Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Patent
1996-12-06
1999-03-30
Koczo, Michael
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
123561, F02B 3710
Patent
active
058874348
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an arrangement for regulating the engine braking effect of a compressor supercharged combustion engine in a vehicle, which engine is equipped with a device for increasing the engine braking effect in a braking mode, as well as means actuable by the driver of the vehicle for activating the engine braking effect-increasing device.
It is known that the engine braking effect of a vehicle can be increased with the help of a device by means of which the combustion chamber of the engine in a braking mode can be connected to the exhaust system, for example by means of the normal exhaust valves being opened, during the latter portion of the compression stroke. As a result of this, the air compressed during the compression stroke flows out of the cylinders and the compression work performed during the compression stroke cannot be recovered during the expansion stroke, thereby providing an increase in the braking effect of the engine. A further increase of the braking effect can be achieved in a known manner by means of the exhaust system also being connected to the cylinders during the latter portion of the induction stroke so that gas from the exhaust system can flow into the cylinders. This results in a pressure increase in the cylinder and an inner charging which leads to an increase in the compression work after interruption of the connection between the cylinders and the exhaust system. Another known engine braking effect-increasing device is an exhaust pressure regulator (AP-regulator), i.e. a throttle in the exhaust system by means of which the back-pressure in the exhaust system can be increased during engine braking.
When using an AP-regulator to increase the engine braking effect, the quantity of air flowing through the cylinders is, however, reduced, which results in increased engine temperatures and thus a limitation to the possible braking effect.
The object of the present invention is to provide a braking effect-regulating arrangement of the type mentioned in the introductory portion which permits greatly increased braking effect in engine braking effect-increasing devices hitherto known, particularly at low engine speeds.
This is achieved in accordance with the invention by means of the compressor being connected to the cam shaft of the engine via a gear arrangement having variable gearing, and the gearing being controllable by a control unit in such a manner that, in a braking mode, the rotational speed of the compressor can be increased with respect to the rotational speed of the engine when the rotational speed of the engine decreases.
By varying the gearing so that the rotational speed of the compressor increases in the stated manner, the degree of charging increases, which results in an increase in the braking effect of the hitherto known engine braking devices. Since the degree of charging increases, the quantity of throughflow air also increases. Thus, an increased airflow from the compressor through the engine is obtained which thereby provides improved cooling as well as the increased braking effect.
In a preferred embodiment, the transmission is a gear arrangement with infinitely variable gearing, a so-called CVT. The arrangement according to the invention is hereby particularly advantageously employed on an engine having a turbo compressor which, in its roll as a flow machine, has considerably poorer charging capabilities at low speed than a displacement machine.
In a particularly advantageous embodiment of the arrangement according to the invention, the controls operated by the driver are connected to a control unit to which the driver can, via said controls, input a desired value for the retardation of the vehicle and in which, via sensors connected thereto, engine data such as the degree of charging and engine speed, as well as vehicle data such as the vehicle velocity, the position of the throttle pedal and the position of the clutch, are fed, whereby the control unit is arranged to compare the inputted desired value of retardation with the actual value
REFERENCES:
patent: 5133188 (1992-07-01), Okada
patent: 5729978 (1998-03-01), Hiereth et al.
Arnell Jan
Dahlgren Magnus
Udd Soren
AB Volvo
Koczo Michael
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