Information
-
Patent Grant
-
6715467
-
Patent Number
6,715,467
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Date Filed
Wednesday, August 21, 200221 years ago
-
Date Issued
Tuesday, April 6, 200420 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
- Wilbur; R. C.
- Noe; Stephen L.
-
CPC
-
US Classifications
Field of Search
-
International Classifications
-
Abstract
An engine braking system includes a pump associated with a source of fluid, the pump supplying pressurized fluid to fuel injectors associated with the engine. An electronic controller is associated with the engine and determines a desired engine braking level as a function of various engine operating conditions and operator inputs. The engine controller produces a pump signal as a function of the desired engine braking level.
Description
TECHNICAL FIELD
The present invention is related generally to the field of internal combustion engines, and more particularly, to the field of engine braking in connection with such internal combustion engines.
BACKGROUND
On highway trucks often carry heavy loads that can total as much as eighty thousand pounds. These trucks have a significant amount of momentum while travelling down the road, especially when travelling at highway speeds, and often require large brakes associated with the wheels (generally referred to as the service brakes) to slow the truck. The service brakes generally rely on friction to slow the wheels and therefore must convert momentum energy of the truck into heat. Since the service brakes are subject to a significant amount of heat and wear in connection with slowing the vehicle, they can represent a significant operating expense if used inefficiently.
Truck manufacturers and operators have recognized that there is a need to be able to generate braking force through devices other than the service brakes. By using other devices the truck operator can extend the life of the service brakes and therefore decrease the operating cost of the truck. Engine compression brakes are one such way to achieve braking force. In general, engine compression brakes create braking force by allowing air that has entered the engine cylinders during the intake stroke to be compressed during the compression stroke, thereby consuming energy. Then, prior to the expansion stroke of the piston (which would return some of the energy stored in the compressed air back to the piston), the exhaust valve is opened to simply exhaust the compressed air. In this manner the engine acts as a compressor, relieving the compressed air out the exhaust, thereby consuming energy from the wheels through the drivetrain to create a braking force. Although, engine compression braking through the selective use of the cylinder valves works well, it would also be desirable to be able to controllably apply additional engine braking force.
The present invention is directed toward overcoming these and other drawbacks associated with prior art systems.
SUMMARY OF THE INVENTION
In one aspect of the present invention, an engine braking system is disclosed for use on an internal combustion engine, having fuel injectors associated with said engine. Also associated with the engine is a pump that provides pressurized fluid to the fuel injectors. An electronic controller is associated with the engine and determines a desired level of engine braking in response to determined engine operating conditions and produces a pump signal as a function of the desired level of engine braking signal.
These and other aspects and advantages of the invention will become apparent upon reviewing the specification in connection with the drawings and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a block diagram of an embodiment of an engine and engine braking system;
FIG.
2
. shows an actuator associated with a cylinder of the engine in a preferred embodiment of the present invention;
FIG. 3
is a flow chart of a preferred embodiment of an algorithm incorporated in software control for performing engine braking; and
FIG. 4
shows a graph of braking horsepower that can be generated using an embodiment of the present invention.
DETAILED DESCRIPTION
The present invention is explained herein with reference to a preferred embodiment of the invention as shown in the drawings and described herein. Those skilled in the art will recognize that the present invention is not limited to the single embodiment shown in the drawings and described herein, but also includes other alternative embodiments and configurations that fall within the scope of the appended claims. Throughout the drawings and specification like element numbers shall be used to refer to like components of the preferred embodiment.
Referring first to
FIG. 1
, a system level block diagram of a preferred embodiment of the engine braking system
20
is shown. The engine braking system
20
preferably includes an electronic controller
22
. Those skilled in the art will recognized that the electronic controller
22
includes a microcontroller or processor
24
, a memory device or devices
26
for storing software control and data values, input/output circuitry (not shown) to permit the controller to issue control signals to actuators outside the electronic controller and to receive sensor and other signals from outside the electronic controller, and other known features of an electronic controller
22
.
Preferably, the engine
76
includes a device for producing high pressure fluid
27
, which in a preferred embodiment may include a high pressure pump
28
, which is connected with the electronic controller
22
and receives signals from the electronic controller that affect the output of the pump
28
. In a preferred embodiment, the high pressure pump
28
is a variable displacement pump which includes a relief valve
102
connected between a high pressure rail
40
and a hydraulic reservoir
32
. In a preferred embodiment, the relief valve
102
relieves excess flow produced by the pump
28
that is not consumed by the fuel injectors, engine valves, engine brake or other engine components or accessories that use the pressurized hydraulic fluid. Although a preferred embodiment includes a high pressure pump
28
with a relief valve
102
, other embodiments may include a separate relief valve
110
, which may be electronically controlled and may be used alone or in combination with the pump relief valve
102
. Although a preferred embodiment uses a variable displacement pump, other embodiments may use a fixed displacement pump or other known pumps without deviating from the scope of the present invention.
In a preferred embodiment, the high pressure pump
28
is connected with a hydraulic reservoir
32
, through a low pressure pump
34
, a heat exchanger
36
, and a fluid filter
38
. The low pressure pump draws hydraulic fluid from the reservoir
32
and outputs the hydraulic fluid through the heat exchanger
36
and the fluid filter
38
to the high pressure pump
28
. The high pressure pump outputs the fluid at a higher pressure into the high pressure rail
40
, which is simply a connection between the pump and fuel injectors
86
,
88
,
90
and
92
. In a preferred embodiment, the pressure of the fluid in the rail
40
supplied to the fuel injectors is determined, at least in part, by a rail pressure control signal provided to the pump
28
by the electronic controller
22
. The high pressure rail
40
is connected with each of the fuel injectors
86
,
88
,
90
and
92
and the high pressure fluid in the rail
40
provides actuating force to the fuel injectors
86
,
88
,
90
and
92
. In a preferred embodiment, the hydraulic fluid includes engine oil and the reservoir
32
is preferably the engine oil pan. However, in other embodiments the high pressure fluid could include high pressure diesel fuel or any other relatively incompressible fluid that can be pressurized sufficiently to be used for the actuating force for the fuel injectors
86
,
88
,
90
, and
92
. The fuel injectors
86
,
88
,
90
,
92
are electrically connected with the electronic controller
22
, which outputs injection signals that, in combination with other factors such as rail pressure, determine the timing, quantity, rate shaping and other variables of the fuel injection event.
The engine braking system
20
preferably includes compression braking means for actuating at least the exhaust valves
66
for at least some of the engine cylinders
68
,
70
,
72
,
74
. There are engine compression braking systems that are commercially available as either original equipment, installed on the assembly line, or as an aftermarket add-on. Jacobs Manufacturing offers several different engine compression braking configurations that may be used in connection with some embodiments of the present invention. In a preferred embodiment, however, the engine compression braking system includes actuators
62
that are connected with and controlled by the electronic controller
22
. The actuators preferably include a solenoid controlled valve
42
,
44
,
46
,
48
that is connected with a fluid actuator, which in a preferred embodiment are hydraulic actuators
50
,
52
,
54
,
56
connected with a respective exhaust valve
66
of a cylinder
68
,
70
,
72
and
74
of the engine
76
. As noted above with respect to the fuel injectors
86
,
88
,
90
,
92
, although a preferred embodiment uses hydraulic fluid to supply actuating force, in other embodiments of the present invention, other pressurized fluids could also be used in connection with the actuators without deviating from the scope of the present invention as defined by the appended claims.
Referring now to
FIG. 2
, a block diagram of an actuator
62
is shown. As shown in the drawing, a solenoid controlled valve
42
is connected with and controlled by signals produced by the electronic controller
22
. The valve
42
is also connected with the source of high pressure fluid, shown in the drawing as the high pressure rail
40
. When the electronic controller
22
issues an appropriate signal, the solenoid controlled valve
42
allows pressurized fluid to flow into a chamber
58
. A piston
60
is preferably disposed within the chamber
58
and moves within the chamber
58
as a function of the fluid allowed to enter the chamber
58
by the solenoid controlled valve
42
. As shown in the drawing, the piston
60
is preferably connected with a rod
64
or other mechanism for transmitting the piston
60
motion to an exterior of the actuator
50
. The rod
64
is associated with an exhaust valve
66
mechanism in such a way that appropriate motion of the rod causes motion of an exhaust valve
66
. In this manner, when the electronic controller
22
issues an appropriate signal to the actuator
50
the exhaust valve
66
may be opened or closed. Thus, the controller
22
in combination with the actuators
50
and exhaust valves
66
, and associated components, can be used to create engine compression braking.
As shown in
FIG. 1
, the engine exhaust valves
66
may be associated with one of a plurality of engine cylinders
68
,
70
,
72
and
74
of the engine
76
. An engine piston
78
,
80
,
82
,
84
may be associated with each of the engine cylinders
68
,
70
,
72
and
74
. While only four engine cylinders are shown in the drawing, those skilled in the art will recognize that this is, for illustration purposes only and is not intended to limit the present invention to application on an engine with four cylinders. To the contrary, the engine braking system described herein may be applied to engines with six, eight or other numbers of engine cylinders without deviating from the scope of the present invention as defined by the appended claims. Further, although the drawing of
FIG. 1
, illustrates certain features associated with the engine
76
, those skilled in the art will recognize that other components are included with such engine
76
, but are omitted from the drawing for clarity. For example; although the drawing shows one exhaust valve
66
associated with each of the engine cylinders
68
,
70
,
72
and
74
, those skilled in the art will recognize that the engine could include additional exhaust valves, and also includes at least one intake valve (not shown). Likewise, the number of actuators
50
, may also be increased.
As is known to those skilled in the art, the electronic controller
22
preferably produces fuel injection signals, which are delivered to the fuel injectors
86
,
88
,
90
, and
92
. The fuel injection signals determine the timing and amount of fuel to be injected into the individual engine cylinders
68
,
70
,
72
and
74
. Various strategies exist for calculating the timing and duration of those injections. However, those strategies are beyond the scope of the present invention and therefore are not discussed herein. Fuel is delivered to the fuel injectors
86
,
88
,
90
, and
92
through a fuel line
106
which is connected with a fuel reservoir or fuel tank
96
through a fuel pump
98
and a fuel filter
100
. Fuel that is not injected into an engine cylinder is returned to the reservoir through a return line
108
.
As will be apparent to those skilled in the art, the high pressure rail
40
may have a high pressure relief valve (not shown) associated with the rail to limit the pressure in the rail. As shown in
FIG. 1
, the high pressure relief valve
102
is shown associated with the high pressure pump
28
, although it could be placed elsewhere within the system and perform the same function.
The electronic controller
22
may be programmed in connection with the algorithm shown in
FIG. 3
, which as described in the following paragraphs performs engine braking. The electronic controller
22
, preferably receives operator inputs and inputs from various sensors on the engine
76
and on the truck to determine that engine braking is appropriate. The electronic controller then preferably generates an engine braking signal. For example, one operator input may be a throttle pedal position
104
, which will indicate to the electronic controller
22
whether the operator is demanding power from the engine. In the event that the operator is pressing the throttle pedal and demanding power, then the electronic controller
22
will determine that no engine braking is required and will not generate the engine braking signal. In some embodiments, there are also switches or other operator interface devices such as touch pads or the like, which will allow the operator to enable, or disable engine braking. In a preferred embodiment, the electronic controller
22
will use those inputs to determine whether to generate the engine braking signal. Algorithms used to determine when engine braking is required are known in the art and are therefore not discussed further herein. However, the algorithm discussed below with reference to
FIG. 3
, creates additional engine braking once the controller determines that braking is necessary and therefore discusses some of the novel aspects of engine braking associated with the present invention.
INDUSTRIAL APPLICABILITY
Referring now to
FIG. 3
, a flowchart of an embodiment of an algorithm associated with software control for a preferred embodiment of the invention is shown. In block
300
, the electronic controller
22
determines that engine braking is required. Program control then passes to block
310
.
In block
310
, the electronic controller
22
issues a braking command to the engine compression brake associated with the engine exhaust valves
66
. The braking command may take the form of a single signal to a bolt on, or aftermarket, compression brake, or the signal may be several signals to the individual actuators
62
at appropriate times and durations to effectuate the compression braking. Program control then passes to block
320
.
In block
320
, the electronic controller
22
issues a pump output command to the high pressure pump
28
that preferably causes the pump to go to maximum displacement. The power required by the pump is a function of flow rate and output pressure. Since the flow rate is a function of the commanded pump displacement and the pump speed, and since the pump speed is a function of engine speed, flow rate can be calculated from the commanded pump displacement and the engine speed. Excess flow not required by the system to actuate compression brakes, valves or other engine systems or accessories is preferably relieved by a relief valve
102
which is internal to the high pressure pump
28
. In an alternate embodiment, a high pressure relief valve
110
may be connected between the high pressure rail
40
and the reservoir
32
and can be used to control excess flow. The output pressure of the pump is determined, in part, by sensing the rail pressure and the pump output command. For example, in some embodiments the rail pressure is a closed loop control and the pressure can be varied by the electronic controller
22
depending on engine operating conditions. In one set of circumstances, the electronic controller
22
may control rail pressure to about 30 MPa. Referring to
FIG. 4
, the power dissipated by the pump, for one pump configuration, is shown for various rail pressures, and for various engine speeds.
FIG. 4
generally illustrates the braking effect of an embodiment of the present invention, and although one embodiment of the present invention may achieve the power dissipation levels shown in
FIG. 4
, other engine and pump configurations may result in a greater or lesser amount of power being dissipated through the engine braking process.
Claims
- 1. An engine braking system comprising:an internal combustion engine; fuel injectors associated with said engine; a pressurized source of fluid associated with said fuel injectors, said pressurized fluid providing power to actuate a fuel injector; a pump associated with said fluid, said pump being connected with said engine and pressurizing said source of fluid; an electronic controller associated with said engine, said controller determining a desired engine braking level in response to determined engine operating conditions and producing a pump signal as a function of said desired engine braking level.
- 2. The engine braking system of claim 1, wherein:said pump is a variable displacement pump; and said pump signal includes a command to run the pump at fill displacement.
- 3. The engine braking system of claim 1, including:a compression brake associated with exhaust valves of said engine; wherein said compression brake is connected with said source of pressurized fluid; and wherein said electronic controller activates said compression brake as a function of said desired engine braking level thereby causing an exhaust valve to open while an engine cylinder has compressed air therein.
- 4. The engine braking system of claim 1, wherein said pump signal includes a command to increase the pressure of said source of pressurized fluid.
- 5. The engine braking system of claim 2, wherein said pump signal includes a command to increase the pressure of said source of pressurized fluid.
- 6. The engine braking system of claim 4, wherein said fluid comprises engine oil.
- 7. The engine braking system of claim 4, wherein said fluid comprises fuel.
- 8. The engine braking system of claim 2, wherein said electronic controller determines said desired engine braking level as a function of operator inputs and at least one sensed engine operating parameter.
- 9. The engine braking system of claim 2, wherein said at least one sensed engine operating parameter includes an engine speed.
- 10. The engine braking system of claim 1, including:an electronically controlled fluid powered actuator associated with at least one exhaust valve of said engine and connected with said source of pressurized fluid and said electronic controller; wherein said electronically controlled fluid powered actuator is responsive to said engine braking signal to controllably open and close said exhaust valve.
- 11. An engine braking system associated with a compression ignition engine, comprising:at least one an electronically controlled fluid powered actuator associated with an exhaust valve of said engine; a source of pressurized fluid connected with said actuator; a pump associated with said source of pressurized fluid, an output flow of said pump controllable; an electronic controller connected with said actuator, said pump, an operator input and an engine parameter sensor, wherein said engine controller produces a desired engine braking level signal as a finction of said operator input and said engine parameter sensor and produces a pump output signal as a function of said braking level signal.
- 12. The engine braking system according to claim 11, including:at least one electronically controlled fluid actuated fuel injection device associated with a cylinder of said engine; wherein said electronic controller is connected with said fuel injection device and produces a fuel injection signal to control fuel injected by said fuel injection device; and wherein said fuel injection device is connected with said source of pressurized fluid.
- 13. The engine braking system according to claim 11, wherein said pump includes a variable displacement pump.
- 14. The engine braking system according to claim 13, wherein flow output from said pump is a function of said pump output signal.
- 15. The engine braking system according to claim 14, wherein said pump output signal corresponds to a maximum flow output in response to said braking signal.
- 16. The engine braking system according to claim 13, including:a pressure sensor associated with said source of pressurized fluid, said pressure sensor producing a signal indicative of the pressure of said fluid; and said electronic controller receiving said pressure signal and producing said pump output signal as a function of said signal and a desired pressure.
- 17. The engine braking system according to claim 15, including:a pressure sensor associated with said source of pressurized fluid, said pressure sensor producing a signal indicative of the pressure of said fluid; and said electronic controller receiving said pressure signal and producing said pump output signal as a function of said signal and a desired pressure.
- 18. The engine braking system according to claim 16, wherein said desired pressure is increased as a function of said braking signal.
- 19. A method of providing engine braking for an internal combustion engine, said engine having associated fuel injectors, a pressurized source of fluid associated with and providing power to actuate said fuel injectors, a pump connected with said engine for pressurizing said fluid, and an electronic controller associated with said engine, comprising the steps of:determining a desired engine braking level in response to determined engine operating conditions, and producing a pump signal as a function of said desired engine braking level.
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