JP6625924B2 - Premixing device - Google Patents

Description

  The present invention relates to a premixing device that mixes fuel gas with air and supplies the mixture to a burner that is a heat source of a heat exchanger for hot water supply via a fan.

  Conventionally, as a premixing device of this type, according to Patent Document 1, the downstream end of a gas supply path provided with a flow rate control valve for supplying a fuel gas is connected to a gas suction section provided in an air supply path on the upstream side of a fan. Air resistance switching means for switching the air flow resistance of the air supply path upstream of the gas suction unit to a large or small value, and gas resistance switching the air flow resistance of the gas supply path downstream of the flow control valve to a large or small size. There is known one provided with switching means.

  By the way, when a proportional valve is used as a flow control valve, the proportional valve is controlled so that an amount of fuel gas corresponding to the required combustion amount is supplied, and the air-fuel ratio of the air-fuel mixture supplied to the burner is kept constant. The fan speed is controlled in accordance with the required combustion amount. However, when the required combustion amount falls below a predetermined value, the fan rotation speed falls below the lower limit rotation speed that can maintain the proportional characteristic of the blown air amount, or the proportional valve current (current supplied to the proportional valve) is proportional to the gas supply amount. If the current falls below the lower limit current at which the characteristics can be maintained, it becomes impossible to supply air or fuel gas in an amount corresponding to the required combustion amount.

  A zero governor that maintains the secondary gas pressure at atmospheric pressure may be used as the flow control valve. In this case, the supply amount of the fuel gas changes according to the differential pressure between the atmospheric pressure, which is the secondary gas pressure, and the negative pressure in the air supply passage. Since the negative pressure in the air supply path changes according to the fan speed, the supply amount of the fuel gas changes according to the fan speed, that is, the air supply amount. Therefore, by controlling the fan speed in accordance with the required combustion amount, air and fuel gas in an amount corresponding to the required combustion amount are supplied to the burner.

  Even in this case, when the fan rotation speed is equal to or lower than the lower limit rotation speed at which the proportional characteristic of the blown air amount can be maintained, it becomes impossible to supply air or fuel gas in an amount corresponding to the required combustion amount. Therefore, when the required combustion amount becomes equal to or less than the predetermined value, the air resistance switching means increases the ventilation resistance of the air supply passage so that the fan rotation speed does not fall below the lower limit rotation speed. It is necessary to be able to supply an appropriate amount of air. In addition, simply increasing the ventilation resistance of the air supply passage increases the negative pressure in the air supply passage, which causes the supply amount of the fuel gas to exceed an amount corresponding to the required combustion amount. It is necessary to increase the ventilation resistance of the gas supply path in accordance with the increase.

  Therefore, in the above conventional example, the air resistance switching means increases the ventilation resistance of the air supply path and the gas resistance switching means increases the ventilation resistance of the gas supply path. The gas flow resistance is reduced and the gas resistance switching means can be switched to a large capacity state in which the gas supply path has a low gas flow resistance. When the required combustion amount exceeds the maximum combustion amount obtained in the small capacity state, the large capacity state is set. When the required combustion amount falls below the minimum combustion amount that can be obtained in the large capacity state, the state is switched to the small capacity state.

  Here, in the device described in Patent Document 1, the air resistance switching means is provided in a portion of the air supply path upstream of the gas suction section, and has an open attitude parallel to the longitudinal direction of the air supply path and the air supply path. The gas resistance switching means is constituted by a switching valve provided to be capable of opening and closing freely in a gas supply path. A stepping motor for rotating the butterfly valve and an interlocking mechanism for opening and closing the switching valve in conjunction with the rotation of the butterfly valve between the open position and the closed position are provided.

  Note that, in order to prevent explosion ignition of the burner, the ignition operation of the burner is performed in a small capacity state in which the butterfly valve is turned to a closed posture. There is also conventionally known a device provided with a close detector composed of a Hall IC for detecting rotation of the butterfly valve to a closed position.

  By the way, in the burner serving as a heat source of the heat exchanger for hot water supply, the ignition operation of the burner is performed when the amount of water detected by the water amount sensor provided in the water supply path to the heat exchanger becomes equal to or more than a specified amount. ing. However, even if the water cannot pass through the heat exchanger due to freezing, the burner may be ignited due to a failure of the water amount sensor, and there is a possibility that the fuel cell may run dry.

JP-A-2005-230113

  In view of the above, it is an object of the present invention to provide a premixing device that can prevent ignition of a burner in a frozen state even if a failure of a water amount sensor occurs.

In order to solve the above-mentioned problem, the present invention is a premixing device that mixes a fuel gas with air and supplies the mixture to a burner serving as a heat source of a heat exchanger for hot water supply via a fan. downstream end of the gas supply passage which is interposed a supply flow rate control valve is connected to the gas suction portion provided on the upstream side air supply passage of said fan, said portion of the air supply passage upstream of the gas suction portion and air resistance switching means for switching the airflow resistance of the magnitude, and a gas resistance switching means for switching the magnitude of the flow resistance of the portion of the gas supply path on the downstream side of the flow control valve, the air resistance switching means, than said gas suction unit provided in the portion of the air supply path upstream, freely rotated in the closed position perpendicular to the longitudinal direction of the longitudinal direction in the open parallel orientation of the air supply passage said air supply passage It is composed of a butterfly valve, before Gas resistance switching means is composed of a switching valve which is provided to be freely opened and closed to the gas supply path, a stepping motor for rotating the butterfly valve, the rotation of the closing position and opening position of the butterfly valve an interlocking mechanism for opening and closing the switching valve in conjunction with each other, in which and a closing knowledge unit comprising a rotation in the closing position of the butterfly valve from the detectable Hall IC, detects angular range with decreasing ambient temperature is determined based on the temperature characteristics of the Hall IC to become narrower, is lower than a predetermined temperature outside the detection angle range of the closing knowledge unit, it falls within the detection angle range of the closing knowledge instrument at the predetermined temperature or higher set the closed side origin position a predetermined rotational angle in the vicinity of the closed position the butterfly valve, the point of the burner in a state in which the butterfly valve is rotated to the closing side origin position said Performs the operation, but when the rotation of the said closed side origin position of the butterfly valve-closing intellectual device is not detected and inhibits the ignition operation.

  According to the present invention, in cold weather when the air temperature is lower than the predetermined temperature, even if the butterfly valve is rotated to the close origin position, the close detector does not detect this and the ignition operation of the burner is prohibited. Therefore, even if a failure occurs in the water amount sensor, ignition of the burner in a frozen state can be prevented, and fail-safe can be achieved.

1 is a cut-away side view showing a premixing device according to an embodiment of the present invention. FIG. 2 is a plan view cut along the line II-II in FIG. 1. Sectional drawing cut | disconnected by the III-III line of FIG. Sectional drawing cut | disconnected by the IV-IV line of FIG. FIG. 5 is a side view of the reduction gear as viewed from the direction of arrow V in FIG. 1. FIG. 4 is a flowchart showing control contents performed by the premixing device of the embodiment.

  With reference to FIG. 1, reference numeral 1 denotes a burner which is a heat source of a heat exchanger 2 for hot water supply and is composed of an all-primary combustion type burner having a combustion surface 1a on which an air-fuel mixture is ejected and burns. A fan 3 is connected to the burner 1. The premixing device A according to the embodiment of the present invention mixes the fuel gas with the air and supplies the mixture to the burner 1 via the fan 3. .

  The premixing device A includes an air supply path 4 upstream of the fan 3 and a gas supply path 5 for supplying fuel gas. As shown in FIG. 4, an on-off valve 6 and a flow control valve 7 composed of a proportional valve or a zero governor are provided at an upstream portion of the gas supply path 5. Further, the downstream end of the gas supply path 5 is connected to a gas suction section 41 provided in the air supply path 4.

  Further, the premixing device A includes an air resistance switching unit that switches the ventilation resistance of the portion of the air supply passage 4 upstream of the gas suction unit 41 to a large or small amount, and a gas supply passage 5 downstream of the flow control valve 7. Gas resistance switching means for switching the ventilation resistance of the portion between large and small. Then, the air resistance of the air supply path 4 is increased by the air resistance switching means, and the ventilation resistance of the gas supply path 5 is increased by the gas resistance switching means. And the gas resistance switching means can be switched to a large capacity state in which the ventilation resistance of the gas supply path 5 is reduced, so that the required combustion amount (combustion amount required to discharge hot water at the set hot water temperature) is small. When the maximum combustion amount obtained in the state exceeds the maximum combustion amount, the state is switched to the large capacity state, and when the required combustion amount falls below the minimum combustion amount obtained in the large state, the state is switched to the small capacity state.

  An inner cylinder 43 is provided in a portion of the air supply path 4 upstream of the gas suction part 41 with a gap between the air supply path 4 and a peripheral wall surface 42 of the air supply path 4. The gap between the peripheral wall surface 42 of the air supply passage 4 and the outer peripheral surface of the inner cylinder 43 forms a sub-passage 4b parallel to the main passage 4a in the inner cylinder 43. As shown in FIG. 2, a plurality of arc-shaped through holes 43b serving as outlets of the sub passages 4b are formed in the flange portion 43a at the downstream end (the upper end in FIGS. 1 and 3) of the inner cylinder 43.

  In addition, a butterfly valve 8 made of a disc that is rotatable about a shaft 81 is provided in the inner cylinder 43, and the butterfly valve 8 constitutes an air resistance switching unit. A stepping motor 82 is connected to a shaft 81 of the butterfly valve 8 via a reduction gear 83. Then, at the time of switching to the low capacity state, the butterfly valve 8 is operated by the stepping motor 82 to move the butterfly valve 8 from the opening posture side shown by a virtual line parallel to the longitudinal direction of the air supply path 4 in the longitudinal direction of the air supply path 4. 1 to 3, the butterfly valve 8 is rotated from the closed posture side to the open posture side by the operation of the stepping motor 82 when switching to the high capacity state. I try to make it. When the butterfly valve 8 is turned to the closed position, the main passage 4a is almost closed, the flow of air is substantially restricted to the sub passage 4b, and the ventilation resistance of the air supply passage 4 increases.

  A portion of the air supply passage 4 adjacent to the upstream side of the gas suction portion 41 is provided with a venturi portion 44 having a smaller diameter than that of the air supply passage 4 in which the inner cylinder 43 is disposed. The portion of the air supply passage 4 adjacent to the downstream side of the venturi portion 44 is surrounded by a cylindrical portion 45 having a larger diameter than the venturi portion 44. Then, the downstream end of the venturi section 44 is inserted into the upstream end of the cylindrical section 45 with an annular gap therebetween, and this gap constitutes the gas suction section 41. The peripheral wall surface of the air supply path 4 between the sub-passage 4 b and the venturi section 44 is formed with a tapered surface 46 whose diameter decreases toward the venturi section 44.

  The gas supply path 5 is located on the upstream side of the gas chamber 51 at the downstream end, which is in communication with the gas suction part 41 and is formed by a gap between the cylinder part 45 and an outer wall surface 51a surrounding the cylinder part 45, A valve chamber 91 is provided in parallel with the passage portion 52 that is always in communication with the gas chamber 51. In the valve chamber 91, there is provided a switching valve 9 formed in a valve seat 92 at the lower end of the valve chamber 91 and opening and closing a valve hole 93 communicating with the passage portion 52. The switching valve 9 constitutes a gas resistance switching means. are doing. When the switching valve 9 is seated on the valve seat 92 and is in a fully-closed state in which the valve hole 93 is closed, the flow of gas through the valve chamber 91 is shut off, and the ventilation resistance of the gas supply path 5 increases.

  The switching valve 9 is opened and closed via an interlocking mechanism 10 as the butterfly valve 8 rotates. As shown in FIGS. 1 and 4, the interlocking mechanism 10 includes a cam 101 connected to a shaft 81 of the butterfly valve 8, a rod 102 having a lower end in contact with the cam 101 and extending upward and connected to the switching valve 9. With the rotation of the butterfly valve 8, the rod 102 moves up and down via the cam 101, and the switching valve 9 is opened and closed. That is, when the butterfly valve 8 is rotated to the open posture side, the rod 102 is pushed up by the cam 101, and the switching valve 9 is moved up, that is, opened, against the urging force of the valve spring 94. When the valve 8 is turned to the closed posture side, the push-up of the rod 102 by the cam 101 is released, and the switching valve 9 is moved down by the urging force of the valve spring 94, that is, is closed.

  Further, a fixed plate 84a disposed in a case 84 accommodating a stepping motor 82 and a reduction gear 83 includes a close detector 85 composed of a Hall IC capable of detecting rotation of the butterfly valve 8 to the closed position, and a butterfly valve 8 An open detector 86 composed of a Hall IC capable of detecting the rotation of the butterfly valve 8 to the open position, and a stopper pin 87 for mechanically restricting the rotation range of the butterfly valve 8 are provided. More specifically, as shown in FIG. 5, a magnet 83a for a close detector and a magnet 83b for an open detector are attached to a reduction gear 83 connected to the shaft 81 of the butterfly valve 8, and a stopper pin 87 is inserted. The arc-shaped groove 83c to be formed is formed. When the butterfly valve 8 rotates to the closed position, the magnet 83a faces the close detector 85, a detection signal is output from the close detector 85, and when the butterfly valve 8 rotates to the open position, the magnet 83b faces the open detector 86, a detection signal is output from the open detector 86, and when the butterfly valve 8 is rotated beyond the closed posture or the open posture, the stopper pin 87 is turned into the arc-shaped groove 83c. The one end or the other end is contacted so that further rotation of the butterfly valve 8 is prevented.

  By the way, the burner 1 serving as a heat source of the hot water supply heat exchanger 2 has a water amount detected by a water amount sensor 2b interposed in a water supply path 2a to the heat exchanger 2 is equal to or more than a specified amount in order to prevent idle heating. I try to ignite when. Further, in order to prevent explosion and ignition of the burner 1, the ignition operation of the burner 1 (sparking with an unillustrated ignition electrode facing the combustion surface 1a and opening the on-off valve 6) needs to be performed in a small capacity state. There is. Further, it is desired that the ignition of the burner 1 in the frozen state can be prevented even if the water amount sensor 2b fails.

  Here, the Hall IC outputs a detection signal when a magnet exists within a predetermined detection angle range centered on a position directly facing the Hall IC, but the detection angle range is narrowed with a decrease in ambient temperature. It has temperature characteristics. Thus, in the present embodiment, based on this temperature characteristic, the temperature falls outside the detection angle range of the close detector 85 below a predetermined temperature (for example, 0 ° C.), and falls within the detection angle range of the close detector 85 above the predetermined temperature. A predetermined rotation angle near the closing posture of the butterfly valve 8 is set to the closing-side origin position, and the control shown in FIG. 6 is performed.

  In this control, when the power is turned on, first, an initialization process for finding the origin is performed. In the initialization process, in step 1, the mechanical lock is closed, that is, the end of the arc-shaped groove 83c in the closing direction is brought into contact with the stopper pin 87. Next, in step 2, the stepping motor 82 is driven by a predetermined number of steps in the opening direction of the butterfly valve 8. Then, after driving the stepping motor 82 in the closing direction by the number of steps corresponding to the closing-side origin position in STEP3, whether the closing detector 85 detects the rotation of the butterfly valve 8 to the closing-side origin position in STEP4. Determine whether or not. If no detection is made, it is determined in STEP 5 whether the number of non-detections has reached a predetermined number (for example, 10 times), and the process returns to STEP 1 until the predetermined number is reached. Go ahead and stop abnormally.

  When the close detector 85 detects the rotation of the butterfly valve 8 to the close-side origin position, the process proceeds to STEP 7 to determine whether or not the detected water amount of the water amount sensor 2b is equal to or more than a specified amount. Then, when the detected water amount becomes equal to or more than the specified amount at the start of hot water supply, the process proceeds to STEP 8 to perform an ignition operation. Then, in STEP 9, it is determined whether or not to switch to the large capacity state, that is, whether or not the required combustion amount exceeds the maximum combustion amount obtained in the small capacity state. If the state should be switched to the large capacity state, the stepping motor 82 is driven in the opening direction by the number of steps corresponding to the opening posture in STEP10, and then the opening detector 86 rotates the butterfly valve 8 to the opening posture in STEP11. It is determined whether or not it has been detected.

  When the open detector 86 detects the rotation of the butterfly valve 8 to the open position, it is determined in STEP 12 whether or not the detected water amount of the water amount sensor 2b is equal to or more than a specified amount. If the temperature falls below the predetermined value, the on-off valve 6 is closed in STEP 13 to extinguish the burner 1, and the process returns to STEP 3. If the detected water amount is equal to or larger than the specified amount during the hot water supply, it is determined in STEP 14 whether or not to switch to the small capacity state, that is, whether or not the required combustion amount has fallen below the minimum combustion amount obtained in the large capacity state. Determine. If the state should be switched to the small capacity state, the stepping motor 82 is driven in the closing direction by the number of steps corresponding to the closing origin position in STEP 15, and then the closing detector 85 moves to the closing origin position of the butterfly valve 8 in STEP 16. It is determined whether or not the rotation is detected, and if it is detected, it is determined in STEP 17 whether or not the detected water amount of the water amount sensor 2b is equal to or more than a specified amount. If the detected water amount falls below the specified amount at the end of hot water supply, the on-off valve 6 is closed in STEP 18 to extinguish the burner 1, and the process returns to STEP 7. If the detected water amount is equal to or more than the specified amount during the hot water supply, the process returns to STEP9. If it is not determined in STEP 9 that the state should be switched to the high capacity state, the process directly proceeds from STEP 9 to STEP 17.

  When the open detector 86 does not detect the rotation of the butterfly valve 8 to the open posture in STEP 11, or when the close detector 85 does not detect the rotation of the butterfly valve 8 to the closed side origin position in STEP 16 In step 19, the on-off valve 6 is closed in step 19 to extinguish the fire of the burner 1 and then abnormally stopped in step 20.

  According to the above control, when the water amount detected by the water amount sensor 2b becomes equal to or more than the specified amount in a state where the butterfly valve 8 is rotated to the close side origin position, the process proceeds to STEP8 and the ignition operation of the burner 1 is performed. If the close detector 85 does not detect the rotation of the butterfly valve 8 to the close-side origin position in STEP 4, the process does not proceed to STEP 8, and the ignition operation is prohibited. Here, the origin position on the closing side of the butterfly valve 8 is a position outside the detection angle range of the close detector 85 when the ambient temperature is lower than the predetermined temperature, so that the cold temperature at which the ambient temperature becomes lower than the predetermined temperature may cause freezing. Sometimes, even if the butterfly valve 8 is rotated to the close-side origin position, this is not detected by the close detector 85, and the ignition operation of the burner 1 is prohibited. Therefore, even if the water amount sensor 2b fails, ignition of the burner 1 in a frozen state can be prevented, and fail-safe can be achieved.

  As described above, the embodiments of the present invention have been described with reference to the drawings. However, the present invention is not limited to these embodiments, and can be implemented with various modifications without departing from the spirit of the present invention.

A: Premixing device, 1: Burner, 2: Heat exchanger for hot water supply, 3: Fan, 4: Air supply path, 41: Gas suction section, 5: Gas supply path, 7: Flow control valve, 8: Butterfly valve , 82 ... stepping motor, 85 ... close detector, 9 ... switching valve, 10 ... interlocking mechanism.

Claims (1)

A premixing device that mixes a fuel gas with air and supplies the mixture to a burner serving as a heat source of a heat exchanger for hot water supply via a fan,
Is connected to the gas suction part downstream end is provided on an air supply passage upstream of the fan of a gas supply passage which is interposed a flow control valve for supplying the fuel gas, the air supply upstream of the gas suction portion includes air resistance switching means for switching the air flow resistance of the portion of the road to the magnitude, and a gas resistance switching means for switching the magnitude of the flow resistance of the portion of the gas supply path on the downstream side of the flow control valve,
The air resistance switching means, than said gas suction unit provided in the portion of the air supply path upstream, close to perpendicular to the longitudinal direction of the air supply passage and an open posture parallel to the longitudinal direction of the air supply passage consists of a rotatable butterfly valve and attitude, the gas resistance switching means is composed of a switching valve which is provided to be freely opened and closed to the gas supply path,
A stepping motor for rotating the butterfly valve, the interlock mechanism for opening and closing the switching valve in conjunction with the rotation of the closing position and opening position of the butterfly valve, the rotation of the closing position of the butterfly valve And a closed detector comprising a detectable Hall IC,
Detection angle range with decreasing ambient temperature is determined based on the temperature characteristics of the Hall IC to become narrower, it is lower than a predetermined temperature outside the detection angle range of the closing knowledge unit, the closed detection at the predetermined temperature or higher setting a predetermined rotational angle of the closed position near the detection angle range to become the butterfly valve of the vessel to the closing side origin position, of the burner in a state in which the butterfly valve is rotated to the closing side origin position said performs an ignition operation, but premixing apparatus characterized by prohibiting the ignition operation when the closing knowledge unit does not detect the rotation of the said closed side origin position of the butterfly valve.

Images