircular cross section. See also FIG.
Then, at one end of the valve shaft 3 located outside the valve body 2,
A metal washer 6 is attached to the outside of the valve body 2.
For example, a metal collar 7 is attached to the other end of the valve shaft 3 to be placed.
And the washer 6 and the collar 7
3 is prevented from moving in the direction of the axis KK. Sa
Furthermore, a metal lever 8 is attached to the collar 7, for example.
When the lever 8 is driven, the valve shaft 3
Is rotated around KK, thus opening and closing the butterfly valve 1
Valve operation is performed.

Referring to FIG. 3, which is an enlarged view of the portion A in FIG. 1, the nitriding is applied on the entire sliding surface 3a of the valve shaft 3 without any binder. A boron nitride layer 9 composed of boron (BN) particles 10 is formed. In the example shown in FIG. 3, the boron nitride layer 9 is formed only on the sliding surface 3a of the valve shaft 3, but the boron nitride layer 9 is formed on the sliding surface 4a of the valve shaft insertion hole 4. Only, or the boron nitride layer 9
To the sliding surface 3a of the valve shaft 3 and the sliding surface 4a of the valve shaft insertion hole 4.
May be formed on both surfaces.

Next, a method of manufacturing the ceramic butterfly valve 1 of the present invention will be described. First, a mixed liquid obtained by mixing boron nitride particles (purity of 99% or more) with alcohol, pure water, and a binder is applied over the entire sliding surface 3a of the valve shaft 3 by spraying, for example, by air pressure. I do. It is preferable to determine the mixing ratio (weight ratio) of the mixed liquid as follows, for example. Boron nitride particles: 1 Alcohol: 1 to 3 Pure water: 5 to 10 Binder: 0.5 to 2 By setting the mixture at such a mixing ratio, the thickness of the initial layer 15 described later can be easily set. be able to.

In this embodiment, since the mixture contains alcohol, for example, ethanol, the boron nitride particles can be well dispersed in the mixture. However, if pure water is not mixed into the mixed solution, that is, if boron nitride particles are mixed with only alcohol to obtain a mixed solution, the concentration of the mixed solution is kept almost constant because the volatility of the alcohol is high. Becomes difficult. On the other hand, in the present embodiment, since pure water is contained in the mixture together with the alcohol, it is easy to maintain the concentration of the mixture almost constant while dispersing the boron nitride particles well in the mixture. can do. Binder in the mixture, for example, PVA
(Polyvinyl alcohol) acts to temporarily hold the boron nitride particles 11 in the mixed liquid on the sliding surface 3a of the valve shaft 3, and therefore, as shown in FIG.
An initial layer 15 is formed thereon.

Next, after passing through a drying step, the valve shaft 3 is connected to the valve body 2.
And then positioned. At this time, since the boron nitride particles 11 in the initial layer 15 are held by the binder, the valve shaft 3 is inserted into the valve shaft insertion hole 4, and the boron nitride particles 11 slide on the valve shaft 3 when positioning. Detachment from the moving surface 3a is prevented. Next, the valve element 5
Are arranged in the valve joint 3b of the valve shaft 3 and positioned. Silicon metal that acts as a bonding agent is disposed in the valve body bonding portion 3b in advance. Next, a preheating step is performed, whereby the binder is removed from the initial layer 15 by evaporating it together with alcohol and pure water, and thus, as shown in FIG. A boron nitride layer 9 composed of a group of boron nitride particles adhered to the entire surface of the sliding surface 3a of the valve shaft 3 is formed. At this time, it is considered that the boron nitride particles 11 constituting the boron nitride particle group 10 adhere to the sliding surface 3a of the valve shaft 3 by, for example, Van der Waals force. Next, a heating step is performed under reduced pressure, whereby the valve element 5 is joined to the valve element joining portion 3b. Next, the washer 6 and the collar 7 are attached to the valve shaft 3, and then the lever 8 is attached to the collar 7, so that the butterfly valve 1 is manufactured.

As in this embodiment, the sliding surface 3 of the valve shaft 3
When the boron nitride layer 9 is formed on the a, a large valve-opening force is not required when the butterfly valve 1 is opened and closed because the boron nitride has a lubricating action. The generation of abnormal noise between the surface 3a and the sliding surface 4a of the valve shaft insertion hole 4 can be prevented. Furthermore, boron nitride is excellent in lubricity and heat resistance, and additionally, is chemically stable, so that it does not chemically react with the fluid flowing in the butterfly valve 1, for example, does not undergo an oxidation reaction. Operation can be ensured for a long time.

As described above, no binder exists in the boron nitride layer 9 in this embodiment. Therefore, as the opening / closing operation of the butterfly valve 1 is repeatedly performed, that is, as the sliding between the sliding surface 3a of the valve shaft 3 and the sliding surface 4a of the valve shaft insertion hole 4 is repeatedly performed, the valve shaft is repeated. 5A, a shearing force f is applied to the boron nitride particles 11 by the relative rotation between the sliding surface 3a of FIG. 3 and the sliding surface 4a of the valve shaft insertion hole 4. As shown in FIG. 5B, the boron nitride particles 11 are divided into a plurality of boron nitride flakes 12, and the respective boron nitride flakes 12 partially overlap with each other in the circumferential direction. In the deformed layer 1 obtained by deforming the boron nitride particles 11 by applying the shearing force f.
5 covers the entire sliding surface 3a of the valve shaft 3 and the sliding surface 4a of the valve shaft insertion hole 4 as shown in FIG. The deformable layer 13 spreads uniformly on each of the sliding surface 3a of the valve shaft 3 and the sliding surface 4a of the valve shaft insertion hole 4, so that the stable operation of the butterfly valve 1 is further ensured for a long time. be able to. Moreover, it is considered that the boron nitride flakes 12 constituting the deformable layer 13 are pressed on the sliding surface 3a of the valve shaft 3 and the sliding surface 4a of the valve shaft insertion hole 4, respectively.
Therefore, as the opening / closing operation of the butterfly valve 1 is repeatedly performed, the deformation layer 13 is prevented from peeling off from these surfaces, and as a result, the stable operation of the butterfly valve 1 can be further ensured for a long period of time. Note that, even if the opening and closing operation of the butterfly valve 1 is performed only a few times after removing the binder, the deformation of the boron nitride 11 can be caused and the deformed layer 13 can be formed.

FIG. 6 shows the E on the sliding surface 3a of the valve shaft 3 after the opening and closing operation of the butterfly valve 1 has been performed about 60,000 times.
FIG. 4 is a diagram showing a result of PMA (electron probe micro analyzer) analysis. Referring to FIG. 6, it can be seen that the number of atoms of boron is much larger than the number of atoms of silicon constituting the valve stem 3 (about 7 to 8 times). Therefore, the sliding surface 3a of the valve shaft 3 is entirely covered with the deformed layer 15 made of boron nitride, and even after the opening and closing operation of the butterfly valve 1 has been performed for a long time, the deformed layer 15 Is held on the sliding surface 3a of the valve shaft 3.

FIG. 7 shows the ratio of the thickness t (see FIG. 4) of the initial layer 15 to the gap T (see FIG. 4) between the sliding surface 3a of the valve shaft 3 and the sliding surface 4a of the valve shaft insertion hole 4. And experimental results showing the relationship between the pressure and the valve opening pressure. In FIG. 7, the valve opening pressure represents the valve opening force of the butterfly valve 1, and the smaller the valve opening pressure, the more uniform the boron nitride layer 9 is formed. The valve opening pressure is a value measured after performing the opening and closing operation of the butterfly valve 1 several times after removing the binder. Referring to FIG. 7, when the thickness t / gap T is in the range of about 0.1 to 0.8, the valve opening pressure is 400 (mm).
Hg). Valve opening pressure is 4
When it is smaller than 00 (mmHg), abnormal noise is generated between the sliding surface 3a of the valve shaft 3 and the sliding surface 4a of the valve shaft insertion hole 4 when the valve shaft 3 is rotated around the axis KK. Does not occur, and good sliding between the sliding surface 3a of the valve shaft 3 and the sliding surface 4a of the valve shaft insertion hole 4 is ensured. Therefore, it is preferable to set the thickness t / gap T in a range from about 0.1 to 0.8. If the thickness t / gap T is less than about 0.1,
The deformation layer 13 described with reference to FIG.
a and the sliding surface 4a of the valve shaft insertion hole 4 are not uniformly formed on each surface, thus increasing the valve opening pressure. On the other hand, when the thickness t / gap T is larger than about 0.8, the thickness of the deformable layer 13 is increased, so that the deformable layer 13 is easily cracked. The moving surface 3a and the sliding surface 4a of the valve shaft insertion hole 4 are easily separated from each other, and thus the valve opening pressure is increased. If the thickness t / gap T is larger than about 0.8, it becomes difficult to position the valve shaft 3 in the valve shaft insertion hole 4. In this embodiment, the thickness t
Is set to about 10 to 60 μm.

FIG. 8 shows boron nitride particles 1 with respect to gap T.
It is an experimental result showing the relationship between the ratio of the average particle diameter d of the boron nitride particles 11 of 0 and the valve opening pressure. Referring to FIG. 8, when the average particle diameter d / gap T is about 0.4 or less, the valve opening pressure becomes 400.
(MmHg). Therefore, it is preferable to set the average particle diameter d / gap T to about 0.4 or less. When the average particle diameter d / gap T is larger than about 0.4, the thickness of the deformable layer 13 increases, and the valve opening pressure increases for the above-described reason. In this embodiment, the average particle diameter d is set to about 5 to 30 μm.

More preferably, the average particle diameter d / gap T is set to about 0.4 or less while the thickness t / gap T is set in the range of about 0.1 to 0.8.

FIG. 9 shows a case where the ceramic butterfly valve 1 shown in FIG. 1 is applied to an internal combustion engine. In the example shown in FIG. 9, the butterfly valve 1 is arranged in the engine exhaust passage 20. In this case, high-temperature exhaust gas flows through the butterfly valve 1, and the surface temperature of the sliding surface 3a of the valve shaft 3 and the sliding surface 4a of the valve shaft insertion hole 4 becomes about 700 ° C. However, the deformation layer 13 made of boron nitride is formed on each of the sliding surface 3a of the valve shaft 3 and the sliding surface 4a of the valve shaft insertion hole 4 as described above. Because of its excellent heat resistance, the deformation layer 13 is prevented from peeling off from the sliding surface 3a of the valve shaft 3 and the sliding surface 4a of the valve shaft insertion hole 4. Further, since boron nitride is chemically stable, it is not oxidized by oxygen in the exhaust gas. Therefore, the deformed layer 13 is separated from the sliding surface 3a of the valve shaft 3 and the sliding surface 4a of the valve shaft insertion hole 4. Is further prevented. In FIG. 9, reference numeral 21 denotes an engine body, 22 denotes an intake passage, 23 and 24 denote a pair of turbochargers, and 25 denotes a butterfly valve driving device connected to the lever 8 of the butterfly valve 1 (see FIG. 1). .

According to the present embodiment, the gap T formed between the sliding surface 3a of the valve shaft 3 and the sliding surface 4a of the valve shaft insertion hole 4 can be reduced, so that the gas flows through the butterfly valve 1. Fluid leakage to the outside can be reduced. further,
Since the processing for reducing the surface roughness of the sliding surface 3a of the valve shaft 3 and the sliding surface 4a of the valve shaft insertion hole 4 is not required, the butterfly valve 1 can be manufactured at low cost.

[0019]

According to the first aspect of the present invention, it is possible to maintain a uniform boron nitride layer on at least one of the sliding surface of the valve shaft and the sliding surface of the valve shaft insertion hole for a long period of time. As a result, stable operation of the butterfly valve can be ensured for a long period of time. In addition, the boron nitride layer slides
Form a uniform boron nitride layer while preventing peeling from the surface
Can be achieved. According to the third aspect of the present invention, the alcohol is contained in the mixture, so that the boron nitride particles can be dispersed well in the mixture, and the concentration of the mixture is substantially constant because the mixture contains pure water. Can be easily maintained. Furthermore, the boron nitride particles are temporarily held on the sliding surface by a binder in the mixed solution over the entire sliding surface to form an initial layer. The butterfly valve can be easily manufactured. Further, a uniform boron nitride layer can be formed while preventing the boron nitride layer from peeling off from the sliding surface. According to the second or fourth aspect, a uniform boron nitride layer can be formed while preventing the boron nitride layer from peeling off from the sliding surface.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a ceramic butterfly valve.

FIG. 2 is a sectional view of the butterfly valve taken along line II-II in FIG. 1;

FIG. 3 is an enlarged view of a portion A of FIG.

FIG. 4 is a partial cross-sectional view of a butterfly valve similar to FIG. 3, illustrating an initial layer.

FIG. 5 is a diagram illustrating the behavior of boron nitride particles when a deformation layer is formed.

FIG. 6 shows EP on a sliding surface of a valve shaft on which a deformed layer is formed.
FIG. 4 is a diagram showing the results of MA analysis.

FIG. 7 is a diagram showing a relationship between a ratio of a thickness of an initial layer to a gap and a valve opening pressure.

FIG. 8 is a graph showing the relationship between the ratio of the average particle diameter of boron nitride particles to the gap and the valve opening pressure.

9 is an overall view of an internal combustion engine to which the butterfly valve of FIG. 1 is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Butterfly valve made of ceramics 2 ... Valve body 3 ... Valve shaft 4 ... Valve shaft insertion hole 5 ... Valve element 9 ... Boron nitride layer 10 ... Boron nitride film 11 ... Boron nitride particles 15 ... Initial layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI // C10N 40:02 (72) Inventor Yoshimura Kunimasa 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Naofumi Tsurumaru 1-1, Yamashita-cho, Kokubu-shi, Kagoshima Prefecture Kyocera Corporation Kagoshima Kokubu Plant (56) References JP-A-61-278664 (JP, A) JP-A-61-6428 (JP, A) -15735 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 9/10 F16K 1/22

Claims (4)

(57) [Claims] At least a valve body and a valve shaft are formed of ceramics, and the valve shaft is slidably supported around an axis of the valve shaft by a valve shaft insertion hole formed in the valve body. In a ceramic butterfly valve, a boron nitride layer composed of a group of boron nitride particles adhered on at least one of the sliding surface of the valve shaft and the sliding surface of the valve shaft insertion hole is provided. Equipped with a sliding surface of the valve shaft and the valve
The above boron nitride layer for the gap between the sliding surfaces of the shaft insertion holes
The thickness ratio of the initial layer for forming
Ceramic butterfly valve set in the range up to . 2. The sliding surface of the valve shaft and the sliding of the valve shaft insertion hole.
Average particle size of the above boron nitride particles for the gap between moving surfaces
2. The ceramic according to claim 1, wherein the ratio of
Box butterfly valve. 3. The method of claim 1, wherein the particles of boron nitride are made of alcohol, pure water,
And at least one of a sliding surface of a valve shaft constituting a ceramic butterfly valve and a sliding surface of a valve shaft insertion hole formed in a valve body of the butterfly valve. After forming an initial layer that temporarily holds the boron nitride particles on the sliding surface by applying over the entire surface on the surface of the above, heating to form a boron nitride layer composed of boron nitride particles , Sliding surface of the valve shaft and the valve shaft
Ratio of the thickness of the initial layer to the gap between the sliding surfaces of the insertion holes
Is set in the range of 0.1 to 0.8 . To claim 3 which sets the ratio of the average particle diameter of the particles of the boron nitride for the gap between the sliding surfaces of the sliding surface and the valve shaft insertion hole of the valve shaft to less than 0.4 The method for producing the ceramic butterfly valve described in the above.