JPH0510527B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a connecting rod for an internal combustion engine, and more particularly to a connecting rod made of a light metal composite reinforced with reinforcing fibers.

Prior Art Connecting rods for internal combustion engines are generally
Consisting of a connecting rod main body and a connecting rod cap, each having a semi-cylindrical recess defining a large end hole for receiving a crankshaft and fastened to each other with bolts,
It is made of steel such as carbon steel. Connecting rods made of such steel are heavy and it is difficult to reduce the weight of internal combustion engines, so connecting rods are made of light metals such as aluminum alloys and Attempts have been made to provide composite reinforcement using reinforcing fibers. In conventional light metal connecting rods that are compositely reinforced with such reinforcing fibers, the parts around the bolt insertion holes formed in the connecting rod body and the connecting rod cap are reinforced with reinforcing fibers. The bolts are either not reinforced or reinforced with reinforcing fibers oriented in one direction along the axis of the bolt insertion hole.

However, in this case, because the coefficient of thermal expansion of the light metal that makes up the connecting rod is greater than that of the steel that makes up the bolt, the area around the bolt insertion hole is damaged during operation of the internal combustion engine. There is a problem in that the thermal expansion is greater than that of the bolt, and as a result, the axial force of the bolt increases, causing creep deformation of the bearing surfaces of the bolt and nut. Furthermore, if the tightening load of the bolt is reduced to avoid such creep deformation, the tensile and compressive loads acting on the connecting rod during operation of the internal combustion engine will cause the large end hole of the connecting rod to become round. loss of strength,
A problem arises in that friction loss between the large end hole of the connecting rod and the crankshaft increases.

In addition, in the above case, the bolt thermally expands more than the area around the bolt insertion hole, so the tightening load on the bolt decreases while the internal combustion engine is running, and this causes the connecting bolt to tighten. Problems arise in that the state of connection between the crankshaft and the crankshaft is impaired, causing looseness, and as a result, friction loss between them increases. In addition, in the above case, the amount of reinforcing fibers filled in the area around the bolt insertion hole is reduced to make the thermal expansion coefficient of that area substantially the same as that of the steel that makes up the bolt. Although it is theoretically possible to do so, in reality it is extremely difficult to uniformly orient a small amount of reinforcing fibers in one direction around the bolt insertion hole and along its axis.

Purpose of the Invention In view of the above-mentioned problems in conventional light metal connecting rods compositely reinforced with reinforcing fibers, the present invention has been made to solve the problem that the thermal expansion coefficients of the bolt and the area around the bolt insertion hole are mutually This is an improved light metal that reliably avoids the creep deformation of the bolt and nut seating surfaces and the decrease in bolt tightening load caused by large differences, and allows internal combustion engines to operate smoothly over long periods of time. The purpose of this invention is to provide connecting rods for internal combustion engines.

SUMMARY OF THE INVENTION According to the present invention, a connecting rod body is provided which has semi-cylindrical recesses that cooperate with each other to define a large end hole for receiving a crankshaft, and which are fastened to each other with bolts. and a connecting rod cap for a light metal internal combustion engine, wherein a portion of each of the main body and the cap surrounding a bolt insertion hole for receiving the bolt extends around the axis of the bolt insertion hole. Compositely reinforced with long fibers that are spirally oriented and extend substantially continuously between both ends of the bolt insertion hole, and the coefficient of thermal expansion in the direction along the axis of the portion around the bolt insertion hole is This is achieved by a connecting rod for an internal combustion engine made of a light metal, characterized in that the coefficient of thermal expansion is substantially the same as the coefficient of thermal expansion of the bolt.

Effects and Effects of the Invention According to the present invention, the portion around the bolt insertion hole is oriented in a spiral around the axis of the bolt insertion hole and extends substantially continuously between both ends of the bolt insertion hole. Compositely reinforced with long fibers, the thermal expansion coefficient of the area around the bolt insertion hole in the direction along the axis is substantially the same as the thermal expansion coefficient of the bolt, so the heat of the area around the bolt insertion hole and the bolt is reduced. It is possible to reliably prevent problems such as creep deformation of the bearing surfaces of bolts and nuts or reduction of bolt tightening load due to large differences in expansion rates.

Further, according to the present invention, the coefficient of thermal expansion of the area around the bolt insertion hole is made substantially the same as the coefficient of thermal expansion of the bolt without reducing the amount of reinforcing fibers. Insufficient strength can be reliably avoided.

The connecting rod according to the present invention may be made of aluminum, magnesium, or an alloy containing these as main components, and the long fibers that compositely reinforce the area around the bolt insertion hole are compatible with the light metals mentioned above. The fibers may be alumina fibers, carbon fibers, alumina-silica fibers, silicon carbide fibers, etc., which have excellent properties and strength-improving effects. In addition, the volume percentage of these long fibers may be selected in the range of 20 to 70% depending on the metal and the type of long fibers constituting the connecting rod, and they are oriented spirally around the axis of the bolt insertion hole. The pitch angle θ of the long fibers is determined based on the light metal, the type of long fibers, and the type of long fibers so that the coefficient of thermal expansion in the direction along the axis around the bolt insertion hole is substantially equal to the coefficient of thermal expansion of the bolt. It is preferable to select the range of 0<θ<30° depending on the fiber diameter, volume fraction, etc.

Embodiment FIG. 1 is a partially cutaway front view showing one embodiment of the connecting rod according to the present invention, and FIGS. 2 and 3 are lines - and - of FIG. 1, respectively.
FIG.

In these figures, 1 and 2 denote connecting rods having semi-cylindrical recesses 4 and 5 that cooperate with each other to define a large end hole 3 for receiving a crankshaft (not shown in the figures). The main body and connecting rod cap are shown. The connecting rod main body 1 and the connecting rod cap 2 are fastened to each other by bolts 6, 7 and nuts 8, 9 with their mating surfaces 1a and 2a in contact with each other, and are thus fastened. Then, the large end portion 10 is defined. Bolts 6 and 7 are mounted on both sides of the recess 4 of the connecting rod body 1 so that their heads are connected to the seat surface 11.
Bolt insertion holes 13 and 14 are provided on both sides of the recess 5 of the connecting rod 2 to receive the bolts 6 and 7, respectively. It is provided at a position aligned with holes 13 and 14. The connecting rod cap 2 is also provided with seating surfaces 17 and 18 for receiving nuts 8 and 9 which are screwed onto the bolts 6 and 7.

A small end hole 20 for receiving a piston pin (not shown) is provided at the end of the connecting rod body 1 opposite to the large end 10, that is, the small end 19. 10 and the small end portion 19 are integrally connected to each other by an arm portion 21.

The connecting rod shown in the figure is made of aluminum alloy (JIS standard AC7A), and the small end 19, the arm part 21, and a part of the large end 10 are made of long fibers oriented in a hairpin shape. a pair of second reinforcing fiber bundles 23 and 24 made of long fibers oriented circularly around the large end hole 3 on both sides of the first reinforcing fiber bundle 22; Composite reinforcement is provided on both sides of the reinforcing fiber bundle 22 by a pair of third reinforcing fiber bundles 25 and 26 made of long fibers oriented circularly around the small end hole 20. The long fibers constituting the reinforcing fiber bundles 22 to 26 are alumina fibers (Fiber FP (registered trademark) manufactured by DuPont).

Furthermore, the parts around the bolt insertion holes 13 and 15 and the bolt insertion holes 14 and 16 are covered with a second reinforcing fiber bundle 23.
and 24, respectively, the axis 2 of the bolt insertion hole
Long fibers 29 and 30 (alumina fibers,
Compositely reinforced with DuPont fiber FP (registered trademark). In this case, the long fibers 29 and 30 are oriented in a spiral manner around the bolt insertion hole.
As shown in FIG. 4, the seat surfaces 11, 17
(The portions near 12 and 18 may be oriented at a small pitch angle close to zero, and the portion between them may be oriented at a relatively large pitch angle.

The connecting rod constructed as described above was manufactured as follows.

First, 105,000 alumina fibers each having a length of 245 mm were bundled to form a first reinforcing fiber bundle 22 as shown in FIG. 5. In addition, by winding alumina fibers around a rod (not shown), a second reinforcing fiber bundle 23 having an outer diameter of 71 mm, an inner diameter of 43 mm, and a height of 5 mm is formed as shown in FIGS. 6 and 7.
(and 24), outer diameter 34mm, inner diameter 18mm, height 5mm
An annular third reinforcing fiber bundle 25 (and 26) was formed.

Furthermore, although not shown in the figure, the diameter is 10 mm and the length is 55 mm.
Alumina fiber yarn (number of fibers
A cylindrical body 31 having an outer diameter of 18 mm, an inner diameter of 10 mm, and a length of 50 mm was formed by winding 120 pieces (120 pieces) 1200 times at a pitch angle θ=2°. Next, stainless steel (JIS standard
It is formed by pressing SUS304) plates (plate thickness 1.5 mm), and when assembled so that they are in contact with each other at the mating surfaces 33 as shown in Fig. 9, the connectors to be manufactured inside the A depression 3 defining a space having a shape substantially corresponding to the bearing rod.
A container consisting of two halves 36 each having a groove 35 defining a passage communicating between the space defined by the depression 34 and the outside of the space was prepared. The parts defining the large and small ends of the recess 34 of one half 36 of the container are each made of stainless steel (JIS standard SUS304) with an outer diameter of 43 mm and a length of 26 mm.
mm, plate thickness 1mm pipe 37 and outer diameter 18mm, length 26
A pipe 38 with a plate thickness of 1 mm and a plate thickness of 1 mm was fixed by welding.

Next, as shown in FIG. 10, second and third reinforcing fiber bundles 23 and 25, first reinforcing fiber bundle 22, two cylindrical bodies 31, and second reinforcing fiber bundles 23 and 25 are placed in recess 34 of container half 36. and third reinforcing fiber bundles 24 and 2
6, the mating surfaces 33 of the halves 36 are brought into close contact with each other, and the outer peripheral edges of the halves 36 are welded.
A connecting rod preform was formed in which the first to third reinforcing fiber bundles and the cylindrical body were placed inside the container formed by the two halves 36.

The preform formed as described above was then preheated to 800° C. in a heating furnace, and then the preform 39 was placed in a mold 40 for high pressure casting as shown in FIG. Next, a molten metal 41 of aluminum alloy (JIS standard AC7A) at 750°C is quickly poured into the mold 40, and the molten metal is pressurized with a surface pressure of 1500 kg/cm ² by a plunger 42 until the molten metal 41 is completely absorbed. It was held until it solidified. Molten metal 41
After the solidified body is completely solidified, the solidified body is removed from the mold 40 using the knockout pin 43, the preform 39 is cut out from the solidified body, and the container is disassembled by cutting the peripheral edge of the preform. The rough material of the connecting rod formed in the process was taken out. Next, by performing machining such as grinding on this connecting rod rough material, the total length is 175 mm, the diameter of the large end hole 3 is 45 mm, the diameter of the small end hole 20 is 18 mm, and the center of the large end hole 3 and the small end hole 20 are formed. As shown in FIGS. 1 to 3, the distance from the center of Like 6
Six connecting rods for a 2000cc gasoline engine were formed.

The connecting rod body and cap formed as described above are tightened to the bolt tightening torque.
By tightening at 450kgfcm, it can be installed in a 6-cylinder gasoline engine with a total displacement of 2000cc, and can be used at full load.
It was subjected to a continuous durability test for 200 hours at a rotation speed of 5800 rpm. After the test, the gasoline engine was disassembled and the connecting rod was examined, and no harmful scratches, deformation, or dents were found in the area around the bolt insertion hole of the connecting rod or on the seat surface. Attempt to tighten the bolts with torque
Continuous durability tests were carried out under the same conditions as the above-mentioned experimental conditions, increasing the capacity to 550 kgfcm, and in this case as well, no deformation or cracks occurred at all in the area around the bolt insertion hole and on the seat surface. Furthermore, when we measured the coefficient of thermal expansion in the direction along the axis of the area around the bolt insertion hole, the coefficient of thermal expansion of this area was 16.4×10 ^-6
This value was found to be substantially equal to the coefficient of thermal expansion (16×10 ⁻⁶ ) of the steel constituting the bolt.

For the purpose of comparison, as shown in the left half of Fig. 12, a specimen was formed under the same conditions as the above-mentioned example except that the area around the bolt insertion hole was not filled with reinforcing fibers. As shown in the connecting rod as Comparative Example 1 and the right half of FIG. A connecting rod as Comparative Example 2 formed under the same conditions as the above-mentioned Example except that it was filled with alumina fiber 44 (Fiber FP (registered trademark) manufactured by DuPont, 224,000 fibers). was formed.

When these connecting rods were tightened with a bolt tightening torque of 450 kgfcm, the bearing surfaces of the bolts and nuts of the connecting rod of Comparative Example 1 sank 1.8 mm, and the connecting rod body and connecting rod It was recognized that it was not possible to enter into a proper contract with Rodcap. In addition, the six connecting rods of Comparative Example 1 and Comparative Example 2 were assembled into the same gasoline engine as that used in the continuous durability test in the above-mentioned example (the tightening torque of each bolt was 350kgfcm and 450kgfcm), and the durability test was conducted under the same conditions as the durability test described above.

As a result, in the connecting rod of Comparative Example 1, a decrease in engine output was observed 10 minutes after the start of the test. In addition, 100 hours after the start of the test, the gasoline engine was stopped and the connecting rod was inspected, and it was found that there was abnormal uneven wear on the bearing seat interposed between the big end and the crankshaft. It was also observed that minute cracks extending along the axis of the bolt insertion hole had occurred on the bolt seating surface and the nut seating surface. Further, in the connecting rod of Comparative Example 2, a decrease in engine output was observed 30 minutes after the start of the test (oil temperature at that time was 140°C). However, even after the test, there were no defects such as cracks in the area around the bolt insertion hole or in the bearing surfaces of the bolt and nut. Furthermore, the above-mentioned Comparative Example 1 and Comparative Example 2
When we measured the thermal expansion coefficients of the parts around the bolt insertion holes of the connecting rod, the respective thermal expansion coefficients were 23 × 10 ^-6 and 8 × 10 ^-6 , which is the same as the thermal expansion of the steel that makes up the bolts. This value was significantly different from the ratio of 16×10 ^-6 .

Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to such embodiments, and it is understood that various embodiments are possible within the scope of the present invention. It will be clear to those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view of one embodiment of the connecting rod according to the present invention, and FIGS. 2 and 3 are lines ``-'' and ``-'' in FIG.
FIG. 4 is a partial sectional view showing the essential parts of another embodiment of the connecting rod according to the present invention, and FIGS. 5 to 7 show the first to third reinforcing fiber bundles, respectively. FIG. 8 is a perspective view showing a cylindrical body formed by spirally oriented long fibers, and FIG. 9 is a perspective view showing the reinforcing fiber bundles shown in FIGS. FIG. 10 is a perspective view showing a half of a container housing the cylinder shown in FIG. 10, and FIG. FIG. 11 is an exploded perspective view showing a preform of a connecting rod made up of the container half shown in FIG. 11; FIG. 11 is a sectional view showing a casting process performed using the preform shown in FIG. The figure is a partially cutaway front view of two conventional connecting rods as comparative examples. 1...Connecting rod body, 2...Connecting rod cap, 3...Big end hole, 4,
5... Recess, 6, 7... Bolt, 8, 9... Nut, 10... Big end, 11, 12... Seat surface, 13
~16... Bolt insertion hole, 17, 18... Seat surface,
19... Small end portion, 20... Small end hole, 21... Arm portion, 22... First reinforcing fiber bundle, 23, 24...
...Second reinforcing fiber bundle, 25, 26... Third reinforcing fiber bundle, 27, 28... Axis line, 29, 30... Long fiber, 31... Cylindrical body, 33... Matching surface, 34...
... Depression, 35 ... Groove, 36 ... Container, 37, 38
... Pipe, 39 ... Preform, 40 ... Mold, 41 ... Molten aluminum alloy, 42 ...
Plunger, 43... Knockout pin, 44...
...Alumina fiber.

Claims (1)

[Claims] 1. A light metal internal combustion engine consisting of a connecting rod body and a connecting rod cap, each having a semi-cylindrical recess defining a large end hole for receiving a crankshaft, which cooperate with each other, and are fastened to each other with bolts. In the engine connecting rod, a portion of each of the main body and the cap surrounding a bolt insertion hole for receiving the bolt is oriented spirally around an axis of the bolt insertion hole, and substantially extends through the bolt insertion hole. Composite reinforcement is provided with long fibers extending continuously between both ends of the hole, and the coefficient of thermal expansion of the portion around the bolt insertion hole in the direction along the axis is substantially the same as the coefficient of thermal expansion of the bolt. A connecting rod for an internal combustion engine made of light metal, characterized by the following features: