GB2187309A

GB2187309A - Burner control

Info

Publication number: GB2187309A
Application number: GB08703375A
Authority: GB
Inventors: Shigeo Naruse; Shinji Kuroda
Original assignee: Rinnai Corp
Current assignee: Rinnai Corp
Priority date: 1986-02-22
Filing date: 1987-02-13
Publication date: 1987-09-03
Also published as: KR910002740B1; FR2594938B1; DE3705437A1; GB2187309B; FR2594938A1; DE3705437C2; JPS62276328A; GB8703375D0; KR870008152A

Abstract

A burner control apparatus e.g. for a gas water heater (1) comprises a fan (6) for supplying combustion air to the burner (5), a control circuit (14) for outputting a command signal to the fan (6) corresponding to a temperature difference between a load temperature of the burner (5) and a set temperature thereof, and a feedback circuit responsive to fan speed or to the volume, pressure or speed of combustion air supplied by the fan (6). The fan command signal may also be responsive to the temperature and quantity of the water supply as measured at (26), (27). <IMAGE>

Description

SPECIFICATION Burning control apparatus This invention relates to a burning control apparatus for controlling driving of a fan for supplying combustion air to a burner.

A burning control apparatus has been proposed that comprises a fan for supplying combustion air to a burner, a temperature control circuit for outputting a signal corresponding to a temperature difference between a load temperature of the burner and a set temperature thereof, and a fan driving circuit for being inputted with the output signal from the temperature control circuit and that serves to change the quantity of combustion air supplied by the fan in accordance with the inputted signal.In this apparatus the driving of the fan can be controlled in accordance with the temperature difference just mentioned but there is the inconvenience that this control may not always be effected accurately on some occasions. Nameiy, for instance, on such an occasion that an air intake passage or a gas exhaust passage has introduced thereinto foreign matters such as dust or the like, and as a result resistance to gas flow is increased, there is brought about such a drawback that the fan cannot be operated so accurately as to correspond to the input signal. In other words, there is a possibility that the quantity of combustion air supplied by the fan to the burner does not correspond accurately to the input signal but may instead be more or less decreased.

According to the present invention there is provided a burning control apparatus comprising a fan for supplying combustion air to a burner, a temperature control circuit for outputting a signal corresponding to a temperature difference between a load temperature of the burner and a set temperature thereof, a fan driving circuit for being inputted with an output signal from the temperature control circuit and serving to change the amount of combustion air supplied by the fan in accordance with the inputted signal so that the driving of the fan is controlled in accordance with the temperature difference, a detecting means for detecting a parameter that determines the amount of air supplied by the fan or that is determined by the amount of air supplied by the fan, and a feedback circuit for being inputted with the detection signal from the detecting means so that a compensation signal generated at the feedback circuit isgiven to the fan driving circuit. In this appera- tus, by the provision of the detecting means for detecting the driving condition of the fan, and the feedback circuit that is inputted with the detection signal of the detecting means so that a compensation signal generated at the feedback circuit can be given to the fan driving circuit, the fan can be controlled to be in such a driving condition that always substantially corresponds to the temperature difference. The apparatus is therefore particularly suited to combustion apparatus of high load combustion type wherein the quantity of combustion air supply is required to be controlled at a high accuracy.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a sectional side view of a gas water heater, Figure 2 is a block diagram of an important portion of the heater of Fig. 1, and Figure 3 is a circuit diagram of the heater.

In Fig. 1, numeral 1 denotes a main body of the gas water heater which has in its lower portion air inlet openings 2 and at its upper portion an exhaust pipe 3. The main body 1 contains therein a burner casing 8 which in turn contains in its middle portion a heat exchanger 4 and a burner 5 for heating the heat exchanger 4; in its lower portion a fan 6 for supplying combustion air to the burner 5; and at its upper portion an exhaust opening 7 connected to the exhaust pipe 3. Water supplied from a water supply pipe 9 upstream of the heat exchanger 4 is heated in the heat exchanger and hot water thus obtained is discharged to a hot water discharging pipe 10 downstream of the heat exchanger 4. At the same time hot exhaust gases are discharged to the exterior through the exhaust pipe 3.

Further in Fig. 1, numeral 11 denotes a gas supply passage connected to the burner 5. An electromagnetic opening and closing valve 12 and an electromagnetic proportional control valve 13 are interposed in this gas supply passage 11 with the valve 12 upstream of the valve 13.

Referring also to Fig. 2, an increasing and decreasing control of the amount of air supplied to the burner 5 is carried out by a fan driving circuit 16 that receives signals from a temperature control circuit 15 in a control circuit 14.

In more detail, the temperature control circuit 15 is itself a known circuit. A signal corresponding to a temperature difference between the actual discharging hot water temperature, that is, the load temperature detected by a temperature sensitive element 17 provided in the hot water discharging pipe 10, and a set temperature in the temperature conrol circuit 1 5 is outputted from the temperature control circuit 15. This output signal is inputted to the fan driving circuit 16 so that electric power corresponding to a magnitude of the signal is supplied to an electric motor of the fan 6 and the rotational speed of the fan is thereby changed in accordance therewith.

As so far described, the construction is not significantly different from what has been previously proposed. In the present apparatus, however, there is provided a detecting means, associated with a detecting circuit 18 (Figs. 2 and 3) for detecting a driving condition of the fan 6, and a feedback circuit 19 that is inputted with a detection signal of the detecting means 18 so that a compensation signal generated at the feedback circuit 19 may be supplied to the fan driving circuit 16.

The details thereof are, for instance, as shown in Fig. 3. Namely, in the illustrated example, the detecting circuit 18 comprises a hall IC type rotation sensor 20 for detecting the rotational speed of the fan 6, and a conversion circuit 21 for converting a pulse signal from the sensor 20 into a corresponding voltage signal-for being outputted. The feedback circuit 19 comprises a comparator 22 for comparing between the output signal of the temperature control circuit 15, that is, a voltage signal corresponding to the temperature difference mentioned above, and a voltage signal outputted from the conversion circuit 21, and an operational amplifier 23 for outputting, as a compensation signal, a voltage signal corresponding to a difference signal obtained at the comparator 22.An improper driving condition of the fan 6 by the fan driving circuit 16 is so compensated by the compensation signal that the difference signal obtained at the comparator 22 may be removed.

In other words, it is possible by the compensation signal for the fan to obtain always such a driving condition that the rotational speed thereof corresponds exactly to the temperature difference.

Such a modification can be considered that, as shown by chain lines in Fig. 2, a calculation circuit 25 is interposed between the temperature control circuit 1 5 and the fan driving circuit 16, and respective signals from a water temperature sensor 26 and a water quantity sensor 27 which are provided in the water supply pipe 9 are arranged to be inputted thereto so that the output signal from the fan driving circuit 16 may be compensated in accordance with change of the supply water temperature or change of the quantity of water supplied.

In the illustrated example, the detection circuit 1 8 detects the rotational speed of the fan 6, but any other desired form of circuit could be utilised that detects the driving condition of the fan 6, such as a circuit detecting the volume of air blown by the fan 6, or the air speed, or the air pressure.

Operation of the apparatus is as follows: On such an occasion that the air inlet openings 2 or the gas exhaust pipe 3 have introduced thereinto a foreign matter such as dust, and thereby resistance to gas flow therethrough is increased such that the fan cannot maintain its driving condition corresponding accurately to the signal outputted from the fan driving circuit 16 that corresponds to the output signal of the temperature control circuit 15, the driving condition of the fan 6, for instance, the actual rotational speed of the fan 6, is detected by the detecting circuit 18 and based on the detection signal thereby obtained, the compensation signal is given from the feed back circuit 19 to the fan driving circuit 16, whereby the fan 6 is compensated for its improper driving and a predetermined proper driving operation of the fan is restored.

Thus a proper predetermined driving of the fan 6 can be always kept. In other words, in the present apparatus, by the provision of the detecting means for detecting the driving condition of the fan, and the feedback circuit that is inputted with the detection signal of the detecting means so that a compensation signal generated at the feedback circuit can be given to the fan driving circuit, the fan can be controlled to be in such a driving condition that always substantially corresponds to the temperature difference. The apparatus is therefore particularly suited to combustion apparatus of high load combustion type wherein the quantity of combustion air supply is required to be controlled at a high accuracy.

Claims

1. A burning control apparatus comprising a fan for supplying combustion air to a burner, a temperature control circuit for outputting a signal corresponding to a temperature difference between a load temperature of the burner and a set temperature thereof, a fan driving circuit for being inputted with an output signal from the temperature control circuit and serving to change the amount of combustion air supplied by the fan in accordance with the inputted signal so that the driving of the fan is controlled in accordance with the temperature difference, a detecting means for detecting a parameter that determines the amount of air supplied by the fan or that is determined by the amount of air supplied by the fan, and a feedback circuit for being inputted with the detection signal from the detecting means so that a compensation signal generated at the feedback circuit is given to the fan driving circuit.

2. A burning control apparatus as claimed in claim 1, wherein the feedback circuit comprises a comparator for comparing between the output signal of the temperature control circuit and the output signal of the detecting circuit, and an operational amplifier for generating the compensation signal corresponding to a difference signal obtained at the comparator so that the output of the operational amplifier can be introduced to the fan driving circuit.

3. A burning control apparatus substantially as hereinbefore described with reference to the accompanying drawings.