Claims:We Claim:
1. A device (10) to detect flow of fuel in a low pressure (LPC)(20) of a fuel injection system (100), said device comprising:
- a first port (12);
- a second port (14);
- a rotary member (16) adapted to rotate when fuel is incident on said rotary member (16) during operation of said LPC (20); and
- a sensing means (18) in proximity of said rotary member (16) adapted to sense movement of said rotary member (16) in one direction.
2. The device as claimed in claim 1, wherein said rotary member (16) is a turbine with a plurality of vanes.
3. The device as claimed in claim 2, wherein plurality of contact means (22) located on said plurality of vanes.
4. The device as claimed in claim 1, wherein said sensing means (18) communicates with an electronic control unit (24)
5. A low pressure circuit (LPC) (20) in a fuel injection system, said LPC (20) comprising at least:
- a first fuel flow path (26) from a fuel tank (102) to a high pressure pump (106);
- a second fuel flow path (28) from said high pressure pump (106) to said fuel tank (102);
characterized in that
- a device (10) to detect flow of fuel, said device (10) located in said LPC (20) adapted to detect flow of fuel in a direction upstream from said fuel tank (102) towards said high pressure pump (106) in said second fuel flow path (28).
6. The LPC (20) as claimed in claim 4, wherein said first fuel flow path (26) comprises a filter (30) located downstream from said fuel tank (102) and upstream from said high pressure pump (106).
7. The LPC (20) as claimed in claim 4, wherein said device (10) is located in said second fuel flow path (28) of said LPC (20).
8. The LPC (20) as claimed in claim 4, wherein said device (10) comprising:
- a first port (12);
- a second port (14);
- a rotary member (16) adapted to rotate when fuel is incident on said rotary member (16) during operation of said LPC (20); and
- a sensing means (18) in proximity of said rotary member (16) adapted to sense movement of said rotary member (16) in one direction
9. An electronic control unit adapted to control working of a fuel injection system, said electronic control unit adapted to perform the following steps:
- receiving from a sensing means (18) a signal indicative of the movement of a rotary member (16) in a device (10);
- indicating on a vehicle dashboard by means of a lamp an indication with reference to the flow of fuel in a direction upstream from said fuel tank (102) towards said high pressure pump (106) in a second fuel flow path (28); and
- limiting the operation of said fuel injection system (100) in the event said signal from said sensing means (18) is received for more than a pre-determined duration of time.
, Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001] This invention relates to a device to detect flow of fuel in a low pressure circuit (LPC) and an low pressure circuit (LPC) thereof.

Background of the invention
[0002] In a common rail fuel injection system 100 known in the state of the art as seen in figure 1 the fuel is drawn from a fuel tank 102 by feed pump 104. The feed pump 104 supplies the fuel from the fuel tank to a high pressure pump 106. A filter 105 is located in the fuel flow path between the feed pump 104 and the high pressure pump 106. The high pressure pump 106 pressurizes the fuel that it receives from the feed pump 104 and sends the fuel to a common rail/accumulator 108. The common rail/accumulator 108 stores and maintains the fuel at a particular pressure. Pressure of the fuel in the common rail/accumulator 108 depends not only on the system design but also on the size of the common rail/accumulator 108. The fuel from the common rail/accumulator 108 is then sent to the injectors 110 and further to the engine (not shown in figure 1). The high pressure pump 106 may also be provided with a fuel metering unit 112 which performs the function of inlet fuel metering. The common rail/accumulator 108 is also provided with a pressure limiting valve 114 to ensure release of fuel from the common rail 108 to the fuel tank 102. The fuel injection system 100 is controlled by an electronic control unit 116.

[0003] WO2007122023A discloses a high-pressure fuel delivery device for an internal combustion engine comprises a high-pressure pump and a low-pressure flow path. The low-pressure flow path leads from a fuel inlet of the high-pressure fuel delivery device to a holding space for a driveshaft of the high-pressure pump and onward to at least one inlet valve of the high-pressure pump. Leakage and/or lubricating fuel is recirculated via a recirculation flow path. It is proposed that the recirculation flow path opens out 66 into the low-pressure flow path 72.

[0004] With specific reference to this disclosure the focus can be laid on the low pressure circuit of the fuel injection system. The low pressure circuit with reference to this disclosure is defined as the flow paths of the fuel injection system that carry low pressure fuel. Typically, the low pressure fuel flows in a downstream path from the fuel tank 102 to the fuel filter 105 and then to the high pressure pump 106. The low pressure fuel flow in a return line wherein the fuel flows from the high pressure pump 106 back to the tank 102.

[0005] With specific focus to the problem statement in accordance with this disclosure. In a common rail pump, when the plunger moves down suction is created and fuel fills in the plunger volume. The pump also houses a throttle for draining the excess fuel and lubrication fuel in case of fuel lubricated pumps. When suction is created fuel can flow from the fuel tank to the return line. Since the return line is connected directly to the tank the unfiltered fuel can enter the high pressure pump 106 and damage the entire system due to particles from the tank 102.

[0006] Similar concept is also observed in common rail systems with start electric feed pump. Start electric feed pump based systems are used for quick start of vehicle by catalyzing the rail pressure build up. These systems are equipped with an overflow valve (~1.5 bar opening pressure) at filter outlet to avoid pressure flow from electric feed pump damaging the gear pump on the high pressure pump. However, the drawback of such a system is the tendency of the gear pump to create high suction at high speeds which can lead to sucking of fuel from this overflow line. Since there is no fuel filter in this line, there are chances of particle entry into the common rail system which can lead to damage of components.

[0007] It is an object of the device and the low pressure circuit of this disclosure to overcome the problem as explained above.
Brief description of the accompanying drawings:
[0008] Different mode of the invention is disclosed in detail in the description and illustrated in the accompanying drawings:
[0009] Figure 1 illustrates a fuel injection system known in the state of the art;
[0010] Figure 2 illustrates a device to detect fuel flow in a low pressure circuit in accordance with this disclosure;
[0011] Figure 3 illustrates a first embodiment of the fuel injection system incorporating a device in accordance with this disclosure; and
[0012] Figure 4 illustrates a second embodiment of the fuel injection system incorporating a device in accordance with this disclosure;

Detailed description of the embodiments
[0013] Figure 2 illustrates a device to detect fuel flow in a low pressure circuit (LPC) of the fuel injection system. The device 10 comprises a first port 12, a second port 14, a rotary member 16 adapted to rotate when fuel is incident on the rotary member 16 during operation of the LPC 20 and a sensing means 18 in proximity of the rotary member 16 adapted to sense movement of the rotary member 16 in one direction.

[0014] In accordance with one embodiment of the device 10 the rotary member 16 is a turbine with a plurality of vanes. A plurality of contact means 22 are located on the plurality of vanes. The sensing means 18 communicates with an electronic control unit 24. The plurality of contact means 22, which are located on the vanes move along with the rotary member, which is a turbine. The location of the contact means 22 with reference to the location of the sensing means 18 is such that the contact means 22 and the sensing mean 18 continue to be in proximity of each other during the operation of the device 10. Further the location of the contact means 22 with reference to the sensing means is such that the sensing means 18 is able to pick up the proximity of the contact means 22 only when the rotary means rotates in one direction.

[0015] In accordance with this disclosure there is also provided a low pressure circuit (LPC) 20 in a fuel injection system. The LPC 20 comprises at least a first fuel flow path 26 from a fuel tank 102 to a high pressure pump 106, a second fuel flow path 28 from the high pressure pump 106 to said fuel tank 102, the LPC 20 is characterized such as to comprise a device 10 to detect flow of fuel. The device 10 located in the LPC 20 is adapted to detect flow of fuel in a direction upstream from the fuel tank 102 towards the high pressure pump 106 in the second fuel flow path 28.

[0016] The first fuel flow path 26 comprises a filter 30 located downstream from the fuel tank 102 and upstream from the high pressure pump 106. The device 10 is located in the second fuel flow path 28 of the LPC 20. The device 10 comprises a first port 12, a second port 14, a rotary member 16 is adapted to rotate when fuel is incident on the rotary member 16 during operation of the LPC 20 and a sensing means 18 in proximity of the rotary member 16 adapted to sense movement of the rotary member 16 in one direction. During the operation the fuel flowing through the device 10 may be incident on the rotary member 16 when the fuel flow from the first port 12 downstream towards the second port 14. During the operation the fuel flow through the device 10 may be incident on the rotary member 16 when the fuel flows from the second port 14 upstream toward the first port 12. The sensing means 18 is adapted to work in a manner such that it is able to pick up the proximity of the contact means only when the fuel in the second flow path flows from the second port 14 towards the first port 12.

[0017] In accordance with this disclosure there is also provided an electronic control unit (24) adapted to control working of a fuel injection system. The electronic control unit adapted to perform the following steps: receiving from a sensing means 18 a signal indicative of the movement of a rotary member 16 in a device 10; indicating on a vehicle dashboard by means of a lamp an indication with reference to the flow of fuel in a direction upstream from the fuel tank 102 towards the high pressure pump 106 in a second fuel flow path 28 and limiting the operation of the fuel injection system 100) in the event the signal from the sensing means 18 is received for more than a pre-determined duration of time.

[0018] For easier understanding of the working of the device and the LPC circuit in accordance with this disclosure it is important to understand the two configurations of the fuel injection system as shown in figure 3 and figure 4. Figure 3 illustrates a fuel injection system incorporating the device 10 in accordance with this disclosure and having an LPC circuit in accordance with this disclosure. As per this fuel injection system there is provided a fuel tank 102 and a first flow path 26 from the fuel tank 102 to the high pressure pump 106. A fuel filter 105 is located in first flow path 26 downstream from the fuel tank 102 and upstream from the high pressure pump 106. The fuel injection system comprises a second flow path 28 from the high pressure pump 106 to the fuel tank 102. This is a fuel injection system where the fuel is sucked from the fuel tank 102 to the high pressure pump 106 due to the suction pressure from the high pressure pump 106. The fuel filter 105 comprises a hand primer, which is used to manually fill the fuel filter 105 with fuel. The first flow path 26 and second flow path 28 define the LPC of the fuel injection system. The device 10 is located in the second flow path 28.

[0019] During operation of the fuel injection system in as seen in figure 4, the high pressure pump 106 is operated and the fuel is sucked from the fuel tank 102 towards the high pressure pump 106 through the filter 105. Some of the fuel from the high pressure pump 106 overflows through the overflow valve flows through the second flow path 28 of the LPC 20. The overflow fuel in the second flow path 28 enters the device 10 through the first port 12 and flow out of the second port 14. During the flow of fuel from the first port 12 to the second port 14 the fuel is incident on the rotary member 16 of the device 10.

[0020] As the piston of the high pressure pump 106 moves down a suction is created, as the suction is created the fuel would flow in the second flow path 28 and through the device 10 from the second port 14 towards the first port 12. As mentioned earlier the sensing means 18 is designed such that it is able to pick up the proximity of the contact means 22 only when the fuel flows from the second port 14 toward the first port 12. The sensing means 18 then sends this information to the electronic control unit 24. On receiving the signal from the sensing means the electronic control unit 24 switched on a lamp in the dashboard of the vehicle. The switched on lamp indicates that the fuel is flow from the fuel tank towards the high pressure fuel pump. This means that there is possibility that the fuel from the tank containing impurities could enter the high pressure pump. If this continue for a period long that a pre-determined period the electronic control unit 24 limits the operation of the fuel injection system. Limiting the operation of the fuel injection system would mean reducing the speed of working of the high pressure fuel pump so that the suction pressure is not created or reducing the speed of the engine to which the high pressure fuel pump is connected.

[0021] Figure 4 illustrates a fuel injection system incorporating the device 10 in accordance with this disclosure and having an LPC circuit in accordance with this disclosure. As per this fuel injection system there is provided a fuel tank 102 and a first flow path 26 from the fuel tank to the high pressure pump 106. A fuel filter 105 is located in first flow path 26 downstream from the fuel tank 102 and upstream from the high pressure pump 106. Further an electric feed pump is provided downstream from the fuel tank and upstream from the fuel filter. In this kind of system the fuel is pumped by the electric feed pump from the fuel tank to the filter. The fuel injection system comprises a second flow path 28. In this specific implement the second flow path 28 is divided into two part a first portion 28a which take the fuel from the fuel filter back to the fuel tank and a second portion 28b which takes the fuel from the high pressure pump to the fuel tank. The device 10 is located in the second portion 28b of the second flow path 28.

[0022] This type of fuel injection system as shown in figure 4 are equipped with an overflow valve at fuel filter 105 outlet to avoid pressure flow from electric feed pump damaging the gear pump on the high pressure pump. However, the drawback of such a system is the tendency of the gear pump to create high suction at high speeds, which can lead to sucking of fuel from this overflow line. Since there is no fuel filter in this line, there are chances of particle entry into the common rail system which can lead to damage of components.

[0023] Thus when fuel gets sucked from the fuel tank toward the second portion of the 28b of the second flow path 28, fuel would flow in the second flow path 28 and the second port 28b and through the device 10 from the second port 14 towards the first port 12. As mentioned earlier the sensing means 18 is designed such that it is able to pick up the proximity of the contact means 22 only when the fuel flows from the second port 14 toward the first port 12. The sensing means 18 then sends this information to the electronic control unit 24. On receiving the signal from the sensing means the electronic control unit 24 switched on a lamp in the dashboard of the vehicle. The switched on lamp indicates that the fuel is flow from the fuel tank towards the high pressure fuel pump. This means that there is possibility that the fuel from the tank containing impurities could enter the high pressure pump. If this continue for a period long that a pre-determined period the electronic control unit 24 limits the operation of the fuel injection system. Limiting the operation of the fuel injection system would mean reducing the speed of working of the high pressure fuel pump so that the suction pressure is not created or reducing the speed of the engine to which the high pressure fuel pump is connected.

[0024] 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