Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1997-03-27
2001-09-25
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S446000
Reexamination Certificate
active
06293253
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a control for a pressure fluid supply system, in particular for the high pressure in a fuel injection system, for example for an internal combustion Diesel engine, in accordance with the preamble of claim
1
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PRIOR ART
A control of this type has become known, for example, from the document EP 0 299 337 A2. A suction throttle located in the suction line of the high-pressure pump is employed here as the device limiting the amount of fluid conveyed, which is set in accordance with the pressure fluid requirement of the consumers in such a way that the high-pressure pump only conveys the actually required pressure fluid amounts into the common high-pressure line, i.e. the common rail. In this known case this is referred to as suction pressure control, which operates as follows:
A pressure sensor is provided in the common high-pressure line, i.e. the common rail, whose pressure signal is provided to a control unit which, as a rule, operates electronically, and is compared there with a set value determined by the operating conditions of the internal combustion engine. An adjustment signal is issued in accordance with the control difference, which adjusts the suction throttle until the set pressure value has been attained in the common rail.
Comparatively elaborate electronic sensor devices and corresponding electronic devices are therefore connected with the known suction throttle control which—as has been found—still has an inadequate response behavior and too slow a control speed for certain areas of application. In the known case this lack of dynamics appears in particular when it is necessary to relieve the pressure in the common rail extremely rapidly. Although the suction throttle valve can be rapidly closed in this case, the high-pressure area, i. e. the common rail, can only be relieved as the result of amounts of leakage or remaining injection amounts.
The object of the invention is therefore based on providing a control for a pressure fluid supply system, in particular for the high pressure in a fuel injection system, for example for an internal combustion Diesel engine, which is distinguished by improved control dynamics, in particular when reducing the pressure in the common rail, while avoiding elaborate electronic sensor devices.
SUMMARY OF THE INVENTION
In accordance with the invention, the pressure in the common high-pressure line, i.e. the common rail, is protected via a high-pressure pressure control valve, preferably in the embodiment of an electrically triggered pressure control valve. The adjusting signal for charging the adjusting element of the device limiting the amount of fluid conveyed is derived from a physical value, which changes in accordance with the amount of fluid throughput in the delivery line of the preferably adjustable pressure control valve. The same as the adjusting signal of the pressure sensor device of the prior art, this adjustment signal operates in the sense of a reduction of the control deviation, but with the particular advantage that the control system can be kept considerably shorter. The control the pressure in the common rail with only the adjustable pressure control valve is therefore achieved, which is preferably embodied as a proportional pressure valve, and to limit the amount of excess pressure fluid or fuel fed by the high-pressure pump into the common rail by means of the derived control signal in the delivery line in such a way, that the energy losses are kept as low as possible.
The particular advantage of the control in this case rests in the higher dynamics, because the downward control of the pump occurs simultaneously with the triggering of the pressure control valve. In other words, the pressure release in the common rail is no longer performed as a result of leakage amounts or remaining injection amounts flowing off, but actively by the adjustable pressure control valve. In the process, increased safety results in case of problems which may occur in the common rail, for example upon the appearance of an emergency in the system, for example binding of an injection nozzle needle or like occurrence. If in such a case the pressure control valve is triggered, it is possible by means of the amount of fluid flowing off, to generate a corresponding adjustment signal, preferably with suitable amplification, so that the high-pressure pump is abruptly reduced to a minimal conveying volume. Therefore dangerous situations can also very quickly be defused by means of the control in accordance with the invention. On the other hand it is possible to achieve pressure build-ups which are easily comparable to systems with suction pressure control.
It has been shown that a very good response behavior of the control can be realized with an adjustable pressure control valve, in particular in the embodiment as an electrically triggered pressure control valve, because a direct force comparison between the pressure force and magnetic force is performed in such a pressure control valve. The behavior of the control can be optimized by means of a suitable adaptation of the adjusting signal of the pressure control valve to the opening characteristics and/or the generation of the adjusting signal, for example in order to keep the excess amount of fluid conveyed by the high-pressure pump at a negligibly small value.
The pressure control valve is advantageously embodied as a proportional control valve. As a substitute, however, it is also possible with the aid of an appropriate electronic device to correct a non-proportional characteristic curve of the pressure to become a control current, wherein it is then also possible to employ a pressure control valve with a non-linear characteristic curve.
The control principle in accordance with the invention can be realized by means of the most diverse adjusting signals. However, a particularly simple way of control results if the adjusting signal is derived from a dynamic pressure upstream of a dynamic throttle in the delivery line. It is possible by means of this further development to maintain the dynamics of control at a very high level, because by means of the dynamic pressure it is possible to send the adjusting signal with good and adaptable amplification to the device for limiting the amounts of fluid conveyed.
Further than that, the control is also suitable for the most diverse embodiments of the device for limiting the amounts of fluid conveyed. If the suction throttle device has a number of suction valves corresponding to the number of the displacement devices of the high-pressure pump, the amounts conveyed by the pump can be easily adapted to the needs of the injection system. In this case it is basically possible to throttle the individual suction valves simultaneously. Additional possibilities of fine matching to the conveyed amounts actually needed by the common rail result from the sequential triggering of the suction valves.
A further variant is the design of the device for limiting the amounts of fluid conveyed. Here the adjusting signal, for example the dynamic pressure upstream of a dynamic throttle in the delivery line, can be used to shut off one displacement device or several displacement devices individually. This can be accomplished through a single control valve, which directly blocks the inflow to the respective displacement device, or by an actuating element, which acts directly via a plunger on a closing body of the suction valves of the respective displacement device and keeps this closing body permanently open, so that this displacement device does not perform any displacement work anymore. With this variant it is also possible for the individual adjusting elements to respond sequentially to the adjusting signal wherein a greater latitude for the exact adjustment of the displaced volume results, particularly in connection with pumps with a multitude of displacement pistons.
The device for limiting the amount of fluid conveyed can also be provided in that a pre-conveying pump, which feeds the high-pressure pump, is correspon
Arnold Bernhard
Eisenbacher Egon
Pawellek Franz
Greenberg Laurence A.
Lerner Herbert L.
Miller Carl S.
Siemens Aktiengesellschaft
Stemer Werner H.
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