From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Technical article detailing the design and operation of an actuated fuel injection valve and its associated systems.
| Identifier | ExFiles\Box 158\5\ scan0035 | |
| Date | 22th April 1939 | |
| 531 Actuated Fuel Injection Valve release and cut-off, the penetration as a function of time, and the form of the spray could be observed. The stroboscope was timed by a rotating switch consisting of a spark gap, one side of which was mounted on a graduated disk which could be rotated to any desired position, while the other side was mounted on a rotating disk. The rotating disk was attached to the motor shaft, which also operated the breaker points to charge and discharge the condensers operating the magnetically-actuated valve. The same motor operated the fuel pump for the jerk-pump system. The fuel system consisted of a container mounted on a torsion balance. Fuel was drawn from the container by a transfer pump and passed through a filter. After leaving the filter, the fuel could be passed either to the jerk-pump or the high-pressure fuel pump for the common-rail system of the magnetically-actuated valve. The common-rail system consisted of a single-cylinder, high-pressure fuel pump which delivered the fuel at a pressure of 4000 lb. per sq. in. to a small chamber. The chamber was connected to the nozzle with a fuel line 6 in. long having an internal diameter of 0.06 in. The chamber was also connected to a pressure regulator by means of which the pressure could be maintained constant at any desired value between 1000 and 4000 lb. per sq. in. With the aid of a revolution counter attached to the system, the average weight of fuel injected per cycle was obtained. The magnetically actuated valve was controlled by a bank of four condensers connected in parallel. By using various combinations of condensers, better control for test purposes could be obtained than if a variable resistance had been used in the charging circuit. The electrical characteristics of the system, with and without variable resistance, were studied with the aid of an R.{Sir Henry Royce} C. A.{Mr Adams} 3-in. cathode-ray oscillograph equipped with a No. 908 tube having a blue screen. Fig. 3. Wiring diagram for a spark ignition engine equipped with magnetically actuated spray valves Fuel Valve The magnetic type of spray valve derives its actuating force from the magnetic attraction of a series of small electro-magnets. The construction of the valve is shown in Fig. 1. The valve consists of 12 iron laminations alternated with non-magnetic laminations. The hollow core through which the needle passes consists of a similar set of laminations. Forty turns of No. 20 copper wire constitute the magnetizing coils, which pass through the shell laminations. The coils are placed in such manner that current flowing through them will produce alternate north and south poles around the circumference of the wire, thus inducing opposite poles in the plunger laminations, as indicated in Fig. 2A. This construction is similar to the field-pole arrangement on a direct-current motor. The laminations on the plunger are displaced toward the valve tip with respect to the frame laminations when the valve is closed. When the circuit through the field coils is completed the resulting current produces a magnetic flux (Fig. 2B) which in turn develops a force tending to lift the valve from its seat. In order to lift the needle as rapidly as possible, the plunger is allowed to move freely for 0.005 in. before striking the collar on the needle. As the current in the coil increases, a critical point is reached where the magnetic pull, and the inertia of the plunger, overbalance the combined force of the spring and oil pressure, and the plunger then moves to a position in which the laminations of the plunger and frame are in the same plane (Fig. 2C). At this position the valve is open and the needle has lifted a maximum distance of 0.028 in. The plunger and frame laminations will remain in the same plane, and thus the valve remains open, until the current and the magnetic flux decrease to a value which no longer balances the combined force of the oil and spring. The closing current is less than the opening current, due to the decreased magnetic reluctance and a small hysteresis in the iron. Among the desired operating characteristics of an injection valve are ease of control and ability to inject Automotive Industries | ||