CLIAMS:We Claim
1 A fuel pump (100) comprising:
a pumping chamber (105);
a plunger (110);
an inlet port (107) and
an inlet flow path (109) in flow communication between said inlet port (107) and said pumping chamber (105);
characterized in that
a control valve located in said inlet port (107), said control valve comprising:
an inlet line (120) for supplying fuel from a fuel tank to said pumping chamber (105) and an overflow line (125) for returning fuel from said pumping chamber (105) to said fuel tank;
a valve piston (130), said valve piston (130) extending from said inlet port (107) into said inlet flow path (109), at least a part of said valve piston (130) in contact with a valve seat (135) defined by said inlet flow path (109) in an operative closed position for said valve piston (130); and
an actuator located proximate to said valve piston (130) and adapted to control movement of said valve piston (130) between an operative open position and an operative close position.

2 The fuel pump (100) as claimed in claim 1, comprising a gallery (145) formed between said control valve and said inlet port (107) of the fuel pump for storing fuel flowing into said pumping chamber (105).

3 The fuel pump (100) as claimed in claim 1, wherein one end of said inlet flow path (109) proximate to said valve piston (130) is provided with a step portion (140) forming said valve seat (135) for the part of said valve piston (130) which extends into said inlet flow path (109) such that said plunger (110) does not strike said valve piston (130) when said plunger (110) is reciprocating within said pumping chamber (105).

4 The fuel pump (100) as claimed in claim 1, wherein said valve piston (130) is operated to be in an operative open position for supplying fuel from a gallery (145) to said pumping chamber (105).

5 The fuel pump (100) as claimed in claim 1, wherein said valve piston (130) is operated to be in an operative open position for returning fuel from said pumping chamber (105) to a gallery (145).

6 The fuel pump (100) as claimed in claim 1, wherein said valve piston (130) is operated to be in an operative close position during pumping of the fuel from said pumping chamber (105) into a high pressure rail.

7 The fuel pump (100) as claimed in claim 1, wherein said actuator is an electromagnetic actuator.

8 The fuel pump (100) as claimed in claim 5, wherein said electromagnetic actuator is a solenoid.

9 The fuel pump (100) as claimed in claim 1, wherein at least a part of said inlet line (120) of said control valve and at least a part of said overflow line (125) of said control valve are common. ,TagSPECI:Complete specification: The following specification particularly describes the invention and the manner in which it is to be performed.

Field of the invention
[001] This invention relates to fuel pump.

Background of the invention
[002] A fuel pump is a component of the fuel injection system for pumping high pressure fuel from a fuel tank into a combustion chamber. A plunger adapted to reciprocate within a pumping chamber of the fuel pump enables pressurizing of the fuel. A metered quantity of fuel is supplied to the fuel pump and a fuel metering unit is used for such metering of the fuel that is supplied to the fuel pump.

[003] The fuel metering unit meters the quantity of fuel entering into the fuel pump based on current supplied by a controller. The fuel metering unit is a separate component in a fuel injection system that is assembled in the fuel injection system. The fuel metering unit should be designed so that it is compatible with other components of the fuel injection system. Therefore, care should be taken during the manufacturing of the fuel metering unit so that its design is such that it is compatible with other components of the fuel injection system. In order to avoid this problem, the fuel metering unit is integrated into the fuel pump. Such integration of the fuel metering unit reduces the need to maintain a particular design of the fuel metering unit so that it is compatible with other components of the fuel injection system. Also, cost of manufacturing a separate fuel metering unit is reduced. Further the cost of assembling the fuel metering unit in the fuel injection system reduces since it is integrated into the fuel pump

[004] An US patent, US 6446606 describes a fuel pump with an integrated fuel metering unit.

Brief description of the accompanying drawings
[005] Figure 1 illustrates a fuel pump in accordance with an embodiment of the present disclosure; and

[006] Figure 2 illustrates a fuel pump with an altered arrangement of a spring in a solenoid valve in accordance with an embodiment of the present disclosure.

Detailed description
[007] Figure 1 fuel pump 100 in accordance with an embodiment of the present disclosure.

[008] The fuel pump 100 comprises a pumping chamber 105, a plunger 110, an inlet port 107 and an inlet flow path 109. The fuel pump 100 is further characterized by a control valve located in said inlet port 107 and comprising an inlet line 120 for supplying fuel from a fuel tank to the pumping chamber 105 and an overflow line 125 for returning fuel from the pumping chamber 105 to the fuel tank. The control valve further comprises a valve piston 130 extending from the inlet port 107 into the inlet flow path 109. At least a part of the valve piston 130 is in contact with a valve seat 135 defined by the inlet flow path 109 in an operative closed position for the valve piston 130. The control valve also comprises an actuator located proximate to the valve piston 130 and adapted to control movement of the valve piston 130 between an operative open position and an operative close position.

[009] Low pressure fuel from the fuel tank is pumped by a feed pump. The control valve comprises an inlet line 120. The low pressure fuel pumped by the feed pump passes through the inlet line 120 of the control valve. In the inlet line 120 is present a first non-return valve 102. The first non-return valve 102 can be a spring loaded valve. The first non-return valve 102 is usually a zero pressure valve that allows fuel to flow from the fuel tank to the gallery 145. The gallery 145 is a volume of space formed between the control valve and the inlet port 107 of the fuel pump 100 for storing fuel flowing into the pumping chamber 105. The low pressure fuel flowing from the inlet line 120 is stored in the gallery 145 and further is supplied to the pumping chamber 105. Also, in the fuel pump 100 disclosed in this disclosure the control valve is designed such that at least a part of the inlet line 120 of the control valve and at least a part of the overflow line 125 of the control valve are common.

[0010] The control valve also comprises a valve piston 130 that is movable between an operative open position and an operative closed position by the actuator. In the present disclosure the actuator is an electromagnetic actuator for moving the between the operative open position and the operative close position. However it should be noted that the actuator is not limited to only electromagnetic actuator and various other actuators that are capable of moving the piston between the operative open and close position can be used in place of the electromagnetic actuator. In this disclosure, the electromagnetic actuator is a solenoid valve.

[0011] In this disclosure, the valve piston 130 is seated on a valve seat 135 when current is not supplied to the solenoid valve. The valve piston 130 being seated on the valve seat 135 corresponds to the valve piston 130 being in the operative close position. The valve seat 135 is a stationary solid seat that is defined by the inlet flow path 109 of the fuel pump 100. In one example, the valve seat 135 may be conical shaped seat. In the operative close position, the valve piston 130 is pressed against the valve seat 135. However, it should be noted that the shape of the valve piston 130 is not limited to conical shape and the valve seat 135 can be of various other shapes. The housing of the fuel pump 100 is subjected to machining process for defining the valve seat 135 at the inlet flow path 109 of the fuel pump 100. At one end of the inlet flow path 109 proximate to the valve piston 130 is provided with the step portion 140. One part of the step portion 140 is formed from the valve seat 135 and extending into the inlet flow path 109 so that the plunger 110 does not strike the valve piston 130 when the plunger 110 is reciprocating within the pumping chamber 105.

[0012] Normally, the valve piston 130 remains in the operative close position when a controller does not supply current. When no current is supplied a spring 104 in the solenoid valve is not energized. The spring 104 may be a compression spring. When the spring 104 is not energized, the valve piston 130 is seated on the valve seat 135. The valve piston 130 being in the operative close position shuts off a flow path between the gallery 145 and the pumping chamber 105 thereby preventing fuel stored in the gallery 145 from flowing into the pumping chamber 105.

[0013] When current is supplied to the solenoid valve, the solenoid valve is energized and spring 104 is compressed. When the solenoid valve is energized, it pushes the valve piston 130 away from the valve seat 135. The valve piston 130 being away from the valve seat 135 corresponds to the valve piston 130 being in the operative open position. When the valve piston 130 is away from the valve seat 135, a flow path is formed between the gallery 145 and the pumping chamber 105. Hence, the fuel flows from the gallery 145 into the pumping chamber 105 when the valve piston 130 is in the operative open position.

[0014] Operation of the fuel pump 100 with the control valve integrated is explained in the below paragraphs.

[0015] In first case, when the plunger 110 is moving from TDC to BDC, the controller supplies current to the solenoid valve. The controller determines that plunger 110 is moving from TDC to BDC based on a CAM angle of the fuel pump 100 and the lift of the plunger 110 from the BDC. CAM angle of the fuel pump 100 and the lift of the plunger 110 at each engine operating condition are stored in memory of the controller. Energizing the solenoid valve causes the valve piston 130 to be in the operative open position thereby allowing fuel to flow from the gallery 145 into the pumping chamber 105 when the plunger 110 is moving from TDC to BDC.

[0016] The fuel flows into the pumping chamber 105 until it is filled to its maximum capacity. Once the pumping chamber 105 is filled to its maximum capacity, the fuel begins to flow back into the gallery 145 and then to the fuel tank through the overflow line 125. The overflow line 125 includes a second non-return valve 106. When pressure of the fuel flowing from the pumping chamber 105 is above opening pressure of the second non-return valve 106, the valve opens and the fuel flows back into the fuel tank. The fuel continues to flow from the pumping chamber 105 back into the fuel tank until the valve piston 130 is at the operative close position.

[0017] When the supply of current to the solenoid valve is stopped, the valve piston 130 is drawn back to the valve seat 135. This causes the valve piston 130 to be in the operative close position and hence the fuel stops flowing from the pumping chamber 105 to the fuel tank. As a result, quantity of the fuel present inside the pumping chamber 105 is pressurized and pumped into a high pressure rail. The supply of current to the solenoid valve is stopped based on the CAM angle of the fuel pump 100 and the lift of the plunger 110 from the BDC.

[0018] An example is explained in the below paragraphs for the purpose of understanding that the supply of current to the solenoid valve is based on the CAM angle of the fuel pump 100 and the lift of the plunger 110 so that required quantity of fuel is supplied to the pumping chamber 105 based on the engine operating condition.

[0019] Let us consider that for a particular engine operating condition, fuel equivalent to 30% of filling capacity of the pumping chamber 105 is required to be pumped into the high pressure rail. When the plunger 110 is moving from TDC to BDC, the controller supplies current to the solenoid valve. As a result, the valve piston 130 moves away from the valve seat 135. This causes fuel to flow from the gallery 145 into the pumping chamber 105 until it is filled to 100% of its capacity. Once the pumping chamber 105 is filled to 100% of its capacity, the fuel from the pumping chamber 105 flows back into the fuel tank through the overflow line 125 until fuel equivalent to 30% of the filling capacity of the pumping chamber 105 is remaining in the pumping chamber 105. Let the cam angle be 60 degree and the lift attained by the plunger 110 be 5mm from BDC when fuel equivalent to 30% of the filling capacity is remaining in the pumping chamber 105. Once the controller determines that the cam angle is 60 degree and the lift of the plunger 110 is 5mm from BDC, the controller stops the supply of current to the solenoid valve. When the supply of current to the solenoid valve is stopped, the valve piston 130 is drawn back to the valve seat 135 and no fuel is allowed to flow from the pumping chamber 105 back into the fuel tank. The fuel remaining in the pumping chamber 105 is thus pressurized and pumped to the high pressure rail. Hence, by shutting of the valve piston 130 at a particular CAM angle and the lift of the plunger 110, required quantity of fuel for that particular engine operating condition is trapped in the pumping chamber 105 and the trapped fuel is thus pumped into the high pressure rail.

[0020] In another case, the valve piston 130 is in the operative open position when current is supplied, the solenoid valve. When the valve piston 130 moves is in the operative open position, fuel from the gallery 145 begins to flow into the pumping chamber 105. When a particular quantity of fuel for a particular engine operating condition is supplied to the pumping chamber 105 the vale piston 130 is operated to be at the operative close position by stopping the current supply to the control valve thereby preventing the flow of fuel from the gallery 145 into the pumping chamber 105. The flow of current is stopped based on the CAM angle of the fuel pump 100 and the lift of the plunger 110. The quantity of fuel supplied to the pumping chamber 105 is thus pressurized when the plunger moves from BDC to TDC. The pressurized fuel is then pumped into the high pressure rail.

[0021] Figure 2 shows an altered arrangement of the spring 104 with respect to the arrangement of the spring 104 in Figure 1. In some cases, it should be noted that the spring 104 in the solenoid valve is arranged such that when the current is supplied to the solenoid valve, the spring 104 is compressed and the valve piston 130 is drawn to the valve seat 135 and when the current supply to the solenoid is stopped, the valve piston 130 moves away from the valve seat 135. For such an operation, one end of the spring 104 is fixed to the housing as shown in figure 2 and the other end of the spring 104 is connected to magnets of the solenoid valve. When the current is not supplied to the solenoid valve, the valve piston 130 is away from the valve seat 135. When the current is supplied to the solenoid valve, the spring 104 is compressed and this draws the valve piston 130 to its valve seat 135.

[0022] Also, the fuel pump 100 disclosed in this disclosure is adapted to operate in two modes. In first mode, the pumping chamber 105 is first filled to its maximum quantity. Once the pumping chamber 105 is filled to its maximum quantity, the fuel begins to flow back into the fuel tank until the valve piston 130 is operated to close the inlet flow path 109. The valve piston 130 is closed such that a particular quantity of fuel for a particular engine operating condition is held within the pumping chamber 105.

[0023] When the fuel pump 100 is operated in the second mode, the inlet flow path 109 is opened so that fuel flows from the gallery 145 is supplied to the pumping chamber 105. When required quantity of fuel for based on engine operating condition is supplied to the pumping chamber 105, then the valve piston is operated to close the inlet flow path 109 thereby not allowing anymore fuel to flow into the pumping chamber 105. The fuel supplied to the pumping chamber 105 is pressurized and pumped into the high pressure rail.

[0024] It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the disclosure. Many modifications in the embodiments with regard working of the solenoid valve, dimensions of the step portion of the fuel pump, profile of the valve piston and profile of the valve seat are envisaged and form a part of this invention. The scope of the invention is only limited by the claims.

CLAIMS
We Claim
1 A fuel pump (100) comprising:
a pumping chamber (105);
a plunger (110);
an inlet port (107) and
an inlet flow path (109) in flow communication between said inlet port (107) and said pumping chamber (105);
characterized in that
a control valve located in said inlet port (107), said control valve comprising:
an inlet line (120) for supplying fuel from a fuel tank to said pumping chamber (105) and an overflow line (125) for returning fuel from said pumping chamber (105) to said fuel tank;
a valve piston (130), said valve piston (130) extending from said inlet port (107) into said inlet flow path (109), at least a part of said valve piston (130) in contact with a valve seat (135) defined by said inlet flow path (109) in an operative closed position for said valve piston (130); and
an actuator located proximate to said valve piston (130) and adapted to control movement of said valve piston (130) between an operative open position and an operative close position.

2 The fuel pump (100) as claimed in claim 1, comprising a gallery (145) formed between said control valve and said inlet port (107) of the fuel pump for storing fuel flowing into said pumping chamber (105).

3 The fuel pump (100) as claimed in claim 1, wherein one end of said inlet flow path (109) proximate to said valve piston (130) is provided with a step portion (140) forming said valve seat (135) for the part of said valve piston (130) which extends into said inlet flow path (109) such that said plunger (110) does not strike said valve piston (130) when said plunger (110) is reciprocating within said pumping chamber (105).

4 The fuel pump (100) as claimed in claim 1, wherein said valve piston (130) is operated to be in an operative open position for supplying fuel from a gallery (145) to said pumping chamber (105).

5 The fuel pump (100) as claimed in claim 1, wherein said valve piston (130) is operated to be in an operative open position for returning fuel from said pumping chamber (105) to a gallery (145).

6 The fuel pump (100) as claimed in claim 1, wherein said valve piston (130) is operated to be in an operative close position during pumping of the fuel from said pumping chamber (105) into a high pressure rail.

7 The fuel pump (100) as claimed in claim 1, wherein said actuator is an electromagnetic actuator.

8 The fuel pump (100) as claimed in claim 5, wherein said electromagnetic actuator is a solenoid.

9 The fuel pump (100) as claimed in claim 1, wherein at least a part of said inlet line (120) of said control valve and at least a part of said overflow line (125) of said control valve are common.

Dated this 31st day of March, 2015
(Digitally signed)
Kartik PuttAiah
Patent agent of the Applicants (IN/PA-1809)

ABSTRACT
A fuel pump 100 is disclosed. The fuel pump 100 comprises a pumping chamber 105, a plunger 110, an inlet port 107 and an inlet flow path 109. The fuel pump 100 is characterized by a control valve located in said inlet port 107 comprising an inlet line 120 for supplying fuel from a fuel tank to the pumping chamber 105 and an overflow line 125 for returning fuel from the pumping chamber 105 to the fuel tank. The control valve further comprises a valve piston 130 extending from the inlet port 107 into the inlet flow path 109 and an actuator located proximate to the valve piston 130 and adapted to control movement of the valve piston 130 between an operative open position and an operative close position.
Reference figure: Figure 1