Claims:We Claim:
1 A delivery valve (200) in a fuel pump, said delivery valve (200) comprising:
a delivery valve body (205) having an axial bore (210); and
a valve pin (215) mounted in said axial bore (210) of said delivery valve body (205) and movable between a first position and a second position, said first position corresponds to a fuel flow path being open such that high pressure fuel flows out of said delivery valve body (205) and said second position corresponds to said fuel flow path being blocked;
characterized in that
said valve pin (215) having a valve bore (220), said valve bore (220) housing a valve assembly for enabling back pressure fuel to flow into said delivery valve body (205) through said valve bore (220) when said valve pin (215) is in said second position.

2 The delivery valve (200) as claimed in claim 1, wherein said valve bore (220) defines a return flow path for enabling said back pressure fuel to flow into said delivery valve body (205).

3 The delivery valve (200) as claimed in claim 1 and claim 2, wherein said return flow path has a cross-sectional area lesser than said fuel flow path.

4 The delivery valve (200) as claimed in claim 1, wherein said valve assembly in said valve pin (215) comprising:
a ball member (230) arranged in said valve bore (220) of said valve pin (215), said ball member (230) movable between an open position and a closed position;
a spring member (240) in contact with said ball member (230) at one end and located within said valve bore (220), said spring member (240) is compressed when said ball member (230) is in said open position; and
a plug (243) assembled within said valve bore (220) and located at second end of said spring for enabling said back pressure fuel to flow out of said delivery valve (200) when said ball member (230) is in said open position.

5 The delivery valve (200) as claimed in claim 1, wherein said valve bore (220) defining a valve seat for movably seating a ball member (230).

6 The delivery valve (200) as claimed in claim 4, wherein said plug (243) comprises an orifice for enabling flow of said back pressure fuel out of said delivery valve (200) when said ball member (230) is in said open position.
, Description:Field of the invention:
[0001] The invention relates to a delivery valve in a fuel pump.

Background of the invention:
[0002] Fuel pump is an essential element for an automobile with diesel engine. Fuel pump is used for pressurizing fuel before the pressurized fuel is injected by a fuel injector. Main components of a fuel pump include a plunger-barrel assembly and a delivery valve assembly. The fuel is pressurized by the reciprocatory movement of the plunger within the barrel. Pressurized fuel is delivered to the fuel injector through the delivery valve assembly. The delivery valve assembly comprises numerous components such as a delivery valve body, a delivery valve holder, throttle plate, filler piece, delivery valve pin and a spring member as shown in Figure 1. However, due to large number of components involved in the delivery valve assembly, pressure of the pressurized fuel drops as it passes through these components. This is an undesirable situation because as the fuel pressure drops, combustion efficiency decreases. In order to avoid the drop in fuel pressure, some components, for example throttle plate, the filler piece which are a part of the delivery valve assembly may be removed. However, when these components are removed, the back pressure fuel will not be dampened. Such back pressure fuel causes cavitation effect and secondary injections. Hence there is a need for a delivery valve which enables dampening of the back pressure fuel and also reduces drop in the fuel pressure.

Brief description of the accompanying drawings:
[0003] Figure 1 illustrates a delivery valve assembly in a fuel pump, in accordance with a prior art;
[0004] Figure 2 illustrates a delivery valve in a fuel pump, in accordance with an embodiment of the invention; and
[0005] Figure 3 illustrates a delivery valve assembly in a fuel pump, in accordance with an embodiment of the invention.

Detailed description of the embodiments:
[0006] Figure 1 illustrates a delivery valve assembly (100) in a fuel pump, in accordance with a prior art. The delivery valve assembly (100) comprises a delivery valve body (12) and a delivery valve holder (14). The delivery valve body (12) has a bore which has a valve seat (16). The bore houses a valve pin (18) which comprise flute-like structures for enabling flow of fuel. The delivery valve holder (14) also comprises a central bore that houses numerous components such as, a first spring (22), a support element (20), a throttle plate holder (24), a throttle plate (26), a filler piece (32) and a second spring (30).
[0007] Pressurized fuel flows from the plunger-barrel assembly into the bore of the delivery valve body (12). The pressure of the pressurized fuel, lifts the valve pin (18) away from its valve seat (16) and compresses the first spring (22). Further, as the valve pin (18) lifts, the valve pin (18) comes in contact with the support element (20) enabling fuel to flow through a central hole in the support element (20) and then along a central hole of the throttle plate holder (24). The direction of the pressurized fuel causes the throttle plate (26) to be positioned away from the throttle plate holder (24). The throttle plate (26) being away from the throttle plate holder (24) causes the fuel to flow along grooves (32a) in the filler piece (32). The pressurized fuel flows along the grooves (32a) in the filler piece (32) and then reaches the central bore of the delivery valve holder (14). The pressurized fuel then flows out of the delivery valve assembly through the central bore of the delivery valve holder (14) and reaches a fuel injector.
[0008] The back pressure fuel from the fuel injector flows back into the delivery valve assembly through the central bore of the delivery valve holder (14) and strikes the throttle plate (26). Pressure of the back pressure fuel pushes the throttle plate (26) towards the throttle plate holder (24) and hence the back pressure fuel is forced to flow through a central bore in the throttle plate (26) along the filler piece (32) and the support element (20) and then reaches the valve pin (18). As the back pressure fuel flows through this path, pressure waves in the back pressure fuel are dampened. Dampening of the back pressure fuel is essential to avoid secondary injections and cavitation effects in components of the fuel pump.
[0009] However, for achieving such dampening of the pressure waves, numerous components are required to be assembled in the delivery valve holder (14). Due to such numerous components being present in the delivery valve holder (14), as the pressurized fuel flows through the delivery valve, the pressure drops when it comes in contact with the numerous components assembled in the delivery valve holder (14). Such drop in fuel pressure is undesirable because when fuel is injected at such reduced pressure, the combustion efficiency decreases. Hence, there is a need for a delivery valve which minimizes the number of components in order to minimize pressure loss in the pressurized fuel in addition to dampening of the pressure waves in the back pressure fuel.
[0010] Figure 2 illustrates a delivery valve (200) and Figure 3 illustrates a delivery valve assembly (300) in a fuel pump, in accordance with an embodiment of the invention.
[0011] The delivery valve (200) comprises a delivery valve body (205) having an axial bore (210), a valve pin (215) mounted on the axial bore (210) of the delivery valve body (205) and is movable between a first position and a second position. The first position corresponds to a fuel flow path being open such that high pressure fuel flows out of the delivery valve body (205) and the second position corresponds to the fuel flow path being blocked. The delivery valve (200) is characterized by a valve pin (215). The valve pin (215) has a valve bore (220). The valve bore (220) houses a valve assembly for enabling back pressure fuel to flow into the delivery valve body (205) through the valve bore (220) when the valve pin (215) is in the second position.
[0012] The structure of the delivery valve (200) in accordance with an embodiment of this disclosure is explained in detail in the below paragraphs.
[0013] The delivery valve (200) comprises a delivery valve body (205). The delivery valve body (205) defines the axial bore (210) that houses the valve pin (215). The axial bore (210) of the delivery valve body (205) also defines a valve seat (235) for movably seating the valve pin (215).
[0014] The delivery valve (200) further comprises a delivery valve holder (245) (shown in Figure 3) where axial bore (210) is extended to the delivery valve holder (245). Within the axial bore (210) of the delivery valve holder (245), a plug (243) and a spring arrangement is assembled as shown in Figure 2. A groove (225) is defined along the axis of the plug (243) for enabling flow of back pressure fuel to flow into the delivery valve body (205).
[0015] The valve pin (215) is a metallic valve element that is movable between a first position and a second position. In the first position, the valve pin (215) is away from the valve seat (235) and this corresponds to opening of the fuel flow path so that the high pressure fuel flows out of the delivery valve body (205). In the second position, the valve pin (215) is seated on the valve seat (235) and this corresponds to blocking of the fuel flow path.
[0016] The valve pin (215) is characterized by the valve bore (220) shown in Figure 2. Orientation of the valve bore (220) is axial with respect to the valve pin (215). The valve bore (220) along with the groove (225) defined along the axis of the plug (243) forms a return flow path for enabling back pressure fuel to flow into the delivery valve body (205) when the valve pin (215) is in the second position. It should be noted that, the cross sectional area of the return flow path is lesser than the fuel flow path. Hence, quantity of back pressure fuel flowing into the delivery valve body (205) is lesser than the quantity of high pressure fuel flowing out of the delivery valve body (205).
[0017] The valve bore (220) houses a valve assembly. The valve assembly comprises a ball member (230) located in the valve bore (220). The valve bore (220) defines a valve seat for movably seating the ball member (230). The ball member (230) is movable between an open position and a closed position. The open position corresponds to opening of the return flow path so that the back pressure fuel flows into the delivery valve body (205) and the closed position corresponds to the return flow path spring being blocked.
[0018] The valve assembly also comprises a spring member (240) arranged in the valve bore (220). One end of the spring member (240) is in contact with the ball member (230). The spring member (240) is a compression spring and has an opening pressure. When the back pressure fuel striking the ball member (230) is equal to or greater than the opening pressure of the spring member (240), the spring member (240) gets compressed and the ball member (230) moves to the open position. When no back pressure fuel strikes the ball member (230), the spring member (240) regains its original position which is the closed position.
[0019] The valve assembly also includes a plug (243) that is assembled in the valve bore (220). The plug (243) is located at second end of the spring member (240). The plug (243) has the groove (225) that allows back pressure fuel to flow into the delivery valve body (205) when the ball member (230) is in open position.
[0020] The working of the delivery valve (200) is explained in detail in the following paragraphs in conjunction with Figure 2 and Figure 3.
[0021] Initially, when no pressurized fuel is present in the fuel pump, the valve pin (215) is seated on the valve seat (235) of the delivery valve body (205).
[0022] Fuel from the fuel tank flows into the plunger-barrel assembly of the fuel pump through an inlet of the fuel pump. The fuel is pressurized by the movement of the plunger within the plunger-barrel assembly. The pressurized fuel is then delivered to the fuel injector through the delivery valve (200). The barrel in the plunger-barrel assembly opens into the axial bore (210) of the delivery valve body (205) of the delivery valve (200) and hence the pressurized fuel from the plunger-barrel assembly flows into the axial bore (210) of the delivery valve body (205).
[0023] The axial bore (210) of the delivery valve body (205) defines a valve seat (235) so that the valve pin (215) is movably seated. When pressure of the fuel flowing in the axial bore (210) of the delivery valve body (205) is beyond a pre-defined threshold, the valve pin (215) that is seated on the valve seat (235) is moved to first position. When the valve pin (215) is being moved to the first position (the valve pin (215) is lifted from the valve seat (235)), the fuel flow path is opened. Further, the spring (250) shown in Figure 3 arranged within the axial bore (210) of the delivery valve holder (245) is compressed when the valve pin (215) is lifted thereby enabling opening of the fuel flow path. Movement of the valve pin (215) to the first position causes the valve pin (215) to come in contact with a filler piece. The pressurized fuel flows along the fuel flow path through the filler piece and then flows out of the delivery valve body (205) reaching the fuel injector.
[0024] When the flow of pressurized fuel is stopped, the valve pin (215) returns to the valve seat (235) and is now considered to be in second position. When the valve pin (215) is in the second position, the fuel flow path is blocked and pressurized fuel does not flow out of the delivery valve body (205).
[0025] Once the pressurized fuel reaches the fuel injector, the fuel is injected into an engine cylinder. Due to high pressures, some quantity of fuel flows back from the fuel injector to the delivery valve (200). This is called as back pressure fuel. The back pressure fuel flows into the delivery valve (200) through the delivery valve holder (245) along the groove (225) of the plug (243) and then through the valve bore (220) of the valve pin (215) and strikes the ball member (230).
[0026] When pressure of the back pressure fuel is equal or greater than the opening pressure of the spring member (240) arranged in the valve bore (220), the spring member (240) is compressed and the ball member (230) moves to open position (the ball member (230) moves away from the valve seat). The ball member (230) being in the open position corresponds to opening of the return flow path. The back pressure fuel flows along the axis of the valve bore (220) and flows through the orifice of the plug (243) arranged in the valve bore (220). The flow of the back pressure fuel is indicated using arrows as shown in Figure 2. The back pressure fuel flowing through the orifice of the plug (243) flows back to the plunger-barrel assembly. Therefore, as the back pressure fuel flows along the return flow path, the pressure waves in the back pressure fuel is dampened thereby minimizing secondary injections and cavitation effects in the components of the fuel pump.
[0027] When no back pressure fuel flows into the delivery valve (200), the ball member (230) is in closed position (the ball member (230) is seated on the valve seat). This closes the return flow path. It should be noted that, the return flow path is opened only when the fuel flow path is blocked.
[0028] Hence, a delivery valve (200) with minimum number of components so that the pressurized fuel flows through the delivery valve (200) with minimal pressure loss when the fuel is flowing to the fuel injector in addition to dampening of pressure waves in the back pressure fuel when the fuel is flowing from the fuel injector is disclosed. In the present design of the delivery valve (200), the throttle plate (26), and throttle plate holder (24), the support element (20) and the second spring (30) is eliminated. Such reduction in components results in reduced pressure drop of the pressurized fuel flowing out of the delivery valve (200) with thereby increasing the combustion efficiency. Further, the valve pin (215) is designed to house a valve assembly that defines a return flow path for the flow of back pressure fuel. Such an arrangement in the valve pin (215), enables dampening of the pressure waves in the back pressure fuel to reduce secondary injection and cavitation effects in the fuel pump.
[0029] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. 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.