CIRCUIT

BACKGROUND

[001] In a selective catalytic reduction (SCR) exhaust gas aftertreatment system, a liquid reducing agent such as a urea- water solution is injected when required into the exhaust gas duct of an internal combustion engine by means of a dosing module that includes an

electromagnetically controllable metering valve. This enables a catalytic reduction of nitrogen oxide to take place in an SCR catalytic converter. The urea thereby dissociates to ammonia (NEL), which reacts with the nitrogen oxides (NO _x ) and converts them into non-toxic water (H ₂ 0) and nitrogen (N ₂ ).

[002] The dosing module used in this process is mounted on the vehicle exhaust duct, and includes an injector that protrudes into the duct, the metering valve that controls supply of the solution to the injector, and a drive unit that actuates the metering valve. The drive unit includes a magnetic coil, whose magnetic field lifts a valve element of the metering valve from a valve seat and in doing so opens the metering valve. To protect the dosing module from high temperatures associated with the exhaust gas duct, during normal vehicle operation, the dosing module may be cooled via a branch of the engine coolant circuit that passes through the dosing module housing.

[003] In some applications, during a hot shut-down of a vehicle, the urea-water solution that is inside the injector begins to boil since coolant is no longer flowing from the engine. As the amount of water in the solution decreases and the urea becomes relatively concentrated, the freezing or crystallization point of the solution changes. As a result, crystalized urea forms at normal ambient temperatures. The crystallization formed within the metering valve may prevent movement of the injector needle.

[004] During the next vehicle drive cycle, if the injector needle is prevented from movement due to the presence of the crystallized solution, the reducing agent can no longer be metered, resulting in increased emissions of nitrogen oxides by the motor vehicle. In order to free the injector needle, the crystalized area must be heated to a temperature at which the crystals melt.

In some cases, heat from the exhaust gas may be used to heat up the dosing module since the dosing module is mounted on the vehicle exhaust duct. However, in some applications during vehicle start up, the coolant is much lower in temperature than the temperature of the exhaust gas duct, and can prevent adequate heating of the metering valve by the exhaust gas duct.

[005] It is desirable to provide a dosing module that permits sufficient heating of the dosing module including the injector to melt any crystallization therein by addressing the effect of relatively cold coolant within the coolant circuit. By addressing the effect of relatively cold coolant within the coolant circuit and thereby permitting sufficient heating of the dosing module injector, the immobilizing effects of the crystallization can be easily addressed, and uninterrupted operation of the exhaust gas aftertreatment system can be provided.

SUMMARY

[006] In some aspects, an exhaust gas aftertreatment system for an internal combustion engine includes a dosing module. The dosing module includes an injector having a discharge opening and configured to inject a reducing agent into a duct of the exhaust gas aftertreatment system, a metering valve that meters a supply of the reducing agent to the discharge opening, and a drive unit that actuates the metering valve. The system includes a coolant circuit including a delivery portion that directs coolant from the internal combustion engine to an inlet of a coolant passageway formed in the dosing module, and a return portion that returns coolant from an outlet of the coolant passageway and returns it to the internal combustion engine. The system further includes a flow control device that is disposed in the coolant circuit and is configured to control coolant flow through the coolant circuit based on a temperature of the coolant within the coolant circuit.

[007] In some embodiments, the flow control device is a thermostatic wax thermostat.

[008] In some embodiments, the flow control device is a bimetal thermostat.

[009] In some embodiments, the flow control device includes a temperature sensor that detects a temperature of the coolant in the coolant circuit, and a coolant control valve disposed in the coolant circuit. The valve is configured to move between a first position in which coolant is permitted to flow through the coolant passageway, and a second position in which coolant is prevented from flowing through the coolant passageway. [0010] In some embodiments, the coolant control valve is a graduated device in that it can be configured to be fully open, partially open and fully closed.

[0011] In some embodiments, the flow control device further includes a coolant bypass passage that bypasses the coolant passageway. The coolant bypass passage has an inlet in the delivery portion, and an outlet in the return portion, and the coolant control valve is configured to move between the first position in which coolant is directed from the coolant line to the coolant passageway inlet and coolant flow to the coolant bypass passage is prevented, and the second position in which coolant is directed from the coolant line to the bypass passage inlet and coolant flow to the coolant passageway is prevented.

[0012] In some embodiments, the flow control device is disposed in the delivery portion.

[0013] In some embodiments, the flow control device is disposed in the return portion.

[0014] In some embodiments, the flow control device is disposed in the coolant passageway.

[0015] In some embodiments, the flow control device prevents coolant flow to the dosing module if a temperature of the coolant is below a predetermined temperature.

[0016] In some aspects, a method is provided for controlling an emissions reduction system of an internal combustion engine at a time of starting the internal combustion engine. The method includes controlling flow of coolant through the coolant passageway via the flow control device based on a temperature of the coolant within the coolant circuit.

[0017] In some embodiments, the flow control device is a thermostatic wax thermostat that is used to detect a temperature of the coolant within the dosing module cooling circuit and to control flow of coolant through the coolant passageway based on the detected temperature of the coolant.

[0018] In some embodiments, the flow control device is a bimetal thermostat that is used to detect a temperature of the coolant within the dosing module cooling circuit and to control flow of coolant through the coolant passageway based on the detected temperature of the coolant.

[0019] In some embodiments, the flow control device includes a coolant circuit temperature sensor that detects a temperature of the coolant in the coolant circuit, and a coolant control valve disposed in the coolant circuit. The valve is configured to move between a first position in which coolant is permitted to flow through the coolant passageway, and a second position in which coolant is prevented from flowing through the coolant passageway. In the method, when a detected temperature corresponding to an output of the coolant circuit temperature sensor is less than a predetermined temperature, the coolant control valve is controlled to reduce a coolant flow amount through the coolant passageway.

[0020] In some embodiments, when the detected temperature is less than a predetermined temperature, the coolant control valve is controlled to prevent a flow of coolant through the coolant passageway.

[0021] In some embodiments, the flow control device further comprises a coolant bypass passage that bypasses the coolant passageway. The coolant bypass passage has an inlet in the delivery portion, and an outlet in the return portion. In the method, when the detected temperature is less than a predetermined temperature, the coolant control valve is controlled to direct at least a portion of the coolant within the coolant circuit to the coolant bypass passage.

[0022] In some embodiments, the system is configured to determine a temperature of the dosing module, and the method includes the following method steps: following the step of controlling flow of coolant through the coolant passageway based on the detected temperature of the coolant, determining a temperature of the dosing module; and adjusting a flow of coolant through the coolant passageway based on a detected temperature of the dosing module.

[0023] In some aspects, an exhaust gas aftertreatment system includes a dosing module that includes an injector having a discharge opening and configured to inject a reducing agent into a duct of the exhaust gas aftertreatment system, a metering valve that meters a supply of the reducing agent to the discharge opening, and a drive unit that actuates the metering valve. The system further includes a coolant circuit that supplies a coolant passageway formed in the dosing module, and a flow control device that is disposed in the coolant circuit and is configured to control coolant flow through the coolant circuit based on a temperature of the coolant within the coolant circuit. -By providing a flow control device in the coolant circuit, a temperature of the dosing module can be controlled whereby it is possible to dislodge an immobilized injector needle. As a result, operation of the dosing module is provided, allowing for treatment of vehicle emissions during vehicle start up and normal vehicle operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Exemplary embodiments of the invention are subsequently described in detail using the figures. The following are shown:

[0025] Fig. 1 is a schematic diagram of exhaust gas aftertreatment system of an internal combustion engine.

[0026] Fig. 2 is a longitudinal cross sectional view of the metering module from FIG. 1.

[0027] Fig. 3 is a schematic diagram of the dosing module cooling circuit.

[0028] Fig. 4 is a schematic diagram of an alternative embodiment dosing module cooling circuit.

[0029] Fig. 5 is a schematic diagram of another alternative embodiment dosing module cooling circuit.

[0030] Fig. 6 is a flow chart illustrating a method of controlling the exhaust gas aftertreatment system.

DETAILED DESCRIPTION

[0031] Referring to Fig. 1, an internal combustion engine 10 of a vehicle includes an exhaust gas aftertreatment system 12 and an engine control unit 14. The engine control unit 14 controls the internal combustion engine 10 and in so doing receives signals of a sensor system 16 concerning operating parameters of the internal combustion engine 10 and processes the signals to actuating variables for actuators 18 of the internal combustion engine 10. The signals of the sensor system 16 typically allow the engine control unit 14 to determine the air mass drawn in by the internal combustion engine 10, the position of the angle of rotation of a crankshaft of the internal combustion engine 10, a temperature of the internal combustion engine 10, etc. The engine control unit 14 typically forms actuating variables for metering fuel into combustion chambers of the internal combustion engine 10, for setting a supercharging pressure of an exhaust gas turbo charger, for setting an exhaust gas return rate, etc. [0032] In addition, the engine control unit 14 is set up for, including programmed for, controlling the course of events of at least one method, an example of which is described below, and/or one embodiment of such a method.

[0033] The exhaust gas aftertreatement system 12 includes an oxidation catalytic converter 20 and an SCR catalytic converter 22. A dosing module 24 is disposed between the oxidation catalytic converter 20 and the SCR catalytic converter 22. The dosing module 24 is supported on a duct of the exhaust gas aftertreatment system 12 and is configured to inject the reducing agent 26 from a reservoir 28 into the duct. The reducing agent 26 is, for example, an aqueous urea solution of 32.5 percent urea and 67.5 percent deionized water, frequently sold under the registered trademark AdBlue. The system 12 includes a pump 32 that directs fluid from the reservoir 28 to the dosing module 24. In the illustrated embodiment, the pump 32 is integrated into the reservoir 28, but in other embodiments, the pump 32 is part of a supply module 34 that may be a separate unit (Fig. 3).

[0034] The control unit 14 actuates the dosing module 24 via a control current which flows through a magnetic coil (not visible in FIG. 1) of the dosing module 24. In so doing, the dosing module 24 is supplied with the reducing agent 26 via a feed line 30, which is supplied with reducing agent 26 by the pump 32. The pump 32 may be a double-acting pump, which during the pressure operation produces the necessary injection pressure for metering the reducing agent 26 into the exhaust gas system 12 and which during the suction operation allows the feed line 30 to be emptied of reducing agent 26. The pump 32 may be controlled by the engine control unit 14 to meet this objective.

[0035] In addition, different sensors 36, 38, 40, 42, 43 and 44, which acquire operating parameters of the exhaust gas system 12 and deliver corresponding data to the engine control unit 14, are provided for controlling the selective catalytic reduction of nitrogen oxides by means of a metering of reducing agent 26 to the exhaust gas aftertreatment system 12 of the internal combustion engine 10. The sensors 36, 40 and 43 are temperature sensors, and the sensor 38 serves to acquire the NOx concentration in the exhaust gas upstream of the SCR catalytic converter 22. Another NOx sensor 42 is disposed downstream of the SCR catalytic converter 22. The sensor 44 detects an ammonia concentration in the exhaust gas downstream the SCR catalytic converter 22 and thus allows for the determination of an overdosage of reducing agent 26. As used herein, the terms“upstream” and“downstream” refer to a position relative to a direction of exhaust gas flow within the system. A fill level sensor 45 acquires the reducing agent fill level in the reservoir 28 and delivers a corresponding signal to the engine control unit 14.

[0036] Referring to Fig. 2, the dosing module 24 includes an injector 46, an electromechanical drive unit 48, a hydraulic connection unit 50 that connects to the feed line 30 that delivers the reducing agent 26 to be metered and an electrical current feed unit 52. In addition, the dosing module 24 includes a heating element 82 that is configured to heat the injector 46 during selected operating conditions, as discussed further below.

[0037] The injector 46 has a sleeve-shaped first housing 54. The injector 46 includes a metering valve 47and a perforated injection disc 64, which are disposed in the first housing 54. The metering valve 47 has an injector needle 56 that is axially guided in the first housing 54. A free end of the injector needle 56 is connected to a spherical valve element 58. The valve element 58 interacts with a valve seat 60. Within the injector needle 56, a guide tube 62 is guided centrally and axially as a feed line for the reducing agent 26. The guide tube 62 ends in the direction of flow 63 at a location that is somewhat above the valve element 58. The injection disc 64 is disposed beneath the valve element 58 and covers an orifice outlet 66 out of the injector 46 through which the reducing agent 26 is discharged. The injection disc 64 may be approximately 150 micrometers thick and comprises disc openings 65 for the discharge of the reducing agent 26.

[0038] In FIG. 2, the drive unit 48 is disposed above the injector 46. The drive unit 48 includes an armature 68 disposed in the extension of the injector needle 56, via which the injector needle 56 can be axially moved with the valve element 58. In particular, the injector needle 56 is axially movable in the first housing 54 between a first position in which the valve element 58 engages the valve seat 60 whereby the metering valve 47 is closed, and a second position in which the valve element 58 is spaced apart from the valve seat 60 whereby the metering valve 47 is open. The armature 68 is moved by the magnetic force produced in a magnetic coil 70. The drive unit 48 is enclosed by a second housing 72.

[0039] A third housing 74 includes the hydraulic connection unit 50 that delivers the reducing agent 26 to be metered and the electrical current feed unit 52. The third housing 74 is fitted, for example screwed, on the second housing 72. The hydraulic connection unit 50 has in the center a connecting channel 76 that receives the reducing agent 26 to be metered. The connecting channel 76 is hydraulically connected to the controllable double-acting pump 32 (Fig. 1). The double-acting pump 32 delivers the reducing agent 26 into the connecting channel 76, where an element acting as a pressure valve 80 is disposed in the direction of flow 63. The element then delivers the reducing agent 26 into the region of a guide tube opening 82. The electrical current feed unit 52 with a socket 84, which accommodates a connector having power supplying lines (not shown) for the magnetic coil 70, is disposed laterally on the third housing 74.

[0040] Referring to Fig. 3, the dosing module 24 includes a coolant passageway 25 that is part of a coolant circuit 90 that delivers coolant discharged from the internal combustion engine 10 to the dosing module 24. The dosing module coolant passageway 25 extends between an inlet 27 and an outlet 29. The coolant passageway inlet 27 receives coolant from a delivery portion 92 of the coolant circuit 90 that directs coolant from the internal combustion engine 10 to the dosing module 24. The coolant passageway outlet 29 discharges coolant from the dosing module 24 into a return portion 94 of the coolant circuit 90 that returns coolant to the internal combustion engine 10.

[0041] A flow control device 96 is disposed in the coolant circuit 90. The flow control device 96 is configured to control coolant flow through the coolant circuit 90 based on a temperature of the coolant within the coolant circuit 90. In the illustrated embodiment, the flow control device 96 is a thermostat, for example a thermostatic wax thermostat 98, that is integrated into the delivery portion 92 of the coolant circuit 90. In some embodiments, the thermostatic wax thermostat 98 may include a wax pellet inside a sealed chamber (not shown). The wax pellet is solid at low temperatures, and as the coolant heats up, the wax melts and expands. The sealed chamber operates a rod which opens a valve (not shown) when a predetermined temperature is exceeded. The predetermined temperature is fixed, but is determined by the specific composition of the wax, so thermostats of this type are available to maintain different temperatures. Thermostatic wax thermostat 98 is configured so that the thermostat valve is closed and coolant flow to the dosing module 24 is prevented if a temperature of the coolant is below the predetermined temperature. During the time the coolant is not flowing into the dosing module coolant passageway 25, the temperature of the dosing module injector 46 is allowed to rise due to heating by nearby structures such as the exhaust duct, and crystals within the injector 46 are melted.

[0042] Although in the embodiment illustrated in Fig. 3, the flow control device 96 is a thermostatic wax thermostat 98, the flow control device 96 is not limited to this type of thermostat. Alternative thermostats such as a bimetal thermostat or other appropriate thermostat can be used, and the specific type of thermostat used depends on the requirements of the specific application.

[0043] Although in the embodiment illustrated in Fig. 3, the flow control device 96 is located within the delivery portion 92 of the coolant circuit 90 (e.g., on an inlet side of the dosing module coolant passageway 25), the flow control device 96 is not limited to this location. For example, in other embodiments, the flow control device 96 may be located in the return portion 94 of the coolant circuit 90 (e.g., on an outlet side of the dosing module coolant passageway 25), or in the dosing module coolant passageway 25.

[0044] Although in the embodiment illustrated in Fig. 3, the flow control device 96 is a thermostat 98, the flow control device 96 is not limited to being a thermostat, and other devices that are configured to control coolant flow through the coolant circuit 90 based on a temperature of the coolant within the coolant circuit 90 may be used. Referring to Fig. 4, in a first example, an alternative embodiment coolant circuit 190 includes a flow control device 196 having a temperature sensor 100 that detects a temperature of the coolant in the coolant circuit 190 and a coolant control valve 102. The flow control device 196 detects a temperature of the coolant in the coolant circuit 190 via the temperature sensor 100, and reduces or prevents coolant flow to the dosing module 24 if a temperature of the coolant is below a predetermined temperature. To this end, the coolant control valve 102 is disposed in the coolant circuit 190 (in the illustrated embodiment, the coolant control valve is disposed in the coolant circuit delivery portion 92, but is not limited to this location) and is configured to move between a first position (e.g., an open position) in which coolant flow within the coolant circuit 190, including the dosing module coolant passageway 25, is permitted, and a second position (e.g., a closed position) in which coolant flow within the coolant circuit 190, including the dosing module coolant passageway 25, is prevented. [0045] In some embodiments, the coolant control valve 102 is binary in that it can be configured to be fully open, permitting unrestricted flow of coolant within the coolant circuit 190 to the coolant passageway 25, or fully closed, preventing flow of coolant within the coolant circuit 190 to the to the coolant passageway 25. In other embodiments, the coolant valve 102 is graduated in that it can be fully open, partially open so as to permit a portion of the flow of coolant within the coolant circuit 90 flow to reach the coolant passageway 25, or fully closed.

[0046] Referring to Fig. 5, in a second example, another alternative embodiment coolant circuit 290 includes a flow control device 296 having the temperature sensor 100, a coolant bypass passage 204 that is in fluid communication with the coolant circuit 290 and bypasses the dosing module coolant passageway 25, and the coolant control valve 102. The flow control device 296 detects a temperature of the coolant in the coolant circuit 290 via the temperature sensor 100, and reduces or prevents coolant flow to the dosing module 24 if a temperature of the coolant is below a predetermined temperature. To this end, the coolant control valve 102 is disposed in the coolant circuit delivery portion 92 and is configured to move between a first position (e.g., a non-bypass position) in which coolant is directed from the coolant circuit delivery portion 92 to the dosing module coolant passageway inlet 27 and coolant flow to the coolant bypass passage 204 is prevented, and a second position (e.g., a bypass position) in which coolant is directed from the coolant circuit delivery portion 92 to the coolant bypass passage 204 and coolant flow to the dosing module coolant passageway 25 is prevented. As in the earlier example, the coolant control valve may control flow between the coolant circuit 290 and the coolant bypass passage in either a binary or graduated manner.

[0047] In some embodiments, the position of the coolant valve 102 may be controlled based on a temperature of the dosing module 24 and/or the components of the dosing module 24. Typically, the temperatures of the dosing module components are modeled within the engine control unit 14, for example based on factors such as vehicle speed, exhaust gas temperature, ambient temperature, and coolant temperature. Alternatively, rather than calculating a dosing module temperature, in some embodiments, the temperature of the dosing module 24 may be detected by a dedicated dosing module temperature sensor 43 (Fig. 1). Advantageously, this permits controlled heating of the dosing module 24 in that the amount of coolant allowed to flow through the coolant passageway can be adjusted (increased or decreased) to allow for melting of the crystals while preventing overheating of dosing module components beyond component heating limits.

[0048] Referring to Fig. 6, a method of controlling an emissions reduction system of the internal combustion engine 10 at the time of vehicle start up will now be described. The method includes the controlling flow of coolant through the dosing module coolant passageway 25 based on a temperature of the coolant within the coolant circuit 90, 190 (step 200). As previously discussed, the exhaust gas afitertreatment system 12 includes the flow control device 96 that automatically controls flow of coolant through the coolant passageway based on a temperature of the coolant within the coolant circuit. The flow control device 96 may be a thermostat such as the thermostatic wax thermostat 98, a bypass device that includes the temperature sensor 100, the coolant bypass passage 104 and the coolant control valve 102 as described above with respect to Fig. 4, or another appropriate flow control device. Regardless of the type of flow control device 96, 196 used, the method includes detecting a temperature of the coolant within the coolant circuit 90, 190 and when the detected temperature is less than a predetermined temperature, the flow control device 96, 196 controls the coolant circuit 90, 190 to prevent a flow of coolant through the dosing module coolant passageway 24.

[0049] In some embodiments, the method may optionally include determining a temperature of the dosing module 24, either indirectly via by modelling based on factors such as engine speed, exhaust gas temperature, ambient temperature and coolant temperature, or alternatively directly via a dosing module temperature sensor 43 (step 202), and then adjusting a flow of coolant through the coolant passageway 25 based on the temperature of the dosing module 24 (step 204).

[0050] Advantageously, the system and method described herein provide sufficient heating of the dosing module 24 including the injector 46 to melt any crystallization therein by addressing the effect of relatively cold coolant within the coolant circuit 90, 190. By addressing the effect of relatively cold coolant within the coolant circuit 90, 190 and thereby permitting sufficient heating of the dosing module injector 46, the immobilizing effects of the crystallization can be easily addressed, and uninterrupted operation of the exhaust gas afitertreatment system may be reliably achieved.

[0051] Selective illustrative embodiments of the system and device are described above in some detail. It should be understood that only structures considered necessary for clarifying the system and device have been described herein. Other conventional structures, and those of ancillary and auxiliary components of the system and device, are assumed to be known and understood by those skilled in the art. Moreover, while a working example of the system and device have been described above, the system and device are not limited to the working examples described above, but various design alterations may be carried out without departing from the system and device as set forth in the claims.