Claims:We Claim:
1. A system (100) to count an opening of a pressure limiting valve (103) in a common rail system , the system comprising a common rail (100), a rail pressure sensor (102), a pressure limiting valve (103), a low pressure return line connector (104) and at least an Electronic Control Unit (ECU (105)), characterized in the system :

a first piezo sensor (106) connected to the ECU (105);

a second piezo sensor (107) connected to the ECU (105).

2. A system to count an opening of the pressure limiting valve (103) in a common rail system as claimed in claim 1, where the first and second piezo sensors are placed across the walls of the low pressure return line connector (104) proximate to the pressure limiting valve (103).

3. A system to count an opening of the pressure limiting valve (103) in a common rail system as claimed in claim 1, where a voltage is applied on the first piezo sensor (106) by the ECU (105).

4. A system to count an opening of the pressure limiting valve (103) in a common rail system as claimed in claim 1, where the second piezo sensor (107) generates a voltage and sends it to the ECU (105).

5. A method (200) of counting an opening of the pressure limiting valve (103) in a common rail system the system comprising a common rail (101), a rail pressure sensor (102), a pressure limiting valve (103), a low pressure return line connector (104) and at least an Electronic Control Unit (ECU (105)), where the ECU (105) is capable of:

applying (201) an input voltage to a first piezo sensor;

receiving (202) an output voltage from a second piezo sensor;

receiving (203) data regarding a pressure drop in the common rail (101) from the rail pressure sensor (102);

recording (204) the output voltage and the data regarding the pressure drop;

counting (205) number of times said pressure limiting valve (103) is opened based on said recording.

6. A method of counting an opening of the pressure limiting valve (103) in a common rail system as claimed in claim 5, where the first and second piezo sensors are placed across the walls of the low pressure return line connector (104) proximate to the pressure limiting valve (103).
, 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] The present disclosure relates to a system to count an opening of a pressure limiting valve in a common rail system.

Background of the invention
[0002] Conventionally a Pressure Limiting Valve (PLV) opening count for a common rail application is calculated based on momentary pressure drop in Rail Pressure Sensor (RPS). Every time, the momentary drop in rail pressure is not due to the opening of the PLV creating an error in the actual PLV opening counts. These errors falsely indicate problems in the common rail system and can take the vehicle in the limp home mode. There is a need for real time data and fool proofing against errors.

[0003] Patent Application US7451038B2 Method for detecting the opening of a passive pressure limiting valve discloses a method for detecting the opening of a passive pressure limiting valve for releasing fuel from a common rail fuel injection system to a tank with a fuel supply including a throttle wherein, based on a stationary rail pressure present during manual operation, a load reduction is detected when the rail pressure exceeds a first limit value and, as a result, a PWM signal for controlling the suction throttle is temporarily increased, the opening of the pressure limiting valve is recognized if, as a result, the rail pressure exceeds a second limit value and increases still further.

Brief description of the accompanying drawings
[0004] An embodiment of the invention is described with reference to the following accompanying drawings:
[0005] Fig. 1 depicts a system to count an opening of a pressure limiting valve in a common rail system; and
[0006] Fig. 2 is a flow-chart for a method to count an opening of a pressure limiting valve in a common rail system.

Detailed description of the drawings

[0007] Figure 1 depicts a system (100) to count an opening of a pressure limiting valve (103) in a common rail system. The system comprises a common rail (101), a rail pressure sensor (102), a pressure limiting valve (103), a low pressure return line connector (104) and at least an Electronic Control Unit (ECU (105)). In an embodiment the system comprises a first piezo sensor (106) and a second piezo sensor (107). The first and second piezo sensors are connected to the ECU (105).

[0008] The first and second piezo sensors are placed across the walls of the low pressure return line connector (104) proximate to the pressure limiting valve (103). In another embodiment of the present invention, the system comprises of a single piezo-sensor placed across the walls of the low pressure return line connector (104) proximate to the pressure limiting valve (103). The single piezo- sensor is connected to the ECU (105).

[0009] The common rail (101) holds the high pressure fuel. The rail pressure sensor (102) measure the pressure in the common rail and the sends the information to the ECU (105). The pressure limiting valve (103) comprises a valve and a spring. When the spring is compressed the valve open and the fuel flows into the low pressure return line connector (104).

[0010] In an embodiment of the above invention discussed above a voltage is applied on the first piezo sensor (106) by the ECU (105). The piezo sensor work on the principle of inverse piezo-electric effect. It means that when a piezo-electric material is subjected to a harmonically varying electric field, it starts vibrating and creates an alternate compression and rarefaction in the surrounding fluid media, which results in the production of sound. This sound is transmitted across the low pressure return line connector (104) and reached the second piezo sensor (107).The second piezo sensor (107) works on the principle of piezo-electric effect and generates a voltage. This voltage is sensed by the ECU (105).

[0011] In another embodiment of the present invention as discussed above the single piezo-sensor senses the flow of fuel in the low pressure return line connector (104) and generates a voltage. This voltage is sensed by the ECU (105).

[0012] Figure 2 is a flow-chart for a method to count an opening of a pressure limiting valve (103) in a common rail system. In step (201) the ECU (105) applies an input voltage to a first piezo sensor (106). In step (202) the ECU (105) receives an output voltage from a second piezo sensor (107). In step (203) the ECU (105) receives data regarding a pressure drop in the common rail (101) from a rail pressure sensor (102). In step (204) the ECU (105) records the output voltage and the data regarding the pressure drop. In step (205) the ECU (105) counts number of times said pressure limiting valve (103) is opened based on said recording.

[0013] In step (201) a voltage is applied to the first piezo sensor (106). Since the piezo sensor works on the principle of inverse piezo-electric effect, the first piezo sensor (106) generates ultrasonic waves which are transmitted across the diameter of the low pressure return line connector (104). These ultrasonic waves reach the second piezo sensor (107). The ultrasonic waves cause vibrations in the second piezo-sensor. Since the second piezo-sensor (107) works on the principle of piezo-electric effect the vibration cause the second piezo sensor (107) generates a voltage. This voltage is sensed and measured by the ECU (105).

[0014] In step (202) the ECU (105) receives this voltage and generates a waveform. When the pressure limiting valve (103) is closed there would no flow of fuel in the low pressure return line connector (104), hence the ultrasonic waves would take a time T1 to travel across the diameter of the low pressure return line connector (104). When the pressure limiting valve (103) is opened fuel flows through the low pressure return line connector (104), hence the ultrasonic waves take a time T2 to travel across the low pressure return line connector (104). T1 is greater than T2 hence the voltage received by the ECU (105) based on the vibration of the second piezo sensor (107) will also vary. Hence the voltage waveform generated by the ECU (105) for the time T2 will show a disturbance.

[0015] In step (203) the ECU (105) receives a data regarding a pressure drop in the common rail from the rail pressure sensor (102). In step (204) the ECU (105) records the output voltage and the data regarding the pressure drop. The readings of the output voltage and the pressure drop are analyzed. In step (205) the ECU (105) counts the number of times said pressure limiting valve (103) is opened based on said recording. This is done based on the number of times there is disturbance in the voltage waveform generated from the voltage output of the second piezo sensor (107) and a corresponding pressure drop in the readings of the rail pressure sensor (102).

[0016] This idea to develop a real time counter to count the number of openings of the pressure limiting valve (103) helps convey the accurate information to the ECU (105) regarding the functioning of the system components inside an internal combustion engine. In conventional systems where the count of pressure limiting valve (103) openings is calculated only by the data received from the rail pressure sensor (102), there are high chances of errors. A sudden drop in rail pressure due to any reason other than the opening of the pressure limiting valve (103) is also construed as a pressure limiting valve (103) opening and gives false information to the ECU (105). This false information can lead to the vehicle going in a limp-home mode. The present invention disclosure avoids this error and false information.

[0017] It must be understood that the embodiments explained in the above detailed description are only illustrative and do not limit the scope of this invention. Any modification to the system to count an opening of a pressure limiting valve (103) in a common rail system are envisaged and form a part of this invention. The scope of this invention is limited only by the claims.