JP2656640B2 - Piston assembly and piston member having predetermined compression height to radius ratio - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates generally to compact piston assemblies for high power internal combustion engines, and more particularly to steel capable of withstanding high pressures and temperatures in a combustion chamber. The present invention relates to a piston assembly having a piston.

(Background technology)

In the last few years, the focus has been on the economics of vehicles, the reduction of emissions and the increase in engine power. This emphasis has also been directed at reducing the size of cars and engines.

At present, engines operating under combustion chamber pressures of up to about 12,410 KPa (1800 psi) have been converted to high power engines, so that higher combustion chamber pressures and temperatures act on the pistons. U.S. Pat. No. 4,581,98 issued to Horst Moebus on April 15, 1986.
The cooling piston disclosed in No. 3 seeks to provide a piston that can withstand such increased pressure and temperature. However, the upper and lower parts of the piston of this patent are joined by welding. This is a costly method and is preferably avoided.

A more preferred mechanism capable of withstanding the high temperatures and pressures of the combustion chamber is U.S. Pat. No. 4,056,04 issued to Kenneth R. Kamman on Nov. 1, 1977.
There is No. 4. This patent shows a complex piston assembly connecting two parts. However, experiments have shown that pistons cast with current technology have high strength, safety factors, and the long life required of current high combustion chamber pressure engines without undue quality control. Absent. Extensive testing shows that the practical level of casting technology is about 13,790 KPa
(2000 psi) or higher. More specifically, the experiment failed early because the majority of the upper portion of the cast steel piston was extremely porous. On the other hand, a small number of cast steel pistons were manufactured as relatively low porosity, so they also passed rigorous testing. Various tests have also been performed to minimize the level of porosity of the cast part, but from a practical point of view the level of porosity remains high. Therefore, it has been found that it is necessary to inspect each casting piston with X-rays for quality control, which is expensive.

Second, the benefit of the cast piston's grain flow is negligible, with very little if any increase in piston strength. Due to the increased pressure and temperature of the combustion chamber, this type of piston does not damage the engine or cause the vehicle to stop.

Rutger Barchem on May 5, 1987
U.S. Pat. No. 4,662,047 to Berchem discloses a one-piece piston. The piston is manufactured by bending a casting blank by pressing with a die to form an annular cylindrical collar. However, the patent does not disclose or suggest reducing the ratio of compression height to piston diameter, adaptability to coupling ratios, and high combustion chamber pressure engines.

Emil Lipberger (Em) dated November 10, 1987
U.S. Pat. No. 4,704,950 to Il Ripberger et al. discloses a single-piece, extremely lightweight, low-friction, uncoupled piston having a compression height to piston diameter ratio of 0.20 to 0.35. is there. However,
The range of ratios indicated by the U.S. patent is unsuitable for use in high-combustion-chamber pressure engines due to poor structural coupling. For example, according to analytical data, the portion supporting the ring cannot withstand the load and may be destroyed.

In addition to taking into account the degree of porosity, the shape and strength of each part of the articulated piston must also be taken into account as they increase the resistance to high compressive loads and thermal stresses and reduce costs. . Take, for example, Societ, an automotive engineer written by MD Roehle.
y of Automotive Engineers, Inc.'s 770031 “Piston for High-Power Diesel Engines” (issued February 28, 1977) shows a number of experiments performed worldwide on each component. . The book also provides a number of considerations for minimizing cracks in lightweight alloy and aluminum pistons, primarily caused by thermal stress. One of the considerations is to increase the length from the upper edge of the wrist pin bore to the lower side of the crown to reduce the stress at the pin bore portion. However, in this case, the so-called critical height CH (vertical distance between the top surface of the piston and the center axis of the wrist pin) of the piston is set to reduce the size of the engine to make it compact and reduce the cost. Making it smaller becomes more important.

Thus, what is presently needed is a piston assembly for a high power engine and a piston for use therein, which is above about 13,790 KPa (2000 psi), preferably about 15,170 KPa (2000 psi).
A piston assembly and piston that can operate continuously and efficiently at combustion chamber pressures in the range of KPa (2200 psi). Furthermore, the piston must have a complex shape and be relatively easy to manufacture. Moreover, the upper part of the piston is preferably as smooth and symmetrical as possible, which increases the stress and / or
Alternatively, thermal distortion can be avoided. Furthermore, the compression height CH of the piston is maximized to maximize compactness.
Preferably, it is as small as possible.

The present invention is directed to overcoming one or more of the problems set forth above.

[Disclosure of the Invention]

The present invention provides a reciprocating articulated piston assembly for use in a high combustion chamber pressure engine, the piston assembly including a steel piston member having an upper portion and a lower portion, the upper portion being substantially similar to the piston assembly. A cylindrical shape, a predetermined maximum diameter "D", a top surface, a tubular wall continuous from the top surface, an annular wall surface facing outward, and a cooling annular recess facing downward. Is provided. Also, the lower portion has a pair of downwardly extending pin bosses that are continuous with the aforementioned outwardly directed annular wall surface, and each of the pin bosses forms a wrist pin receiving bore aligned on the same axis. I have.
Compressed height "CH" as the vertical distance between the same axis and the top surface
When the ratio between the compression height “CH” and the maximum diameter “D” is 6
Is a predetermined value in the range of 0% to 45%, and as a whole,
Alternatively, or slightly, a skirt having a pair of wrist pin receiving bores having an elliptical shape having a maximum diameter and a minimum diameter is provided around the lower portion, with the wrist pin receiving bores facing in the direction of the minimum diameter and the same axis. It is arranged to be aligned. A wrist pin is slidably disposed in the lower portion wrist pin receiving bore and the wrist pin receiving bore of the skirt. Further, the skirt has a top surface that is not in contact with, but very close to, the lower end surface of the upper portion, the skirt has a generally annular recess located on the top surface, and a cooling fluid on the skirt. And a pair of passages that communicate with each other.

The pistons provided by the present invention provide a simple, low cost, and lightweight solution to withstand increased combustion pressure and temperature in current and future engines.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an engine piston assembly according to the present invention, FIG. 2 is a partial sectional view of the piston assembly taken along the line II-II of FIG. 1, FIG. FIG. 4 is a partially enlarged view showing a top surface portion of the piston shown in FIG. 2, FIG. 4 is a plan view of the piston as viewed from the line IV-IV in FIG. 2, FIG. 5 is VV in FIG. FIG. 6 is a plan view of the piston skirt when cut along a line, and FIG. 6 is a partially enlarged sectional view of a top surface portion of the piston shown in FIG. 1 and FIG. 7 shows a flow streak of a cast piston having only a cooling recess, and FIG. 7 is a partially enlarged sectional view of a top surface portion of the piston shown in FIG. 1 and FIG. Figure 4 shows the flow streak of a casting piston with a cooling recess provided.

〔Example〕

FIG. 1 and FIG. 2 show a multi-cylinder internal combustion engine 10. Internal combustion engine 10 includes a bottom block 12, a top block or spacer member 14, and a cylinder head.
It has 16 and. The cylinder head 16 is rigidly connected in a conventional manner by a plurality of fasteners or bolts 18 passing through the cylinder head 16 and the top block 14 and being screwed to the bottom block 12. The cylinder liner 48, supported in the middle, has an upper portion 52 located on the top block 14, and a cooling fluid passage is formed around the cylinder liner 48. The internal combustion engine 10 may be of a conventional type.

The internal combustion engine 10 further includes a cooling oil firing nozzle 74. An oil firing nozzle 74 is rigidly connected to the bottom block 12 and is operatively connected to a pressurized oil supply (not shown) for supplying cooling oil and the like to the articulated piston assembly 76. .

The piston assembly of the internal combustion engine 10 is an upper steel piston member
An upper piston member 78 and a lower piston skirt 80 are swingably mounted on a common wrist pin 82 having a central axis 84. Wrist pin 82 is also made of steel and has an outer cylindrical surface 86 and a cylindrical bore 88 extending therethrough. The cylindrical bore 88 is provided for weight reduction. The conical connecting rod 90 has an upper eye end 92, and a steel lined bronze sleeve bearing 94 inside the upper eye end 92 is coupled to a wrist pin 82, Driven by 82.

As shown in FIG. 2, the upper steel piston member 78 has a generally cylindrical upper portion 96 and has a predetermined maximum diameter D. Upper portion 96 has a top surface 98 and a crown surface 100. Top surface 98 is flat and lies in a plane perpendicular to central axis 66. Crown surface 100 is, in this embodiment, a rotating surface that is fully machined about central axis 66. Crown surface 100 is located in the center,
It has a top portion 102 located below the top surface 98, a substantially cylindrical land portion 104 radially outward, and an annular trough 106 smoothly connecting the top portion 102 and the land portion 104. I have. Combination of the top 102, the annular trough 106, and the land 104 greatly improves combustion efficiency.

As best shown in FIG. 3, the upper steel piston member 78 includes a tubular wall 108 extending from the outer edge of the top surface 98. This tubular wall 108 has a top land 100 formed around it, a top ring groove 112 having a wedge-shaped cross section, an upper middle land 114, a middle ring groove 116 having a rectangular cross section, a lower middle land 118, and a bottom section having a rectangular cross section. Ring groove 120, lower end surface
It has a bottom land 122 ending in 124. An annular wall surface 126 facing radially inward also forms part of the tubular wall 108 and extends upward from the lower end surface 124. Upper part 9
6 further comprises an annular wall 128 facing radially outwards
And a connecting portion 130 facing downward. The connecting portion 130 connects the wall surface 126 and the wall surface 128 to form an annular cooling recess 132 having an accurate cross-sectional shape. In practice, the wall 128 has an upper conical portion 134,
It is formed from a cylindrical portion 136 that continues below. The upper conical portion 134 has an inclination angle A with respect to the central axis 66, which is about 12 ° as shown in FIG. On the other hand, the wall surface 126 is conical and has an inclination angle B of about 1.7 °. The annular cooling recess 132 may be forged into any shape. For example, a shallow concave portion may be used as shown in FIG. 6, or a deep concave portion may be used as shown in FIG. Further, as shown in FIGS. 6 and 7, the Glen flow obtained by forging is as shown by imaginary lines.

The steel piston member 78 further comprises a lower portion 158. Lower portion 158 includes a pair of dependent pin bosses 160,
The slave pin boss 160 is coupled to the wall 128 of the upper portion 96 and to the downwardly facing recessed pocket 162 formed by the upper portion 96. The recess pocket 162 is substantially uniformly spaced from the top 102 of the crown surface 100 to form a crown 164 of approximately uniform thickness of about 4 mm or 5 mm, as shown in FIGS. . In addition, due to these shapes, a relatively thin, generally conical-shaped web 166 is formed between the wall surface 128 and the crown surface annular trough 106 and the adjacent land portion 104. Web 166 has a minimum thickness W of about 4-7 mm.
Each of the pin bosses 160 has a bore 16 penetrating the pin boss 160.
8 are formed, and the bores 168 are each fitted with a bronze bearing sleeve 170 lined with steel. These bearing sleeves 170 are axially aligned and pivotally receive the wrist pins 82.

The piston skirt 80 has a top surface 172 that is not in contact with, but is in close proximity to, the lower end surface 124 of the upper portion 96 of the piston member 78, and has an upwardly-facing annular surface facing the top surface 172. An oil trough 174 is formed. A slightly elliptical outer peripheral surface 176 extends from the periphery of the top surface 172.
Piston skirt 80 has maximum diameter 177 and minimum diameter 177b
have. A pair of wrist pin receiving bores 178 are formed so as to extend through the piston skirt 80, and the wrist pin receiving bores 178 are axially aligned with the minimum diameter 177b. Further, a snap ring receiving groove 180 is formed in each bore 178. The piston skirt 80 is thus pivotally attached to a wrist pin 82 provided so as to be slidably inserted into both wrist pin receiving bores 178. The wrist pin 82 is prevented from moving beyond the ring 182 in the direction of the axis 84 by a pair of split retaining rings 182 disposed in the snap ring receiving grooves 180, respectively.

A pair of bosses 184 facing in the axial direction are provided in the piston skirt 80, and a pair of lubricant passages 186 extending through the boss 184 in the axial direction are provided. As shown in FIG. 5, the lubricant passages 186 are diagonally opposed to each other, so that the piston skirt 80 can be attached to the wrist pin 82 in two positions, so that at least one lubricant Aisle 186
Are axially aligned with the oil firing nozzle 74. The piston skirt 80 is provided with a semi-cylindrical recess 188 facing downward in a diagonal direction and opening downward at the bottom thereof. And a clearance is created between them.

[Industrial applicability]

The steel piston member 78 according to the present invention is used for the articulated piston assembly 76. The articulated piston assembly is used in a high combustion chamber pressure engine 10 where the combustion chamber pressure is 15,170 KPa (2200 psi). This articulated piston assembly
The power can be increased by the 76, and the size of the engine can be reduced. As shown in FIG. 1, an engine in which an articulated piston assembly 76 is used.
10 has an intermediate supported cylinder liner 48 and has two cylinder blocks 12,14.
The liquid coolant flows only inside the top block 14 of the two blocks and provides an excellent cooling or heat dissipation effect to the piston assembly.

In operation, articulated piston assembly 76 moves downward to bottom dead center. At this bottom dead center, the oil firing nozzle 74 is aligned with the skirt passage 186
Fire the lubricant oil through. The oil continues to spray upward and contacts the surface of the cooling recess 132 of the piston member 78 and splashes around the surface in the opposite direction. Most of the lubricant oil accumulates in the skirt trough 174 as the piston assembly 76 reciprocates and then is evenly distributed within the piston member.

Referring to FIG. 3, the top of the cooling recess 132 is directly below the top surface 98 of the piston member and has a vertical distance E from the top surface 98.
Is about 5 mm. In conclusion, the ratio of vertical distance E to piston diameter D should be less than or equal to about 0.10, and is preferably between about 0.04 and 0.06. In one embodiment, the diameter D was 124 mm, the vertical distance E was 5.5 mm, and the ratio of piston diameter to vertical distance was about 0.044.

In the same embodiment, the vertical distance CH between the top surface 98 and the wrist pin central axis 84 was 70 mm. Therefore, the ratio of the vertical distance CH to the diameter D was about 0.56. Therefore,
From this it can be concluded that the ratio of the vertical distance CH to the diameter D should be less than about 0.60, and preferably about 0.60.
It is in the range of 0.60 to 0.45.

In addition to the numerical limitations described above, the articulated piston assembly 76 is preferably manufactured in a particular manner and using certain materials. For example, the upper steel piston member 78
Is preferably forged from an alloy steel which is basically a 4140 improved steel.

Similarly, the lower aluminum piston skirt 80 is preferably forged from a modified aluminum, which is basically a SAE321-T6 modified aluminum.

The alloy steels described above are particularly suitable for class II forging,
It is possible to provide an austenite particle size of 5 or finer that is desired to withstand the high combustion pressures in high combustion chamber pressure engines. in this way,
As shown in FIGS. 6 and 7, primarily due to the Glen flow and web size in the web 166, it is possible to resist or transfer pressure or other forces to today's high combustion chamber pressure engines. It can achieve the high strength, safety factor, and long life that are desired.

The forged aluminum alloys described above have high hardness, excellent wear resistance, and a relatively low coefficient of thermal expansion.

Continuation of the front page (56) References JP-A-59-58137 (JP, A) JP-A-61-58956 (JP, A) US Patent 4180027 (US, A)

Claims (8)

(57) [Claims] 1. A steel piston member (78) having an upper portion (96) and a lower portion (158), said upper portion (96) being substantially cylindrical and having a predetermined maximum diameter "D"; A top surface (98), a tubular wall (108) continuous from the top surface (98), and an annular wall surface (1
28) and a downwardly directed cooling annular recess (132), wherein the lower portion (158) extends downwardly in a pair continuous with the outwardly directed annular wall surface (128). A pin boss (160) is provided, each of which forms a wrist pin receiving bore (168) arranged on the same axis (84), and the same axis (84) and the top surface (98). When the compression height “CH” is defined as the vertical distance between the compression height “CH” and the maximum diameter “D” is a predetermined value within the range of 60% to 45%. , As a whole or slightly oval with a maximum diameter and a minimum diameter, a pair of wrist pin receiving bores (17
A skirt (80) with 8) is arranged around the lower part (158) such that the wrist pin receiving bore (178) is aligned with the same axis (84) in the direction of the smallest diameter. A wrist pin (82) is slidably disposed in the pair of wrist pin receiving bores (178) of the skirt (80) and the wrist pin receiving bore (168) of the lower portion (158). The skirt (80) is provided at the lower end surface (12) of the upper portion (96).
4), but not very close to the top surface (17
2) the skirt (80) has a substantially annular recess (174) located on the top surface (172), and a pair of passages (186) for communicating a cooling fluid to the skirt (80). A reciprocating articulated piston assembly (76) for use in a high combustion chamber pressure engine (10), comprising: 2. The upper part (96) and the lower part (158).
The connecting piston assembly (7) according to claim (1), wherein the piston is integrally formed by forging with steel.
6). 3. The articulated piston assembly (76) according to claim 1, wherein said annular cooling recess (132) is located below said top surface (98). The upper part (96) has a crank surface (10).
The articulated piston assembly (76) according to claim (3), characterized in that it comprises (0). 5. The crown surface (100) has a centrally located apex (102) and an annular trough (106) continuous with the crown surface (100). The articulated piston assembly (76) according to claim (4). 6. The recess (174) stores the cooling fluid and splashes the cooling fluid against the recess (174) while the piston assembly (76) is reciprocating. An articulated piston assembly (76) according to claim 1, characterized in that: 7. The device according to claim 6, wherein each of said pair of wrist pin receiving bores has an inner surface, and an annular ring groove is formed in each inner surface. The articulated piston assembly (76) as described. 8. The articulated piston according to claim 7, wherein a snap ring (182) for holding the wrist pin (82) is arranged in each of the grooves (180). Assembly (76).