Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
2003-11-14
2004-12-14
Nguyen, Hoang (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C417S043000, C417S364000
Reexamination Certificate
active
06829893
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German Application No. 102 52 975.2, filed Nov. 14, 2002, the disclosures of which is expressly incorporated by reference herein.
The present invention relates to a compressor arrangement, particularly for commercial vehicles, having an internal-combustion engine for generating a rotating movement, which internal-combustion engine drives a compressor unit, which is connected on the output side. The compressor unit generates compressed air from the ambient air. A control unit triggers the generating of compressed air when compressed air is required.
Particularly in the field of commercial vehicle construction, compressor arrangements of this type are used in order to provide compressed air for the on-board pneumatic system of a commercial vehicle. The pneumatic system on board a commercial vehicle is required particularly for supplying the brake system, the air suspension, the trailer, and diverse accessories. For this purpose, the compressor arrangement of a commercial vehicle generates compressed air of approximately 12.5 bar.
The product information “High-Performance Compressors” of the firm Knorr-Bremse Systeme für Nutzfahrzeuge GmbH (Printing No. P-3505-DE-01) discloses a compressor unit which is constructed in the manner of a piston compressor. A crankshaft rotatingly disposed in a compressor housing converts a rotating movement on the input side, by means of the principle of a crankshaft drive, into a linear back and forward (reciprocating) motion of an assigned piston, which is housed in a cylinder. The piston, interacting with a valve device housed in the cylinder cover, takes in ambient air and subsequently delivers the latter in a compressed manner. The compressor unit can be obtained in a single- or multi-cylinder construction variant. The multi-cylinder construction variant is suitable for pneumatic systems with a relatively high consumption of compressed air and, correspondingly, has a higher delivery capacity.
In a generally known manner, the compressor unit is driven by way of the internal-combustion engine of the commercial vehicle. In most application cases, a rotational-speed-gearing transmission unit is connected between the internal-combustion engine and the compressor unit. In this case, the transmission unit is constructed as a spur gear system with a fixed transmission ratio in order to gear up the rotational speed generated by the internal-combustion engine to a transmission ratio of normally 1.5, so that the compressor unit mounted on the output side of the transmission unit can be operated at the permissible rotational speed. The transmission unit of the compressor unit is usually integrated directly in the vehicle transmission of the commercial vehicle.
In addition, such known compressor arrangements are provided with technical measures for saving energy. Thus, the operation of the above-described known compressor arrangement takes place by way of a control which ensures that the compressor unit starts its operation only if a compressed-air demand exists in the pneumatic system of the commercial vehicle. In most cases, the compressed-air demand is determined by way of a pressure sensor connected with the system pressure. If the system pressure falls below a defined threshold pressure, the operation of the compressor unit is started in order to again build up a sufficient air pressure. For storing the built-up pressure, pressure vessels (tanks) are customarily used in the case of the pneumatic system.
In order to implement such a demand control for starting the operation of the compressor unit, the compressor unit can be switched between a delivery phase and an idling phase. In the delivery phase, the compressed air is generated from ambient air and is fed into the pneumatic system. In contrast, the compressor unit runs without any load in the idling phase, so that, although a piston movement is carried out, no compressed air reaches the pneumatic system. This compressed air is discharged to the outside. Since, because of the eliminated load, much less power is absorbed by the compressor unit in the idling phase than in the delivery phase, this type of air demand control contributes to the saving of energy.
However, long-term tests have shown that this air-demand-controlled compressor arrangement is often operated with very short switch-on durations of from 5-10% in the delivery phase, which is the result of the predominantly long-distance hauling operation that occurs on the autobahn or highways. With such a short switch-on duration, the comparatively high switch-on duration of approximately 90% in the idling phase becomes much more important so that, as a result of the still considerable power consumption in the idling phase, on the whole, the energy consumption is higher in the idling operation than in the load operation. This result is also intensified by the fact that the compressor unit is often overdimensioned (oversized) for the normal operation in order to generate a high pressure in the pneumatic system within a very short time. This takes place particularly during the charging of the pneumatic system when the pressure tanks are empty, during the operation of the lifting axles, etc. On the whole, the known air demand control therefore still has fairly unsatisfactory results with respect to the saving of energy.
Furthermore, an air demand control of a compressor arrangement is generally also known in the state of the art which uses a mechanically operable separating clutch between the engine unit and the compressor unit. The compressor unit will be stopped by the use of the separating clutch when there no longer is a demand for compressed air. However, in comparison to a continuous idling, a compressor unit operated in such a manner is subjected to high wear as a result of an absence of a lubricating effect during the cold start. In addition, the mechanically operable separating clutch required for this air demand control is also subjected to wear so that, on the whole, fairly high maintenance expenditures are required in the case of this alternative known solution for saving energy.
It is therefore an object of the present invention to further improve an air-demand-controlled compressor arrangement of the above-mentioned type such that a more effective savings of energy of the compressor arrangement is achieved while the maintenance expenditures are simultaneously minimal.
Based on an air-demand-controlled compressor arrangement for generating compressed air from the ambient air, including a control unit for triggering the generating of compressed air when compressed air is demanded.
This object is achieved by providing an auxiliary compressor unit for covering peak demands for compressed air, which is fluidically connected in parallel with respect to the internal-combustion-engine-driven compressor unit and is driven by an electric motor. The control unit starts the operation of the auxiliary compressor unit in the event of a detected peak demand.
The invention includes the technical teaching that an auxiliary compressor unit is provided for covering peak demands for compressed air, which is fluidically connected parallel to the internal-combustion-engine-driven compressor unit and is driven by an electric motor. The control unit starts the operation of the auxiliary compressor unit in the event of a detected peak demand.
The advantage of the solution according to the invention is in particular that a smaller-dimensioned (main) compressor unit can be used, which is driven by the internal-combustion engine of the commercial vehicle. Such an internal-combustion-engine-driven compressor unit has a correspondingly lower power consumption in the idling phase and can be operated more effectively in the load phase, specifically, with a longer switch-on duration. Furthermore, the smaller-dimensioned internal-combustion-engine-driven compressor unit also requires a smaller space in the engine compartment of the commercial vehicle.
The control unit preferably controls th
Doerr Wolfgang
Gerum Eduard
Crowell & Moring LLP
Knorr-Bremse Systeme fuer Nutzfahrzeuge GmbH
Nguyen Hoang
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