Abstract:
The invention relates to a method and a circuit for igniting a gas flow in a fully automatic manner. The aim of the invention is to maintain the necessary current consumption so low that an integratable voltage source can be used. To this end, once an electronic control unit has been activated, a thermoelectric safety pilot valve ( 2 ) is opened by an electromagnet which is temporarily excited by a rush of current, is maintained in the open position by a safety pilot magnet ( 6 ) by means of a holding current provided by a voltage source ( 10 ), and the escaping gas is ignited. Once a thermoelectric couple ( 4 ) is provided for the necessary holding current, the voltage source ( 10 ) is switched off. In the event of damage, the method is automatically interrupted.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and all advantages of PCT application No. PCT/EP2004/013000, filed on Feb. 12, 2004, which claims the priority and benefit of German patent application No. 103 95 928.8, filed on Feb. 13, 2003. 
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The invention concerns a process for igniting a gas stream and a circuit arrangement for carrying out this process as can be used for a gas heating stove with gas regulator fittings. 
     (2) Description of Related Art 
     Facilities for a gas heating stove or the like are available in a large number of designs. 
     And so an ignition device for igniting gases is described in U.S. Pat. No. 5,722,823 A. The ignition device has a magnet coil that operates a gas valve, an igniter to ignite the gas stream electrically and a remote control that is connected to the magnet coil and the igniter via a low-voltage line. The remote control includes an energy supply and a time switch for timing the provision of low voltage. 
     This design requires a great deal of energy to ignite the gas stream. So there is provision for three relay coils, which means a relatively high power input. The solenoid valve is constantly energised during the ignition process, which results in a high power consumption. Consequently the only energy supply option is a mains supply. Another disadvantage is that faults occurring within the switch can lead to safety-related issues. 
     A valve device for controlling the ignition of a gas burner is familiar from the GB 2 351 341 A. An operating spindle is moved by hand into the ignition position, which opens the ignition locking valve. The operating spindle needs only be held a short time in this position as a microswitch is engaged when the operating spindle is moved. This causes a voltage to be made available from a power supply to engage the magnet. Ignition takes place by piezoelectric spark ignition. The power supply is switched off when the thermoelectric current provided by a thermocouple is sufficient to keep the ignition locking valve in its open position. 
     Even with this solution use of a power supply is a disadvantage. Additional effort is also needed to carry out the piezoelectric spark ignition. Especially where there is a fairly large conduction gap between the ignition locking valve and the burner aperture there is a further problem insofar as there cannot yet be any ignitable gas mixture at the burner aperture, as the time between the ignition locking valve opening and ignition is relatively short. 
     Further to this DE 93 07 895 U describes a multi-function valve with thermoelectric locking for gas burners on heating devices. This multifunction valve uses a room&#39;s existing power supply to operate it. To ignite the gas stream a magnetic valve is energised via a pushbutton, opening the ignition locking valve. The gas stream is ignited at the same time. A thermocouple in the area of the ignited gas flame is heated and puts a magnetic insert into an energised condition via the resultant thermoelectric current. The magnet holds an anchor firm and so keeps the ignition locking valve linked to the anchor in the open position. Now the pushbutton can be released and the magnetic valve be de-energised. 
     Here it is a disadvantage that the pressure valve must be held long enough until the thermoelectric current holds the ignition locking valve in the open position. It is also a disadvantage that the power consumption is relatively high in view of the fact that the magnetic valve must remain energised for this time via the power supply so that a mains supply is necessary. 
     Both solutions described in GB 2 351 341 A a in DE 93 07 895 U also have the disadvantage that they cannot be run fully automatically, and manual operation is necessary. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is based on the problem of developing a process for fully automatic ignition of a gas stream and a switch arrangement for carrying out this process that has such a low power consumption that it would be possible to employ an integrated electricity source with an adequate life. The structure should also be kept as simple and as inexpensive as possible. 
     According to the invention the procedural problem is solved by activating a transverter, which generates a higher voltage from direct current provided by an electricity source, with which a storage capacitor and an ignition capacitor to provide the ignition voltage are loaded. An essentially familiar ignition locking magnet is activated by a holding current provided by the electricity source, while at the same time an electric circuit that exists between the ignition locking magnet and a thermocouple that can be influenced by the gas flame is interrupted via a relay. The storage capacitor is now abruptly discharged via a circuit element, generating a current surge and briefly energising an electromagnet, to open an essentially familiar ignition locking valve and at the same time applying the anchor of the ignition locking magnet. Owing to the ignition locking magnet activated by the holding current the anchor is held in this position after application and a pilot light to ignite the outflowing gas is generated via an ignition electrode linked with the ignition capacitor via an ignition transformer in a familiar fashion. Subsequently further ignition procedures are initiated whereby the ignition capacitor is recharged and a new pilot light is generated after charging has taken place. After a prescribed period of time ignition is terminated. The holding current flowing from the electricity source to the ignition locking magnet is interrupted and the circuit between the ignition locking magnet and the thermocouple is closed via the relay. 
     This has found a solution, which remedies the aforementioned disadvantages of prior art. A brief operation of the electronic control unit facilitates ignition of the gas stream. In view of the only pulsed operation of the electromagnet, which is independent of how long the control unit is operated, there is a very low power requirement. It also possible to access the electricity source to generate the pilot light, so that there is no need for the additional cost of a piezoelectric ignition device. 
     Advantageous embodiments of the invention are, derived from the other patent claims. 
     It proves to be beneficial if, after the electronic control unit is activated to ignite the gas stream, a check takes place to determine whether a gas flame is alight. If the information is positive the ignition procedure is aborted, while if it is negative the aforementioned steps of the procedure are carried out. 
     There is also an advantageous embodiment of the process if the existence of a thermal electromagnetic force is measured, while other ignition procedures are initiated if there is an absence of thermal electromagnetic force. If however there is evidence of thermal electromagnetic force ignition is terminated. As soon as measurements of thermal electromagnetic force indicate that the electronically calculated thermoelectric current is sufficient to keep the anchor on the ignition locking magnet, the holding current flowing from the electricity source to the ignition locking magnet is interrupted and the electric circuit between the ignition locking magnet and the thermocouple is again closed via the relay. 
     It is also feasible for the storage capacitor and the ignition capacitor to be charged relatively easily via transverters assigned respectively to them at different voltages. 
     There is also a favourable embodiment of the process, if a higher alternating current is generated from the direct current supplied from the electricity source, whereby a power oscillator is used instead of the transverter and the storage capacitor is only switched to a first stage of a multiple cascade when the ignition procedure is initiated, whereupon the storage capacitor and the ignition capacitor connected by electrical conduction with the second stage of the multiple cascade are charged to prescribed higher voltages by means of the higher alternating current via the cascade circuit. After the prescribed higher direct current voltages have been reached the power oscillator is switched off and switched on again when other ignition procedures are initiated. 
     To reduce power requirements even further, which is particularly important when the electricity source is a battery, the dimensions of which can be so small that it can be located together with the electronic control unit in the housing of the receiver portion of a remote control, the holding current supplied by the electricity source to hold the anchor can flow simultaneously through the ignition locking magnet and the relay, while at the time that the electric circuit between the ignition locking magnet and the thermocouple is closed an additional current is briefly generated to safely prevent the anchor dropping out when the relay is rearranged because of the brief interruption in current when the switching contact of the relay is interposed. On the other hand it is also feasible for the voltage of the holding current supplied to the ignition locking magnet from the electricity source to be transverted to the millivolt range via an additional transverter. 
     It is also advantageous if the existence of a thermal electromagnetic force is measured using an analogue amplifier. 
     The safety of the process, such as when a breakdown occurs, is increased by a procedural step, which after a defined period of time has elapsed, also interrupts the energisation of the ignition locking magnet from the electricity source by using one or more independendent safety cutoffs, connected in series and timed. 
     To keep the time between the first ignition procedure and the following ignition procedures as brief as possible, it is desirable to save energy by disconnecting the storage capacitor from the cascade before further cyclical charges of the ignition capacitor. 
     As far as the circuit arrangement is concerned the problem is solved in accordance with the invention by the features stated in patent claim  12 . Advantageous embodiments and evolutionary developments are set out in the associated subclaims. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The procedure that is the subject of the invention and circuit arrangement in accordance with the invention to ignite a gas stream is explained in further detail in an embodiment below. The individual representations show: 
         FIG. 1  a schematic representation of the circuit arrangement, 
         FIG. 2  a detailed representation of the power oscillator 
         FIG. 3  a detailed representation of the analogue amplifier. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The circuit arrangement in accordance with the invention and exemplified in  FIG. 1  to carry out the process of igniting a gas stream is employed on a gas regulating valve. This gas regulating valve is a switching and regulatory device that is preferably intended for installation in a gas-heated chimney stove or similar. It facilitates the operation and monitoring of a burner where the gas volume flowing to the burner is controlled. As well as assemblies that are not material to the invention and not therefore represented in this embodiment, the gas regulating valve also has an ignition burner  1  and a ignition locking valve  2 . The design and function of the ignition burner  1  and the ignition locking valve  2  are familiar to specialists and have not therefore been explained in detail. 
     It is triggered by an undescribed microcomputer module serving as an electronic control unit, which in this embodiment is located in a likewise undescribed separately located housing of the receiver section of a remote control together with an electricity source  10 . The electricity source  10  consists of standard commercial batteries as shown in the drawing, in this case size R 6 . 
     A power oscillator  11  detailed further below that can be triggered from the microcomputer module via a port J, is connected with the electricity source  10 . In series with this is a cascade circuit  12 / 13  which serves to trigger and supply a downstream storage capacitor C 1  and to trigger and supply a downstream ignition capacitor C 2 . As the voltage required to charge the storage capacitor C 1  is significantly less than the voltage required to charge the ignition capacitor C 2 , the cascade circuit  12 / 13  is designed as a multiple cascade circuit. 
     Here the first stage of cascade  12  serves to trigger and supply the downstream storage capacitor C 1 . Downstream from this in turn is an electromagnet  5 , which, as shown schematically in the drawing, serves to actuate an essentially familiar ignition locking valve  2 . In view of the brevity of the charge a low thermal capacity so-called pulse magnet  5  is sufficient. 
     The second stage of the cascade  13  serves to trigger and supply the downstream ignition capacitor C 2 , which is part of an essentially familiar and therefore not further detailed ignition device. The ignition capacitor C 2  can be triggered to ignite by the microcomputer module via port C. The second stage of cascade  13  is connected with an element  14  to monitor the voltage. At the same time element  14  serves to limit the maximum voltage that can occur, to prevent a destruction of components. An additional voltage monitor for the storage capacitor C 1  can be omitted, as after the ignition capacitor C 2  has been charged it can be assumed that the storage capacitor C 1  has also been charged. Port D serves to send a check-back signal to the microcomputer module. 
       FIG. 2  shows in detail the circuit for the power oscillator  11  being used. Power oscillator  11  consists of the CMOS electric circuit  15 , essentially familiar to specialists, with at least four gates. These gates can be NOR gates, NAND gates, simple negators etc. Downstream from them is a complementary field effect power stage  16 , to which an LC series oscillator circuit, consisting of coil 
     L 1  and HF condensor C 3  is connected. An RC link serves as a so-called phase shifter  19  for feedback and phase adjustment. 
     As further indicated in  FIG. 1 , a ignition locking magnet  6  forming part of the ignition locking valve  2  is linked with a thermocouple  4 . The normally closed contact of a monostable relay  17  is also located in this circuit, whereas this circuit is open in the energised state and the ignition locking magnet  6  receives current from the electricity source  10  supplied by the batteries. In addition to this a circuit element, in this case a transistor T 1 , which can be triggered by the microcomputer module via port G, is connected on the one hand with the electricity source  10  and on the other with the relay  17 . A resistor RI is also located in parallel with relay  17 , as the holding current required for the ignition locking magnet  6  is higher than the current flowing through the relay  17 . This circuit also has two series-connected and timed safety cutoffs  18 , which are connected for control purposes with the microcomputer module via the ports H and M. 
     Two further circuit elements, a transistor T 2  and a transistor T 3 , are tied up to this circuit between relay  17  and safety cutoffs  18 . While the transistor T 2 , upstream of which there is a resistor R 3 , is connected with the negative terminal of electricity source  10  and can be triggered by the microcomputer module via the port F, transistor T 3  is connected with the positive terminal of electricity source  10  and can be triggered by the microcomputer module via the port E. 
     In addition to this an analogue amplifier  20  is connected in parallel with the thermocouple  4 . This analogue amplifier  20  has the task of measuring a direct current at thermocouple  4  occurring in the millivolt range, amplifying it and converting it into a range that the microcomputer module can process. As the DC amplifiers otherwise customary for such instances on the one hand require an auxiliary supply above the operating voltage and on the other hand suffer drift deviations, due to temperature influences for example, the analogue amplifier  20  is designed as an AC amplifier. 
     The analogue amplifier, as also described in  FIG. 3 , is described as follows: 
     A field effect transistor T 4  that can be triggered by the microcomputer module via port L and a resistor R 2  form a controllable voltage divider. A pre-amplifier and a booster amplifier are downstream from the voltage divider, with blocking capacitors C 4 /C 5  assigned to each of them. 
     With the pre-amplifier V 1  the reference potential is formed by the positive voltage in order to eliminate fluctuations in the on-board voltage. On the other hand, in the case of the booster amplifier V 2  the reference potential is formed by mass. Both amplifiers V 1 /V 2  and a trigger TR are operated by the microcomputer module through the port K, as they are rendered inoperable when not required to save electricity. The trigger TR behind the booster amplifier V 2  is linked for its part with the microcomputer module via port I. 
     To carry out this process the ignition command is passed on to the microcomputer module via the remote control. The analogue amplifier  20  activated via port K checks whether a thermal electromagnetic force bears against thermocouple  4  and the relevant information is given to the microcomputer module via port I. Whereas the ignition procedure is aborted, if there is an existing thermal electromagnetic force, which is equivalent to a burning pilot light, if there is no thermal electromagnetic force the voltage divider of analogue amplifier  20  is triggered by the microcomputer module via port L. A single switching of the voltage divider will convert the direct current at thermocouple  4  at this time into a pulse of alternating current. The pulse reaches pre-amplifier V 1  via the blocking capacitor C 4 . The signal from the preamplifier V 1  is connected to the booster amplifier V 2  via the blocking capacitor C 5  and further amplified. This analogue signal coming from the booster amplifier V 2  is digitalised by the trigger TR at fixed trigger points, as shown in the diagram associated with  FIG. 3 . 
     The diagram plots the course of voltage U during the time t. In a prescribed voltage level SE and on introduction of the pulse signal IS at time TL the trigger TR sets an initial trigger point TR 1  and at the release of the voltage of pulse signal IS a second trigger point TR 2 , to which a time TE is assigned. The time lapse between the two points in time TL and TE is a measuring signal MS. 
     The measuring signal MS obtained from the existing thermal electromagnetic force reaches the microcomputer module via port  1 . The length of measuring signal MS is directly proportional to the thermal electromagnetic force at thermocouple  4 . 
     Whereas the ignition procedure is aborted if there is any thermal electromagnetic force, i.e. if the pilot light is already burning, if, on the other hand, there is no thermal electromagnetic force the power oscillator  11  will be activated by the microcomputer module via port J and the storage capacitor C 1  will be switched to the first stage  12  of the multiple cascade via port A. 
     Activating the power oscillator  11  starts to oscillate the resonant circuit over the feedback element i.e. the resonant circuit becomes a self-oscillatory and frequency-determining power oscillator  11 . This means that at the output from the power oscillator  11  there is a many times higher alternating current opposed to the low direct current supplied by the batteries at the input. This alternating current charges the storage capacitor C 1  and the ignition capacitor C 2  with the assistance of the two cascade stages  12 / 13 , until element  14 , which serves to monitor the voltage and limit the maximum voltage that occurs, responds and sends a signal via port D to the microcomputer module, which then switches off the power oscillator  11  via the port J. 
     Then the timed safety cutoffs  18  are activated via the port M and the ignition locking magnet  6  is supplied with a holding current from electricity source  10  via transistor T 1  triggered via port G, energising relay  17 , and so opening the circuit between ignition locking magnet  6  and thermocouple  4 . The resonant circuit C 1  is abruptly discharged by the subsequent triggering of port B. Thereupon resonant circuit C 1  is separated from cascade stage  12  via port A. The pulse magnet  5  is briefly energised by this power surge and a tappet  7  is moved far enough against the force of a recoil spring  8  for the anchor  3  to attach to ignition locking magnet  6 . Because of the flowing holding current the anchor  3  is held in this position and the ignition locking valve  2  in the open position. The gas can flow through the gas regulating valve to the ignition burner  1 . 
     If a breakdown occurs as a result of a component failure or the like, after a defined period of time has elapsed the energisation of the ignition locking magnet  6  via electricity source  10  will also be interrupted by one or more independent safety cutoffs  18  connected in series and timed and the ignition locking valve will not remain in the open position, but will be closed again by recoil spring  8 . 
     The microcomputer module activates the ignition device via port C, the ignition capacitor C 2  discharges and the pilot light at ignition electrode  9  flashes over, igniting the outflowing gas. 
     After a prescribed period of time has elapsed, in this example approx. I second, the analogue amplifier  20  is activated via the ports K and L and a check is carried out to determine whether, because heating has commenced as a result of the burning pilot light, a detectable voltage is already being applied on thermocouple  4 , i.e. at least approx. 1 mV. 
     If this is not the case, further ignition procedures will be introduced, while, as already explained in detail above, the power oscillator  11  will be activated, the ignition capacitor C 2  will be charged and then discharged again when a new pilot light is generated. With these following ignition procedures the storage capacitor C 1  is separated from cascade stage  12  to save power, as a further charging of the storage capacitor C 1  is no longer necessary. Should no ignition of the gas occur within a specified period, the microcomputer module will abort the ignition procedure. 
     Should the minimum voltage exist no further ignition procedures will of course be initiated, but the available open circuit voltage of thermocouple  4  will again be checked until the amount of the current electronically calculated from this will be sufficient as holding current for ignition locking magnet  6 . At this point the analogue amplifier  20  is deactivated via port K and the current flowing from the electricity source  10  to the ignition locking magnet  6  is interrupted via port G. The relay  17  is de-energised and the make-and-break contacts of relay  17  close the circuit between thermocouple  4  and ignition locking magnet  6 . The anchor  3  is now held by the thermoelectric current. 
     To prevent anchor  3  dropping out because of the essentially brief interruption of the holding current when the make-and-break contacts of relay  17  are switched over, the transistor T 2  is briefly activated via port F at the time of the switchover and an additional current is generated with similar brevity via the resistor R 3 , safely preventing the anchor dropping off as mentioned above. 
     Should the gas regulating valve be switched off the switch-off command is passed on to the microcomputer module via the remote control. By briefly activating port G and port E while circumventing the safety cutoffs  18  and the ignition locking magnet  6  a power surge is sent through relay  17 , whose make-and-break contacts briefly lift off as a result. This interrupts the holding current flowing between thermocouple  4  and ignition locking magnet  6 . The anchor is no longer held by the ignition locking magnet  6  and the ignition locking valve  2  closes under the influence of the recoil spring  8 . The gas flow to ignition burner  1  and of course to the main burner—not shown—is interrupted and the gas flame is extinguished. 
     The process that is the subject of the invention and the circuit arrangement for carrying out this process are not of course limited to the embodiment described. Alterations, adaptations and combinations are possible without departing from the scope of the invention. 
     It is evident that the transmission of control signals can, as is generally known, be made by cable, infra-red, radio waves, ultra-sound etc. It is also possible for there no remote control to be used and for all the necessary components to be on or in the gas regulating valve. It is also possible for there to be just a main burner, which is ignited directly. Also a small plug-in power supply unit can be used as an electricity source ( 10 ) instead of batteries, which is then easy to plug in. 
     
       
         
               
             
               
               
               
               
             
           
               
                   
               
               
                 List of reference marks 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                  1 
                 ignition burner 
                 C2 
                 ignition capacitor 
               
               
                  2 
                 ignition locking valve 
                 C3 
                 HF - capacitor 
               
               
                  3 
                 anchor 
                 C4 
                 blocking capacitor 
               
               
                  4 
                 thermocouple 
                 CS 
                 blocking capacitor 
               
               
                  5 
                 pulse magnet 
                 IS 
                 pulse signal 
               
               
                  6 
                 ignition locking magnet 
                 L1 
                 coil 
               
               
                  7 
                 tappet 
                 LS 
                 pulse signal 
               
               
                  8 
                 recoil spring 
                 MS 
                 measuring signal 
               
               
                  9 
                 ignition electrode 
                 R1 
                 resistor 
               
               
                 10 
                 electricity source 
                 R2 
                 resistor 
               
               
                 11 
                 power oscillator 
                 R3 
                 resistor 
               
               
                 12 
                 cascade stage 1 
                 SE 
                 voltage level 
               
               
                 13 
                 cascade stage 2 
                 TE 
                 time at TR2 
               
               
                 14 
                 Element for monitoring 
                 TL 
                 time at TR1 
               
               
                   
                 and limiting zung 
                 TR 
                 trigger 
               
               
                 15 
                 CMOS circuit 
                 TR1 
                 trigger point 
               
               
                 16 
                 complementary - field effect 
                 TR2 
                 trigger point 
               
               
                   
                 power stage 
                 T1 
                 transistor 
               
               
                 17 
                 relay 
                 T2 
                 transistor 
               
               
                 18 
                 safety cutoff 
                 T3 
                 transistor 
               
               
                 19 
                 phase shifter 
                 T4 
                 field effect transistor 
               
               
                 20 
                 analogue amplifier 
                 V1 
                 pre-amplifier 
               
               
                 A to M 
                 ports 
                 V2 
                 booster amplifier 
               
               
                 C1 
                 storage capacitor 
                 MS 
                 measuring signal