Claims:We claim:
1. A turbidity sensor 12 for a fuel injection system 10, said fuel injection system comprising a fuel flow path 14, said fuel flow path 14 adapted to channel fuel containing soot from at least one of a fuel injector 16 and a high pressure fuel pump 18 to a fuel tank 20, said turbidity sensor 12 comprising:
a light emitter 33 positioned within said fuel flow path 14, said light emitter 33 adapted to emit a beam of light;
a light detector 35 positioned within said fuel flow path 14, said light detector 35 adapted to receive the beam of light that is emitted from said light emitter 33; and
a control unit 22 in electronic communication with said light detector 35, said control unit 22 adapted to determine a concentration of water in the fuel flowing through said fuel flow path 14 based on a variation in intensity of light received by said light detector 35 from said light emitter 33.

2. The turbidity sensor 12 in accordance with Claim 1, wherein said turbidity sensor 12 is positioned in a fuel return flow path of said high pressure fuel pump 18 to said fuel tank 20.

3. The turbidity sensor 12 in accordance with Claim 1, wherein said turbidity sensor 12 is positioned in a fuel return flow path of said fuel injector 16 to said fuel tank 20.

4. A control unit 22 in electronic communication with a turbidity sensor 12 for a fuel injection system 10, said control unit 22 adapted to:
receive an electronic signal from a light detector 35 of said turbidity sensor 12; and
determine a concentration of water in the fuel flowing through a fuel flow path 14 of said turbidity sensor 12 based on a variation in intensity of light received by said light detector 35 from a light emitter 33.

5. The control unit 22 in accordance with Claim 5 wherein the control unit 22 determines a concentration of water in the fuel flowing through said fuel flow path 14 based on a concentration of soot flowing from at least one of said fuel injector 16 and said high pressure fuel pump 18. , Description:Field of the invention:
[0001] This disclosure relates to a turbidity sensor, and more particularly to a turbidity sensor for a fuel injection system.
Background of the invention:
[0002] U.S. Patent Application Number 4713964A describes a device for measuring the optical turbidity, i.e., the soot components in discharge gases of diesel engines, which is relatively simply constructed, operates safely and enables a simple handling even with differently structured measuring devices. This result is achieved in that a controller for controlling the light density of the measuring light beam is optically coupled with a light source. A sample and hold circuit is provided with the values of a measuring detector and the control detector fed to a sample and hold circuit in a time multiplex manner with the measuring values processed in a computer unit. Control values are fed to the light source by means of a control loop. In addition, the computer unit is capable of storing a plurality of measuring values or turbidity values and average value of the stored peak values, whereby the peak values are determined by a dynamic measuring of a defined number of measuring cycles. Moreover, a device is provided which feeds motor related parameter to the computer unit for triggering of measuring value determination and measuring value calculation.

Brief description of the accompanying drawings:
[0003] An embodiment of the disclosure is described with reference to the following accompanying drawings:
[0004] Figure 1 illustrates a block diagram of a turbidity sensor in a fuel injection system; and
[0005] Figure 2 illustrates a block diagram of a turbidity sensor in electronic communication with a control unit shown in Figure 1.

Detailed description of the embodiments:
[0006] A turbidity sensor 12 for a fuel injection system 10 is described.. A light emitter 33 is positioned within the fuel flow path 14, the light emitter 33 adapted to emit a beam of light. A light detector 35 is positioned within the fuel flow path 14, the light detector 35 adapted to receive the beam of light that is emitted from the light emitter 33. A control unit 22 is in electronic communication with the light detector 35, the control unit 22 adapted to determine a concentration of water in the fuel flowing through the fuel flow path 14 based on a variation in intensity of light received by the light detector 35 from the light emitter 33.

[0007] The control unit 22 is in electronic communication with a turbidity sensor 12 for a fuel injection system 10. The control unit 22 is adapted to receive an electronic signal from a light detector 35 of the turbidity sensor 12. The control unit 22 is adapted to determine a concentration of water in the fuel flowing through a fuel flow path 14 of the turbidity sensor 12 based on a variation in intensity of light received by the light detector 35 from a light emitter 33.

[0008] Figure 1 illustrates a block diagram of a fuel injection system 10. The fuel injection system 10 includes a fuel tank 20. A fuel filter 28 is positioned downstream from the fuel tank 20 and receives fuel that is supplied from the fuel tank 20 by means of a low pressure fuel pump (not shown). Filtered fuel from the fuel filter 28 is channeled to a high pressure fuel pump 18, where the pressure of fuel is substantially increased. From the high pressure fuel pump 18, pressurized fuel is channeled to a high pressure common rail 26, from where it is delivered to a fuel injector 16. Pressurized fuel is delivered from the fuel injector 16 to an engine cylinder (not shown).

[0009] In accordance with one embodiment of the fuel injection system. Excess fuel from the high pressure pump and the excess fuel from the fuel injector is sent back to the fuel tank. For this embodiment of the fuel injection system the turbidity sensor is located in the fuel flow path downstream from the point in the fuel flow path which receives the fuel from the injector and the high pressure fuel pump.

[00010] In accordance with another embodiment of the fuel injection system. Excess fuel from the high pressure fuel pump 18 is delivered via a fuel return path 30 to a fuel accumulator 24, wherein the fuel accumulator 24 is used to store fuel. Similarly, excess fuel from the fuel injector 16 is delivered via a fuel return path 32 to the fuel accumulator 24. From the fuel accumulator 24, the stored fuel is channeled to a turbidity sensor 12 via a fuel flow path 14. In an alternate embodiment, the turbidity sensor 12 may be positioned upstream from the fuel accumulator 24 and downstream from the fuel injector 16. In yet another alternate embodiment, the turbidity sensor 12 may be positioned upstream from the fuel accumulator 24 and downstream from the high pressure fuel pump 18. The turbidity sensor 12 is used to measure a concentration of soot present in the fuel that is channeled from at least one of the fuel injector 16 and the high pressure fuel pump 18. A control unit 22 is in electronic communication with the turbidity sensor 12 and determines a concentration of water present in the fuel as will be explained in more detail below.

[00011] Figure 2 illustrates a block diagram 50 of a turbidity sensor 12 in electronic communication with a control unit 22. The turbidity sensor 12 includes a light emitter 33 that is positioned within the turbidity sensor 12. The light emitter 33 emits a beam of light that is received by a light detector 35 that is also positioned within the turbidity sensor 12. The light emitter 33 is positioned within a line of sight of the light detector 35 and transmits a beam of light to the light detector 35 at a specific intensity. Due to soot which flows with the fuel through the turbidity sensor 12, the intensity of light that is received by the light detector 35 is lower than the intensity of light that is emitted by the light emitter 33. Therefore, by determining the intensity of light that is received by the light detector 35, the control unit 22 calculates the concentration of soot flowing through the turbidity sensor 12. Based on the concentration of soot that is flowing through the turbidity sensor 12, the control unit 22 determines the quantity of water that is present in the fuel that flows out of the high pressure fuel pump 18 as will be explained in detail below. If the quantity of water that is present in the fuel is above a threshold limit, the control unit 22 activates an alerting device (not shown) to notify a user that the quantity of water that is present in the fuel is above the threshold limit.

[00012] The working of the turbidity sensor 12 in the fuel injection system 10 is described as an example. Fuel from the fuel tank 20 is channeled to the high pressure fuel pump 18 via the fuel filter 28. In the high pressure fuel pump 18, the fuel combines with small quantities of oxygen that is present in the high pressure fuel pump 18 to create soot particles and water. Due to the high temperature of fuel in the high pressure fuel pump 18, the water that is generated is decomposed to form hydrogen and oxygen molecules. The oxygen molecules combine with the fuel in the presence of the high temperature and pressure to create additional soot and water. The chain reaction continues, and hence a large quantity of soot and water are created in the high pressure fuel pump 18. The fuel containing the large quantity of soot and water are channeled from the high pressure fuel pump 18 to the high pressure common rail 26. From the high pressure common rail 26, the fuel containing the large quantity of soot and water are channeled to the fuel injector 16. From the high pressure fuel pump 18 and the fuel injector 16, the fuel containing the large quantity of soot and water are channeled to the fuel accumulator 24 via the fuel return path 30 and the fuel return path 32 respectively. From the fuel accumulator 24, the fuel containing the large quantity of soot and water are channeled to the turbidity sensor 12.

[00013] As the fuel containing the large quantity of soot and water flows through the turbidity sensor 12, the intensity of light that is received by the light detector 35 from the light emitter 33 is diminished. The amount of reduction in the intensity of light that is received by the light detector 35 is proportional to the concentration of soot that is present in the fuel. The control unit 22 receives an electronic signal from the light detector 35 and hence determines the concentration of soot that is present in the fuel. Based on the concentration of soot that is present in the fuel, the control unit 22 determines the quantity of water that is present in the fuel by means of a correlational map. If the quantity of water that is present in the fuel is above an acceptable threshold limit, the control unit 22 activates the alerting device to notify the user that the quantity of water that is present in the fuel is above the acceptable threshold limit.

[00014] 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.