Kolbenschmidt Pierburg Group

Transcription

1 Kolbenschmidt Pierburg Group Mechatronic Exhaust Gas Recirculation Valve for Commercial Diesel Applications A System Module to Optimize Emission Characteristics

2 Complying With the Upcoming Exhaust Gas Legislation by Means of Electronically Controlled Exhaust Gas Recirculation Valves for Commercial Diesel Applications The evermore stringent global emission control legislation governing IC engine-driven vehicles calls for further measures designed to curb raw exhaust gas emissions, specifically for commercial diesel vehicles, in order to ensure efficient and sustainable compliance with emission threshold values. Figs. 1 and 2 illustrate the development of the European particulate matter and nitrogen oxide limit levels which approximately converge with the future US standards. External exhaust gas recirculation has become indispensable as a highly efficient instrument for reducing the engines NOx emissions. Similar to the requirement profile for diesel-engine driven passenger cars, in the future, the continuous and accurate addition of exhaust gas recirculation with simultaneous high system dynamics will be required for commercial diesel applications as well. It has been demonstrated that for meeting the emission requirements under EPA10, Euro 6 and Tier 4 final, for example, an electrically driven exhaust gas recirculation valve is the only solution to comply with this demand. To this end, Pierburg has developed a product family of electronically controlled recirculation systems for diesel engines with swept volumes ranging from 4 to 16 liters. PM (g/kwh) EU-Stage-4 USA Tier 4 EU Stage-3A (2008) US Tier-3 (2008) EU-Stage-3B Fig. 1: Limit emission values: off-road engines EU Stage-2 (2001) US Tier-2 (2001) P > 74 kw USA Tier interim NOx (g/kwh) 0.15 EU emission standards for heavy duty engines Euro II 1998 Product Benefits at a Glance Easy controllability and accurate metering of even minute EGR rates to meet all requirements of Euro 6, Tier 4 final and EPA 10 applications Modular system for various applications in the on-road and off-road sectors and for marine engines Scope of supply: ready-to-install system composed of valve and actuator, which are precisely tuned, both thermodynamically and electrically Single-flow and double-flow designs available (Figs. 3, 4) May be installed in any position Adaptability to various installation situations by separating valve assemblies and applying separate actuators Actuators with supply voltage ratings from V, activation through CAN bus or PWM signals, no hydraulics or pneumatics required Installable even under critical thermal boundary conditions thanks to integrated water cooling PM (g/kwh) 0.1 Euro III US 2010 Euro V Euro IV 0.01 Euro VI NOx (g/kwh) Fig. 2: Limit emission values: on-road engines Low pressure drop, minimum external leakage and short actuating times Service life > 20,000 h or > 20 million cycles; all relevant validations, cf. Table 1 2

3 The Modular EGR Valve System for Commercial Diesel Engines Various actuators and valve groups can be combined with each other as independent system modules and thus take into account the diverse demands made on exhaust gas recirculation rates. The system module varieties developed by Pierburg are based on the use of common parts for actuators and valve bodies in order to keep the total number of individual parts at a minimum. By way of example, Fig. 5 illustrates the subdivision into heavy-duty and medium-duty valves. Single-flow and double-flow valve types with different control valve diameters are available encompassing an engine range from 100 to 600 kw or 4 to 16 liters swept volume (Fig. 6). Fig. 3: Single-flow EGR valve For engine sizes exceeding this range, larger actuator designs are available. Alternative Applications for the Actuator As a separate component, the actuator is also suitable for other applications in heavy-duty and medium-duty diesel engines. On one hand, it lends itself as a drive of the wastegate valve in single- and two-stage charging systems, and on the other, the actuator may be employed for operating an exhaust gas valve downstream of the exhaust gas turbine (Fig. 7). Fig. 4: Double-flow EGR valve Fig. 5: Modular system for EGR valves 3

4 Further applications with similar demands on torque, setting speed and ambient conditions are also feasible, subject to adapted design of the push rod geometry (four-bar link). EGR system Characteristic Unit Specification Value Electric operation allows a simplified application and contrary to other auxiliary energies (e.g. compressed air or hydraulics) it does not require additional sensors with elaborate control. Hence the technology may be utilized in different vehicle segments and applications, whether on-road, off-road or for marine uses. Design and Function The Pierburg EGR valve is composed of an actuator and a valve body, which are connected to each other by a coupling rod (Fig. 5). In principle, the electrical actuator and the valve body are autonomous modules so that the most varied installation situations can be realized by means of a modular system (cf. Fig. 5). In addition, this concept favors the thermal isolation between valve body and actuator, which is imperative, because of the high exhaust gas temperatures and installation in a hot environment. The parallel arrangement of valve axis and actuator axis is an advantageous solution which can be adapted to the installation space available in the engine compartment. Pressure drop at max. EGR rate mbar < 30 Internal leakage throttle flap max. EGR < 2 % Temperature in valve area C 800 Failsafe position close Durability h 20,000 Opening time t 90 ms < 150 Closing time t 90 ms < 100 Position feedback yes Supply voltage V 12/24 Control accuracy max. EGR < 0.2 % Communication ECU CAN & PWM Tab. 1: Minimum requirement The coupling rod serves as a transmission element for the torques between actuator and valve assembly. By adjusting the active lever arms appropriately, the transmission function of input and output is optimized for the application concerned. Focal requirements are proper control behavior and the efficient exploitation of the actuator torque in relation to the backout torque and the breakaway torque. The high thermal, mechanical and chemical stresses prevailing in hot applications call for the use of materials that are resistant to high temperatures and corrosion. Besides this, functional aspects such as low flow losses and good controllability, especially in the case of low EGR rates, are indispensable prerequisites for the acceptance of the system. Fig. 6: EGR valve in installed condition 4

5 Actuator Exacting requirements in relation to service life and operational reliability for commercial diesel engines make noncontact and brushless electrical drives an inevitable necessity in order to ensure that they withstand more than 20,000 operating hours. the EGR cooler. In this case, the actuator does not need an additional mounting. Provided that the installation space offers sufficient air cooling, a water connection is not required. The heat shield covers the entire actuator including the plug area, and is adjusted as a function of the installation and plug position. A two-step stationary planetary gear is built in to guarantee a high torque transmission in line with the order of magnitude required for the envisioned application. This gear design has been service-proven in millions of series-produced components and allows high gear reduction rates at low external loads and high efficiencies, while needing little installation space. By way of example, figure 8 shows an actuator with gear as a sectional model. On the gear side, a space-saving non-contact sensor is integrated for detecting the angular position of the output shaft. Thanks to this patented arrangement, any backlash in the gear is eliminated and a high degree of setting accuracy of up to 0.1 degrees is achieved. Optionally, a return spring may be arranged coaxially to the stationary planetary gear which makes it possible for the actuator to be set to a failsafe position. This allows the electrical actuator to be used as an autonomous drive unit including failsafe function also to be used for other applications in the engine compartment, such as an exhaust gas throttle, brake valve or VNT actuator. Fig. 7: Actuator as exhaust gas valve drive The necessary control electronics are an integral part of the actuator, representing, at the same time, the electrical and logical interface with the control unit of the diesel engine. As a set-point input for internal position control, it accepts CAN data or a pulse width modulated voltage signal (PWM) and provides status feedback via CAN. The actuator and electronic system are designed for voltage supply from 12 V to 24 V so that region-specific requirements are allowed for. Electronicecontrol EC motor Gear Optionally, the actuator may be connected to a coolant circuit in order to preclude thermal overload of the electronic components, even under unfavorable operating conditions. Depending on its application, the actuator can be fastened to the respective component by means of a purpose-designed mounting. Fig. 6 shows an example of how to directly fasten the body of the EGR valve to the intake or incidence side of Fig 8: Sectional view of actuator 5

6 EGR Control Valve Following the analysis of various valve designs, not least with a view to minimizing the actuating energy required, a pressure-equalized control valve was chosen. The control behavior of the exhaust gas valve (Fig. 9) at small aperture angles was improved in favor of small-rate control with the aid of flow simulations and test series. Electrical Interface Plug & Play Repeat of above paragraph By using the same actuator type, the interface with the control unit of the diesel engine is identical for all applications. The supply voltage is 12 V to 24 V DC under the boundary conditions of the usual standards of industrial diesel engine applications (on-road, off-road, marine). For communication with the electronic control unit (ECU) of the engine, a CAN bus or else a PWM interface will be available. As a standard, the EGR system is equipped with a 5-pole standard plug (Bosch- Compact) complying with the usual demands on heavy-duty plug connections. Customer-specific connections may also be realized without problem. Fig. 10: Trial on engine test bench Qualification, Validation, Series Production The components were subjected to all tests and trials that are customary for commercial diesel engines. These included in particular: lifetime test, connection test, vibration endurance test, etc. (Fig. 10). Several embodiment options of the valves described will be launched in series production in 2011 and Mass flow (kg/h) Flow characteristic (throttle dia. 42) p = 30 mbar (closed) (open) Control variable % (PWM) Fig. 9: Valve characteristic Achieving Targets Systematically Business Unit Commercial Diesel Systems In the ongoing endeavor to pay tribute to customer requirements, Pierburg has pooled the relevant activities into the Commercial Diesel Systems Business Unit. The comprehensive expertise in the area of air and exhaust gas management was combined with proven air supply products such as intake manifolds, charge air distributors and throttles, as well as pollutant reduction units like exhaust gas recirculation valves, exhaust gas coolers, exhaust gas valves, exhaust gas mass flow sensors and secondary air systems. Today, these individual elements are successfully deployed in combustion engines as components and, by combining several individual products, as modules. Pierburg possesses the competence to act as your partner in engine development in facing the challenges of present and future emission limits. 6

7 In order to be able to warrant low development costs and high development quality, it is essential to have the right understanding of the interaction between the individual components and their impact on the processes taking place inside the engine. With its fine-tuned charging system components Pierburg is supports the engine manufacturer in this demanding optimization process. Pierburg is a Global Player Long before the buzzword globalization became a dictum, it was vital for the automotive and OEM supplier industries to cross borders and establish a worldwide network of production sites. Pierburg, too, has understood and taken this trend into consideration early on. Besides the German plants in Neuss, Nettetal and Berlin, the company possesses production locations in all important automotive markets of the world. These include production plants and sales establishments in France, the United Kingdom, Spain, Italy and the Czech Republic as well as North and South America, India, and China. As an innovation and technology driving system partner of the OEM, Pierburg is always close to its customers with its world-wide location concept. Moreover, the plants specialization and internal production network yield scale effects and synergies, enhanced efficiency and optimized flexibility Further locations in low-cost regions offer customers competitive products without trade-off in quality. For example, Pierburg has been established in China since The plant in Shanghai primarily caters to the Chinese market, being additionally active as a parts supplier within the Pierburg group. A similar strategy is pursued by Pierburg at the location Ústí nad Labem, Czech Republic, for the European market. Pierburg possesses a worldwide network with team spirit. Exhaust Control Valve EGR Valve EU VI EPA 10/13 Tier 4 Tier 4f EGR Mass Sensor Actuators System Development and Manufacturing EGR Cooler Turbo Charger Intake Throttle Reed Valve Fig. 11: Pierburg System supplier 7

8 Pierburg GmbH Alfred-Pierburg-Straße Neuss GERMANY Tel Fax Subject to alterations. Printed in Germany. A IX j