JPH0113011B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital combustion control device applied to a gas or oil combustor or the like.

Combustion equipment that uses gas, heavy oil, etc. as fuel has a prescribed operating procedure from preparation for ignition to completion of ignition.
It is considered safest and most reliable to proceed with the sequence of operations in conjunction with confirmation of equipment operation.

These combustor operation requirements have been met in conventional devices using simple electrical circuits, such as relay sequences. However, in recent years, work-oriented thinking has been adopted from the standpoint of improving the functionality of combustion equipment, or ensuring efficient and safe operability during ignition and operation.

In other words, the method involves checking the results of each movement step by step, and if an abnormality is discovered during the step, the movement should be stopped immediately and the next correct instruction should be followed. , or guide the sequential operation to the safe side and perform a failsafe operation.

Relay circuits are insufficient in terms of configuration and speed to accurately judge and advance the operating status of increasingly complex devices, and semiconductors are characterized by their small size, low cost, and ease of control. Digital control is being considered in many places.

Particularly in the field of combustion equipment, various operation sequences are required for gas and oil combustors depending on whether they are used for general household use, commercial use, industrial use, etc.

However, since the basic sequence at ignition startup and the basic operation sequence such as flame check during operation are common, it is possible to make it smaller, cheaper, and more reliable by integrating these common control circuits. is required.

The present invention has been made to deal with the above-mentioned situation, and is caused by an operational failure of a semiconductor element in a digitally controlled combustion device, especially a drive transistor of a first valve control circuit that first opens a valve when a thermostat is required. Shortage failure can be quickly detected not only during ignition operation, but also during operation to ensure safe operation of the combustion equipment (in the case of gas, the first valve control circuit operates to open the pilot valve, The purpose of the present invention is to provide a fail-safe type digital combustion control device that is designed to prevent gas from leaking into the furnace as soon as the power is turned on, which poses the risk of explosion.

Hereinafter, the present invention will be described with reference to illustrated embodiments. In FIG. 1, SF is a sequence selector, which performs a switching operation between recycling and non-recycling.

TH is a thermo-required signal generating section for promoting ignition, which performs a switching operation and is connected to the output section of the signal via an amplifier A1 to a differentiating circuit 1 having an AND circuit AN11 as a trigger gate. The thermostat HS is connected to a two-input NAND circuit NA3 via an amplifier A2.

FD is a flame detection unit, which uses an output side device to detect whether or not the flame is reliably ignited by optical or other means. The detection side of the frame detection section FD is an amplifier A3 and an AND circuit.
AN12, NAND circuit NA1 via differential circuit 2
is connected to the input of Signal generation unit KR that generates the OR signal of the earthquake detection device and dry firing detector
is connected to an AND circuit AN12 and a delay circuit 3 via an amplifier A4, and the output side of this delay circuit 3 is connected to the other input side of the NAND circuit NA3.

The pre-purge shift register PSR is a pre-purge clock generator OSC that divides a specific frequency.
It shifts the signal in synchronization with the clock from 2, and controls the timing function when performing the valve opening operation, which will be described later. A matching circuit MP consisting of a flip-flop or the like is connected to the final output terminal, and the output terminal of the matching circuit MP is introduced to the input gate of the trial shift register TSR. That is, this trial shift register TSR operates following the prepurge shift register PSR, and the matching circuit MP
The trial shift register is connected to the reset terminal of
The output terminal of the TSR is connected to the output terminal of the inverter circuit IN3.

The trial clock generator OSC1 is inputted as a clock to the trial shift register TSR, which is also frequency-divided. Also the AND circuit
AN2 performs a predetermined signal delay operation by setting the simultaneous output condition of the trial shift register TSR, and after the output signal satisfies some logic conditions, the output device is activated.

First, the output device BM is an output circuit for a fan motor driven by a transistor Q1, and connects, for example, a relay K1 as a load to exhaust raw gas or combustion gas.

SSH is a safety switch heater circuit. First, as a safety check during ignition operation, transistor Q5 is turned on and the heater operates for a unit time to check the safety inside the furnace.

Subsequently, during normal operation, the first valve control circuit V
1C is applied, the valve is opened by the load K2 of the transistor Q2, and after a while, the output signal of the timer TA or TB is input to the transistors Q3 and Q4, respectively, to drive the ignition control circuit IGC and the second valve. Control circuit V2
Perform operation C.

For example, the load K3 of the ignition control circuit is connected to the ignition coil via a normally closed contact circuit, and ignition is performed when the contact opens.

In addition, K4 is a valve, and the first valve control circuit plays the role of a pilot valve in the case of gas fuel.
In addition, in the case of heavy oil, etc., the main valve is opened and closed.

Similarly, the load K4 of the second valve control circuit V2C also opens and closes the main gas supply valve in the case of gas, and similarly opens and closes the main valve in the case of heavy oil. In the figure, AN is an AND circuit, OR is an OR circuit, M is a memory circuit composed of a flip-flop circuit, and NA is a NAND circuit.

In the present invention constructed in this way, the operation will be explained below with reference to the control circuit block diagram of FIG. 1 and the time chart of FIG. 2. In FIG. 2, A shows the normal combustion state of oil, and B shows the normal combustion state of gas. In FIGS. 2A and B, pre-ignition pre-purge period 1, post-ignition period 2, ignition trial period 3, V2 delay period 4, power supply 5, and after ignition, the next sequence (post-ignition) is started quickly. The transitional trial shortening function 6, the ignition establishment 7, and the trial period shortening 8 after the ignition establishment of only gas combustion are shown.

Assume now that the sequence selector SE selects the sequence operation, and the output signal during recycling is held at H level. In such a state, when the thermo request signal generator TH is activated, its output signal is inverted from L level to H level, and the signal passed through amplifier A1 and differentiator circuit 1 remains at H level and is output to the AND circuit. Input to AN14.

Since the other three input gates of the NAND circuit NA1 under the off condition are all initially set to H level, the NAND circuit is activated by the H level trigger input signal from the AND circuit AN14.
The output of NA1 is inverted to L and input to AND circuit AN3. Therefore, the AND circuit AN3 unconditionally keeps its output at the L level regardless of the levels of the other input gates, so the output of the NAND circuit NA2 connected to the next stage is kept at the H level.

Therefore, the base current is supplied to the transistor Q5 of the safety switch heater SSH to turn on the heater. On the other hand, the output line output in parallel with the heater transmits an L level signal to the inverter circuits IN1 and IN2 via the resistor R and the buffer 5.

The inverted signal H passed through the inverter circuit IN1 is
It is input to the AND circuit 4 via the latch circuit 6. However, since the other input gates of the AND circuit AN4 are at L level, the output signal is L,
The operations of the memory circuits M1 and M2 do not change either, and the output signal of the memory circuit M2 remains at the L level and is transmitted to the input of the prepurge shift register PSR.

Also, since the output of the AND circuit AN5 is L, the transistor Q1 of the output circuit BM for the fan motor
remains in the off state. The L signal transmitted to the input of the pre-purge shift register PSR is divided and output as the pre-purge clock OSC.
From the time when the output of the NAND circuit NA1 switches to the H level in synchronization with the signal No. 2, the L input of the pre-purge shift register PSR is connected to the AND circuit AN6.
The output signal is sequentially shifted to the output side by the clock after passing through. When this operation is started, at that moment one of the inputs of the AND circuit AN1 is inverted to L level, so the output of this AND circuit AN1 naturally becomes L level.

Then, the input of the pre-purge shift register PSR switches to H again, the H level is sequentially shifted, and when all the outputs become H, the AND circuit AN
The output of 1 also changes from L to H.

On the other hand, when the output of the AND circuit AN1 becomes L level, the output of the NAND circuit NA1 becomes H, and the output of the AND circuit AN3 becomes H.
Since the output of NA2 is switched to L, transistor Q
5 is turned off and the heater is cut off, but the other output lines connected to its collector momentarily switch to H, so the inverter circuit IN1 and the latch circuit 6
The output via the AND circuit AN4 momentarily meets the H level condition, and the memories M1 and M2 become H level, and the output of the AND circuit AN5 becomes H, turning on the transistor Q1 of the fan motor output circuit BM.
Switch to Then, the output K1 is applied and the fan motor starts rotating, or safe pre-combustion within the furnace is confirmed, and the combustion gas is discharged to the outside by the fan. Also, due to the initial operation, the H signal via the inverter circuit IN2 is transferred to the memory M.
3. Reset M4 and timers TA and TB in advance. During this time, shift register PSR for pre-purge is
The initial L input of takes a predetermined time to reach the final output, and once the L signal is sent out, each of its output signals is subsequently filled in entirely by the H signal, and the H signal is shifted until the final output is reached. The H level is transmitted from the terminal to the input set terminal of the matching circuit MP. At this time, the output Q terminal of the matching circuit MP is inverted to the H level for the first time, and an H signal is input to the trial shift register TSR. With this operation, the signal synchronized with the clock of the trial clock generator OSC1 starts a shift operation, but when the shift signal reaches the first output terminal of the register, the matching circuit MP is connected because the inverter circuit IN3 is connected. It is immediately reset and the output of the matching circuit is returned to the L level again.

Shift register that started the above shift operation
When all the output signals of each stage of TSR become H, the output signal of AND gate AN2 also becomes H. For this reason,
Inverter circuit IN3 output signal and AND gate
AND gate by ANDing the output signals of AN2
The output signal of AN7 also becomes H, and this AND gate
When the output signal of AN7 sets the memory M3, the input H condition of the AND circuit AN8 is established, and the transistor Q2 of the first pilot valve control circuit V1C is set.
turns on and the pilot valve is opened if gas is present. This series of operations is as illustrated in FIG. 2B, for example. After a predetermined time, the input condition of the AND circuit AN10 is set to H, so the memory M4 is set and the timer
TA and TB start operating. Immediately when the timer TA times up, the transistor Q3 of the ignition control circuit IGC is turned on, and the ignition operation is performed by the load K3. And continue with timer TB
Due to time-up, the second valve control circuit V2C
Transistor Q4 turns on, valve K4 operates, and all ignition occurs, completing the operation.

In addition, if there is a failure in ignition, the flame detector FD monitors the ignition situation, so if a misfire is confirmed, the differential circuit 2 immediately sends an
The level output pulse signal is generated by a NAND circuit
Switch the first and second input gates of NA1 to L,
Therefore, its output changes to H again and the NAND circuit NA
Once the output of 2 is switched to L, the transistor Q5 is
Return it to the off state and switch its output to H level,
The signal H for returning to the beginning is given again to the pre-purge shift register PSR, and the re-ignition operation is performed. At this time, the first gate of the AND circuit AN8, that is, the line from the thermo request signal generating section TH, is instantaneously inverted to L by the previous flame detection signal H signal, so the transistor Q2 of the first valve control circuit V1C is turned off. be done. Of course memory M3, M
4. Timers TA and TB are H of inverter circuit IN2
It is reset in the meantime by a signal. In this way, in the event of a misfire, such ignition recycling operation is repeated a predetermined number of times, and if ignition is successful, normal operation is resumed, and if ignition is not successful, an alarm signal is output and the failure is communicated by alarm or other means. .

On the other hand, the first valve control circuit V controls the pilot flame in the case of gas fuel and the valve in the case of heavy oil fuel when the thermo-required signal of the combustion device is generated.
If a collector-emitter short failure occurs in the 1C transistor Q2, the collector potential of the transistor Q2 will always remain stable at the L level, so the input gate of the OR circuit OR2 will become an L signal, and other When all the circuits in are operating normally, the memory circuit M3 is H, so the AND circuit after the thermo request signal is generated.
Naturally, the input signal to AN8 becomes L, and its output signal also becomes L. In other words, normally the 2 of OR circuit OR2
One of the two input gates should be held at H level, but in this case both gates stabilize at L level, so the output of AND circuit AN3 immediately switches to L level. At the same time, the output of the NAND circuit NA2 is also reversed to H, and the safety switch heater SSH remains turned on. In other words, since the alarm circuit AL is connected in parallel with the safety switch heater SSH, it immediately notifies the outside of the device failure. As another example, if a short failure occurs in the transistor Q2 for some reason while normal operation is being continued, the alarm operation is executed without delay using the same operating procedure. Also, when fuel exhaustion is detected, the output of the NAND circuit NA1 is inverted to L, and the AND circuit
Since the output of AN8 is dropped to L and the output of AND circuit AN5 is made to be L, the fan motor output circuit BM,
The first valve control circuit V1C, the ignition control circuit IGC, and the second valve control circuit V2C are naturally switched off to perform fail-safe operation.

As described above, according to the present invention, the first valve control circuit V1C during ignition operation or during operation combustion
It is possible to quickly discover a short failure in the transistor Q2 that operates the pilot valve (in the case of gas). Furthermore, the present invention allows anyone to drive safely, and even in the event of a misfire, the safety confirmation operation can always be carried out in conjunction with the flame detector, which is compatible with ensuring reliability of operation. In addition, there is an advantage that a highly functional digital combustion control device can be configured with a relatively simple circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a digital combustion control device showing the circuit configuration of essential parts of the present invention, and FIG. 2 is a time chart of FIG. 1. SE...Sequence selector, TH...Thermo request signal generation section, FD...Flame detection section, PSR...Prepurge shift register, MP...Matching circuit, TSR...
Trial shift register, BM...output circuit for fan motor, SSH...safety switch heater, V
1C...first valve control circuit, IGC...ignition control circuit, V2C...second valve control circuit.

Claims (1)

[Claims] 1. AND circuit AN1 which obtains the logical product of the outputs of each stage of the pre-purge shift register PSR which determines the pre-purge period; AND circuit AN2 which obtains the logical product of the outputs of each stage of the trial shift register TSR which determines the trial period; The output signal of shift register PSR and the AND circuit AN
AND circuit to obtain logical product with normal signal from 2
AN7, a memory circuit M3 set by the output signal of the AND circuit AN7, a heat request signal based on the output signal of the thermo request signal generator TH that promotes initial ignition of the combustion device, and an output signal of the memory circuit M3. an AND circuit AN8 that obtains the logical product of the AND circuit AN8, a transistor Q2 of the first pilot valve control circuit V1C driven by the output signal of the AND circuit AN8, an output signal of the AND circuit AN8, and a collector output signal of the transistor Q2. an OR circuit OR2 that obtains the logical sum of the heat request signal and the flame presence signal based on the output signal of the flame detector FD monitoring the ignition status, and the AND circuit AN1.
and the output signal of the AND circuit AN2, and the output signal of the OR circuit OR2 and the NAND circuit NA1.
AND circuit AN3 that obtains logical product with the output signal of
and a safety switch heater SSH and an alarm generation circuit AL that operate by inputting the output signal of the AND circuit AN3.