Information
-
Patent Grant
-
6321717
-
Patent Number
6,321,717
-
Date Filed
Tuesday, February 15, 200024 years ago
-
Date Issued
Tuesday, November 27, 200122 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Marshall, O'Toole, Gerstein, Murray & Borun
-
CPC
-
US Classifications
Field of Search
US
- 123 9015
- 123 321
- 123 322
-
International Classifications
-
Abstract
A method of compression braking is provided for use in an internal combustion engine having a plurality of combustion chambers that share a common exhaust manifold, such as, for example, a six-cylinder engine. The method comprises the steps of moving each exhaust valve to an open position at a first time corresponding to approximately the beginning of the power portion of the cycle of the combustion chamber associated with the exhaust valve and moving each exhaust valve to the open position at a second time corresponding to approximately the end of the intake portion of the cycle of the combustion chamber associated with the exhaust valve.
Description
TECHNICAL FIELD
The present invention relates generally to engine retarding methods and, more particularly, to a method for engine compression braking.
BACKGROUND ART
Engine brakes or retarders are used to assist and supplement wheel brakes in slowing heavy vehicles, such as tractor-trailers. Engine brakes are desirable because they help alleviate wheel brake overheating. As vehicle design and technology have advanced, the hauling capacity of tractor-trailers has increased, while at the same time rolling resistance and wind resistance have decreased. Thus, there is a need for advanced engine braking systems in today's heavy vehicles.
Known engine compression brakes convert an internal combustion engine from a power generating unit into a power consuming air compressor.
U.S. Pat. No. 3,220,392 issued to Cummins on Nov. 30, 1965, discloses an engine braking system in which an exhaust valve located in a cylinder is opened when the piston in the cylinder nears the top dead center (TDC) position on the compression stroke. An actuator includes a master piston, driven by a cam and pushrod, which in turn drives a slave piston to open the exhaust valve during engine braking. The braking that can be accomplished by the Cummins device is limited because the timing and duration of the opening of the exhaust valve is dictated by the geometry of the cam which drives the master piston and hence these parameters cannot be independently controlled.
In an effort to maximize braking power, engine braking systems have been developed that use both the compression stroke and what would normally be the exhaust stroke of the engine in a four-cycle powering mode to produce two compression release events per engine cycle. Such systems are commonly referred to as two-cycle retarders or two-cycle engine brakes and are disclosed, for example, in U.S. Pat. No. 4,592,319 issued to Meistrick on Jun. 3, 1986, and in U.S. Pat. No. 4,664,070 issued to Meistrick et al. on May 12, 1987. The Meistrick et al. '070 patent also discloses an electronically controlled hydro-mechanical overhead which operates the exhaust and intake valves and is substituted in place of the usual rocker arm mechanism for valve operation.
A method of two-cycle exhaust braking using a butterfly valve in an exhaust pipe or manifold in combination with opening an exhaust valve at both the beginning and the end of the compression stroke is disclosed in U.S. Pat. No. 4,981,119 issued to Neitz et al. on Jan. 1, 1991.
In a further effort to maximize braking power, systems have been developed which open the exhaust valves of each cylinder during braking for at least part of the downstroke of the associated piston. In this manner, pressure released from a first cylinder into the exhaust manifold is used to boost the pressure of a second cylinder. Thereafter, the pressure in the second cylinder is further increased during the upstroke of the associated piston so that retarding forces are similarly increased. This mode of operation is termed “back-filling” and systems employing this mode of operation are disclosed in the Meistrick '319 patent and in U.S. Pat. No. 4,741,307 issued to Meneely on May 3, 1988.
U.S. Pat. No. 5,526,784 issued to Hakkenberg et al. on Jun. 18, 1996, and assigned to the assignee of the present invention, discloses a system and method for compression braking of a multi-cylinder engine that uses simultaneous opening of all exhaust valves of the engine. The system and method of the Hakkenberg et al. '784 patent, when implemented in a multi-cylinder engine such as, for example, a 6-cylinder engine, provides higher cylinder pressures in cylinders still in the early stages of a compression stroke when the exhaust valves are opened, thereby allowing the cylinder pressure to build up and increase the braking function.
U.S. Pat. No. 5,724,939, issued to Faletti et al. on Mar. 10, 1998, and assigned to the assignee of the present invention, discloses two-cycle and four-cycle methods of compression braking for an internal combustion engine. In accordance with the method disclosed in the Faletti et al. '939 patent, exhaust valves are opened in cylinders wherein associated pistons are near TDC and substantially simultaneously, exhaust valves are opened in cylinders wherein associated pistons are nominally past bottom dead center (BDC). This provides an advantageous braking power increase due to back-filling of the cylinders wherein associated pistons are nominally past BDC.
DISCLOSURE OF THE INVENTION
Applicant has discovered that a desirable method of back-filling for an engine braking system is to open each exhaust valve in each cylinder at a first time at approximately the beginning of the power stroke and at a second time at approximately the end of the intake stroke. This method provides additional braking power resulting from back-filling of each cylinder, and simulations indicate that an increase of braking power of approximately 20% is provided by the method of the present invention, as compared to braking without back-filling.
In accordance with one aspect of the present invention, a method of compression braking is provided for use in an internal combustion engine having a plurality of combustion chambers. Each combustion chamber operates in a cycle comprising intake, compression, power and exhaust portions, and each combustion chamber is in flow communication with an exhaust valve movable between an open position and a closed position for selectively placing each combustion chamber in flow communication with a common exhaust manifold. The method comprises the steps of moving each exhaust valve to the open position at a first time corresponding to approximately the beginning of the power portion of the cycle of the combustion chamber associated with the exhaust valve and moving each exhaust valve to the open position at a second time corresponding to approximately the end of the intake portion of the cycle of the combustion chamber associated with the exhaust valve.
In accordance with another aspect of the present invention, each portion of the cycle of the internal combustion engine comprises 180 degrees of crank angle rotation and the step of moving each exhaust valve to the open position at the first time includes a step of holding the exhaust valve open from approximately the beginning of the power portion of the cycle of the combustion chamber associated with the exhaust valve to a crank angle of about 80 degrees after the beginning of the power portion of the cycle of the combustion chamber associated with the exhaust valve.
In accordance with yet another aspect of the present invention, the step of moving each exhaust valve to the open position at the second time includes a step of holding the exhaust valve open from a crank angle of about 120 degrees after the beginning of the intake portion of the cycle of the combustion chamber associated with the exhaust valve to a crank angle of about 30 degrees after the beginning of the compression portion of the cycle of the combustion chamber associated with the exhaust valve.
Other features and advantages are inherent in the method claimed and disclosed or will become apparent to those skilled in the art from the following detailed description in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a block diagram of an exhaust valve actuation system capable of carrying out the method of the present invention;
FIG. 2
is a diagrammatic partial sectional view of the valve actuation system of
FIG. 1
showing the exhaust valves in a closed position;
FIG. 3
is a view similar to
FIG. 2
, showing the exhaust valves in an open position;
FIG. 4
is an exaggerated enlarged detail view encircled by
4
—
4
of
FIG. 3
;
FIG. 5
is a block diagram of an exhaust valve actuation system for use with a six cylinder engine capable of carrying out the method of the present invention;
FIG. 6
is a table showing the timing of exhaust valve opening for each cylinder of the system of
FIG. 5
during a braking mode of operation in accordance with the method of the present invention; and
FIG. 7
is a plot depicting simulation results illustrating the braking mode of operation in accordance with the present invention, and showing combustion chamber pressure, combustion chamber temperature, valve events and exhaust port pressure as a function of crank angle (a fueling graph is indicated by the solid line, an exhaust back fill is indicated by the section line symbol and the baseline is indicated by the hidden line symbol).
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will now be described with reference to
FIGS. 1-5
that show an apparatus capable of carrying out the method of the present invention, which comprises an exhaust valve actuation system
10
A, associated with a cylinder
11
A of a six-cylinder, four-cycle internal combustion engine
12
. For clarity, only the valve actuation system
10
A, associated with cylinder
11
A is shown in
FIGS. 1-3
, as the components and operation thereof are identical to those of valve actuation systems
10
B,
10
C,
10
D,
10
E and
10
F that are associated with cylinders
11
B,
11
C,
11
D,
11
E and
11
F, respectively. The engine
12
has a cylinder head
14
and one or more engine exhaust valve(s)
16
associated with each cylinder and reciprocally disposed within the cylinder head
14
. The exhaust valves
16
are only partially shown in
FIGS. 2 and 3
and are movable between a first or closed position, shown in
FIG. 2
, and a second or open position, shown in FIG.
3
. The valves
16
are biased toward the first position by any suitable means, such as by helical compression springs
18
. Each valve
16
, when open, places an associated engine cylinder
11
A,
11
B,
11
C,
11
D,
11
E or
11
F in fluid communication with a common exhaust manifold
13
via an exhaust port
15
.
An actuator head
20
has an axially extending bore
22
therethrough of varying diameters. Additionally, the actuator head
20
has a rail passage
24
A therein which may be selectively placed in fluid communication with either a low pressure fluid source
26
or a high pressure fluid source
28
, both of which are shown in FIG.
1
. The pressure of the fluid from the high pressure fluid source
26
is greater than 1500 psi, and more preferably, greater than 3000 psi. The pressure of the fluid from the low pressure fluid source is preferably less than 400 psi, and more preferably, less than 200 psi.
A cylindrical body
30
(
FIG. 2
) is sealingly fitted within the bore
22
by a plurality of O-rings
32
and has an axially extending bore
36
.
A bridge member
46
is disposed within a recess
48
in the actuator head
20
adjacent to the body
30
. The bridge
46
has a bore
50
of predetermined length which is coaxially aligned with the bore
36
in the body
30
.
A plunger
54
includes a plunger surface
58
and includes an end portion
60
secured within the bore
50
of the bridge
46
. A second end
62
of the plunger
54
is slidably disposed within the bore
36
of the body
30
. The second end
62
of the plunger
54
has a frusto-conical shape
64
which diverges from the plunger surface
58
at a predetermined angle which can be seen in more detail in FIG.
4
. The plunger
54
may be integrally formed with or separately connected to the bridge
46
, such as by press fitting. The plunger
54
is operatively associated with the valves
16
and is movable between a first position and a second position. The movement of the plunger
54
toward the second position moves the valves
16
to the open position. It should be understood that the plunger
54
may be used to directly actuate the exhaust valves
16
without the use of a bridge
46
. In this manner, the plunger
54
would be integrally formed with or separately positioned adjacent the exhaust valves
16
such that the valves
16
are engaged when the plunger
54
is moved to the second position.
A means
68
for communicating low pressure fluid into the bridge
46
is provided. The communicating means
68
includes a pair of orifices
69
disposed within the bridge
46
and a pair of connecting passages
70
extending through the orifices
69
and the bridge
46
and into the plunger
54
. A longitudinal bore
74
extends through a portion of the plunger
54
and is in fluid communication with the connecting passages
70
within the bridge
46
. An orifice
80
extends outwardly from the longitudinal bore
74
. A cross bore
84
extends through the body
30
at a lower end
90
. The cross bore
84
is connected to a lower annular cavity
94
defined between the body
30
and the actuator head
20
. The lower annular cavity
94
is in communication with the low pressure fluid source
26
through a passage
96
A in the actuator head
20
. As discussed in further detail below, the cross bore
84
has a predetermined position relative to the orifice
80
such that the orifice
80
is in fluid communication with the low pressure fluid source
26
through the passage
96
A when the plunger
54
begins to move from the first position to the second position.
A pair of hydraulic lash adjusters
100
,
102
are secured within a pair of large bores
106
,
107
, respectively, in the bridge
46
by any suitable means, such as a pair of retaining rings
108
,
110
. The lash adjusters
100
,
102
are in fluid communication with the orifices
69
and the connecting passages
70
and are adjacent the exhaust valves
16
. However, it should be understood that the lash adjusters
100
,
102
may or may not have the orifices
69
dependent upon the internal design used.
A plug
120
is connected to the actuator head
20
and is sealingly fitted into the bore
50
at an upper end
124
of the body
30
in any suitable manner, such as by threading or press fitting and/or by retainer plates
125
secured to the actuator head
20
by bolts
127
. A cavity
130
forming a part of the bore
50
is defined between the plug
120
and the plunger surface
58
. It should be understood that although a plug
120
is shown fitted within the bore
50
to define the plunger cavity
130
, the cylinder head
14
may be sealingly fitted against the bore
50
. Therefore, the plunger cavity
130
would be defined between the cylinder head
14
and the plunger surface
58
.
A first means
140
for selectively communicating fluid from the high pressure fluid source
28
into the plunger cavity
130
is provided for urging the plunger
54
toward the second position. The first communicating means
140
includes means
144
defining a primary flow path
148
between the high pressure fluid source
28
and the plunger cavity
130
during initial movement toward the second position. The means
144
further defines a secondary flow path
152
between the high pressure fluid source
28
and the plunger cavity
130
during terminal movement toward the second position.
A control valve, preferably a spool valve
156
A, communicates fluid through the high pressure rail passage
24
A and into the primary and secondary flow paths
148
,
152
. The spool valve
156
A is biased to a first position P
1
by a pair of helical compression springs (not shown) and moved against the force of the springs (not shown) to a second position P
2
by an actuator
158
A. The actuator
158
A may be of any suitable type, however, in this embodiment the actuator
158
A is a piezoelectric motor. The piezoelectric motor
158
A is driven by a control unit
159
which has a conventional on/off voltage pattern.
The primary flow path
148
of the first communicating means
140
includes an annular chamber
160
defined between the body
30
and the actuator head
20
. A main port
164
is defined within the body
30
in fluid communication with the annular chamber
160
and has a predetermined diameter. An annular cavity
168
is defined between the plunger
54
and the body
30
and has a predetermined length and a predetermined position relative to the main port
164
. The annular cavity
168
is in fluid communication with the main port
164
during a portion of the plunger
54
movement between the first and second positions. A passageway
170
is disposed within the plunger
54
and partially traverses the annular cavity
168
for fluid communication therewith.
A first check valve
174
is seated within a bore
176
in the plunger
54
and has an orifice
178
therein in fluid communication with the passageway
170
. The first check valve
174
has an open position and a closed position and the orifice
178
has a predetermined diameter.
A stop
180
is seated within another bore
182
in the plunger
54
and is disposed a predetermined distance from the first check valve
174
. The stop
180
has an axially extending bore
184
for fluidly communicating the orifice
178
with the plunger cavity
130
and a relieved outside diameter. A return spring
183
is disposed within the first check valve between the valve
174
and the stop
180
.
The secondary flow path
152
of the first communicating means
140
includes a restricted port
190
which has a diameter less than the diameter of the main port
164
. The restricted port
190
fluidly connects the annular chamber
160
to the annular cavity
168
during a portion of the plunger
54
movement between the first and second positions.
A second means
200
for selectively communicating fluid exhausted from the plunger cavity
130
to the low pressure fluid source
26
in response to the helical springs
18
is provided for urging the plunger
54
toward the first position. The second communicating means
200
includes means
204
defining a primary flow path
208
between the plunger cavity
130
and the low pressure fluid source
26
during initial movement from the second position toward the first position. The means
144
further defines a secondary flow path
210
between the plunger cavity
130
and the low pressure fluid source
26
during terminal movement from the second position toward the first position. The spool valve
156
A selectively communicates fluid through the primary and secondary flow path
208
,
210
and into the low pressure fluid source
26
through the rail passage
24
A.
The primary flow path
208
of the second communicating means
200
includes a second check valve
214
seated within a bore
216
in the body
30
with a portion of the second check valve
214
extending into the annular chamber
160
. The second check valve
214
has an open and a closed position. A small conical shaped return spring (not shown) is disposed within the second check valve
214
. An outlet passage
218
is defined within the body
30
between the second check valve
214
and the plunger
54
. The outlet passage
218
provides fluid communication between the plunger cavity
130
and the annular chamber
160
when the second check valve
214
is in the open position during a portion of the plunger
54
movement between the second and the first position.
The secondary flow path
210
of the second communicating means
200
places the orifice
178
in fluid communication with the low pressure source
26
during a portion of the plunger
54
movement between the second and first positions.
A first hydraulic means
230
is provided for reducing the plunger
54
velocity as the valves
16
approach the open position. The first hydraulic means
230
restricts fluid communication to the annular cavity
168
from the high pressure fluid source
28
through the main port
164
during a portion of the plunger
54
movement between the first and second positions and blocks fluid communication to the annular cavity
168
from the high pressure fluid source
28
through the main port
164
during a separate portion of the plunger
54
movement between the first and second positions. A second hydraulic means
240
is provided for reducing the plunger
54
velocity as the valves
16
approach the closed position. The second hydraulic means
240
includes the frusto-conical shaped second end
62
of the plunger
54
for restricting fluid communication to the low pressure fluid source
26
from the plunger cavity
168
through the outlet passage
218
and for blocking fluid communication to the low pressure fluid source
26
from the plunger cavity
168
through the outlet passage
218
.
INDUSTRIAL APPLICABILITY
For increased understanding, the following sequence begins with the plunger
54
in the first position, and therefore, the valve in the closed (or seated) position. Referring to
FIG. 1
, at the beginning of the valve opening sequence, voltage from the control unit
159
is applied to the piezoelectric motor
158
A which, in turn, drives the spool valve
156
A in a known manner from the first position P
1
to the second position P
2
. Movement of the spool valve
156
A from the first position P
1
to the second position P
2
closes off communication between the low pressure fluid source
26
and the plunger cavity
130
and opens communication between the high pressure fluid source
28
and the plunger cavity
130
.
Referring specifically to
FIG. 2
, during the initial portion of the plunger
54
movement from the first position to the second position, high pressure fluid from the high pressure fluid source
28
is communicated to the plunger cavity
130
through the primary flow path
148
. The high pressure fluid unseats the first check valve
174
, allowing the majority of high pressure fluid to rapidly enter the plunger cavity
130
around the first check valve
174
through the relieved outside diameter of the stop
180
.
As the plunger cavity
130
fills with high pressure fluid, the plunger
54
moves rapidly downward opening the valves
16
against the force of the springs
18
. As the plunger
54
moves downward, the position of the annular cavity
168
in relation to the main port
164
constantly changes. The downward motion of the annular cavity
168
allows fluid connection between the annular cavity
168
and the restricted port
190
, thereby allowing high pressure fluid to enter the plunger cavity
130
through both the primary and secondary flow paths
148
,
152
.
As seen in
FIG. 3
, when the annular cavity
168
moves past the main port
164
in the terminal portion of the plunger movement fluid communication is restricted and eventually blocked by the outer periphery of the plunger
54
so that all fluid communication between the high pressure fluid source
28
and the plunger cavity
130
is through the restricted port
190
. Since the diameter of the restricted port
190
is smaller than the main port
174
, downward motion of the plunger
54
is slowed, thereby reducing the velocity of the valve
16
as it reaches a fully open position.
As the annular cavity
168
moves past the restricted port
190
, fluid communication is restricted and eventually blocked by the outer periphery of the plunger
54
which allows the plunger
54
to hold the valve
16
at its maximum lift position. As leakage occurs within the system, the plunger
54
will move up and slightly re-open the restricted port
190
and, therefore, recharge the plunger cavity
130
causing the plunger
54
to move back down. The valve
16
open position is then stabilized around the maximum lift position by the small movements of the plunger
54
opening and closing the restricted port
190
. During this time, the return spring
183
on the first check valve
174
returns the valve
174
to its seat. It should be understood that the restricted port
190
may not be necessary dependent upon specific designs which would accomplish rapid stopping of the plunger
54
at maximum lift, such as utilizing a plunger
54
with a larger diameter or higher forces on the springs
18
.
Referring again to
FIG. 1
, to begin the valve closing sequence, voltage from the control unit is removed from the piezoelectric motor
158
A which, in turn, allows the spool valve
156
A to return in a known manner from the second position P
2
to the first position P
1
. Movement of the spool valve
156
A from the second position P
2
to the first position P
1
closes off communication between the high pressure fluid source
28
and the plunger cavity
130
and opens communication between the low pressure fluid source
26
and the plunger cavity
130
. At this stage, the potential energy of the springs
18
is turned into kinetic energy in the upwardly moving exhaust valve
16
.
Referring more specifically to
FIG. 3
, the high pressure fluid within the plunger cavity
130
unseats the second check valve
214
since low pressure fluid is now within the annular chamber
160
. The unseating of the second check valve
214
allows the majority of fluid within the plunger cavity
130
to rapidly return to the low pressure fluid source
26
through the primary flow path
208
. A portion of the high pressure fluid within the plunger cavity
130
is returned to the low pressure fluid source
26
through the secondary flow path as the orifice
178
fluidly connects with the annular chamber
160
during the terminal plunger
54
movement from the second position to the first position.
As the second end
62
of the plunger
54
having the frusto-conical shape
64
moves past the outlet passage
218
, fluid communication to the low pressure fluid source
26
is gradually restricted and eventually blocked, reducing the velocity of the valve
16
as it reaches its closed or seated position. Once the outlet passage
218
is completely blocked, fluid communication from the plunger cavity
130
to the low pressure fluid source
26
is only through the orifice
178
, as can be seen in FIG.
2
. The fluid communication occurs only through the orifice
178
because the first check valve
174
is seated, allowing substantially no additional fluid communication around the first check valve
174
. Therefore, final seating velocity is more finely controlled by the size of the small diameter of the orifice
178
.
Additionally, when the spool valve
156
A is in the P
1
position and connected with the low pressure fluid source
26
, fluid is communicated to the hydraulic adjusters
100
,
102
through the orifices
69
. The orifices
69
communicate with the passages
70
to control the maximum pressure allowed for the lash adjusters
100
,
102
. However, when the spool valve moves into the P
2
position, the plunger
54
is moved downwards and the orifice
80
moves past the cross bore
84
restricting and eventually blocking fluid communication from the low pressure fluid source
26
to the adjusters
100
,
102
.
Now referring to
FIGS. 5 through 7
, when braking is desired, the engine is converted to a braking mode in which the normal intake and exhaust valve events are preferably disabled, or alternatively, may continue to occur (i.e., if a camactuated valve opening mechanism is used for normal intake and exhaust valve events), and in which each exhaust valve
16
is opened by about 2 mm at a first time when the cylinder
11
A,
11
B,
11
C,
11
D,
11
E or
11
F associated with the exhaust valve
16
is at the beginning of the power portion of the cycle of operation (i.e., when the associated piston (not shown) is at TDC, depicted in
FIGS. 6 and 7
for cylinder
1
as a crank angle of zero degrees), and is preferably held open for about 80 degrees of crank angle. As a result, the exhaust port pressure in the exhaust manifold
13
is elevated due to a pressure pulse
242
(
FIG. 7
) caused by the opening of each exhaust valve
16
at the beginning of the power portion of the cycle of operation.
In addition, each exhaust valve
16
is opened by about 2 mm at a second time when the cylinder
11
A,
11
B,
11
C,
11
D,
11
E or
11
F associated with the exhaust valve
16
is at the end of the intake portion of the cycle of operation (i.e., when the associated piston (not shown) is at about 60 degrees before BDC, depicted in
FIGS. 6 and 7
for cylinder
1
as a crank angle of 480 degrees), and is again preferably held open for about 80 degrees of crank angle.
The timing and duration of the opening of each exhaust valve is dictated by the control unit
159
that sends a signal to each piezoelectric motor
158
A,
158
B,
158
C,
158
D,
158
E or
158
F (associated with the appropriate cylinder
11
A through
11
F, respectively). Each piezoelectric motor
158
A-E in turn, drives the corresponding spool valve
156
A,
156
B,
156
C,
156
D,
156
E or
156
F from the first position P
1
to the second position P
2
, to in turn operate the corresponding valve actuation system
10
A,
10
B,
10
C,
10
D,
10
E or
10
F as discussed above with regard to FIG.
1
.
As seen in
FIG. 6
, during the braking mode in accordance with the method of the present invention, the first and second opening events coincide with one another as follows: the cylinder
1
first opening event coincides with the cylinder
3
second opening event; the cylinder
5
first opening event coincides with the cylinder
6
second opening event; the cylinder
3
first opening event coincides with the cylinder
2
second opening event; the cylinder
6
first opening event coincides with the cylinder
4
second opening event; the cylinder
2
first opening event coincides with the cylinder
1
second opening event; and the cylinder
4
first opening event coincides with the cylinder
5
second opening event. Thus, for each of the foregoing pairs of cylinders, the pressure in the cylinder undergoing the second opening event will increase as a result of the pressure pulse
242
provided by the cylinder undergoing the first opening event.
Numerous modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure may be varied substantially without departing from the spirit of the invention, and the exclusive use of all modifications which come within the scope of the appended claims is reserved. For example, the foregoing description was primarily directed to an apparatus capable of carrying out a method in accordance with the present invention utilizing an electronically controlled hydraulic valve actuation system. However, as those skilled in the art will recognize, the method in accordance with the present invention can be practiced with any suitable apparatus.
Claims
- 1. A method of compression braking of an internal combustion engine, the engine having a plurality of combustion chambers, each combustion chamber operating in a cycle comprising intake, compression, power and exhaust portions, each combustion chamber being in flow communication with an exhaust valve movable between an open position and a closed position for selectively placing each combustion chamber in flow communication with a common exhaust manifold, the method comprising the steps of:moving each exhaust valve to the open position at a first time corresponding to approximately the beginning of the power portion of the cycle of the combustion chamber associated with the exhaust valve; and moving each exhaust valve to the open position at a second time corresponding to approximately the end of the intake portion of the cycle of the combustion chamber associated with the exhaust valve; wherein each portion of the cycle of the internal combustion engine comprises 180 degrees of crank angle rotation and wherein the step of moving each exhaust valve to the open position at the first time includes a step of holding the exhaust valve open from approximately the beginning of the power portion of the cycle of the combustion chamber associated with the exhaust valve to a crank angle of about 80 degrees after the beginning of the power portion of the cycle of the combustion chamber associated with the exhaust valve.
- 2. The method of claim 1, wherein the step of moving each exhaust valve to the open position at the second time includes a step of holding the exhaust valve open from a crank angle of about 120 degrees after the beginning of the intake portion of the cycle of the combustion chamber associated with the exhaust valve to a crank angle of about 30 degrees after the beginning of the compression portion of the cycle of the combustion chamber associated with the exhaust valve.
- 3. A method of compression braking of an internal combustion engine, the engine having a plurality of combustion chambers, each combustion chamber operating in a cycle comprising intake, compression, power and exhaust portions, each combustion chamber being in flow communication with an exhaust valve movable between an open position and a closed position for selectively placing each combustion chamber in flow communication with a common exhaust manifold, the method comprising the steps of:moving each exhaust valve to the open position at a first time corresponding to approximately the beginning of the power portion of the cycle of the combustion chamber associated with the exhaust valve; and moving each exhaust valve to the open position at a second time corresponding to approximately the end of the intake portion of the cycle of the combustion chamber associated with the exhaust valve; wherein each portion of the cycle of the internal combustion engine comprises 180 degrees of crank angle rotation and wherein the step of moving each exhaust valve to the open position at the second time includes a step of holding the exhaust valve open from a crank angle of about 120 degrees after the beginning of the intake portion of the cycle of the combustion chamber associated with the exhaust valve to a crank angle of about 30 degrees after the beginning of the compression portion of the cycle of the combustion chamber associated with the exhaust valve.
US Referenced Citations (13)
Foreign Referenced Citations (1)
Number |
Date |
Country |
63-272929 |
Nov 1988 |
JP |