THE TECHNOLOGICAL TREND OF VEHICLE S ELECTROMAGNETIC CONTROL VALVE (ECV)

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 3, March 2018, pp , Article ID: IJMET_09_03_116 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed THE TECHNOLOGICAL TREND OF VEHICLE S ELECTROMAGNETIC CONTROL VALVE (ECV) Geonwoong Baek Department of Mechanical & Automotive Engineering, Kongju National University, Republic of Korea, , Cheonan-daero, Seobuk-gu, Cheonan-si, Chungcheongnam-do Haengmuk Cho Department of Mechanical & Automotive Engineering, Kongju National University, Republic of Korea, , Cheonan-daero, Seobuk-gu, Cheonan-si, Chungcheongnam-do ABSTRACT In accordance with CO 2 emissions and fuel efficiency regulations of each country, external valves of air-conditioner compressor for vehicle affecting exhaust gas and fuel efficiency should be accurately controlled, and understanding on the related function elements of electromagnetic control valve (ECV) as well as technology development should be realized together. Overseas individual institutions and groups, etc. are analyzing force, pressure, and temperature, etc. acting on components of the valves by using related theories and analysis programs for application to practices. In the present article, technological trends of the electromagnetic control valve (ECV) that drives the plunger and controls flow rates by applying electromagnetic forces as a function of inputted electric currents among externally-controlled valve methods for variable swash plate-type compressors are described. Key words: Swash plate compressor, ECV, Cooling capacity, Bellows set, Solenoid. Cite this Article: Geonwoong Baek and Haengmuk Cho, The Technological Trend of Vehicle s Electromagnetic Control Valve (ECV), International Journal of Mechanical Engineering and Technology 9(3), 2018, pp INTRODUCTION Due to the effects of environment pollution and global warming, regulations on vehicles fuel economy and exhaust gas are being increased. In the case of the US, regulations are being enforced to achieve more than 54.5mpg(23.2km per liter) by 2025, while more than a given amount of exhaust gas is specified not to be discharged in Europe. According to the data, diesel vehicles showed a reduction by a maximum of 22.7% in fuel economy as a result of operation of the vehicle s air-conditioner compressor, while gasoline vehicles showed a maximum reduction of 19.5%. In the case of exhaust gas, diesel vehicles had more emission of NOx by about 5%, while gasoline vehicles were found to produce more of THC(NMOG) by 22% and CO by 18% CO [1] editor@iaeme.com

2 The Technological Trend of Vehicle s Electromagnetic Control Valve (ECV) According to the demand for improvement in fuel efficiency and reduction of exhaust gas of vehicles, development of related technology for ECV that controls compression amounts of the variable swashplate-type air-conditioner compressor is required. ECV regulates swash plate of the compressor by controlling pressures of the section according to ECU signals of the vehicle as an electromagnetic-type air pressure control valve, improving performance of the air conditioner compressor. In the present article, a theory for improving performance of the electromagnetic external valve(ecv) of variable compressors for vehicles is described along with experimental results. 2. THE TECHNOLOGY OF ELECTROMAGNETIC CONTROL VALVE (ECV) 2.1. Vehicle s Air Conditioner Compressor Air conditioner compressor for vehicles is being implemented in the direction of increasing the compressor efficiency by variably changing angles of the swash plate as a function of pressures inside the compressor for improvement in fuel economy and power performance while the compressor s swash plate is not of a fixed type. The fixed swash plate-type as shown in Fig.1 (a) produces operability deterioration due to inducement of torque variation resulting from on/off repetition. To prevent this, a variable swash plate-type air-conditioner compressor controlling angles of the swash plate has been developed. For valve methods of the variable swash plate-type compressor, there are mechanical control valve (MCV) and electronic control valve (ECV). In both methods, cooling load is controlled according to suction port pressures of the refrigerant, and valves are operated by using a pressure difference between discharge port and crank port. When the compressor is not driven, the valves are closed by spring load to shut off flow of the refrigerant and prevent transmission of suction pulsation, and while the valve is opened, the pressure difference before and after the check valve is increased upon normal operation of the compressor [2]. The inside swash plate-type is a variable swash plate-type air-conditioner compressor of MCV method, employing a method where slope of the swash plate is varied by mechanical variation due to inside pressure difference, with the inside structure being shown in Fig.1(b). Since the control range of the inside variable swash plate-type is limited, an external variable swash plate-type compressor has been recently developed for application to practice so as to produce optimum efficiencies by mounting of electrically-driven externally- controlled valve (ECV), with its inside structure being shown in Fig.1 (c). As compared with the MCV applied to the inside swash plate-type, the ECV applied to the external swash plate-type allows close control according to running state and power state of the vehicle so that studies on ECV of the external swash plate-type are being actively carried out. Structure of the ECV is composed of cylinder-type valve, solenoid, and bellows. Solenoid plays the role of adjusting valve positions by using electromagnetic forces, driving the plunger and controlling flow rates by producing electromagnetic forces according to the inputted electric current. Bellows involves a key technology of the ECV, as an apparatus that controls flow rates of the valve through opening/closing of the tube by axial tensile and compressive movement with sensing of pressure changes in the compressor crankcase and editor@iaeme.com

3 Geonwoong Baek and Haengmuk Cho prompt expansion and shrinkage motion [3]. In addition, as regulation of valve flow rates is possible, disturbance of other pressures and torques is prevented. Control of ECV determines duty of the ECV by comparing with the target temperature and operating of the air temperature at evaporator outlet as the input signal in the ECV control module. Accordingly, suction pressures can be controlled and power consumption is reduced by changing the swash plate angle of the compressor. For temperature control method, power consumption of the compressor is reduced by comparing the control logic for indoor temperatures and the control logic for duct discharge temperatures and optimally controlling operation amount of the controller under the same required air volume as well as temperaturecontrolling door [4]. (a) Fixed type (b) Internal variable type (c) External variable type Figure 1 A/C compressor type with swash plate [2] 2.2. ECV Control Logic Operation conditions of the ECV are optimally controlled according to operating conditions. By receiving signals from the ECU of P/T (power train), valve operation status is determined by the ECU of the ECV according to acceleration/deceleration criteria. Acceleration/deceleration is determined by entering/clearing in the relationship between TPS of acceleration signals and RPM, while deceleration signals are determined by using car speeds, brake pedal signals and fuel cut signals [4]. Upon vehicle acceleration, ECV duty is reduced upon vehicle acceleration by application of the algorithm based on feedback of discharged air temperature which allows control of editor@iaeme.com

4 The Technological Trend of Vehicle s Electromagnetic Control Valve (ECV) ECV duty according to operation with the target air temperature of evaporator. [3] It operates by limiting the risen temperature of the evaporator and compensating for the discharged air temperature. Driving of ECV is controlled through P/T ECU, while improvements in fuel efficiency by 4% and in power by 2% can be expected according to the control logic for discharged air interlocked with P/T [4] Efficiency Decreasing Factor of Compressor Figure 2 shows the shapes of valve spring and valve rod suction path as ECV components of the compressor ECV. Performance of the compressor is affected by the valve spring and the valve rod face. Performance degradation occurs due to spring load of the check valve and flow on the valve rod face. To find accurate performance degradation, the degradation ratio of cooling capacity should be obtained through the ratio between the compressor s cooling capacity (Q) and the suction capacity. Degradation ratio of cooling capacity is as given by equation (1). ( ) ( ) (1) of the equation (1) shows the cooling capacity [W], the discharge pressure[bar], the suction pressure[bar], the polytrophic index, the volumetric efficiency[%], and gap volume ratio[%]. If loads of the spring as a component for the valve affecting performance is reduced and the valve rod face is changed to a plane to reduce the degradation ratio, there is an improvement effect by 1.9% [2] Motion of Bellows as a function of Mechanical Weight Since bellows affects the ECV performance as the major component for ECV, mechanical rigidity of the bellows needs to be verified to find behavior of the bellows. For verification of the bellows rigidity, a spring constant of the bellows should be obtained. The spring constant of the bellows set is as given by the equation (2). of the equation (2) means the spring constant. When the spring constant is obtained through the equation (2), is derived. When load displacement at this time is measured by application of the effective elastic modulus (545Gpa), the maximum displacement is observed to be 0.9mm, and the load 5.3N as shown in Fig.3 [3] Bellows Movement Depending on Refrigerant Pressure Depending on pressures of the refrigerant entering the suction valve, the bellows as a component of the valve shrinks or expands. To find required movement when the valve is opened and closed, the extent of movement when pressure of the refrigerant is applied should be known. Pressure analysis through the finite element analysis is shown in Fig.4. When the refrigerant pressure is 500kPa, a repulsive force (2.77N) is produced by constraining the axial (2) editor@iaeme.com

5 Geonwoong Baek and Haengmuk Cho deformation. In addition, the amount of deformation varies with presence status of the inside spring, and the amount of deformation is reduced when there is the spring [3]. Figure 2 Assembly of a suction check valve on the rear housing of a compressor [3] Figure 3 Load-displacement curve of bellows [4] Figure 4 Reaction force of bellows by pressure under a fixed constraint [4] editor@iaeme.com

6 The Technological Trend of Vehicle s Electromagnetic Control Valve (ECV) Figure 5 Construction of external control valve [5] 3. EFFICIENCY IMPROVEMENT DESIGN OF ECV 3.1. Improvement Design of ECV Electromagnetic Force Since electromagnetic forces acting on the ECV are the forces that operate the valve, performance of the ECV is enhanced the higher the electromagnetic forces. Electromagnetic of the ECV,, can be given by the equation (3). of the equation (3) is the elastic force of the bellows[n], the elastic force of the plunger spring [N], the projected net area of the bellows[ ], the valve suction pressure [Pa], When the electromagnetic force of the existing valve is calculated from the equation (3), 25N is obtained as given by the equation (4) [5]. According to the equation (3), electromagnetic force of the valve should be designed to be larger than the elastic forces of the bellows and the spring. To further improve the electromagnetic forces, there is a method of reducing energy consumption by minimizing the air gap present within the magnetic field circuit, and design should be carried out so that the magnetic flux flows smoothly by alleviating magnetic flux density at places where the magnetic flux density is locally concentrated in the iron core portion [5] Design of Solenoid As shown in Fig.5, solenoid of the ECV is composed of disk, core housing, coil, plunger, and housing body. If the space within the magnetic circuit of solenoid is minimized, electromagnetic forces of the valve can become stronger to increase the suction force of refrigerant, and performance of the valve can be enhanced by reducing energy consumption if the suction forces are increased. (3) (4) editor@iaeme.com

7 Geonwoong Baek and Haengmuk Cho If the gap between the plunger and the housing as components of the solenoid is reduced and the overall air gap is designed to be constant, then the improvement of the electromagnetic force by 17.8% can be expected [5]. If the depth of the core groove (maximum depth) is reduced and the shape is designed to be circular, then the improvement of the electromagnetic force by 15.2% can be expected. When the thickness of the disk is increased, the improvement of the electromagnetic force by 2.3% [5] can be expected. 4. CONCLUSIONS In the present article, a variable compressor has been described and types of suction control valves used for the variable compressor have been introduced. In the suction control valve, components of ECV (electronic external valve) were described, and a design capable of improving efficiency of the valve summarized. 1. Control logic of the ECV can be precisely controlled by precision analysis of the vehicle s acceleration/deceleration signals and duty control of the valve. 2. Performance of the ECV is determined by the control logic capable of precisely controlling the valve as well as the electromagnetic forces of the solenoid and the bellows constituting the valve. 3. If load displacements of the bellows are precisely measured for improvement of electromagnetic forces, and the bellows along with the solenoid are designed with reduction of air gaps within the circuit, the performance improvement of the ECV can be expected. ACKNOWLEDGEMENT [S , Development of ECV for Automotive Air Con. Compressor] This work was supported by the Technological Innovation R&D Program (No: S ) funded by the Small and Medium Business Administration (SMBA, Korea) REFERENCES [1] Kim SW, Lee MH, Kim KH, Jung CH (2013), A Study about Emission and Fuel Economy of a Passenger Car according to Blower Strength of A/C and Heater", Spring Academic Conference of Korean Society of Automotive Engineers, Vol. 2013, No.5, pp: [2] Lee BS, Lee YJ, Lee TJ, Han JS, Bae IP, Lee GH (2016), A Study on the Optimum Design of the Suction Check Valve used to the Variable Swash Plate Compressor for a Vehicle, Treatise on Academic Conference of Society of Air-conditioning & Refrigerating Engineers of Korea, pp: [3] Son IS, Shin DK, Hwang S (2016), Analysis of the Mechanical Behavior of Bellows for Electromagnetic Control Valve", Korea Academia-Industrial Cooperation Society, Vol.17, No.3, pp: , [4] Lee CW, Kim JW, Jang KL, Jeong GS (2010), Development of Speed Sensitive Air Conditioning System for Fuel Economy and Power Performance, Korean Society of Automotive Engineers, pp: [5] Lee YJ, Lee GH (2010), Design for Improving Magnetic Force for Control Valve in Variable Compressor, Korean Society for Fluid Power & Construction Equipment, Vol.7, No.4, pp: [6] Settapong Malisuwan, Wassana Kaewphanuekrungsi, Noppadol Tiamnara and Pollawich Apintanapong, A Study of Electromagnetic Radiation Effects From Mobile Phone Base editor@iaeme.com

8 The Technological Trend of Vehicle s Electromagnetic Control Valve (ECV) Stations on Human Health. International Journal of Advanced Research in Engineering and Technology, 6 ( 12 ), 2015, pp [7] Bhavikatti, A. M., Dr. Subhash Kulkarni and Arunkumar Lagashetty. Electromagnetic Studies on Nano - Sized Magnesium Ferrite. International Journal of Electronics and Communication Engineering & Technology, 2 (2), 2011, pp [8] Dr. Srinivasa Baba, V. S. S. N., Giri Raju, B. and Mrs. Srivalli Gundala. Electromagnetic Interference (EMI) Analysis for Oblique Incidence of EM Waves in Double Shields. International Journal of Electronics and Communication Engineering & Technology, 6 (11), 2015, pp editor@iaeme.com