Abstract:
A circuit configuration operates an electrically triggerable magnet valve having a valve-control element adjustable into at least two working positions for selecting one fluid-flow path at a time to be acted upon by a fluid and corresponding to a respective working position. The circuit configuration includes a device for adjusting the valve-control element into a different working position in connection with an imposition of fluid, predominantly present in liquid components, on at least a portion of a fluid-flow path formed by the magnet valve. A refrigeration appliance, in particular a refrigerator or freezer or a combination refrigerator-freezer includes the circuit configuration.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a Continuation of International Application Serial No. PCT/EP95/02621, filed Jul. 6, 1995. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a circuit configuration for operating an electrically triggerable magnet valve having a valve-control element that can be put into at least two working positions and through the adjustment of which one fluid-flow path at a time that is acted upon by a fluid and that corresponds to the respective working position can be selected. 
     Circuit configurations as defined above are used, for instance, in refrigeration appliances that have a plurality of compartments at different temperatures, for triggering bistable magnet valves that are used there. On the basis of such valves a flow of refrigerant generated by a compressor in a refrigeration circuit is conducted to evaporators in the compartments having various temperatures in accordance with the need for refrigeration. To that end, the valve-control element of the bistable magnet valve is moved into one or the other of its working positions in accordance with the need for refrigeration in storage compartments of the refrigeration appliance. That is done through the use of the force exerted on the valve-control element by the electromagnets and as a consequence of that force the valve-control element is accelerated into its closing position. A clearly audible noise is generated by the closing process. In the past, that noise had been handled through the use of sound damping provisions made in the valve-control element, in the form of plastic parts that cause the closure of nozzle-like supply openings. In the case of such plastic parts, however, if they are not to wear prematurely at the nozzle-like supply openings, a relatively high Shore hardness must be chosen, which necessarily in turn causes not inconsiderable worsening of the acoustical insulation. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide a circuit configuration for operating an electrically triggerable magnet valve and a refrigeration appliance having the circuit configuration, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which enable low-noise operation of an electrically triggerable magnet valve in a simple way. 
     With the foregoing and other objects in view there is provided, in accordance with the invention, a circuit configuration for operating an electrically triggerable magnet valve having a valve-control element adjustable into at least two working positions for selecting one fluid-flow path at a time to be acted upon by a fluid and corresponding to a respective working position, the circuit configuration comprising a device for adjusting the valve-control element into a different working position in connection with an imposition of fluid, predominantly present in liquid components, on at least a portion of a fluid-flow path formed by the magnet valve. 
     Due to the structure according to the invention, speed damping and attendant noise damping for the moving valve-control element are generated, with the damping being constant over the service life of the electrically triggerable magnet valve and being generated by the liquid fluid, since the noise damping is independent of possible changing material properties of materials typically used for acoustical insulation, for example the process of aging in plastics. Moreover, the extent of damping for the valve-control element can be varied in a simple way through the use of the geometrical structure of the valve-control element. 
     In accordance with another feature of the invention, the device for imposing the liquid fluid on the portion of the fluid-flow path formed by the magnet valve is attained by a time lag in the adjustment of the valve-control element with respect to an activation of a device for driving the fluid. 
     The use of such a structure assures that liquid fluid is imposed on the portion of the fluid-flow path formed by the magnet valve in an especially simple way, without additional expense for sensors. 
     In accordance with a further feature of the invention, the time lag can be generated especially simply if the device effecting the time lag is formed by an essentially electromechanically constructed timing element. Moreover, such a timing element is distinguished by its sturdy construction. 
     In accordance with an added feature of the invention, the device effecting the time lag is formed by a timing element composed of electronic components. 
     In such a structure, the order of magnitude of the time lag can also be varied retroactively in a simple way. Moreover, such a timing element can be made extremely economically. 
     In accordance with an additional feature of the invention, the time lag is in a range between 30 seconds and 90 seconds. 
     In accordance with yet another feature of the invention, a time lag that proves to be especially pertinent is 60 seconds. 
     In accordance with a concomitant feature of the invention, the device serving to drive the fluid is constructed as a refrigerant compressor. 
     With the objects of the invention in view there is also provided a refrigeration appliance, in particular a refrigerator or freezer or a combination refrigerator-freezer which includes the circuit configuration. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a circuit configuration for operating an electrically triggerable magnet valve and a refrigeration appliance having the circuit configuration, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic, perspective view of a two-temperature refrigerator shown with opened doors, including a refrigerator compartment and a freezer compartment having temperatures that are controlled by an electronic regulating device; and 
     FIG. 2 is a schematic and block circuit diagram of the electronic regulating device with an electronic circuit configuration for generating trigger signals for triggering an electromagnet valve that controls a flow of refrigerant to the freezer compartment or the refrigerator compartment. 
     FIG. 3 is a schematic diagram of a refrigeration circuit. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is seen a combination refrigerator and freezer  10  which has a heat-insulating housing  11  with two storage compartments that are disposed vertically one above the other, are thermally separated from one another by a heat-insulating partition  12  and are closable with separate doors  13  and  14 . The higher storage compartment, which is closable with the door  13 , is constructed as a refrigerator compartment  15  and is equipped with shelves  16  that are disposed one above the other at vertical intervals and are intended for storing things to be refrigerated. The other storage compartment  17 , which is located below the refrigerator compartment  15 , is separated from it by the heat-insulating partition  12  and is closable by the door  14 , is constructed as a freezer compartment, which is equipped with frozen-product containers  18  that can be pulled out like drawers to hold things to be frozen. 
     FIG. 3 shows that both the refrigerator compartment  15  and the freezer compartment  17  are equipped with evaporators  50  for maintaining their intended storage chamber temperature. The evaporators are incorporated into a likewise refrigeration circuit  51  within which a compressor  52  that supplies the evaporators  50  with liquid refrigerant is disposed. The compressor  52  is operated intermittently, and phases in which the compressor  52  is turned on and off are dependent on the temperatures prevailing in the storage compartments. On one hand, these temperatures are detected by non-illustrated temperature sensors and processed to form values that can be indicated by temperature indicator elements in an evaluation logic element  19  that is part of an electronic regulating device. On the other hand they are processed into a digital signal “A” seen in FIG. 2 that can be further processed in a circuit configuration  30 . 
     As is seen particularly in FIG. 2, the digital signal “A” that is present at the output side of the evaluation logic element  19  represents an input signal for the circuit configuration  30 , which is equipped on the input side with two RC elements serving to attain different time periods. These elements are formed by two parallel-connected ohmic resistors  31  and  32  with different resistances and one common capacitor  33  in series circuit therewith. A diode  34  precedes the resistor  32  with the lower resistance and has an anode terminal connected to the resistor  32 , so that the charging process of the capacitor  33  takes place through the higher-impedance resistor  31 . The voltage potential generated by the charging process at the capacitor  33  is applied to combined inputs of a NAND gate  35  having an output signal which is delivered to a base of a pnp transistor  36 . The pnp transistor  36  has an emitter terminal which is connected to a direct voltage supply “U B ” and a collector terminal which is connected to ground potential through an ohmic resistor  37  that limits the collector current. A gate terminal for tapping an ignition current for a triac  38  is disposed between the collector terminal of the pnp transistor  36  and the ohmic resistor  37 . The triac  38  has a main electrode terminal which is coupled through a monostable electromagnet valve  39  that controls two fluid-flow paths to a line pole “L” of a 230-volt alternating voltage. Another main electrode terminal of the triac  38  is connected to a zero pole “N” of the alternating voltage supply, which at the same time also forms a ground terminal for this main electrode of the triac  38 . 
     A requirement for refrigeration of the refrigerator compartment  15  in response to a rising storage temperature therein is signaled at the output of the evaluation logic element  19  by a logical “1” for the output signal “A”, which on one hand signifies the activation of the refrigerant compressor and on the other hand signifies a switchover process of the monostable magnet valve  39  from its position of repose for changing the fluid-flow path for the refrigerant to the evaporator of the refrigerator compartment  15 . The switchover process of the electrically triggerable magnet valve  39  is delayed in time, as compared with the turn-on process of the compressor, by the RC element formed of the resistor  31  and the capacitor  33 . This is because the logical “1” at the output of the evaluation logic element  19  is applied to the combined inputs of the NAND gate  35  only after the conclusion of the charging process of the capacitor  33  and generates a logical “0” at the output of this NAND gate that is delivered to the base of the pnp transistor  36  acting as an electronic switch, thereby putting this transistor into the conducting state. The current flowing between the emitter and the collector of the pnp transistor  36  as a result of its conduction state acts as an ignition current for the triac  38 , thereby closing the circuit for the monostable magnet valve  39 , so that the desired change of position of its valve-control element, acting for the electromagnets, occurs in order to divert the refrigerant to the evaporator of the refrigerator compartment  15 . 
     The triggering of the magnet valve  39  is delayed, as already described, as compared with the triggering of the compressor, due to the input-side connection of the NAND gate  35  with the RC element formed of the resistor  31  and the capacitor  33 . Intrinsically, because of the output signal “A” being output by the evaluation logic element  19  in the event of a need for refrigerant for the refrigerator compartment  15 , this triggering should occur simultaneously. Due to the time lag between when the compressor is put into operation and when the fluid-flow path for the refrigerant is changed by the magnet valve  39 , it is assured that the latter experiences a flow through it of refrigerant in the liquid phase, so that the switchover motion of the valve-control element that effects the change of direction for the flow takes place in a way that is damped by liquid and thus is maximally noiseless, without additional damping provisions having to be taken. Times that are usable for the order of magnitude of the time lags are those between 30 seconds and 90 seconds which have already shown good results, and a delay of 60 seconds has proved favorable. 
     FIG. 3 also shows that an electromechnically constructed timing element  60  can be used for generating the time lag. 
     Instead of the activation of the magnet valve  39  taking place after the compressor, it is equally possible to provide a liquid sensor to monitor the liquid level in the magnet valve  39  in order to assure the liquid damping for the valve-control element. 
     Once the storage temperature in the refrigerator compartment  15  has reached its intended desired value, this is signaled through temperature sensors to the evaluation logic element  19 , whereupon this logic element outputs a signal for putting the compressor out of operation and outputs a logical “0” as its output signal “A”. This output signal is applied to the input of the NAND gate  35  as a switchover signal for the magnet valve  39 , delayed by the discharge time of the capacitor  33 . Since the resistance of the resistor  32  is much lower than that of the resistor  31 , the switchover process of the magnet valve  39  into its position of repose that opens the fluid-flow path to the freezer compartment evaporator takes place virtually simultaneously with the stopping of the compressor. Due to the slight time lag, for which a time of 50 ms has already proved favorable, it is assured that at least the fluid-flow path of the refrigeration circuit specified by the magnet valve  39  still has liquid refrigerant imposed on it, and thus the switchover process of the valve-control element takes place in a liquid-damped fashion and thus virtually noiselessly. 
     In the event that a need for refrigeration is reported for the freezer compartment  17 , the evaluation signal “A” of the evaluation logic element  19  is a logical “0”, and as a result a logical “1” is applied to the NAND gate  35 . The transistor  38  thus blocks, causing the triac  38  to be inactive and thus depriving the magnet valve  39  of current. 
     Instead of the circuit configuration  30  which is made up of discrete electronic components in the exemplary embodiment, it is also conceivable for its function and that of the evaluation logic element  19  to be simulated by a suitably programmed microprocessor, so that the delayed putting of the magnet valve  39  into operation as compared with the compressor can be accomplished by a suitable software program. 
     It is understood that the invention is also applicable to a wiring of a bistable magnet valve with a valve-specific wiring change that would then be provided in this wiring.