Information
-
Patent Grant
-
6644271
-
Patent Number
6,644,271
-
Date Filed
Wednesday, October 30, 200221 years ago
-
Date Issued
Tuesday, November 11, 200320 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Finnegan, Henderson, Farabow, Garrett & Dunner
-
CPC
-
US Classifications
Field of Search
US
- 123 321
- 123 322
- 123 9012
- 123 9013
-
International Classifications
-
Abstract
An engine braking system for a multi-cylinder engine includes a supply of low pressure fluid and an engine fluid sump. A plurality of valve actuators are each configured to be alternatively fluidly coupled to the supply of low pressure fluid and the engine fluid sump. Each valve actuator is operably coupled to at least one exhaust valve for a respective cylinder. The system also includes a braking control valve operably coupled to two of the valve actuators. The braking control valve is movable between a first position at which the two valve actuators are fluidly coupled to the engine fluid sump and blocked from the supply of low pressure fluid and a second position at which the two valve actuators are fluidly coupled to the supply of low pressure fluid and blocked from the engine fluid sump.
Description
TECHNICAL FIELD
This invention relates generally to engine braking systems and methods and, more particularly, to a control valve for engine braking systems and methods.
BACKGROUND
Engine brakes, or engine retarders, are sometimes used to assist and supplement wheel brakes in slowing heavy vehicles, such as dump trucks, construction vehicles, tractor-trailers, and the like. Engine compression brakes convert an internal combustion engine from a power generating unit into a power consuming air compressor. Compressed air from the compression stroke of the engine is released through the cylinder exhaust valve when the piston in the cylinder nears the top-dead-center position. In conjunction with the increasingly widespread use of electronic controls in engine systems, engine braking systems have been developed which are electronically controlled by a central engine control unit.
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 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 actuator is controlled by a hydraulic circuit requiring at least one control valve and at least one solenoid valve for each cylinder.
Thus, the Cummins device requires manufacture, assembly, warranty, and maintenance of these numerous valves. Each of these concerns comes at an expense to the manufacturer and the user. Furthermore, the numerous valves and associated plumbing occupy space in the engine compartment, thus increasing the size of the engine, the weight of the engine, and the gross weight of the associated vehicle.
The present invention provides an economical and reliable engine braking system that avoids one or more of the aforesaid shortcomings in the prior art.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, an engine braking system for a multi-cylinder engine includes a supply of low pressure fluid and an engine fluid sump. A plurality of valve actuators are each configured to be alternatively fluidly coupled to the supply of low pressure fluid and the engine fluid sump. Each valve actuator is operably coupled to at least one exhaust valve for a respective cylinder. The system also includes a braking control valve operably coupled to two of the valve actuators. The braking control valve is movable between a first position at which the two valve actuators are fluidly coupled to the engine fluid sump and blocked from the supply of low pressure fluid and a second position at which the two valve actuators are fluidly coupled to the supply of low pressure fluid and blocked from the engine fluid sump.
In accordance with another aspect of the invention, an engine braking method for a multi-cylinder engine is provided. Compressed air from the compression stroke of a cylinder is used for engine braking and the compressed air is released through a cylinder exhaust valve near a piston top-dead-center position. The method includes supplying fluid from a supply of low pressure fluid to a braking control valve and selectively controlling movement of the braking control valve between a first position at which two valve actuators are fluidly coupled to an engine fluid sump and blocked from the supply of low pressure fluid and a second position at which the two valve actuators are fluidly coupled to the supply of low pressure fluid and blocked from the engine fluid sump. Each of the valve actuators controls an exhaust valve of a different cylinder.
In accordance with yet another aspect of the invention, an engine braking system for two cylinders of a multi-cylinder engine includes a supply of low pressure fluid, an engine fluid sump, and a valve actuator operably coupled to each cylinder. Each of the valve actuators is configured to be alternatively fluidly coupled to the supply of low pressure fluid and the engine fluid sump. The system also includes a braking control valve operably coupled to two of the valve actuators. The braking control valve is movable between a first position at which the two valve actuators are fluidly coupled to the engine fluid sump and blocked from the supply of low pressure fluid and a second position at which the two valve actuators are fluidly coupled to the supply of low pressure fluid and blocked from the engine fluid sump. A check valve is associated with each of the valve actuators. Each check valve is configured to prevent fluid flow from the respective valve actuator to the supply of low pressure fluid. At least one exhaust valve is operably coupled to each valve actuator.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a schematic illustration of an engine braking system according to an exemplary embodiment of the present invention; and
FIG. 2
is a cross-sectional diagrammatic view of a brake control valve of the engine braking system shown in FIG.
1
.
DETAILED DESCRIPTION
Referring now to
FIG. 1
, an engine braking system
100
, for example, an engine compression braking system, for a multi-cylinder engine (not shown) is disclosed. The engine braking system
100
includes an input device
102
electrically coupled to an electronic control module (ECM)
104
. The input device
102
may be, for example, a selectively switchable control available in an operator compartment of a vehicle, an automatic switch associated with a vehicle brake pedal, or any known method of providing an input signal. Optionally, the engine braking system
100
may include a sensor
106
configured to sense a crankshaft position indicator
108
. The indicator
108
may be correlated to a top-dead-center position of each piston (not shown) in a cylinder
110
of the engine.
The ECM
104
is electrically coupled to one or more braking control valves
114
. Although only one braking control valve
114
and two cylinders
110
are shown for simplicity, it should be understood that more than one braking control valve may be required for an engine having more than two cylinders, as will be discussed below.
The engine braking system
100
further includes a supply
118
of hydraulic fluid, such as oil, at low pressure. The low pressure oil supply
118
may be the lubrication oil passed through the engine gallery to lubricate bearings and other engine components. The braking control valve
114
may include a supply port
122
fluidly coupled to the low pressure supply
118
via a hydraulic line
120
. The braking control valve
114
may also include a vent port
124
fluidly coupled to an engine fluid sump
126
via a hydraulic line
128
.
The engine braking system
100
also includes a valve actuator
130
, for example, a master/slave piston assembly, associated with each cylinder of the engine. The braking control valve
114
may include an actuation port
132
fluidly coupled to a pair of valve actuators
130
via a pair of hydraulic manifolds
134
. Each manifold
134
may include a check valve
136
arranged to prevent fluid flow back to the braking control valve
114
. It should be appreciated that the pair of manifolds
134
may be combined between the check valve
136
and the actuation port
132
, but one check valve
136
is associated with each valve actuator
130
to independently provide pressurized fluid to actuator manifolds
146
,
148
associated with each of the valve actuators
130
.
The braking control valve
114
may also include two drain ports
138
,
140
fluidly coupled to the pair of valve actuators
130
via a pair of hydraulic lines
142
,
144
. The hydraulic lines
142
,
144
are separately coupled to the two drain ports
138
,
140
to avoid unintentional actuation of the actuator associated with one cylinder by return fluid flow from the actuator associated with another cylinder.
Each valve actuator includes a first piston assembly
150
and a second piston assembly
170
. The first piston assembly
150
includes a piston
152
slidable in a housing
154
. The piston
152
may be coupled with a plunger
156
and a spring
158
arranged to urge the piston
152
in a first direction. The plunger
156
may be mechanically coupled to a rocker arm
160
associated with, for example, a fuel injection system (not shown). It should be appreciated that the rocker arm
160
may be independent of the fuel injection system. The rocker arm
160
may be mechanically coupled to a rotatable cam
162
, for example, a cam that determines fuel injection timing, and an associated cam follower
164
so as to transfer rotational motion of the cam
162
to linear motion of the piston
152
in the first direction. The piston
152
and the housing
154
define a first pressure chamber
166
in fluid communication with an actuator manifold
146
or
148
.
The second piston assembly
170
includes a piston
172
slidable in a housing
174
. The piston
172
may be coupled with a plunger
176
and a spring
178
arranged to urge the piston
172
in a first direction. The plunger
176
may be mechanically coupled to a rocker arm
180
associated with an exhaust valve
182
. The rocker arm
180
may be mechanically coupled to a rotatable camshaft, cam, and associated cam follower (not shown) so as to transfer rotational motion of the camshaft to linear motion of the exhaust valve
182
for opening and closing an exhaust outlet
184
of the cylinder
110
, as is well known in the art. The piston
172
and the housing
174
define a second pressure chamber
186
in fluid communication with an actuator manifold
146
or
148
.
Referring now to
FIG. 2
, the braking control valve
114
includes a spool valve
202
slidable in a valve body
204
. The braking control valve
114
may also include a spring
206
urging the spool valve
202
in a first direction toward a closed position of the braking control valve
114
. The braking control valve
114
may further include a solenoid
208
arranged to operate the braking control valve
114
to move the spool valve
202
in a second direction, opposite the first direction and opposite the spring force, toward an open position of the braking control valve
114
.
The spool valve
202
includes a series of lands
210
,
212
,
214
,
216
,
218
delimiting a series of annuluses
220
,
222
,
224
,
226
. The annuluses
220
,
222
are arranged on the valve
202
to fluidly communicate with the respective drain ports
140
,
138
when the braking control valve
114
is in the closed position (FIG.
2
). The annuluses are also arranged such that the fluid communication with respective ports
140
,
138
ceases when the braking control valve is in an open position (not shown).
The annulus
226
is always in fluid communication with the supply port
122
. When the braking control valve
114
is in an open position, the annulus
226
also fluidly couples the actuation port
132
with the supply port
122
. Optionally, the annulus
224
may be in fluid communication with the actuation port
132
when the braking control valve
114
is in a closed position. This optional fluid communication allows drainage from the hydraulic manifold
134
, for example, when the engine is turned off.
The spool valve
202
also includes a plurality of radial throughholes
230
,
232
,
234
arranged to fluidly couple a respective annulus
220
,
222
,
224
to a longitudinal bore
236
. Each throughhole
230
,
232
,
234
, may include a pair of throughholes perpendicular to one another. The longitudinal bore
236
, in turn, is fluidly coupled to the vent port
124
.
It should be appreciated that a 6-cylinder engine having one exhaust valve per cylinder would have 6 exhaust valves and 6 exhaust valve actuators. Thus, for such a 6-cylinder engine, the engine braking system
100
may include three braking control valves
114
if all six cylinders are to be used for engine braking. On the other hand, a 6-cylinder engine having two exhaust valves per cylinder would have twelve exhaust valves and twelve exhaust valve actuators. However, the two exhaust valves for each cylinder could be bridged so that one actuator would drive both exhaust valves in one cylinder.
It should further be appreciated that the input device
102
may be an operator-switchable input that may provide an on/off signal or that may provide a variable braking signal. For example, in a 6-cylinder engine, the input device
102
may be switchable between off, 2-cylinder, 4-cylinder, and 6-cylinder positions, such that the amount of engine braking can be varied.
Industrial Applicability
In operation, the ECM
104
may enter an engine braking mode in response to a signal from the input device
102
. During an engine braking mode, fuel supply to the engine cylinders
110
used for engine braking should be stopped. The ECM
104
may receive signals from the sensor
106
to attain appropriate timing during the engine braking mode such that compressed air is released from the cylinder
110
through the exhaust outlet
184
when the piston is near a top-dead-center position.
In the engine braking mode, the ECM
104
energizes the solenoid
208
, which moves the braking control valve
114
from a first, closed position to a second, open position. Energizing the solenoid
208
causes the spool valve
202
to move in a direction opposite to the force of the spring
206
(upward in
FIG. 2
) to fluidly couple the supply port
122
and the actuation port
132
. In addition, the spool valve
202
blocks fluid communication between the drain ports
138
,
140
and the sump
126
. As a result, hydraulic fluid from the low pressure supply
118
flows to the hydraulic manifolds
134
and is available for use by the valve actuators
130
.
If the pressure of hydraulic fluid in a hydraulic manifold
130
is high enough to open the associated check valve
136
, then the fluid may flow to the associated actuator manifold
146
or
148
and return line
142
or
144
, as well as to the first pressure chamber
166
and the second pressure chamber
186
. The check valves
136
may be structured and arranged to allow fluid flow from the hydraulic manifold
130
when the pressure of fluid in the associated actuator manifold and return line drops below a predetermined pressure. Therefore, at least the predetermined pressure is kept available to the valve actuators
130
.
At times when the braking control valve
114
is in the second position, the “master” piston assembly
150
may act as a pump, providing pressurized fluid to the “slave” piston assembly
170
. For example, linear movement of the piston
152
of the first piston assembly
150
in a direction of the force of the spring
158
, in response to motion of the cam
162
, the cam follower
164
, and the rocker arm
160
, causes linear movement of the piston
172
of the second piston assembly
170
. Since the hydraulic fluid in the first pressure chamber
166
, the actuator manifold
146
or
148
, the return line
142
or
144
, and the second pressure chamber
186
cannot be drained or otherwise relieved, the piston
172
of the second piston assembly
170
is moved in a direction opposite to the force of the spring
178
. In turn, the plunger
174
of the second piston assembly
170
is urged downward against the rocker arm
180
, which urges the exhaust valve
182
to an open position. The open position of the exhaust valve
182
allows compressed air to escape the cylinder
110
via the exhaust outlet
184
, thereby performing an engine braking function. Thus, rotation of the cam
162
causes the exhaust valve
182
to open and close in a cyclical manner during the engine braking mode.
At times when the ECM
104
is not operated in the engine braking mode, the solenoid
208
is not energized and the braking control valve
114
is not actuated. When the braking control valve
114
is not actuated, the return spring
206
in the braking control valve
114
moves the spool valve
202
to the first position shown in FIG.
2
. In the first position, the supply
118
of low pressure fluid is blocked from the actuation port
132
, and the drain ports
138
,
140
are in fluid communication with the engine fluid sump
126
via the vent port
124
.
It should be appreciated that the operation and timing of the valve actuators
130
may be pre-selected to achieve a desired amount of engine braking. For example, in a 6-cylinder engine, each of the valve actuators
130
may open a corresponding exhaust valve
182
once during a 360° crankshaft rotation. Thus, during one crankshaft rotation, each of the six cylinders
110
will have contributed to the engine braking function. As discussed, the level of braking may be determined by the ECM
104
in response to a manual control command by the operator, a cruise control system command, or an automatic braking system command.
It will be apparent to those skilled in the art that various modifications and variations can be made in the engine braking system without departing from the scope of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only.
Claims
- 1. An engine braking system for a multi-cylinder engine, comprising:a supply of low pressure fluid; an engine fluid sump; a plurality of valve actuators, each of the valve actuators being configured to be alternatively fluidly coupled to the supply of low pressure fluid and the engine fluid sump, each valve actuator being operably coupled to at least one exhaust valve of a respective cylinder; and a braking control valve operably coupled to two of the valve actuators, the braking control valve being movable between a first position at which the two valve actuators are fluidly coupled to the engine fluid sump and blocked from the supply of low pressure fluid and a second position at which the two valve actuators are fluidly coupled to the supply of low pressure fluid and blocked from the engine fluid sump.
- 2. The engine braking system according to claim 1, further including a check valve associated with each of the two valve actuators, each check valve being configured to prevent fluid flow from the respective valve actuator to the supply of low pressure fluid.
- 3. The engine braking system according to claim 1, wherein the braking control valve includes a supply port fluidly coupled to the supply of low pressure fluid.
- 4. The engine braking system according to claim 3, wherein the braking control valve includes a spool valve slidable in a valve body.
- 5. The engine braking system according to claim 4, wherein the spool valve is an electrically-actuated spool valve.
- 6. The engine braking system according to claim 5, wherein the braking control valve includes a solenoid configured to selectively actuate the spool valve.
- 7. The engine braking system according to claim 4, wherein the braking control valve further includes a spring arranged to urge the spool valve to a first position.
- 8. The engine braking system according to claim 7, wherein the braking control valve further includes a first drain port and a second drain port, the first drain port fluidly coupling a first valve actuator with the engine fluid sump and the second drain port fluidly coupling a second valve actuator with the engine fluid sump when the spool valve is urged to the first position by the spring.
- 9. The engine braking system according to claim 8, wherein the spool valve is moved to a second position when actuated.
- 10. The engine braking system according to claim 9, wherein the braking control valve includes an actuation port fluidly coupled with the valve actuators, the actuation port being fluidly coupled with the supply port when the spool valve is actuated to the second position.
- 11. The engine braking system according to claim 10, wherein fluid communication between the first drain port and the first valve actuator and between the second drain port and the second valve actuator is blocked when the spool valve is actuated to the second position.
- 12. The engine braking system according to claim 11, wherein the braking control valve further includes a vent port configured to fluidly couple the first drain port and the second drain with the engine fluid sump when the spool valve is in the first position.
- 13. The engine braking system according to claim 12, wherein the valve spool includes a longitudinal bore fluidly coupled to the vent port, a first annulus associated with the first drain port and fluidly coupled to the longitudinal bore via at least one radial bore corresponding to the first annulus, and a second annulus associated with the second drain port and fluidly coupled to the longitudinal bore via at least one radial bore corresponding to the second annulus.
- 14. The engine braking system according to claim 1, including a hydraulic manifold coupled to the braking control valve, the hydraulic manifold being fluidly coupled to at least one of the exhaust valve actuators.
- 15. The engine braking system according to claim 1, further including an electronic control module configured to control timing of actuation and de-actuation of the braking control valve with respect to a piston top-dead-center position in a cylinder.
- 16. An engine braking method for a multi-cylinder engine wherein compressed air from the compression stroke of a cylinder is used for engine braking and the compressed air is released through a cylinder exhaust valve near a piston top-dead-center position, the method comprising:supplying fluid from a supply of low pressure fluid to a braking control valve; and selectively controlling movement of the braking control valve between a first position at which two valve actuators are fluidly coupled to an engine fluid sump and blocked from the supply of low pressure fluid and a second position at which the two valve actuators are fluidly coupled to the supply of low pressure fluid and blocked from the engine fluid sump, each of the valve actuators operably coupled to an exhaust valve of a different cylinder.
- 17. The engine braking method according to claim 16, further including preventing fluid flow from the valve actuators to the supply of low pressure fluid via the braking control valve.
- 18. The engine braking method according to claim 16, wherein said selectively controlling includes actuating a spool valve such that the spool valve slides in a valve body of the braking control valve from a first position to a second position.
- 19. The engine braking method according to claim 16, further including opening at least one of said exhaust valves when a piston is near a top-dead-center position in a cylinder.
- 20. An engine braking system for two cylinders of a multi-cylinder engine, comprising:a supply of low pressure fluid; an engine fluid sump; two valve actuators, each valve actuator operably coupled to a different one of the two cylinders, each of the valve actuators being configured to be alternatively fluidly coupled to the supply of low pressure fluid and the engine fluid sump; a braking control valve operably coupled to the two valve actuators, the braking control valve being movable between a first position at which the two valve actuators are fluidly coupled to the engine fluid sump and blocked from the supply of low pressure fluid and a second position at which the two valve actuators are fluidly coupled to the supply of low pressure fluid and blocked from the engine fluid sump; a check valve associated with each of the two valve actuators, each check valve being configured to prevent fluid flow from a respective valve actuator to the supply of low pressure fluid; and at least one exhaust valve operably coupled to each of the two valve actuators.
US Referenced Citations (16)