Patent Publication Number: US-2016222860-A1

Title: Module for an scr system and system comprising same

Description:
The present invention pertains to systems for selective catalytic reduction of NO in the exhaust gas of internal combustion engines. In particular, the present invention pertains to a module including sensors for assessing properties of the content of a urea tank (for example, temperature and/or quality). 
     International patent application publication WO 2007/141312 A1 in the name of the present applicant discloses a system for storing an internal combustion engine exhaust gas liquid additive, the said system comprising a tank for storing the additive and an “immersed” baseplate positioned through an opening made in the bottom wall of the tank, the said baseplate comprising at least one orifice through which a system for injecting the said additive into the exhaust gases can be fed, and also incorporating at least one other active component of the storage system and/or of the injection system. It is known from this document to equip the base plate with a temperature sensor, a quality sensor, or a pressure sensor. This document does not address the spatial issues of placing multiple sensors on the base plate. If the system needs to accommodate multiple sensors, it is customary to arrange one or more sensors at a different place in the tank, off the base plate. 
     It is an object of embodiments of the present invention to overcome this disadvantage. According to an aspect of the invention, there is provided a module for an SCR system, the module having a base plate with a socket and a first sensor ( 101 ) mounted in said socket, the module further comprising an electrical interface connected to a first sensor ( 101 ) of a first type, wherein said electrical interface is also adapted to alternatively connect to a second sensor ( 102 ) of a second type. 
     Thus it is proposed a module with a versatile electrical interface. In other words, the module is equipped with an electrical interface with can operate with a sensor of a first type, and which can also operate with a sensor of a second type. 
     Thus, in a first configuration, the electrical interface is connected with a sensor of a first type. In a second configuration, the electrical interface is connected with a sensor of a second type. 
     For instance, said first sensor is a combined temperature and urea quality sensor, and said second sensor is a temperature sensor. 
     Embodiments of the present invention are based on the insight of the inventor that while it may be possible to place a combined quality and temperature sensor on the base plate to save space, this would require a redesign of the entire module. In addition, the resulting module would be more expensive, regardless of whether the quality measurement function is actually desired by the end customer. Thus, the invention provides a module architecture that supports a combined quality and temperature sensor, which could be replaced by a temperature sensor depending on the requirements of the customer, without requiring substantive modifications. In some embodiments, minor modifications may be needed, as will be described in more detail below. 
     The urea quality is any physical feature specific to the urea. 
     For instance, this quality is the concentration of urea. This quality may then be measured directly, or indirectly through the measurement of another physical feature of the urea, such as viscosity, capacity, density, opacity. 
     According to an aspect of the invention, there is provided an SCR system comprising a module as described above and an ECU, the electrical interface connecting the combined temperature and urea quality sensor to the ECU, wherein the ECU is configured to read out a signal received via the electrical interface as digital sensor data. In an embodiment of the SCR system according to the present invention, the ECU is further configured to read out a signal received from the electrical interface as analog sensor data, when the signal originates from a temperature sensor. 
     It is an advantage of this embodiment that the SCR system may be equipped with a combined quality and temperature sensor, or a temperature sensor, depending on the requirements of the customer, without requiring modifications of the wiring or the ECU. 
     In a variant of this embodiment, the first sensor is a combined temperature sensor, quality sensor, and a urea level sensor, and the second sensor is a temperature sensor and a urea level sensor. 
     A further advantage is that said sensor is able to take measurements at the point closest to the urea suction point. 
     According to an aspect of the invention, there is provided a motor vehicle comprising the SCR system as described above. 
    
    
     
       These and other aspects and advantages of the present invention will now be described in more detail with reference to the accompanying drawings, in which: 
         FIG. 1  represents a module according to an embodiment of the present invention; and 
         FIG. 2  represents a module having a slightly different socket, in which a temperature sensor is mounted instead of a combined temperature and quality sensor. 
     
    
    
       FIG. 1  represents a base plate  110  of a delivery module for a vehicular fluid tank, in particular a urea solution tank of an SCR system. Reference is made to WO 2009/007405, in the name of the present applicant, for a detailed description of a known module. Fluid communication between the inside and the outside of the tank is achieved by means of tubes passing through the base plate  110  (not visible in the views reproduced here). The base plate  110  is sometimes referred to in the art as the “flange”. The module may be attached to a tank wall by placing it over an opening provided for that purpose, and securing it. 
     The module of  FIG. 1  integrates a combined quality and temperature sensor  101 , i.e. a quality sensor also capable of measuring temperature. This allows replacing the temperature sensor of current designs by the quality and temperature sensor. The module design and the electronic architecture according to the invention are such that the combined quality and temperature sensor, and the “legacy” temperature sensor of the SCR module become intercheangeable. 
     In  FIG. 2 , the module is shown with a legacy temperature sensor  102 . 
     The interchangeability may be achieved with physically identical module forms (i.e., where the two types of sensors have the same footprint and the same mechanical mounting means), or with different module forms which can be produced with minimal changes to the moulding process (e.g., by moulding the actual mounting socket by means of an interchangeable socket). In both cases, the production process becomes highly uniform for both variants. In particular, the electrical interface at the bottom of the base plate (the side facing outwards of the tank, not visible in the views reproduced here) is identical for both variants, such that no distinction needs to be made in the further wiring and assembly process. 
     The ECU is preferably capable of correctly reading the incoming signal on the same wire pair, regardless of whether the connected sensor is a combined quality and temperature sensor or a temperature sensor, notwithstanding the fact that sensors of the former type typically provide a digital signal, while sensors of the latter type provides an analog signal. The inventors have found that this effect can be achieved by branching the sensor signal in parallel towards a digital I/O port and to an analog (diagnostic) port. When the digital sensor signal on the digital input port is detected as timeout (continuous analog signal) and there is no fault detected on analog (diagnostic) input, then the temperature sensor is connected and the analog (diagnostic) port is used to measure the temperature sensor signal; otherwise the combined quality and temperature sensor is connected and the digital port is used to read the signal from the combined quality and temperature sensor. 
     The module of the present invention may be mounted in a urea tank of an SCR system. The SCR system may be arranged in a vehicle with an internal combustion engine. 
     While the invention has been described hereinabove with reference to separate embodiments, this was done for clarifying purposes only. The skilled person will appreciate that features described in connection one embodiment, can also be applied to other embodiments, with the same technical effects and advantages. Furthermore, the scope of the invention is not limited to these embodiments, but is defined by the accompanying claims.