MONONEN REIJO (FI)
| US2944535A | 1960-07-12 | |||
| US4483181A | 1984-11-20 | |||
| US4606312A | 1986-08-19 | |||
| DE1751543A1 | 1970-08-27 |
| 1. | A method for controlling the injection of fuel into the combustion chamber of an internal combustion engine, in which method the pressure of a combustion chamber is sensed by means of a piezoelectric transducer (6) sensing the tensile stress of fastening bolts 4 for a cylinder cover 3 defining a combustion chamber or by means of a strain gauge transducer (61 ), c h a r a c t e r i z e d in that the timing and rate of injection of a fuel to be injected into the combustion chamber of a freepiston engine are controlled in real time in connection with each individual injection depending on a signal from said transducer (6) . |
| 2. | A method as set forth in claim 1, c h a r a c t e r ¬ i z e d in that said signal from the transducer (6) is combined in a control unit (7) controlling the injection of fuel with a signal representing the loading output of an engine. |
| 3. | An apparatus for controlling the injection of fuel into the combustion chamber of an internal combustion engine, said apparatus comprising a piezoelectric transducer (6), which is in contact with a fastening bolt (4) for a cylinder cover (3) defining a combustion chamber and which is connected to a fuel injection control unit (7) for delivering to the control unit (7) a signal depending on the tensile stress of said fastening bolt (4), c h a r a c t e r i z e d in that the control unit (7) is connected to a piezoelectric actuator (9), which controls the opening of the needle of a fuel injection nozzle (8), said injection nozzle (8) being adapted to feed fuel into the combustion chamber of a freepiston engine. |
In conventional crankshaft engines, the control over the injection of fuel is typically obtained by using a mechanical cam for operating a fuel pump. The cam design is used to determine a pressure diagram for the pump and this, in turn, controls opening of the needle. With this arrangement, it is not possible to take into consideration the fluctuations of a load and a combustion pressure in the regulation of an injection rate until after a substantial delay. However, in terms of controlling the operation of e.g. a free-piston engine, it is essentially important that the engine control unit be capable of sensing the loading and combustion process in real time and maintaining the fuel injection under control with no delay. This object is achieved by means of a method and apparatus of the invention on the basis of the characterizing features set forth in the annexed claims.
The invention will now be described in more detail with reference made to the accompanying drawing which illustrates a mechanism of the invention.
A cylinder 1 houses a moving engine piston 2, which together with a cylinder cover 3 defines a combustion chamber. The cover 3 is fastened in a conventional fashion by means of fastening bolts 4, the top end of just one being shown. A washer 6 placed underneath a nut 5 included in the bolt 4 is in fact a piezoelectric transducer, whose output signal depends on the tensile stress of said bolt 4.
The piezoelectric transducer 6 is linked to a fuel
injection control unit 7 which in turn is connected to a piezoelectric actuator 9. The actuator 9 controls opening of the needle of an injection nozzle 8 on the basis of a control signal received from the control unit 7.
The piezoelectric transducer 6 enables the control unit 7 to sense a loading and combustion process in real time and to maintain the fuel injection under control with no delay. A signal from the transducer 6 contains a messaage about the rising rate of the pressure of an individual compression stroke. If, for example, in the case of a free-piston engine, the pressure rising rate is too fast, it is possible to previously inject a small amount of fuel for stopping the piston 2 and preventing a gable-hitting stroke. The actual injection can also be dimensioned to be lesser than the preceding injection considering, of course, the present loading. In particular, however, the arrangement makes it possible to monitor the combustion pressure immediately after the injection, so that the fluctuations of injection and combustion pressure follow the fluctuations of loading with no delay.
The use of washer transducers 6 of the invention is simple with normal fastening bolts. Neither is the transducer 6 subjected to high temperatures, which is the case with transducers placed e.g. in a combustion chamber.
A piezoelectric transducer can also be fitted in some other way in connection with fastening bolts 4 to obtain a signal proportional to the combustion pressure from the strain of fastening bolts 4. The actuator 9 controlling the opening of the needle of injection nozzle 8 can also be a solenoid valve, as described in US Patent publication 4,628,881.
Although the invention is suitable for use in all types of internal combustion engine, wherein the feeding of fuel is effected by injection, the invention is particularly useful in connection with a free-piston engine. One example of a free-piston engine, in which the invention can be applied, has been described in Patent publication FI-80760.