JP6309861B2 - Combustion device - Google Patents

Description

  The present invention relates to a burner unit having a plurality of burners, a combustion fan for supplying combustion air to the burner unit, a proportional valve provided in a gas supply path for supplying fuel gas to the burner unit, and a downstream of the proportional valve Controlling the combustion fan, proportional valve, and capacity switching valve, which is provided in the gas supply path on the side, changes the combination of the burners that supply fuel gas, and switches the combustion capacity of the entire burner unit to multiple stages. And a control device.

  In this type of combustion apparatus, the control means performs control to vary the rotation speed of the combustion fan and the proportional valve current energized to the proportional valve according to the required combustion amount, and the required combustion amount is proportional to the current combustion capacity. When the combustion amount of the burner unit obtained when the valve current is set to the upper limit value is exceeded, the capacity increase control is performed to increase the combustion capacity by one step, and the required combustion amount is the lower limit of the proportional valve current with the current combustion capacity. When the value is lower than the combustion amount of the entire burner unit obtained when the value is set, the capacity reduction control is performed to lower the combustion capacity by one stage.

  Here, the lower limit value and upper limit value of the proportional valve current are the lower limit values of the proportional valve current with the combustion capacity of the burner unit as a whole higher by one stage when the proportional valve current is set to the upper limit value with the combustion capacity of each stage. It is set to exceed the combustion amount of the burner unit as a whole. As a result, the combustion amount range obtained on one side of the adjacent combustion capacities in the capacity ranking partially overlaps with the combustion amount range obtained on the other side (hereinafter, the overlapping combustion amount range is referred to as an overlap allowance). Once the capacity increase control is performed, the capacity decrease control is not performed unless the required combustion amount is reduced more than the allowance, and the capacity increase control and the capacity decrease control are repeated in a short time due to a minute change in the required combustion amount ( Hunting) is prevented. When hunting occurs, the temperature of the hot water becomes unstable and noise due to frequent opening and closing of the capacity switching valve is generated. Therefore, it is desirable to prevent hunting as much as possible.

  By the way, in the burner that newly supplies the fuel gas by the capacity increase control, the flame lift tends to occur until the temperature of the flame opening increases. Therefore, until the predetermined time elapses after the capacity increase control is performed, the flame holding amount is increased so that the proportional valve current is larger than the value corresponding to the required combustion amount while maintaining the rotation speed of the combustion fan at the value corresponding to the required combustion amount. A device that performs control is also known. According to this, the fuel concentration of the air-fuel mixture ejected from the burner becomes high, and it is possible to prevent the flame lift in the burner that newly supplies the fuel gas by the capacity increase control.

  However, during the flame holding increase control, the lower limit value of the proportional valve current is corrected to increase, and the lower limit of the combustion amount obtained by the combustion capacity after the capacity increase is increased by the increase in the lower limit value of the proportional valve current. For this reason, during the flame holding increase control, the overlap is reduced, and hunting is likely to occur.

  Therefore, conventionally, according to Patent Document 1, the elapsed time from the capacity down control to the capacity up control between the predetermined combustion capacity other than the maximum combustion capacity and the combustion capacity one step higher than that is less than the predetermined set time. It is known that the flame holding increase control is prohibited when it becomes. If flame holding increase control is prohibited, the lower limit of the combustion amount obtained by the combustion capacity after the capacity increase control is maintained at a relatively low value immediately after the capacity increasing control and after the flame holding increase control ends, and the overlap allowance increases. , The occurrence of hunting can be suppressed.

  By the way, instead of the above-described flame holding increase control until a predetermined time has elapsed since the capacity increase control, the proportional valve current is maintained at a value corresponding to the required combustion amount, and the rotational speed of the combustion fan is changed to the required combustion amount. It is also known that flame holding control is performed so that the fuel concentration of the air-fuel mixture ejected from the burner is increased to a value lower than the value corresponding to the above. According to this, the lower limit value of the proportional valve current is not corrected to be increased by the flame holding control, and the overlap margin is not reduced during the flame holding control.

  However, if the number of revolutions of the combustion fan is reduced by flame holding control, the amount of surplus air that reaches the heated object without contributing to combustion decreases, the thermal efficiency becomes relatively high, and The change width of the heating amount is relatively large. Therefore, during the flame holding control, hunting is likely to occur even if the overlap margin is not reduced.

JP2013-245887A

  This invention makes it the subject to provide the combustion apparatus which enabled it to suppress generation | occurrence | production of the hunting during flame holding control in view of the above point.

  In order to solve the above problems, the present invention provides a burner unit having a plurality of burners, a combustion fan for supplying combustion air to the burner unit, and a proportionality provided in a gas supply path for supplying fuel gas to the burner unit. A capacity switching valve that is provided in a portion of the gas supply path downstream of the valve and the proportional valve, changes the combination of the burner for supplying fuel gas, and switches the combustion capacity of the entire burner unit to a plurality of stages, a combustion fan, A combustion apparatus having a control means for controlling a proportional valve and a capacity switching valve, wherein a lower limit value and an upper limit value of a proportional valve current energized to the proportional valve are set to an upper limit value with the combustion capacity of each stage. The combustion amount of the entire burner unit is set to exceed the combustion amount of the entire burner unit when the proportional valve current is set to the lower limit value with a combustion capacity one stage higher than that, and the control means includes a combustion fan In addition to performing control to vary the rotation speed and proportional valve current according to the required combustion amount, the required combustion amount exceeds the combustion amount of the entire burner unit obtained when the proportional valve current is set to the upper limit with the current combustion capacity. When the required combustion amount falls below the combustion amount of the entire burner unit obtained when the required combustion amount is the current combustion capability and the proportional valve current is set to the lower limit value, The capacity down control is performed to reduce the combustion capacity by one step, and the proportional valve current is maintained at a value corresponding to the required combustion amount until the predetermined time has elapsed since the capacity up control is performed, and the rotational speed of the combustion fan is required. In the configuration that performs flame holding control that is lower than the value corresponding to the combustion amount, the lower limit value of the proportional valve current is set lower during flame holding control than when flame holding control is not executed. To do And butterflies.

  According to the present invention, since the lower limit value of the proportional valve current is reduced during flame holding control, the overlap is increased only by that portion. Thereby, the hunting which is easy to occur during the flame holding control can be effectively suppressed.

The schematic diagram which shows the structure of the combustion apparatus of embodiment of this invention. The graph which showed the combustion characteristic line showing the relationship between the combustion amount of the whole burner unit, and fan rotation speed about the combustion capacity of each stage.

  FIG. 1 shows a combustion apparatus according to an embodiment of the present invention comprising a hot water supply heat source unit. This combustion apparatus includes a combustion housing 1. A burner unit 2 and a hot water heat exchanger 3 are housed in the lower and upper portions of the combustion housing 1, respectively, and combustion is performed on the lower surface of the combustion housing 1 to supply combustion air to the burner unit 2. A fan 4 is connected. And the water from the water supply pipe | tube 3a of the upstream of the heat exchanger 3 is heated with the combustion gas from the burner unit 2, and the hot water heated by predetermined | prescribed preset temperature to the hot water discharge pipe | tube 3b of the downstream of the heat exchanger 3 is received. I try to get hot water out. The combustion gas that has passed through the heat exchanger 3 is discharged to the outside from an exhaust port 1 a opened at the top of the combustion housing 1.

The burner unit 2 has first to third three burners 2 ₁ , 2 ₂ , 2 ₃ . In this embodiment, a total of 15 unit burners 2a are juxtaposed, the first burner 2 ₁ with three unit burners 2a, the second burner 2 ₂ with five unit burners 2a, and the remaining seven units. constitute a third burner _{2 3} burner 2a. Each burner 2 ₁ , 2 ₂ , 2 ₃ is not composed of each predetermined number of unit burners 2 a, but each burner 2 ₁ , 2 is composed of one burner having the same combustion capacity as the predetermined number of unit burners 2 a. It is also possible to configure ₂ and 2 ₃ .

A gas supply path 5 for supplying fuel gas to the burner unit 2 is provided with a main valve 6 composed of an electromagnetic on-off valve and a proportional valve 7 on the downstream side thereof. The portion of the gas supply path 5 on the downstream side of the proportional valve 7, the first branch passage 5 ₁ connected to the first burner 2 _1, and the second branch passage 5 ₂ leading to the second burner 2 _2, third burner is branched into a third branch channel 5 ₃ leading to 2 _3. The first to third branching passages 5 ₁ , 5 ₂ , and 5 ₃ are provided with first to third ability switching valves 8 ₁ , 8 ₂ , and 8 _{3 that} are electromagnetic on-off valves, respectively. And the combination of the burner that supplies fuel gas is changed by opening and closing the _{first to} third capacity switching valves 8 ₁ , 8 ₂ , and 8 ₃ so that the combustion capacity of the entire burner unit 2 is switched to a plurality of stages. .

In detail, by supplying fuel gas only to the first burner 2 ₁ by opening the first capacity switching valve _81, the lowest first stage of capacity burner unit 2 total combustion capacity ( switching the unit burners 3 duty capacity), by supplying the fuel gas only in the second burner 2 ₂ by opening the second capacity switching valve _82, the whole burner unit 2 burning ability of the second stage Switch to capacity (capacity equivalent to 5 unit burners), open both first and second capacity switching valves 8 ₁ , 8 ₂ , and supply fuel gas to both first and second burners 2 ₁ , 2 ₂ By supplying, the combustion capacity of the entire burner unit 2 is switched to the third stage capacity (capacity of eight unit burners), and both the first and third capacity switching valves 8 ₁ and 8 ₃ are opened. By supplying fuel gas to both the first and third burners 2 ₁ , 2 ₃ , the entire burner unit 2 Is switched to the fourth stage capacity (capacity of 10 unit burners), the first to third capacity switching valves 8 ₁ , 8 ₂ , 8 ₃ are opened and the first to third burners 2 ₁ are opened. , 2 ₂ , and 2 ₃ , the combustion capacity of the entire burner unit 1 is switched to the highest fifth stage capacity (capacity of 15 unit burners).

The combustion apparatus further includes a controller 9 comprising a microcomputer as control means for controlling the combustion fan 4, the main valve 6, the proportional valve 7, and the capacity switching valves 8 ₁ , 8 ₂ , and 8 ₃ . The controller 9 calculates a required combustion amount (combustion amount required to discharge hot water at a set temperature) according to the hot water supply load, and the first to third capacity switching valves 8 ₁ , 8, 8 ₂ and 8 ₃ are opened and closed to switch the combustion capacity of the burner unit 2 as a whole. A combustion amount equal to the required combustion amount is obtained with the switched combustion capability, and an appropriate amount of air corresponding to this combustion amount is obtained. Is controlled such that the rotational speed of the combustion fan 4 and the proportional valve current energized to the proportional valve 7 are varied according to the required combustion amount.

  The rotation speed of the combustion fan 4 is feedback-controlled so as to become the target rotation speed corresponding to the required combustion amount, the rotation speed of the combustion fan 4 is detected, and the proportional valve current is set to be proportional to the detected rotation speed. Variable so-called fan advance control may be performed. Even in this case, the proportional valve current is variably controlled according to the required amount of combustion, although indirectly, and is included in the present invention.

  FIG. 2 shows a combustion characteristic line representing the relationship between the combustion amount obtained by the combustion capacity of each stage and the rotational speed of the combustion fan 4 (fan rotational speed). This combustion characteristic line is the capacity of the first stage. Is line L1, the second stage capacity is line L2, the third stage capacity is line L3, the fourth stage capacity is line L4, and the fifth stage capacity is line L5. Here, the lower limit value of the proportional valve current corresponding to the lower limit value Nmin of the fan speed and the upper limit value of the proportional valve current corresponding to the upper limit value Nmax of the fan speed are the upper limit value of the proportional valve current by the combustion capacity of each stage. Combustion capacity of the entire burner unit 2 is set to be higher than the combustion quantity of the entire burner unit 2 when the proportional valve current is set to the lower limit with a combustion capacity one step higher than that, and adjacent combustion performance ranks. There will be an overlap W between abilities.

  Then, when the required combustion amount exceeds the combustion amount of the entire burner unit 2 obtained when the required combustion amount is the current combustion capacity and the proportional valve current is set to the upper limit value (fan rotation speed is the upper limit value Nmax), The capacity increase control is performed to increase the capacity by one step, and the combustion amount of the entire burner unit 2 obtained when the required combustion amount is the current combustion capability and the proportional valve current is set to the lower limit value (fan rotation speed is the lower limit value Nmin). When it falls below, capacity down control is performed to lower the combustion capacity by one step. According to this, once the capacity reduction control is performed, the capacity increase control is not performed unless the required combustion amount increases by the overlap allowance W or more, and once the capacity increase control is performed, the required combustion amount is reduced to the overlap allowance W. Unless the capacity is reduced, the capacity reduction control is not performed, and a phenomenon (hunting) in which the capacity increase control and the capacity reduction control are repeated in a short time due to a minute change in the required combustion amount is suppressed.

  In addition, the controller 9 further prevents the proportional lift current until a predetermined time (for example, 90 seconds) elapses after the performance increase control is performed in order to prevent a flame lift in the burner that supplies new fuel gas by the capacity increase control. While maintaining the value corresponding to the required combustion amount, flame holding control is performed so that the fan rotational speed is lower than the value corresponding to the required combustion amount, and the fuel concentration of the air-fuel mixture ejected from the burner is increased. A line L2 ′ in FIG. 2 indicates a combustion characteristic line during the flame holding control after the capacity increase control from the first stage combustion capacity to the second stage combustion capacity.

  By the way, the overlap allowance W becomes smaller as the combustion capacity becomes lower. Further, if the fan rotation speed is lowered by flame holding control, the amount of surplus air reaching the heat exchanger 3 without contributing to the combustion is reduced, the thermal efficiency becomes relatively high, and the change width of the hot water supply temperature with respect to the change in the combustion amount. Is relatively large. Therefore, hunting is likely to occur during the flame holding control during the capacity increase to the second stage combustion capacity, coupled with the fact that the overlap allowance W is relatively small.

  Therefore, in this embodiment, the lower limit value of the proportional valve current is set lower by a predetermined value during flame holding control when the capacity is increased to the second stage combustion capacity than when flame holding control is not executed. ing. According to this, the lower limit of the line L2 ′ in FIG. 2 is displaced from the point A to the point A ′. Therefore, during the flame holding control, the overlap margin between the first stage combustion capacity and the second stage combustion capacity increases from W to W ′, and hunting can be effectively suppressed.

  Note that if the lower limit value of the proportional valve current is lowered, there is a risk that the flame approaches the burner at the upper end of the burner and the burner overheats. However, since the flame holding control is only performed for a predetermined time at the beginning of the capacity increase control, if the lower limit value of the proportional valve current is lowered only during the flame holding control, the burner does not overheat.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to this. For example, in the above embodiment, the overlap allowance W becomes so small that the hunting is likely to occur only between the combustion capacities of the first stage and the second stage. The lower limit value of the proportional valve current is lowered only during the control, but the lower limit value of the proportional valve current is also lowered during the flame holding control when the capacity is increased to the third to fifth stage combustion capacity. May be.

  Moreover, although the said embodiment applies this invention to the combustion apparatus which consists of the hot water supply heat source machine which has the heat exchanger 3 for hot water supply, even if it is a combustion apparatus for uses other than hot water supply, such as for heating, The present invention can be similarly applied as long as the combustion capacity is switched by a combination of burners for supplying fuel gas.

2 ... Burner unit, 2 ₁ , 2 ₂ , 2 ₃ ... Burner, 4 ... Combustion fan, 5 ... Gas supply path, 7 ... Proportional valve, 8 ₁ , 8 ₂ , 8 ₃ ... Capacity switching valve, 9 ... Controller (control) means).

Claims (1)

A burner unit having a plurality of burners, a combustion fan for supplying combustion air to the burner unit, a proportional valve provided in a gas supply path for supplying fuel gas to the burner unit, and a gas supply downstream of the proportional valve A capacity switching valve that is provided in the passage and changes the combination of the burners for supplying fuel gas to switch the combustion capacity of the entire burner unit to a plurality of stages; and a control means for controlling the combustion fan, proportional valve and capacity switching valve A combustion apparatus comprising:
The lower limit value and upper limit value of the proportional valve current energized to the proportional valve are the proportional valve current with the combustion capacity of the burner unit as a whole higher by one stage when the proportional valve current is the upper limit value with the combustion capacity of each stage. Is set to exceed the combustion amount of the entire burner unit when
The control means performs control to vary the rotation speed of the combustion fan and the proportional valve current in accordance with the required combustion amount, and a burner obtained when the required combustion amount sets the proportional valve current to the upper limit value with the current combustion capacity. Combustion of the entire burner unit, which is obtained when the required combustion amount is the current combustion capability and the proportional valve current is set to the lower limit when the combustion amount of the entire unit exceeds the combustion amount. When the quantity falls below the limit, the capacity reduction control is performed to lower the combustion capacity by one step, and further, the proportional valve current is maintained at a value corresponding to the required combustion amount until a predetermined time elapses after the capacity increase control is performed. In what is configured to perform flame holding control to lower the rotational speed of the combustion fan than the value according to the required combustion amount,
A combustion apparatus characterized in that the lower limit value of the proportional valve current is set lower during flame holding control than when flame holding control is not executed.

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