JPS5818050Y2 - Combustion safety device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a safety device for preventing abnormal combustion in a forced air supply/exhaust type combustion device.

Conventionally, in forced air supply and exhaust type combustion equipment, the presence or absence of air being blown by a blower was detected using a pressure switch by guiding the wind pressure in the air supply and exhaust passage, and when the pressure switch was activated, the operation of the combustion equipment was stopped. Safety could not be guaranteed and there was a high risk of malfunction.

On the other hand, in a combustion device that has an air-fuel ratio control device that controls the mixture ratio of air and fuel (air-fuel ratio) and also controls the combustion amount, if the combustion amount becomes too small, the error of the air-fuel ratio control device can be ignored. There is a risk that the air-fuel ratio will fluctuate and cause abnormal combustion.

For this reason, it is necessary to set in advance a minimum combustion amount for stable combustion in the burner within the controllable range of the air-fuel ratio control device, and to prevent combustion below the minimum combustion amount.

The present invention includes a first pressure switch that uses wind pressure to detect a preset minimum combustion amount that guarantees stable combustion;
and a second pressure switch that detects a set combustion amount that is larger than the minimum combustion amount using wind pressure, and when the second pressure switch is activated, the combustion amount is maintained at a combustion amount that is larger than the minimum combustion amount. In addition to preventing the amount of combustion from becoming too small, if for some reason the combustion amount falls below the minimum combustion amount, the first pressure switch will stop combustion. Prevent crop errors.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall configuration of a forced air supply/exhaust type combustion apparatus equipped with this combustion safety device.

In FIG. 1, there is an air nozzle 2 in a part of the air supply path 1, which generates a pressure difference in relation to the air volume, and has a high pressure section 3 and a low pressure section 4.
form.

Gas and air are mixed in the low pressure section 4, and the mixed gas is combusted in the combustor 6 through the mixing pipe 5, heat exchanged, and discharged from the exhaust path 1' by the blower 7.

The gas pipe line 8 includes a thermoelectric safety valve 9, a gas pressure regulator 10,
A solenoid valve 11 is arranged, and gas is ejected from a gas nozzle 12 to a low pressure part 4 of an air nozzle 2.

The pressure of the high pressure section 3 of the air nozzle 2 is guided to the gas pressure adjustment device 10 through a pressure guiding pipe 13, and the air-fuel ratio is controlled by the air nozzle 2 and the gas pressure adjustment device 10.

14 is a pilot burner attached to the combustor 6, air is supplied from the air supply line 1 through a pilot air supply pipe 15, and gas is supplied from the gas line 8 via a pilot gas burner 16 and a pilot gas pipe 17. Ru.

Further, the electromotive force generated in the thermoelectric element (not shown) by combustion in the pilot burner 14 is supplied to the thermoelectric safety valve 9 from a lead wire 19 via a contact 18 .

20 is a first pressure switch, 21 is a second pressure switch, and pressure chambers 28, 29, 30, 31 are formed by casings 22.23, 24.25 and diaphragms 26.27, respectively.
, and the pressure of the high pressure part 3 of the air nozzle 2 is guided to the pressure chamber 28.30 by the pressure introduction pipe 33', 32' through the pressure lead-out pipe 33.32, respectively, and the pressure chamber 29.30 is formed.
31, the pressure of the low pressure part 4 of the air nozzle 2 is connected to the pressure outlet pipe 3.
5° 34 through pressure introduction pipes 35' and 34', respectively.

As mentioned above, the first pressure switch 20 opens and closes the contact 18 located in the middle of the lead wire 19 that transmits thermoelectromotive force, and the second pressure switch 21 opens and closes the contact 37 that is part of the circuit that guarantees the minimum combustion amount. do.

38 and 39 are pressure setting springs, respectively.

FIG. 2 is a specific example of a speed control circuit for a blower motor.

60 is a thermistor for temperature detection, resistance 700.701
．． 702 and a bridge.

The bridge output e, is inverted and amplified by the amplifier 704 to become e.

The amplification factor of amplifier 704 is set in advance by resistor 703.

ep is applied to the base of the transistor 711 via the current limiting resistor 729 and the diode 709.

The emitter of the transistor 711 is grounded through a series connection of a diode 712 and a capacitor 713, and a Vcc voltage, which will be described later, is applied between the collector and the ground.

Resistors 714, 716, 717. PUT 715 and capacitor 713 form a so-called strain oscillator,
Its output is passed through a transformer 718 to a triac 719
is applied to the gate of the fan motor 50 to control the phase of the fan motor 50.

Transistor 711. Diode 712 is capacitor 7
13, and therefore, by changing its base voltage, the phase of the motor 50 can be controlled.

730 is a transformer that drops the commercial power supply voltage applied between the power supply terminals P and P', and has a full-wave rectifier bridge 720 on its secondary side, and a Zener diode 722 and a Zener current limiter that clip the bridge output to V2. A flow resistance 721 is provided.

The Vcc voltage is a voltage clipped to Y2 of the power supply layer.

Furthermore, Vcc is connected to diode 723 and capacitor 724.
is smoothed to obtain vCC2, which is used as a DC power source for a bridge including the thermistor 60, an amplifier 704, an amplifier 708 to be described later, and the like.

Next, the simulator will be explained.

The output ep of the amplifier 704 is the second pressure switch 2 described above.
The voltage is applied to the series connection of a resistor 706 and a capacitor 707 through a contact 705A (37A in FIG. 1).

Voltage e of capacitor 707. is a first-order lag whose transfer function is given by T/(1+ST) with respect to ep.

The T is given by the product of the resistance value R and the capacitance C of the resistor 706 and capacitor 707.

It is assumed that the amount of air blown Q responds to the applied voltage Vm of the motor 50 with a first-order lag of the transfer function KA/(1+5TA).

The delay of Vm with respect to ep is several tens of m5 ec at most, while the delay of TA with respect to several seconds is negligible.

Here, if RC is chosen appropriately so that TA=T, then C
C is a voltage obtained by simulating the amount of air blown Q.

That is, a resistor 706 and a capacitor 707 are connected in series,
The voltage e of the capacitor 707.

is a voltage obtained by simulating the air blowing amount Q with respect to Vm, that is, ep.

If this voltage is input to a voltage follower constituted by an amplifier 708, the output e of the amplifier 708 will be e.

This voltage ef is connected to the resistor 728 and the diode 710.
is applied to the base of the transistor 711 via.

At the connection point between the resistor 728 and the diode 710, there is another contact 705B (37B in FIG. 1) of the second pressure switch.
) is provided.

In normal operating conditions, the air flow rate Q is larger than the operation setting air volume QB of the second pressure switch 21, so the contacts 705A, 705B (37A, 37 in FIG.
B) is closed and the output ef of amplifier 708 is connected to resistor 72.
8. Grounded via contact 705B, transistor 71
Only ep is applied to the base of 1.

If ep decreases and Q decreases and reaches Q8, contacts 705 A, 705 B open, and then capacitor voltage e.

1 becomes the output e of the amplifier 708.

Since ecl>e, ef=eel is applied to the base of transistor 711, and Q maintains Q8.

The set air volume QB for operation of the second pressure switch 21 is set to be slightly larger than the air flow volume Qmirl at the minimum combustion volume that guarantees stable combustion.

FIG. 3 is a graph showing the operation of the circuit of FIG. 2, in which a shows the base voltage et of the transistor 711,
8, where b indicates the output voltage ef=ec and C indicates the air volume Q, et is et□ and equal to ep□ before time t1.
Let ec be ecl and Q be QA.

At time t1, the hot water temperature becomes much higher than the planned temperature,
The resistance value of the thermistor 60 becomes small, so ep becomes ep
□ and et is also et□ = ep, so et2 = e
It decreases to p2.

ec gradually decreases with a first-order lag, and the change is similar to when Q decreases with a first-order lag than QA.

When Q-QB is reached at time t2, the second pressure switch 21
Although there is a slight response delay, it is ignored because it is much smaller than the delay in the air flow rate Q with respect to the applied voltage Vm of the motor 50.
705 B opens, the amplifier 708 holds the voltage ec=ec2 at that time, and after t2 ef=ec2
becomes.

Since this voltage is greater than ep2, it becomes et2-ec2, and Q maintains Q8.

Next, the operation of the first pressure switch 20 will be described.

Below the minimum combustion amount, stable combustion is not guaranteed due to fluctuations in air-fuel ratio control, so the air volume Q at the minimum combustion amount is
It is necessary to stop combustion at min.

Therefore, the operation setting air volume of the first pressure switch 20 is Qmi.
It is next to n.

In Figure 1, due to some abnormality in the air supply/exhaust system, such as a failure of the blower or a blockage in the air supply/exhaust passage, the air flow rate is reduced to Qm.
When the temperature becomes less than in, the contact 18 opens and no current flows through the thermoelectric circuit of the pilot burner, and the thermoelectric safety valve 9 closes to cut off the gas circuit.

It is preferable that the operating air volume QB of the second pressure switch 21 be closer to the operating air volume Qmin of the first pressure switch 20, since combustion can be performed with a lower combustion amount.

However, when the air volume suddenly decreases as shown in Fig. 3, the second pressure switch 21 may not operate even though there is no abnormality in the air supply/exhaust system due to setting errors in the syssilator and variations in the response delay of the pressure switch. At the same time the first
The pressure switch 20 may be activated, or the first pressure switch 20 may be activated due to a slight time delay until the second pressure switch 21 is activated and a predetermined voltage is applied to the motor 50 to start it. .

To prevent this malfunction, the response delay of the first pressure switch 20 is made larger than the response delay of the second pressure switch 21.

That is, the second pressure switch 21 is made to respond immediately to a decrease in the amount of air blown, and the first pressure switch is made to respond with a slight delay.

Specifically, in order to achieve this purpose, the pressure outlet pipe 33, 35 or the pressure inlet pipe 34 of the first pressure switch 20 is
It is conceivable to provide an aperture at ', 35'.

With the above configuration, the second pressure switch 21 operates immediately to maintain the motor 50 at a predetermined voltage when the air flow rate suddenly decreases.

Since the other first pressure gas, the switch 20, has a slow response, it guarantees the time it takes for the motor 50 to start and maintain the airflow amount QB, and will not malfunction if there is no abnormality in the air supply/exhaust system.

As described above, according to the present invention, by providing the first pressure switch 21 that detects the minimum combustion amount and the second pressure switch 22 that detects the combustion amount that is set slightly larger than the minimum combustion amount, the combustion device It is safe because it always performs stable combustion and stops operation when the amount of combustion is below the minimum amount.

Furthermore, the response to the pressure of the first pressure switch 20 is
By setting the switch later than the switch 21, it is possible to prevent malfunction when the combustion amount suddenly decreases.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a forced air supply/exhaust combustion device equipped with a combustion safety device according to an embodiment of the present invention, Fig. 2 is a circuit diagram of the speed control circuit of the blower motor, and Fig. 3 is the operation of the circuit. This is a graph showing. 1...Air supply path, 1'...Exhaust path, 2.
...Air nozzle, 3...High pressure section, 4...
...Low pressure section, 5...Mixing pipe, 6...
・Combustor, 7...Blower, 8...Gas pipe line, 9...Thermoelectric safety valve, 10...Gas pressure regulator, 11... ...Solenoid valve, 12...
...Gas nozzle, 14...Pilot burner,
20...First pressure switch, 21...
Second pressure switch.

Claims (3)

[Scope of utility model registration request] (1) A first pressure switch for starting or stopping operation of the combustion device by detecting a preset minimum combustion amount using wind pressure in a forced air supply/exhaust type combustion device; A combustion safety device comprising: a second pressure switch that detects the amount of combustion by wind pressure; and a combustion controller that maintains the amount of combustion when the second pressure switch is activated. (2) The combustion safety device according to claim 1, wherein the response of the first pressure switch to pressure is set to be slower than the response of the second pressure switch. (3) The combustion safety device according to claim 1 or 2, wherein the wind pressure applied to the first pressure switch and the second pressure switch is derived from an air throttle section of an air-fuel ratio control device.