Title: Reciprocating engine with a variable compression ratio mechanism
Abstract: A reciprocating engine with a variable compression ratio mechanism is disclosed. A lubrication system of the engine is improved by controlling an oil pressure according to a compression ratio setting. The lubrication system includes various combinations of control valves and oil passages. The oil relief passage is opened at a high compression ratio setting applied to a low engine load range and is otherwise closed at a low compression ratio setting applied to a high engine load range.
Patent Number: 6,920,847 Issued on 07/26/2005 to Hiyoshi, et al.
| Inventors:
|
Hiyoshi; Ryosuke (Kanagawa, JP);
Ushijima; Kenshi (Kanagawa, JP);
Yasuda; Yoshiteru (Yokohama, JP);
Moteki; Katsuya (Tokyo, JP)
|
| Assignee:
|
Nissan Motor Co., Ltd. (Yokohama, JP)
|
| Appl. No.:
|
756470 |
| Filed:
|
January 14, 2004 |
Foreign Application Priority Data
| Feb 24, 2003[JP] | 2003-045709 |
| Current U.S. Class: |
123/48B; 123/78; 123/196.R |
| Intern'l Class: |
F02B 075/04 |
| Field of Search: |
123/48 R,48.B,78.E,78.F,196.R
|
References Cited [Referenced By]
U.S. Patent Documents
| 4195601 | Apr., 1980 | Crise.
| |
| 5247911 | Sep., 1993 | Nenicka.
| |
| 6397796 | Jun., 2002 | Styron et al.
| |
| 6505582 | Jan., 2003 | Moteki et al.
| |
| 6736091 | May., 2004 | Tibbles.
| |
| Foreign Patent Documents |
| 1 170 482 | Jan., 2002 | EP.
| |
| 1 178 194 | Feb., 2002 | EP.
| |
| 2002-21592 | Jan., 2002 | JP.
| |
Primary Examiner: Kamen; Noah P.
Attorney, Agent or Firm: Foley & Lardner LLP
Claims
1. A reciprocating engine comprising:
a variable compression ratio mechanism for regulating an engine compression ratio
according to an engine load;
a main oil passage;
an oil pressure source hydraulically connected to the main oil passage for supplying
pressurized lubricating oil to the main oil passage;
an oil supply passage hydraulically connecting the main oil passage to a lubricated
element; and
an oil pressure control device for controlling an oil pressure in the main oil
passage for the lubricated element according to the engine compression ratio, the
oil pressure control device comprising a mechanism for varying a relative distribution
of an oil supply pressure for a lubricated element subset according to the engine
compression ratio.
2. The reciprocating engine as claimed in claim 1 wherein:
the oil pressure control device lowers the oil pressure in the main oil passage
at a high compression ratio setting and keeps the oil pressure in the main oil
passage at a low compression ratio setting.
3. A reciprocating engine comprising:
a variable compression ratio mechanism for regulating an engine compression ratio
according to an engine load;
a main oil passage;
an oil pressure source hydraulically connected to the main oil passage for supplying
pressurized lubricating oil to the main oil passage;
an oil supply passage hydraulically connecting the main oil passage to a lubricated
element; and
an oil pressure control device for controlling an oil pressure in the main oil
passage according to the engine compression ratio, and for lowering the oil pressure
in the main oil passage at a low compression ratio when an oil temperature of the
lubricating oil is high.
4. A reciprocating engine comprising:
a variable compression ratio mechanism for regulating an engine compression ratio
according to an engine load;
a main oil passage;
an oil pressure source hydraulically connected to the main oil passage for supplying
pressurized lubricating oil to the main oil passage;
an oil supply passage hydraulically connecting the main oil passage to a lubricated
element;
an oil pressure control device for controlling an oil pressure in the main oil
passage according to the engine compression ratio;
a cylinder head oil gallery adapted to be formed in a cylinder head;
a cylinder head main oil passage hydraulically connecting the main oil passage
to the cylinder head oil gallery;
a cylinder head sub oil passage hydraulically connecting the main oil passage
to the cylinder head oil gallery; and
a cylinder head oil pressure control device provided in the cylinder head sub
oil passage for controlling an oil supply pressure for the cylinder head oil gallery
from the main oil passage,
wherein the main oil passage comprises a main oil gallery formed in a cylinder
block.
5. The reciprocating engine as claimed in claim 4 wherein:
a fluid resistance of the cylinder head sub oil passage is smaller than that
of the cylinder head main oil passage; and
the cylinder head oil pressure control device opens the cylinder head sub oil
passage at a high compression ratio setting and closes the cylinder head sub oil
passage at a low compression ratio setting.
6. The reciprocating engine as claimed in claim 4 wherein:
the cylinder head oil pressure control device comprises:
an oil relief passage for relieving lubricating oil from the main oil gallery;
and
a control valve for regulating an opening of the oil relief passage according
to a compression ratio setting, and
the cylinder head sub oil passage is connected downstream of the oil relief passage
from the control valve.
7. The reciprocating engine claimed as claim 6 wherein:
the control valve comprises:
a thick in-valve oil passage having a smaller fluid resistance; and
a thin in-valve oil passage having a larger fluid resistance;
the control valve opens the oil relief passage;
the oil relief passage is connected to the cylinder head sub oil passage only
via the thick in-valve oil passage at a high compression ratio setting; and
the control valve closes the oil relief passage, and the oil relief passage is
connected to the cylinder head sub oil passage via the thin in-valve oil passage
at a low compression ratio setting.
8. A reciprocating engine comprising:
a variable compression ratio mechanism for regulating an engine compression ratio
according to an engine load;
a main oil passage;
an oil pressure source hydraulically connected to the main oil passage for supplying
pressurized lubricating oil to the main oil passage;
an oil supply passage hydraulically connecting the main oil passage to a lubricated
element; and
an oil pressure control device for controlling an oil pressure in the main oil
passage according to the engine compression ratio,
wherein the oil pressure control device comprises:
an oil relief passage for relieving a lubricating oil from the main oil passage;
and
a control valve for regulating an opening of the oil relief passage according
to an engine compression ratio setting, the control valve comprising a moving element
of the variable compression ratio mechanism for being moved during the engine compression
ratio setting being varied and for being positioned according to the engine compression
ratio setting.
9. The reciprocating engine as claimed in claim 8 wherein:
the variable compression ratio mechanism comprises:
a lower link rotatably attached to a crankpin of a crankshaft;
an upper link pivotally connected at one end to the lower link and at another
end to a piston;
a control shaft rotatably supported by a cylinder block, the control shaft comprising
an eccentric cam;
a control link pivotally connected at one end to the eccentric cam and at another
end to the lower link;
a compression-ratio control actuator for regulating a rotation angle of the control
shaft to set an engine compression ratio.
10. The reciprocating engine as claimed in claim 9 wherein:
the control shaft comprises a journal rotatably supported on the cylinder block,
the journal having a portion which functions as the control valve according to
the rotation angle of the control shaft.
11. The reciprocating engine as claimed in claim 10 wherein:
the control shaft comprises an in-valve oil passage formed as a part of the oil
relief passage; and
the cylinder block comprises a control-shaft bearing cap for supporting the control
shaft, the control-shaft bearing cap comprising an oil passage formed as a part
of the oil relief passage.
12. The reciprocating engine as claimed in claim 10 wherein:
the control shaft comprises an in-valve oil passage formed as a part of the oil
relief passage, the in-valve oil passage comprising:
an axial oil passage placed along a longitudinal direction of the control shaft;
a first radial oil passage hydraulically connected at one end to the axial oil
passage and at another end to an opening in an outer surface of the journal; and
a second radial oil passage hydraulically connected at one end to the axial oil
passage and at another end to an opening in an outer surface of the eccentric cam.
13. The reciprocating engine as claimed in claim 12 wherein:
the control shaft comprises an in-valve oil passage formed as a part of the oil
relief passage; and
the cylinder block comprises a control-shaft bearing cap for supporting the control
shaft, the control-shaft bearing cap comprising an oil passage formed as a part
of the oil relief passage.
14. The reciprocating engine as claimed in claim 9 wherein:
the compression-ratio control actuator comprises:
a piston housing rigidly attached to the engine;
a piston rod slidably supported on the piston housing and connected at one end
to a periphery of the control shaft, for stroking relative to the piston housing
to regulate the rotation angle of control shaft;
the piston housing having a portion formed as a part of the oil relief passage;
and
the piston rod having a portion formed as a part of the oil relief passage for
functioning as the valve according to a position of the piston rod relative to
the piston housing.
15. The reciprocating engine as claimed in claim 9 further comprising:
a cylinder head oil gallery formed in a cylinder head;
a cylinder head main oil passage hydraulically connecting the main oil passage
to the cylinder head oil gallery;
a cylinder head sub oil passage hydraulically connecting the main oil passage
to the cylinder head oil gallery; and
a cylinder head oil pressure control device provided in the cylinder head sub
oil passage for controlling an oil supply pressure for the cylinder head oil gallery
from the main oil passage,
wherein the main oil passage comprises a main oil gallery formed in the cylinder
block.
16. The reciprocating engine as claimed in claim 15 wherein:
the control shaft comprises a journal rotatably supported on the cylinder block,
the journal having a portion which functions as the control valve according to
the rotation angle of the control shaft.
17. The reciprocating engine as claimed in claim 15 wherein:
the compression-ratio control actuator comprises:
a piston housing rigidly attached to the engine;
a piston rod slidably supported on the piston housing and connected at one end
to a periphery of the control shaft, for stroking relative to the piston housing
to regulate the rotation angle of the control shaft;
the piston housing having a portion formed as a part of the oil relief passage;
and
the piston rod having a portion formed as a part of the oil relief passage for
functioning as the valve according to a position of the piston rod relative to
the piston housing.
18. A reciprocating engine comprising:
a variable compression ratio mechanism for regulating an engine compression ratio;
a main oil passage;
an oil pressure source hydraulically connected to the main oil passage for supplying
pressurized lubricating oil to the main oil passage;
an oil supply passage hydraulically connecting the main oil passage to a lubricated
element; and
an oil pressure control device for controlling an oil pressure in the main oil
passage for the lubricated element according to an engine load which is a parameter
used to determine the engine compression ratio, the oil pressure control device
comprising a mechanism for varying a relative distribution of an oil supply pressure
for a lubricated element subset according to the engine compression ratio.
19. A reciprocating engine comprising:
a variable compression ratio mechanism for regulating an engine compression ratio
according to an engine load;
a main oil passage;
an oil pressure source hydraulically connected to the main oil passage for supplying
pressurized lubricating oil to the main oil passage;
oil supply means for supplying lubricating oil from the oil pressure source via
the main oil passage to a lubricated element; and
oil pressure control means for controlling an oil pressure in the main oil passage
for the lubricated element according to the engine compression ratio, the oil pressure
control means comprising means for varying a relative distribution of an oil supply
pressure for a lubricated element subset according to the engine compression ratio.
20. A reciprocating engine comprising:
a variable compression ratio mechanism for regulating an engine compression ratio;
a main oil passage;
an oil pressure source hydraulically connected to the main oil passage for supplying
pressurized lubricating oil to the main oil passage;
oil supply means for supplying lubricating oil from the oil pressure source via
the main oil passage to a lubricated element; and
oil pressure control means for controlling an oil pressure in the main oil passage
for the lubricated element according to an engine load which is a parameter used
to determine the engine compression ratio, the oil pressure control means comprising
means for varying a relative distribution of an oil supply pressure for a lubricated
element subset according to the engine compression ratio.
21. A method of regulating an oil pressure in a main oil passage of a reciprocating
engine including at least a variable compression ratio mechanism for regulating
an engine compression ratio, a main oil passage, an oil pressure source hydraulically
connected to the main oil passage for supplying pressurized lubricating oil to
the main oil passage, an oil supply passage hydraulically connecting the main oil
passage to a lubricated element, and an oil pressure control device for controlling
an oil pressure in the main oil passage, the method comprising:
determining whether the engine compression ratio is high or low relative to a
predetermined value;
operating the oil pressure control device for keeping the pressure in the main
oil passage for the lubricated element when the engine compression ratio is low;
operating the oil pressure control device for lowering the pressure in the main
oil passage for the lubricated element when the engine compression ratio is high;
and
varying a relative distribution of an oil supply pressure for a lubricated element
subset according to the engine compression ratio.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to a reciprocating internal combustion
engine with a variable compression ratio mechanism including a multiple-link type
piston crank mechanism, and more particularly to an improvement in a lubrication
system of the engine.
Recent years, there have been disclosed various variable compression ratio
mechanisms of a reciprocating internal combustion engine with a multiple-link type
piston crank mechanism which are capable of varying the top dead center (TDC) position
and/or the bottom dead center (BDC) of a piston and the engine compression ratio
by displacing a part of elements of the linkage. One such mechanism is disclosed
in Japanese Patent Provisional Publication No. 2002-21592 published Jan. 23, 2002
(corresponding to U.S. Pat. No. 6,505,582 assigned to the assignee of the present
invention Jan. 14, 2003). This variable compression ratio mechanism includes an
upper link connected at one end to a piston with a piston pin, a lower link oscillatably
or rockably pin-connected to the other end of the upper link with an upper pin
and rotatably attached to a crankpin of a crankshaft, a control link oscillatably
pin-connected at one end to the lower link with a control pin, a control shaft
rotatably mounted onto a cylinder block and having an eccentric cam oscillatably
supporting the other end of the control link, for varying the engine compression
ratio by regulating the position of the eccentric cam of the control shaft according
to an engine operating condition.
SUMMARY OF THE INVENTION
In the aforementioned reciprocating engine with a variable compression ratio
mechanism,
lubrication is necessary for three elements, that is, a control shaft, a control
pin and an upper pin in addition to general lubricated elements such as a crankshaft,
a crankpin and a piston pin. There is a possibility accordingly that an inadequate
oil supply leads to a trouble in the lubrication of a piston skirt and bearings
under a high engine load condition. If the oil pressure or the oil supply is excessively
increased as a countermeasure against a lubrication trouble, an excessive oil supply
for less oil demand leads to a useless work of the oil pump, which consequently
results in a low fuel efficiency.
Accordingly, it is an object of the present invention to improve a lubrication
system of a reciprocating engine with a variable compression ratio mechanism.
In order to accomplish the aforementioned and other objects of the present invention,
a reciprocating engine comprises a variable compression ratio mechanism for regulating
an engine compression ratio according to an engine load, a main oil passage, an
oil pressure source hydraulically connected to the main oil passage for supplying
pressurized lubricating oil to the main oil passage, an oil supply passage hydraulically
connecting the main oil passage to a lubricated element, and an oil pressure control
device for controlling an oil pressure in the main oil passage according to the
engine compression ratio.
According to another aspect of the invention, a reciprocating engine comprises
a variable compression ratio mechanism for regulating an engine compression ratio,
a main oil passage, an oil pressure source hydraulically connected to the main
oil passage for supplying pressurized lubricating oil to the main oil passage,
an oil supply passage hydraulically connecting the main oil passage to a lubricated
element, and an oil pressure control device for controlling an oil pressure in
the main oil passage according to an engine load which is a parameter used to determine
the engine compression ratio.
According to a further aspect of the invention, a reciprocating engine
comprises a variable compression ratio mechanism for regulating an engine compression
ratio according to an engine load, a main oil passage, an oil pressure source hydraulically
connected to the main oil passage for supplying pressurized lubricating oil to
the main oil passage, oil supply means for supplying lubricating oil from the oil
pressure source via the main oil passage to a lubricated element, and oil pressure
control means for controlling an oil pressure in the main oil passage according
to the engine compression ratio.
According to a still further aspect of the invention, a reciprocating engine
comprises a variable compression ratio mechanism for regulating an engine compression
ratio, a main oil passage, an oil pressure source hydraulically connected to the
main oil passage for supplying pressurized lubricating oil to the main oil passage,
oil supply means for supplying lubricating oil from the oil pressure source via
the main oil passage to a lubricated element, and oil pressure control means for
controlling an oil pressure in the main oil passage according to an engine load
which is a parameter used to determine the engine compression ratio.
According to another aspect of the invention, a method of regulating an
oil pressure in a main oil passage of a reciprocating engine including at least
a variable compression ratio mechanism for regulating an engine compression ratio,
a main oil passage, an oil pressure source hydraulically connected to the main
oil passage for supplying pressurized lubricating oil to the main oil passage,
an oil supply passage hydraulically connecting the main oil passage to a lubricated
element, and an oil pressure control device for controlling an oil pressure in
the main oil passage, the method comprises determining whether the engine compression
ratio is high or low relative to a predetermined value, operating the oil pressure
control device for keeping the pressure in the main oil passage when the engine
compression ratio is low, and operating the oil pressure control device for lowering
the pressure in the main oil passage when the engine compression ratio is high.
The above objects and other objects, features, and advantages of the present
invention are readily apparent from the following detailed description of the best
modes for carrying out the invention when taken in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 is a cross-sectional view of a variable compression ratio mechanism of
a reciprocating engine of the present invention.
FIG. 2A is a block diagram depicting a lubrication system of a 1st embodiment
of the present invention at a high engine compression ratio setting.
FIG. 2B is a block diagram depicting the lubrication system of the 1st embodiment
of the present invention at a low engine compression ratio setting.
FIG. 3A is a block diagram depicting a lubrication system of a 2nd embodiment
of the present invention under a low engine speed and low engine load condition.
FIG. 3B is a block diagram depicting the lubrication system of the 2nd embodiment
of the present invention under a high engine speed and high engine load condition.
FIG. 4A is a block diagram depicting a lubrication system of a 3rd embodiment
of the present invention at a high engine compression ratio setting.
FIG. 4B is a block diagram depicting the lubrication system of the 3rd embodiment
of the present invention at another high engine compression ratio setting.
FIG. 4C is a block diagram depicting the lubrication system of the 3rd embodiment
of the present invention at a low engine compression ratio setting.
FIG. 5 is a cross-sectional view of a variable compression ratio mechanism of
a 4th embodiment of the present invention, which includes a compression-ratio control
actuator as a part of the system.
FIG. 6A is a block diagram depicting a lubrication system of the 4th embodiment
of the present invention at a high engine compression ratio setting.
FIG. 6B is a block diagram depicting the lubrication system of the 4th embodiment
of the present invention at a low engine compression ratio setting.
FIG. 7A is a cross-sectional view taken along the plane indicated by the line
VIIA-VIIA in FIG. 7B, depicting a lubrication system of a 5th embodiment of the
present invention, which includes a control shaft as a part of the system, at a
high engine compression ratio setting.
FIG. 7B is a block diagram depicting the lubrication system of the 5th embodiment
of the present invention at the high engine compression ratio setting.
FIG. 8A is a cross-sectional view taken along the plane indicated by the line
VIIIA-VIIIA in FIG. 8B, depicting the lubrication system of the 5th embodiment
of the present invention at a low engine compression ratio setting.
FIG. 8B is a block diagram depicting the lubrication system of the 5th embodiment
of the present invention at the low engine compression ratio setting.
FIG. 9A is a cross-sectional view taken along the plane indicated by the line
IXA-IXA in FIG. 9B, depicting a lubrication system of a 6th embodiment of the present
invention, which includes a control shaft as a part of the system, at a high engine
compression ratio setting.
FIG. 9B is a block diagram depicting the lubrication system of the 6th embodiment
of the present invention at the high engine compression ratio setting.
FIG. 9C is a cross-sectional view taken along the plane indicated by the line
IXC-IXC in FIG. 9B, depicting the lubrication system of the 6th embodiment of the
present invention at the high engine compression ratio setting.
FIG. 10A is a cross-sectional view taken along the plane indicated by the line
XA-XA in FIG. 10B, depicting the lubrication system of the 6th embodiment of the
present invention at a low engine compression ratio setting.
FIG. 10B is a block diagram depicting the lubrication system of the 6th embodiment
of the present invention at the low engine compression ratio setting.
FIG. 10C is a cross-sectional view taken along the plane indicated by the line
XC-XC in FIG. 10B, depicting the lubrication system of the 6th embodiment of the
present invention at the low engine compression ratio setting.
FIG. 11A is a block diagram depicting a lubrication system of a 7th embodiment
of the present invention at a high engine compression ratio setting.
FIG. 11B is a block diagram depicting the lubrication system of the 7th embodiment
of the present invention at a low engine compression ratio setting.
FIG. 12 is a graph depicting characteristic curves of oil pressures in relation
to an engine speed, in a main oil gallery and a cylinder head oil gallery of the
7th embodiment of the present invention.
FIG. 13A is a block diagram depicting a lubrication system of a 8th embodiment
of the present invention at a high engine compression ratio setting.
FIG. 13B is a block diagram depicting the lubrication system of the 8th embodiment
of the present invention at a low engine compression ratio setting.
FIG. 14A is a block diagram depicting a lubrication system of a 9th embodiment
of the present invention at a high engine compression ratio setting.
FIG. 14B is a block diagram depicting the lubrication system of the 9th embodiment
of the present invention at a low engine compression ratio setting.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, particularly to FIGS. 1 through 2B, there
is shown a variable compression ratio mechanism common to all embodiments described later.
The variable compression ratio mechanism includes a lower link
2 rotatably
attached to a crankpin
12 of a crankshaft
1, an upper link
5
connecting lower link
2 to a piston
3, a control shaft
7 having
an eccentric cam
8, and a control link
6 connecting eccentric cam
8 to lower link
2. The rotation angle of control shaft
7 is
varied by a compression-ratio control actuator
51 (described later, refer
to FIG. 5) mainly according to the engine load condition. The motion restriction
condition of lower link
2 by control link
6 is changed accordingly,
so that the characteristics of the stroke of piston
3, specifically, the
TDC position and/or the BDC position and the engine compression ratio of piston
3 are varied or controlled.
More specifically, crankshaft
1 includes a plurality of journals
11
and crankpins
12. Each journal
11 is rotatably supported on a main
bearing between a cylinder block
21 and a crankshaft bearing cap
22.
Lower link
2 is rotatably attached to crankpin
12 which has a predetermined
eccentricity from the rotation center of journal
11. Lower link
2
consists of two split members. Crankpin
12 is mated with a connecting hole
defined between the two split members of lower link
2. Upper link
5
is pivotally connected at a lower end via an upper pin
10 to one end of
lower link
2, and also pivotally connected at an upper end via a piston
pin
4 to piston
3. Piston
3 is reciprocated in a cylinder
bore
23 of cylinder block
21 by the burning pressure. Control link
6 is pivotally connected at a small end or an upper end via a control pin
9 to the other end of lower link
2, and oscillatably or rockably
connected at a big end or a lower end to eccentric cam
8 of control shaft
7. Control shaft
7 is placed parallel to crankshaft
1 and
rotatably supported on a main bearing between crankshaft bearing cap
22
and a control-shaft bearing cap
24 attached on the lower side of crankshaft
bearing cap
22. Eccentric cam
8 is offset from the rotation center
of control shaft
7. Control-shaft bearing cap
24 is formed as a ladder-shaped
or a bearing beam structure where a plurality of bearing caps are connected to
a beam along the longitudinal direction of the engine.
The rotation angle of control shaft
7 is regulated or controlled by a
compression-ratio control actuator including an electric motor, such as compression-ratio
control actuator
51 shown in FIG. 5, according to the control signal from
an engine control unit (not shown). The compression-ratio control actuator rotates
control shaft
7 to displace the center of eccentric cam
8 and to
raise or lower the oscillating center at a lower end of control link
6.
Accordingly, the geometry of lower link
2 at TDC is changed to raise or
lower the position of piston
3 at TDC. Therefore it is possible to vary
the compression ratio. This control of the compression ratio is operated based
on an engine operating condition, generally sets a lower compression ratio to a
higher engine load condition.
As shown in FIGS. 2A and 2B, an oil pump
31 as an oil pressure source,
which is driven by the torque of crankshaft
1, sumps lubricating oil stored
in an oil pan
32, pressurizes the lubricating oil and feeds a main oil gallery
33 as a main oil passage formed in cylinder block
21 (refer to FIG.
1) under pressure. The oil supplied to main oil gallery
33 is distributed
to a plurality of lubricated elements
34 (oil supplied elements) in cylinder
block
21, such as bearings on crankshaft
1 which elements are necessary
to be lubricated. The oil in main oil gallery
33 is partly supplied via
a cylinder head main oil supply passage
36 to a cylinder head oil gallery
35 formed in the cylinder head. The oil is mainly supplied to a plurality
of lubricated elements (not shown) such as a valve train and a bearing on a camshaft
in the cylinder head. The oil returns to oil pan
32 after lubricating the
lubricated elements. In FIGS. 2A,
2B, a thickness of a line such as oil
passages
36,
37 is corresponding to an oil pressure or an oil quantity,
as a higher oil pressure or a larger oil quantity is shown as a thicker line and
a lower oil pressure or a smaller oil quantity is shown as a thinner line. In other
drawings depicting a lubrication system, the same symbols are applied.
The oil pressure in main oil gallery
33 pressurized by oil pump
31
mainly depends on the engine speed, because oil pump
31 is driven by the
torque of crankshaft
1. The oil pressure necessary for supplying lubricating
oil properly to the lubricated elements varies mainly according to the engine load
condition. In general, a higher engine load condition demands a higher oil pressure.
In the aforementioned reciprocating engine with a variable compression ratio mechanism,
lubrication is necessary for three elements, that is, a control shaft, a control
pin and an upper pin in addition to general lubricated elements such as a crankshaft,
a crankpin and a piston pin. Accordingly, there is a possibility that inadequate
oil supply leads to a trouble in the lubrication of a piston skirt and bearings
under a high engine load condition. If oil pressure or oil supply is excessively
increased as a countermeasure against a lubrication trouble, an excessive oil supply
for less oil demand leads to a useless work of the oil pump, which consequently
results in a low fuel efficiency.
In order to improve the mechanism, the following embodiments include oil pressure
control means for regulating the oil pressure in main oil gallery
33 according
to the compression ratio set by the variable compression ratio mechanism or to
the engine load condition. Consequently, lubricating oil is properly supplied to
the lubricated elements according to the compression ratio setting or the engine
load condition. Under a low engine load condition where a high compression ratio
is applied, the oil pressure is lowered to reduce a work loss of the oil pump for
the improvement of fuel efficiency. On the other hand, under a high engine load
condition where a low compression ratio is applied, oil pressure in main oil gallery
33 is kept high without falling. Lubricating oil is thus enough supplied
to lubricated elements to prevent securely seizes and lubrication failures at the
lubricated elements.
In all following embodiments, the oil pressure control means include oil relief
passage
37 connected to main oil gallery
33 for relieving oil from
main oil gallery
33, a control valve (such as a valve
38 in a first
embodiment) as an oil pressure regulating mechanism for regulating the oil pressure
in main oil gallery
33 by selecting or changing the opening of oil relief
passage
37 according to the compression ratio setting or the engine load
condition. This control valve may be a two-position selector type which sets oil
relief passage
37 to be open or closed, or a continuously variable type
which can continuously regulate oil pressure and oil flow.
Referring now to FIGS. 2A and 2B, there is shown a first embodiment of
the present invention. In the first embodiment, valve
38 such as a solenoid
valve is provided to open or close oil relief passage
37. Valve
38
is operated by a control unit such as an engine control unit according to the compression
ratio setting.
As shown in FIG. 2A, oil relief passage
37 is opened by valve
38
at a high compression ratio setting mainly applied to a low engine load condition.
In this way, a part of the oil is relieved from main oil gallery
33 via
oil relief passage
37 to lower the oil pressure in main oil gallery
33.
Accordingly, the work loss of oil pump
31 is reduced to improve fuel efficiency
under a low engine load condition. On the other hand as shown in FIG. 2B, oil relief
passage
37 is closed by valve
38 at a low compression ratio setting
mainly applied to a high engine load condition. In this way, no oil is relieved
via oil relief passage
37 to keep a high oil pressure. Accordingly, the
lubricated elements are enough supplied with lubricating oil to prevent a lubrication
failure under a high engine load condition.
Referring now to FIGS. 3A and 3B, there is shown a second embodiment of
the present invention. In the second embodiment, valve
38 such as a solenoid
valve is operated according not to the compression ratio setting but to the engine
load (more specifically a target driving torque calculated on variable factors
such as an accelerator opening. In detail shown in FIG. 3A, oil relief passage
37 is opened by valve
38 under a low engine speed and low engine
load condition to lower the oil pressure in main oil gallery
33. On the
other hand as shown in FIG. 3B, oil relief passage
37 is closed by valve
38 under a high engine speed and high engine load condition to keep a high
oil pressure in main oil gallery
33. In this way, there are provided similar
effects as in the case of the first embodiment.
In General, a high compression ratio setting is applied to a low engine speed
and low engine load condition. For instance, however, a low compression ratio setting
is applied to a low engine speed and low engine load condition by way of exception
where temperatures of oil and water are high just after a high engine load operation.
In this state, the oil pressure in main oil gallery
33 can be properly changed
or regulated by controlling oil pressure according to the engine load.
Referring now to FIGS. 4A,
4B and
4C, there is shown a third
embodiment of the present invention. In the third embodiment, a valve
41
such as a solenoid valve is placed in oil relief passage
37 to open or close
oil relief passage
37 and to change or regulate the oil supply and the oil
supply pressure to a particular lubricated element subset
34a. Valve
41 changes the distribution of the oil supply and the oil supply pressure
to each lubricated element such as a valve train, a camshaft bearing and a crankshaft
bearing, which needs lubrication, according to the compression ratio setting. In
detail, valve
41 is connected to partial oil supply passage
42 which
is connected to lubricated element subset
34a, and is provided with
in-valve oil passage
43 which is simply shown as a T-shape in the figures,
to open or close oil relief passage
37 and/or partial oil supply passage
42.
As shown in FIG. 4A, oil relief passage
37 is opened and partial oil supply
passage
42 is closed at a first high compression ratio setting. In this
way, the oil pressure in main oil gallery
33 is lowered via oil relief passage
37 to prevent an unnecessary work loss of oil pump
31. Partial oil
supply passage
42 is closed so that lubricating oil is not supplied to lubricated
element subset
34a by priority.
As shown in FIG. 4B, oil relief passage
37 and partial oil supply passage
42 are both opened by valve
41 at a second high compression ratio
setting (for example, the compression ratio is lower than that of the first high
compression ratio setting). In this way, the oil pressure in main oil gallery
33
is lowered via oil relief passage
37 to prevent an unnecessary loss of oil
pump
31. Lubricating oil is supplied to lubricated element subset
34a
via partial oil supply passage
42 by priority to increase the oil flow
and the oil pressure in lubricated element subset
34a relative to
other lubricated elements. Accordingly, potential inadequate lubrication for lubricated
element subset
34a can be effectively avoided.
As shown in FIG. 4C, oil relief passage
37 is closed and partial oil supply
passage
42 is opened at a low compression ratio setting mainly applied to
a high engine load condition. In this way, lubricating oil is supplied to lubricated
element subset
34a via partial oil supply passage
42 by priority
while the oil pressure in main oil gallery
33 is not lowered by oil relief
passage
37. Accordingly, potential inadequate lubrication for lubricated
element subset
34a can be effectively avoided.
In the third embodiment, similar effects as in the case of the first embodiment
is provided. In addition, the oil distribution to lubricated element subset
34a
can be properly changed according to the compression ratio setting, to supply
a proper amount of lubricating oil to each lubricated element according to the
compression ratio setting. The lubricated elements where a small amount of oil
supply is enough at a high compression ratio and low engine load condition, that
is, lubricated elements except lubricated element subset
34a includes
a piston skirt, a cylinder bore, and the sliding surfaces of main moving elements
such as a crankshaft and crankpin bearings. In general, a reciprocating engine
of a single link type where a single connecting rod connects a piston pin to a
crankpin, structurally has a uniquely defined angle of the connecting rod from
the piston stroke line according to the piston stroke position. Accordingly, a
relatively large piston thrust load is imposed by the burning pressure under a
low engine speed range corresponding to a high fuel efficiency range. Therefore
a relatively large amount of oil supply is necessary for the piston skirt and the
cylinder bore. On the other hand, when the aforementioned variable compression
ratio mechanism is applied, upper link
5 corresponding to the connecting
rod of the single link type can keep a geometry closely along the piston stroke
line in a burning time period. Accordingly, a piston thrust load caused by the
burning pressure can be greatly reduced. Therefore the oil supply to the piston
skirt and the cylinder bore can be reduced under a low engine speed and low engine
load condition corresponding to a high fuel efficiency range.
The input load mainly varies according to the burning pressure and the inertial
load at the sliding surfaces of main moving elements such as a crankshaft and crankpin
bearings. A small amount of oil supply is enough when the input load is small,
for example, under a low engine load condition. Necessary oil supply increases
with the input load. On the other hand at sliding surfaces in the cylinder head
such as a valve train and a camshaft, a change of a necessary oil supply according
to the input load is smaller than that of the sliding surfaces of the main moving
elements. Therefore as shown in the embodiment, properly changing the proportion
of the oil supply to the sliding surfaces of the main moving elements and the sliding
surfaces in the cylinder head according to a compression ratio setting (or an engine
load condition) results in decreasing an unnecessary loss of oil pump
31
and in allocating just enough oil supply necessary for each sliding surface.
When the compression ratio is varied in a reciprocating engine with a variable
compression ratio mechanism, moving elements which consist of a variable compression
ratio mechanism mechanically operates. When a valve as means for controlling the
oil pressure as mentioned above consists of the moving elements of the variable
compression ratio mechanism, a structure and a control of the system are greatly
simplified. For instance as shown in the following embodiments, parts of an oil
relief passage is formed both in the moving element of the variable compression
ratio mechanism and in a housing which supports the moving element allowing a motion
of the moving element. The oil relief passage is opened or closed according to
a position of the moving element which functions as a valve.
Referring now to FIGS. 5,
6A, and
6B, there is shown a 4th
embodiment of the present invention. Compression-ratio control actuator
51
for regulating the rotation angle of control shaft
7 includes a piston rod
52 connected to control shaft
7, and a piston housing
53 for
slidably supporting piston rod
52. Piston rod
52 slides in piston
housing
53 to regulate the rotation angle of control shaft
7. In
this embodiment, piston rod
52 functions as a valve. In detail, a pair of
partial oil relief passages
55 is formed in piston housing
53 as
a part of oil relief passage
37. An in-valve oil passage
54 is formed
in piston rod
52.
As shown in FIG. 6A, piston rod
52 is positioned to communicate in-valve
oil passage
54 with partial oil relief passage
55 at a high compression
ratio setting mainly applied to a low engine load condition. In this state, oil
is relieved from main oil gallery
33 via oil relief passage
37 to
lower the oil pressure in main oil gallery
33. An unnecessary work loss
of oil pump
31 is thus avoided. On the other hand as shown in FIG. 6B, piston
rod
52 is positioned to close partial oil relief passage
55 at a
low compression ratio setting mainly applied to a high engine load condition. In
this state, oil is not relieved from main oil gallery
33 via oil relief
passage
37. Thus, the oil pressure in main oil gallery
33 is kept
high and the oil supply pressure for the lubricated elements is enough allocated.
As shown in this embodiment, piston rod
52 of compression-ratio control
actuator
51 which moves control shaft
7 functions as a valve to open
or close oil relief passage
37. Accordingly, it is not necessary to provide
an additional valve and a control unit for the valve, which leads to a simplification
of the structure and the control of the system.
Referring now to FIGS. 7A through 8B, there is shown a 5th embodiment of
the present invention. In the 5th embodiment, a journal
7a of control
shaft
7 functions as a valve to open or close oil relief passage
37
hydraulically connected to main oil gallery
33. In detail, an in-valve oil
passage
61 is formed in journal
7a of control shaft
7.
Partial oil relief passages
62 and
63 are formed in bearing caps
22 and
24 supporting journal
7a, and are open to the
abutting surface of journal
7a.
As shown in FIGS. 7A and 7B, the rotation angle of control shaft
7 is
regulated
to open oil passages
61 through
63 at a high compression ratio setting
mainly applied to a low engine load condition. In this state, a part of the oil
in main oil gallery
33 is relieved via oil relief passage
37. Accordingly,
the oil pressure in main oil gallery
33 is lowered to prevent an unnecessary
work loss of oil pump
31.
On the other hand as shown in FIGS. 8A and 8B, partial oil relief passages
62
and
63 are not communicated with each other by in-valve oil passage
61
at a low compression ratio setting mainly applied to a high engine load condition.
In this way, oil pressure in main oil gallery
33 is not lowered by oil relief
passage
37 and is kept high so that oil pressure for each lubricated element
can be allocated to provide a desirable lubrication.
As shown above in the 5th embodiment, journal
7a of control shaft
7 of the variable compression ratio mechanism functions as a valve to determine
the opening of oil relief passage
37 according to the compression ratio
setting. Accordingly, it is not necessary to provide an additional valve and a
control unit for the valve, which leads to a simplification of the structure and
the control of the system. The oil passage which supplies lubricating oil to the
sliding surfaces of journal
7a of control shaft
7 is utilized
as a part of oil relief passage
37 to simplify the structure additionally.
Referring now to FIGS. 9A through 10C, there is shown a 6th embodiment
of the present invention. In the 6th embodiment, journal
7a of control
shaft
7 functions as a valve to open or close oil relief passage
37
as in the case of the 5th embodiment. In detail, an in-valve oil passage
65
through
67 are formed in control shaft
7 as a part of oil relief
passage
37. A partial oil relief passage
64 is formed in crankshaft
bearing cap
22. In-valve oil passage
65 through
67 consists
of an axial-direction oil passage
66 extending along the axial direction
of control shaft
7, a first radial-direction oil passage
65 connecting
axial-direction oil passage
66 to the outer surface of journal
7a,
and a second radial-direction oil passage
67 connecting axial-direction
oil passage
66 to the outer surface of eccentric cam
8.
As shown in FIGS. 9A through 9C, in-valve oil passage
65 through
67
is connected to partial oil relief passage
64 at a high compression ratio
setting (or at a rotation angle of the control shaft corresponding to the high
compression ratio) mainly applied to a low load range. In this state, lubricating
oil is supplied to the outer surface of eccentric cam
8 from main oil gallery
33 via oil relief passage
37. After lubricating the sliding surface
of eccentric cam
8, the lubricating oil finally returns to oil pan
32.
Thus, the oil pressure in main oil gallery
33 is lowered due to this oil
relief from main oil gallery
33 via oil relief passage
37. Accordingly,
an unnecessary work loss of oil pump
31 is avoided to improve fuel efficiency.
On the other hand shown in FIGS. 10A through 10C, in-valve oil passage
65
through
67 is not connected to partial oil relief passage
64, that
is, oil relief passage
37 is closed at a low compression ratio setting mainly
applied to a high engine load condition. In this state, oil is not relieved from
main oil gallery
33 via oil relief passage
37. The oil pressure in
main oil gallery
33 is kept high so that oil is enough supplied to each
lubricated element.
As shown above in the 6th embodiment, control shaft
7 and crankshaft bearing
cap
22 of the variable compression ratio mechanism function as a valve to
determine the opening of oil relief passage
37 according to the compression
ratio setting. Accordingly, it is not necessary to provide an additional valve
and a control unit for the valve, which leads to a simplification of the structure
and the control of the system. The oil passage which supplies lubricating oil to
the sliding surfaces of journal
7a and eccentric cam
8 of
control shaft
7 are utilized as a part of oil relief passage
37 to
simplify the structure additionally.
In addition, when partial oil relief passage
63 is formed in control-shaft
bearing cap
24 as in the case of the 5th embodiment, it is possible to regulate
the oil pressure and the oil flow more precisely by two stages in combination with
the aforementioned oil relief from eccentric cam
8.
Referring now to FIGS. 11A,
11B and
12, there is shown a
7th embodiment of the present invention. The pressure of the oil discharged from
oil pump
31 driven by crankshaft
1 is low at a low engine speed,
and high at a high engine speed. Accordingly in general, an orifice is provided
in the oil passage between the main oil gallery and the cylinder head oil gallery
to lower oil pressure in the cylinder head oil gallery relative to that in the
main oil gallery in the high engine speed range. In this way, when the engine speed
rises high, the oil pressure in the cylinder head oil gallery is prevented from
excessively rising to oversupply oil to the valve train. On the other hand, it
is necessary to prevent a shortage of the oil flow supplied to the cylinder head
oil gallery in the low engine speed range. Accordingly, the capacity of the oil
pump is enlarged to raise the oil pressure in main oil gallery, for allocating
the oil pressure in the cylinder head oil gallery. In this state, the oil pressure
in the main oil gallery excessively rises in the high engine speed range. It is
necessary to keep the oil pressure constant by relieving a part of the oil. Therefore
a work loss of the oil pump is increased to lower fuel efficiency. Necessary oil
flow for lubricated elements such as a valve train in the cylinder head varies
according not to the engine rotation speed, but mainly to the engine load. While
the oil pressure in the cylinder head oil gallery is not necessary to be greatly
varied according to the engine rotation speed, the oil pressure in the main oil
gallery is necessary to be raised to supply larger oil under a higher speed and
higher engine load condition. In this embodiment, the oil pressure variation in
the cylinder head oil gallery corresponding to the compression ratio variation
is made smaller than that in the main oil gallery. In this way, it is possible
to supply oil to the cylinder head oil gallery without an unnecessary work loss
of the oil pump. The capacity of the oil pump can be decreased to improve fuel efficiency.
Specifically, valve
38 is provided in oil relief passage
37
connected to main oil gallery
33, to regulate the opening of oil relief
passage
37. A cylinder head sub oil supply passage
71 is provided
for connecting a downstream oil passage
37b of oil relief passage
37 to cylinder head oil gallery
35. The oil flow resistance of cylinder
head sub oil supply passage
71 is set to be smaller than that of cylinder
head main oil supply passage
36 which is directly connected to main oil
gallery
33 and to cylinder head oil gallery
35. In this state, the
oil pressure fall between main oil gallery
33 and cylinder head oil gallery
35 via cylinder head sub oil supply passage
71 is smaller than via
cylinder head main oil supply passage
36, so that the difference between
the oil pressure in cylinder head oil gallery
35 and the oil pressure in
main oil gallery
33 is small.
As shown in FIG. 11A, oil relief passage
37 is opened by valve
38
at a high compression ratio setting applied to a low engine speed and low engine
load condition. Accordingly as shown in FIG. 12, the oil pressure in main oil gallery
33 is lowered to avoid an unnecessary work loss of oil pump
31. In
addition, the lubricating oil is supplied to cylinder head oil gallery
35
mainly via cylinder head sub oil supply passage
71 with a small flow resistance,
to reduce relatively the oil pressure fall in cylinder head oil gallery
35,
so that an inadequate lubrication is prevented in the lubricated elements in the
cylinder head.
As shown in FIG. 11B, oil relief passage
37 is closed by valve
38
at a low compression ratio setting applied to a middle-high engine speed and high
engine load condition. In this way, the lubricating oil is not relieved from main
oil gallery
33 via oil relief passage
37. As shown in FIG. 12, the
oil pressure in main oil gallery
33 is kept high to supply the lubricating
oil for each lubricated element. The lubricated oil is supplied to cylinder head
oil gallery
35 from main oil gallery
33 only via cylinder head main
oil supply passage
36. Thus, the oil pressure in the cylinder head is not
excessively raised, so that the lubricating oil is properly supplied to the lubricated
elements in the cylinder head.
Referring now to FIGS. 13A and 13B, there is shown an 8th embodiment. In
this embodiment, journal
7a of control shaft
7 functions as
a valve as in the case of the 5th embodiment, which is the only difference from
the 7th embodiment. Specifically, partial oil relief passage
64 is formed
as a part of oil relief passage
37 in journal
7a of control
shaft
7. When control shaft
7 is rotated to vary the compression
ratio setting, oil relief passage
37 is opened or closed accordingly. In
the 8th embodiment, similar effects as in the case of the 5th embodiment are provided
in addition to similar effects as in the case of the 7th embodiment.
Referring now to FIGS. 14A and 14B, there is shown a 9th embodiment. In
this embodiment, cylinder head sub oil supply passage
71 is connected to
a valve
72 provided in oil relief passage
37. Valve
72 opens
or closes oil relief passage
37 connected to main oil gallery
33
and also has a function of opening or closing cylinder head sub oil supply passage
71. Two in-valve oil passages which have different cross-sectional areas
and different oil flow resistances are provided in valve
72. One is a thick
oil passage
73 which has a large cross-sectional area and a small oil flow
resistance, and the other is a thin oil passage
73 which has a small cross-sectional
area and a large oil flow resistance. Valve
72 may be replaced by journal
7a of control shaft
7 as in the case of the 7th embodiment.
As shown in FIG. 14A, cylinder head sub oil supply passage
71 is opened
in addition to oil relief passage
37 by valve
72 at a high compression
ratio setting applied to a low engine load condition. Oil relief passage
37
is connected to cylinder head sub oil supply passage
71 only via thick oil
passage
73 with a small oil flow resistance. Accordingly, the oil pressure
fall in cylinder head oil gallery
35 relative to that in main oil gallery
33 is reduced.
As shown in FIG. 14B, oil relief passage
37 is closed and cylinder head
sub oil supply passage
71 is opened by valve
72 at a low compression
ratio setting applied to a high engine load condition. Oil relief passage
37
is connected to cylinder head sub oil supply passage
71 via both thick oil
passage
73 and thin oil passage
73 in series. Accordingly, the oil
pressure fall in cylinder head oil gallery
35 relative to the oil pressure
in main oil gallery
33 is smaller than in the case of connecting only via
thick oil passage
73.
In the aforementioned embodiment, similar effects as in the case of the 8th embodiment
is provided. In addition, the oil supply and the oil pressure for the cylinder
head gallery are regulated more specifically.
The entire contents of Japanese Patent Application No. 2003-45709 (filed Feb.
24, 2003) are incorporated herein by reference.
While the foregoing is a description of the preferred embodiments carried out
the invention, it will be understood that the invention is not limited to the particular
embodiments shown and described herein, but that various changes and modifications
may be made without departing from the scope or spirit of this invention as defined
by the following claims.
*
