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 diesel exhaust fluid (DEF) system to measure a temperature of an exhaust fluid.
[0002] Background of the invention
[0003] Modern diesel vehicles that are equipped with selective catalytic reduction use a diesel exhaust fluid (DEF) for removal and reduction of nitrous oxides. The DEF typically comprises high purity urea dissolved and suspended within de-ionized water. This solution of urea in demineralized water is commonly known as Adblue.
[0004] The DEF (AdBlue) is stored in the manufacturer’s original container and kept in a cool, covered area with good ventilation and out of direct sunlight to prevent water loss due to evaporation. Typically, the DEF (AdBlue) freezes at -11.5 deg. When it is thawed, it returns to its initial quality. When the vehicle is switched ON, a supply module (SM) supplies DEF (AdBlue) to a dosing module for the exhaust gas treatment. However, due to frozen DEF (AdBlue), the supply is restricted till a heater melts & clears the frozen AdBlue in the flow path of the supply module.
[0005] In existing systems, there are no systems that can effectively detect the AdBlue temperature to understand the fluid condition. The prior art US2022127988 AA discloses a first temperature sensor positioned within the diesel exhaust fluid supply module and structured to provide first temperature information indicative of a first temperature, and a second temperature sensor positioned within the diesel exhaust fluid supply module and structured to provide second temperature information indicative of a second temperature. The systems and apparatuses further include one or more processing circuits including one or more memory devices coupled to one or more processors, the one or more memory devices configured to store instructions thereon that, when executed by the one or more processors, cause the one or more processors to provide energy to a heating system based on the first temperature information and the second temperature information.
[0006] In the present disclosure, a plastic spring clip with Negative temperature coefficient (NTC) temperature sensor is attached to measure the AdBlue temperature in supply module periodically. By knowing the DEF (AdBlue) condition and with the effective control of heater, the supply of DEF (AdBlue) to the dosing module will be improved. The disclosed DEF system with The NTC temperature sensor provides improved sensing accuracy. Further, the same is compatible with existing designs and limits any extra manufacturing requirements.

[0007] Brief description of the accompanying drawings
An embodiment of the invention is described with reference to the following accompanying drawings:
[0008] Figure 1 depicts a diesel exhaust fluid (DEF) system to measure a temperature of an exhaust fluid.
[0009] Figure 2 depicts a flowchart for a method to measure a temperature of an exhaust fluid in a diesel exhaust fluid (DEF) system.

[0010] Detailed description of the drawings:

[0011] The present disclosure provides a system and a method to measure a temperature of an exhaust fluid.

[0012] A temperature measuring device is fixed at a bottom end of a plastic spring clip and filled with a fluid, preferably from a group of epoxides to protect and provide good conductivity. A sensor harness is guided through the plastic spring clip. The sensor, the harness and the epoxide filling together constitute the spring clip assembly. A top end of the spring clip assembly is mounted on the pump module with a snaping feature. The snaping feature is a spring clip that latches on to a fixation screw. The fixation screw attaches the pump module with a printed circuit board (PCB).
[0013] This makes the spring clip assembly integrated with pump module and the PCB. The sensor wire harness is connected with PCB through a connector. While assembling the pump module with a exhaust fluid in a DEF supply module (to store the exhaust fluid) ,the plastic spring clip is compressed between the pump module & a housing surface of the chamber in the supply module. This ensures that the sensing surface is always in contact with the housing. To compensate the assembly tolerance deviations, a thermal paste may be used to reduce the air gap (if any) at sensing surface. The bottom end (sensor surface) of the proposed NTC spring clip temperature sensor may be placed on the AdBlue housing surface with a guiding feature (sensor locator) in housing. The NTC temperature sensor on the DEF(AdBlue) housing surface can detect DEF temperature indirectly (since no contact with DEF). At certain intervals the NTC sensor will be activated to sense the temperature of DEF housing surface. Since the NTC sensor with plastic spring clip detects the surface temperature of the DEF housing, the difference in temperature between housing surface & DEF may be calibrated in an electronic control unit (ECU), said ECU adapted control the supply of the DEF to the dosing module.
[0014] The present invention will now be described by way of example, with reference to accompanying drawings. Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations, and fragmentary views. In predetermined instances, details which are not necessary for an understanding of the present invention, or which render other details difficult to perceive may have.

[0015] Referring to Figure 1, the same depicts a diesel exhaust fluid (DEF) system (10) to measure a temperature of an exhaust fluid. The DEF system comprises a pump module (1), an exhaust fluid chamber (2) in a DEF supply module and a Printed Circuit board (PCB)(3). The PCB (3) is attached to the pump module (1) through a fixation screw (4). A temperature measuring device(5) comprises an upper portion (5a). The upper porting (5a) of the temperature measuring device (5) has at least one clip(5d). Said at least one clip (5d) is fastened on to the fixation screw (4). The temperature measuring has a curved middle portion (5b).The temperature measuring device further has an end portion (5c) fixed on to a housing (6) of the exhaust fluid chamber(2). Said end portion (5c) comprises a cavity (8) having a thermistor (9) in a wired connection with the PCB(3). The wire (13) may be connected to the PCB through a wire connector (14)

[0016] The PCB(3) is adapted to measure the temperature of the exhaust fluid based on a pre-defined thickness of the housing(6) of the exhaust fluid chamber (2) and a change in resistance of the thermistor(9). In an example, the type of thermistor is a negative temperature coefficient (NTC) thermistor. A thermistor is a type of resistor whose resistance is dependent on temperature. The word is a combination of thermal and resistor. NTC thermistors have a negative temperature coefficient which means when temperature rises the resistance will decrease.

[0017] The cavity (8) is filled with a fluid, said fluid selected from a group of epoxides. In an example the fluid may be epoxy. Epoxy is stable, tough, and resistant to corrosive chemicals, epoxies are excellent adhesives and useful surface coatings. Epoxy is the family of basic components or cured end products of epoxy resins.

[0018] A surface (11) between the housing and the fluid filled cavity may be sealed by a thermal paste. Thermal paste is a thermally conductive chemical compound used as an interface between two surfaces where heat is transferred. The main role of thermal paste is to eliminate air gaps or spaces (which act as thermal insulation) from the interface area to maximize heat transfer and dissipation. The end portion of the temperature measuring device may be placed on the housing surface with a sensor locator (7) in housing.

[0019] Referring to figure 2, the same depicts a flowchart for a method to measure a temperature of an exhaust fluid in a diesel exhaust fluid (DEF) system, said DEF system comprises a pump module, an exhaust fluid chamber and a Printed Circuit board (PCB) attached to the pump module through a fixation screw as described above. It is to be understood that a system to implement the present method has been described in Figure 1. The method comprises the first step (101) of fastening an upper portion of a temperature measuring device to the fixation screw through at least one clip, said upper portion comprising the at least one clip. The method (101) followed by method step (102) of fixing an end portion of the temperature measuring device to a housing of the exhaust fluid chamber, said end portion comprising a thermistor, said thermistor in a wired connection with the PCB.

[0020] The temperature of the exhaust fluid by said PCB is measured based on a pre-defined thickness of the housing of the exhaust fluid chamber, and a change in resistance of the thermistor. A cavity in the end portion having the thermistor is filled with a fluid, said fluid selected from a group of epoxides. A surface between the housing and the cavity having the thermistor and the fluid is filled by a thermal paste.

[0021] Advantageously in the present invention, the proposed DEF system provides improved sensing accuracy of the diesel exhaust fluid. The proposed NTC temperature sensor can be operated under a wide range of operating conditions, (-40º C to 85º C).

[0022] Further, the NTC temperature sensor measurement signals can be measured along with the pump module signals through the PCB, thereby eliminating the need for separate connectivity.
, Claims:WE CLAIM:

1. A diesel exhaust fluid (DEF) system(10) to measure a temperature of an exhaust fluid, said DEF system comprising a pump module (1), an exhaust fluid chamber(2) and a Printed Circuit board (PCB) (3), said PCB (3) attached to the pump module(1) through a fixation screw(4),
characterized in the DEF system (10),
a temperature measuring device(5) comprising:
- an upper portion(5a) having at least one clip, said at least one clip fastened on to the fixation screw;
-a curved middle portion(5b); and
-an end portion(5c) fixed on to a housing of the exhaust fluid chamber, said end portion comprising a cavity (8) having a thermistor (9) in a wired connection with the PCB(3).

2. The DEF system (10) as claimed claim 1, wherein, said PCB is adapted to measure the temperature of the exhaust fluid based on:
- a pre-defined thickness of a housing (6) of the exhaust fluid chamber (2), and
- a change in resistance of the thermistor(9).

3. The DEF system (10) as claimed in Claim 1, wherein, the cavity(8) is filled with a fluid, said fluid selected from a group of epoxides.

4. The DEF system (10) as claimed in Claim 3, wherein, a surface between the housing (6) and the fluid filled cavity(8) is sealed by a thermal paste.

5. The DEF system(10) claimed in Claim 1, wherein a type of thermistor (9) is a negative temperature coefficient thermistor.

6. A method (100) to measure a temperature of an exhaust fluid in a diesel exhaust fluid (DEF) system, said DEF system comprising a pump module, an exhaust fluid chamber and a Printed Circuit board (PCB) attached to the pump module through a fixation screw,
characterized in the method
- fastening an upper portion of a temperature measuring device to the fixation screw through at least one clip, said upper portion comprising the at least one clip (101); and
-fixing an end portion of the temperature measuring device to a housing of the exhaust fluid chamber, said end portion comprising a thermistor, said thermistor in a wired connection with the PCB (102).
7. The method (100) as claimed in Claim 6, wherein, measuring the temperature of the exhaust fluid by said PCB based on :
a pre-defined thickness of the housing of the exhaust fluid chamber, and
a change in resistance of the thermistor.

8. The method (100) claimed in Claim 6, wherein, filling a cavity in the end portion having the thermistor with a fluid, said fluid selected from a group of epoxides.

9. The method (100) as claimed in Claim 8, wherein, sealing a surface between the housing and the cavity having the thermistor and the fluid by a thermal paste.