WO1996006388A1

WO1996006388A1 - Circuit for the drive of at least one electrically actuated magnet

Info

Publication number: WO1996006388A1
Application number: PCT/EP1995/002620
Authority: WO
Inventors: Georg Strauss
Original assignee: Bosch-Siemens Hausgeräte Gmbh
Priority date: 1994-08-23
Filing date: 1995-07-06
Publication date: 1996-02-29
Also published as: DE59503808D1; PL318462A1; EP0776496B1; TR199500942A2; PL178333B1; ES2125027T3; BR9508737A; EP0776496A1; CN1160444A

Abstract

The invention concerns a circuit for the drive of at least one electrically actuated magnet by means of an appropriately sized actuation power which causes the magnet to switch a switching element into the desired position where it is held in place. After the switching element has been switched into the desired position, the magnet is repeatedly acted on at predetermined time intervals, at least for a short period, by the actuation power corresponding to this switch position.

Description

Circuit arrangement for controlling at least one electrically controllable magnet

The invention relates to a circuit arrangement for controlling at least one electrically controllable magnet with a targeted control power, by means of which the magnet switches a switching element into a desired switching position in which the switching element is held.

Circuit arrangements according to the preamble of claim 1 are known for the control of bistable solenoid valves used in multi-temperature refrigerators, which serve to control the inflow of refrigerant to the evaporators arranged in compartments of different temperatures. Such circuit arrangements used in cooling devices have a logic part on the input side for evaluating control parameters such as temperature controller signals, with the aid of which a triac or two thyristors arranged antiparallel to one another on the circuit output side to act on the bistable Solenoid valve with the speaking control power are driven. In the case of these semiconductor components, a so-called "overhead ignition" can occur in their supply voltage as a result of mains voltage peaks, by means of which an undesired actuation pulse is generated on the solenoid valve, which then results from a desired temperature controller -Signal-related valve position is converted into its opposite switching position. Such an occurrence can result in the temperature in a freezer compartment of a two-temperature refrigerator rising above the permitted value, so that the goods stored therein are at least significantly impaired in appearance and taste, while on the other hand a drop in temperature in the refrigerator compartment of the device can lead to the destruction of containers cooled with liquid chilled goods.

The invention has for its object to improve a circuit arrangement according to the preamble of claim 1 in such a way that an unintentional change in position of a required switching position of the electrically controllable magnet is avoided.

This object is achieved according to the invention in that after the switching element has been switched into the desired switching position, the magnet is repeatedly acted upon at least briefly with control power corresponding to this switching position at predetermined switching positions. The solution according to the invention ensures that the electrically controllable magnet is always kept securely in its required switching position without additional monitoring and associated evaluation measures, so that undesired misalignments of the electrically controllable magnet, possibly leading to damage, are reliably prevented .

According to a further preferred embodiment of the subject matter of the invention it is provided that semiconductor components are provided for supplying the magnet with control power, which after switching the switching element into the desired switching position are repeated at predetermined time intervals with one that is used to provide the control power Control signal are applied.

With such a solution, an electromagnet can be controlled in a particularly inexpensive and simple manner, the control elements being quickly replaceable in the event of damage.

A particularly simple concept for a logic circuit, with which the possibility of a malposition of the electrically controllable magnet is minimized at the same time, is obtained if, according to a further advantageous embodiment of the subject matter of the invention, it is provided that the time intervals between the control signals are of the same length. According to a further preferred embodiment of the subject matter of the invention, it is provided that the drive power is formed by the half-waves of an alternating voltage, a plurality of which are each generated directly one after the other as a signal sequence, two successive signal sequences being represented by a cycle time of the half-waves are long distance from each other.

Such a solution ensures the required switching position of a switching element actuated by the electromagnet is adequately ensured, at the same time minimizing the energy consumption due to the switching arrangement and its stress.

A circuit arrangement is particularly precisely controlled as required by the corresponding influencing variables if, according to a last advantageous embodiment of the subject matter of the invention, it is provided that the generation of the control signals are generated automatically by a control unit as a function of at least one control parameter.

The invention is explained in the following description using the example of a two-temperature cooling device shown in simplified form in the accompanying drawing. Show it: 1 shows a two-temperature cooling device with opened doors with a cooling compartment and a freezer compartment, the temperatures of which are controlled by an electronic control device,

2 shows a section of the electronic control device with an electronic circuit arrangement for generating control signals to secure the required switching position of a bistable solenoid valve which controls the flow of refrigerant to the cooling compartments,

3 shows the control signals corresponding to the two switching positions of the bistable solenoid valve, each schematically plotted on a time axis.

1 shows a refrigerator and freezer combination 10, the heat-insulating housing 11 of which has two storage compartments which are thermally separated from one another by a heat-insulating partition 12, are arranged vertically one above the other and can be closed with separate doors 13 and 14. The higher-lying storage compartment, which can be closed with the door 13, is designed as a cooling compartment 15, which is equipped with storeys 16 which are arranged one above the other in vertical intervals and serve to store refrigerated goods. The other storage compartment 13 arranged below the cooling compartment 15, separated from it by the heat-insulating intermediate wall 12 and lockable with the door 14, is designed as a freezer compartment 17, which is equipped for the storage of frozen goods with pull-out pull-out frozen food containers 18.

Both the cooling compartment 15 and the freezer compartment 17 are equipped with evaporators (not shown), which are integrated in a refrigeration circuit (also not shown), within which one supplies the evaporators with liquid refrigerant, in order to maintain their intended storage room temperature Compressor is arranged, which is operated intermittently, the on and off phases of the compressor being dependent on the temperatures prevailing in the storage compartments. These are recorded by temperature sensors (not shown) and processed in an evaluation logic 19 belonging to an electronic control device on the one hand to values which can be displayed in temperature display elements and on the other hand processed into digital signals "A" and "B" which can be further processed in a circuit arrangement 30 (See Fig. 2).

As can be seen in particular from FIG. 2, the digital signals "A" and "B" on the output side of the evaluation logic 19 represent input signals for the circuit arrangement 30, a positive output signal "A" being a cooling request for the cooling compartment 15 signals, while a positive output signal "B" means a cooling requirement for the freezer compartment 17. The output signal "A" present at the evaluation logic 19 is assigned to an input of a NAND gate 31 for its further processing via a current limiting resistor 30.1. leads, the second input of which is supplied with an input signal "C". This can assume both the voltage level logic "1" and the voltage level logic "0", which are each generated by a NAND switch trigger 32 merged at its two inputs, the duration of the respective signal state is of different lengths. In the case of logic level "1", this period of time results from the charging time of a resistor 33 connected through an ohmic resistor 33 and a capacitor 34 connected to ground potential with its cathode, the RC element for determining the direction of the charging current having one with its Cathode connection to the ohmic resistor 33 coupled diode 35 is connected upstream. The duration of the logic level "0" for the input signal "C" is determined by an RC element which is formed from the capacitor 34 and an ohmic resistor 36, the resistance value of which for generating a longer period of time for the logic level 0 is clearly above that of Ohm's resistance 33.

Furthermore, the evaluation logic 19 with its output providing the digital signal "A" is connected via a diode 37 coupled with its anode connection to this output to a circuit section belonging to the circuit arrangement 30, which section is required for evaluating the operation of household appliances ¬ Chen AC voltage is used, which through a "L" line pole of the AC voltage network to a current limiting for the operation of logic stone serving resistor 38 is coupled. This is connected to two diodes 39 and 40 arranged in series, the diode 39 with its cathode connection with the positive pole of a direct voltage source U

B is connected while the other diode 40 is connected to its

Anode connection is connected to ground potential, which at the same time forms the zero pole "N" of the AC voltage. The potential which arises at the connection point between the diodes 39 and 40 arranged in series is fed on the input side to a NAND-Schmitt trigger 41, the two inputs of which are connected to one another. The output of the NAND-Schmitt trigger 41 is connected to the cathode connection of a diode 41.1, which is connected on the anode side to an input of a NAND-Schmitt trigger 42, which at the same time also applies the output signal "B" from the evaluation logic 19 is. The signal "C" is present at the other input of the NAND-Schmitt trigger 42. The output of the NAND-Schmitt trigger 42, like that of the NAND-Schmitt trigger 31, is connected to the base of a pnp transistor 43, the emitter connection of which to one

DC voltage supply U is connected while

B its collector connection is connected to ground potential via an ohm ¹ , which limits the collector current. Arranged between the collector connection of the pnp transistor 43 and the ohmic resistor 44 is the gate connection connected to a current-limiting series resistor 44.1 for tapping the ignition current of a triac 45, the second main electrode connection of which is connected to the line pole "L" of a 230 volt AC voltage coupled bistable, two flow paths switching electrically controllable solenoid valve 46 is connected. The other main electrode of the triac 45 is connected to the zero pole "N" of the AC voltage supply.

In the event that there is a need for cooling for the cooling compartment 15 due to the increased temperature therein, this is detected by an already mentioned sensor which monitors the cooling air temperature and the signal generated by the temperature sensor thereupon from the evaluation logic 19 to a logic "1" implemented at their output "A". This level, which is fed to the corresponding input of the NAND-Schmitt trigger 31, works, together with a similar level, generated by the signal "C" at the output of the NAND-Schmitt trigger 31, on the basis of the switch 43 serving pnp transistor 43 acting low level (logic "0"), whereby it is brought into the conductive state.

The input signal "C" at the input of the NAND-Schmitt trigger 31, which is generated automatically by the circuitry of the NAND-Schmitt trigger 32, is only high during the charging time of the capacitor 34 above the resistor 33 (logic "1"), while it has a low level for the discharge duration of the capacitor 34 over the resistor 36, both level states by exceeding or falling below a predetermined switching threshold on the initially linked NAND-Schmitt trigger 32 are effected. The output signal of the NAND-Schmitt trigger 31 is also influenced by the evaluation of the AC mains voltage for operating the fridge-freezer combination (for example 230 volts), both the diode 40 and the diode 37 being affected by the negative half-wave of this sinusoidal AC voltage is set in the conductive state, so that at the input of the signal "A" of the NAND-Schmitt trigger 31 there is a low level for approximately the duration of this half-wave, as a result of which the output of the NAND-Schmitt trigger 31 is at a high level passes over and thus blocks the PNP transistor 43. In contrast, the positive half-wave of the sinusoidal AC voltage can have no influence on the low level originally set at the output of the NAND-Schmitt trigger 31, so that the pnp transistor 43 thus switched through and the ignition of the triac 45 thereby caused one Energizing the bistable solenoid valve 46 causes where takes place by the desired change in position of the valve actuator for redirecting the refrigerant to the evaporator of the cooling compartment 15.

The influence is prevented by wiring the output "A" of the evaluation logic 19 and the input of the NAND-Schmitt trigger 41 with the diode 37, which is arranged in the reverse direction with respect to the output "A", since one for a non-cooling requirement due to the positive half-wave of the sinusoidal AC voltage, no high level can be present at the input of the NAND-Schmitt trigger 31, which would rather lead through the transistor 43 in an unauthorized manner.

For the period of time for which the signal "C" has a high level and the cooling compartment 15 is requesting cold, the solenoid valve 46 is corresponding to the positive half-waves of the sinusoidal alternating voltage which follow one another at equal time intervals, as shown in FIG. 3 under position "1" are shown, acted upon, whereby the valve actuator of the solenoid valve 46, which serves as an armature for the electro-magnets, is held in the desired switching position as required. According to the

Time period, which in Fig. 3 under position "1" with t (=

P time duration of the control pause) and essentially corresponds to the discharge time of the capacitor 34, the signal "C" has a low level, as a result of which a high level is set at the output of the NAND-Schmitt trigger 31, which is the PNP transistor 43 is set in the blocking state, so that the solenoid valve 46 is not acted upon by drive power for this period. After this time t has elapsed, the signal "C" again shows high-pe

P gel, whereby the solenoid valve 46 is again supplied with control power in the form of the positive half-waves of the mains AC voltage supply in order to ensure that the valve switching element of the solenoid valve 46 is reset to the required switching position when this occurs, for example as a result of so-called "overhead ignition" of the triac 45 would have been removed therefrom. Here, the time value for the

Control pause t a time of 30 s already

P bare size, while a time of 70 ms for the duration of the signal "C" has proven to be favorable.

If there is a cooling requirement for the freezer compartment 17, this is signaled by a high level present at the output "B" of the evaluation logic 19, which on the input side via a current-limiting resistor 30.2, as well as the signal "C" on the NAND-Schmitt Trigger 42 is present, which is used to control the pnp transistor 43 when the cold is demanded for the freezer compartment 17 and thus also for the targeted control of the solenoid valve 46 via the triac 45. Whose cooling power is required for the freezer compartment 17 by the negative half-waves of a sinusoidal AC voltage, as shown in FIG. 3 under position "0". The course of the sinusoidal AC voltage is evaluated by the series connection of the diodes 39 and 40, with the connection of the NAND-Schmitt trigger 41 in conjunction with the diode 41.1 only the negative half-wave at a corresponding level of the signal "C" on Output of the NAND-Schmitt trigger 42 is capable of causing a low level and thus switching the pnp transistor 43 through, while the positive half-wave of the sinusoidal AC voltage cannot cause any control of the transistor 43 serving as an electronic switch. By connecting the NAND-Schmitt trigger 41 with the diode 41.1 on the output side, at a high level to the output "B" of the evaluation logic 19, the corresponding input signal The signal at the NAND-Schmitt trigger 42 follows the output signal of the NAND-Schmitt trigger 41, while a low level at the output "B" ensures that this is independent of the output signal of the NAND-Schmitt trigger 41 at the input of the NAND-Schmitt-Triggers 42 remains intact. Analogous to the control of the solenoid valve 46 with the positive half-waves according to the position "1" shown in FIG. 3, the negative half-waves (FIG. 3 position "0") are used as control power only for the period of a high -Level at the output of the NAND-Schmitt trigger 32 supplied to the solenoid valve 46.

In order to be able to ensure after switching the valve switching element serving as an armature into the switching position appropriate for the freezer compartment 17 that the valve switching element of the solenoid valve 46 is in the desired position, this is from time to time with a signal sequence serving as control power in the form of the negative half-waves of the sinusoidal AC voltage, the length of the signal sequence being determined by the duration of the high level for the signal "C" and the duration t between the signal

P follow is determined by the duration of the low level for the signal "C".

Claims

P A T E N T A N S P R Ü C H E

Circuit arrangement for controlling at least one electrically controllable magnet with a targeted drive power, by means of which the magnet switches a switching element into a desired switching position in which the switching element is held, characterized in that the magnet (46) after switching the switching element in the desired switching position (15, 17) is repeatedly acted upon at predetermined intervals with a control power corresponding to this switching position, at least briefly.

Circuit arrangement according to Claim 1, characterized in that semiconductor components (45) are provided for the actuation power to be applied to the magnet (46) which, after the switching element has been switched over to the desired switching position (15, 17) in predetermined positions Time intervals are repeatedly applied with a control signal which serves to provide the control power.

Circuit arrangement according to claim 2, characterized gekenn¬ characterized in that the time intervals between the control signals are dimensioned the same length.

Circuit arrangement according to claim 1 or 2, characterized in that the drive power by the Half waves of an alternating voltage are formed, of which a plurality are generated directly one behind the other as a signal sequence, two successive signal sequences being spaced apart from one another by a time period that is long compared to the cycle time of the half waves.

5. Circuit arrangement according to claim 4, characterized gekenn¬ characterized in that the generation of the control signals are generated automatically by a control unit (32, 33, 34, 35, 36) in dependence on at least one Ansteuerpa¬ parameter.