The present system and method relate to increasing the engine braking capability of a vehicle. More specifically, the system and method relate to coordinating the use of a hydraulic fan from the cooling system of the vehicle with the compression braking system to increase overall engine braking capabilities.
Engine braking occurs when the retarding forces within an engine are used to slow a vehicle down, as opposed to using an external braking mechanism such as friction brakes or magnetic brakes. Large vehicles, including large diesel trucks typically use a compression release brake, also known as “Jacob brake” or “Jake brake.” This type of brake is most commonly confused with real engine braking; it is used mainly in large diesel trucks and works by opening the exhaust valves at the top of the compression stroke, resulting in adiabatic expansion of the compressed air, so the large amount of energy stored in the compressed air is not returned to the crankshaft, but is released into the atmosphere.
Normally during the compression stroke, energy is used as the upward-traveling piston compresses air in the cylinder. The compressed air then acts as a compressed spring and pushes the piston back down. However, with a Jake brake in operation, the compressed air is suddenly released just before the piston begins its downward travel. This sudden release of compressed air creates audible sound waves similar to the expanding gases escaping from the muzzle of a firearm. Having lost the energy stored within the compressed air, the engine is then made to pull the piston down, which draws new air into the cylinder, and then travel upward again, compressing the new volume of air, which will again be released to the atmosphere after having been compressed. Though this action, the engine loses energy. The efficiency of the engine brake could be measured due to engine boost pressure increase and how fast the engine decreases the speed.
The use of compression release engine brakes may cause a vehicle to make a loud chattering or “machine gun” noise, especially vehicles having high flow mufflers, or no mufflers at all, causing many communities in the United States to prohibit compression braking within municipal limits. Therefore, given these restrictions, there is a need to increase the engine braking capacity. The present system and method incorporates use of a hydraulic fan, which is already part of the cooling system of the vehicle, to further increase the energy or power load on the engine, resulting in reduced speed and maximizing braking performance.
There is disclosed herein an improved system and method for increasing the engine braking capacity of a vehicle engine, which avoids the disadvantages of prior systems while affording additional structural and costs advantages.
Generally speaking, the present system and method relates to increasing the engine braking capacity of an engine, through increasing the speed of a hydraulic fan in synchrony with application of the engine braking system.
A method for increasing engine brake capability of a vehicle engine, is disclosed. In an embodiment, the method includes the steps of providing a compression release braking system, providing an energy drawing component for increasing power draw on the vehicle engine, and, increasing the engine braking capability by synchronizing operation of the energy drawing component with operation of the compression release braking system.
A system for increasing engine braking capacity on a vehicle, is disclosed. In an embodiment, the system includes a compression release brake, a power absorbing component of a cooling system and, a controller for integrating operation of the power absorbing component with the compression release brake to increase the braking capacity of the engine.
These and other features and advantages of the engine braking system and method can be more readily understood from the following detailed discussion with reference to the appended drawing figures
Referring to
As mentioned, engine braking occurs when the retarding forces within an engine are used to slow down a vehicle, as opposed to using an external braking mechanism, such as friction brakes or magnetic brakes. Therefore, in an effort to increase the engine braking capacity, the present system incorporates the use of the hydraulic fan 38 from the cooling system 30. The hydraulic fan 38 is a power consumer of energy, and therefore, the fan is used as an energy drawing component on the engine. The fan power is proportional to the fan speed (P1/P2=(n1/n2)3). Therefore, running the fan at a maximum speed, results in greater power drag and subsequent slow down of the engine, which reduces the engine speed and maximizes the engine braking performance.
Operation of the hydraulic fan 38 is synchronized with the operation of the compression brake system 20 through use of the fan electronic controller 40. For example, when the driver steps off the accelerator pedal (not shown), a signal is sent to the fan electronic controller 40, which then activates the hydraulic fan 38. The hydraulic fan 38 starts running up to a maximum speed, which then pulls energy from the engine, slowing the engine down in coordination with the compression braking system 20. Use of the fan 38 synchronized with the compression braking system 20 improves the overall braking capacity of the engine.
The speed of the fan 38 will vary up to the maximum speed depending on the heat exchange requirements of the engine. The speed of the fan 38 is proportionally driven up to the maximum speed depending on required heat rejection or in other words, in response to the temperature of the coolant radiator inlet (not shown) and CAC intake air outlet (not shown). Because operation of the hydraulic fan 38 draws significant energy from the engine, the cooling system 30 is designed to operate the fan at the maximum speed only under specific conditions, to avoid performance and fuel penalties.