Abstract:
A burner system for controlling the gas/air mixture of a burner has a sensor providing a signal dependent on the pressures in gas and air lines supplying the burner. A summing device receives a signal based on the air flow rate and the signal from the sensor, and provides a regulating signal controlling the setting of a gas regulating valve regulating the flow of gas in the gas line.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This patent application is a continuing application of U.S. patent application Ser. No. 09/701,687 filed on Mar. 9, 2001 now ABN by Derk Vegter. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a regulating system for controlling the gas/air mixture of gas burners. 
     Regulating systems for gas burners serve to provide a gas/air mixture, that is, they serve to feed a gas flow and a combustion-air flow to a burner. In this case, the gas flow through a gas valve can be set as a function of the combustion-air pressure. Such regulating systems have been disclosed by DE 24 27 819 B2, Austrian Patent 190 195 and De 37 07 883 C1. 
     Regulating systems for gas burners are known in which the transmission ratio between gas pressure and combustion-air pressure or between gas flow and combustion air flow is variable. In all the known regulating systems, the requisite pressure measurement is carried out by means of a diaphragm, that is pneumatically. However, this pneumatic method has a large number of disadvantages, which all together restrict the range of application of known regulating systems. Thus the hysteresis properties of the diaphragm and the forces acting between the diaphragm and the gas valve restrict the working range and thus the range of application. Furthermore, the interplay between the requisite small actuating forces and the operating tolerances of the diaphragm, as a result of disturbances such as temperature fluctuations or the like, restricts the range of application of known regulating systems. 
     Against this background, the problem underlying the present invention is to provide a regulating system for gas burners which avoids the abovementioned disadvantages and thus has a greater range of application. 
     BRIEF DESCRIPTION OF THE INVENTION 
     This problem is solved by a regulating system for gas burners that controls gas flow based on the air flow and the pressures in the gas flow and air flow ducts. 
     Further advantageous refinements of the invention follow. A preferred exemplary embodiment of the invention is explained in more detail below with reference to the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows a regulating system according to the invention with further modules in schematic representation. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The regulating system shown in the drawing serves to provide a gas/air mixture for a gas burner (not shown). 
     With reference to FIG. 1 a gas flow can be fed to the burner (not shown) via a first line  10 . A gas-regulating valve  11  and two gas safety valves  12 ,  13  are assigned to the first line  10  carrying the gas flow. The gas-regulating valve  11  and the gas safety valves  12 ,  13  may be of any desired design. The construction and mode of operation of gas safety valves and gas-regulating valves are sufficiently known from the prior art. 
     Furthermore, a combustion-air flow can be fed to the burner (not shown) via a second line  14 . The combustion-air flow is produced by a fan  15 , the rotational speed of which is determined by a motor  16  assigned to the fan  15 . 
     A restrictor or choke point  17  is arranged inside the second line  14  carrying the combustion-air flow. In the region downstream of the choke point  17 , the first line  10  carrying the gas flow opens into the second line  14  carrying the air flow. In this region, the first line  10  carrying the gas flow is terminated by gas nozzle  18 . 
     A sensor  19  is arranged between the first line  10  carrying the gas flow and the second line  14  carrying the combustion-air flow. The sensor  19  is connected by a first measuring point  20  to the first line  10  carrying the gas flow, namely upstream of the gas nozzle  18  in the direction of flow of the gas. Furthermore, the sensor  19  is connected by a second measuring point  21  to the second line  14  carrying the combustion-air flow, namely upstream of the choke point  17  in the direction of flow of the combustion air. 
     The sensor  19  is designed as a differential-pressure sensor, in particular as a flow-rate meter or anemometer. The pressure difference between the gas pressure and the combustion-air pressure can therefore be determined by means of the sensor  19 . 
     If the gas pressure matches the combustion air, the flow through the sensor  19  designed as flow-rate meter or anemometer is equal to zero. If the combustion-air pressure is higher than the gas pressure, a flow from the second measuring point  21  in the direction of the first measuring point  20  can be detected. On the other hand, if the combustion-air pressure is lower than the gas pressure, a flow from the first measuring point  20  in the direction of the second measuring point  21  can be detected by the sensor  19 . The pressure ratios of gas pressure and combustion-air pressure can therefore be determined by the sensor  19  from the rate of flow through the sensor  19  and from the direction of flow. 
     Depending on these pressure ratios, the sensor  19  generates an electrical or electronic signal  22 . This electrical or electronic signal  22  is fed to a control unit or regulating unit  23 , which generates a regulating signal  24  for an actuator  25  of the gas-regulating valve  11 . 
     To insure a variable transmission ratio between gas pressure and combustion-air pressure or gas flow and combustion-air flow, the electrical or electronic signal  22  of the sensor  19  is balanced with an auxiliary signal  27  in a summing device  26 , specifically before the signal  22  is fed to the regulating unit  23 . The output signal  30  of the summing device  26  is therefore fed as input signal to the regulating unit  23 , the output signal  30  being an additive superimposition of the signals  22 ,  27 . 
     The auxiliary signal  27  is a signal which functionally depends on a rotational speed of the fan  15 . The auxiliary signal  27  is obtained in an evaluating device  28  from a rotational-speed signal  29  of the fan  15  or of the motor  16  of the fan  15 . Since the auxiliary signal  27  functionally depends on the rotational speed of the fan  15 , it directly follows that the auxiliary signal  27  depends on the combustion-air flow or combustion-air pressure. 
     Unlike the exemplary embodiment shown, it is possible to generate the auxiliary signal  27  in another way. Thus it is not absolutely necessary for the auxiliary signal  27  to be determined from the rotational speed of the fan. It is also conceivable to provide an additional sensor (not shown) for determining the combustion-air flow and thus for generating the auxiliary signal  27 . 
     To provide a gas/air mixture with a variable transmission ratio between gas pressure and combustion-air pressure, the procedure with the regulating system according to the invention is therefore as follows: 
     An electrical or electronic signal  22  which corresponds to the pressure difference between the gas pressure and the combustion-air pressure is determined by means of the sensor  19 . This electrical or electronic signal  22  is balanced with an auxiliary signal  27 . To this end, the electrical or electronic signal  22  and the auxiliary signal  27  are added. The auxiliary signal  27  depends on the combustion-air flow, in particular on the rotational speed of the fan  15 . The output signal  30 , determined from the signals  22 ,  27 , of the summing device  26  is fed to a regulating unit  23 , which generates a regulating signal  24  for the actuator  25  of the gas-regulating valve  11 . In this case, the regulating signal  24  is determined in such a way that the regulating unit  23  changes the gas flow to the effect that the input signal for the regulating unit  23 , that is the signal  30  determined from the signals  22 ,  27 , assumes a value of zero. 
     A factor which determines the transmission ratio between gas flow and combustion-air flow can be determined in the evaluating device  28 . This factor is a multiplication factor. The higher this multiplication factor is, the higher is the transmission ratio. The transmission ratio can be varied by varying the multiplication factor. 
     List of Designations 
       10  Line 
       11  Gas-regulating valve 
       12  Gas safety valve 
       13  Gas safety valve 
       14  Line 
       15  Fan 
       16  Motor 
       17  Choke point 
       18  Gas nozzle 
       19  Sensor 
       20  Measuring point 
       21  Measuring point 
       22  Signal 
       23  Regulating unit 
       24  Regulating signal 
       25  Actuator 
       26  Summing device 
       27  Auxiliary signal 
       28  Evaluating device 
       29  Rotational-speed signal 
       30  Out put signal 
     The preceding has described my invention.