JPS6139565B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion control device for a proportional control type gas water heater equipped with a fan motor and a pressure equalization valve.

Currently, gas combustion control devices are widely used in general households, but half of them are constant combustion types (the amount of combustion is constant).
Therefore, the amount of hot water dispensed is adjusted to adjust the ratio of hot water to water to obtain the desired hot water temperature. As a result, waste of water and gas is inevitable. In addition, it is necessary to adjust the temperature of the hot water, and there is the inconvenience that the temperature of the hot water may change if the hot water is tapped at multiple locations. To improve this, some models have a step control function (the combustion amount can be set in several stages), but the fact that the combustion amount is constant remains the same, so the conventional inconvenience remains.

On the other hand, proportional control type gas water heaters have been put on the market as a solution to the inconvenience of conventional constant combustion types due to the energy saving trend, and are attracting attention in various fields.

Although there are several proportional control systems, FIG. 1 shows the basic configuration of a type of gas water heater using a fan motor and a pressure equalizing valve, which is related to the present invention. This figure 1 shows the case of a stop-start three-point hot water supply system. In this figure, SV is the main valve, GG is the gas burner, and FV is the valve opening that changes analogously according to the air pressure sent from the fan motor FM. ,
It is a pressure equalizing valve that operates so that the gas pressure supplied to burner B is proportional to the previous air pressure, flow switch SW2 that detects the flow of water through heat exchanger HC, thermistor TH that detects the hot water temperature, and flame of burner B. Detecting frame rod FL, fan motor
The control circuit CC operates in response to a signal from the air pressure switch SW3 that detects the air pressure from the FM, and operates the load circuit LC to control the fan motor.
Controls FM, ignition transformer IG, and original valve SV.

The water temperature is controlled by controlling the rotation speed of the fan motor FM, adjusting the pressure equalizing valve EV, and changing the gas amount. This control system is composed of a feedback loop schematically shown in FIG. i.e. set temperature and thermistor
Comparing the water temperature detected by the TH, the PID control circuit generates a signal for PID operation based on the deviation and sends it to the next phase control circuit. The phase control circuit converts the signal into a trigger signal and supplies it to the fan motor drive circuit, and the phase control circuit controls the rotational speed of the fan motor to change the gas amount in a predetermined direction. After the system reaches equilibrium in this way, combustion continues with a constant amount of gas. When there is a change in the set temperature or the amount of hot water dispensed, the hot water temperature is corrected according to the feedback loop described above.

By the way, in general, in combustion equipment, before attempting an ignition operation, a pre-purge operation is performed to exhaust residual gas, etc. from the combustion chamber. In particular, this type of gas water heater is a closed type, so it is necessary to perform a sufficient pre-purge, but considering that it will be used in a general household, it is desirable to do it in a short time from the viewpoint of ease of use. However, the fan motor uses an induction motor, and the starting voltage of the induction motor (the voltage at which it starts rotating for the first time from a stopped state) increases rapidly as the temperature decreases due to lubricant, friction, etc., and then the motor rotates at a constant speed. This is a problem, especially in the winter, as it takes a long time to reach the number.

In addition, if ignited at the maximum combustion capacity, an explosive flame will be generated, which is dangerous, and the ignition noise is unpleasant, so a slow ignition method is used, in which a small flame is ignited at first and the flame gradually increases. It is desirable to take.

However, if this slow ignition method is used, the rotation speed of the fan motor must be kept low at first, so the applied voltage must be lowered, but this may cause inconveniences such as not reaching the starting voltage in winter. become.

In view of the above, the present invention applies maximum voltage to the fan motor during pre-purge to ensure startup, performs sufficient pre-purge in a short time, and then lowers the applied voltage to cause slow ignition. An object of the present invention is to provide a combustion control device that solves the problem of starting a fan motor while using an ignition method.

An embodiment of the present invention will be described below. In FIG. 3, a load circuit is configured on the primary side of the power transformer T, and a control circuit is configured on the secondary side. In the load circuit, terminals 01 and 02 are power supply terminals of the combustion control device and are connected to an AC power source. The phase of the fan motor FM is controlled by the fan motor drive circuit, and when the relay X _W is turned on, its normally open contact closes and the maximum voltage is preferentially applied, causing full rotation. Original valve SV, ignition transformer IG is relay X _P ,
The normally open contact of X _F closes and turns ON. The control circuit is composed of a rectifier circuit, a smoothing circuit, and various circuits connected thereafter. The remainder of the secondary winding of the power transformer T is applied to a flame rod FL connected to a terminal 13 via a flame detection circuit, and the flame detection circuit detects the presence or absence of a flame by utilizing the flame rectification effect. Note that the terminal 14 is grounded through the water heater body. The block 40 is a bridge circuit, and the bridge is composed of a resistor 22, a resistor 23, a thermistor TH as a temperature detector connected to terminals 09 and 10, and a variable resistor VR as a temperature setter connected to terminals 11 and 12. The PID control circuit then outputs an output based on the deviation.

Next, the sequence will be explained in detail with reference to the time chart shown in FIG. Terminal 03,0
4 is connected to the operation switch SW1,
When this is OFF, power is not supplied to the subsequent circuits, all relays are OFF, and therefore all loads are OFF, and the sequence does not proceed. Next, when the operating switch SW1 is turned on, current is supplied to the LED 31 through the resistor 20, causing it to light up, indicating that the operating switch has been turned on.
Now, when tapping starts at any of the three tap holes in Figure 1, flow switch SW2 detects the water flow and turns ON, base current flows to transistor 30 through resistor 21, and relay X _W operates. Therefore, the maximum voltage is applied to the fan motor FM, the rotation speed rises, air is blown into the combustion chamber, and a pre-purge operation is performed to exhaust the residual gas in the chamber. When air is blown, the air pressure to the combustion chamber increases, and when the pressure exceeds a certain level, air pressure switch SW3 turns on.
Power is supplied to the various circuits that follow. When air pressure switch SW3 turns on, relay X _F
operates, the fan motor start timer circuit starts the timer operation, and after the fan motor FM reaches the maximum number of revolutions, the time is up and the output turns off the transistor 30. Therefore, the relay X _W returns and opens its normally open contact, and the fan motor FM is thereafter phase-controlled by the FM drive circuit. At this time, the flame detection circuit has not yet detected a flame, so in the phase control circuit, the output of the flame detection circuit preferentially determines the trigger phase and controls the rotation speed of the fan motor FM to approximately half of the maximum rotation speed (slowly). The engine attempts to reach a predetermined rotational speed corresponding to ignition. The slow ignition preparation timer circuit starts timer operation when the fan motor start timer circuit times out, but because there is a fall time due to the inertia of the fan motor FM, the slow ignition preparation timer circuit starts rotating at about half the previous maximum rotation speed. The trick is to wait until the numbers go down. When the rotational speed of the fan motor FM falls and stabilizes at about half of the maximum rotational speed, the slow ignition preparation timer circuit times up, relay _XP operates, and the trial timer circuit starts timer operation. When relay X _P operates and closes the normally open contact, the main valve SV turns on and supplies gas, and since relay X _P is already on and the normally open contact is closed, the ignition transformer IG turns on. Start a spark with the ignition electrode and attempt ignition. At this time, since the rotational speed of the fan motor FM is approximately half of the maximum rotational speed as described above, the amount of air and gas is small, and so-called slow ignition is performed (see FIG. 4A for the above operation). If the flame detection circuit does not detect a flame within a certain period of time (trial time), the trial time circuit times out and resets the _relay
Turn on AL. When the _relay
Turn off. On the other hand, when the alarm circuit operates, its output also stops generating the trigger signal of the phase control circuit, so the power supply to the fan motor FM is stopped.
After a short period of time, the rotation speed decreases, so the air pressure to the combustion chamber also decreases, and the air pressure switch SW3 is activated.
turns OFF, cutting off power to various circuits. Therefore, all loads are OFF and only the alarm AL is ON.
This state continues (see FIG. 4B for the above operation).

If ignition occurs during the previous ignition attempt and the flame detection circuit detects a flame, the _relay Stop the timer operation of the circuit and turn _on the relay
Continue operating state. In addition, until the flame detection circuit detected a flame, the phase control circuit outputs a trigger signal with a determined phase preferentially using the output of the flame detection circuit, but after detecting a flame, the output of the PID control circuit Since a trigger signal with a phase based on this is output, the rotation speed of the fan motor FM is controlled according to the feedback loop mentioned earlier, and the combustion amount follows this to obtain hot water at the set temperature (the above operation (see Figure 4A). Thereafter, when the set temperature or the amount of hot water dispensed is changed, the feedback loop described above always controls the hot water temperature to the set temperature.

If combustion stops for some reason during combustion, the flame detection circuit detects the ignition and turns off relay _XP , which continues to operate with the output of the flame detection circuit.Then, its normally open contact is opened and the original valve SV is turned off. Turn OFF and shut off the gas path. At the same time, relay X _F operates, but when relay X _P turns OFF, the alarm circuit operates and alarm AL turns ON, notifying the user. When the alarm circuit operates, its output stops the generation of the trigger signal of the phase control circuit, so the fan motor
Since the FM is no longer energized and the rotational speed decreases, the air pressure to the combustion chamber decreases, and the air pressure switch SW3 is turned off, cutting off the power to the various circuits thereafter. Eventually, all loads are turned off.
However, only the alarm AL continues to be ON (see Figure 4c for the above operation).

If hot water is stopped during combustion, the flow switch
Since SW2 is turned off, the power to the subsequent various circuits is cut off, all loads are turned off, and combustion stops. The alarm AL is activated due to ignition error or fire interruption.
If it is turned on, it can be restarted by stopping the hot water supply, turning off the flow switch SW2, turning on the water again, and turning on the flow switch SW2, or turning off the operation switch SW1 and turning it on again. Note that in FIGS. 4A to 4C, hatched areas are drawn in the charts for "hot water" and "FM", which indicate the range of the amount of hot water dispensed and the range of the rotation speed of the fan motor FM.

In the above explanation, voltage was applied to fan motor FM at startup through the contacts of relay X _W , regardless of the fan motor drive circuit, but as shown in Fig. 5, relay X _W was applied to When not in use, the output of the fan motor start timer circuit is input to the phase control circuit, and until the fan motor start timer circuit times out, the phase control circuit outputs a trigger signal with an advanced phase preferentially to start the fan motor FM. It's okay. In this case, it is more effective to advance the trigger phase as much as possible. Further, the rotation speed of the fan motor FM during the slow ignition operation is not limited to half of the maximum rotation speed, but is increased or decreased depending on the combustion equipment. In addition, the air pressure switch
Instead of SW3, an air flow switch that operates by detecting air flow may be used.

As described in the embodiments above, according to the present invention, the fan motor is activated when the fan motor rotates and reaches a predetermined rotation speed, that is, after the blowing pressure of the fan motor reaches a predetermined value. Since a starting timer circuit is provided, the fan motor applies maximum voltage for a certain period of time from when the blowing pressure of the fan motor reaches a predetermined value until the timer circuit times out. In other words, the maximum voltage is applied to the fan motor for a certain period of time after the rotational speed of the fan motor has risen to a certain degree. Therefore, no matter how the rotation of the fan motor starts, it will surely reach the maximum rotation, and therefore the pre-purge operation will be performed reliably (in contrast, it is possible to simply reach the maximum rotation after a certain period of time from the start of operation). If the start-up is slow, the pre-purge operation is uncertain because the fan motor may not reach its maximum rotation within the fan motor time by simply applying the maximum voltage to the fan motor. Also, when the pre-purge operation is completed and the voltage applied to the fan motor is under the control of the control circuit, the slow ignition timer circuit starts to measure time, and when this timer circuit times out, the ignition operation starts. Considering the fall time of the rotation of the fan motor, the ignition operation is started after waiting until the rotation speed has settled down to a predetermined rotation speed. Therefore, the ignition operation during the trial can be performed reliably.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the basic configuration of a type of gas water heater using a fan motor and a pressure equalization valve, Fig. 2 is a block diagram of the control system, and Fig. 3 is a circuit configuration of an embodiment of the present invention. Block diagrams shown in Figure 4A and Figure B
5 and 4C are time charts for explaining the operation, and FIG. 5 is a block diagram showing the circuit configuration of another embodiment. B...burner, HC...heat exchanger, FM...fan motor, EV...pressure equalization valve, SV...main valve, GG...gas governor, IG...ignition transformer, FL...flame rod, TH...thermistor, LC...load circuit, CC...control Circuit, W1...operation switch, SW2...flow switch, SW3...air pressure switch.

Claims (1)

[Claims] 1. A gas burner, a heat exchanger heated by the gas burner to turn water into hot water, a fan motor that sends air to the gas burner, and a water flow detection means that detects water flow to the heat exchanger. , a pressure equalizing valve that controls the gas pressure sent to the gas burner in proportion to the air pressure supplied by the fan motor; and a pressure equalizing valve that detects the air blowing pressure of the fan motor and outputs an output when the air blowing pressure reaches a predetermined pressure. An air pressure switch to derive the water, a temperature detector to detect the temperature of the hot water,
A combustion control device for a proportional control type gas water heater, comprising a control circuit that controls the rotation speed of the fan motor in proportion to the deviation between the detected temperature and the set temperature, in accordance with the output of the air pressure switch. A fan motor start timer circuit that starts operation and times up after the fan motor reaches maximum rotation, and a fan motor start timer circuit that applies maximum voltage to the fan motor when it is operating and times up after the fan motor reaches maximum rotation, and then controls the control circuit. a switching circuit that switches to apply voltage to the fan motor via the
a slow ignition timer circuit that measures the time until the fan motor reaches a predetermined rotation speed after being controlled by the control circuit; and a trial circuit that operates according to a time-up output of the slow ignition timer circuit to perform an ignition operation. A combustion control device comprising: a circuit.