TITLE:

A Backflow pipe assembly in a fuel injection system Field of the invention

This invention relates to the field of backflow pipe connector for a fuel injector. Background of the invention

A fuel injector is a part of both low pressure circuit and high pressure circuit in a fuel injection system. The high pressure circuit comprises at least a high pressure pump, accumulator, and the injector adapted to receive pressurized fuel from the accumulator. The injector opens and closes for injecting fuel into the engine cylinder based upon signals from the ECU. The un-injected volume of fuel that is left over in the injector, due to factors like opening & closing of the injector and leakage through clearances, needs to be relieved from the injector to avoid secondary injection and un-necessary pressure build up in the injector so as to prevent damage to the components of the injector. Located in the injector is a back flow path that opens into a pipe leading to a fuel tank. The pressure at which un-injected fuel is relieved back to the fuel tank is generally referred to as back pressure. The back pressure depends upon the dimensions of the pipe, material of the pipe and the like. In the current state of art, the back pressure of fuel, is maintained to an acceptable level by having a check valve/ non-return valve in the fuel return pipe of the low pressure circuit. In order to ensure the stability of the injection quantity over lifetime and for the robustness of the injector for lifetime, there is a need to make the backpressure of the fuel independent of the pipe characteristics.

FIG. 1 illustrates a backflow pipe for a fuel injector 100 used in the state of art. The back flow pipe is a part of low pressure circuit in the fuel injection system. The backflow pipe 106 connects the backflow connector 104 of the injector 100 to the fuel tank 108. The un- injected fuel from the injector 100, is sent back to the fuel tank 108 through the back flow pipe 106. The backflow pipe 106, has a one-way valve (check/ non-return valve) 102 that allows the fuel to flow through the backflow pipe in one direction only, i.e. from the backflow connector to the fuel tank and not the other way. It is observed that, in addition to the backflow valve, the diameter of the pipe and pipe characteristic influence the back pressure of the injector. The back pressure to injector can be affected by the material of the back flow pipe, diameter/length and layout of the low pressure circuit in the fuel injection system.

Brief description of the accompanying drawing

Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

FIG. 1 illustrates a backflow pipe for a fuel injector used in state of art; and FIG. 2 illustrates a backflow pipe assembly in a fuel injection system. Detailed description of the embodiments

FIG. 2 illustrates a backflow pipe assembly 200 in a fuel injection system. The backflow pipe assembly 200 is adapted to send un-injected fuel from an injector to a fuel tank, and comprises at a backflow connector 202 engaged to a back flow outlet of the injector. The backflow connector 202 is removably fitted to the injector in the fuel injection system. A valve 208 is located within the back flow connector 202, the valve 208 is adapted to throttle un-injected fuel received from the backflow outlet 104 of the injector into the backflow pipe 206. The valve 208 is integrated with the backflow connector 202. The valve 208 may also be removably fitted to the back flow connector 202. The valve 208 is a one-way valve, and is at least one, from a combination comprising at least a ball valve, a pin type valve, a pintle valve.

The constructional details of backflow pipe assembly 200 with backflow connectors 202 will now be described in further detail. The backflow pipe assembly 200 with backflow connectors 202 is located in the low pressure circuit of the fuel injection system. The backflow connector 202 is attached to the backflow outlet of the injector 104 and the other end of the backflow pipe connector 202 opens backflow pipe 206. Each injector has such an arrangement, comprising the backflow connector 202 attached to the backflow outlet of the injector (For the purpose of simplicity only one injector with back flow connector is shown in FIG.2). Backflow fuel flow from the injectors via the back flow connector 202 and to the backflow pipe 206 back into the fuel tank. The backflow connector 202 is removably fitted to the backflow pipe 206 in the fuel injection system.

The working of fuel injector 210 with the valve 208 integrated in the backflow pipe connector 202 will now be explained in detail with reference to FIG. 2. The injector 210, receives fuel for injection into the engine cylinder, from the accumulator. The ECU through signals to the injector, decides the quantity of fuel that needs to be injected into the engine cylinder. The injector opens and closes, during fuel delivery. The un-injected fuel generally comprises leakage from injector (clearances in injector components, dead volume) and the control quantity used to enable injection of fuel in the injector. The un-injected fuel flows through the fuel return path present in the injector to reach the backflow outlet of the injector. The function of the fuel return path is to allow un-injected fuel present within the injector to flow back to the backflow pipe 206 present in the low pressure circuit. The valve 208 that is located in the backflow pipe connector 202 throttles un-injected fuel and maintains the required back pressure to the injector, the fuel now flows through the backflow pipe 206 to reach the fuel tank. Since, the valve 208 is a one-way valve, flow of fuel is only possible from the backflow pipe to the fuel tank 220. As the fuel is throttled in the backflow pipe connector 202 itself, the need for a separate valve 102 (as disclosed in the detailed description of FIG. 1) in the back flow pipe 206 is not required anymore (in comparison to FIG.l in state of art). This arrangement largely removes the influence of the low pressure pipe 206, on the injection quantity. Additionally, the requirements on the backflow pipe 206 is reduced in terms of pressure capability and retaining material properties within a close band. By having a separate back flow connector the influence of back flow pipe pressure also referred to a as back pressure can be eliminated in the low pressure circuit. The back flow pipe assembly with the proposed back flow connector gives greater flexibility in designing the low pressure circuit.

It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention in terms of and also the type of valve used. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.