Available online at www.sciencedirect.com
ScienceDirect Procedia Engineering 168 (2016) 59 – 62
30th Eurosensors Conference, EUROSENSORS 2016
A PCB based engine air intake sensor – Application to a typical low power engine Dimitrios N. Pagonisa, Anastasios Moschosb, Grigoris Kaltsasb* a
Department of Naval Architecture, TEI of Athens, Athens 12243, Greece b Department of Electronics, TEI of Athens, Athens 12243, Greece
Abstract This work concerns the evaluation of a novel sensor for determining the air intake of a typical low power engine. The sensor is based on PCB technology enabling effective thermal isolation and direct communication to the macroworld. The device was integrated into a DIESEL engine testbed for characterization purposes while a commercially available mass air flow sensor was employed as a reference; the proper functionality of the developed prototype has been validated. Key features of the proposed device are robustness, simplicity and low-cost suggesting numerous potential applications in the automotive area. © by Elsevier Ltd. This is an openLtd. access article under the CC BY-NC-ND license ©2016 2016Published The Authors. Published by Elsevier (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 30th Eurosensors Conference. Peer-review under responsibility of the organizing committee of the 30th Eurosensors Conference Keywords: Flow sensor; PCB sensor; Automotive sensor; Engine tesbed
1. Introduction Mass air flow sensors are widely employed in the automotive industry for measuring the air intake into internal combustion engines in order to adjust the amount of fuel supplied for efficient combustion. During the past decade, microsystem technologies have greatly contributed to reduce the cost of the specific type of sensors; furthermore, the majority of the devices currently employed are thermal flow microsensors [1,2,3] since in order to provide equivalent performance to MEMS sensors by traditional electromechanical/discrete electronics approaches, the cost
* Corresponding author. Tel.: +30-2105385305; fax: +30-2105385304. E-mail address:
[email protected]
1877-7058 © 2016 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 30th Eurosensors Conference
doi:10.1016/j.proeng.2016.11.146
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would have to be increased significantly [4]. In this paper we present a novel PCB technology based engine air intake sensor. The sensor is fabricated utilizing only standard PCB fabrication techniques and commercially available components, eliminating the need for complicated and expensive procedures. 2. Fabrication technology The operation of a fully PCB integrated thermal sensor without the presence of silicon or wire bonding has been demonstrated previously [5,6]; in the specific device, the sensing elements (thermistors) are formed by deposition and patterning of an appropriate Pt layer. We should note that priory to the Pt deposition planarization of the patterned PCB surface (Cu tracks) is performed in order to smooth the existing height variations, since a straightforward metal deposition on the PCB does not lead to a functional structure due to the anomalous topography of the surface [5]; for the specific step, a negative tone photoresist SU-8 is employed. ȉo further simplify the above fabrication process and eliminate the necessity for the planarization step, the following alteration has been performed; after copper patterning on the PCB substrate, appropriate -commercially available, NTC thermistors have been mounted on the corresponding Cu tracks as sensing elements, instead of forming them by Pt deposition and patterning; thus, the resulting fabrication technology has significantly fewer steps, lower cost and increased robustness. The R-T response for the thermistors employed is shown at figure 1a while the final structure of the device is presented at figure 1b.
a
b
Fig. 1. (a) Element resistance as a function of the temperature for the utilized NTC thermistors; (b) The fabricated sensor (12 NTC thermistors have been employed as sensing elements in the particular device)
3. Measurement Setup In order to validate the functionality of the proposed device an initial characterization has been performed on a DIESEL engine testbed. In more detail, the developed sensor was integrated into a typical four cylinder low power industrial engine (IVECO N45 MST with rated power of 125 HP at 2200 rpm) coupled with an eddy current dynamometer (DYNOmite with maximum absorbed power 400 HP at 5000 rpm). The engine air intake was also recorded with a commercially available air flow meter, as a reference. Both, the engine speed and the mechanical load applied by the dynamometer were Fig. 2. The sensor packaging and electrical interface system
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controlled accordingly employing the testbed’s control station (fig. 3b). Note that the engine speed varied from idle (about 900 rpm) to 1600 rpm while the mechanical load applied was zero to moderate (about 20% of the rated for the engine speed employed). The sensor was mounted on an appropriate housing as shown in figure 2, which was connected to the engine’s air intake. In more detail, the device was wall-mounted to a tube with a diameter of 84 mm; which was placed in series with the testbed air flow meter. The complete experimental setup is illustrated in figure 3.
a
b
ŶŐŝŶĞdĞƐƚďĞĚ EĂǀĂůƌĐŚŝƚĞĐƚƵƌĞƉƚ
Fig. 3. (a) The evaluation setup - a:Dynamometer, b:Reference flow sensor, c: Developed sensor; (b) Engine testbed control station
4. Results - Discussion The prototype sensor was evaluated under anemometer principle of operation utilizing both constant current (CC) and constant resistance (CR) modes. The experimental data (i.e. extracted sensor’s signal versus the measured engine air intake) are presented in figure 4; saturation in the sensor’s signal is noticed for flows above 180 Kg/h in CC mode of operation. Furthermore, the sensitivity of the device improves significantly in CR mode of operation, as expected. It should be noted though that the corresponding Reynolds number for the specific flow range / experimental setup is up to 48000 (full turbulent flow region). As a general remark, we can conclude that the functionality of the proposed device has been successfully demonstrated.
Fig. 4. Preliminary evaluation results under the hot-wire principle of operation for constant current and constant resistance mode
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5. Conclusions A novel PCB thermal sensor for the air intake measurement of a typical low power industrial engine was presented. The device is based on a relative simple fabrication technology with low equipment needs which allows direct electrical communication to the macroworld eliminating the need of wire bonding. Furthermore, by employing commercially available thermistors as sensing elements, the fabrication cost is reduced while at the same time the robustness of the device is increased. The sensor was integrated in a typical DIESEL engine for evaluating its functionality; the flow range employed for characterization was 0-190 kg/h under the anemometer operating principle, for constant current (CC) and constant resistance (CR) modes of operation, while a commercially available mass air flow sensor was employed as a reference. The obtained preliminary results confirm the proper functionality of the developed prototype. On-going work focuses on the optimization of the device’s design, the use of calorimetric principle of operation and also on employing a by-pass measuring setup in order to obtain laminar flow conditions for the specific flow range.
References [1] Oleg Sazhin, Novel mass air flow meter for automobile industry based on thermal flow microsensor, Flow Measurement and Instrumentation 30 (2014) 60-65. [2] J. Marek, M. Illing, Microsystems for the automotive industry. Electron Devices Meeting, IEDM '00. Technical Digest International (2000) 3-8. [3] K. Hanzawa, S. Tashiro, H. Hoshika, M. Matsumoto, Developments in Precision Power Train. Hitachi Review 63 (2014) 109-114. [4] William J. Fleming, M, Overview of Automotive Sensors. IEEE Sensors Journal 1 4 (2001) 296-308. [5] G. Kaltsas, A. Petropoulos, K. Tsougeni, D. N. Pagonis, T. Speliotis, E. Gogolides and A. G. Nassiopoulou, “A novel microfabrication technology on organic substrates - Application to a thermal flow sensor”, Journal of Physics: Conf. Ser. ,92 012046 (2007). [6] A. Petropoulosa, D. N. Pagonis, G. Kaltsas, “Flexible PCB-MEMS flow sensor”, Procedia Engineering (2012 ) 47 236 – 239.
