JPS59212621A - Gas combustion controller - Google Patents

Abstract

PURPOSE:To increase a combustion amount regulating ratio and to stabilize an air-fuel ratio, by a method wherein either an air amount regulating means or gas amount regulating means is controlled dependently on the load of a burner, and the other is controlled according to a difference between two output signals from a differential pressure signal discriminating circuit. CONSTITUTION:When pressure switching valves 14a and 14b are borught into a first state, PG and PA are applied in pressure guiding holes 13 and 15 respectively, of a differential pressure sensor 12. When the pressure switching valves 14a and 14b are brought into a second state, PA and PG are applied in the pressure guiding holes 13 and 15, respectively, of the differential pressure sensor. Namely, the output of the differential pressure sensor alternately produces an output, corresponding to (PA-PG), and an output corresponding to -(PA-PG) having reverse polarity thereto. A gas pressure proportional valve 10 is controlled by feedback so that an input signal (PA-PG) is brought to zero by means of an air fuel ratio regulating circuit 19 including an integrating computing element. This causes maintaining of PG=PA without being effected by the error of a differential pressure sensor 12 and a differential pressure sensor detecting circuit 16.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention continuously varies the amount of combustion depending on the load, and also changes 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 amount). This invention relates to a high-load gas combustion control device used particularly in household appliances, which maintains a nearly constant fuel ratio (fuel ratio) and achieves combustion stability and high efficiency.

Configuration of conventional example and its problems This is the first conventional high-load gas combustion 17 control device of this type.
The pressure equalizing valve system (or zero governor one-way system) shown in the figure is well known.

In the figure, air sent by a blower 1 is guided to a mixing section 3 via an air throttle 2, while gas is passed through a pressure equalizing valve 4. The mixed gas is led to the mixing section 3 through the gas throttle 5, and the mixed gas is led to the bar 6 where it is combusted.

Here, the pressure PA of the second flow of the air restrictor 2 is introduced into the back pressure chamber 7 of the pressure equalization valve 4, and the pressure equalization valve 4 has an outlet pressure pG
is automatically adjusted so that it becomes equal to the pressure in the back pressure chamber 7. When the air amount is QA, the gas amount is QG, and the pressure of the mixing section is PM, the air-fuel ratio QA/QG has the following relationship.

QG K2
(K2 is the constant of air throttling and gas throttling, respectively) If it can be ideally adjusted to PG-PA using a pressure equalization valve, then Equation 1 will become as follows, and the air-fuel ratio should always be constant regardless of QA and QG.

However, the pressure equalizing valve 4 receives the pressure difference between PG and PA at the diaphragm 8, and uses the force generated by the pressure difference to move the valve 9 to adjust the outlet pressure PG.
In addition to this, there is always a steady deviation between the two, and the pressure adjustment error Δ is also caused by the effects of the diaphragm's rigidity, changes in the effective pressure-receiving area of the diaphragm due to displacement, and the equalization valve inlet pressure that the valve receives.
Generates pG. That is, PQ:PA+ΔPG is expressed as.

From Equation 3, if the air amount QA is decreased in order to reduce the combustion amount, (PA-PM) is proportional to the square of QA, so the error in the air-fuel ratio increases rapidly for a constant ΔPG. It is.

Therefore, if you want to increase the combustion amount control ratio while keeping the air-fuel ratio within a certain error range and maintaining combustion stability and high efficiency, you must make the value of (PA-PM) sufficiently large or ΔPG
Increasing (PA-PG) means reducing the opening area of the air throttle, which means increasing the supply pressure of the blower, which not only requires a larger blower, but also increases the supply pressure. With household city gas or the like having a low PA, the PA becomes higher than the gas supply pressure, causing problems such as not being able to obtain the required amount of gas. Further, in order to reduce ΔPG, the diaphragm of the pressure equalizing valve becomes large, and there are also problems such as deterioration over time and difficulty in adjustment, which is not practical.

If a gas combustor for home use is used for hot water supply or space heating, and if the temperature of hot water is to be controlled by proportional control, a combustion amount adjustment ratio of about 115 to 1/10 is required, making it difficult to apply conventional methods. Ta.

OBJECT OF THE INVENTION The present invention solves the problems of the conventional technology, and it is possible to achieve a large combustion amount control ratio without increasing the size of the blower or valve device.
Another object of the present invention is to provide a high-load gas combustion control device with excellent air-fuel ratio stability.

Structure of the Invention In order to achieve this object, the present invention provides an air blower, an air amount adjusting means, and an air restrictor in the air passage, a gas amount adjusting means and a gas restrictor in the gas passage, and connects the downstream side of the air restrictor with the gas restrictor. A mixing unit that mixes the air constrictor downstream and a differential pressure sensor that generates an electric signal according to the pressure difference; and a differential pressure sensor that generates an electric signal in response to the pressure difference; The pressure upstream of the gas throttle is guided to the second pressure guide hole of the differential pressure sensor, and in the second state, the pressure upstream of the air throttle is transferred to the second pressure guide hole of the differential pressure sensor. and a differential pressure signal discrimination device that extracts two differential pressure signals corresponding to two states of the pressure switching valve from the output signal of the differential pressure sensor in synchronization with the pressure switching valve. A circuit configured to control either the air amount adjusting means or the gas amount adjusting means according to the load of the burner, and the other according to the difference between the two output signals of the differential pressure signal discrimination circuit. It is.

With this configuration, the detection error that occurs in a part of the differential pressure sensor is canceled out by taking the difference between the two signals of the differential pressure signal discrimination circuit, and the pressure difference between the pressure upstream of the air throttle and the pressure upstream of the gas throttle is accurately determined. Since it can detect the two pressures, it has the effect of equalizing the two pressures with high accuracy.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. 2 and 3. In FIG. 2, an air throttle 2 is connected downstream of the blower 1, and a mixing section 3 is connected downstream thereof. On the other hand, the gas passage is connected to the gas proportional control valve 10. It is connected to the mixing section 3 via a gas throttle 5. The outlet of the mixing section 3 is connected to a burner 6, and the mixed gas is combusted by the burner 6 and passes through a heat exchanger 11 to heat an object to be heated. The pressure guiding hole A13 of the differential pressure sensor 12 is connected to the common boat of the three-way pressure switching valve 14-a, and the pressure guiding hole A13 of the differential pressure sensor 12 is connected to the common boat of the three-way pressure switching valve 14-a.
15 is connected to a common boat of the pressure switching valve 14-b.

The gas passage upstream of the gas throttle is connected to the first state port of the switching valve 14-a and the second state port of the switching valve 14-b,
The air passage upstream of the air throttle is connected to the first state port of the switching valve 14-b and the second state port of the switching valve 14-a. The switching valves 14-a and 14-b are connected to the same drive signal. The output signal of the differential pressure sensor 12 is input to the differential pressure signal discrimination circuit 17 via the differential pressure sensor detection circuit 16, and the two output signals of the differential pressure signal discrimination circuit 17 are input to the differential amplifier 1.
It is applied to the positive phase and negative phase input terminals of 8, respectively. The output signal of the differential amplifier 18 is applied to an air-fuel ratio adjustment circuit 19 including an integral calculation element, and the output signal is applied to the gas proportional control valve 10.
to drive. The differential pressure signal discrimination circuit 17 includes m=tatami switching switches 20-a and 20-b, and a switch 2
The normally closed terminal of 0-Δ and the normally closed terminal of switch 20-b are connected to the output of the differential pressure sensor detection circuit 16, and the normally closed terminal of switch 20-a and the normally open terminal of switch 20-b are connected to ground (signal The common terminal of the switch 20-a is connected to the positive phase input terminal of the differential amplifier 18, and the common terminal of the switch 20-b is connected to the negative phase input terminal of the differential amplifier 18. The output of the generating circuit 21 is such that the first state time and the second state time are equal and repeat alternately, and the pressure switching valve 14-a.

14-b and the changeover switches 20-a and 20-b. On the other hand, the difference between the signal of the temperature sensor 22 provided at the outlet of the heat exchanger 11 and the temperature setting circuit 23 is input to the temperature adjustment circuit 24 including the blower rotation speed control section, and the output signal of the temperature adjustment circuit 24 is sent to the blower 1. Add to. Here, the air amount adjusting means is configured by controlling the rotation speed of the blower 1.

1, when the pressure switching valves 14-a and 14-b are in the first state, the PG is connected to the pressure guiding hole A13 of the differential pressure sensor 12.
pA is applied to the pressure guiding hole B15, and the pressure switching valve 14-1.
When 14-b is in the second state, the pressure guiding hole A1 of the differential pressure sensor
3, pG is applied to the PA pressure guiding hole B1B. In other words, the output of the differential pressure sensor is (PA-PG) and the opposite polarity -
Alternate outputs corresponding to (PA - PG) are obtained.

The differential pressure sensor 12 and the differential pressure sensor detection circuit 16 have error factors such as temperature drift and changes over time 9 assembly variations, and the output signal of the differential pressure sensor detection circuit 16 is ΔP+.
It is expressed as ε. (ΔP: differential pressure, ε: error) In FIG. )+ε1, when state 2 is (PA
-PG)+81. The signal at the positive phase input terminal of the Uid differential amplifier 18 is added only during the first state period (b).

(dl is the negative phase input terminal of the differential amplifier 18 (tb in the M number)
Only the period of the + second state is added. (el-(i'
)/i is the output signal of the differential amplifier 18, and since the time in the first state and the second state are equal, the average value is calculated using a slip circuit or the like, and the result is (e) - (iil shown by the broken line). PA-
PG) is obtained. It can be seen that the error components ε1 in both states have opposite phases and cancel each other out. Even if the error changes to 82 as shown on the right side of Fig. 3, it is the same (PA -, -
PG) signal is obtained. Therefore, the input signal (PA-P
The gas pressure proportional valve 10 is feedback-controlled so as to make G) zero, and can be maintained at PG:PA without being affected by errors of the differential pressure sensor 12 and differential pressure sensor detection circuit 16.

When the flow rate of the object to be heated, the set temperature, etc. change, the temperature adjustment circuit 24 adjusts the rotation speed of the blower 1 to adjust the air 111. At this time, following the change in PA, as described above (PA
= PG), the combustion amount is adjusted while keeping the air-fuel ratio constant as explained in the conventional example, and the temperature at the outlet of the heat exchanger 11 is controlled to be equal to the set temperature. be.

At this time, since it is not affected by the error of the differential pressure sensor, it has the effect of keeping the air-fuel ratio stable even if the combustion amount adjustment ratio is increased. Since the pressure difference between both ends of the trench air throttle 2 can be set small, the blower can be made small, and the differential pressure sensor does not require high precision, so it has the effect of being able to be made small and inexpensive. It is possible to use a differential pressure sensor such as a semiconductor diffusion type pressure sensor, which is conventionally unsuitable for this type of application due to large temperature fluctuations. The response speed is fast and the pressure can be switched in short cycles, making it easy to create a smoothing circuit.
Moreover, it does not affect the response speed of the control system. Therefore, it is possible to provide a compact device.

Next, another embodiment of the present invention will be described with reference to FIGS. 4 and 5. The difference in FIG. 4 from the above embodiment is that the differential pressure signal discrimination circuit 17 includes a first voltage storage circuit 25 and a second voltage storage circuit 26, and the signal of the sensor detection circuit 16 is applied to each input terminal. . Timing generation circuit 21
drives the pressure switching valves 14-a and 14-b, and
The first and second voltage storage circuits are configured to apply memory update control signals to the first and second voltage storage circuits, respectively. The difference between the output signals of the second voltage storage circuit is used as the input signal of the air-fuel ratio adjustment circuit. In FIG. 6 (al is the pressure switching valve 14-a).

14-b drive signal, (bl is the output signal of the differential pressure sensor detection circuit. (C) and (dl are the memory update control signals applied to the first and second voltage storage circuits, respectively, and the first voltage The output voltage of the memory circuit is (PA - PG) +
Which continuous signal ((e-1(it)), the output voltage of the second voltage storage circuit is -(PA -PG, )+ε continuous signal (t
el-tii) ). These two signals are subtracted by a differential amplifier and are shown as 2X (PA-PG
) is extracted, and it can be seen that the error ε is canceled out as in the previous example. Therefore, the same effect as the above embodiment can be obtained, and the voltage storage circuit may be an analog memory circuit or a digital memory circuit, and especially when configured using a microcomputer, the voltage storage circuit can be used as a timing generation circuit or a voltage storage circuit.

Since the differential amplifier circuit and the air-fuel ratio adjustment circuit can be realized using the internal circuits of a microcomputer and software, it is easy to simplify the electric circuit and reduce costs. 11 has been explained in which the output of the air-fuel ratio adjustment circuit controls the gas amount adjustment means with the output of the gas amount adjustment circuit, but conversely, the output of the temperature adjustment circuit controls the gas amount adjustment means, and the air-fuel ratio Exactly the same effect can be obtained even if the air amount adjusting means are individually controlled by the output of the adjusting circuit.

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

(1) A blower, an air amount adjusting means, and an air restrictor in an air passage, a gas amount adjusting means and a gas restrictor in a gas passage, a mixing section that joins the downstream of the air restricting and the downstream of the gas restricting, and a differential pressure sensor; In the first state, the pressure upstream of the air throttle is guided to the first pressure guide hole of the differential pressure sensor, the pressure upstream of the gas throttle is guided to the second pressure guide hole of the differential pressure sensor, and in the second state Conversely, a pressure switching valve that guides the pressure upstream of the air meter to the second pressure guiding hole of the differential pressure sensor and the pressure upstream of the gas throttle to the first pressure guiding hole of the differential pressure sensor, respectively; from the differential pressure sensor to the first one of the switching valves. It has a differential pressure signal discrimination circuit that extracts two differential pressure signals respectively corresponding to the second state, and controls the air amount adjusting means according to the load of the burner, and controls the two outputs of the differential pressure signal discrimination circuit. By controlling the other according to the difference between the two, the combustion amount is automatically adjusted according to the load, and the error of the differential pressure sensor is canceled out, so that the pressure upstream of the air throttle p' and the pressure upstream of the gas throttle are Since the pressure is equalized with high precision, the air-fuel ratio is kept constant.

(2) Since the pressure difference between both ends of the air restrictor can be set small, the pressure generated by the blower can be reduced, resulting in an effect of miniaturization.

(3) Differential pressure sensors cancel out their errors, so
Since high precision is not required, it is small and inexpensive, and has the advantage of eliminating the need for initial zero adjustment.

(4) As a result of the above, it is possible to provide a compact and inexpensive household combustion machine with a large combustion amount control ratio and high efficiency.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional gas combustion control device, FIG. 2 is a block diagram of an embodiment of the gas combustion control device of the present invention,
FIG. 3 is an operational waveform diagram, FIG. 4 is a block diagram of another embodiment of the present invention, and FIG. 5 is an operational waveform diagram. 1...Blower, 2...Air throttle, 3...
...Mixing section, 5...Gas throttle, 12...
Differential pressure sensor, 14-a. 14-b...Pressure switching valve, 16...Differential pressure sensor detection circuit, 17...Differential pressure signal discrimination circuit, 18...Differential amplifier, 20-a, 20
-b... Changeover switch, 21... Timing generation circuit, 25... First voltage storage circuit, 26...
...Second voltage storage circuit. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 2 Figure 3 (pA-le) - εf (1'/l sound) - and. ii (++A-1'cy+ Figure 4

Claims (3)

[Claims] (1) Blower and air supplying combustion air to the air passage
II: A mixing device that has an adjusting means and an air restrictor, has a gas amount adjusting means and a gas restrictor in the gas passage, and mixes air and gas by merging downstream of the air restrictor and downstream of the gas restrictor. a differential pressure sensor that generates an electrical signal in accordance with the pressure difference between the two introduced pressures; and a differential pressure sensor that has two switching states and in its first state changes the pressure upstream of the air throttle to the differential pressure sensor. The pressure upstream of the gas throttle is introduced into the first pressure guide hole to the second pressure guide hole of the differential pressure sensor T)j, and in the second state, the pressure upstream of the air throttle is transferred to the pressure upstream of the differential pressure sensor. The pressure upstream of the gas throttle is input to the first pressure guiding hole of the differential pressure sensor.
a pressure switching valve configured to lead the pressure to the respective pressure guiding holes; and two states of the switching valve in synchronization with the monthly power switching force.
and a differential pressure signal discrimination circuit that extracts two differential pressure signals corresponding to A gas combustion control device that performs control according to the difference between two output signals of a signal discrimination circuit. (2) The pressure switching valve is the first. The switch circuit alternately switches to the second state at equal time intervals, and the differential pressure signal discrimination circuit switches and connects the signal of the differential pressure sensor to two output terminals in synchronization with the operation of the pressure switching valve No. 111. Patent M!, in which the average value of the difference signal between the two output signals of the switch circuit is used as the control signal! ! 1. The gas combustion control device according to item 1. (3) The first circuit in which the differential pressure signal discrimination circuit memorizes the signal of the differential pressure sensor. 2. The gas combustion control device according to claim 1, further comprising a second voltage storage circuit, the memory updating operation of which is synchronized with the two switching states of the pressure switching valve.