Fluid handling – With indicator – register – recorder – alarm or inspection means – Position or extent of motion indicator
Patent
1991-05-14
1992-05-05
Rosenthal, Arnold
Fluid handling
With indicator, register, recorder, alarm or inspection means
Position or extent of motion indicator
25112902, 25112916, 25112904, F16K 3106, F02M 5100
Patent
active
051098857
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention relates to a solenoid valve, in particular for fuel-injection pumps.
When such solenoid valves are used in fuel-injection pumps, they are mounted in the high-pressure channel of the fuel-injection pump and used to control the fuel quantity injected per pump-piston stroke. The closing or operating time of the solenoid valve thereby determines the injection period and, with a given nozzle cross-section, also determines the fuel-injection quantity. The solenoid valves generally have constant switching times, which are constructively determined. Thus, for example, from the time that the electromagnet is no longer triggered until the valve is actually completely opened, there is a time delay in which fuel is still injected Consequently, the end of the fuel-injection phase comes later than the instant that the electromagnet is interrupted, as specified by the control element, by the amount of the constant switching time of the valve when the valve is opened.
In addition, the manufacturing tolerances of the solenoid valves, as well as long-term drift, lead to time differences between the time that the electromagnetic excitation ceases and the time that the solenoid valve actually opens. This negatively effects the capability to correctly meter fuel during the injection phase Therefore, a position signalling device has been provided for these types of solenoid valves. This position signalling device detects the two contact positions of the valve needle, namely when it contacts the valve seating (valve closed) and when it strikes against the stroke-limit stop (valve fully opened). When one has knowledge of these valve-needle contact positions, the injection fuel quantity can be very precisely dosed.
A known solenoid valve for a fuel-injection pump of the type mentioned at the outset (DE 36 33 107 Al) has a position signalling device with a disk of piezoelectric ceramic material, which is integrated in the strokelimit stop. When the solenoid valve is opened after the electromagnetic excitation has ceased, the valve needle lifts off from the valve seating under the effect of the valve-opening spring and hits the piezoelectric ceramic disk. In this manner, a voltage is generated which is fed as a valve-opening signal to the control element and is evaluated there accordingly. To this end, the two electrical outputs of the piezoelectric ceramic disk are connected to a double-conductor cable which passes as an insulated cable through the valve housing. This entails additional processing steps for the valve housing, an additional electrical connecting line to the electrical connection for the electromagnetic excitation coil, and additional expenditure for assembly.
ADVANTAGES OF THE INVENTION
In contrast, the solenoid valve according to the invention has the advantage that the electric signal, which is generated by the piezoelectric ceramic when the valve needle strikes, is transmitted to the control element without entailing any additional transmission length. As a result of the measures according to the invention, one can use the double-conductor connecting line for this, as it is available and required anyway. It can be arranged between the control element and the electromagnetic excitation winding, which serves to trigger the electromagnets. If the electromagnetic excitation is interrupted, as occurs when the circuit element, which is generally designed as a transistor final stage in the control element, is opened, then the feedback conductor of the double-conductor connecting line is uncoupled from ground.
The charges produced when the valve needle hits the piezoelectric ceramic lead to a voltage pulse in the parasitic capacitors of the diode connected in series to the excitation winding of the power transistors of the control element, and of the connecting line between the control element and the electromagnets. This voltage pulse can be tapped at the output terminal of the control element connected to the feedback conductor. This voltage pulse represents a signal for recognizing the valv
REFERENCES:
patent: 4628885 (1986-12-01), Ogburn et al.
Robert & Bosch GmbH
Rosenthal Arnold
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