MXPA99008809A - Method for controlling at least one capacitive actuating element - Google Patents

Abstract

The invention relates to a method for controlling at least one capacitive actuating element. The capacity of the actuating element Cp=&Dgr;Q/Up is calculated from the charge quantity (&Dgr;Q) supplied to said actuating element and the voltage (Up) applied to the actuating element once the charging process is complete and the energy (Eist)=0.5*Cp*Up2=0.5*&Dgr;Q*Up supplied to theactuating element during the charging process is calculated from the capacity (Cp) and the voltage (Up) of the actuating element. The charging voltage (UL=UC1 + UC2) is regulated in such a way that the energy (Eist) supplied corresponds to a predetermined set value (Esoll).

Description

PROCEDURE TO CONTROL WHEN LESS ONE MEMBER OF CAPACITIVE ADJUSTMENT FIELD OF THE INVENTION The invention relates to a method for controlling at least one capacitive adjusting member according to the preamble of claim 1.

BACKGROUND OF THE INVENTION German Patent DE 36 21 541 A1 discloses a method for controlling capacitive adjusting members, especially piezoelectrically operated fuel injection valves, of an internal combustion engine, according to which the adjustment members receive a Constant tension. A piezo-adjustment member consists of a plurality of piezoceramic layers and forms a so-called "stack", which upon receiving a voltage modifies its dimensions, in particular its length, or which with mechanical pressure or traction generates an electrical voltage. The electrical properties of a piezo-battery of this type vary with the temperature at which it is located. With an increasing temperature, the capacity increases, but also the route. In the case of temperatures of approximately -40 ° C to + 150 ° C, to be considered for automotive applications, variations of up to factor of 2. If, for example, a piezo-adjustment member is loaded at all operating points at a constant voltage, which at low temperatures provides the necessary travel, at high temperatures a path is obtained which is considerably greater than the required, which, in the case of fuel injection valves with constant fuel pressure, involves too much fuel. Since at higher temperatures the piezo-pile capacity is also higher, much more load and energy are taken than necessary. Therefore, the process known from the German patent DE 36 21 541 Al only works with sufficient precision with limit conditions without any modification (no tolerance of the components used, no variation of the electrical properties, constant temperature). From US Pat. No. 5,387,834 a control circuit for a capacitive adjusting member is known, which is controlled by a constant load voltage and a determined charging duration depending on the temperature of the adjustment member measured with a sensor.

OBJECTIVES AND ADVANTAGES OF THE INVENTION The objective of the invention is to provide a procedure to control at least one capacitive adjusting member, which works with sufficient precision even when the limit conditions vary, without using a temperature sensor. This object is achieved in accordance with the invention with the features indicated in claim 1. Advantageous developments of the invention are pointed out in the sub-claims. The investigations showed that the energy supplied to a capacitive adjusting member is a much more accurate measurement of the distance ds than the applied voltage, and that a load with constant energy in the required temperature range results in an essentially more constant travel . The path varies approximately linearly with the voltage applied at a certain temperature. If the temperature varies, the path also varies with the constant voltage. On the other hand, the path varies proportionally to the square of the energy supplied, but independently of the temperature. Also, from the load? Q fed to the adjustment member and the voltage U "measured after the charging process is finished therein, for example Pl, the capacity C" =? Q / U "of the member of the device is determined. fit and subsequently, from? Q and C », the energy fed to the member E_real = u" 5 ° x * • C * "" D x * - * - * UUD '= 0? .- 5 ° x- •? iXQ ^ x • x- Uuntv. E • "- '• s' = > t'-e ^ vvacilioorr E- ^ teal is compared with a predetermined Eteoric value and according to the result of the comparison, the load voltage UT is regulated for the following control process (U * - ^ increases when Ereal < Eteoric Y is decremented when Efeal > Eteórico). In a method that can be used for any control circuit, the amount of applied load ΔQ is determined by the integration of the current I "flowing through the adjusting member during the charging process. A) Yes: ? Q = íipdt = Jipdt / Up - > E.real = 0.5 x íip t x U " For circuits with charge and discharge capacitors connected in series, as shown in the drawing, there is a simpler procedure for determining the amount of charge? Q fed to the adjustment member, in which no integration is required. In this procedure, the voltage in the discharge capacitor C2 is measured before the charging process and after the charging process is completed, and the difference? U = Uantes - U¿ | eSpUgs is calculated and the load quantity is determined from it ? Q = C2 x? U = C2 x (Ua, ntes - U¿eSpU £ s). With the tension U_ on the adjustment member after completing the charging process, analogously to the procedure indicated above, the capacity of the adjustment member and the energy Ereaj supplied thereto are determined: ? Q = C2 x (Uantes - U after) - > Cp = C2 x (Uantes - U afterwards) / Up • > E. real 0. 5 X C2 x (Uantes - U afterwards) x Up This value, as described above, is compared with a predetermined theoretical value and according to the result, the load voltage Uj ^ is regulated for the next control process. Since the capacity of the adjustment member C- is approximately proportional to the temperature of the same Tp, the capacity of the adjustment member CL calculated according to the formula CP "=? Q / UP" Tp, can be used for the determination of the temperature of the adjustment member Tp and, optionally, omitting a temperature sensor.

BRIEF DESCRIPTION OF THE DRAWINGS The method according to the invention is illustrated with the aid of a circuit, which is observed in the drawing, to control at least one adjustment member capacitive Pl a Pn, for the actuation of at least one fuel injection valve not shown, by means of a control circuit ST, which is part of a motor control apparatus operated by a microprocessor, also not shown. DETAILED DESCRIPTION OF THE INVENTION Between the positive pole + U < j p * - * and the negative pole GND of a regulated voltage source SNT, preferably of a part of a combinational logic network, is connected to a charging capacitor Cl through a DI diode. Parallel to the charging capacitor Cl is a serial connection of a load switch Ta, two additional diodes D2 and D3 and a discharge switch Tb connected to the negative pole GND. Between the junction point of the two diodes D2 and D3 and the ground connection GND, there is a series connection of a load reversal capacitor C2, an oscillatory coil L, a first adjustment member Pl and a first switching element IT selection controlled. For each additional adjustment member P2 to Pn, a series connection of said member and another selection switch T2 to Tn is connected in parallel to the series connection of the first adjustment member Pl and the first selection switch TI. The selection switches, the discharge switch Tb and the bypass switch Te cited below, are in this mode N-MOSFET power switches, which usually contain inverting diodes. The load switch Ta is configured in this mode as a power switch P-MOSFET. In addition, an already mentioned bypass switch Te is provided, whose drain connection is connected to the connection point between the oscillatory coil L and the adjustment members Pl to Pn, and whose source connection is connected to the source connection when minus a TI selection switch. All the switches are controlled through their gate connections by the output signals of the control circuit ST. The bypass switch Te arranged in parallel to the adjustment members Pl to Pn, is controlled by the control circuit ST, when the tension of the adjustment member exceeds a previously established limit value or when a fault is detected in the internal combustion engine until the final power stages of the injection valves, and discharges the capacitive adjusting members Pl a Pn in the manner of a short circuit, through the inverting diodes of the selection switches TI to Tn. The bypass switch Te is also required to charge the discharge capacitor C2 prior to the first actuation of an adjustment member or to discharge between two adjustment member drives spaced in time.

Instead of the bypass switch Te, it is also possible to provide a diode or Zener diode with the same polarity as the reversing diodes of the bypass switch, then it is necessary to charge the discharge capacitor C2 by means of an actuator actuator, in a fuel injection valve preferably without fuel pressure. The switches Ta, Tb, Te and TI to Tn are controlled by the control circuit ST depending on control signals st of a motor control apparatus not shown. The charge capacitor Cl can be considered as an output capacitor of the SNT combinational logic network part. The control process for this circuit is described below. During the operation thereof, the charge capacitor Cl is charged to an output voltage + Ug- of the part of the combinational logic network SNT, determined by the SNT control circuit. The determination of such tension is illustrated below. At the start of the operation, the capacitor Cl is charged to + <j] st4j, and the discharge capacitor C2 is discharged and the oscillating coil L is de-energized. So that the capacitor C2 is also charged before the first adjustment member drive, it is first passed to driver the bypass switch Te. In this way Cl is discharged through C2, L and Te. Immediately, it happens again to non-driver and the discharge switch Tb is passed to the driver. Thus, for L, C2, Tb and the inverter diodes of the bypass switch a current flows in the opposite direction, whereupon C2 is charged and polarized in such a way that, after one or more charge and discharge cycles, in the series connection of Cl and C2 is the load voltage r ^ = U ^ -j + U ^ - Through a measuring circuit configured as Sample-and-Hold switch S & H, the voltage U 2 in the capacitor C2 is notified to the control circuit ST, which thus adjusts the output voltage + Ugjsj- * r- = U of the part of the combinational logic network SNT, which in the series connection of Cl and C2 is a predetermined initial tension. Since, in the case of non-driving, the voltage U 2 in the capacitor C2 decreases slowly, also during operation, for example during the charging process at a low number of revolutions (i.e., in the case of member drives) of adjustment more spaced in time), or in displacement operation, these recharges of the discharge capacitor C2 are carried out. If a member drive is to take place adjustment, by means of a measuring circuit M, which can consist in the simplest case of a shunt resistance, after the first process the current Ip flowing in the control circuit is measured and integrated into an integrator that is in the control circuit. Since the measurement circuit M is only required for this process, in the drawing it is framed in dotted lines and the reference for current Ip is in parentheses. The other course of this procedure works as in the second process described below. According to this simpler second process, before the loading of the adjustment members, the voltage U? V- »is measured.

= Uan, it is in the discharge capacitor C2 and it is notified to the control circuit ST. Next, the load switch Ta and the selection switch TI assigned to the corresponding adjustment member are passed to conductors, for example, Pl. Flow of SNT and Cl flows through Ta, C2, L, Pl and TI into GND. , until the adjustment member is loaded. Subsequently, Ta and TI become non-conductors, the adjustment member remains charged. At this moment the voltage U2 = udesnues is measured in e ** - capacitor d discharge C2 and the voltage Up in the adjustment member Pl, and is notified to the control circuit ST. Does it calculate the energy Erea according to the formulas mentioned above? fed to the adjustment member and compares said value with a predetermined theoretical value E-theoretical- According to the above, the load voltage Uj ^ needed for the next control process is determined.

Yes Erea1t < Eteráco, the load voltage Uj ^ is increased, for example by levels, in a level with respect to the value previously valid; yes Ereaj > te ^ co, then a level is decreased. Is the charge voltage U-r ^ regulated to Erea? = -e ^ rjco. The state of charge of the adjustment member Pl is maintained until, when the control signal st disappears, the discharge switch Tb passes to the conductor. With this switch driving, all the adjustment members Pl a Pn are discharged to the discharge capacitor via the coil L. The voltage U ^ in the discharge capacitor C2 after discharging the adjustment members is communicated through the Sample-and-Hold switch S & H to the control circuit ST, which regulates the output voltage + U in such a way * SNT of the part of the combinational logic network SBT, which in the following control process reaches the load voltage previously determined U- ^ = U ^ + ~ ÜQ2 'With this load voltage the following charging process can be carried out of the adjustment member Pl, or else the loading process of the next adjustment member P2, etc.

Claims (4)

NOVELTY OF THE INVENTION Having described the above invention, it is considered as a novelty, and therefore, the content of the following is claimed as property: CLAIMS

1. A method for controlling at least one capacitive adjusting member (Pl to Pn) by a charging voltage (Uj, characterized: because from the charge amount? Q fed to the adjustment member (Pl to Pn) and the voltage from the same Up after completing the loading process, the capacity of the adjustment member is calculated according to the Cn equation because from the values of adjustment member capacity C_ and adjustment member voltage Up, the energy Erea1 supplied to the adjustment member during the charging process is calculated, according to the equation Erea? = 0.5 x Cp x Uß = 0.5 x? Q x Up, because the value of the supplied energy Ereaj is compared with a predetermined theoretical value (-e r ^ co, and because the load voltage UT = U I +? for the next control process it increases by a predetermined value, when the energy supplied Ereaj is less than the theoretical value Ete ^ rjco, or is decremented, when the energy supplied Erea? is greater than the theoretical value

Eteoric • 2. A method according to claim 1, characterized in that the amount of charge? Q supplied to the adjustment member (Pl to Pn), is determined by integrating the current Ip flowing through the limiting member. adjustment during the charging process, according to the equation? Q = j Ipdt.

3. A method according to claim 1, characterized in that in the case of circuits with charge and discharge capacitors (Cl, C2) in series connection, where on the charge capacitor (Cl) can be applied an adjustable voltage (- ^ Ug ^ -j, the quantity of charge? Q supplied to the adjustment member (Pl a Pn) is determined, through the difference? U = Uantes - after the voltages Uantes and U afterwards in the capacitor of discharge (C2) before and after the loading process, and the capacity C2 of it, according to the equation? Q = C2 x? U = C2 x (Uantes - UdeSpU? s).

4. A method according to claim 1, characterized in that the calculated capacity of the adjustment member Cp is used to determine the temperature of the same Tn.