Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Patent
1996-09-17
1999-04-20
Koczo, Michael
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
F02B 3712
Patent
active
058947310
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a device for regulating the engine braking power of an internal combustion engine in a motor vehicle, which is equipped with a compression braking device, a device for varying the degree of charging during braking, and driver actuated means for activating the compression braking device and the device for varying the degree of charging.
DESCRIPTION OF THE RELATED ART
It is known that the engine braking power of a vehicle can be increased with the aid of a device of the above described type, by means of which the engine combustion chambers during braking are placed in communication, during the latter portion of the compression stroke, with the exhaust system, for example by opening the exhaust valves. The result will be that air compressed during the compression stroke will flow out from the cylinders, and thus compression work carried out during the compression stroke cannot be recovered during the expansion stroke, and therefore the braking power of the engine will be increased. An additional increase in the braking power can be achieved in a known manner by also placing the exhaust system in communication with the cylinder during the latter portion of the intake stroke, so that gases from the exhaust system can flow into the cylinders. This results in an increasing pressure in the cylinder and an inner charging, thus increasing the compression work after closing off the communication between the cylinders and the exhaust system. The degree of inner charging can be varied by means of an exhaust pressure governor (EP-governor), i.e. a damper in the exhaust duct, which can be controlled by the driver in a known manner between the completely open and completely closed positions.
Common to the hitherto known systems for increasing the braking power of the engine is that they all work without any feedback, i.e. when they are activated by the driver, for example by throwing a switch and releasing pressure on the accelerator, the engine will provide maximum braking power. In the example described above, this will involve, firstly, that the exhaust system is placed in communication with the cylinders during the latter portion of the intake stroke and/or compression stroke, and, secondly, closing the damper of the exhaust pressure governor. The engine will thus generate maximum braking power regardless of external conditions, such as road slope and the friction of the tires against the road surface. These external conditions sometimes cause the retardation to be greater than what is desired or cause the vehicle drive wheels to skid.
SUMMARY OF THE INVENTION
The purpose of the present invention is to achieve a device of the type described by way of introduction, which has a feedback regulating system, which primarily controls the retardation instead of the braking power to thereby eliminate the above mentioned disadvantages of the known devices.
This is achieved according to the invention by virtue of the fact that the driver actuated means are coupled to a control unit, to which the driver, via said means, can feed a command value for vehicle retardation and to which, via sensors connected to the same, engine data, such as degree of charge and rpm, and vehicle data, such as vehicle speed, accelerator position and clutch pedal position, are fed, and that the control unit is disposed to compare the set command value for the retardation with the actual value thereof and deliver a signal for setting the degree of charging as a function of said difference and of the accelerator position or the clutch pedal position.
In its simplest form the driver actuated means for setting the command value can have a single preset retardation level and be activated when the driver lifts his foot from the accelerator, so that the same retardation is always obtained regardless of external conditions. The retardation is in this case preset at a level which minimizes the risk of wheel skidding. In a preferred further development of the invention, the means for setting the
REFERENCES:
patent: 4961145 (1990-10-01), Gernot
patent: 5127501 (1992-07-01), Arikawa
patent: 5410882 (1995-05-01), Davies et al.
patent: 5444980 (1995-08-01), Dellora et al.
patent: 5647318 (1997-07-01), Feucht et al.
AB Volvo
Koczo Michael
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