Information
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Patent Grant
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6371062
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Patent Number
6,371,062
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Date Filed
Wednesday, October 18, 200023 years ago
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Date Issued
Tuesday, April 16, 200222 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
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CPC
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US Classifications
Field of Search
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International Classifications
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Abstract
A variable length connecting rod assembly for imparting a variable compression ratio to an internal combustion engine. The assembly contains a first part (22; 72), a second part (20; 74), and a third part (34; 70) assembled together to form the large end of the connecting rod assembly and provide a variable length for the connecting rod assembly. The first part is a semi-circular cap. One (20; 74) of the second and third parts is fastened tight to the first part (22; 72). Guides (36, 38, 48; 88, 90, 92) disposed at opposite sides of the large end operatively relate the other (34; 70) of the second and third parts and the fastened parts to provide for relative sliding motion between the other of the second and third parts and the fastened parts over a limited adjustment range to change the length of the connecting rod assembly.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to reciprocating piston type internal combustion (I.C.) engines for motor vehicles. More specifically it relates to I.C. engines having variable compression ratio connecting rods.
2. Background Information
A gasoline engine whose compression ratio remains invariant as operating conditions change is said to be knock-limited. This means that the compression ratio built into the engine design must be selected to avoid objectionable engine knock that would otherwise occur during certain conditions of engine operation if the compression ratio were larger. However, those conditions that give rise to engine knocking in a motor vehicle typically prevail for only limited times as the vehicle is being driven. At other times, the engine could operate with better efficiency, and still without knocking, if the compression ratio could be made higher, but unfortunately the engine is incapable of achieving more efficient operation during those times because its compression ratio cannot change.
Certain technologies relating to reciprocating piston I.C. engines having variable compression ratio pistons and connecting rods are disclosed in various patents, including U.S. Pat. Nos. 1,875,180; 2,376,214; 4,510,895; 4,687,348; 4,979,427; 5,562,068; and 5,755,192. Various reasons for employing such technologies in I.C. engines have been advanced in those documents. One reason is to improve efficiency by enabling an engine that is relatively more lightly loaded to run at a compression ratio that is higher than a compression ratio at which the engine operates when running relatively more heavily loaded.
The compression ratio of an engine can be varied by varying the overall effective length of a connecting rod and piston. Change in overall effective length may be accomplished in either the connecting rod, or the piston, or in both. The foregoing patents describe various mechanisms for varying overall effective length.
U.S. Pat. No. 5,562,068 discloses a variable compression ratio connecting rod where adjustment of effective length takes place at the large end. Adjustment is performed via an eccentric ring that is generally coincident with a crank pin, but can be selectively locked to the crank pin and to the large end of the rod. When locked to the crank pin, the eccentric ring assumes a position that causes the rod to have a longer effective length and hence a higher compression ratio. When locked to the rod, the eccentric ring assumes a position that causes the rod to have a shorter effective length and hence a lower compression ratio.
SUMMARY OF THE INVENTION
The present invention relates to further improvements in variable length connecting rods of reciprocating piston I.C. engines for varying engine compression ratios as engine operating conditions change. In particular the invention contemplates constructions for effecting length change at the large end of a connecting rod so that the incorporation of variable compression ratio by length change does not adversely contribute to the reciprocating mass of an engine in a way that might otherwise create unacceptable imbalance.
A general aspect of the invention relates to a variable length connecting rod assembly for imparting a variable compression ratio to an internal combustion engine. The assembly contains a first part, a second part, and a third part assembled together to form the large end of the connecting rod assembly and provide a variable length for the connecting rod assembly. The first part is a semi-circular cap. One of the second and third parts is fastened tight to the first part. Guides disposed at opposite sides of the large end operatively relate the other of the second and third parts and the fastened parts to provide for relative sliding motion between the other of the second and third parts and the fastened parts over a limited adjustment range to change the length of the connecting rod assembly.
Further aspects will be seen in various features of two presently preferred embodiments of the invention that will be described in detail.
BRIEF DESCRIPTION OF THE DRAWINGS
The drawings that will now be briefly described are incorporated herein to illustrate a preferred embodiment of the invention and a best mode presently contemplated for carrying out the invention.
FIG. 1
is an exploded perspective view of a connecting rod constituting a first embodiment.
FIG. 2
is a non-exploded view of
FIG. 1
, looking along a main axis of an engine.
FIG. 3
is an exploded perspective view of a connecting rod constituting a second embodiment.
FIG. 4
is a non-exploded view of
FIG. 3
looking along a main axis of an engine.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
FIGS. 1 and 2
show a connecting rod
12
of a first piston/connecting rod embodiment
10
for endowing an engine with a variable compression ratio. Connecting rod
12
comprises a large end
14
for journaling on a crank pin
15
of a crankshaft and a small end
16
for journaling on a central portion of a wrist pin for coupling the connecting rod to the piston (as schematically shown). A variable length mechanism
18
is embodied in the connecting rod at its large end to provide for variation in overall length as measured between the large and small ends.
Large end
14
comprises an upper cap
20
and a lower cap
22
that are fastened together around the crank pin. Lower cap
22
comprises parallel through-holes
26
,
28
at opposite ends of its semi-circumference. At opposite ends of its semi-circumference, upper cap
20
comprises through-holes
30
,
32
that align with holes
26
,
28
respectively when the two caps are girdling the crank pin.
Connecting rod
12
further comprises a part
34
containing a connecting rod portion
35
. One end of part
34
contains small end
16
, and the opposite end is coupled through variable length mechanism
18
with large end
14
. That coupling comprises through-holes
36
,
38
that align with through-holes
30
,
32
respectively, fasteners
40
,
42
, and nuts
41
,
43
. Through-holes
36
,
38
are disposed mutually parallel, and are contained in free ends of curved arms
45
that extend from connecting rod portion
35
.
Each fastener
40
,
42
comprises a head
44
at a proximal end and a screw thread
46
at a distal end. Intermediate proximal and distal ends, each fastener comprises a circular cylindrical guide surface
48
. The parts are assembled in the manner suggested by the Figures with the respective fastener shanks passing though respective aligned through-holes
36
,
30
;
38
,
32
; and
26
,
28
; and threading into respective nuts
41
,
43
. The diameters of through-holes
36
,
38
are larger than those of through-holes
30
,
32
to allow shoulders
50
at the ends of guides
48
to bear against the margins of through-holes
30
,
32
. As the fasteners and nuts are tightened, such as by turning with a suitable tightening tool, the two caps
20
,
22
are thereby forced together at their ends, crushing the crank pin bearing in the process.
The axial length of each guide surface
48
, as measured between head
44
and shoulder
50
, is slightly greater than the axial length of each through-hole
36
,
38
, and the diameters of the latter are slightly larger than those of the former to provide sliding clearance. In this way it becomes possible for rod part
34
to slide axially over a short range of motion relative to large end
12
. That range of motion is indicated by the reference
52
in FIG.
2
and constitutes a limited adjustment range for changing the length of the connecting rod assembly. When arms
45
abut part
20
around the margins of through-holes
30
,
32
, the connecting rod assembly has minimum length. When arms
45
abut heads
44
, the connecting rod assembly has maximum length.
Channels
54
may be assembled at the sides to provide additional bearing support for the axial sliding motion. Mechanism
18
may comprise passive and/or active elements for accomplishing overall length change, and resulting compression ratio change.
FIGS. 3 and 4
illustrate the connecting rod
62
of a second piston/connecting rod embodiment
60
for endowing an engine with a variable compression ratio. Connecting rod
62
comprises a large end
64
for journaling on a crank pin of a crankshaft (not shown) and a small end
66
for journaling on a central portion of a wrist pin (also not shown) for coupling the connecting rod to the piston (also not shown). A variable length mechanism
68
is embodied in the connecting rod at its large end to provide for variation in overall length between the large and small ends.
Mechanism
68
is provided by a bearing retainer
70
which is captured between a cap
72
and one end of a rod part
74
. Opposite ends of the semi-circumference of cap
72
contain holes
76
,
78
that align with threaded holes
80
,
82
in rod part
74
. Fasteners
84
,
86
fasten the cap to the rod part. The cap and rod part have channels
88
,
90
that fit to respective portions of a flange
92
of bearing retainer
70
. The channel and flange depths are chosen to allow the assembled cap and rod part to move axially a short distance on the bearing retainer, thereby changing the overall length, as marked by the reference
94
in FIG.
4
. Mechanism
68
may comprise passive and/or active elements for accomplishing overall length change and corresponding compression ratio change. The channels form the groove, and the flange the tongue, of a tongue-and groove type joint providing for sliding motion that adjusts the length of the connecting rod assembly.
While a presently preferred embodiment has been illustrated and described, it is to be appreciated that the invention may be practiced in various forms within the scope of the following claims.
Claims
- 1. A variable length connecting rod assembly for imparting a variable compression ratio to an internal combustion engine, the assembly comprising:a first part, a second part, and a third part assembled together to form the large end of the connecting rod assembly and provide a variable length for the connecting rod assembly; the first part comprising a semi-circular cap; one of the second and third parts being fastened tight to the first part; and guides disposed at opposite sides of the large end operatively relating the other of the second and third parts and the fastened parts to provide for relative sliding motion between the other of the second and third parts and the fastened parts over a limited adjustment range to change the length of the connecting rod assembly; fasteners disposed on opposite sides of the large end for fastening the one of the second and third parts tight to the first part; wherein the one of the second and third parts fastened tight to the first part by the fasteners comprises a semi-circular cap fastened to the semi-circular cap of the first part providing for the two fastened semi-circular caps to girdle a crank pin; and the guides comprise surfaces of the fasteners disposed in through-holes in the other of the second and third parts.
- 2. A variable length connecting rod assembly as set forth in claim 1 in which the other of the second and third parts comprises a connecting rod portion, and the through-holes are disposed at ends of arms of the other of the second and third parts that extend to opposite side of the connecting rod portion at the large end of the connecting rod assembly.
- 3. A variable length connecting rod assembly as set forth in claim 2 further comprising additional parts assembled to opposite sides of the large end of the connecting rod assembly to aid in providing guidance for relative sliding motion between the other of the second and third parts and the fastened parts.
- 4. A variable length connecting rod assembly as set forth in claim 3 in which the additional parts comprises channels.
- 5. A variable length connecting rod assembly as set forth in claim 1 in which the fasteners comprise shoulders spaced from heads, the shoulders abut the one of the second and third parts to fasten the one part tight to the first part, and the heads are disposed to be abutted by the other of the second and third parts to define a limit of maximum length for the connecting rod assembly.
- 6. A variable length connecting rod assembly for imparting a variable compression ratio to an internal combustion engine, the assembly comprising:a first part, a second part, and a third part assembled together to form the large end of the connecting rod assembly and provide a variable length for the connecting rod assembly along a longitudinal centerline extending from the large end to a point of attachment to a piston; the first part comprising a semi-circular cap; one of the second and third parts being fastened tight to the first part; and guides disposed at opposite sides of the large end lateral to and parallel with the longitudinal centerline for operatively relating the other of the second and third parts and the fastened parts to provide for relative sliding motion between the other of the second and third parts and the fastened parts over a limited adjustment range to change the length of the connecting rod assembly; fasteners disposed on opposite sides of the large end for fastening the one of the second and third parts tight to the first part; wherein the one of the second and third parts fastened tight to the first part by the fasteners comprises a connecting rod portion having, at one end, a semi-circular cap fastened to the semi-circular cap of the first part, the two fastened caps capture the other of the second and third parts, and the guides comprise tongue-and-groove type guides; the tongues are disposed on the other of the second and third parts, and the grooves are disposed on the two fastened semi-circular caps.
US Referenced Citations (11)
Foreign Referenced Citations (1)
Number |
Date |
Country |
19844200 |
Jun 1999 |
DE |