Fuel supply systems

1. A fuel supply system comprising:

a fuel pump capable of supplying fuel stored within a fuel tank to a fuel injecting valve device of an engine;

a pressure regulator including a pressure regulating chamber, into which a part of the fuel supplied from the fuel pump to the fuel injecting valve device can be introduced, and a back pressure chamber, into which a part of the fuel pressurized by the fuel pump can be introduced,

wherein a pressure of the fuel within the pressure regulating chamber can be regulated according to a back pressure produced within the back pressure chamber, and surplus fuel not to be used within the pressure regulating chamber can be discharged from the pressure regulator;

a change-over device configured to be able to change between a fuel introduction state for introducing the fuel into the back pressure chamber of the pressure regulator and an atmospheric pressure introduction state for introducing an atmospheric pressure into the back pressure chamber of the pressure regulator, so that a system fuel pressure of the fuel supplied to the fuel injecting valve device can be changed by the change-over device;

a check valve arranged in a fuel supply path leading from the fuel pump to the fuel injecting valve device, the check valve being positioned on an upstream side of a first diverting point in the fuel supply path, from which the fuel is introduced into the pressure regulating chamber of the pressure regulator; and

an outflow prevention device capable of preventing outflow of the fuel within the back pressure chamber of the pressure regulator when the engine is stopped while the system fuel pressure being heightened.

2. The fuel supply system as in claim 1 , further comprising:

an upstream side path diverged from the fuel supply path at a second diverting point positioned on an upstream side of the check valve, so that a part of the fuel is introduced into the back pressure chamber of the pressure regulator via the upstream side path;

wherein the outflow prevention device comprises a check valve arranged in the upstream side path at a position on an upstream side of the change-over device and capable of preventing backflow of the fuel.

3. The fuel supply system as in claim 1 , wherein the outflow preventing device comprises a valve device capable of opening and closing a path leading from the back pressure chamber of the pressure regulator to the change-over device.

4. The fuel supply system as in claim 1 , wherein the outflow preventing device comprises a valve device capable of opening and closing an atmospheric side path of the change-over device.

5. A fuel supply system comprising:

a fuel pump capable of supplying fuel stored within a fuel tank to a fuel injecting valve device of an engine;

a pressure regulator including a pressure regulating chamber, into which a part of the fuel diverted from a first diverting point in a fuel supply path leading from the fuel pump to the fuel injecting valve device can be introduced, and a back pressure chamber, into which a part of the fuel diverted from a second diverting point in the fuel supply path on a downstream side of the first diverting point can be introduced,

wherein a pressure of the fuel within the pressure regulating chamber can be regulated according to a back pressure produced within the back pressure chamber, and surplus fuel not to be used within the pressure regulating chamber can be discharged from the pressure regulator;

a change-over device configured to be able to change between a fuel introduction state for introducing the fuel into the back pressure chamber of the pressure regulator and an atmospheric pressure introduction state for introducing an atmospheric pressure into the back pressure chamber of the pressure regulator, so that a system fuel pressure of the fuel supplied to the fuel injecting valve device can be changed by the change-over device;

a check valve arranged in the fuel supply path at a position on a downstream side of the second diverting point for the back pressure chamber and capable of preventing backflow of the fuel;

a bypass path connected to the fuel supply path to bypass the check valve;

wherein the change-over device includes a change-over valve;

wherein the change-over valve is capable of allowing flow of the fuel through the bypass path when an atmospheric pressure is introduced into the back pressure chamber;

wherein the change-over valve is capable of preventing flow of the fuel through the bypass path when the fuel is introduced into the back pressure chamber; and

wherein the change-over valve is capable of preventing flow of the fuel through the bypass path when the engine is stopped while the system fuel pressure being heightened.

6. A fuel supply system comprising:

a fuel pump capable of supplying fuel stored within a fuel tank to a fuel injecting valve device of an engine;

a pressure regulator including a pressure regulating chamber, into which a part of the fuel supplied from the fuel pump to the fuel injecting valve device can be introduced, and a back pressure chamber, into which a part of the fuel pressurized by the fuel pump can be introduced,

wherein a pressure of the fuel within the pressure regulating chamber can be regulated according to a back pressure produced within the back pressure chamber, and surplus fuel not to be used within the pressure regulating chamber can be discharged from the pressure regulator;

a change-over device configured to be able to change between a fuel introduction state for introducing the fuel into the back pressure chamber and an atmospheric pressure introduction state for introducing an atmospheric pressure into the back pressure chamber of the pressure regulator, so that a system fuel pressure of the fuel supplied to the fuel injecting valve device can be changed by the change-over device;

a check valve arranged in a fuel supply path leading from the fuel pump to the fuel injecting valve device to prevent backflow of the fuel, the check valve being positioned on a downstream side of a diverting point in the fuel supply path, from which the fuel is introduced into the pressure regulating chamber of the pressure regulator, so that the system fuel pressure can be heightened when the engine is stopped.