The Research and Development and Industrialization on Inversely Proportional Solenoid Valve of Electric Hydraulic Control Automatic Transmission Rangli Wu Shaanxi Defence Vocational and Technical College, Xi'an, Shaanxi, China Abstract The objective of the paper is to study the dynamic and static characteristics of proportional solenoid valve by using the mathematical principle to establish the corresponding research system model. The paper describes the generation and development of continuously variable transmission (CVT), establishes mathematical analysis models of its electric field and magnetic field, and uses the software Maxwell of Ansoft to simulate its static characteristics. The results analyze the simulation data of static characteristics of proportional solenoid valve, and finds that the working stroke range of the proportional solenoid valve is determined by the characteristics between the force and displacement and remain approximately horizontal. The characteristics of the proportional solenoid valve in a CVT are mainly determined by the characteristics of the proportional solenoid, so the length of its working section is related to the type of proportional solenoid. Keywords - proportional solenoid valve; CVT; static characteristics; proportional solenoid I. INTRODUCTION A. Development of Continuously Variable Transmission In 1914, German Benz Corp produced first automatic transmission, but it is not the modern electro-hydraulic control of the transmission, it is a belt transmission of the mechanical type continuously variable transmission. In 1926, Buick car will be the first hydraulic coupling and manual transmission together, produced the first generation of hydraulic transmission, but also need to step on the clutch to interrupt power transmission. Automatic transmission in 1940 America Oldsmobile motors were mounted on the first modern significance. This is a liquid controlled transmission of a tandem planetary gear mechanism, and in 1950s in the United States, the 3 largest auto companies began mass production. From 1992 to 1994, the rapid development of electronic controlled transmission[1]. Solenoid valve in particular, the number of solenoid valve to increase the number of, makes the shift solenoid valve has been completely abolished the throttle valve and hydraulic pressure on the D position of the rise and fall control. Double lock solenoid valve is to change the torque converter lock condition control more accurate. The main hydraulic solenoid valve pressure regulator valve could alleviate the burden of work. Clutch solenoid valve, at the time of the solenoid valve, solenoid valve, solenoid valve, torque converter solenoid valve, torque buffer solenoid valve, forced to drop the solenoid valve and the speed of the pulse generator, such as a large number of emerging, the electronic control system for the transmission control surface to further expand. CVT made a landmark breakthrough in the last century 60's. At that time, the researchers at VDT company in Holland began to investigate and study, the aim is to develop a more compact and simple CVT, to match the engine with a larger horsepower. They developed a metal V- type belt type continuously variable transmission called "pushing-block-v-belt", it has a higher transmission power, efficiency index value, and even better than the automatic transmission at that time. after that, CVT has made considerable progress, TOYOTA, Ford, Nissan and other major automotive plants in the world adopted[2], as shown in Figure 1 (a) - (B). (a) Continuously variable transmission in the dongfeng vehicle of japan (b) The CVT car in the subaru brand Fig. 1 Continuously Variable Transmission in Car DOI 10.5013/IJSSST.a.16.3B.07 7.1 ISSN: 1473-804x online, 1473-8031 print
B. Proportional Solenoid Valve Valve is used to control the flow direction of the fluid flow in the system or to adjust the pressure and flow, it is an important control component in hydraulic and pneumatic systems. Valve according to the method of classification, can be divided into manual, motor, electromagnetic type. Solenoid valve is the use of electromagnetic force to promote the valve core action to achieve the flow of fluid, off or change the flow of the solenoid valve operation is convenient, flexible layout, to achieve automatic operation of the action, is the mechanical and electrical integration in the mechanical and electrical parts of the. The electrical signal is converted into an air pressure or hydraulic signal, the interface function of the control air cylinder, hydraulic cylinder, etc.. Solenoid valve is also a major branch of the actuator in automatic instrument. Solenoid valve is the use of the electromagnetic force generated by the circuit switch to open and close or displacement control, its structure is simple, the price is low, the power source is easy, the speed is also faster. Solenoid valve by driving mode, can be divided into linear and rotary type[3]. In rotary solenoid valve, because it is still necessary to convert the rotary motion into linear motion, which increases the mechanical loss, the time delay of the operation. For example, in a digital flow valve driven by a step motor, a pulse sequence is required for the computer, after driving power supply, the stepper motor, each pulse of the stepper motor rotate a fixed step angle along a given direction, and then, by means of a cam or thread, the rotary angle is converted into a displacement, driven by the valve core to move a certain distance. Compared with the rotary solenoid valve, the structure of linear solenoid valve is simple, control and application are more convenient, so it gets more attention. Therefore, as an electromagnetic valve actuator of linear motor has become the object of this paper[4]. II. MATERIALS AND METHODS A. Stepless Transmission System Dynamics Model The model of the vehicle power transmission system is shown in Figure 2.5. The driving force is transmitted from the engine through the clutch to the CVT active belt wheel, through the transmission of the continuously variable transmission mechanism to the passive belt pulley, the differential and the drive shaft are driven to the wheel. The model of the engine and the metal belt continuously variable transmission system and the analysis of its characteristics are established, it is an important basis for studying the matching strategy and control law of continuously variable transmission system. In the process of modeling, we are interested in the parts of the engine, the continuously variable transmission, the transmission system, the wheels and the vehicle dynamics model. In the process of modeling, the clutch is assumed to be combined or the torque converter has been locked[5], the engine speed and the CVT of the active belt wheel speed is the same. Fig. 2 Simplified Model of Automobile Power Transmission System The angular acceleration of the engine is: Ie e Te Tin (1) CVT output shaft angular acceleration: I T T i i (2) s s out I 0 cvt T out T i (3) in cvt icvt e s (4) dicvt e s icvt s (5) dt Where Te is the engine output torque with the unit of N.m; Tin is a CVT driver driving pulley input torque; Out CVT is the T output torque with the unit of N.m; TI is the equivalent drag torque on the wheel with the unit of N.m; Ie is an equivalent moment of inertia of the flywheel and the active pulley in the CVT input shaft, kg.m2; Is is a passive belt wheel and the main reducer in the CVT on the passive axis of the equivalent moment of inertia, kg.m2; Icvt is the belt transmission ratio; I0 is the ratio of the main reducer; e is engine speed with the unit of rad/s; S is the passive belt wheel rotation speed with the unit of rad/s; As the metal belt transmission efficiency; The dynamic equations of the continuously variable transmission system are obtained: TI Ti e cvt dicvt eie i0icvt s (6) dt 2 Is 2 Is Ii Ii e cvt e cvt From the above analysis can be seen, the ratio change rate of the continuously variable transmission system has a decisive influence on the dynamic response of the vehicle, and the dynamic matching of CVT between the engine output power and the driving force of the vehicle is determined. And the ratio change rate is determined by the hydraulic control system, which is the need to control the parameters, therefore, it is necessary to analyze the hydraulic control system in order to obtain the control method of the ratio change rate[6]. DOI 10.5013/IJSSST.a.16.3B.07 7.2 ISSN: 1473-804x online, 1473-8031 print
B. Study on the Improvement of the Static Characteristics of Electromagnet The static characteristics of the electromagnet mainly study the characteristics of linear and hysteretic behavior. Linear characteristics study: linear is the proportion of the valve curve and line to meet the degree, generally expressed in a linear working range of 5%, that is, in the scope of this work, working curve with a straight line instead of the error is not more than 5%. The working range of the electromagnet is determined by the intersection of the spring characteristic curve and the suction line, only when the slope of the spring characteristic curve is higher than the suction line, or the spring stiffness is greater than the suction stiffness, is a stable working point. Proportional valve is linear, which is determined by the distribution of these operating points[7]. After summarizing the research, the factors that affect the linear: (1)The suction characteristics and electromagnet have a great influence on the suction characteristics. From the linear point of view, the suction characteristic curve of the electromagnet is close to that of the uniform distribution, but the horizontal suction characteristic is actually at the expense of the suction. (2)The magnetic permeability of the nonlinear ferromagnetic material and the magnetization curve of ferromagnetic material has an extreme value, which causes the magnetic permeability of the proportional valve to be saturated when the rated current is close to the rated current. (3)Spring stiffness of the linear favorable spring stiffness of the working point across the suction characteristics of the curve is relatively narrow, avoiding the curve of the bending part. Therefore, in the proportion of the pressure valve each with a hard spring. (4)The initial air gap is larger for the linear favorable. (5)The diameter should be appropriate if the armature diameter is too large or too large electromagnet, the spring rigidity is relatively soft, and the working point falls in the bending part of the suction characteristic, unless the initial air gap is large, the linearity is not good, and the essence is the matching problem of the scheme design. Study on the influencing factors of hysteretic phenomena: The main factors that affect the size of the hysteresis are the magnetic hysteresis and the mechanical friction of the ferromagnetic material. In order to reduce the magnetic hysteresis of ferromagnetic materials, soft magnetic material is used for the selection of soft magnetic material and the corresponding heat treatment process can be used to achieve the magnetic properties of the soft magnetic materials, such as the increase of the initial permeability and decrease the coercive force. On the mechanical friction, through the measurement of the electromagnet, there is a large friction, that there is a radial imbalance force. In order to reduce friction, from the angle of the friction coefficient of the reduced path to the unbalanced force and reduce the bearing[8]. The former, the magnet in the structure to ensure that the working air gap and the non working air gap of the concentric requirements, parts to have a certain stiffness. And the non working air gap is not too small, because the air gap is too small, the influence of the eccentricity is greater. The latter, the best use of linear bearings to achieve with rolling friction instead of sliding friction. Have the use of graphite bearing, but a little bump shaft surface will increase hysteresis. Bronze sheet armature hanging, completely eliminating the friction. Proportional valve solenoid generally use the DC power supply, to reduce the hysteresis, in the power supply of the DC signal to retain a certain amount of pulse, that is, "the flutter signal", the static friction of the bearing is changed to dynamic friction. This does not complicate the power supply, instead, it becomes more simple, as long as the rectification process is reduced by filtering requirements, and even completely cancel the filter, so that the power to keep a certain frequency of the pulse component[9]. C. Improvement of Dynamic Characteristics Electromagnet Analysis and research of proportional solenoid, can understand the driving voltage, the initial air gap, the return spring preload and the electromagnetic valve movement quality of the solenoid valve dynamic response characteristics of the impact, increasing the driving voltage, can significantly shorten the time of the solenoid valve closing time to shorten the initial gap, not only to shorten the time of solenoid valve closed, and can reduce the electromagnet drive current spring preload is the resistance of the solenoid valve open, also the power to shut off the solenoid valve should be considered in addition to the compromise, the dynamic characteristics of electromagnet are influenced by many factors, in addition to the coil inductance, the inertia of the moving part, the magnetic induction is lagging behind the magnetic field, so in dynamic analysis, in consideration of the influence of the relaxation phenomenon caused by the hysteresis phenomenon on the dynamic holding of the electromagnet[10]. Once upon a time, the study of the dynamic characteristics of the electromagnet is mainly about the influence of the eddy current on the coil current. In fact, due to the hysteresis effect of magnetic induction, the magnetic induction field is established by the magnetic field. After eliminating the current delay, the influence of the factor on the dynamic characteristics of the electromagnet is obvious. For the use of ordinary ferromagnetic materials for the magnet of the proportion of the electromagnet, the impact will not be ignored. This lag time is generally 10-5~10-2 second. This performance in the role of the solenoid by step electrical signal, the output force for a period of time delay, this delay in addition to the influence of the current signal delay, mainly due to the phenomenon of the ferromagnetic material itself. The cause of this phenomenon is a lot of reasons, which is mainly the influence of eddy current and magnetic hysteresis. For step signal, the influence of the hysteresis is more obvious, because basically can do to eliminate the influence of current delay[11]. D. Proportional Solenoid Valve Mathematical Model Neglecting the influence of the magnetic field effect of the soft magnetic material on the magnetic resistance and the DOI 10.5013/IJSSST.a.16.3B.07 7.3 ISSN: 1473-804x online, 1473-8031 print
influence of the electric eddy current, and the influence of the temperature is not considered. In the process of establishing the system model, the following hypothesis: assuming that the supply pressure is constant, assuming that the outlet pressure is zero; the fluid analysis is considered to be in line with Newton theory; The spring and the valve core are all concentrated in an inertia parameter; the spring characteristic is linear. The proportional solenoid valve is further subdivided into four parts: Electric field, magnetic field, mechanical and hydraulic fluid, the four parts are interrelated[12]. Figure 3 expresses the signal coupling relationship between each part. When the control signal is given, in the electric field, the signal is amplified and the output current is I to the magnetic field, the change of magnetic field Phi affects the output current of the electric field; Magnetic field output Φ electromagnetic force FmR to mechanical part, at the same time, the displacement of the valve core x, speed will have an impact on the magnetic field characteristics; Fluid portion of the fluid force FpR acting on the spool, at the same time, the displacement of the valve core, the speed of the fluid will be part of the impact. Therefore, for a comprehensive analysis of the characteristics of the solenoid valve, analysis of the method of coupling analysis is needed[13]. Figure 3. Internal signal coupling diagram of proportional solenoid valve In the case of the ideal case, the voltage balance equation of the solenoid valve coil is: d U Ri (7) dt U is the coil drive voltage in the form of I; is the coil drive current; the R is the coil resistance; it is the flux linkage. The magnetic flux linkage and the air gap in the current and magnetic circuit of the windings are expressed as a Formula (7): di ( xa, i) dxa U Ri Le (8) t dt i dt Le is induction coefficient; xa is magnetic circuit air gap length in Formula (8), the right side of the first item is the resistance drop, and the second is the induced electromotive force caused by the current change, third as the electromotive force of spool displacement caused by. It can be seen from the magnetic flux linkage, the coupling between the valve core displacement and the coil current. Magnetic field: neglecting displacement current and hysteresis effect, the magnetic field vector potential function equation can be derived from the basic equation of Maxwell: A 1 A J (9) t 0 In the formula, is the electrical conductivity; A is the magnetic potential vector; is the relative permeability; 0 is the vacuum permeability; J is the source of the current density, is differential operator. Current density value of I(t) for N turn coil: NI() t J0 (10) Ac Ac is the cross section area of the coil. Electromagnetic force calculation formula is as follows: W( x, I) Fm (11) x W is the magnetic field energy. III. RESULTS AND ANALYSE A. Geometric Modeling Analysis of Proportional Electromagnet Maxwell of Ansoft is a very good electromagnetic analysis software. It is in the finite element mesh to adapt to the originality of the technology, provide a strong support for the design engineers to design creative design. Maxwell2D/3D is an important part of the design and solution of Ansoft mechanical and electrical system. Maxwell2D is a powerful and accurate result, easy to use two-dimensional electromagnetic field finite element analysis software. The static characteristics of the proportional solenoid are calculated by Magnetostatic solver Maxwell2D. In Maxwell2d X-Y coordinate system according to the actual size Kaidi electromagnet company production of GV-45-4-BT proportional solenoid can the proportional solenoid was established. Figure 4 shows the model of the proportional electromagnet built in the X-Y coordinate system in the Maxwell2D. Boundary condition is the key to solve the problem of electromagnetic field, the simulation model involves two kinds of boundary conditions are Neumann boundary conditions and Dirichlet boundary conditions. Neumann boundary conditions are often referred to as second kinds of boundary conditions, It defines the law of boundary potential and the distribution of derivative. Maxwell mentioned that the Qicinuo Iman boundary, namely, the wizard is zero. Neumann boundary conditions for the simulation of magnetic wall, to prevent any lines across the border. If the boundary is sufficiently far from all current sources, the H field is small at the boundary, the Neumann boundary conditions have little effect on the whole field; Often called the Dirichlet boundary conditions for the first boundary condition, finite element computing, it is often called the constrained boundary conditions, or the essential boundary conditions. It defines the distribution of boundary potential, and the potential is a function of the boundary position. In DOI 10.5013/IJSSST.a.16.3B.07 7.4 ISSN: 1473-804x online, 1473-8031 print
addition, it is also required to set up the boundary conditions of the balloon at the outer boundary of the solution region, and to simulate the insulation system. Simulation environment and the following assumptions: 1)The influence of the magnetic flux on the working process of the electromagnet; 2) Without the effect of the magnetic flux response; 3)Ignoring the effect of fluid resistance in the process of friction force, hydrodynamic force on armature movement. Figure 5. The relationship between displacement and output force We can see from Figure 5, in the whole range of proportional solenoid armature, the characteristics of force and displacement between the characteristics of the horizontal characteristics. It can be divided into three sections, in the air gap near zero section, a sharp rise in output force, become the attraction region. In this trip section can not work properly. Therefore, in the structure, the use of the method of limiting the film will be excluded, the armature can not be moved to this section. When the air gap is too large, the output force is obviously decreased, known as the empty travel zone, this section can not work normally, but sometimes it is necessary. In addition to attracting area and air travel to, with horizontal displacement force characteristics of the section become the work area. The length of the working section is related to the type of proportional electromagnet. Figure 4. Proportional solenoid model B. Parametric Simulation and Characteristic Analysis Parametric simulation is a parameter to be set to change the size of the parameters to be studied, the accuracy of the simulation method is higher than that of magnetic circuit. It not only avoids the cost of capital in multi group sample experiments, and can greatly improve the work efficiency. In the case of different coil current, the parameters can be obtained, the static force characteristic curve of the electromagnet is shown in Figure 5, where the horizontal axis is the displacement (mm), and the vertical axis is the output force (N.m). I1=200m, F3 and F2 in Figure 5 are the corresponding currents are I1=400mA, I1=400mA, I1=400mA. IV. CONCLUSIONS The CVT is an important part of the automobile system, which adopts proportional solenoid valve. In this paper, the mathematical model of the electric field and magnetic field of proportional solenoid valve is established, the dynamic characteristics and static characteristics of the electromagnet are described, and the static characteristics of the solenoid valve are analyzed, that in the whole range of proportional solenoid armature, the characteristics of force and displacement between the characteristics of the horizontal characteristics, the length of the working section is related to the type of proportional electromagnet. REFERENCE [1] Vaughan N D, Gamble J B. The modeling and simulation of a proportional solenoid valve. Journal of dynamic systems, measurement, and control, vol.118, No.1, pp.120-125, 1996. [2] Gamble J B, Vaughan N D. Comparison of sliding mode control with state feedback and PID control applied to a proportional solenoid valve. Journal of dynamic systems, measurement, and control, vol.118, No.3, pp. 434-438, 1996. [3] Maiti R, Saha R, Watton J. The static and dynamic characteristics of a pressure relief valve with a proportional solenoid-controlled pilot stage. Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, vol.216, No.2, pp. 143-156, 2002. [4] Lua A C, Shi K C, Chua L P. Proportional assist ventilation system based on proportional solenoid valve control. Medical engineering & physics, vol.23, No.6, pp. 381-389, 2001. DOI 10.5013/IJSSST.a.16.3B.07 7.5 ISSN: 1473-804x online, 1473-8031 print
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