Claims:We Claim:
1. An adaptor (100) for a Compressed Natural Gas (CNG) injector 102; said adaptor 100 located at a delivery end 103 of said injector (102) and adapted to open into an engine cylinder and comprises:
a hollow casing (104), and

a needle (106) located within said hollow casing (104), said needle (106) adapted to be actuated in dependence of the pressure of said gas at said delivery end 103 of said injector 102.

2. The adaptor 100 of claim 1, wherein a spring (108) is located within said hollow casing 104, said spring 108 adapted to bias said needle 106.
, Description:Field of the invention
[0001]This invention relates to the field of compressed natural gas (CNG) based fuel injection system.

Background of the invention
[0002]With the emergence of stringent pollution legislations worldwide and limited availability of fossil fuels, there has been a shift towards the use of alternate type of fuel in automotive engines, like liquefied petroleum gas (LPG) and CNG. Compressed natural gas (CNG) is used due to favorable hydrogen: carbon (H: C) ratio resulting in low emissions. One of the commonly used CNG type fuel injection is the manifold injection system. In the case of manifold injection system maintaining precise control over injection quantity (CNG) with respect to air in each cylinder is critical. Hence, there is a need for ensuring a precise control of injection quantity using the existing CNG injector for meeting emission requirements. The other method used for CNG injection is “direct injection”. In direct injection a CNG injector injects fuel that is gas in this case directly into the engine cylinder. The design of injector for direct injection is complex and hence would prove to a challenge for low cost vehicles using CNG injection.

Brief description of the accompanying drawing
[0003] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[0004] FIG. 1 illustrates an adaptor for a Compressed Natural Gas (CNG) injector; and
[0005] FIGS. 2A-2B illustrate the working of the adaptor.

Detailed description of the embodiments
[0006] FIG. 1 illustrates an adaptor 100 for a Compressed Natural Gas (CNG) injector 102. The adaptor 100 is located at a delivery end 103 of the injector 102 and adapted to open into an engine cylinder (not shown). The adaptor 100 comprises a hollow casing 104 and a needle 106 located within the hollow casing 104. The needle 106 is adapted to be actuated in dependence of the pressure of the gas at the delivery end 103 of the injector 102. In an embodiment a spring 108 is located within the hollow casing 104, the spring 108 is adapted to actuate the needle 106.

[0007]The construction of the adaptor 100 will be explained in further detail. The adaptor 100 disclosed herein is located at the delivery end 103 of the CNG injector 102. The adaptor 100 may be flexibly attached to the delivery end 103 of the CNG injector 102. Alternately, the adaptor 100 may be fixed permanently to the delivery end 103 of the CNG injector 102. The CNG injector 102 receives the fuel in the form of gas from a rail. The rail stores the gas at a pressure that is required for injection into the engine cylinder. The CNG injector 102 comprises an inlet to receive gas and a delivery end 103 allows the gas to flow into the adaptor 100. The adaptor 100 comprises a hollow casing 104 and the needle 106 is located within the hollow casing 104. One end of the needle 106 comprises a protrusion 109. The protruded part of the needle 106 rests against the inner surface of the hollow casing 104.The profile of the needle 106 is such that the movement of the needle 106 in a first direction will cause the fuel to get injected into the engine cylinder as shown in FIG. 2A and the movement of the needle 106 in a second direction will prevent entry of combustion gases into the adaptor 100 and the CNG injector 102 as shown in FIG. 2B.

[0008] FIGS. 2A-2B illustrate the working of the adaptor 100. The CNG (gas) is stored under pressure in a tank. From the tank the CNG flows into a rail via a pressure regulator. The gas enters the CNG injector 102 and reaches the delivery end 103 of the injector 102. During suction stroke of the engine, the pressure of gas at the delivery end 103 of the injector 102 overcomes the spring 108 stiffness causing the needle 106 to open as shown in FIG 2A. The stiffness of the spring 108 is such that the needle 106 opens during the suction stroke of the engine. The protrusion 109 is designed in way such that the movement of the needle 106 causes the protrusion to open the casing 104, thereby causing the gas to flow from the adaptor 100 into the engine cylinder. Upon completion of the suction stroke, the needle 106 moves in a second direction aided by the spring 108 so as to block the flow of gas from the adaptor 100 to the engine as shown in FIG. 2B.

[0009]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 the type of fuel/ gas 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.