JPS649529B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention continuously varies the combustion amount according to the load, and also changes the ratio of the combustion amount air amount (hereinafter simply referred to as the air amount) to the gas amount (hereinafter referred to as the air-fuel ratio). This invention relates to a gas combustion control device used particularly in household appliances to maintain combustion stability and high efficiency by keeping the temperature constant (as described above) almost constant.

Configuration of Conventional Example and Its Problems The pressure equalization valve system (or zero governor system) shown in FIG. 1 is well known as a conventional gas combustion control device of this type. That is, the air sent by the blower 1 passes through the air throttle 2 to the mixing section 3, and the gas passes through the pressure equalizing valve 4 and the gas throttle 5 to the mixing section 3, where the air and gas are mixed and then led to the burner 6 where they are combusted. do.

The pressure upstream of the air throttle 2 is introduced into the back pressure air 7 of the pressure equalizing valve 4, and the pressure equalizing valve 4 automatically adjusts the pressure at the outlet of the pressure equalizing valve to be equal to the pressure in the back pressure chamber 7. Here, the pressure upstream of the air restriction is P _A , the air amount is Q _A , the pressure upstream of the gas restriction is P _G , the gas amount is Q _G ,
If the pressure in the mixing section is P _M , the air-fuel ratio Q _A /Q _G is (K ₁ and K ₂ are constants determined by the air restriction and gas restriction, respectively.) There is the following relationship.

If the pressure equalizing valve 4 can ideally adjust P _G = P _A Therefore, even if Q _A is changed, the air-fuel ratio should always remain constant. However, the pressure equalization valve has a diaphragm 8
Since the valve 9 is mechanically moved in response to the differential pressure between P _A and P _G , the rigidity of the diaphragm, the change in the effective area of the diaphragm due to displacement, the influence of the equalization valve inlet pressure on the valve 9, etc. Therefore, a pressure adjustment error ΔP _G is sure to occur. In other words, since P _G = P _A + ΔP _G , Therefore, the fluctuation of air-fuel ratio due to pressure adjustment error is P _A
−P The smaller the value of _M , the larger it becomes.

Therefore, if you try to increase the combustion amount control ratio while keeping the air-fuel ratio error within a certain range,
Either the value of P _A − P _M had to be increased or ΔP _G had to be decreased.

On the other hand, when used as a household gas combustor for hot water supply or space heating, the combustion amount adjustment ratio is 1/5 to 1/1.
Approximately 0 is required. For this reason, increasing P _A - P _M not only makes the blower extremely large, but also makes it impossible to achieve this because P _A becomes higher than the gas supply pressure, such as with city gas where the supply pressure is low. Further, even if the method is realized using a gas other than city gas, there is a problem in that when the gas pressure decreases, the accuracy of air-fuel ratio control deteriorates significantly, making it impossible to obtain a good combustion state. Furthermore, there is a limit to reducing ΔP _G due to the size of the pressure equalizing valve, and it is difficult to apply to household combustion equipment due to the effects of aging and difficulty in adjustment.

Purpose of the invention The present invention solves such conventional problems,
It is an object of the present invention to provide a gas combustion control device that has a large combustion amount control ratio and excellent air-fuel ratio stability without increasing the size of a blower or a valve device.

Structure of the Invention In order to achieve this object, the present invention provides an air constriction and a gas constriction that generate pressure loss in accordance with the respective flow rates in the air side passage and the gas side passage, and merges the downstream sides thereof to create a common pressure. and a temperature detector that guides the pressure upstream of the two throttles to a differential pressure sensor that generates an electric signal according to the pressure difference and detects the temperature of the heated object, and a temperature setting device; It has a temperature adjustment circuit that amplifies and calculates the difference between the signal of the temperature detector and the signal of the temperature setting device, and a differential pressure comparator that generates an output when the absolute value of the output of the differential pressure sensor is equal to or higher than a certain value. , controlling the air amount adjusting means provided upstream of the air throttle with the output of the temperature adjusting circuit, controlling the gas amount adjusting means provided upstream of the gas restricting according to the output of the differential pressure sensor, and When an output from the differential pressure comparator is generated, the air amount adjusting means is controlled in accordance with the signal from the differential pressure sensor with priority over the temperature adjusting circuit.

With this configuration, a differential pressure sensor that electrically acts on the means for detecting the differential pressure upstream of the two throttles on the air side and the gas side is provided, and the air-fuel ratio is kept constant according to the output of this differential pressure sensor. When the output of the differential pressure sensor becomes larger than a predetermined constant value, the air amount is controlled by the air amount adjusting means in priority to the temperature control circuit. Even if the gas pressure decreases, the air-fuel ratio is corrected and a stable combustion condition is maintained at all times.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 2 to 4. In FIG. 2, parts that are the same as those in FIG. 1 are given the same numbers.

In FIG. 2, 4 is a differential pressure sensor, 7 is a gas amount adjusting means such as a gas pressure proportional control valve (hereinafter 7 is referred to as a gas pressure proportional control valve), 8 is a heat exchanger, 9 is a hot water outlet pipe, and 10 is a It is a temperature detector such as a thermistor installed on the tapping pipe, and 11 and 12 are a gas side passage and an air side passage, respectively. As an electrical control system, in order to control the blower 1 according to the signal from the temperature detector 10, 13 temperature detection circuits, 14 temperature setters, 15 temperature adjustment circuits, 1
It consists of an air amount adjusting means such as a rotational speed adjusting circuit (6) (a damper may be provided downstream of the blower 1 and a means for changing the rotation angle of this damper), and also according to the output of the differential pressure sensor (4). Consists of a differential pressure sensor detection circuit (17) and an air-fuel ratio adjustment circuit (18) to control the gas pressure proportional control valve (7), and further controls the air-fuel ratio so that it does not exceed the allowable range when the gas pressure decreases. A differential pressure comparator 19 is used as a means for this purpose.

In Figure 3 A, the straight line ABC shows the air-fuel ratio control characteristics when there is no abnormal gas pressure drop, etc.
The straight line of BDE indicates a state in which the gas amount does not increase more than G _L even if the air amount increases when an abnormal gas pressure drop occurs. 3B and 3C show the state of the output of the differential pressure comparator and the output of the differential pressure sensor that occur in response to the amount of air in such a case.

FIG. 4 shows a hot water supply capacity characteristic diagram when the present invention is applied to a gas hot water supply device as an embodiment of the present invention.

In the above configuration, the burner 6 is already ignited, and the amount of hot water flowing out from the hot water tap 9 reaches the fourth point.
Assume that control is being performed at point A in FIG. 3 exactly when W _MIN in the figure. (In other words, this state is the minimum state of the control range, and the air amount is controlled to A _MIN and the gas amount is controlled to G _MIN .)
If the temperature setting device 14 is left as it is in such a state and the amount of hot water is increased, the temperature of the hot water will temporarily drop, so that the temperature setting device 14 is A temperature deviation signal ΔT is generated. This temperature deviation signal ΔT is processed by a temperature control circuit 15 and a rotation speed control circuit 16 to control the air amount from the blower 1 to increase. In such a state where the amount of air changes every moment, a differential pressure is generated in the differential pressure sensor 4, so this differential pressure is electrically processed by the differential pressure sensor detection circuit 17 and the air-fuel ratio adjustment circuit 18, and the differential pressure is 7 so that the differential pressure acting on the pressure sensor 4 becomes zero.
control to increase the flow rate from the gas pressure proportional control valve.

At this time, in Figure 3 A, from A to B (or C
direction), the control will be along a straight line.

Further, in FIG. 4, the outlet temperature is controlled to be approximately constant T _MAX on the line from e to e'.

Furthermore, when the amount of hot water is reduced to W' _MIN and the temperature setting device 14 is set to T _MIN , the state f in FIG. 4 is maintained. Then, if you gradually increase the amount of hot water from this state to W _MAX ,
As in the above case where e is controlled from e′,
The tapping temperature is controlled from f to f' while maintaining approximately T _MIN .

This state can be explained based on Figure 3 A.
The air-fuel ratio is controlled at a constant value along the line AC from the state halfway between and C to the state of the maximum rated value C, that is, the state where the air amount is A _MAX and the gas amount is G _MAX .

On the other hand, if you reduce the hot water output from a state of e', f' or between them, or lower the set temperature using the temperature setting device 14 from a state of the minimum control temperature T _MIN or higher, contrary to the above, The blower 1 is controlled to reduce the amount of air, which acts in the direction of decreasing the pressure at P _A in FIG. 2, so that an apparent pressure difference is generated in the pressure difference sensor 4. Therefore, the gas pressure proportional control valve 7 is automatically controlled to reduce the gas amount so that this differential pressure becomes zero.

The above is an explanation of the operation in a normal control state where there is no drop in gas pressure. As is well known, the types of gases used in household gas combustion appliances are city gas,
Typical examples include natural gas and propane gas. The supply gas pressure for each of these gases is specified,
For example, in the case of city gas, the standard gas pressure is 100mm.
_H2O , minimum gas pressure _50mmH2O , maximum gas pressure 200mm
It is specified as H ₂ O.

It goes without saying that the combustion equipment is designed so that the combustion characteristics, hot water supply capacity, etc. specified for the combustion equipment are fully satisfied even at the lowest gas pressure.

However, when the combustion state, hot water supply state, and air-fuel ratio are intermediate between AB in Fig. 3, and the supply gas pressure is abnormally low, an attempt is made to increase the combustion output as described above. Then, the air amount Q _A is A ₁ ,
A ₂ and A ₃ increase, but the gas amount does not increase more than G _L at point B, so the air-fuel ratio control characteristic bends from point B without following the ABC line, and is controlled like ABDE. . In other words, the amount of gas becomes insufficient and the air-fuel ratio increases. In other words, point D is the limit point of the allowable air-fuel ratio determined from combustion characteristics and the like.

On the other hand, in such a state, if the combustion state is varied, the output of the differential pressure sensor 4 is controlled to be zero because the air-fuel ratio is controlled at a predetermined value on the AB line, so a ₁ ~ The output from the differential pressure comparator 19 is controlled along the line a ₂ and along the line b ₁ to b ₂ (that is, the output is zero).

Then, when the gas pressure enters the control range B to D where it is decreasing, the differential pressure sensor 4 generates an output along line _a2 to _a3 , and when the combustion output further increases from point D, _a3
~a Output along ₄ lines is generated. At this time, the air-fuel ratio tends to increase further along the DE line, but on the other hand, beyond point D, that is, the air amount increases.
When attempting to increase from A ₂ , the output of the differential pressure sensor 4 exceeds the constant value a ₃ , so the differential pressure comparator 19
From this, an output along b ₃ to _{b 4} is generated. In such a case, the output of the differential pressure comparator 19 is used to control the temperature control circuit 15 so as to reduce the number of revolutions of the blower 1, that is, to bring it back from point E to point D.

In addition to a drop in the supply pressure itself, there are other cases where the gas pressure drops abnormally: That is, if the pressure in the exhaust system of the combustion equipment increases due to strong winds or the like, the amount of gas decreases, which is the same as when the supply gas pressure decreases.

In this way, when the gas supply pressure of the gas combustion equipment decreases and the output of the differential pressure sensor 4 exceeds a certain value, the output of the differential pressure comparator 19 causes the blower 1 to receive an output that reduces the amount of air. By giving this, it becomes possible to control the air-fuel ratio so that the variation falls within the permissible range. Therefore, deterioration of combustion characteristics such as generation of carbon monoxide and soot is avoided.

Effects of the Invention As described above, the gas combustion control device of the present invention provides the following effects.

An air throttle and a gas throttle are installed on both the air and gas side passages, and the downstream sides of these are merged to create a common pressure, and the pressure upstream of the two throttles is detected by a differential pressure sensor and corresponds to the combustion output. Since the air-fuel ratio is controlled to be constant using the output of the differential pressure sensor generated by the engine, pressure adjustment errors are reduced and combustion control accuracy is improved compared to conventional mechanical pressure equalization valve control. In addition, since the differential pressure of the differential pressure sensor can be controlled by reducing it, blowers, etc. can be made smaller, and it can be applied to household combustion equipment when the supply gas pressure, such as city gas, is low. It is something to do.

In addition, by equipping a differential pressure comparator that generates an output when the output of the differential pressure sensor is above a certain value, the gas amount can be adjusted when the supplied gas pressure decreases or strong winds act on the combustion equipment. By giving priority to controlling the air volume adjustment means,
Air-fuel ratio fluctuations can be controlled to within a certain range. Therefore, the combustion state can be stabilized at all times, making it possible to realize highly safe combustion equipment.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the configuration of a conventional gas combustion control device, Fig. 2 is an explanatory diagram of the configuration and blocks of an embodiment of the gas combustion control device of the present invention, and Fig. 3 is an explanatory diagram of the above-mentioned embodiment of the gas combustion control device of the present invention. Control operation explanatory diagram, 4th
The figure is a hot water supply capacity characteristic diagram of the gas hot water supply equipment in the above-described embodiment of the present invention. 1...Blower, 2...Air throttle, 3...Mixing section, 4...Differential pressure sensor, 5...Gas throttle, 6...
Burner, 7...Gas amount adjustment means, 10...Temperature detector, 11...Gas side passage, 12...Air side passage, 14...Temperature setter, 15...Temperature adjustment circuit, 16...Air amount Adjustment means, 19...differential pressure comparator.

Claims (1)

[Claims] 1 The air side passage is provided with a blower for supplying combustion air, an air amount adjustment means, and an air throttle, and the gas side passage is provided with a gas amount adjustment means and a gas restriction, and the downstream side of the air restriction and the gas restriction is installed. a mixing unit that mixes air and gas; a differential pressure sensor that generates an electric signal corresponding to the pressure difference between the upstream of the air throttle and the upstream of the gas throttle; and a heated target heated by a burner. A temperature detector that detects body temperature;
a temperature setting device that sets the outlet temperature of the heated object; a temperature adjustment circuit that amplifies and calculates the difference between the signal of the temperature detector and the signal of the temperature setting device; It has a differential pressure comparator that generates an output when the temperature is equal to or greater than a value, the air amount adjusting means is controlled by the output from the temperature adjusting circuit, and the gas amount adjusting means is controlled according to the output of the differential pressure sensor. and a gas combustion control device that controls the air amount adjusting means in accordance with the signal of the differential pressure sensor with priority over the temperature adjusting circuit when the output of the differential pressure comparator is generated.