KR20140147745A - Reductant delivery unit for automotive selective catalytic reduction with thermally optimized peak-and-hold actuation based on an injector open event - Google Patents

Abstract

Provided is a trigger circuit for a peak-and-hold driving circuit for a reductant delivery unit (RDU) that is provided with a solenoid actuation injector for a selective catalytic reduction (SCR) post-treatment for vehicles. The peak-and-hold driving circuit is configured and arranged for the injector to be actuated in a rise peak current phase followed by a low-current hold phase. The trigger circuit includes an injector opening detection circuit that is configured and arranged to trigger a transition from an injector rise peak phase to the subsequent hold phase based on a detected injector opening event.

Description

Technical Field [0001] The present invention relates to a reduction agent delivery unit for selective catalytic reduction of an automobile by a thermally optimized peak and hold operation based on an open event of an injector. BACKGROUND OF THE INVENTION 1. Field of the Invention < RTI ID = EVENT}

The present invention relates to a reducing agent delivery unit (RDU) for supplying a reducing agent to an engine exhaust system, and more particularly, to a reduction agent delivery unit (RDU) To a reducing agent delivery unit (RDU) for improving the electrical load.

The advent of stricter emissions legislation in new rounds in Europe and North America has driven the implementation of new exhaust aftertreatment systems, particularly in the lean and ultra-lean conditions Lean burn technology such as ignition (diesel) engines and stratified charge spark ignition engines (typically direct injection). The lean-burn engine shows a high level of nitrogen oxide (NOx) emissions that are difficult to process in the oxygen-enriched exhaust gas environmental characteristics of the lean burn. One such technique involves a catalyst that facilitates the reaction of ammonia (NH ₃ ) and exhaust gas nitrogen oxides (NO x) to produce nitrogen (N ₂ ) and water (H ₂ O). This technique is called Selective Catalytic Reduction (SCR).

Ammonia is difficult to handle in its pure form in automotive environments. Thus, it is customary in these systems to use a liquid aqueous urea solution, typically 32% strength urea solution (CO (NH ₂ ) ₂ ). This solution is called AUS-32 and is also known by its commercial name AdBlue. The urea solution is transferred to a hot exhaust stream and converted to ammonia in the exhaust gas and after conversion to ammonia and isocyanic acid after undergoing thermal decomposition or thermolysis. The isocyanic acid is then hydrolyzed with water present in the exhaust gas and converted to ammonia and carbon dioxide (CO ₂ ). The ammonia resulting from the heat dissipation and hydrolysis then undergoes a catalytic reaction with nitrogen oxides as previously described.

The AUS-32 injector is typically installed directly on the engine exhaust, which exposes the injector to a very hot environment. To reduce the electrical thermal load on the injector, so-called peak-and-hold injector drivers have been introduced. Referring to FIG. 1, the function of such a driver is to provide two modes of describing the injector current, namely a rise-to-peak current phase, followed by a low current hold phase, (Current control at high switching frequency).

The low current level is generally much lower than the fully saturated current level of the injector and is higher than the minimum level of current required to maintain the injector (solenoid) opening. In today's drive circuits, the transition from the rising peak to the hold phase is typically triggered by current level detection on the current, once the current reaches that level, a subsequent hold phase becomes possible. FIG. 2 shows a peak and hold circuit 10 with a conventional peak current detection and trigger circuit 12.

The main advantage of operating the injector with a low current hold face is a low electrical load that results in comparison with operation under saturated switch conditions. For example, an injector with a 12 ohm coil supplied at 14V would consume 16.3 Watts (l = 1.2 A). Injectors operating in 0.5 A hold mode will consume 7 Watts during the hold phase.

Disadvantages arise as the temperature rises and the injector resistance increases. As the resistance increases, the time required for the current to reach the predetermined threshold will increase due to the time correlation to the coil resistance. In a limited case with a sufficiently high temperature, the current may never reach the transition threshold and the injector is still open. The temperature range in which this situation occurs depends on the difference between the selected transition current level and the minimum current required to open the injector. This difference will not be zero considering the tolerances and variations of the various components that make up the electrical and magnetic circuits.

For example, today the peak current is specified at a level of 0.8A. Which is higher than the required nominal open current of 0.6 A. The nominal hold current specified is 0.5 A. For example, if the available electrical supply voltage is only 12 V and the injector coil resistance is 17 OMEGA (for example, the injector coil temperature is 130 C), a situation may arise where the saturated injector current is 0.7 A. An example of a similar current waveform in this case is shown in FIG. Thereafter, the risk of this condition is that it already operates the injector at elevated temperatures subject to increased electrical thermal load.

Therefore, there is a need for a reducing agent delivery unit (RDU) that improves the overall electrical load over a wide temperature range by triggering a transition from peak to hold based on detection of injector opening.

An object of the present invention is to satisfy the above-mentioned requirements. According to the principles of the present invention, this object is achieved by a trigger circuit for the peak and hold drive circuit of a reductant delivery unit (RDU) equipped with a solenoid operated injector for selective catalytic reduction (SCR) post-treatment of vehicles. The peak and hold drive circuit is configured and arranged to operate the injector at a rising peak current phase followed by a low current hold phase. The trigger circuit includes an injector opening detection circuit configured and arranged to trigger a transition from a rising peak face of the injector to a subsequent hold phase based on a detected open event of the injector.

According to another aspect of the embodiment, the reducing agent delivery unit (RDU) and the control unit for selective catalytic reduction (SCR) post-treatment of the vehicle include a reducing agent delivery unit (RDU) with a solenoid operated injector. The control unit is electrically connected to the solenoid. The control unit is equipped with a peak and hold drive circuit that is configured and arranged to operate the injector at a rising peak current phase followed by a low current hold phase. The drive circuit includes an injector opening detection circuit configured and arranged to trigger a transition from a rising peak face of the injector to a subsequent hold phase based on a detected open event of the injector.

According to another aspect of an embodiment, a method of triggering a reducing agent delivery unit (RDU) with a solenoid actuated injector for selective catalytic reduction (SCR) post-treatment of a vehicle includes detecting and detecting an open event of the injector , Triggering the transition from the rising peak face of the injector to the subsequent hold face to limit the heat load on the injector to the minimum value necessary to ensure the opening of the injector.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features, and features of the present invention, as well as methods of operation and functions of related components of the structure, as well as combinations of components and economies of manufacture, are set forth in the following detailed description and attached drawings Will be more apparent in light of the claims, all of which form a part hereof.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be better understood from the following detailed description of preferred embodiments of the invention taken in conjunction with the accompanying drawings, in which like reference numerals refer to like parts.
Figure 1 is a plot of a conventional injector current showing a rising peak face followed by a low current hold phase.
2 is a block diagram of a conventional peak and hold circuit with a peak current detection and trigger circuit.
Figure 3 is a plot of a conventional current waveform showing saturation current at 0.7 A;
4 shows a conventional injector open event detection by current analysis.
Figure 5 shows the detection of the open time from the second derivative of the coil current.
6 is a block diagram of a peak and hold circuit with an injector opening detection circuit provided in accordance with one embodiment.
Figure 7 shows the current waveform resulting from the circuit of Figure 6;
8 is a diagram of a control circuit including the circuits of Fig. 6 for operating a reductant delivery unit (RDU).

The disclosed embodiment relates to a control strategy for eliminating the risk of an undesirable increase in the heat load of the injector of the reducing agent delivery unit (RDU) at an already elevated operating temperature. Detection of injector opening and closing events by analysis of voltage or current is well known. An example of open event detection by current analysis is shown in FIG. 4 (labeled "OPP2") where the accelerometer signal is referenced 14, the voltage signal is 16, (18), and the current signal is indicated by reference numeral (20).

The detection of these events is useful for diagnostic purposes and can also be used to compensate for lifetime shifts in flow due to changes during the injector transient phase. Referring to FIG. 5, one embodiment of this detection is in the form of a hardware with circuitry that generates an electrical pulse 22 upon an open detection using a second derivative 24 of the current waveform as an input value. The spurious initial pulse 26 can be ignored by suitably using an enable window that allows only pulses over any predetermined time during, for example, the injector pulse-width. One example of using a second derivative of the current detecting injector state is disclosed in the present application, entitled " Solenoid-Actuator-Armature End-of-Motion Detection "Quot; US Provisional Application " (Attorney Docket Number: 2012P02238US), filed concurrently herewith, the contents of which are incorporated herein by reference.

Referring to FIG. 6, there is shown a block diagram of a peak and hold drive circuit 10 'constructed and arranged to actuate the injector at a rising peak current phase followed by a low current hold phase, according to one embodiment. The circuit 10 'includes a trigger circuit 28 with an injector opening detection circuit 29. Thus, the trigger circuit 28 replaces the current threshold trigger circuit 12 of the prior art of FIG. This circuit 10, when detected, for example, using the second derivative 24 of the above-mentioned current waveform, is used to trigger the transition from the rising peak face of the injector actuation control to the subsequent hold phase Use an open event. In this embodiment, the detection circuit 29 includes a processing or differential circuit 31 for a differential current. Instead of using the second derivative of the current, another conventional method of detecting the open state of the actuator or injector may be used. An example of the current waveform 30 resulting from the execution of this embodiment is shown in Fig.

8, a circuit 10 'including a trigger circuit 28 is connected to a control unit 32 electrically connected to a solenoid operated injector 34 of a reducing agent delivery unit (RDU) As shown in Fig. Reducing agent delivery unit (RDU) 36 may be used in systems of the type disclosed in U.S. Patent Application Publication No. 2008/0236147 A1, the contents of which are incorporated herein by reference.

The reducing agent delivery unit (RDU) 36 includes a solenoid fluid injector 34 that provides a metering function of the fluid and provides a spray jet of fluid into the exhaust flow path of the vehicle for dosing application . Fluid injector 34 is preferably a gasoline, electrically actuated solenoid (coil) fuel injector, such as the type disclosed in U.S. Patent No. 6,685,112, the contents of which are incorporated herein by reference. Accordingly, when the coil of the injector 34 is energized, the valve in the injector is opened, allowing the reducing agent to be transferred to the exhaust gas flow path in a conventional manner.

By using the injector open event as a trigger, the heat load of the injector is limited to the minimum value necessary to ensure the opening of the injector. The risk of the rising peak face being lengthened and thus additional heat load is also prevented.

The foregoing preferred embodiments are illustrated and described for purposes of illustrating methods of using the preferred embodiments as well as illustrating the structural and functional principles of the invention, which embodiments may be modified without departing from such principles. Therefore, the present invention includes all modifications that fall within the scope of the following claims.

Claims (11)

A trigger circuit for a peak and hold drive circuit of a reductant delivery unit (RDU) with a solenoid operated injector for selective catalytic reduction (SCR) post-treatment of vehicles, said peak and hold drive circuit comprising a rising peak Wherein the trigger circuit is configured and arranged to actuate the injector at a current phase,
And an injector opening detection circuit configured and arranged to trigger a transition from a rising peak face of the injector to a subsequent hold face based on a detected open event of the injector.
Trigger circuit.
The method according to claim 1,
Wherein the driving circuit is combined with the driving circuit so as to include the trigger circuit,
Trigger circuit.
3. The method of claim 2,
Further comprising a reducing agent delivery unit (RDU)
Trigger circuit.
The method of claim 3,
Wherein said drive circuit and said trigger circuit are part of a control unit electrically connected to said reductant delivery unit (RDU)
Trigger circuit.
The method according to claim 1,
Wherein the open detection circuit is configured and arranged to trigger the transition based on an electrical pulse generated when detecting an open event of the injector using a second derivative of the current waveform as an input value,
Trigger circuit.
6. The method of claim 5,
Wherein the open detection circuit comprises a differentiating circuit.
Trigger circuit.
A reducing agent delivery unit (RDU) and control unit for selective catalytic reduction (SCR) post-treatment of vehicles,
A reducing agent delivery unit (RDU) with a solenoid operated injector, and
A control unit electrically connected to the injector, the control unit comprising a peak and hold drive circuit configured and arranged to operate the injector at a rising peak current phase followed by a low current hold phase, And a control unit comprising a injector opening detection circuit configured and arranged to trigger a transition from the rising peak face of the injector to a subsequent hold face based on the detected open event.
Reducing agent delivery unit (RDU) and control unit.
8. The method of claim 7,
Wherein the injector opening detection circuit is configured and arranged to trigger the transition based on an electric pulse generated when detecting an open event of the injector using a second derivative of the current waveform as an input value,
Reducing agent delivery unit (RDU) and control unit.
9. The method of claim 8,
Wherein the injector opening detection circuit includes a differential circuit,
Reducing agent delivery unit (RDU) and control unit.
CLAIMS What is claimed is: 1. A method for triggering a reducing agent delivery unit (RDU) with a solenoid operated injector for selective catalytic reduction (SCR)
Detecting an open event of the injector;
And triggering a transition from a rising peak face of the injector to a subsequent hold face based on the detecting step to limit the heat load on the injector to a minimum value necessary to ensure opening of the injector.
Way.
11. The method of claim 10,
Wherein the detecting step uses a second derivative of the current waveform of the injector,
Way.

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