Claims:We claim:
1. A pressure control valve (10) of a common rail system, said pressure control valve (10) comprising:
a housing(14) comprising an inlet and an outlet;
characterized in that
a moving plate (32) placed in proximity of said inlet of said housing (14);
a supporting element (26) placed in proximity of said outlet of said housing (14);
at least one first spring (28) connected between said moving plate(32) and one surface of said supporting element (26);
a cover plate (21) removably fitted to one end of said supporting element (26) away from said outlet of said housing (14);
a needle (18) placed in a central axial guide way formed through said moving plate (32) and said supporting element (26) in a manner such that at least a part of said needle (18) extends towards said moving plate (32) and at least a part of said needle (18) extends towards said cover plate (21), said needle (18) being spring (20) loaded against said cover plate (21);
and
at least one electro magnet (24) placed in proximity to said needle (18) and said cover plate (21).
2. The pressure control valve (10) as claimed in claim 1, wherein said housing (14) comprising a holder (22) adapted to hold said needle (18).
3. The pressure control valve (10) as claimed in claim 1, wherein at least a part of said needle (18) will be in contact with at least a part of said moving plate (32) in one operative position of said needle (18).
4. The pressure control valve (10) as claimed in claim 1, wherein a needle (18) placed in a central axial guide way formed through said moving plate (32) and said supporting element (26) in a manner such that at least a part of said needle extends beyond said moving plate (32).
5. The pressure control valve as claimed in claim 1, wherein at least one part of said moving plate (32) will be in contact with at least one part of said housing (32).
, Description:Field of the invention:
[0001] This disclosure relates to a pressure control valve of a common rail system.
Background of the invention:
[0002] In an internal combustion engine with a common rail system, the quality of combustion is critically determined by the pressure level in the rail. The life of the components in the common rail system will be affected if the pressure fluctuations goes very high. The pressure control valve mounted on the rail controls the pressure in the rail based on a feedback signal from an electronic control unit. A rail pressure sensor will provide the actual value of the pressure at any instant to the electronic control unit. The electronic control unit compares the received value with a predefined value and sends a correcting signal to the pressure control valve to open or close more, there by changing the amount of fuel leaking from the rail to achieve the desired pressure value. The pressure limiting valve will be opened mechanically due to the pressure of the fuel in the rail, if the pressure in the rail is more than a predefined pressure limit value of the system or component.
[0003] A European patent EP2278152 discloses a fuel injection valve having a control valve (solenoid valve) and a control element including a central bore for receiving and guiding a pressure pin. The control valve exhibits a pressure limiting function when the pin produces a hydraulic connection of the bore with a return line by changing axial length of the pin during defined pressure force at a front surface of the pin.

Brief description of the accompanying drawing s:
[0004] An embodiment of the disclosure is described with reference to the following accompanying drawings:
[0005] Figure 1 illustrates a pressure control valve of a common rail system according to one embodiment of the invention; and
[0006] Figure 2 illustrates a common rail system in a vehicle according to one embodiment of the invention.
[0007] Figure 3 illustrates a pressure control valve of a common rail system according to one embodiment of the invention.
Detailed description of the embodiments:
[0008] Figure 1 illustrates a pressure control valve 10 of a common rail system in accordance with this disclosure. The pressure control valve 10 comprises a housing 14 having an inlet 12 and an outlet 30. The pressure control valve 10 comprises a moving plate 32 placed in proximity of the inlet 12 of the housing 14 and a supporting element 26 placed in proximity of the outlet 30 of the housing 14. At least one first spring 28 is connected between the moving plate 32 and one surface of the supporting element 26.The pressure control valve 10 comprises a cover plate 21 removably fitted to one end of the supporting element 26 away from the outlet 30 of the housing 14. The pressure control valve 10 comprises a needle 18 placed in a central axial guide way formed through the moving plate 32 and the supporting element 26 in a manner such that at least a part of the needle 18 extends towards the moving plate 32 and at least a part of the needle 18 extends towards the cover plate 21, the needle 18 is spring 20 loaded against the cover plate 21.The pressure control valve10 comprises at least one electro magnet 24 placed in proximity to the needle 18 and the cover plate 21.

[0009] The needle 18 in the pressure control valve 10 is guided axially in the central axial guide way and at least a part of said needle 18 will be in contact with at least a part of the moving plate 32 in one operative position of the needle 18.The needle 18 used in this disclosure is such that the part of the needle 18 which is contact with the moving plate 32 has a shape which is different from the part of the needle 18 which extends towards the cover plate 21. In one embodiment, the needle 18 is placed in the central axial guide way in such a way that, at least a part of the needle 18 is in contact with the surface of the moving plate 32 away from the inlet of the housing of the pressure control valve as shown in figure 1. In another embodiment, the needle 18 is placed in the central axial guide way in such a way that at least one part of the needle 18 is placed is in contact with the surface of the moving plate in proximity of the inlet of the housing of the pressure control valve as shown in fig 3. At least one part of the moving plate 32 will be in contact with at least one part of the housing 14. The housing 14 comprises a holder 22 to hold the needle 18. The spring 20 is connected between the holder 22 and one surface of the cover plate 21. The needle 18 is fixed in the holder 22 in such a way that due to the movement of the needle 18, the spring 20 is either compressed or expanded.

[00010] Fig.2 illustrates a common rail system in a vehicle according to one embodiment of the invention. The common rail fuel injection system 50 comprises a common rail 38 positioned between a high pressure pump 36 and a plurality of fuel injectors 40. A fuel filter 34 is connected between the high pressure pump 36 and a fuel tank 31. The common rail fuel injection system 50 comprises a rail pressure sensor 35 and a pressure control valve 10 mounted on the common rail 38 adapted to maintain the pressure in the common rail 38. In one embodiment, the pressure control valve 10 is mounted on the common rail 38 in such a way that, the outlet 30 of the common rail 38 and the outlet of the pressure control valve 10 are in fluid communication with each other. In another embodiment, the pressure control valve 10 is mounted on the common rail 38 in such a way that, the outlet 30 of the pressure control valve 10 is directly connected to the fuel tank 31. An electronic control unit 33 connected to the pressure control valve 10 controls the position of the pressure control valve 10 in dependence with the detected pressure in the common rail 38.

[00011] The rail pressure sensor 35 senses the pressure in the common rail 38 and the sensed pressure is transmitted to the electronic control unit 33. Depending on the sensed pressure and the difference between the sensed pressure value and a predefined pressure value, the electronic control unit 33 supplies current to the electromagnet 24 to actuate the needle 18. Plurality of current values which will be supplied to the electromagnet 24 are mapped to plurality of fuel pressure values in the common rail 38. The current Vs fuel pressure map is stored in the electronic control unit 33.

[00012] In one embodiment of the invention, when the sensed pressure in the common rail 38 is more than the predefined pressure value, the electronic control unit 33 supplies a current to the electro magnet 24. The electro magnets 24 upon receiving the current, actuates the needle 18 in a direction such that, the needle 18 moves towards the covering plate 21 of the housing 14 .The spring 20 which is connected between the holder 22 of the needle and one surface of the covering plate 21 is compressed due to the movement of the needle 18.The holder 22 which is holding the needle 18 also moves in the same direction in which the needle 18 is moved. Due to the movement of the needle 18, the fuel present in the common rail 38 will pass through the outlet 30, thus by reducing the pressure in the common rail 30.

[00013] If the sensed pressure in the common rail 38 continues to be more than a predefined safety pressure limit, the moving plate 32 will be pushed towards the supporting element 26 as the pressure of the fuel in the common rail 38 is high enough to over the spring force of the spring that is located between the moving plate and the supporting element 26. Due to the movement of the moving plate 32, the first spring 28 will get compressed towards supporting element 26, thus allowing more fuel to pass through the outlet 30. Thus the moving plate provides an additional safety mechanism in case the pressure build up in the common rail is beyond acceptable limit of the common rail. Once the pressure reduces and is within acceptable limit the moving plate moves back to its original position. Further, when the electronic control unit 33 detects the pressure in the common rail 38 has reduced to the desired value, the supply of the current is discontinued to the electromagnets 24. The spring 20 which is compressed due to the movement of the needle 18 expands and brings the needle 18 to its initial position.

[00014] In another embodiment of the invention, when the pressure in the common rail is more than the predefined value, the electronic control unit 33 supplies a current to electromagnet 24 to actuate the needle 18. The needle 18 is actuated in such a way that, the needle 18 moves in a direction (i.e., towards the inlet 12) allowing the fuel to pass through the outlet 30 back to the fuel tank. The spring 20 connected to the needle expands towards the supporting element 26 due to the movement of the needle 18. When the sensed pressure in the rail 38 continues to increase beyond a pressure value which is acceptable for the common rail, the pressure of fuel impinging on the moving plate 32 will be high enough to overcome the spring force of the first spring 28 such as to move the moving plate towards the supporting element 26. The first spring 28 will be compressed towards the supporting element 26 due to the movement of the moving plate 32. Due to the movement of the moving plate 32 and the first spring 28, more fuel is made to pass through the outlet 30 back into the fuel tank, thus reducing the pressure of the fuel in the common rail to reduce the pressure of fuel in the rail under acceptable limit. Thus the moving plate provides an additional safety mechanism in case the pressure build up in the common rail is beyond acceptable limit of the common rail. Once the pressure reduces and is within acceptable limit the moving plate moves back to its original position. Further, when the pressure in the common rail 38 reaches the desired value, the electronic control unit 33 discontinues the supply of current to the electromagnets 24. As the supply of current to the electromagnets is stopped the spring 20 which was earlier in an expanded state will come back to its original compressed state. As the spring 20 attains its original compressed position the needle 18 will be displaced and the needle 18 will move back to its initial position.

[00015] With the above pressure control valve 10, the pressure controlling and pressure limiting function can be achieved. The needle 18 which is spring 20 loaded is used to control the rail pressure, by making the valve to act like a pressure control valve 10. The spring 20 which is connected between the moving plate 32 and the supporting element 26 is used to open the valve when the pressure in the common rail is beyond the safety/ acceptable pressure limit of the common rail, thus by acting like a pressure limiting valve10. With the above design of the pressure control valve 10 disclosed, the number of components required to maintain the fuel pressure in the common rail is reduced.

[00016] 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.