JPH0221483B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention continuously varies the combustion output according to the load, and the ratio of the amount of combustion air (hereinafter simply referred to as air amount) to the amount of gas (hereinafter referred to as air-fuel ratio) The present invention relates to a gas combustion control device used particularly in household combustion equipment to maintain combustion stability and high efficiency by keeping the temperature approximately constant.

Configuration of conventional example and its problems As a conventional gas combustion control device of this type, the first
Pressure equalization valve method (or zero governor method) shown in the figure
is well known. That is, the air sent by the blower 1 passes through the air throttle 2 to the mixing unit 3, and the gas passes through the pressure equalizing valve 4 and the gas throttle 5 to the mixing unit 3, where the air and gas are mixed and guided to the burner 6. Burn.

The pressure upstream of the air throttle 2 is introduced into the back pressure chamber 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 and the air volume is
Q _A , the pressure upstream of the gas throttle 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, gas restriction, and gas type, respectively).

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, since the pressure equalizing valve 4 mechanically moves the valve 9 in response to the differential pressure between P _A and P _G at the diaphragm 8, the stiffness of the diaphragm, the change in the effective area of the diaphragm due to displacement, 9
A pressure adjustment error ΔP _G will always occur due to the influence of the equalization valve inlet pressure. That is, P _G = P _A + ΔP _G
So, 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, in order to increase the combustion output adjustment ratio while keeping the air-fuel ratio error within a certain range, the value of P _A - P _M must be increased or ΔP _G must be decreased.

On the other hand, for household gas combustion equipment used for hot water supply or space heating, the combustion output adjustment ratio is 1/5.
About 1/10 is necessary. For that reason, P _A −
Increasing P _M not only makes the blower extremely large, but also makes P _A higher than the gas supply pressure, which is impossible when using city gas, etc., where the supply pressure is low. Even if this is achieved with gas other than city gas, for some reason during combustion, for example, if you are using a gas cylinder, the propane gas is about to run out while you are using it, or if there are strong winds such as during a typhoon. When the exhaust resistance of combustion equipment increases and the so-called gas pressure decreases, such as when it becomes difficult for combustion gas to flow, the amount of combustion gas may not be able to follow the amount of supplied air. In such cases, conventional mechanical pressure equalization valves limit the upper limit of the amount of supplied air to ensure that the air-fuel ratio balance does not deviate from the stable combustion range, depending on the magnitude of the combustion output. There was a problem that a good combustion condition could not be obtained because there was no means to do so. Furthermore, there are limits to reducing the pressure adjustment error ΔP _G , which is determined by the limits of the mechanical accuracy of the pressure equalization valve, due to the size of the pressure equalization valve, and there are effects of aging and difficulty in adjustment, making it difficult for household combustion equipment to reduce. was difficult to apply.

Purpose of the Invention The present invention solves the above-mentioned conventional problems, and has a large combustion output adjustment ratio without increasing the size of the blower or valve device, and has excellent air-fuel ratio stability even in the unlikely event of a drop in gas pressure. The object of the present invention is to provide a gas combustion control device that has the following characteristics.

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 according to 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 electrical signal according to the pressure difference and detects the temperature of the heated object, and a temperature setting device; a temperature control circuit that amplifies and calculates the difference between the signal of the temperature detector and the signal of the temperature setting device; and a temperature control circuit that amplifies and calculates the difference between the signal of the temperature sensor and the signal of the temperature setting device; A differential pressure comparator is provided to generate a differential pressure, and the output of the temperature control circuit controls an air amount adjusting means provided upstream of the air throttle, and the air amount adjusting means provided upstream of the gas throttle is controlled according to the output of the differential pressure sensor. In addition to controlling the gas amount adjusting means, when the output of the differential pressure comparator is generated,
The air amount adjusting means is configured to be controlled in accordance with a signal from a differential pressure sensor in priority to the temperature adjusting circuit.

With this configuration, it is equipped with a differential pressure sensor that detects the differential pressure upstream of the two throttles on the air side and gas side, and adjusts the gas amount according to the output of this differential pressure sensor so that the air-fuel ratio is constant. If the output of the differential pressure sensor becomes larger than the comparison reference value corresponding to the air amount, the air amount is controlled by the air amount adjusting means in priority to the temperature control circuit. Even when the gas pressure decreases, the air-fuel ratio is corrected and controlled, so a stable combustion state is always possible.

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, 7G is a gas amount adjusting means such as a gas pressure proportional control valve (hereinafter 7G is referred to as a gas pressure proportional control valve), 7A is an air amount adjusting means such as a damper, and 8 is a heat exchanger. Exchanger, 9 is hot water pipe, 1
0 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 one blower according to the signal from the temperature detector 10, 13 temperature detection circuits, 14 temperature setting devices, 15 temperature adjustment circuits, and 16 air volume adjustment means circuits are provided. It also consists of 17 differential pressure sensor detection circuits and 18 air-fuel ratio adjustment circuits in order to control the 7G gas pressure proportional control valve according to the output of the 4 differential pressure sensors. A differential pressure comparator 19 is used as a means for controlling the air-fuel ratio so that it does not exceed an allowable range when the air-fuel ratio decreases.

In Figure 3 A, the straight lines A, B', B, and C are the excess air ratio (m) when there is no abnormal gas pressure drop.
) constant (m=1.2 in the case of this first embodiment)
The air-fuel ratio control characteristics of

The straight line of BDE and the straight lines of B', D', and E' indicate that the air volume changes from A ₁ to A ₂ when an abnormal gas pressure drop occurs.
Even if the amount of gas increases from A′ ₁ to A′ ₂ ,
It shows a state in which it does not increase more than G _L or G′ _L.

The straight line connecting O, D', and D indicates that the excess air ratio m is greater than m=1.2 (in this embodiment, m=
1.6) and shows the air-fuel ratio control characteristics near the limit of the stable combustion region determined from the combustion characteristics of the burner. Conversely, points D and D' indicate points where the air-fuel ratio remains the same even when the combustion output changes.

In addition, in such a case, B and C in Figure 3
It shows the status 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.

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, when the burner 6 is already ignited and the amount of hot water flowing out from the hot water tap 9 is W _MIN in FIG. 4, it is controlled at point A in FIG. 3. shall be. (i.e.
This state is the minimum state of the combustion variable range, and the air amount is controlled at A _MIN and the gas amount is controlled at G _MIN .)
If you leave the temperature setting device 14 at T _MAX in this state and increase the amount of hot water, the temperature of the hot water will temporarily drop.
A temperature deviation signal ΔT is generated between the temperature detection circuit of 1 and the temperature setter of 14. This temperature deviation signal ΔT is processed by a temperature control circuit (15) and an air volume control means circuit (16) to control the air volume from one blower to be increased. In such a situation where the amount of air changes from moment to moment, the differential pressure sensor (4)
Since differential pressure is generated, 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 acting on the differential pressure sensor 4 is reduced to 7G so that the differential pressure acting on the differential pressure sensor 4 becomes zero. control to increase the flow rate from the gas pressure proportional control valve.

At this time, in FIG. 3A, the air-fuel ratio is kept constant, that is, the control is carried out along a straight line from direction A to direction C.

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 the hot water output amount is gradually increased from this state to W _MAX , the hot water temperature will change from f to f' while maintaining T _MIN , just as in the case where it was controlled from e to e'. controlled up to.

This state can be explained based on Figure 3 A.
Along the AC line, the air-fuel ratio is controlled to be constant until the maximum rated value C is reached, that is, the air amount is A _MAX and the gas amount is G _MAX .

Conversely, if you reduce the hot water output or amount from a state of e', f' or between them, or lower the set temperature using the temperature setting device 14 from a state above the minimum control temperature T _MIN , the blower 1 will Since the air amount is controlled to decrease and the pressure at P _A in FIG. 2 acts in the direction of decreasing, a differential pressure is generated in the differential pressure 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 gas types used in household gas combustion appliances include city gas, natural gas, propane gas, and the like. The supply gas pressure for each of these gases is regulated; for example, in the case of city gas, the standard gas pressure is 100mmH ₂ O,
The minimum gas pressure is 50mmH ₂ O and the maximum gas pressure is 200mmH 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, if the supply gas pressure drops abnormally for some reason when the combustion state, hot water supply state, and air-fuel ratio are intermediate on the AC line in Figure 3, if you try to increase the combustion output, the air The quantity Q _A is A ₁ ,
A ₂ and A ₃ increase, but the gas amount does not increase from 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 ABCE. Become. In other words, the amount of gas becomes insufficient and the air-fuel ratio increases.

On the other hand, in such a state, if the combustion output is varied, the output of the differential pressure sensor 4 is controlled to be zero because it is controlled at a predetermined air-fuel ratio 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 apparently 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 air amount further increases from point D,
Output along lines _a3 to _a4 is generated. At this time DE
On the other hand, if the air-fuel ratio attempts to increase further along the line _of
Comparison reference value a ₃ whose output is determined by the air amount A ₂
, the differential pressure comparator 19 generates an output along line b ₃ to b ₄ . In such a case, the output of the pressure sensor 4 or the output of the differential pressure comparator 19 is used to prioritize the temperature control circuit 15 and reduce the rotational speed of the blower 1, that is, to return it from point E to point D. It is something to control.

In addition, if the gas pressure decreases in the lower combustion range than in the above case and the gas amount does not increase from G' _L in Figure 3 A, the air-fuel ratio control characteristic will be changed to B in the same way. Bend from point ′, A, B′, D′,
It tries to be controlled like E′, but in this case also
Since point E' is in the direction of increasing more than the limit value m = 1.6 of _{the allowable air-fuel ratio, the comparison reference value a' corresponding to the air amount A' 2 is} exceeded. The output of the comparator 19 gives priority to the temperature control circuit 15 and moves from point E' to point D', that is, m
= 1.6. In addition,
In the example shown in Fig. 3, both the high combustion region and the low combustion region are controlled at m = 1.6 (constant value) or less. It is also possible to control the high combustion range to be smaller than the low combustion range. (In this case,
The comparison reference value is not directly proportional to the air amount Q _A. ) In addition to a drop in the supply pressure itself, cases where the gas pressure drops abnormally include the following: 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 supply pressure decreases due to the force of the gas combustion equipment, if the output of the differential pressure sensor 4 exceeds the comparison reference value determined by the amount of air, the differential pressure comparator 19
By giving the blower 1 an output that reduces the amount of air by the output of , it becomes possible to perform control such that the upper limit of the allowable air-fuel ratio, that is, m=1.6, is not exceeded over the entire variable combustion range. Therefore, carbon monoxide will not be generated in excess of the allowable limit, abnormal combustion noise will not be generated, or the combustion flame will not blow out.

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. Instead, it can be controlled by reducing the differential pressure of the differential pressure sensor, making it possible to downsize blowers and apply it to household combustion equipment when the supply gas pressure, such as city gas, is low. It is something.

Additionally, by installing a differential pressure comparator that generates an output when the output of the differential pressure sensor is equal to or higher than the comparison reference value corresponding to the air amount, it can be used even if the supply gas pressure decreases or strong winds act on the combustion equipment. However, by controlling the air amount adjusting means with priority over the gas amount adjusting means, it is possible to control the air-fuel ratio so that the upper limit of the allowable air-fuel ratio is not exceeded over the entire variable combustion 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, 7G...Gas amount adjustment means, 7A...Air amount adjustment means, 10...Temperature detector, 11...Gas side passage, 12...Air side passage, 14...Temperature setting device, 15...Temperature Adjustment circuit, 19... Differential pressure comparator.

Claims (1)

[Claims] 1 A blower for supplying combustion air, an air amount adjusting means, and an air restrictor are provided in the air side passage, and a gas amount adjusting means and a gas restrictor are provided in the gas side passage, and the air restrictor and the gas restrictor are provided in the gas side passage. It is equipped with a mixing section that mixes air and gas by merging downstream, and 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 is heated by a burner. a temperature detector for detecting the temperature of the heated body, a temperature setting device for setting the outlet temperature of the heated body, and a temperature for amplifying the difference between the signal of the temperature detector and the signal of the temperature setting device. The absolute value of the output of the differential pressure sensor caused by excess air when the gas pressure decreases is set in advance as a comparison reference value in the adjustment circuit and in a form corresponding to the amount of air that affects the combustion characteristics of the burner, and the absolute value of the output of the differential pressure sensor is set in advance as a comparison reference value in a form that corresponds to the amount of air that affects the combustion characteristics of the burner, and the absolute value of the output of the differential pressure sensor that occurs due to excess air when the gas pressure decreases is set in advance as a comparison reference value in a form that corresponds to the amount of air that affects the combustion characteristics of the burner. and a differential pressure comparator that generates an output when and a gas combustion control device that controls the air amount adjusting means in accordance with the output of the differential pressure sensor with priority over the temperature adjusting circuit when the output of the differential pressure comparator is generated.