JPH06288534A - Combustion control device - Google Patents

Abstract

PURPOSE:To prevent an abnormal sound from being produced owing to combustion upon required heat being altered. CONSTITUTION:Target revolutions of a fan 24 determined in response to a required heat amount of a required heat amount of a required heat amount calculation unit 42 and operation revolutions of the fan 24 detected by a revolution detection unit 46 are compared with each other. When the target revolutions are larger than the operation revolutions by predetermined revolutions or more, intermediate revolutions between the target revolutions and the operation revolutions are taken as control revolutions only for a predetermined time and thereafter the target revolutions are taken as the control revolutions to drive the fan 24. When a rotational difference between the target revolutions and the operation revolutions is smaller than predetermined revolutions, the target revolutions to drive the fan 24 while supplying electric power to a proportional valve 21 in response to the operation revolutions. The revolutions of the fan 24 are brought into two stages in such a manner and a change rate of the revolutions is slowed down, so that a difference between a delayed change of opening of the proportional valve 21 and the change rate is reduced to ensure a proper air/fuel ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control device equipped with a blower for supplying combustion air to a burner.

[0002]

2. Description of the Related Art In a burner such as a water heater, in order to obtain a stable combustion state in a burner, a blower that supplies combustion air to the burner and a proportional valve that controls a gas supply amount are used. It is necessary to match the control states, and for that purpose, for example, the blower is controlled according to the required heat amount calculated based on the set temperature, the incoming water temperature, etc., and the operating speed of the blower is detected and detected. There is one that controls the gas proportional valve according to the operating speed to make the combustion air amount and the fuel gas amount have a predetermined air-fuel ratio.

[0003]

However, as described above, even if the gas proportional valve is controlled based on the operating speed of the blower, if the amount of gas supplied to the burner is suddenly changed, Since the combustion state becomes unstable, change the energizing current value to the gas proportional valve in a unit time (for example, 0.05
There is a limit to the magnitude of the current value that changes every second). As a result, even if the command current value to the gas proportional valve is set in accordance with the blower's operating speed that is quickly changed in response to the required heat amount, the current value of the gas proportional valve is actually There is a delay before the value is changed.
In particular, when the set heat is changed or the incoming water temperature decreases and the required heat amount increases significantly, and the number of revolutions of the blower controlled in accordance with the required heat amount increases, the opening of the gas proportional valve The delay time of change becomes large. For this reason, with respect to the amount of combustion air supplied by the blower, a time delay occurs until the gas amount corresponding to the amount of combustion air is supplied to the burner, and the air-fuel ratio becomes inadequate. During this period, there is a problem that the air becomes momentarily rich (excess air), and abnormal noise is generated due to combustion.

It is an object of the present invention to prevent the combustion state from becoming unstable when changing the required heat quantity and to prevent the generation of abnormal noise.

[0005]

The present invention comprises a required heat amount determining means for determining the required heat amount of a burner, and provides a blower and a fuel supply amount for supplying combustion air to the burner according to the required heat amount. In a combustion control device for controlling a proportional valve for controlling, a target rotation speed determining means for determining a target rotation speed of the blower according to the required heat amount, and a rotation speed detecting means for detecting an operating rotation speed of the blower. A rotational speed difference detecting means for detecting a rotational speed difference between the target rotational speed and the operating rotational speed and determining whether the target rotational speed is higher than the operating rotational speed by a predetermined rotational speed or more; While driving the blower with the rotation speed as the control rotation speed, when the rotation speed difference is a predetermined rotation speed or more, the intermediate rotation speed between the target rotation speed and the operating rotation speed is continued for a predetermined time, and Blower control hand A blower drive means for setting the control rotation speed to drive the blower, and a proportional valve control means for controlling the current value of the proportional valve based on the detected rotation speed of the rotation speed detection means. Technical means.

[0006]

In the present invention, the target rotation speed of the blower is determined according to the required heat quantity, and the target rotation speed is set as the control rotation speed.
The blower is driven. Further, the operating speed of the blower is detected, and it is determined whether or not the target speed is higher than the operating speed by a predetermined speed or more.If the target speed is higher than the operating speed by a predetermined speed or higher, the target speed is increased. The blower is driven with the rotation speed intermediate between the rotation speed and the operating rotation speed as the control rotation speed continuously for a predetermined time. On the other hand, the proportional valve is controlled by a current value according to the detected rotation speed of the blower. As a result, when the required heat amount changes and the target rotation speed of the blower increases significantly enough to cause a difference of a predetermined rotation speed or more with respect to the operating rotation speed, the combustion air amount supplied to the burner is , The amount of combustion air corresponding to the required heat amount does not increase at once, but is once increased to the amount of combustion air corresponding to the heat amount less than the required heat amount, and after a predetermined time has passed, until the amount corresponding to the required heat amount, It is increased step by step.

Correspondingly, the current value of the proportional valve is
Since it is controlled stepwise according to the operating speed of the blower that supplies the combustion air, even if the characteristic of changing the current value of the proportional valve is set gently for a stable combustion of the burner, the predetermined time Since it increases to the current value corresponding to the blower rotation speed until the time elapses, it can be changed to the current value corresponding to the blower operating rotation speed, and then again to the blower speed increased to the target rotation speed. Since the current value corresponding to the rotation is increased step by step, the combustion air amount by the blower and the gas amount adjusted by the proportional valve do not greatly deviate from the predetermined proper air-fuel ratio. Therefore, no abnormal noise is generated in the burner due to a defect in the air-fuel ratio.

[0008]

According to the present invention, even if the required heat quantity changes greatly, the change characteristic of the rotation speed of the blower for supplying the combustion air to the burner is changed to the change characteristic of the fuel supply quantity supplied by the proportional valve. It can be loosened to suit. Therefore, the amount of combustion air is less than the amount of fuel supplied, and even if there is a sudden change in the required heat amount, an appropriate air-fuel ratio is secured in the burner and abnormal noise is generated. There is no.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on the embodiments shown in the drawings. FIG. 1 shows only a hot water supply unit 1 in a gas water heater with a reheating function. In FIG. 1, the water supply pipe 10 communicates with the heat exchanger 12 and the bypass pipe 13 via the distributor 11, and the downstream side of the heat exchanger 12 and the bypass pipe 13 join and are connected to the hot water outlet pipe 14. There is.

The distributor 11 is a water quantity controller for adjusting the water quantity of the heat exchanger 12 and the water quantity of the bypass pipe 13 in accordance with the turning angle of the valve body. As for the relationship between the amount of water in the bypass pipe 13 and the total amount of water in the hot water outlet pipe 14, at 0 to 90 degrees, only the amount of water in the heat exchanger 12 increases according to the rotation angle, and the amount of water in the bypass pipe 13 is in a substantially fully closed state. Is fixed to a small amount of water (0.5 liters / minute) set to eliminate dead water, and at 90 to 270 degrees, the water quantity of the heat exchanger 12 becomes constant at the water quantity at 90 degrees, and the water quantity of the bypass pipe 13 becomes Only the angle is set to increase according to the turning angle. Here, the distributor 11 is
When it is driven by a stepping motor and a rotation angle corresponding to each water amount set as described above is given by calculation, it is driven by the number of steps corresponding to the rotation angle. In addition, 15 is a water amount sensor, 16 is a feed water temperature thermistor, 17 is a water governor, 18 is a heat exchanger outlet thermistor,
Reference numeral 19 is a hot water temperature thermistor.

The heating means for heating the heat exchanger 12 includes two burners 22 and 23 in which the amount of the fuel gas supplied by the proportional valve 21 provided in the fuel pipe 20 for supplying the fuel gas is controlled. In addition, a blower 24 for supplying combustion air to the burners 22 and 23 is provided. Further, the burner 2 is connected to the branch fuel pipes 25 and 26 that branch from the fuel pipe 20 and supply the fuel gas to the burners 22 and 23.
Small solenoid valves 27, 28 for controlling the combustion of 2, 23, respectively
Is provided. Reference numeral 29 is an original solenoid valve, 30 is an ignition electrode of the igniter, and 31 is a frame rod for detecting ignition.

The hot water supply unit 1 having the above structure is controlled by the control device 40 together with the reheating unit (not shown).
The control device 40 controls the combustion of the burners 22 and 23 and the water amount control by the distributor 11, and controls the outlet heated water temperature by a combination of these controls. In the combustion control, the point fire extinguishing control of the burners 22 and 23 is performed according to the water flow detection by the water amount sensor 15, and the set temperature Tset by a remote controller (not shown) provided in the bathroom or the kitchen and the water supply temperature detected by the water supply temperature thermistor 16. The feedforward control amount of the heating amount of the burners 22 and 23 is calculated from the temperature Tin and the water amount detected by the water amount sensor 15, and after the tapping temperature Tout reaches the set temperature Tset, the tapping temperature T
A part of the feedback control amount based on out is added to the feedforward control amount, the required heat amount for the burners 22 and 23 is calculated, the opening / closing control of each small solenoid valve 26, 27, the opening control of the proportional valve 21. And the combustion amount control for controlling the rotation speed of the blower 28 is performed.

In the water amount control, the maximum water amount reference value Lff is calculated to prevent the set temperature Tset, the feed water temperature Tin, and the water amount in the water heating circuit from exceeding the maximum heating capacity of the burners 22 and 23 with respect to the set temperature Tset. In order to calculate the reference value and prevent the tap water temperature from fluctuating when the user operates the faucet during hot water supply and the amount of water changes, and to improve the stability of the tap water temperature when the set temperature is changed. Set temperature to Tse
A correction value calculation for calculating the water amount correction value Lp from the deviation between t and the outlet hot water temperature Tout is performed, and the sum of the maximum water amount reference value Lff and the water amount correction value Lp calculated by these is set as the maximum water amount value L for the water amount. The distributor 11 is controlled to a rotation angle corresponding to the rotation angle. In the correction value calculation, in order to obtain the set temperature as quickly as possible in cold start, a limit is set in the calculation of the water amount correction value Lp in the transition period until the outlet heated water temperature reaches the set temperature. When the outlet heated water temperature Tout is Tout <Tset-1, the water amount correction value Lp
= 0, and when Tout ≧ Tset −1 is satisfied, calculation of the water amount correction value Lp is started, and after the fire extinguishing operation due to water stoppage,
The water amount correction value Lp is continuously calculated for the post-purge period until about 8 minutes have elapsed, and after about 8 minutes, the water amount correction value Lp is set to 0 and the water amount control is performed. In the present embodiment, in addition, in order to prevent the gradual increase in the amount of water in the initial stage of hot water supply due to the above water amount control and to obtain the stability of the water amount, the minimum value of the maximum water amount value L is set in accordance with the maximum water amount reference value Lff. I try to limit it.

Next, the combustion control section 41 for controlling the combustion amount in the control device 40 will be described with reference to FIG. The combustion control unit 41 is roughly divided into three parts: a required heat amount calculation unit 42, a blower control unit 43, and a proportional valve control unit 48.
It is composed of two functional parts. As described above, the required heat amount calculation unit 42 calculates the feedforward control amount of the heating amount of the burners 22 and 23 from the set temperature Tset, the feed water temperature Tin, and the water amount, and the outlet heated water temperature Tout has reached the set temperature Tset. After that, a part of the feedback control amount based on the hot water outlet temperature Tout is added to the feedforward control amount to calculate the required heat amount for the burners 22 and 23.

The blower controller 43 includes a required heat amount calculator 42.
Although the number of rotations of the blower 24 is controlled based on the required heat amount calculated in the above, in the present embodiment, in particular, the set temperature T
When there is a large change in the set or a large change in the water supply temperature Tin,
In order to secure the stability of combustion, in order to suppress the change in the rotation speed of the blower 24, the target rotation speed determination unit 44, the blower drive unit 45, the rotation speed detection unit 46, and the rotation speed comparison unit 47 are included. There is.

The target rotation speed determination unit 44 rotates the blower 24 necessary to supply the burners 22 and 23 with the combustion air amount corresponding to the combustion amount corresponding to the required heat amount calculated by the required heat amount calculation unit 42. In the functional unit that determines the number of revolutions, the target number of revolutions is promptly determined corresponding to the required heat quantity. The blower drive unit 45 differs from the target rotation speed of the target rotation speed determination unit 44 set in the rotation speed comparison unit 47, which will be described later, by using the target rotation speed determined by the target rotation speed determination unit 44 as the control rotation speed. It is a functional unit that drives and controls the blower 24 based on the control rotation speed.

The rotation speed detecting section 46 is a functional section for detecting the actual operating speed of the blower 24 driven by the blower driving section 45. The rotation speed comparison unit 47 determines the target rotation speed N determined by the target rotation speed determination unit 44 in correspondence with the required heat quantity.
o and the actual blower 24 detected by the rotation speed detection unit 46
Of the target rotation speed No is determined by comparing the target rotation speed No with the predetermined rotation speed Nx or more with respect to the operation rotation speed Na. When the rotation speed difference N is greater than the predetermined rotation speed Nx and the rotation speed difference ΔN is larger than the predetermined rotation speed Nx, the control rotation speed in the blower drive unit 45 is set to an intermediate value between the target rotation speed No and the operation rotation speed Na, for example, the target rotation speed Na. The number of revolutions Nv (Nv = No-Ny), which is smaller than the number No by a certain number of revolutions Ny, is set, and this is continued for a predetermined time t to drive and control the blower 24.

The proportional valve control unit 48 determines the target current value of the proportional valve 21 corresponding to the operating rotation speed Na of the blower 24 detected by the rotation speed detection unit 46, and controls the energization current value of the proportional valve 21. To do. Here, the magnitude of the change in the energizing current value changed when the target current value changes is, for example, 0.1 mA per unit time (0.05 seconds) in order to ensure the stability of combustion. Is set by giving a gradual constant change speed to the change speed of the operating rotation speed Na, so that the rapid change of the operation rotation speed Na of the blower 24 follows with a delay. It is like this.

Next, the operation of this embodiment will be described with reference to FIG. When the user opens the faucet and the amount of hot water supplied through the water heating circuit reaches the ignition water amount, pre-purge by the blower 24 is performed, and when the rotation of the blower 24 reaches a predetermined rotation speed, the original solenoid valve 29, small The solenoid valves 26 and 27 are opened, the proportional valve 21 is controlled to the ignition opening degree, the burners 22 and 23 are ignited, and the heating control is started. On the other hand, as the water amount control, the maximum water amount reference value Lff is calculated from the feed water temperature Tin detected by the water supply temperature thermistor 16, the set temperature Tset, and the maximum heating capacity of the burners 22 and 23, and the hot water outlet temperature Tout and the set temperature T are calculated.
The water amount correction value Lp is calculated from the relationship with the set, and the distributor 11 is controlled according to the sum.

During hot water supply, the target speed No. and the operating speed N
a is compared, and the rotation speed difference ΔN is a predetermined rotation speed Nx.
It is determined whether or not this is the case, and when the rotation speed difference ΔN is smaller than the predetermined rotation speed Nx (N in step S1).
O), the blower 24 is driven with the target rotation speed No determined according to the required heat amount as the control rotation speed (step S2). While the hot water is being supplied, the set temperature Tset is changed to a high value or the feed water temperature Tin is lowered, so that the required heat amount calculated by the required heat amount calculating section 42 is, for example, as shown in FIG.
When the speed rapidly increases from Qmin to Qmax, the target rotation speed No is swiftly changed from the rotation speed Nmin to the rotation speed Nmax in the rotation speed determination unit 44 of the blower control unit 43.

At this time, the target rotational speed No and the operating rotational speed N
Since the rotation speed difference ΔN from “a” is larger than the predetermined rotation speed Nx (YES in step S1), the control rotation speed of the blower 24 is immediately changed to the changed new target rotation speed No, which is the rotation speed Nmax. Is not changed, and is set to a rotation speed Nv (Nv = No-Ny) which is smaller than the target rotation speed No by a constant rotation speed Ny for a predetermined time t (step S
3), the operating speed Na of the blower 24 is the predetermined time t
During the period, the rotation speed Nmin changes to the rotation speed Nv. Further, in the middle of this, due to the inertia of the impeller of the blower 24, the operating speed Na temporarily exceeds the rotation speed Nv and overshoots, then reaches the rotation speed Nv, and when the predetermined time t elapses, the blower The control rotation speed of the fan 24 is changed to the target rotation speed No.
Is changed from the number of revolutions N to the number of revolutions Nmax, and in this case as well, the operating number of revolutions Na temporarily exceeds the number of revolutions Nmax and overshoots, and then becomes the number of revolutions Nmax.

The operating speed N of the blower which changes in this way
The target current value of the proportional valve 21 is also changed corresponding to a, and the energization current value is changed by a predetermined current value for each unit time toward the target current value. At this time, the change in the energization current value of the proportional valve 21 is delayed with respect to the change in the operating speed Na of the blower 24, but the change amount of the operating speed Na of the blower 24 is divided into two stages. Since the amount of change in each stage is small, the amount of fuel gas controlled by the proportional valve 21 does not significantly deviate from the appropriate air-fuel ratio with respect to the amount of combustion air supplied by the blower 24. Therefore, the burner 22,
In No. 23, since combustion is performed with an appropriate air-fuel ratio, it is possible to prevent abnormal noise from being generated due to unstable combustion.

As described above, according to the present invention, when the required heat quantity changes, the fuel gas changes due to the change delay of the current value of the proportional valve with respect to the change of the combustion air quantity due to the change of the rotation speed of the blower. The delay in change of the supply amount can be reduced as compared with the conventional case. Therefore, an appropriate amount of fuel gas corresponding to the combustion air can be supplied to the burner, and the burner does not largely deviate from the proper air-fuel ratio. As a result, no abnormal noise is generated in the burner. In the above embodiment, when the required heat amount is large, it is determined whether the target rotation speed No is greater than the operation rotation speed Na by a predetermined rotation speed Nx or more, and the control rotation speed is determined according to the determination result. However, when the required heat quantity is small, the hot water outlet temperature is much higher than the set temperature, and it is necessary to lower the hot water outlet temperature quickly. It is necessary to set the difference ΔN, the constant rotation speed Xy for determining the control rotation speed, and the predetermined time t for continuing the rotation speed to different values from the above cases.

[Brief description of drawings]

FIG. 1 is a partial schematic view showing a main part of a gas water heater with a reheating function according to an embodiment of the present invention.

FIG. 2 is a partial functional block diagram for explaining combustion control of the control device in the embodiment of the present invention.

FIG. 3 is a flow chart for explaining an air blowing control operation in the embodiment of the present invention.

FIG. 4 is a time chart for explaining combustion control in the embodiment of the present invention.

[Explanation of symbols]

 21 Proportional Valve 22, 23 Burner 24 Blower 40 Control Device (Combustion Control Device) 42 Required Heat Quantity Determining Section (Required Heat Quantity Determining Means) 44 Target Rotation Speed Determining Section (Target Rotation Speed Determining Means) 45 Blower Driving Section (Blower Driving Means) 46 rotation speed detection unit (rotation speed detection means) 47 rotation speed difference comparison unit (rotation speed difference detection means) 48 proportional valve control unit (proportional valve control means)

Claims (1)

[Claims] 1. A required heat amount determining means for determining a required heat amount of a burner, comprising a blower for supplying combustion air to the burner according to the required heat amount and a proportional valve for controlling a fuel supply amount. In a combustion control device for controlling, a target rotation speed determination unit that determines a target rotation speed of the blower according to the required heat amount, a rotation speed detection unit that detects an operating rotation speed of the blower, the target rotation speed and the Rotational speed difference detection means for detecting a rotational speed difference from the operating rotational speed and determining whether the target rotational speed is higher than the operating rotational speed by a predetermined rotational speed or more, and the target rotational speed as a control rotational speed While driving the blower, when the rotation speed difference is equal to or more than a predetermined rotation speed, an intermediate rotation speed between the target rotation speed and the operating rotation speed is continued for a predetermined time and the control rotation speed of the blower control means is continued. age A combustion control device comprising: a blower drive means for setting and driving the blower; and a proportional valve control means for controlling a current value of the proportional valve based on the detected rotation speed of the rotation speed detection means. .