JP7399463B2 - Water heater - Google Patents

Description

The present invention relates to a water heater equipped with a premixer that generates a mixture of fuel gas and combustion air through rotation of a fan.

As disclosed in Patent Document 1, water heaters are known that are equipped with a premixer upstream of a burner that generates a mixture of fuel gas and combustion air by rotating a fan. . This premixer is partitioned into two venturis that supply fuel gas and combustion air in a branched manner, and by opening and closing one of the venturis with a butterfly valve, the combustion amount of the burner can be divided into two stages: large and small. It is switchable. A solenoid valve is provided in the gas supply path to the premixer, and its opening and closing are controlled by the controller together with the butterfly valve. This solenoid valve may be provided only in the gas supply path to one venturi side that is opened and closed by the butterfly valve.

US Patent Application Publication No. 2011/139045

If a solenoid valve is provided only on one venturi side, when switching the combustion stage of the burner from 1st stage to 2nd stage (small → large), the butterfly valve is moved from the closed position to the open position, and the solenoid valve is The valve will also be opened.
However, if the solenoid valve opens too late than the butterfly valve opens, a so-called air-rich condition will occur, and conversely, if the solenoid valve opens too early than the butterfly valve, , there is a possibility that a so-called gas-rich (excessive fuel gas) state occurs, and the combustion state deteriorates instantaneously, causing a misfire. This can also occur when switching the combustion stage from two stages to one stage (large → small).

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a water heater that can prevent deterioration of the combustion state when switching the combustion stage of a burner.

In order to achieve the above object, the invention according to claim 1 includes a premixer for generating a mixture of air and fuel gas through a fan and supplying the mixture to a burner; Equipped with a controller that controls the combustion of
The premixer has two venturis through which air flows through the rotation of a fan, and fuel gas is supplied to each via a branch pipe branched from a gas supply path.
a butterfly valve capable of opening and closing one of the venturis;
Equipped with a solenoid valve that can open and close one branch pipe that connects to one venturi,
A water heater in which a controller can switch the combustion amount of a burner into two stages, large and small, by opening and closing a butterfly valve and a solenoid valve,
The controller sets a solenoid valve opening/closing position for opening and closing the solenoid valve between the open and closed positions of the butterfly valve, and makes the butterfly valve wait at the solenoid valve opening/closing position before igniting the burner. When igniting the burner, the butterfly valve is moved from the solenoid valve opening/closing position to the valve opening or closing position depending on the combustion amount, and when the butterfly valve is opened/closed, the butterfly valve passes through the solenoid valve opening/closing position. It is characterized by opening and closing the solenoid valve at the appropriate timing.

According to the first aspect of the invention, when opening and closing the butterfly valve, the controller opens and closes the solenoid valve at the timing when the butterfly valve passes through the solenoid valve opening and closing position. Therefore, air richness and gas richness are less likely to occur, and deterioration of the combustion state when switching the combustion stage of the burner can be prevented.
Further, the controller causes the butterfly valve to wait at the solenoid valve open/close position before igniting the burner, and moves the butterfly valve from the solenoid valve open/close position to the valve open position or the valve close position depending on the amount of combustion when the burner is ignited. Therefore, regardless of the amount of combustion in the burner, the butterfly valve will not become stuck during ignition of the burner and will not operate normally or cause an ignition delay.

It is a schematic diagram of a water heater. FIG. 3 is a longitudinal cross-sectional view of the mixing cylinder.

Embodiments of the present invention will be described below based on the drawings.
FIG. 1 is a schematic diagram showing an example of a water heater. In this water heater 1, a burner 3 is arranged above a combustion chamber 2 with the combustion surface facing downward, and below the burner 3 is a primary heat exchanger 4 that mainly recovers sensible heat from combustion exhaust. It is a reverse combustion type in which a secondary heat exchanger 5 is arranged to recover latent heat. The burner 3 is a mesh burner having a flame hole plate on the lower surface in which a large number of flame holes are formed.
A premixer 7 is provided upstream of the gas supply pipe 6 to the burner 3 . The premixer 7 includes a fan 8 on the downstream side and two venturis 9A and 9B on the upstream side. The venturi 9B is opened and closed by a butterfly valve 10. Air suction ports 11A and 11B are provided upstream of the venturis 9A and 9B, respectively.
Branch pipes 12A and 12B branching from the gas supply pipe 6 are connected to the downstream sides of the suction ports 11A and 11B in the venturis 9A and 9B, respectively. The branch pipe 12B is provided with a solenoid valve 13 that opens and closes the gas flow path to the venturi 9B. A pressure equalizing valve 14 is provided on the upstream side of the branch pipes 12A, 12B in the gas supply pipe 6.

A water supply pipe 15 is connected to an inlet end of the secondary heat exchanger 5 , and an outlet end of the secondary heat exchanger 5 is connected to an inlet end of the primary heat exchanger 4 . A hot water outlet pipe 16 is connected to the outlet end of the primary heat exchanger 4 . A bypass pipe 17 is connected between the water supply pipe 15 and the hot water outlet pipe 16 outside the combustion chamber 2 .
The water supply pipe 15 is provided with a water flow sensor 18, an inlet water temperature sensor 19, and a water flow adjustment valve 20. The hot water outlet pipe 16 is provided with an outlet temperature sensor 21 that detects the temperature near the outlet from the primary heat exchanger 4, and an outlet temperature sensor 22 that detects the temperature downstream from the connection part with the bypass pipe 17. . The bypass pipe 17 is provided with a bypass valve 23 that adjusts the bypass flow rate.

A drain discharge pipe 24 equipped with a neutralizer 25 is connected to the combustion chamber 2 . Further, an exhaust duct 26 is connected to the combustion chamber 2 to open the downstream end to the outdoors. Furthermore, the combustion chamber 2 is provided with an igniter 27 for igniting the burner 3 and a flame rod 28 for flame detection.
The water heater 1 includes a controller that controls the combustion of the burner 3 and the rotation of the fan 8 based on detection signals obtained from each sensor, and executes outlet hot water temperature control to match the outlet temperature to the set temperature set by the remote controller 31. It is equipped with 30.

The premixer 7 consists of a fan case (not shown) that accommodates the fan 8 and a mixing cylinder attached to the lower part of the fan case. FIG. 2 shows details of the mixing cylinder 40. The mixing cylinder 40 includes a lower cylinder part 41 which opens air suction ports 11A and 11B at the lower end, and an expanded upper cylinder which is connected coaxially from the upper end of the lower cylinder part 41 and whose diameter increases as it goes upward. 42. A pressure reducing part 43 having a small passage area is formed in the lower cylinder part 41 through which air sucked from the suction ports 11A and 11B passes.
A partition wall 44 in the vertical direction is formed in the mixing cylinder 40 from the lower cylinder part 41 to the pressure reducing part 43 and the lower part of the upper cylinder part 42, dividing the inside of the mixing cylinder 40 into two left and right. However, the partition wall 44 is arranged at a position eccentric to one side from the axis of the mixing cylinder 40, and inside the mixing cylinder 40 is a venturi 9A that vertically penetrates the left side of the partition wall 44 in FIG. A venturi 9B is formed that passes vertically through the right side of the.

Further, a butterfly valve 10 is provided above the partition wall 44 within the upper cylinder portion 42 . This butterfly valve 10 is a semicircular plate body with a seal plate 45 fixed to the back surface, and support parts 46, 46 provided at both the front and rear ends of the lower end are rotatably held above the partition wall 44. A U-shaped valve seat 47 is formed on the venturi 9B side of the upper cylinder portion 42 and slopes upward from the upper end of the partition wall 44 to the right.
A valve drive motor (not shown), which is a stepping motor, is provided on the back side of the mixing cylinder 40, and the shaft of the motor (not shown) is connected to a support portion 46 on the rear side. Therefore, due to the rotation of the valve drive motor, the butterfly valve 10 is moved to the open position A where it extends upwardly from the partition wall 44 to open the venturi 9B as shown by the solid line in FIG. The seal plate 45 is tilted until it abuts against the valve seat 47, and can swing between a valve closing position B in which the venturi 9B is closed.

However, before the burner 3 is ignited, the butterfly valve 10 is brought to a standby position C, which is intermediate between the valve open position A and the valve closed position B, by the valve drive motor, as shown by the two-dot chain line. ing. This standby position C also serves as a position (electromagnetic valve opening/closing position) at which the solenoid valve 13 is opened and closed when the burner 3 switches the combustion stage during combustion.
In the mixing cylinder 40, between the upper end of the lower cylinder part 41 and the upper end of the pressure reducing part 43, communication passages 48A and 48B are formed which communicate with the branch pipes 12A and 12B and open toward the upper cylinder part 42, respectively. has been done.

In the water heater 1 configured as described above, when water is passed into the appliance, the controller 30 drives the fan motor to rotate the fan 8 at a rotation speed corresponding to the amount of combustion requested by the remote controller 31. At this time, if the combustion amount is equal to or higher than a predetermined threshold, it is assumed that 2-stage (large combustion amount) ignition is being performed, and the solenoid valve 13 is opened, the valve drive motor is controlled, and the butterfly valve 10 is put on standby. Move from position C to valve open position A to open venturi 9B. Since the butterfly valve 10 is not located at the closed position B, it can smoothly move to the open position A without sticking.
Then, in the mixing cylinder 40, air proportional to the rotation speed of the fan 8 is sucked from below the lower cylinder part 41 from the suction ports 11A and 11B, and flows on the left side of the partition wall 44 as shown by the dotted line arrow in FIG. The air is branched into air A1 and air A2 flowing on the right side, which flow to the upper cylinder portion 42 through venturis 9A and 9B, respectively. At this time, the air A1 and A2 passing through the venturis 9A and 9B increase the flow velocity and flow toward the upper cylinder part 42 due to the reduction in the passage area of the pressure reducing part 43, so that negative pressure is generated.

At the same time, a main valve (not shown) is opened in the gas supply pipe 6 to supply fuel gas, which passes through the pressure equalization valve 14 and branches into branch pipes 12A and 12B. Therefore, from the communication passages 48A, 48B, as shown by the solid line in FIG. 2, gas G1, G2 in an amount corresponding to the pressure difference between the venturis 9A and 9B and the negative pressure generated is sucked into the upper cylinder part 42. Here, it is mixed with air A1 and A2 to generate an air-fuel mixture.

On the other hand, if the required combustion amount is less than a predetermined threshold, it is assumed that 1st stage (lower combustion amount) ignition is performed, and the valve drive motor is controlled to move the butterfly valve 10 from the standby position C to the valve closing position B. to close Venturi 9B. Since the butterfly valve 10 is not located at the open position A, it can be quickly moved to the closed position B.
Therefore, the air sucked in by the fan 8 is only the air A1 that passes through the venturi 9A. Moreover, the fuel gas flows into the communication path 48A only from the branch pipe 12A.
Then, from the communication passage 48A, an amount of gas G1 corresponding to the pressure difference between the gas G1 and the negative pressure generated in the venturi 9A is sucked into the upper cylinder portion 42, where it is mixed with air A1 to generate an air-fuel mixture.

The air-fuel mixture thus generated in the mixing cylinder 40 is sucked into the fan case, sent to the burner 3, jetted out from each flame hole in the flame hole plate, and ignited by the igniter 27 to be combusted.
The combustion exhaust gas from the burner 3 passes between the fins of the primary heat exchanger 4, thereby exchanging heat with the water flowing in the heat transfer tubes, and recovering sensible heat. Thereafter, by passing through the secondary heat exchanger 5, heat is exchanged with the water flowing through the internal flow path, and latent heat is recovered. Then, it rises inside the exhaust duct 26 and is discharged outdoors.
Thereafter, the controller 30 controls the rotation speed of the fan 8 and the combustion stage switching of the burner 3 based on the difference between the hot water temperature obtained from the hot water temperature sensor 22 and the set temperature set by the remote controller 31. .

Here, when switching the combustion stage of the burner 3 from the 1st stage to the 2nd stage, the controller 30 controls the valve drive motor to move the butterfly valve 10 from the valve closing position B to the valve opening position A to open the venturi 9B. Open. At this time, the controller 30 opens the solenoid valve 13 at the timing when the butterfly valve 10 passes through a standby position C between the valve open position A and the valve closed position B. This timing can be ascertained from the pulse signal that controls the valve drive motor.
On the other hand, when switching the combustion stage of the burner 3 from the second stage to the first stage, the controller 30 controls the valve drive motor to move the butterfly valve 10 from the open position A to the closed position B and close the venturi 9B. do. At this time as well, the controller 30 closes the solenoid valve 13 at the timing when the butterfly valve 10 passes through the standby position C. This timing can also be determined from the pulse signal that controls the valve drive motor.
In this way, the solenoid valve 13 opens and closes at the timing when the butterfly valve 10 passes the standby position C, so the timing at which air and fuel gas are supplied does not deviate significantly, and so-called air rich or gas rich is less likely to occur.

Thus, according to the water heater 1 of the above embodiment, the controller 30 is located at a standby position between the open position A and the closed position B of the butterfly valve 10, where the butterfly valve 10 waits before igniting the burner 3. C is set, and when the burner 3 is ignited, the butterfly valve 10 is moved from the standby position C to the valve open position A or the valve closed position B depending on the combustion amount.
With this configuration, regardless of the combustion stage of the burner 3, when the burner 3 is ignited, the butterfly valve 10 will not become stuck and not operate normally or cause an ignition delay.

In addition, the controller 30 sets a standby position C (solenoid valve opening/closing position) in which the solenoid valve 13 is opened/closed between the open position A and the closed position B of the butterfly valve 10 , and opens/closes the butterfly valve 10 . When operating, the solenoid valve 13 is opened and closed at the timing when the butterfly valve 10 passes the standby position C.
With this configuration, air richness and gas richness are less likely to occur, and deterioration of the combustion state when switching the combustion stage of the burner 3 can be prevented.

In addition, in the above embodiment, the standby position of the butterfly valve (the solenoid valve opening/closing position) is set midway between the valve opening position and the valve closing position, but it does not have to be exactly in the middle; The standby position (electromagnetic valve opening/closing position) may be set at a position close to either of the two positions.
Further, the closing side of the butterfly valve may be on the opposite side (the left side in FIG. 2). In this case, the solenoid valve is also provided in the branch pipe on the valve-closing side.
Furthermore, the present invention is also applicable to water heaters in which the premixer is located downstream of the fan.
In addition, the present invention is applicable not only to reverse combustion type water heaters but also to water heaters with a primary heat exchanger and a secondary heat exchanger installed above the burner, or water heaters without a secondary heat exchanger. It is possible.

1. Water heater, 2. Combustion chamber, 3. Burner, 4. Primary heat exchanger, 5. Secondary heat exchanger, 6. Gas supply pipe, 7. Premixer, 8.・Fan, 9A, 9B... Venturi, 10... Butterfly valve, 11A, 11B... Suction port, 12A, 12B... Branch pipe, 13... Solenoid valve, 15... Water supply pipe, 16... Hot water outlet pipe, 17...Bypass pipe, 18...Water flow sensor, 19...Incoming water temperature sensor, 21...Outlet temperature sensor, 22...Output hot water temperature sensor, 26...Exhaust duct, 30...Controller, 31...Remote controller, 40 ...Mixing tube, 41.. Lower cylinder portion, 42.. Upper cylinder portion, 44.. Partition wall, 48A, 48B.. Communication path.

Claims (1)

A premixer for generating a mixture of air and fuel gas through a fan and supplying the mixture to a burner, and a controller for controlling operation of the fan and combustion of the burner,
The premixer has two venturis through which air flows due to the rotation of the fan and to which fuel gas is respectively supplied via branch pipes branched from the gas supply path;
a butterfly valve that can open and close the one venturi;
comprising a solenoid valve capable of opening and closing one of the branch pipes connected to the one venturi,
A water heater in which the controller can switch the combustion amount of the burner into two stages, large and small, by opening and closing the butterfly valve and the electromagnetic valve,
The controller sets a solenoid valve opening/closing position for opening/closing the solenoid valve between an open position and a valve closing position of the butterfly valve, and before igniting the burner, the solenoid valve opens/closes at the solenoid valve opening/closing position. The butterfly valve is kept on standby, and when the burner is ignited, the butterfly valve is moved from the solenoid valve opening/closing position to the valve opening position or the valve closing position according to the combustion amount, and when the butterfly valve is opened/closed. The water heater is characterized in that the solenoid valve is opened and closed at the timing when the butterfly valve passes through the solenoid valve opening and closing position.

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