JPS60240854A - Piston for internal-combustion engine made of light metal - Google Patents

Abstract

PURPOSE:To improve resistance to heat and durability, by a method wherein composite reinforcement is made on the head part of a titled piston by the use of reinforcing fiber having a thermal expansion rate lower than that of a light metal, and as a portion is increased in temperature, the volume rate of reinforcing fiber is increased. CONSTITUTION:A piston 1 for a direct injection type diesel engine is formed by an aluminium alloy, and a combustion chamber dent 3, having a conical projection 5 protruded along an axis 4, is formed in the central part of a head part 2. In which case, composite reinforcement is made on the top surface of the head part 2 by the use of alumina tow having a mean fiber size of 3.2mu, a mean fiber length of 2mm., and composition of 95wt% Al2O3 and 5wt% SiO2. In which case, the volume rate of the alumina tow in first - third region, which are set, in order, around the opening end of the combustion chamber dent 3, is set to, for example, 8%, 3%, and 1%, and as a portion is increased in temperature, a thermal expansion preventing effect is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to internal combustion engines, and more particularly to light metal pistons for internal combustion engines.

The pistons of conventional internal combustion engines are generally made of aluminum alloy in order to reduce the weight of IU. However, since aluminum alloys have poor heat resistance, when an internal combustion engine is operated under severe conditions, melting damage and cracks due to thermal fatigue may occur in the head portion. In particular, it has been well known that in the piston of a direct injection diesel engine that has a combustion chamber recess in the head, cracks are likely to occur at the edge of the cylinder head side end of the combustion chamber recess due to thermal fatigue. There is. Therefore, in order to prevent such problems from occurring, it is necessary to: (1) make the edge of the cylinder head side end of the combustion chamber recess into a rounded and smooth shape; (2) perform electrolytic simulation treatment on the surface of said edge; Conventionally, methods have been proposed, such as casting a ring made of a metal with excellent high-temperature strength, such as copper alloy, and (2) providing cooling holes inside the top ring groove.

However, method (■) has the problem that the performance of the internal combustion engine decreases, method (2) has the problem that the electrolyte membrane treatment is expensive, and method (2) has the problem that the weight of the piston is high. There is also the problem that the cost increases, and the method (2) has the problem that it is difficult to manufacture the piston.

Purpose of the Invention In view of the above-mentioned problems with conventional light metal pistons for internal combustion engines, the present invention provides a piston that has excellent heat resistance and durability, and is therefore capable of improving the performance of internal combustion engines, and is relatively efficient. It is an object of the present invention to provide a lightweight light metal piston for an internal combustion engine that can be manufactured.

DESCRIPTION OF THE INVENTION According to the present invention, the above objects are: - A piston for an internal combustion engine made of a light metal, the head portion of which is composite reinforced with reinforcing fibers having a lower coefficient of thermal expansion than the light metal constituting the piston; A light metal piston for an internal combustion engine, characterized in that the volume fraction of the reinforcing fibers is increased in areas where the temperature reached during operation of the internal combustion engine is high, and a light metal piston for an internal combustion engine, The head section is compositely reinforced with multiple types of reinforcing fibers that have a lower coefficient of thermal expansion than the light metals that compose it, and has an excellent thermal expansion suppressing effect in areas that reach high temperatures during internal combustion engine operation. Enhanced #! This is achieved by a light metal piston for internal combustion engines that is compositely reinforced with A fibers.

Effects and Effects of the Invention According to the configuration as described above, the volume fraction of the reinforcing fibers is increased in areas where the temperature reached during operation of the internal combustion engine is high, and/or the area has an excellent thermal expansion suppressing effect. reinforcement su
By composite reinforcement in m, the coefficient of thermal expansion is reduced in the parts where the attained Ill is high, and this equalizes the amount of thermal expansion of each part of the head part. The occurrence of cracks due to volume differences is avoided. Further, according to the above-described configuration, the portion heated to a high temperature during operation of the internal combustion engine is reinforced with a high volume percentage.
Since it is compositely reinforced with aN or reinforcing fibers that have excellent thermal expansion suppressing effects, it is possible to reliably avoid melting loss at that location. Further, according to the above configuration, when the surface of the head portion is subjected to electrolytic membrane treatment, or when the entire head portion is compositely reinforced with high volume ratio or relatively expensive reinforcing fibers having an excellent thermal expansion suppressing effect. Compared to the above, it is possible to obtain an excellent piston without cracking or melting damage as described above.

The reinforcing fibers used in the light metal piston for internal combustion engines of the present invention include short fibers such as alumina, alumina-silica, and carbon; long fibers such as alumina, carbon, boron, and silicon carbide; and long fibers such as silicon carbide and silicon nitride. It may be voice force, and assuming that the fiber material and volume ratio are the same, the order of highest thermal expansion suppressing effect is long fiber, short fiber, and voice force,
In terms of materials, assuming that the fiber morphology and volume fraction are the same, short fibers are carbon, alumina-silica,
For alumina and long I18, carbon, silicon carbide, alumina, and boron are ranked, and for voice force, silicon nitride and silicon carbide are ranked. Further, the light metal in the light metal internal combustion engine starting piston of the present invention may be aluminum, magnesium, or an alloy containing these as main components, which have excellent adhesion to the various reinforcing fibers as described above and are light in weight.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings.

Embodiment 1 FIG. 1 is a longitudinal sectional view showing one embodiment of a piston for an internal combustion engine according to the present invention, which is configured as a piston for a direct injection diesel engine. In the figure, 1 indicates a piston, and the piston 1 is made of aluminum alloy (JIS
JM grade AC8A> is formed. The piston 1 has a combustion chamber recess 3 in the center of its head 2. A substantially conical projection 5 is provided in the center of the combustion chamber recess 3 and projects along the axis 4 . Although not shown in the figure, the surface part of the head part 2 on the side of the cylinder head, which is not shown in the figure, has an average fiber diameter of 3.2μ, an average fiber length of 21RII+, and 95wt%A: 20s. , 5wt
It is composite-reinforced with alumina short fibers ("Safil" manufactured by IC1 Corporation) having a composition of %SiO2.

A second region 6 around the opening line of the combustion chamber recess 3, a second region 7 radially around the second region, and a third region 8 radially around the second region. The volume percentages of the alumina short fibers are set to 8%, 3%, and 1%, respectively, and the alumina short fibers are substantially three-dimensionally randomly oriented. In FIG. 1, numerals 9 to 12 represent a top land, a top ring groove, a second ring groove, and an oil ring groove, respectively, and 13 receives a bottle boss.

The composite area of the alumina short fibers and the volume fraction of the alumina short fibers in the piston constructed as described above were determined as follows. First, a piston that is not compositely reinforced with reinforcing fibers such as short alumina fibers is installed in a diesel engine, and after the diesel engine has been operated for a predetermined period of time, the piston is cut along its axis and the hardness of each part of the head is measured. The degree of decrease in hardness of each part before and after operation of the diesel engine is measured, and from this, during operation of the diesel engine,
, 66□. □□□, eh. oh. - and shown in Figure 2. If the constituent materials of the piston are the same in each part,
The amount of thermal expansion is larger in the area where the reached temperature is higher.Therefore, from the temperature distribution shown in Figure 2, in order to reduce the occurrence of distortion due to temperature differences in each part of the head, The thermal expansion coefficients of regions A to D in the figure are respectively 20 x 10-8.
21Xl 0-”, 22X10-6.23X10
-'/(+(!In order to obtain
, 3%, and 1%.

The piston shown in FIG. 1 was manufactured as follows. First, in the production of a tubular heat insulating mat, an inner diameter 6 made of short alumina fibers 14 having a volume ratio of 8% and substantially three-dimensionally randomly oriented is produced by a widely used vacuum forming method.
2n+m, outer diameter 74mm.

A first ring 15 with a thickness of 7II1M is formed, and an inner diameter of 74ffi made of short alumina fibers with a volume ratio of 3% oriented in a substantially three-dimensional random manner by a method similar to this.
II11 Second ring 1 with outer diameter 8f3 mm and thickness 7I
6, and an inner diameter of 881 and an outer diameter of 106 made of alumina short fibers with a volume ratio of 1% and substantially three-dimensionally randomly oriented.
A third ring 17 having a length of 111 m and a thickness of 71 mm was formed, and the rings were fitted together to form a fiber molded body 18 as shown in FIG. 3.

Next, after heating the fiber molded body 18 to about 700°C, the fiber molded body is placed in the lower die 20 of the casting device 19 for piston casting.
aluminum alloy (JI) at about 740° C.
The molten metal 22 of S standard A C8A> was poured, and the molten metal was pressurized at a pressure of about 1000 kQ/cs' in the upper mold 23, and the pressurized state was maintained until the molten metal 22 was completely solidified. After the molten metal 22 is completely solidified, it is lowered by the knockout bottles 24 and 25! ! After taking out the solidified body from No. 20 and subjecting the thus obtained piston material to T6 heat treatment, machining such as grinding was performed to obtain an outer diameter of 102,111 m.
, the first with a length of 105 mm and a diameter of the combustion chamber recess of 64 mm.
A piston 1 as shown in the figure was used.

In order to evaluate the performance of the pistons formed as described above, two pistons each having the same dimensions and shape were prepared as described above (formed samuta pistons and composite reinforced with reinforcing fibers such as alumina short II fibers). Prepare those pistons with a cylinder bore diameter of 102 mm and a stroke of 105 m.
It was installed in a 4-cylinder, 4-cycle diesel engine with a total exhaust capacity of 34.31 cc, and a durability test was conducted for 300 hours at a rotation speed of 3800 rpm and full load. When each piston was inspected after the test, it was found that in pistons that were not compositely reinforced with short alumina fibers, numerous cracks had occurred at the edge of the cylinder head side of the recess in the combustion chamber. However, it was confirmed that no cracks were generated in the piston of the present invention formed as described above.

Embodiment 2 FIG. 5 is a longitudinal sectional view similar to FIG. 1, showing an embodiment of a piston for an internal combustion engine according to the present invention, which is also constructed as a piston for a direct injection diesel engine.

In FIG. 5, parts that are substantially the same as those shown in FIG. 1 are designated by the same reference numerals.

In this embodiment, the head portion 2 extends in the radial direction to the cylindrical outer peripheral surface of the piston 1, and in the longitudinal direction of the piston from the surface 2a of the head portion 2 to substantially the center of the second land 26. Although not shown in the figure, the average fiber diameter is 3 μm and 52 wt% At 2011148 wt%
It is compositely reinforced with alumina-silica short fibers ("Kao Wool" manufactured by Isolite Industries Co., Ltd.) having a composition of 5iOp. In particular, the first region 6 around the combustion chamber recess 3 is made of alumina-silica short m miscellaneous material with an average fiber length of 1.5 mm and a volume fraction of 10% (bulk density 0.26 (1/lJ + 3)). The second i region 7 has an average fiber length of 2.5 mm and a volume fraction of 8% (bulk density 0.21).
The third region 8 has an average m-ply length of 3.5 mm and a volume fraction of 6% (gas density 0.16 (1 /ci) Alumina-silica knowledge) is coarsely and compositely reinforced, and the alumina-1 silica short IIat11 in each region is oriented in a substantially two-dimensional random manner within a virtual cylindrical plane concentric with the axis 4. has been done. The piston according to this embodiment has the same structure as the piston according to the first embodiment described above in other respects.

The piston constructed as described above was formed as follows. First, although not shown in the figure, the average fiber length is 1.5 m.
First to third slurries were formed by dispersing three types of alumina-silica short fibers in water to which a small amount of colloidal silica was added. Next, as shown in FIG. 6C, a filter 30 consisting of a cylindrical wire mesh 27 and metal plates 28 and 29 closing both ends of the filter 30 is immersed in the slurry 31.
By carrying out the so-called vacuum forming method in which the dispersion medium inside 0 is suctioned and removed through the conduit 32 for the first to third slurries shown in above), the inner diameter is 64 mm and the outer diameter is 104 + n.
1Il, a cylindrical body with a length of 120 mm is formed, a part of the inner circumferential surface of the cylindrical body is cut off, and the cylindrical body is dried, so that the thickness is reduced from the radially inner side as shown in FIG. are 5 m1R, 6 mm19 m1ll, respectively, and the average #li fiber length is 5111111° and the volume fraction is 10%, and the average fiber length is 2. 5
A fiber molded body 37 was formed from three fiber H layers 34 to 36, each consisting of alumina-silica short fibers having an average fiber length of 3.51 mm and a volume fraction of 6%, and alumina-silica short fibers having a volume fraction of 6%. Next, using this MIN molded body 37, the case of the above-mentioned Example 1'! ″n, I (7) iti% JI
* 31 FI K J: ') e 7 h > *
'tK 'e JF5 a I-・T6 for the material
After heat treatment, machining such as grinding was performed to obtain a piston 1 as shown in FIG.

The piston thus formed was assembled into the same diesel engine as that used in Example 1 above, and a durability test was conducted under the same operating conditions as in Example 1. As a result, the combustion chamber It was confirmed that no cracks were generated at the edge of the cylinder head side end of the recess 3. Further, the amount of wear of the top ring groove 10 was small, and no seizure of the top land 9 or any signs thereof were observed.

Embodiment 3 FIG. 8 is a longitudinal sectional view showing yet another embodiment of the piston for internal combustion engines according to the present invention, which is constructed as a piston for a direct injection diesel engine. In the figure, parts that are substantially the same as those shown in Figure tJ1 and Figure 5 are given the same reference numerals.

In this embodiment, the first region 38 defining the edge of the cylinder head side end of the combustion chamber recess 3 is located along the axis 4 at a volume fraction of 35%, although it is not shown in the figure. Alumina length 1t [t(10
The second region 39 around the first region 38 has a volume of 1210% (bulk density 0.33+] /
,
), and the third region 40 around the second region 39 in the radial direction has a volume ratio of 5% (bulk density 0, 16
The third p region 40 is compositely reinforced with alumina short 11 fibers (not shown in the figure) (manufactured by ICI Co., Ltd. Seikin Co., Ltd. [Safil]) which are three-dimensionally randomly oriented at 0/n3). extends to the cylindrical outer peripheral surface of the piston 1,
In the axial direction, it extends from the surface 2a of the head portion 2 to substantially the center of the second land 26. This embodiment is constructed in the same manner as the embodiment shown in FIGS. 1 and 5 in other respects.

A piston having the above-mentioned configuration (diameter 10211 length 105 mm, first region 38 inner diameter 54 mm outer diameter 74 mm)
m, axial length 5.51, inner diameter of second region 39 74
mm, outer diameter 90mm, axial length 11111I111
Third (7) region [40 (7) inner diameter 90n+m, axial length 23+111! l) was formed in the same manner as in Examples 1 and 2 above, and the piston was formed in the same manner as in Examples 1 and 2.
When the engine was assembled into the same diesel engine as that used in the previous example, and an endurance test was conducted at a rotational speed of 3,800 rpm+ and a full load, it was found that the durability lasted for 500 hours, which is longer than in the cases of Examples 1 and 2 described above. 1. Even after a long test, no cracks were found on the edge of the cylinder head side end of the combustion chamber recess 3, and the amount of wear on the top ring groove 10 was small, and there was no seizure or seizure of the top land 9. No signs of this were observed.

Example 4 The first region 38 in Example 3 above has a volume ratio of 25%
A piston identical to the piston of Example 3 was formed, except for the steel which was compositely reinforced with three-dimensionally randomly oriented silicon carbide voice force (average fiber diameter 0.5μ, average fiber length 150μ). Example 3 described above for this piston
A durability test was conducted under the same conditions as in the case of 50
Even after the 0-hour durability test, there were no cracks on the edge of the cylinder head side end of the combustion chamber recess 3, the amount of wear on the top ring groove 10 was small, and there was no seizure or seizure of the top land 9. No signs of this were observed.

Embodiment 5 FIG. 9 is a partially cutaway perspective view showing one embodiment of an internal combustion 41i piston according to the present invention configured as a piston for an indirect injection diesel engine. Furthermore, this ninth
In the figures, parts that are substantially the same as those shown in FIGS. 1 and 5 are designated by the same reference numerals.

In this embodiment, a first region 41 defining the center of the cylinder head side surface of the head portion 2 is formed in a three-dimensional random orientation with a volume ratio of 20%, although it is not shown in the figure. The second region 42 around the first region 41 in the radial direction is Although not shown, short alumina fibers (95 wt% δA120G, 5 wt% SiO2,
The third region 4 around the second region 42 in the radial direction is compositely reinforced with ICI Co., Ltd. [Saphir RFJ].
3 is compositely reinforced with alumina fiber ("Saphir", manufactured by ICI Corporation), which is not shown in the figure, and is three-dimensionally randomly oriented at a volume ratio of 7%. Also, the third area 4
3 extends to the cylindrical outer peripheral surface of the piston 1 in the radial direction, and extends from the surface 2a of the head portion 2 to substantially the center of the recand land 26 in the axial direction.

A piston having the configuration as described above (diameter 92IWII+
1 length 851IIIl, diameter of first region 41 4Qm
m, thickness 5 mm, inner diameter of the second region 42 (Mm, outer diameter 761!1 m, thickness 5 mn+, inner diameter of the third region 7 (3
mm, axial length 15m1Tl) was formed by high-pressure casting as in each of the above-mentioned examples, and the piston thus formed was assembled into a 200Qcc 4-cylinder day-bill engine, and was durable for 300 hours at a rotational speed of 520 orpm. When the test was conducted, it was confirmed that no melting damage or cracks occurred on the surface 2a of the head portion 2 of the piston, and that the amount of wear of the top ring groove 10 was small. Furthermore, no burn-in of Topland 9 or any signs thereof were observed. Furthermore, by compositely reinforcing the head section with reinforcing fibers, the wall thickness of the head section can be made thinner, which makes the piston lighter and allows for better blow-up and higher speed rotation.

Although the present invention has been described above in detail with reference to several embodiments, the present invention is not limited to these embodiments, and various embodiments are possible within the scope of the present invention. This will be clear to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an actual example of a piston for an internal combustion engine according to the present invention configured as a piston for a direct injection diesel engine, and FIG. 2 shows the operating state of the piston for a direct injection diesel engine. An illustration showing the temperature distribution at
FIG. 3 is a perspective view showing a fiber molded body used in manufacturing the embodiment shown in FIG. 1, and FIG. 4 is a cross-sectional view showing the casting process when manufacturing the embodiment shown in FIG. 1. 5 is a longitudinal sectional view showing another embodiment of a piston for an internal combustion engine according to the present invention configured as a piston for a direct injection type diesel engine, and FIG. 6 is a longitudinal sectional view showing an embodiment of the piston shown in FIG. 5. Figure 7 is a partially cutaway diagram of the IIA fiber composition body used in the manufacture of the piston shown in Figure 51. 8 is a longitudinal sectional view showing another embodiment of the piston for an internal combustion engine according to the present invention configured as a piston for a direct injection diesel engine 1, and FIG. 1 is a perspective view, partially cut away, of an embodiment of a piston according to the invention configured as a piston for an engine; FIG. 1...Piston, 2...Head part, 3...Combustion chamber recess. 4... Axis line, 5... Protrusion, 6... First region, 7
... second region, 8 ... third region, 9 ... top land, 10 ... top ring groove, 11 ... second ring groove. 12...Oil ring groove, 13...Bin boss, 14
...Alumina short fiber, 15...First ring, 16
...Second ring, 17...Third ring, 18.
...II fiber molded body, 19... Casting device, 20... Lower mold, 21... Mold cavity, 22... Molten metal of aluminum alloy. 23...Upper mold, 24.25...Knockout bin,
26...Second land, 27...Wire mesh, 28.2
9... Metal plate, 30... Filter, 31... Slurry, 32... Conduit, 33... Axis line, 34... First S*fu, 35... Second Fiber layer, 36... Third fiber layer, 37... Fiber molded body, 38... First region, 39... Second region. 40...Third area, 41...First area, 42.
...Second Area, 43...Third Area Patent Applicant Toyota Motor Corporation Representative Patent Attorney Masatake Akashi 1st Figure 2Figure 3Figure 1 Day 4Figure 5Figure 6Figure 2 Figure 7 Figure 8 Figure 9

Claims (2)

[Claims] (1) The piston for internal combustion engines is made of light metal, and the head part is composite reinforced with reinforcing fibers that have a lower coefficient of thermal expansion than the light metal that composes it, so that the temperature reached during operation of the internal combustion engine is high. 1. A piston for an internal combustion engine made of a light metal, characterized in that the volume fraction of the reinforcement is increased in each part. (2) This is a light metal piston for internal combustion engines, and the head part is compositely reinforced with multiple types of reinforcing fibers that have a lower coefficient of thermal expansion than the light metal that composes it, so that the temperature reached during operation of the internal combustion engine is A light metal piston for an internal combustion engine, characterized in that high-temperature parts are compositely reinforced with Reinforced 41 navy blue, which has an excellent effect of suppressing thermal expansion.