JPS63271022A - Air/fuel ratio control device for gas burning equipment - Google Patents

Abstract

PURPOSE:To prevent deterioration of durability and instability of burning due to a gas supply greater than or less than the burning capacity of equipment by regulating an opening range setting means for solenoid valve and a speed range setting means for electric fan in advance according to the gas species. CONSTITUTION:CPU 31 has connected to it a hot water temperature setting device 40 for setting the hot water delivery temperature, an opening degree input device 41 for an opening range setting means 1 and a rotational speed input device 42 for a rotational speed range setting means 2. Variable resistors in the opening degree input device 41 limits the maximum and minimum current applied to a solenoid valve 11 by their being adjusted to limit the maximum and minimum opening of the solenoid valve 11 so that the gas supply amount to gas burning equipment may not be greater than its maximum burning capacity or smaller than the minimum burning capacity. Variable resistors in the rotational speed input device 42 sets the maximum and minimum current applied to an electric motor 12 by their being adjusted corresponding to the maximum and minimum opening of the solenoid valve 11 to set the maximum and minimum rotational speed of the fan 12 so that the air/fuel ratio at that time may be appropriate for the gas species.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a gas combustion system in which the ratio between the amount of gas supplied to a gas burner and the amount of primary air supplied (hereinafter simply referred to as the air-fuel ratio) is kept almost constant. The present invention relates to an air-fuel ratio control device for equipment.

[Prior art]

In fully premixed gas combustion equipment, where the air-fuel ratio is appropriately increased to make the gas combustion equipment more compact, or where all of the air required for combustion is mixed with the gas as primary air, flame lift is required. In order to obtain stable combustion without backfire or backfire, it is necessary to keep the air-fuel ratio at a nearly constant and appropriate value. An example of a technology that satisfies this need is a gas combustion control device disclosed in Japanese Patent Application Laid-Open No. 60-80018. In this technology, a gas amount adjustment means is controlled by a combustion amount adjustment signal. The air 1tiJfi1 node means is controlled by a signal obtained by correcting the air amount signal calculated based on the combustion amount adjustment signal.

[Problem that the invention seeks to solve]

Gas combustion equipment is supplied with different gas types depending on the area where it is installed, and the unit calorific value varies depending on the gas type.

Gas pressure, combustion characteristics, etc. are different. Therefore, even in the same gas combustion equipment, the characteristics between the current applied to the solenoid valve that controls the gas supply amount and the voltage applied to the electric fan that controls the primary air supply amount are A, B in Fig. 6, As shown in C, it is necessary to use different air-fuel ratios depending on the gas type, otherwise it will not be possible to provide an appropriate air-fuel ratio according to the gas type and achieve stable combustion, or the maximum combustion capacity of the equipment will not be achieved. Problems arise in that if the fuel is exceeded, durability is reduced, or if the capacity is below the minimum equipment capacity, combustion becomes unstable.

For this reason, the characteristic map or calculation formula that determines the characteristics between the current applied to the solenoid valve and the voltage applied to the electric fan needs to be different for each gas type, but this makes it possible to However, since the specifications differ depending on the region of use, there are problems in that the total number of items in stock increases, costs increase, and the effort involved in inventory management and shipping management increases.

The present invention is based on the fact that the characteristics between the opening degree of the solenoid valve and the rotation speed of the electric fan to obtain an appropriate air-fuel ratio quantitatively vary greatly depending on the gas type, but are qualitatively similar. The above problem was solved by focusing on the following.

[Means for solving problems]

For this purpose, the air-fuel ratio control device for gas combustion equipment according to the present invention, as shown in FIG. It includes an electromagnetic valve 11 that changes to control the amount of gas supplied to the gas burner 10, and an electric fan 12 whose rotation speed continuously changes depending on the applied voltage to control the amount of primary air supplied to the gas burner 10. The air-fuel ratio control device for gas combustion equipment includes a hot water temperature setting device 40 that sets the hot water temperature, a hot water temperature sensor 43 that detects the hot water temperature from the heat exchanger 20, and a maximum and minimum temperature of the solenoid valve 11. an opening range setting means 1 for setting the opening degree to a predetermined value; a rotation speed range setting means 2 for setting the maximum and minimum rotational speeds of the electric fan 12 to predetermined values; and the maximum and minimum opening degrees. The ratio of the current applied to the electromagnetic valve 11 based on the maximum and minimum applied currents corresponding to the ratio and the voltage applied to the electric fan 12 based on the maximum and minimum applied voltages corresponding to the maximum and minimum rotation speeds. a storage means 3 for storing preset characteristics between the ratios and the hot water temperature setting device 4;
The electromagnetic valve 11 is opened so that the difference between the two outlet temperatures is reduced within the range of the maximum and minimum applied current by comparing the outlet temperature set by 0 and the outlet temperature detected by the hot water temperature sensor 43. a first calculating means 4 that calculates an applied current that changes the degree; a solenoid valve driving device 45 that applies the applied current calculated by the first calculating means to the solenoid valve 11; a second calculation means 5 for calculating a ratio of the applied currents based on the maximum and minimum currents; A third device that calculates the ratio of current applied to the fan 12.
The electric fan 1 is calculated based on the tenth calculation stage 6, the ratio calculated by the third calculation means, and the maximum and minimum applied voltages.
a fourth calculation means 7 for calculating the voltage applied to the fourth calculation means 7;
The applied voltage calculated by the calculation means is applied to the electric fan 1.
The present invention is characterized in that it is equipped with a motor drive device 46 that applies an electric current to the motor.

[Effect]

Depending on the type of gas to be used, the opening range setting means 1 is adjusted in advance so that the gas amount does not exceed the maximum combustion capacity of the device and does not fall below the minimum combustion capacity of the solenoid valve 11.
The maximum and minimum opening degrees of the electric fan 12 are set, and the rotation speed range setting means 2 is adjusted so that the air-fuel ratio at the maximum and minimum opening degrees becomes an appropriate value according to the gas type. and minimum rotation speed. When the gas combustion equipment is activated, the first calculating means 1 compares the hot water temperature detected by the hot water temperature sensor 43 with the hot water temperature preset by the hot water temperature setting device 40, and calculates the current applied to the solenoid valve 11. The solenoid valve drive device 45 applies this value of applied current to the solenoid valve 11.
If there is a difference in the temperature of the Okayama hot water, the opening degree of the solenoid valve 11 is changed to change the amount of gas supplied to the gas burner 10, and the temperature of the hot water discharged from the heat exchanger 20 is set by the hot water temperature setting device 40. value. The applied current is calculated to be within the range of the maximum and minimum applied currents corresponding to the maximum and minimum opening degrees of the solenoid valve 11.

The second calculation means 5 calculates a ratio of the applied current calculated by the first calculation means 4 based on the maximum and minimum applied currents, and the third calculation means 6 stores it in the storage means 3 based on this ratio. The voltage ratio to be applied to the electric fan 12 is calculated from the obtained characteristics.

The fourth calculation means 7 calculates the voltage applied to the electric fan 12 based on the ratio calculated by the third calculation means 6 and the maximum and minimum applied voltages corresponding to the maximum and minimum rotational speeds of the electric fan 12, and applies the voltage to the electric fan 12. The drive device 46 applies this value of applied voltage to the electric fan 12 . As a result, the rotational speed of the electric fan 12 becomes a value corresponding to the opening degree of the solenoid valve 11.
Primary air is supplied to the gas burner 10 in an amount corresponding to the amount of gas supplied.

The characteristics between the opening degree of the solenoid valve 11 and the rotational speed of the electric fan 12 to obtain an appropriate air-fuel ratio quantitatively vary greatly depending on the gas type, but qualitatively they are similar, so it is important to memorize them. The characteristics between the ratio of the current applied to the electromagnetic valve and the ratio of the voltage applied to the electric fan, which are stored in the means 3, are substantially the same even if the gas types are different.

〔Effect of the invention〕

As described above, according to the present invention, by adjusting the opening range setting means and the rotation speed range setting means in advance according to the gas type to be used, gas combustion equipment with the same specifications can be adapted to various different gas types. It is possible to obtain an appropriate gas supply amount and air-fuel ratio by using the equipment, and to prevent a decrease in durability and instability of combustion due to gas supply exceeding or below the combustion capacity of the equipment or an inappropriate air-fuel ratio. Can be done. In addition, the adjustment based on the gas type is performed at the maximum and minimum opening of the solenoid valve and the corresponding maximum and minimum rotational speed of the electric fan. Since the characteristics between fan rotational speeds are qualitatively the same even if the gas types are different, the air-fuel ratio is maintained at a predetermined value depending on the gas type even at values other than the maximum and minimum values.

〔Example〕

First, the embodiment shown in FIGS. 2 to 4 will be explained.

As shown in FIG. 2, a water supply pipe 21 is connected to one end of the heat exchanger 20.
A hot water supply pipe 22 having a hot water tap 23 at its tip is connected to the other end. When the hot water supply tap 23 is open, water supplied from the water supply pipe 21 is heated by the gas burner 10 when passing through the heat exchanger 20, reaches a predetermined hot water temperature, and is discharged from the hot water tap 23. gas burner 10
The mixing chamber 15 is connected to a gas supply pipe 13 equipped with a solenoid valve 11 whose opening degree changes according to the applied current, and an air supply pipe from an electric fan 12 whose rotation speed changes according to the applied voltage. 14 are connected. The opening degree of the solenoid valve 11 and the rotational speed of the electric fan 12 are controlled in conjunction with each other by an electronic control device 30, which will be described later.
is supplied from the gas burner 10 and mixed in the mixing chamber 15.
supplied to

The electronic control unit 30 is a microprocessor (hereinafter simply C
(referred to as PU) 31, and read-only memory (hereinafter simply referred to as RO).
M) 32 and writable memory (hereinafter simply RA
The CPU 31 includes a solenoid valve drive device 45 and a motor drive device 46, respectively.
A solenoid valve 11 and an electric fan 12 are connected via. In this embodiment, the solenoid valve 11 is a proportional solenoid valve whose opening degree changes in proportion to the applied current, and the electric fan 12
The motor is a brushless DC motor whose rotational speed changes in proportion to the applied voltage.

A hot water temperature sensor 43 such as a thermistor is provided in the hot water outlet pipe 22 located immediately after the heat exchanger 20 to detect the hot water temperature.
The electric fan 12 is also provided with a rotation speed sensor 44 that generates a number of pulses proportional to its rotation speed, and both sensors 43, 4.4 are connected to the CP via an interface in the enclosure.
It is connected to U31. The CPU 31 also includes a hot water temperature setting device 40 for setting the hot water temperature, and an opening range setting means 1.
opening input device 41 and rotation speed range setting means 2 for
A rotational speed input device 42 for is connected via the enclosure interface. In this embodiment, the hot water temperature setting device 40 is a hot water temperature setting device 40 that can be adjusted by an external knob.
The main body is a variable resistor, and each input device 4L 4
2 is mainly composed of two semi-fixed variable resistors each having a maximum value and a minimum value set according to the type of gas. Each variable resistor of the opening input device 41 limits the maximum and minimum applied current to the solenoid valve 11 by adjusting it, so that the amount of gas supplied to the gas combustion equipment does not exceed the maximum combustion capacity. Furthermore, the maximum and minimum opening degrees of the solenoid valve 11 are limited so that the combustion capacity does not fall below the minimum combustion capacity. Further, each variable resistor of the rotational speed input device 42 is adjusted to set the maximum and minimum voltages applied to the electric motor 12 corresponding to the maximum and minimum opening degrees of the solenoid valve 11, and adjust the air-fuel ratio at that time. The maximum and minimum rotational speeds of the electric fan 12 are set so that the rotational speed of the electric fan 12 is a predetermined appropriate value depending on the type of gas. The variable resistors of both input devices 41 and 42 are adjusted to match the type of gas in the shipping area at the time of shipment from the factory or store, etc., and are then sealed to prevent adjustment.

The ROM 32 stores maximum applied currents (rmax, Blmax, CIm in FIG. 6) of the applied currents to the solenoid valve 11.
ax, etc.) as 100% and the minimum applied current (A1m1n, B1m1n, C1m1n, etc. in Fig. 6) as 0%, and the maximum applied voltage (Fig. 6) of the applied voltage to the electric fan 12. 8Vmax +BVmax,CV
max, etc.) is 100%, and the minimum applied voltage (8Vmin, BVmin in FIG. 6) is 100%.

The characteristics between the ratios RvO and 0% (CVmin, etc.) are stored as a characteristic map. FIG. 3 is a graphical representation of such a characteristic map. In this embodiment, the proportional solenoid valve and the brushless DC motor as described above are used as the motors for the solenoid valve 11 and the electric fan 12. In order to keep the air-fuel ratio constant, the applied voltage ratio Rv should theoretically have a characteristic P that increases in proportion to the square root of the applied current ratio Ri.

This is because the amount of gas supplied to the gas burner 10 is proportional to the square root of the secondary side pressure of the solenoid valve 11, and this secondary side pressure is
This is because the second air amount is proportional to the rotational speed of the electric fan 12. In this example, since the ratios Ri and Rv are both digitized values of 255 bits, the characteristic map is P.
It is not continuous as shown in , but is step-like along P as shown in p. The ROM 32 also stores a control program for executing the control operations shown in the flowchart of FIG.

Next, the control operation of the present invention will be explained mainly with reference to the flowchart shown in FIG.

When the power is turned on to operate the gas combustion equipment, the electronic control unit 30 first sets each variable to 0 or a predetermined initial value, and then water is supplied to the water supply pipe 21 according to the control flow of the enclosure. Determine whether or not there is. If the hot water tap 23 is opened and water is flowing through the water supply pipe 21, the electronic control device 3
0 activates the concave road timing flow to generate an interrupt signal every 0.3 seconds, each time starting execution of the control operation according to the flowchart of FIG.

First, the CPU 31 reads the hot water outlet temperature TI set by the hot water temperature setting device 40 in step 101 as a digitized signal, and similarly reads the hot water outlet temperature T2 detected by the hot water temperature sensor 43 in step 102. Next, in step 103, the rotational speed sensor 44
The rotational speed N2 of the electric fan 12 detected by is read in the same way, and in the subsequent step 104, the applied voltage V of the electric fan 12 stored in the ROM 32 is determined from the applied voltage V output to the electric fan 12 in step 117 of the previous control operation. After calculating the set rotation speed N1 of the electric fan 12 based on the voltage and rotation speed characteristics, step 10
In step 5, the rotation speed error ratio β of the electric fan 12 is calculated using the following formula (% formula %). Then, in step 106, the CPU 3
The absolute value of this rotational speed error ratio β is compared with a predetermined error ratio limit value K (-0, 1 to 0.2), and if it is not 1βbK, proceed to the next step 107, and if 1β1>K, step 119 After the electromagnetic valve 11 is fully closed and the electric fan 12 is stopped to stop combustion in the gas burner 10, all control flows including the timing flow are stopped. This rotational speed error ratio β is used in step 117 described below to correct the voltage applied to the electric fan 12 and bring the rotational speed of the electric fan 12 closer to the set rotational speed according to the opening degree of the solenoid valve 11. However, 1βl>K means that some abnormality has occurred in the electric fan 12 or related parts, and steps 106 and 119 are steps for performing an emergency stop in such a case. It is something.

In step 107, the CPU 31 calculates the increase rate ΔI of the current I applied to the solenoid valve 11 using the following formula 6 (%) α: a proportional constant determined by the operating conditions, and in the subsequent step 108, the following formula 6 (%) Imax, lm1n : The applied current I is calculated based on the maximum and minimum applied currents corresponding to the maximum and minimum opening degrees of the solenoid valve 11 set by the opening input device 41. Following steps 109-1
12, after limiting the applied current I so that its value is within the range of the maximum value 1ma and the minimum value lm1n,
In step 113, the CPU 31 controls the applied current I.
An output is applied to the solenoid valve 11 via the solenoid valve drive device 45.

Next, in step 114, the CPU 31 calculates the ratio R4 of the applied current I using the following formula (%), and then in step 115, calculates the electric fan corresponding to this ratio Ri from the characteristic map shown in FIG. 12
The ratio Rv of the applied current to is calculated.

In step 116, the CPU 31 calculates the voltage applied to the electric fan 12 according to the maximum and minimum applied voltages corresponding to the maximum and minimum rotation speeds of the electric fan 12 set by the rotation speed input device 42. After calculating V and correcting this applied voltage V in step 117 using the following formula 6, % (1), in step 118 this applied voltage V is output to be applied to the electric fan 12 via the motor drive device 46. , stops the control operation according to the flowchart of FIG. 4. In step 117, the electric fan 12
Even if the characteristics between the applied voltage and the rotational speed vary from product to product or change over time, the rotational speed of the electric fan 12 can be corrected to a predetermined value according to the opening degree of the solenoid valve 11. This is to prevent errors in the air-fuel ratio.

The control operation according to the flowchart in FIG. 4 is as described above.
This is repeated every 0.3 seconds, and as a result, the electronic control unit 30 increases the opening degree of the solenoid valve 11 within a range below the maximum opening degree when T2<TI.
In this case, the opening degree of the solenoid valve 11 is decreased within the range of the minimum opening degree or more, and the hot water temperature T2 from the heat exchanger 20 is brought closer to the hot water temperature TI set by the hot water temperature setting device 40, thereby reducing the temperature of both hot water and dust. Match TI and T2. Adjustment of the air-fuel ratio according to the gas type at the time of shipment is performed only at the maximum and minimum opening degrees of the solenoid valve 11 and the corresponding maximum and minimum rotation speeds of the electric fan 12, but an appropriate air-fuel ratio can be obtained. The characteristics between the opening degree of the solenoid valve 11 and the rotational speed of the electric fan 12 for Using one characteristic map, the air-fuel ratio can be maintained at a predetermined value depending on the gas type even at values other than the maximum and minimum values.

In the above embodiment, as described above, the applied current ratio Ri
The characteristic map between Rv and the ratio Rv of the applied voltage is theoretically a square root curve P as shown in FIG.
Since both 4 and Rv are digitized values of 255 bits, they actually have a step-like shape as shown in p. In the case of such a characteristic map, the ratio of applied current R
In the range where i is small (the opening degree of the solenoid valve 11 is small) and therefore the slope of the curve P is large, the ratio of the applied voltage R
Since ν changes in units of more than 1 bit,
The error from the theoretical value of the ratio Rv of the applied voltage to be output is 2 pics I. or more, which increases the error from the theoretical value of the amount of primary air supplied. In this state, the absolute value of the primary air amount is also small, so the relative error further increases, and the error in the air-fuel ratio increases, so combustion tends to become unstable or incomplete. As shown graphically in FIG. 5, the horizontal axis of the characteristic map stored in the ROM 32 is the digitized value of the square of the applied current ratio Ri, and the vertical axis is the digitized value of the applied voltage ratio Rv. This can be solved by using a converted value. In this way, the ratio R
The characteristic map between the square of i and the ratio RvO is theoretically as shown by the straight line Q in FIG. 5, and if this map is digitized, it becomes a stepwise map q along the straight line Q. According to the characteristic map shown in FIG. 5, the ratio of the applied current Rv changes by 1 bit in most cases over the entire range of the square of the applied current ratio Ri, so the ratio of the applied voltage that is outputted Rv The error with respect to the theoretical value is almost never greater than 1 bit. As a result, the error in the amount of primary air supplied is reduced, the error in the air-fuel ratio is also reduced, and combustion becomes stable. In this case, in the flowchart of FIG. 4, step 115 is different from the above explanation, and the applied current ratio Ri calculated in step 114 is
After squaring, the ratio Rv of the applied voltage is calculated from the characteristic map shown in FIG. 5 based on the square of this ratio Ri.

In the above embodiment and its modifications, the ROM 32 stores a characteristic map between the applied current ratio Ri and the applied voltage ratio RvO, which is made up of a large number of sets of numerical values calculated in advance or obtained through experiments. Instead of such a characteristic map, an arithmetic expression may be stored, and the applied voltage ratio Rv may be calculated using this arithmetic expression each time the applied current ratio Ri or its square is calculated.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an air-fuel ratio control device for gas combustion equipment according to the present invention, FIGS. 2 to 4 show an embodiment of the present invention, FIG. 2 is an overall configuration diagram, and FIG. FIG. 4 is a flowchart showing a control program; FIG. 5 is a third modified example FIG. 6 is a diagram showing the characteristics between the current applied to the electromagnetic valve and the voltage applied to the electric fan for each type of gas. Explanation of symbols 1... Opening range setting means, 2... Rotation speed range setting means, 3... Storage means, 4... First calculation means, 5...
・Second calculation means, 6...Third calculation means, 7...Fourth
Calculating means, 10... Burner, 11... Solenoid valve, 12
... electric fan, 20 ... heat exchanger, 40 ... hot water temperature setting device, 43 ... hot water temperature sensor, 45 ... solenoid valve drive device, 46 ... motor drive device. Figure 2! 1 Figure 3 O'y') tro546
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Claims (2)

[Claims] (1) A gas burner that heats the water supply passing through the heat exchanger;
A solenoid valve whose opening degree continuously changes according to applied current to control the amount of gas supplied to the gas burner; and a solenoid valve whose rotation speed continuously changes according to applied voltage to control the amount of primary air supplied to the gas burner. The air-fuel ratio control device for gas combustion equipment includes an electric fan that controls a hot water temperature, a hot water temperature setting device that sets a hot water temperature, a hot water temperature sensor that detects a hot water temperature from the heat exchanger, and a hot water temperature sensor that detects the hot water temperature of the solenoid valve. opening range setting means for presetting maximum and minimum opening degrees to predetermined values; rotation speed range setting means for presetting maximum and minimum rotational speeds of the electric fan to predetermined values; and said maximum and minimum opening degrees. The ratio of the current applied to the electromagnetic valve based on the maximum and minimum applied current corresponding to the ratio of the applied voltage to the electric fan based on the maximum and minimum applied voltage corresponding to the maximum and minimum rotation speed, storage means for storing preset characteristics between the two; and a storage means for storing preset characteristics between the hot water temperature setting device and the hot water temperature detected by the hot water temperature sensor, and comparing the hot water temperature set by the hot water temperature setting device with the hot water temperature detected by the hot water temperature sensor to determine whether the hot water temperature is within the range of the maximum and minimum applied current. a first calculating means for calculating an applied current to change the opening degree of the solenoid valve so that the difference between the two outlet hot water temperatures is reduced; and applying the applied current calculated by the first calculating means to the solenoid valve. a solenoid valve driving device; a second calculation means for calculating a ratio of the applied current calculated by the first calculation means with reference to the maximum and minimum currents; a third calculation means for calculating the ratio of the current applied to the electric fan from the characteristics stored in the storage means; and a third calculation means for calculating the ratio of the current applied to the electric fan based on the ratio calculated by the third calculation means and the maximum and minimum applied voltages. An air-fuel ratio control device for gas combustion equipment, comprising: a fourth calculation means for calculating an applied voltage; and a motor drive device for applying the applied voltage calculated by the fourth calculation means to the electric fan. (2) The characteristic stored by the storage means is a characteristic map consisting of a digitized value of the square of the applied current ratio and a digitized value of the corresponding applied voltage ratio. An air-fuel ratio control device for gas combustion equipment according to claim 1.