Injection Volume Outline of SPV
There are two types of SPV (Spill Control Valve) that control the injection volume.
Conventional type SPV
(used in axial plunger type pump)
Direct-acting type SPV
(used in the radial plunger type pump for high-pressure applications)
Conventional Type SPV
The conventional type SPV consists of two valves: main valve and pilot valve.
At normal condition
The pilot valve of the SPV is normally closed, as electricity runs through the coil. The fuel pressure and the spring force causes the main valve to close passage “A” as well, due to the pressure from the inside of the valve being greater than that of the outside of the valve.
When the signal from the engine ECU is turned off
When the signal from the ECU turns off, causing the current applied to the coil to turn off, the pilot valve moves upward by the force of the pilot spring, causing passage “B” to open.
When the pilot valve is opened
Then, the pressure that is applied above the main valve decreases. As a result, the main valve ascends, causing passage “A” to open.
Direct-acting Type SPV
In contrast to the conventional type SPV, the direct-acting type SPV, which is fitted in a pump with a higher fuel pressure, achieves high levels of response and spill characteristics. Furthermore, the signals from the ECU are amplified by the EDU to operate the valve at a high voltage of approximately 150V when closing the valve. Thereafter, the valve remains closed at a low voltage.