Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1989-09-19
1993-04-27
Miller, Carl S.
Internal-combustion engines
Charge forming device
Fuel injection system
123506, 123449, F02M 5100, F02M 3704
Patent
active
052052621
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is directed to a fuel injection pump system, for internal combustion engines, of the generic type which includes a distributor type fuel injection pump having an axially oscillating plunger delimiting a pump work space, an electrically controlled switching valve arranged between the pump work space and a low pressure space filled with fuel, and a computerized control device for controlling the switching valve.
In a distributor-type fuel injection pump which has already been suggested (German Patent Application P 37 21 352.0) the reference delivery stroke effecting the injection is determined as the angle of rotation .phi..sub.Q of the pump plunger which corresponds to this reference delivery stroke. Since the control device can only process times, but not angles of rotation, an angle-time system is provided with which the time T.sub.0 required for the pump plunger to pass through a measurement window stretching over a preselected constant angle of rotation .phi..sub.0 is measured. The closing period T.sub.Q during which the determined reference delivery stroke of the pump plunger is executed is then calculated with this measurement time T.sub.O and the constant angle of rotation .phi..sub.0. The closing time is calculated according to T.sub.Q =T.sub.0 .multidot..phi..sub.Q /.phi..sub.0.
In order to keep metering errors resulting from speed changes between the time measurement and the actual metering as small as possible, the time measurement was applied as close as possible to the delivery stroke of the pump plunger effecting the injection and the time measurement window was stretched in the area of the bottom dead center position of the pump plunger. Nevertheless, erroneous metering due to speed changes between the area of the bottom dead center position and the delivery stroke area, which can be proved to occur, can not be avoided, which, in a positive feedback effect, results in a substantially deviating speed adjustment of the internal combustion engine.
In a known distributor-type fuel injection pump (U.S. Pat. No. 4,475,507), control marks are arranged so as to be distributed along the circumference of the pump plunger in the sequence of the pump plunger delivery strokes and cooperate, one after the other, with a stroke position transmitter. In this way, sequential signals are produced which characterize the bottom dead center position of the pump plunger prior to the commencement of its delivery stroke. The switching valve which controls the connection between the pump work space and the relief or low-pressure space is triggered and brought into the closing position by means of these control signals. With the aid of an angular segment transmitter, rotational angle segments are counted in sequence and compared with a reference angle until agreement prevails. After this point, the switching valve is opened again so that the injection is terminated. The reference angle is composed of a pre-stroke angle and an injection angle, both of which are measured from preselected parameters corresponding to a characteristic field. The disadvantage of this control of the switching valve consists in that an accurately manufactured segment wheel must be produced with perfect pulse recognition. In addition, the pulse train or minimum division in angular segments cannot be refined as desired at a reasonable cost, so that the metering accuracy of the fuel injection quantity is limited on the basis of this defined resolution.
ADVANTAGES OF THE INVENTION
The fuel injection pump, according to the invention, is characterized in that a stroke transmitter (36) is provided which determines the stroke path of the pump plunger (14) and transmits to the control device, as an actual delivery stroke signal, the delivery stroke covered by the pump plunger (14) starting from a reference point, in that the actual delivery stroke signal is compared in the control device (34) with a reference signal corresponding to a predetermined plunger stroke of the pump plunger and, on the other hand, with a desired del
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patent: 4462361 (1984-07-01), Karle
patent: 4475507 (1984-10-01), Miyaki
patent: 4576129 (1986-03-01), Wallenfang
patent: 4603669 (1986-08-01), Takemoto
patent: 4706635 (1987-11-01), Draper
patent: 4788960 (1988-12-01), Oshizawa
patent: 4790277 (1988-12-01), Schechter
patent: 4870939 (1989-10-01), Ishikawa
patent: 4884549 (1989-12-01), Kelly
Anton Karle
Werner Pape
Miller Carl S.
Robert & Bosch GmbH
Striker Michael J.
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