JPS587892B2 - Combustion amount control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a combustion amount control device for a water heater or the like having a proportional solenoid valve that continuously controls the combustion amount.

Configuration of conventional examples and their problems In conventional combustion devices, such as water heaters, one of the means for controlling the combustion amount of the burner in response to load fluctuations is to fully open a valve device provided in the fuel passage in response to the water temperature. There is one that completely closes the valve, and another that electrically or physically proportionally controls the opening degree of the valve device in response to the water temperature.

However, the former fully open, fully closed type, so-called ON-O
In the FF type valve device, the water temperature fluctuates periodically within a certain range, and frequent ON-OFF operations reduce the life characteristics of the valve, and there are also problems in terms of ignition and extinguishing noise.

In this regard, in the latter case, which uses a proportional valve device, the amount of combustion supplied to the burner is proportionally controlled according to the load at the time, so there are problems with the above-mentioned variations in hot water temperature, valve life, and noise. However, on the other hand, a new control problem was raised regarding the combustibility of the burner due to the proportional control of the combustion amount.

In other words, in burners that use not only gas but also liquid fuel such as oil, there is a stable combustion range related to the combustion characteristics, and if the lower limit of the above range is exceeded, the fire may be inadvertently extinguished or a large amount of CO will be generated. It is what it is.

Therefore, conventional combustion amount control means using proportional valve devices have adopted combustion amount control characteristics as shown in FIG.

That is, in FIG. 1, the region indicated by X is a proportional combustion amount control region in which the combustion amount of the burner is proportionally controlled according to the temperature of the heated object.

The above-mentioned proportional combustion amount control region X is not set in the entire range between the maximum and zero combustion amount, but is designed to instantly shut off combustion when the minimum stable combustion amount QL of the burner is reached.

According to such combustion amount control characteristics, proportional combustion amount control of the burner is performed within a stable combustion range, so problems such as extinguishing and increase in CO amount are eliminated.

Further, FIG. 2 shows the rise characteristic when the temperature of the heated body is set to Ts in the proportional combustion amount control region X of FIG. 1.

For example, when a temperature sensor is provided in a water outlet path of a water heater, it takes time for the temperature sensor to detect the temperature of hot water discharged from the heating section.

Furthermore, it takes time for the valve to operate based on the detection signal (current, pressure) from the temperature detector.

Due to such a delay in response time, the temperature of the heated object is not stable from the beginning, and gradually reaches Ts while undulating up and down with reference to the set temperature Ts.

The wave phenomenon described above becomes more significant as the load on the object to be heated is smaller.

However, in Fig. 1, if the combustion amount of the burner is set to Q1 in order to set the temperature of the heated body to Ts, the temperature of the heated body initially exceeds the combustion OFF point T1 and reaches T2 due to the previous temperature wave. As a result, the combustion of the burner is stopped, and when the temperature of the heated object decreases due to the combustion stop of the burner, the burner restarts combustion again and the temperature of the heated object decreases from T1 due to the fluctuation in the combustion amount. 3 For this reason, especially when the load is small, even if the combustion amount is set in the proportional combustion amount control region As with conventional ON-OFF control, this method has the disadvantage of causing fluctuations in water temperature, generation of ignition/extinguishing noise, and shortening of valve life, as well as narrowing the actual range of proportional combustion amount control. Was.

OBJECT OF THE INVENTION The present invention eliminates such conventional drawbacks, and uses a conventional proportional solenoid valve to control the heated object by improving the control circuit without adding a new ON-OFF type solenoid valve. The purpose of this is to easily return to a stable control state even if the temperature of the controller fluctuates.

Structure of the Invention In order to achieve this object, the present invention amplifies an electrical signal from one detection unit that detects a physical quantity such as the temperature of a heated object, and changes the electrical output proportionally in accordance with the signal. A control circuit is provided that has a proportional output region, a constant output region in which the output does not change in response to changes in the signal, and an output cutoff point in this constant output region, and the proportional solenoid valve is controlled by the output of this control circuit. It is something that you have.

With the above configuration, even if the burner is controlled in the proportional combustion amount control region close to the minimum stable combustion amount QL and the temperature of the heated object fluctuates and the combustion amount is throttled, the control circuit will control the proportional solenoid valve to In addition to maintaining a safe combustion state by preventing the minimum stable combustion amount from being reduced to below the minimum stable combustion amount QL, if the above temperature fluctuation is within a certain size, the minimum stable combustion amount is maintained at a constant output without immediately shutting off combustion. The system maintains a state in which it is easy to return to a stable state when temperature fluctuations cease, and also achieves reliable temperature control by shutting off combustion when temperature changes are large.

Description of examples Hereinafter, an embodiment thereof will be described with reference to the accompanying drawings.

First, FIG. 3 shows the combustion amount control characteristics of the present invention, which shows the relationship between the temperature of the heated body and the burner combustion amount in a combustion device such as a water heater.

That is, in the present invention, there is a proportional combustion amount control region X, and even if the temperature of the heated object detected by one temperature sensor increases and exceeds the lower limit of the X region, the minimum combustion amount of the burner does not change. The main feature is that a constant combustion amount region Y is set, and when the temperature of the heated object rises to Ta, combustion of the burner is shut off.

According to the combustion amount control characteristics described above, the constant combustion region Y serves as a buffer region against the wave phenomenon of the temperature of the heated object at the time of temperature rise as shown in FIG. 2 described above.

For example, in response to the wave phenomenon of the temperature of the heated object, the temperature of the heated object overshoots the set value Ts and exceeds the temperature T3 at the lower limit QL of the proportional combustion amount control region X, T4.
Even if the burner reaches the minimum combustion amount QL, the burner continues its combustion operation, so the temperature of the heated object does not drop suddenly due to the minimum combustion amount of the burner, and the momentum of the temperature drop causes it to fall significantly below the set value Ts. Finally, the set value Ts
It is stable at the set combustion amount Q2.

Therefore, according to the characteristics shown in Fig. 3, the wave phenomenon when the temperature of the heated object rises is small, and even if the set temperature is determined near the lower limit of the proportional combustion amount control region X, the burner ON- Can prevent OFF combustion,
This allows the actual proportional combustion amount control range to be expanded to the theoretical value.

Note that in the proportional combustion amount control region exist.

Next, FIG. 4 shows a water heater, in which water flowing through a water supply pipe 1 passes through a heat exchanger 3 heated by a burner 2, becomes hot water, and exits from a hot water pipe 4 to a hot water tap 5. be.

A safety valve 7 and a proportional electromagnetic valve 8 are connected to the fuel supply path 6 to the burner 2, and a fuel supply path 10 to the pipe burner 9 branches from between the two valves.

Further, FIG. 5 shows a specific configuration example of the proportional solenoid valve 8, in which 11 is an excitation coil wound around the bobbin 12, and 13.13 is a spacer 14 at both ends of the bobbin 12.
．． 14', each supporting piece 1
5. 15' is formed by bending and cutting.

A plunger 16 has a projection 17 made of a small diameter non-magnetic material projecting upward and is inserted into the excitation coil 11 so as to be movable forward and backward with a small gap therebetween.

18 is a case that houses the excitation coil 11 and the like.

Moreover, 1 9 and 19 are the support pieces 1 5 . 1 and 5' are leaf springs having one end fixed to each other, and these free ends are pivotally connected to pins 20 and 20' projecting from the circumferential surfaces of the plunger 16 and the protrusion 17.

That is, as is clear from the above, the plunger 16 has a pair of plate springs 1 9 . The leaf springs 19 and 19', which are supported by 19' and are installed to prevent friction from occurring, act as plungers that are generated when a current is applied to the excitation coil 11. 16
It also serves as a dust counter for axial operation.

21 is a partition plate that closes the lower opening of the case 18; 22 is a diaphragm provided for sealing in the penetration portion of the tip of the plunger 16 with respect to the partition plate 21; 23 is a combustion inlet 24 connected to the fuel supply path 6; A valve device main body having a fuel outlet 25 and a valve seat 27 formed in the middle of a fuel passage 26 connecting these inflow and outflow ports 24 and 25, and a valve seat 27 at the tip of the plunger 16 facing the valve seat 27 This is where the attached valve body 28 is located.

29 is a packing provided between the partition plate 21 and the main body 23.

Unlike a valve driven by a motor or the like, such a proportional solenoid valve has a quick response because the position of the valve body 28 is determined immediately according to the current value applied to the excitation coil 11, and therefore it can be turned ON. -The period during which the combustion amount remains below the minimum combustion amount of the burner during the transition of OFF combustion can be extremely shortened, and therefore, by combining it with the present invention, the effect of stable combustion, which is one of the objects of the present invention, can be significantly reduced. It is something to tighten.

Furthermore, in FIG. 4, 30 is a heat-sensitive resistance element such as a thermistor that detects the temperature of hot water flowing in the hot water outlet pipe 4, and 31 is operated by a signal from this element 30 to control the current of the excitation coil 11 in the proportional solenoid valve 8. It is an electrical controller.

With the above configuration, when starting the hot water supply operation, the hot water tap 5
When it is opened, the water flowing through the tap water pipe 4 has not yet been heated, so the resistance of the heat-sensitive resistance element 30 is the highest, and therefore the excitation coil 11 of the proportional solenoid valve 8 is controlled via the controller 31.
maximum current flows.

From this, the plunger 16 is attached to the leaf spring 19. 1 9
', and this plate is 1 9 . 1 and 9', and the valve body 28 is moved away from the valve seat 27. At this point, since the maximum amount of fuel is supplied to the burner 2, its combustion amount is is also maximum.

Next, when the amount of hot water discharged is reduced from the above, that is, when the hot water supply load becomes smaller, the temperature of the hot water passing through the hot water supply pipe 4 increases, so the resistance of the heat sensitive resistance element 30 decreases, and the resistance of the heat sensitive resistance element 30 decreases by that amount. As a result, the current in the excitation coil 11 in the proportional solenoid valve 8 decreases, and the leaf springs 1 9 ,
The plunger 16 descends with an anti-dust force of 19'.

As a result, the valve body 28 approaches the valve seat 27 and throttles the fuel amount.
It regulates the combustion amount of the burner 2.

As is clear from the above, in the water heater shown in Fig. 4, the proportional solenoid valve 8 proportionally controls the amount of fuel to the burner 2 in response to fluctuations in the hot water supply load. The temperature is kept approximately constant.

Further, in the present invention, as described above, the proportional solenoid valve 8 is closed so that the combustion amount of the burner 2, that is, the degree of restriction of the fuel amount does not fall below a certain level, to prevent incomplete combustion.
At the time of ignition, the control temperature is suppressed by igniting with a combustion amount corresponding to the hot water supply load above the certain amount, and furthermore, at the time of ignition, the amount of fuel is increased, albeit within a limited short time, to reduce the flame transfer properties of the burner. This is further improved, but this point will become clear in the explanation of the controller 31 below.

The controller 31 controls the current of the excitation coil 11 as shown in FIG. 3 in response to temperature fluctuations detected by the heat-sensitive resistance element 30.

That is, in the X region, the current of the exciting coil 11 is controlled proportionally to temperature fluctuations, and in the Y region, a constant current is maintained against temperature fluctuations between T3=Tc to ensure the minimum combustion amount of the burner. When the temperature exceeds +qc, the current is cut off.

Further, in this state, the burner is re-ignited when the temperature drops below T.

According to the above control method, burner combustion is always cut off at a current below the Y region, so incomplete combustion does not occur, and the current of the exciting coil 11 is not detected to turn on and off. Since the temperature from one temperature-sensitive resistance element 30 is detected and turned on and off, reliable temperature control can be performed even in the on-off state.

Further, even when proportional control and ON-OFF control are combined, stable temperature control with little variation can be achieved.

Next, the specific circuit configuration of the controller 31 will be explained with reference to FIG.

In the figure, S is a DC power supply circuit for driving the proportional solenoid valve, which is composed of an AC power supply 32, a step-down transformer 33, full-wave rectification diode bridges 34 and 35, and a smoothing capacitor 36.

Reference numeral U designates a circuit that flows a constant current in the Y region, which forms a bridge with resistors 37, 38, 39, 40 and 41, detects the voltage of the bridge with differential transistors 42 and 43, and transmits the signal to transistors 44 and 44. Amplify with 45,
It supplies current to the excitation coil 11 of the proportional solenoid valve.

46 is the emitter resistance of the differential transistor 42, 43, 4
7 is an emitter resistance of the transistor 44, and 48 is an emitter resistance of the transistor 45.

49 is a negative feedback resistor, which is intended to stabilize the circuit gain.

The diode 50 is for absorbing the back electromotive force of the exciting coil 11.

The transistor 51 provided in the current increasing circuit V is in the proportional region
The resistor 52,
A bridge is formed by the heat-sensitive resistance element 30 and resistors 37, 38, and 39, and the potentials ad are compared.

Now, if the detected temperature of the heat-sensitive resistance element 30 becomes lower than Ts in FIG. 3, the resistance value of the heat-sensitive resistance element 30 is large, so the potential at point m becomes higher than the potential at point b, and the transistor 51 is energized. .

However, since it is an emitter follower circuit, the potential at point b has almost the same value as the potential at point a, and the potential at point b changes in accordance with the change in the potential at point a.

The change in potential remains unchanged in the differential transistors 42 and 43.
This signal is used to increase or decrease the current in the excitation coil 11.

When the detected temperature of the heat-sensitive resistance element 30 is lower than the set temperature, the base and emitter of the transistor 51 are reverse biased, and a constant current is applied to the exciting coil 11.

Transistor 53 of ON-OFF circuit W. 54 is the third
The operation is performed in the Y region of the figure, and a bridge is formed by a resistor 52, a heat-sensitive resistance element 30, and resistors 37, 38, and 39, and potentials c and d are compared.

Now, if the detected temperature of the heat-sensitive resistance element 30 is higher than the temperature shown in FIG. 3, it is because the resistance of the heat-sensitive resistance element 30 is small.
When the potential at point C becomes lower than the potential at point d, transistor 53 is energized and transistor 54 is driven to bypass the collector current of transistor 42 through diode 55 and cut off the current in exciting coil 11.

When the temperature decreases and the resistance value of the heat-sensitive resistance element 30 increases, and the potential at point C becomes higher than the potential at point d at temperature T5 in FIG. 3, the base and emitter of the transistor 53 are reverse biased, and the 54 is turned off, the constant current is supplied to the excitation coil 11 again.

56 provides a difference between the temperature at which the transistor 53 turns on (Ts in FIG. 3) and the temperature at which it turns off (To in FIG. 3), in order to prevent the valve from being turned on and off frequently, and for switching. This is a positive feedback resistor to ensure operation.

The diodes 57 and 58 are for temperature compensation of the transistors 51 and 53, and are intended to prevent the ON-OFF point and the point where the proportional current flows from shifting due to changes in ambient temperature.

The resistor 39 has a constant current range temperature width (T3-T in Figure 3).
c).

The set temperature can be freely selected by changing the value of the resistor 52.

The capacitor 59 accumulates charge when the proportional solenoid valve is OFF, that is, when the transistor 54 is ON, and when the proportional solenoid valve is ON,
In other words, when the transistor 54 is OFF, it releases the charge, temporarily increases the potential at point a, and the excitation coil 1
1, a current is passed through the valve so that the opening is such that the burner can be ignited stably.

This operation increases the flame transferability of the burner and prevents the occurrence of fuel spill accidents due to ignition failure, and since it is performed for a limited time, after the expiration of the time period, the resistance value of the temperature-sensitive resistance element 30 will be adjusted. The combustion amount can be quickly returned to the original combustion amount, and therefore the influence on the control temperature can be minimized.

In addition, in FIG. 6, 60 is a resistor.

FIG. 7 shows the temperature characteristics of the water heater obtained by the above-mentioned electric control means. ON-OFF control is performed between the two.

In region G where the amount of hot water supplied is equal to or greater than L1, proportional control is performed and the temperature is maintained approximately at the set temperature.

If the maximum allowable hot water supply amount L2 or more, even the maximum combustion amount cannot be controlled, so the temperature drops rapidly.

Effects of the Invention As described above, the combustion amount control device of the present invention provides the following effects.

(1) As a control circuit, the proportional output region amplifies the electrical signal from the detection section 1 and changes the electrical output proportionally according to that signal, and the constant output that does not change the output in response to changes in the signal. Since the proportional solenoid valve is controlled by the output of the proportional solenoid valve, the proportional combustion amount control region is close to the minimum stable combustion amount of the burner, which causes fluctuations in the temperature of the heated object and reduces the combustion amount. Even when the temperature fluctuation is within a certain range, the control circuit prevents the proportional solenoid valve from being throttled below the minimum stable combustion amount of the burner, maintains a stable control state, and maintains the minimum stable output with a constant output if the temperature fluctuation is within a certain amount. This is to maintain the amount of combustion and ensure a state where it is easy to return to a stable state when temperature fluctuations cease.

Therefore, it is possible to obtain safe combustion and a stable combustion amount control state by using the conventional proportional solenoid valve as is, expanding the actual proportional combustion amount control range to the theoretical range, and maximizing the combustion characteristics of the burner. It has an effect that can be utilized.

(2) Since the output cutoff point of the control circuit is in a constant output range, when the temperature change of the heated object is large, combustion can be cut off at the minimum stable combustion amount, and reliable temperature control can be performed. The control circuit creates a proportional output area, a constant output area, and an output cutoff point in response to a signal from one detection part, and drives the proportional solenoid valve. The cutoff control region is not reversed and is determined in an orderly manner according to the detection unit signal, making it possible to always obtain stable combustion amount control characteristics even during mass production of the device.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram of conventional combustion amount control, Fig. 2 is a temperature rise characteristic diagram of a heated object, Fig. 3 is a characteristic diagram of combustion quantity control of the present invention, and Fig. 4 is a diagram using a water heater as a combustion device. , FIG. 5 is a sectional view of the proportional solenoid valve, FIG. 6 is a diagram showing an example of the electric control circuit of the proportional solenoid valve, and FIG. 7 is a diagram showing one example of the electric control circuit for the proportional solenoid valve. It is a water temperature characteristic diagram of the vessel. 2...Burner, 3...Heat exchanger, 8.
...Proportional solenoid valve, 30...Detection unit (hot water temperature resistance element), 31...Controller, S...
Direct current power supply circuit for driving proportional solenoid valve, U...Circuit that flows constant current, ■...Current increase circuit, W...
...ON-OFF circuit.

Claims (1)

[Claims] 1. A burner, an object to be heated by the burner, and a detection section that detects a physical quantity such as the temperature of the object to be heated, and an electrical signal that amplifies the electrical signal from this detection section and generates electricity proportionally according to the signal. A control circuit that has a proportional output region in which the output changes and a constant output region in which the output does not change in response to changes in the signal, and has an output cutoff point in this constant output region, and the output of the control circuit. A combustion amount control device consisting of a proportional solenoid valve installed in the controlled fuel supply path to the burner.