JPS649531B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ventilation safety device for a forced air combustion appliance that detects whether or not air is being supplied normally by a blower fan. The purpose of this is to ensure that fire-extinguishing safety operations are carried out immediately in the event of a fire.

Conventionally, in the case of the so-called FE combustion method, which is a forced air combustion appliance with the air supply side open indoors, even if a back pressure of 12 mm of water column is generated at the end of the exhaust path, the flame will not extinguish, backfire, or flames will be extinguished. Standards have been established that there should be no abnormality such as overflow, and that if the wind pressure at the exhaust section is increased, the gas passage will be closed before a flame abnormality occurs. The blower fan that blows the air must have sufficient capacity. A wind pressure switch is generally used as a safety device for detecting the air blowing state of the blower fan. However, in the pressure detection method of such a wind pressure switch, as shown in Fig. 1, the positive pressure detection tube B installed on the outlet side of fan A
In the positive pressure detection method that detects the air blowing pressure, when a head wind pressure is applied, the positive pressure increases and switch C does not turn off. Also, as shown in Figure 2, Juan A
With the negative pressure detection method in which a negative pressure detection tube D is installed on the suction side of the fan A, even if a considerably high back pressure is generated, it takes some time for the suction power of the fan A to weaken, and during that time, abnormal combustion such as overflowing of flames may occur. Moreover, in the case of a device that detects negative pressure on the fan discharge side as shown in Fig. 3, the detection ability is undeniably lower than that of the one shown in Fig. 2, and switch C immediately turns off when it receives back pressure. Therefore, there is a problem that combustion cannot be sustained up to the above-mentioned reference back pressure. As described above, in either system, the wind pressure switch could not function satisfactorily as a safety device.

The present invention has been made with the aim of solving such difficulties, and it goes without saying that positive pressure detection is performed on the fan discharge side, but more stable detection ability can be obtained when negative pressure detection is performed on the fan suction side. Focusing on this, we provide a new detection method that skillfully relates both positive and negative detection methods.

The embodiment will be described below with reference to FIGS. 4 and 5. 1 is an exterior of a forced air combustion appliance, 2 is a heat exchanger provided in the exterior 1, 3 is a burner case with a built-in gas burner 4, 5 is a gas jet nozzle, and 6 is connected to the upper part of the heat exchanger 2. It is an exhaust stack and extends outdoors. Reference numeral 7 designates a Shirotsuko-type blower fan with a discharge port 8 connected to the bottom surface of the burner case 3, and the fan 7 blows the gas burner 4 and the nozzle 5.
It is designed to send combustion air to. 9 is a negative pressure chamber 11 and an atmospheric pressure chamber 12 by a diaphragm 10.
This is a negative pressure operated wind pressure switch which is configured such that a micro switch 13 which is pressed and closed by displacement of a diaphragm 10 faces the negative pressure chamber 11 side. 14 is a solenoid valve that supplies gas to the nozzle 5, and the micro switch 13 is arranged in its power supply circuit. Reference numeral 15 designates a pressure detection tube whose one end faces the suction side of the fan 7, more specifically, the interior of the impeller 16, and whose other end is connected to the negative pressure chamber 11. The tip of the tube 17 is exposed to the inside of the burner case 3. Further, this branch pipe 17 is provided with an orifice function by, for example, narrowing its inner diameter as will be described later. Reference numeral 18 denotes an intake port opened at a proper location in the exterior 1.

When the fan 7 is driven in such a configuration,
Due to the suction force, the negative pressure chamber 11 of the wind pressure switch 9 becomes negative pressure via the pressure tube 15, and the diaphragm 1
0 is displaced and closes the micro switch 13, the solenoid valve 14 is then opened to shift the gas burner 4 to steady combustion. At this time, the fan discharge pressure is introduced into the pressure detection tube 15 from the branch pipe 17, which acts to reduce the negative pressure suction force on the fan suction side. The negative pressure settles to a negative pressure value that is slightly relieved by the positive pressure on the fan discharge side. With this, the wind pressure switch 9
detects the drive of the fan 7.

During this steady combustion, when headwind pressure is applied to the exhaust stack 6, the internal pressure of the burner case 3 increases, but this increase in internal pressure hardly reaches the suction side of the fan 7, and the negative pressure on the fan suction side still remains at a high value. show. However, the increased internal pressure is directly applied to the branch pipe 17, and this causes the negative pressure acting on the diaphragm 10 to be significantly reduced, causing the micro switch 13 to open. This is how the safety function works in the event of back pressure.

Note that the inner diameter of the branch pipe 17 determines the degree of negative pressure relaxation effect caused by positive pressure, so by appropriately setting the inner diameter of this branch pipe, the back wind pressure will overcome the fan capacity and the burner 4 will become abnormal. It is easy to turn off the wind pressure switch 9 just before starting combustion. Note that an orifice member may be inserted into the branch pipe 17.

In summary, the present invention solves the problem that when the negative pressure that operates a negative pressure-operated wind pressure switch is obtained only on the suction side of the fan, it is difficult for the back wind pressure to cross the fan and reach the negative pressure detection part. This problem was solved by introducing positive pressure from the fan discharge side, which is directly affected by back wind pressure, as if bypassing the fan, and adding this positive pressure to the negative pressure that operates the wind pressure switch, which satisfies the criteria mentioned at the beginning. Even if a fan with a large capacity is used, it is extremely effective in being able to immediately turn off the wind pressure switch and carry out fire extinguishing safety in the event of an abnormality.

It goes without saying that by using a large-capacity fan, there is no need for the wind pressure switch to have a large return spring, and that a very ordinary wind pressure switch can be used.

In addition, the present invention is not limited to the above embodiments,
As shown in Fig. 6, negative pressure introduction pipe 19 and positive pressure introduction pipe 20
are provided separately and each is connected to the negative pressure chamber 1 of the wind pressure switch 9.
1, or as shown in FIG. 7, positive pressure may be introduced at one end of the pressure measuring tube 21 and negative pressure on the fan suction side may be introduced at a midpoint thereof. In any case, the positive pressure on the fan discharge side can be taken from a part other than the burner case, for example, from the upper part of the heat exchanger.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional positive pressure detection method, Fig. 2 is an explanatory diagram of a conventional negative pressure detection method, Fig. 3 is an explanatory diagram showing another conventional example of a negative pressure detection method, and Fig. 4 is an explanatory diagram of a conventional negative pressure detection method. FIG. 5 is a partial cross-sectional view of the same, FIG. 6 is a main part configuration diagram showing another embodiment of the invention, and FIG. 7 is still another embodiment of the invention. It is a main part configuration diagram showing the. 7...Blower fan, 9...Wind pressure switch, 11
...Negative pressure chamber.

Claims (1)

[Claims] 1 Negative pressure obtained on the suction side of a blower fan that sends combustion air and positive pressure obtained on the discharge side of the blower fan are both applied to the same negative pressure chamber side of a negative pressure operated wind pressure switch. A ventilation safety device in a forced air combustion appliance that operates the wind pressure switch.