阅读说明：本技术 温度感测单元和尿素传感器 (Temperature sensing unit and urea sensor ) 是由 N.詹森 B.B.莱 H.阿德兰 O.罗特维特 于 2019-07-12 设计创作，主要内容包括：本发明涉及可与尿素传感器一起使用的温度感测单元,且公开了组装这样的温度感测单元的方法。本发明还涉及尿素传感器和用于组装它的方法。温度感测单元,包括至少一个温度传感器(126,128)；以及基底(118),其包括至少一个第一区域(120)和至少一个第二区域(122)；其中所述至少一个温度传感器(126,128)布置在所述第二区域(122)中,且其中所述第二区域(122)远离所述第一区域(120)延伸。(The invention relates to a temperature sensing unit usable with a urea sensor, and discloses a method of assembling such a temperature sensing unit. The invention also relates to a urea sensor and a method for assembling it. A temperature sensing unit comprising at least one temperature sensor (126, 128); and a substrate (118) comprising at least one first region (120) and at least one second region (122); wherein the at least one temperature sensor (126, 128) is arranged in the second region (122), and wherein the second region (122) extends away from the first region (120).)

1. A temperature sensing unit comprising:

at least one temperature sensor (126, 128); and

a substrate (118) comprising at least one first region (120) and at least one second region (122);

wherein the at least one temperature sensor (126, 128) is arranged in the second region (122), and wherein the second region (122) extends away from the first region (120).

2. The temperature sensing unit of claim 1, wherein the first region (120) and the second region (122) are electrically and mechanically interconnected by an interconnect (132) comprising a flexible printed circuit board.

3. The temperature sensing unit of claim 2, wherein the substrate (118) comprises a rigid-flex circuit board, the second region (122) being disposed on a rigid portion of the rigid-flex circuit board.

4. The temperature sensor of any of the preceding claims, wherein at least one first temperature sensor (126) and at least one second temperature sensor (128) are disposed in the second region (122) to generate differential temperature-dependent signals.

5. The temperature sensing unit of claim 4, wherein the first temperature sensor (126) is arranged in the second region (122), the first temperature sensor (126) being at a greater distance from the first region (120) than the second temperature sensor (128) is at from the first region (120).

6. The temperature sensing unit of any one of the preceding claims, further comprising at least one third temperature sensor (130) arranged in the first region (120) of the substrate (118).

7. The temperature sensing unit of claim 6, operable to predict an external temperature by: combining a first temperature signal generated by at least one temperature sensor (126, 128) arranged in the second region (122) with a second temperature signal generated by at least one third temperature sensor (130) arranged in the first region (120).

8. The temperature sensing unit of any one of the preceding claims, wherein the second region (122) is at least partially enclosed in a separate temperature sensing housing element (134) protruding from a main cover (136) covering the first region (120) of the substrate (118).

9. A urea sensor module mounted in a urea tank, the urea sensor module (100) comprising a temperature sensing unit according to any of the preceding claims.

10. A urea sensor module as claimed in claim 8, wherein the urea sensor module (100) is mounted at an opening (114) of the urea tank (112) such that a sensor portion (110) extends to the interior of the urea tank (112), and wherein the temperature sensing unit is arranged at the sensor portion (110).

11. A urea sensor module according to claim 8 or 9, wherein the sensor portion (110) comprises at least one of a fluid level sensor and a fluid mass sensor arranged in a first region (120) of the substrate (118).

Technical Field

The invention relates to a temperature sensing unit usable with a urea sensor, and discloses a method of assembling such a temperature sensing unit. The invention also relates to a urea sensor and a method for its assembly.

Background

Selective Catalytic Reduction (SCR) reduction systems have been used to purify harmful NOx components in the exhaust of diesel vehicles. SCR systems use a urea solution, referred to as Diesel Exhaust Fluid (DEF), to purify the exhaust. The urea solution is stored in a urea tank provided on the vehicle. The proper composition and level of urea solution in the tank must be ensured to achieve efficient purification of the exhaust gases. Thus, a urea sensor is employed in the urea tank to measure the level and/or concentration and/or temperature of the urea solution in the tank.

The urea sensor is provided with a liquid level measuring device. Furthermore, a concentration and/or mass measuring device, a temperature measuring device, a suction pipe and a return pipe are provided. The suction pipe draws urea solution from the urea tank and provides the urea solution to decompose NOx in the exhaust gas, and the return pipe circulates excess urea solution back into the urea tank.

Because a temperature value is needed to calculate the concentration of DEF (e.g., based on the speed of sound in the liquid), an accurate temperature measurement is needed. In order to achieve a high accuracy of concentration measurements, the temperature in the liquid must be known accurately. Furthermore, since the freezing point of the urea solution is-11 ℃, there is a risk that the urea solution freezes at any temperature below-11 ℃. Chilled urea solutions can present problems and difficulties in efficiently decomposing NOx. This is because of the large volume expansion of the urea solution due to freezing, which can result in excessive pressure being generated inside the suction pipe. Therefore, it is very important to accurately monitor the temperature of the urea solution in the tank.

The existing temperature sensor is placed in close proximity to the heater or on the same Printed Circuit Board (PCB) as the remaining electronic components. Due to the heat generation of these electronic components, the temperature sensor is affected and its accuracy is reduced. Furthermore, the assembly concept of existing temperature sensors generally shows an unsatisfactory thermal coupling between the fluid and the temperature sensor through the potting material covering the PCB with the temperature sensor. On the other hand, temperature sensing units provided as separate components connected to the PCB (e.g. via a plug connector) are expensive and require additional assembly steps when mounting the temperature sensing unit.

There remains a need for a temperature sensor arrangement that can produce highly accurate measurements and that can be economically manufactured while being robust even in challenging application environments.

Disclosure of Invention

This object is solved by the subject matter of the independent claims. Advantageous embodiments of the invention are the subject matter of the dependent claims.

The invention is based on the idea that at least one temperature sensor of the temperature sensing unit is arranged on a common substrate with other electronic components, but in an area extending away from the rest of the substrate. In other words, the temperature sensor is arranged as a sort of tower, which protrudes from the rest of the Printed Circuit Board Assembly (PCBA). The temperature sensing unit according to the invention thus comprises at least one temperature sensor and a substrate comprising at least one first region and at least one second region. The at least one temperature sensor is arranged in the second region, and the second region extends away from the first region, for example in a direction through the first region. The plane defined by the second region and the plane defined by the first region may comprise an angle different from 0 °, preferably an angle between about 80 ° and 100 °, more preferably about 90 °. However, an angle of 0 ° is also possible. The angle can be chosen arbitrarily according to the respective spatial requirements. In the following, the protruding second region carrying the at least one temperature sensor is also referred to as "tower".

The advantage of this solution is that, on the one hand, the heat generated by the electronic components assembled in the first area of the PCB (this area is also referred to as the main area) does not interfere with the temperature measurement. Thus, the temperature of the fluid can be monitored more accurately. On the other hand, the temperature sensor may be in more direct contact with the liquid, thus resulting in a faster response time and further enhanced accuracy.

According to an advantageous embodiment of the invention, the first region and the second region are electrically and mechanically interconnected by an interconnect comprising a flexible printed circuit board. The advantage of this solution is that no cumbersome and expensive assembly and soldering is required and that the electrical contact is stable and robust even in the environment of challenging automotive applications. As is well known, a flexible printed circuit board is also called a Flexible Printed Circuit (FPC), a flexible circuit, or a flexible PCB.

Flexible printed circuits were originally designed to replace traditional wiring harnesses. The purest form of flex circuit is a large number of conductors bonded to a dielectric film. In connection with the present invention, however, it is intended that a flexible printed circuit board refers to a bendable support for electrically conductive leads and optionally also for active and passive electronic components, such as resistors, capacitors, inductors, sensors, and more complex monolithic components.

In particular, the substrate may comprise a rigid-flex circuit board, the second region being arranged on a rigid portion of the rigid-flex circuit board. Thus, the complete substrate comprising the first and second regions may be manufactured two-dimensionally, and the second region may be made the third dimension only when the substrate is mounted in the protective housing. Therefore, manufacturing can be significantly facilitated.

It is well known that for most rigid-flex circuits, the circuit is made up of multiple inner layers of flex circuits that are selectively attached together using an epoxy prepreg adhesive film, similar to a multilayer flex circuit. However, the multi-layer rigid-flex circuit requires rigid plates to be included on the outside, inside, or both, when the design is completed. Rigid-flex circuits combine the advantages of rigid boards and flexible circuits integrated together to form one circuit. The two-in-one circuits are interconnected, for example, by plated through holes (so-called vias). Rigid-flex circuits provide higher component density and better quality control. Where additional support is required, the design is rigid, while at the corners and areas where additional space is required, the design is flexible.

Alternatively, the substrate according to the invention can also be realized as a so-called MID component. MID is an abbreviation of the term "molded interconnect device" and encompasses three-dimensional circuit carriers injection molded from modified polymer materials. The modification may allow laser activation of the circuit traces on the surface of the circuit carrier, the activated areas being metallized in an electroless metal plating bath to create conductive traces extending therefrom to the third dimension. In addition to laser direct structuring techniques (addition and deletion), according to the present invention, two-shot injection molding, thermal embossing and insert molding can also be used to fabricate three-dimensional substrates that can be used for the temperature sensing unit according to the present invention.

According to a further advantageous embodiment, at least one first temperature sensor and at least one second temperature sensor are arranged in the second region to generate differential temperature-dependent signals. This differential measurement eliminates the effect of any common mode interference on the measurement results. Furthermore, two (or more) temperature sensors may also be provided for redundancy, so that if one sensor fails, temperature measurements can still be performed.

Advantageously, the first temperature sensor is arranged in the second region at a greater distance from the first region than the second temperature sensor. Thus, the two temperature sensors are arranged sequentially along the longitudinal axis of the second region, thus keeping the space requirement low.

According to an advantageous embodiment of the invention, the temperature sensing unit comprises at least one further temperature sensor arranged in the first region of the substrate. The further temperature sensor may act as a reference temperature sensor, which measures the temperature of the main PCB. By analyzing the temperature on the PCB, the temperature sensing unit is able to more accurately detect temperature changes in the fluid than the temperature in the tower. Since the reference sensor can be used to correct the measured temperature within the tower, the temperature response of the system can be significantly improved. This is particularly important under thawing conditions when the liquid temperature may change rapidly.

Further, the temperature sensing unit is operable to predict the external temperature by: the first temperature signal generated by the at least one temperature sensor arranged in the second area is combined with the second temperature signal generated by the at least one third temperature sensor arranged in the first area. For example, a suitable model relating the external temperature to the temperature difference between the two zones may be used to process the first and second temperature signals.

A particularly efficient thermal coupling of the temperature sensor to the liquid can be achieved when said second area is at least partially enclosed in a separate temperature sensing housing protruding from a module cover covering said first area of the substrate. It can be shown that in such a "tower" the temperature measured by the sensor reaches the true temperature of the liquid within ± 1 ℃ in 1.5 minutes, whereas a temperature sensor located on the PCBA takes more than 10 minutes to reach the same temperature.

The invention also relates to a urea sensor module mounted in a urea tank, comprising a temperature sensing unit according to the invention. By being able to accurately monitor the urea solution, the urea sensor module according to the invention has the advantage that in case of freezing, appropriate countermeasures can be taken, such as heating the liquid and/or flushing the supply line (and also the pump, the filter, etc., and all components located on this line), to prevent damage after freezing.

According to an advantageous embodiment of the invention, the urea sensor module is mounted at the opening of the urea tank such that the sensor portion extends into the interior of the urea tank, and wherein the temperature sensing unit is arranged at the sensor portion. In other words, the sensor part with the temperature sensing unit is not located at the base plate arranged close to the opening, but is arranged at the distal end of the urea sensor module in order to reach it further into the tank. This has the advantage that the temperature in the tank can be monitored more reliably, thereby enhancing the safety of the entire SCR system.

Advantageously, the sensor portion comprises at least one of a fluid level sensor and a fluid mass sensor arranged in a first region of the substrate, and the at least one temperature sensor of the temperature sensing unit is arranged in a second region of the substrate extending away from the main PCBA. An advantage of this arrangement is that any interference of the components assembled on the main PCB with the temperature monitoring can be kept low.

The invention can be used in a Selective Catalytic Reduction (SCR) system for purifying harmful NOx components in the exhaust gases of a diesel vehicle, comprising a urea tank and a urea sensor mounted in the urea tank for measuring one or several properties of a urea solution in the tank, and a temperature sensing unit according to the invention.

In addition, the temperature sensing unit according to the present invention may be assembled by a method including the steps of:

providing a substrate comprising at least one first region and at least one second region;

mounting at least one first temperature sensor and at least one second temperature sensor in a second region of the substrate;

wherein the second region extends in a direction across the first region.

In particular, the first region and the second region may be electrically and mechanically interconnected by an interconnect comprising a flexible printed circuit board, wherein the method comprises the step of bending the second region to a position where it extends through the first region. Thus, the electronic components can first be fully placed on the substrate by standard two-dimensional pick and place procedures, for example using SMT (surface mount technology) components which are reflow soldered to the substrate. The substrate is then bent such that the second region is disposed through a plane defined by the main PCB.

In order to allow for fast response times and high accuracy of the temperature sensing unit, the method further comprises the step of at least partially enclosing said second area in a separate temperature sensing housing protruding from the module cover covering said first area of the substrate.

A particularly simple and accurate way of enclosing the second region in a tower-shaped separate housing may be achieved by providing a recess in the interior of the temperature sensing housing into which recess formed in the interior of the temperature sensing housing the second region is inserted. The arrangement may be mechanically fixed, for example by filling some potting material covering the interconnection between the first and second areas of the substrate.

In order to allow reference measurements to be made close to the main PCB, a third (reference) temperature sensor is assembled in said first area of the substrate. This step may be performed substantially simultaneously with installing the at least one temperature sensor in the second region.

Finally, a method of assembling a urea sensor module installed in a urea tank may comprise performing the steps according to the above method to assemble a temperature sensing unit, wherein the urea sensor module is installed at an opening of the urea tank such that a sensor portion extends into an interior of the urea tank, and wherein the temperature sensing unit is arranged at the sensor portion.

Drawings

The accompanying drawings are incorporated in and form a part of the specification to illustrate several embodiments of the present invention. Together with the description, the drawings serve to explain the principles of the invention. These drawings are merely for purposes of illustrating preferred and alternative examples of how the invention may be made and used, and are not to be construed as limiting the invention to only the embodiments shown and described. Furthermore, several aspects of the embodiments may form the solution according to the invention, individually or in different combinations. The embodiments described below can therefore be considered individually or in any combination thereof. Further features and advantages will become apparent from the following more particular description of various embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same elements, and in which:

FIG. 1 is a schematic perspective view of a urea sensor module;

FIG. 2 is a schematic diagram of a urea tank with a urea sensor module installed therein;

FIG. 3 is a schematic cross-sectional view of an electronic module including a temperature sensing unit;

FIG. 4 is a layout of a substrate of an electronic module;

FIG. 5 is a schematic perspective view of an electronic module;

fig. 6 is a schematic diagram illustrating a temperature response of a temperature sensing unit according to the present invention.

Detailed Description

The invention will now be explained in more detail with reference to the drawings and first to fig. 1.

Fig. 1 shows a perspective view of a urea sensor module 100 according to the invention. The urea sensor module 100 has a base plate 102 that is mounted in an orifice of a urea tank belonging to a Selective Catalytic Reduction (SCR) system. A urea intake line 104 and a urea return line 106 are provided for transporting the urea solution. It is necessary to provide a heating line 108 to heat the urea solution.

At the distal end of the urea sensor module 100, opposite the base plate 102, a sensor portion 110 is arranged. The sensor part according to the invention comprises a temperature sensing unit according to the principles of the invention, but also a urea solution quality sensor, e.g. based on the ultrasonic principle, and an Electronic Control Unit (ECU) for driving and evaluating the sensor components.

FIG. 2 schematically illustrates the installation of the urea sensor module 100 inside the urea tank 112. According to the present invention, sensor portion 110 is disposed away from an orifice 114 provided within urea tank 112 for insertion of urea sensor module 100. Thus, all sensors are located in close proximity to the bottom 116 of the urea tank 112, which is advantageous for temperature sensing and accuracy of mass measurement.

Fig. 3 shows a schematic cross-sectional view of the sensor portion 110 shown in fig. 2. In accordance with the present invention, the sensor portion 110 has a substrate 118 having a first region 120 and a second region 122. The second region 122 extends in a direction substantially at right angles to the plane defined by the first region 120, as shown by axis 124. However, it is obvious to the person skilled in the art that any other angle than 0 ° may also be advantageously used (preferably between 80 ° and 100 °).

An electrical interconnection between the first region 120 and the second region 122 is established by providing a flexible interconnection region 132. Preferably, the complete substrate 118 is formed of a rigid-flex substrate, wherein the first region 120 and the second region 122 comprise rigid printed circuit boards, and the interconnect region 132 is formed of a flex board, which configuration has the following advantages: the complete substrate may be fabricated and assembled with electronic components before bending the second region 122 to a final position.

In the second region 122, a first temperature sensor 126 and a second temperature sensor 128 are arranged along the axis 124. However, according to the present invention, only one temperature sensor or more than two temperature sensors may be arranged in the second region 122. According to the present invention, the first temperature sensor 126 and the second temperature sensor 128 are formed of, for example, NTC sensors. These negative temperature coefficient resistors can be used as integrated SMT components and have the advantage of providing accurate temperature dependent signals, while being robust and long term stable. It will be apparent, however, that any other suitable temperature sensing element, such as a thermocouple or the like, may be employed.

According to the invention, the second region 122 carrying the at least one temperature sensor 126, 128 is enclosed in a separate housing element 134, the housing element 134 projecting from a main cover 136, the main cover 136 covering the first region 120 in which the electronic components are arranged. The second region 122 thus forms a kind of "tower" in its housing element 134, protruding from the main cover 136 of the sensor part 110.

As schematically shown in fig. 3 (although it must be noted that the figure is not drawn to scale), the protective casing element 134 is much thinner than the cover 136 so that the fluid 138 in which the central portion 110 is immersed has a more direct thermal contact with the temperature sensors 126, 128.

Further, a third temperature sensor 130 forming a reference temperature sensor may be disposed in the first region 120. By analysing the temperature across the first region 120 (which forms the main PCBA of the sensor portion 110), temperature changes in the liquid 138 can be detected compared to the temperature in the power. This can be used to correct the measured temperature in the column to improve the temperature response of the system. This is particularly important under thawing conditions when the liquid temperature may change rapidly. The reference temperature sensor 130 may also be an NTC temperature sensor. It will be apparent, however, that any other suitable temperature sensing element, such as a thermocouple or the like, may be employed.

As described above, existing SCR systems only use temperature sensors on the PCBA, and therefore self-heating of the PCBA can affect the temperature measurement and reduce the accuracy of the system. Furthermore, the conventional temperature sensor is also less thermally coupled to the liquid due to the low thermal conductivity of the potting material surrounding the PCBA. However, the solution according to the invention only allows using an optional temperature sensor 130 provided on the PCBA as a reference and measuring the fluid temperature by means of at least one temperature sensor 126, 128 arranged within a protruding housing element 134.

Fig. 4 shows a layout of a substrate 118 according to an exemplary embodiment of the present invention according to this example, the first region 120 being formed by a rigid printed circuit board carrying a plurality of electronic components, including a control unit 140. The second region 122 is also formed by a rigid circuit board, in particular a first temperature sensor 126 and a second temperature sensor 128. In the illustrated embodiment, the temperature sensors 126, 128 are formed by NTC elements. The first region 120 and the second region 122 are interconnected to each other by a flexible interconnection region 132. The interconnect region 132 includes electrically conductive leads for connecting the temperature sensors 126, 128 to the control unit 140.

In addition, a reference temperature sensor 130 adapted to measure the temperature on the main PCB is arranged in the first region 120.

Furthermore, the first area 120 forming the main PCB may also be connected to at least one further rigid substrate 144 via a second flexible interconnect area 142. Advantageously, the complete substrate 118 as shown in fig. 4 is formed as an integrated rigid-flex PCB.

Fig. 5 shows in a schematic perspective view how the base 118 is arranged in the protective cover 136. A protruding housing element 134 extends from a surface of the main cover 136 and includes the second region 122 with the temperature sensors 126, 128. Furthermore, the first region 120 of the substrate carries at least one temperature sensor 130 for measuring the temperature in the vicinity of the electronic control unit 40.

Hereinafter, the assembly of the temperature sensing unit 100 according to the present invention will be explained in detail with reference to fig. 3 to 5. In a first step, a substrate 118, such as shown in FIG. 4, is provided having rigid and flexible regions. Electronic components, such as an electronic control unit 140 and an optional reference temperature sensor 130, are assembled in the first region 120. At least one temperature sensor 126, 128 is located in the second region 122. According to the present invention, all electronic components can be mounted in a pick and place assembly step and will be electrically connected by a subsequent reflow soldering step. The substrate 118 is advantageously flat, as shown in FIG. 4. In a next step, copper 136 with raised housing element 134 is provided and second region 122 is slid into a recess provided inside housing element 134 in a direction along axis 126. This is possible because the electrical interconnection between the first region 120 and the second region 122 is formed by the flexible interconnection region 132. In a final step, a potting material may be molded around the first region 122 and the flexible interconnect region 132. This process allows a safe and stable electrical connection between the temperature sensors 126, 128 and the electronic control unit 114, while the manufacturing process is particularly simple and fast. On the other hand, fast response times and optimal thermal coupling of temperature sensors 126, 128 to fluid 138 may be achieved.

In summary, a method of assembling a temperature sensing unit may comprise the steps of: providing a substrate 118 comprising at least one first region 120 and at least one second region 122; mounting at least one temperature sensor 126, 128 in the second region 122 of the substrate 118; wherein the second region 122 extends away from the first region 120.

Further, said first region 120 and said second region 122 are electrically and mechanically interconnected by an interconnect 132 comprising a flexible printed circuit board, and wherein the method comprises the step of bending the second region to a position where it extends through the first region 120.

The method may include the step of at least partially enclosing said second region 122 in a separate temperature sensor housing element 134 projecting from a main cover 136 covering said first region of the base 118.

Preferably, the second region 122 is inserted into a recess formed inside the temperature sensor housing element 134.

Fig. 6 shows the temperature response behavior of the temperature sensing unit 100 according to the present invention. In particular, curve 600 (shown as a dashed line) illustrates a temperature gradient of 50 ℃ in fluid 138. As shown by curve 601, it takes about 10 minutes for the temperature sensor 130 disposed in the first region 120 under the main cover 136 to reach the full amplitude of the signal corresponding to the fluid temperature gradient. In contrast, as shown in curve 602, the differential signal of the first temperature sensor 126 and the second temperature sensor 128 represents the full volume (full scale) of the temperature signal that has corresponded to a 50 ℃ temperature gradient in the fluid after approximately 1.5 minutes.

In summary, the concept of placing the temperature sensor in a "tower" increases the thermal coupling of the sensor to the liquid while reducing the coupling to the PCBA. This has two effects. Firstly, sensors respond more quickly to temperature changes in the fluid, and secondly, they are less susceptible to self-heating by the PCBA. Furthermore, the temperature sensor is mounted on a PCB part which is connected to the main PCBA via an integrated flex cable. This improvement eliminates the need for manual welding and greatly simplifies the manufacturing process, thereby reducing costs. Furthermore, by spatially separating the temperature measurements from the "tower" and from the PCBA, detection of temperature changes in the liquid may be improved, and greater accuracy may be achieved.

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