EP1023533A1

EP1023533A1 - Method for controlling an electromechanical actuating device

Info

Publication number: EP1023533A1
Application number: EP98952541A
Authority: EP
Inventors: Achim Koch; Hanspeter Zink
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1997-10-15
Filing date: 1998-09-02
Publication date: 2000-08-02
Anticipated expiration: 2018-09-02
Also published as: EP1023533B1; US6483689B1; DE19745536C1; JP2001520494A; DE59804352D1; WO1999019615A1

Abstract

An actuating device has an actuating element (12) and an actuating drive (11). Said actuating drive has at least one electromagnet with a coil (113), a moveable retaining plate (117) and at least one spring (118a, 118b) which prestresses the retaining plate into a predetermined neutral position (R). The coil generates a retarding field whilst the retaining plate moves away from the coil for a predetermined period of time (T2).

Description

description

Method for controlling an electromechanical actuator

The invention relates to a method for controlling an electromechanical control device according to the preamble of claim 1. It relates in particular to a control device for controlling an internal combustion engine.

An open actuator (DE 195 26 683 AI) has an actuator, which is designed as a gas exchange valve, and an actuator. The actuator has two electromagnets, between which an armature plate can be moved against the force of a restoring means by switching off the coil current on the holding electromagnet and switching on the coil current on the capturing electromagnet. The coil current of the respective catching electromagnet is kept constant at a predetermined catch value for a predetermined period of time and then regulated by a two-point controller with hysteresis to a hold value until the coil current is switched on.

Production variations and deviations from the specified arrangement of the components of the actuator, in particular the restoring means, have the effect that the rest position specified by the restoring means is not symmetrical to the contact surfaces on the electromagnets. For example, the armature plate may collide strongly with an electromagnet if the armature plate is moved from one electromagnet to the other. The impact creates a loud noise.

Ever stricter legal limits for sound radiation from a motor vehicle and requirements for a quietly running internal combustion engine are making it suitable for the sea oes control unit imperatively requires that the sound generation by the control unit is low.

The object of the invention is to provide a method for controlling an actuating device which reduces the sound generation when an armature plate strikes an electromagnet.

The object is achieved by the features of patent claim 1. The solution is characterized in that while the braking value is specified as the setpoint for the current, the current causes a braking field which generates a force which is directed counter to the acceleration force which acts on the armature plate. The acceleration force is caused by the tension of the springs. The impact speed of the anchor plate is reduced by the braking field. The solution also has the advantage that wear on the actuator is reduced.

In advantageous embodiments of the invention, the

Time period T2 depends on the speed and a load size or a speed of the anchor plate or the braking value depends on the speed and the load size or speed of the anchor plate. This enables a targeted, asymmetrical adjustment of the rest position of the anchor plate without the sound radiation being increased during operation of the actuating device. This is particularly useful if the actuator is an exhaust valve, since this must be opened against the exhaust gas pressure in the cylinder.

Further advantageous embodiments of the invention are characterized in the subordinate claims.

Exemplary embodiments of the invention are explained in more detail with reference to the schematic drawings. Show it: FIG. 1 shows an arrangement of an actuator in an internal combustion engine,

FIG. 2 shows a circuit arrangement of the driver for the control device,

FIG. 3 shows a block diagram of a control device for controlling the control device,

4 shows a state diagram of block B6 of the control device, FIG. 5a-e shows the time course of the control voltages, the current through the first and second coil, the position of the armature plate and an output signal of a comparator device 7.

Elements of the same construction and function are provided with the same reference symbols in all figures.

An actuator 1 (FIG. 1) comprises an actuator 11 and an actuator 12, which is designed, for example, as a gas exchange valve and has a shaft 121 and a plate 122. The actuator 11 has a housing 111 in which a first and a second electromagnet are arranged. The first electromagnet has a first core 112, in which a first coil 113 is embedded in an annular groove. The second electromagnet has a second core 114, in which a second coil 115 is embedded in a further annular groove. The first core 112 has a recess 116a, which forms a guide for the shaft 121. The second core 114 has a further recess 116, which also serves as a guide for the shaft 121. An anchor plate 117 is movably arranged in the housing 111 between the first core 112 and the second core 114. A first spring 118a and a second spring 118b bias the anchor plate 117 into a predetermined rest position t on R. The actuator 1 is rigidly connected to a cylinder head 21. An intake duct 22, an exhaust duct 22a and a cylinder with a piston 24 are assigned to the cylinder head 21. The piston 24 is coupled to a crankshaft 26 via a connecting rod 25.

A control device 3 is provided which detects signals from sensors and generates control signals for the control device 1. The sensors are a position sensor 4, which detects a position X of the armature plate 117, a first ammeter 5a, which detects the actual value I_AV1 of the current through the first coil 113, a second ammeter 5b, which detects an actual value I_AV2 of the current through the second coil 115 detects a speed sensor 27, which detects the speed N of the crankshaft 26, or a load detection sensor 28, which is preferably an air mass meter or a pressure sensor. In addition to the sensors mentioned, other sensors can also be present.

A comparator device 7 is provided which generates a pulse signal depending on the detected position X and predetermined threshold values K1, K2, K3, K4. The comparator device 7 has four analog threshold value comparators, each of which changes its output signal at one of the threshold values K1, K2, K3, K4. The pulse signal of the comparator device, which is plotted in FIG. 5e, then arises through a logical combination of the threshold value comparators. The threshold values K1, K2, K3, K4 (FIG. 5d) are, for example, at the following relative distance values, which are based on the distance between the contact surface of the armature plate 117 for the first electromagnet and the contact surface of the armature plate 117 for the second electromagnet: Kl 5%, K2 at 20%, K3 at 80% and K4 at 95%. A timing element 8 (FIG. 1), which is preferably designed as a so-called “CAPCOM” unit, detects the pulse duration of the pulse signal generated by the comparator device 7 and forwards the time durations T_C2, T_02 assigned to the pulse durations to the control device 3 as digital data.

In a first approximation, the time period T_C2 is a measure of the average speed of the anchor plate between the threshold values K3 and K4. In a first approximation, the time period T_02 also determined by the timer 8 is a measure of the average speed of the anchor plate 117 between the threshold values K2 and K1.

Drivers 6a, 6b are provided which amplify the control signals of the control device 3. A circuit arrangement

(Figure 2) of the driver 6a, 6b has a first transistor 61 whose base connection is connected to an output of the control device 3 and to which the voltage signal U _S n is present. Furthermore, the circuit arrangement has a second transistor 62, the base connection of which is connected to the control device 3 and to which the voltage signal U _s2 ι is present. The circuit arrangement also has a first diode 63, a second diode 64 and a capacitor 65.

If a high voltage level is present at the base-side connection of the first transistor 61, the first transistor 61 becomes conductive from the collector to the emitter. If a high voltage level is additionally present at the second transistor 62 at the base-side connection, then the second transistor 62 also becomes conductive. The supply voltage U _v then drops approximately at the first coil 113. The current I_AV1 through the coil 113 then increases until the entire supply voltage U _v across the internal resistance of the first coil 113 drops. If a low voltage level is then specified at the base-side connection of the first transistor 61, the block Transistor 61 and the diooe 63 becomes conductive as a freewheeling diode. The current I_AV1 through the coil then ate. By setting the voltage level of the voltage signal U _S noc and low, a two-point control of the current I AVI through the coil takes place.

If both the voltage level of the voltage signal Usn and the voltage level of the voltage signal U _Ξ2 ι are switched from high to low, both the first diode 63 and the second diode 64 become conductive and the current through the first coil 113 is driven by the charge of the capacitor 75, is reduced considerably more quickly than if e freewheeling takes place only via the first diode 63. This ensures a very rapid reduction in the current I_AV1 through the first coil 113.

The circuit arrangement of driver 6b is analogous to the circuit arrangement shown in FIG. 2. It differs only in that the voltage signal U _S ι ₂ is present at the base-side connection of the first transistor 61 and the voltage signal U _Ξ22 is applied to the base connection of the second transistor 62, and in that the emitter of the first transistor 61 and the collector of the second Transistors 62 are electrically conductively connected to the second coil 115.

FIG. 3 shows a block diagram of the control device 3 for controlling the electromechanical control device 1. In a block B1, a catch value I_F1 is determined from a map, depending on the speed N and the air mass flow MAF. The values of the map are determined on an engine test stand or by simulations in such a way that heat losses m of the respective coil are low.

The difference between the setpoint T C2 * and the actual time period T C2 is calculated in a summing point S1. The Setpoint T_C2 * is fixed. Alternatively, it can also be determined from a map depending on at least one variable detected by the sensors. Em block B2 comprises an integrator which, depending on the difference between the setpoint T_C2 * and the actual time period T_C2, calculates a correction value with which the summing point S2 or the catch value I_F is corrected. As a result, influences due to production variation and aging of the actuator are taken into account.

In a block B3, a hold value I_H is dependent on the

Drenzahl N and the air mass flow MAF determined from a map. In a block B4, a braking value is determined from a characteristic field as a function of the speed N and the air mass flow MAF and / or as a function of the integral via the deviation of the target value T_02 * and the actual time period T_02. The setpoint T_02 * is fixed. Alternatively, however, it can also be determined from a map depending on at least one variable detected by the sensors.

In a block B5, the time period T2 is determined from a map as a function of the speed N and the air mass flow MAF and / or the integral of the difference between the target value T_02 * and the actual time period T_02.

In block B6 it is determined whether the catch value I_F1, the hold value I_H, the braking value I_B or a zero value I_N (eg zero amperes) is assigned as the setpoint I_SP1 of the current for a controller B7. The controlled variable of the controller B7 is the current through the first coil 113. The function of the block B6 is described below with reference to FIG. 4.

The difference between the setpoint I_SP1 determined in block B6 and the actual value I_AV1 of the current through the first coil 113 is the control difference of the two-point controller with hy sterically trained regulator B7. The manipulated variables of the controller B7 and the voltage signals U _s π and U _s2 ι.

In FIG. 3, the block diagram is shown as an example for the calculation of the control signals for the first coil 113. The control signals for the second coil, ie the voltage signals U _S ι ₂ , U _s22, are _calculated analogously, only the time periods T_C2, T_C2 * are to be replaced by the time periods T_02, T_02 *. The output variable of block B6 is then the setpoint I_SP2 of the current through the second coil

115, em regulator B8, which is the same in construction as the regulator B7 nat as the controlled variable the current through the second coil 115 and has the voltage signals U _Ξ ι ₂ and U _{s22 as manipulated variables} .

FIG. 4 shows the state diagram of block B6 as an example for the calculation of the setpoint I_SP1 of the current through the first coil 113. The first state ZI is the start from which the transition takes place in a state Z2 when the condition E1 is fulfilled that em Setpoint X_SP of position X is equal to a closed position C of anchor plate 117. In the state Z2, the setpoint I_SP1 is the catch value I_F.

From state ZI there is a transition to state Z3 if a condition E2 is fulfilled, specifically that the setpoint X_SP of position X is equal to an open position 0. In state Z3, the setpoint I_SP1 is equal to the zero value I_N.

A transition from the state Z2 to a state Z4 takes place if the period dt since the state Z2 was taken is greater than a period T0. The time period T0 is either fixed or determined by the detection of the impingement of the armature plate on the first electromagnet. In the state Z4, the setpoint I_SP1 of the current through the first coil 113 is the hold value I_H. The transition from the state Z4 to a state Z5 takes place when a condition E4 that the setpoint X_SP of the position X of the anchor plate 117 is the open position 0 is fulfilled.

In the state Z5, the setpoint I_SP1 of the current through the first coil 113 is the zero value I_N. A transition from the state Z5 to a state Z6 takes place when the condition E5, in that the time period dt since the taking of the state Z5 is greater than a time period T1, is fulfilled. The time period Tl is predetermined such that a transition from the state Z5 to the state Z6 occurs at the earliest when the armature plate 117 begins to move away from the first electromagnet.

15

In the state Z6, the setpoint I_SP1 of the current through the first coil 113 is the braking value I_B. The condition E6 for a transition from the state Z6 to the state Z3 is that the time period dt since the state Z6 was taken is greater than

20 the time period T2. In the state Z3, the setpoint I_SP1 of the current through the first coil 113 is the zero value I_N. The condition E7 for the transition from state Z3 to state Z2 is that the setpoint X_SP of the position of the anchor plate is equal to the closed position C.

25

The state diagram of block B6 for determining the setpoint I_SP2 of the current through the second coil 115 corresponds to the state diagram according to FIG. 4, with the difference that the closed position C by the open position 0 and

30 is to be replaced in reverse and that the setpoint I_SP1 is to be replaced by the setpoint I_SP2.

Figure 5a shows the voltage signal U _Ξ n and the voltage signal U _Ξ ι ₂ (shown in dotted lines) plotted over the Figure 5b shows the voltage signal U _s2 ι and the voltage signal Us22 (shown in dotted lines) plotted over time t.

FIG. 5c shows the assigned time profile of the actual value I_AV1 of the current through the first coil 113, and the time profile of the actual value I_AV2 (shown in dotted lines) of the current through the second coil 115.

FIG. 5d shows the assigned position X of the anchor plate 117 plotted against the time t.

Up to a point in time ti, the setpoint value of the current through the first coil 113 is the hold value I_H. The holding value I_H is predetermined such that the force on the armature plate 117 caused by the current through the first coil 113 is sufficient to hold the armature plate in contact with the first electromagnet and, on the other hand, only slight heat losses occur.

At a point in time ti, the zero value I_N is specified as the setpoint I_SP1 of the current through the first coil 113 for the time period T1. At time t _x , both the voltage signal U _s n and the voltage signal U _s2 ι are set to a low level, so that the actual value I_AV1 of the current through the first coil drops very quickly to the zero value I_N. After the time period Tl has elapsed from the time ti, the braking value I_B is specified as the desired value of the current through the first coil 113 at a time t ₂ , for the time period T2. If the time period T2 depends on the speed and the load replacement size, preferably the air mass flow, the rest position R can be specified asymmetrically to the contact surfaces of the armature plate on the two electromagnets. This is advantageous if the actuator is used as an outlet valve is trained that the exhaust valve must be moved during the transition from the closed position C to the open position 0 against oen low cylinder pressure. The time period Tl is preferably chosen so that the anchor plate at time t _; is still close to the closed position (e.g. has only covered 3% of the way between the closed and open positions). A very good braking effect on the anchor plate is achieved.

From a point in time t ₄ , the first coil again specifies the zero value I_N as the setpoint I_SP1 of the current. From the time t ₈ , the setpoint I_SP1 of the current through the first coil is given the catch value I_F, specifically for the period T0.

At a point in time t ₃ , the catch value I_F is specified as the setpoint I_SP2 of the current through the second coil 115. The time t ₃ can also be in time after the time t ₄ .

The associated course of the position X of the anchor plate shows that after the time ti the anchor plate first remains in the closed position C and then moves with increasing speed in the direction of the open position 0 until the acceleration of the anchor plate 117 decreases from time t ₂ and the anchor plate reaches the open position 0 at time t ₅ .

The invention is not limited to the exemplary embodiment described. The method can be executed as a program by a microprocessor. However, it can also be implemented by a logic circuit or by an analog circuit arrangement. The catch value I_F and / or the holding value I_H and / or the braking value I_B can also be fixed, predetermined values. The controller can also be designed, for example, as a single-point controller with a timing element or as a pulse width modulation controller. A particularly low sound radiation from the actuator is achieved if the catch value I_F is additionally reduced, specifically for a period of time that depends on the difference between the setpoint T_C2 *, T_02 * and the actual period T_C2, T_02.

The catch value is, for example, eight amperes, the hold value three amperes and the braking value ten amperes.

Claims

claims

1. A method for controlling an electromechanical actuator, which has an actuator (12) and an actuator (11), which has:

- A first electromagnet with a first coil (113) and a second electromagnet with a second coil (115), and

- A first and a second spring (118a, 118b), which bias the anchor plate (117) into a predetermined rest position (R), the actuator (12) being assigned a controller (B7, B8) for each coil, the The controlled variable is the current through the respective coil (113, 115), with the following successive steps: a hold value (I_H) is specified as the setpoint value of the current through either the first or second coil (113, 115) up to a point in time (tl),

- A zero value (I_N) is specified as a setpoint for a period (Tl), - A braking value (I_B) is specified as a setpoint for the further period (T2), and

- The zero value (I_N) is specified as the setpoint.

2. The method according to claim 2, characterized in that a position transmitter (4) for detecting the position (X) of the anchor plate (117) is provided, and that the time period (Tl) depends on the position (X).

3. The method according to any one of claims 1 to 2, characterized in that the further time period (T2) depends on the speed (N) and a load size.

4. The method according to any one of claims 1 to 3, characterized in that the braking value (I_B) depends on the speed (N) and the load size.

5. Verkanren nacn one of claims 3 or 4, daourcn characterized in that the load size of the air mass flow (MAF)

6. The method according to any one of the preceding claims, characterized in that the further time period (T2) depends on the speed of the anchor plate (117).

7. The method according to any one of the preceding claims, characterized in that the braking value (I_B) depends on the speed of the anchor plate (117).

8. The method according to any one of claims 6 or 7, characterized in that the speed of the anchor plate (117) is approximated by the time period (T_02, T_C2) which the anchor plate (117) requires in order to a first threshold value (K2 , K3) of position (X) to reach a second threshold value (K1, K4) of position (X).