JPS6357697B2 - - 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. In response to the operational demands of these combustion equipment, conventional equipment:
This problem was dealt with using simple electrical circuits, such as relay sequences. However, in recent years, a work-oriented approach has been adopted from the standpoint of improving the functionality of combustion equipment, and improving efficiency and safety during ignition and operation. In other words, if an abnormality is discovered during each step of the operation by checking the results one by one, the operation must be stopped immediately and the next correct instruction must be followed, or the sequence of operations must be continued. Relay circuits are inadequate in terms of configuration and speed, and the characteristics of semiconductors are insufficient to accurately judge and advance the operating status of devices that are becoming increasingly complex, such as guiding to the safe side and performing fail-safe operations. Digital control, which is characterized by its small size, low cost, and ease of control, is being considered in many places. Particularly in the field of combustion equipment, various operating sequences are required for gas and oil combustors depending on whether they are for general household use, commercial use, or industrial use. Since the basic operation sequences such as the flame check are all common, it is essential to integrate these common control circuits to make them smaller, cheaper, and more reliable.

Therefore, the present invention has been made to deal with the above-mentioned situation, and when the pre-purge operation time of the combustion device ends and the ignition trial operation begins, an internal failure occurs in the trial shift register. Immediately when any one of the output terminals is inverted to L, the output level of the second AND circuit is inverted to L in order to fail-safe the final load side output device,
At the same time, the output terminal of the 7th AND circuit is lowered to L level, and the subsequent input signal of the 3rd memory is switched to L level, and an L signal is simultaneously applied to the input of the 1st NAND circuit, and its output level is set to H, and the safety switch heater is turned on. immediately shifts the third memory by switching the output H signal of the second inverter on the line of its collector terminal, and shifts the first and second memory of the load.
It is an object of the present invention to provide a digital combustion control device that provides a signal to quickly turn off a valve control circuit and an ignition control circuit.

Hereinafter, the present invention will be described with reference to illustrated embodiments. In FIG. 1, the SE performs a switching operation between recycling and non-recycling using a sequence selector. The TH performs a switching operation in a thermo-required signal generating section that promotes ignition, and a differential-integral circuit 1 having an AND circuit as a trigger gate is connected to the output section of the signal. In addition, the FD uses an output side device in the flame detection section to detect whether or not the flame is definitely ignited by optical or other means, and the detection signal is sent to the differential circuit 2. , a pre-purge shift register that constitutes the main part of the present invention
It is connected to the input of a NAND circuit NA1, which forms a simultaneous condition with the output signal of an AND circuit AN1, which makes the output gates of the same polarity of the PSR a simultaneous condition. Prepurge shift register PSR is a prepurge clock generator that divides a specific frequency.
It shifts the signal in synchronization with the clock from OSC2, and controls the timing function when opening the valve, 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 reset terminal of the matching circuit MP is connected to the output terminal of an inverter gate connected to the output terminal of the trial shift register TSR. has been done. The trial clock generator OSC1 is also frequency-divided and input as a clock to the trial shift register TSR. Furthermore, the AND circuit AN2 performs a predetermined signal delay operation by taking the output simultaneous conditions of the trial shift register TSR, and after the output signal satisfies some logical conditions, it activates the output device. let First, as an 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 V1C is turned on, and the valve is opened by the load K2 of the transistor Q2.
After a while, timer TA or TB
The output signals are input to transistors Q3 and Q4, respectively, to drive the ignition control circuit IGC and operate the second valve control circuit V2C. 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. Further, K4 is a valve, and the first valve control circuit plays the role of a pilot valve in the case of gas fuel, and opens and closes the main valve in the case of heavy oil or the like. 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 configured in this way, the following
The operation will be explained with reference to the control circuit block diagram shown in the figure and the tom chart shown in FIG. In this figure 2, A is the normal combustion state of oil, B is the normal combustion state of gas, pre-ignition pre-purge period 1, post-ignition period 2, ignition trial period 3, and valve V2 delay period. 4. Power supply 5. Trial shortening function 6. Ignition establishment 7. Shortening of trial period after establishing ignition for gas combustion only 8.
shows. 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, first the thermo request signal generator TH
When activated, its output signal changes from L level to H level.
The signal that is inverted to the level and passed through the differential and integral circuit 1 is H.
It is input to the NAND circuit NA1 with the same level.
Since the other three input gates of the NAND circuit NA1 under the initial conditions are all initialized to H level, the output is inverted to L by this H trigger input signal and is input to the AND circuit AN3. However, since the AND circuit AN3 unconditionally keeps its output at the L level regardless of the levels of the other input gates, the output of the NAND circuit NA2 connected at the next stage is also kept at the H level. Therefore, a safety switch heater
A base current is supplied to the SSH transistor Q5 and the heater is turned on. On the other hand, an output line output in parallel with the heater transmits an L level signal to the inverter circuits IN1 and IN2 via a resistor.
The inverted signal H passed through the inverter circuit IN1 is D
- It is input to the AND circuit 4 via an FF (flip-flop) as an H signal. But that AND circuit
Since the other input gates of AN4 are at L level, the output signal is L, and the operation of memory circuits M1 and M2 remains unchanged, and the output signal of memory circuit M2 is L.
Shift register PSR for pre-purge without changing the level
is transmitted to the input of Also, since the output of the AND circuit AN5 is L, the fan motor output circuit BM
The transistor Q1 remains in the off state. The L signal transmitted to the input of the pre-purge shift register PSR is synchronized with the frequency-divided signal of the pre-purge clock OSC2, and the L signal of the pre-purge shift register PSR changes from the time the output of the NAND circuit NA1 switches to H level. The input is sequentially shifted to the output side by the clock via the AND circuit AN6. At the moment when this operation starts, one of the inputs of the AND circuit AN1 becomes L.
Since the level is inverted, the output naturally becomes H level. Then, the input of the pre-purge shift register PSR is switched to H again, the H level is sequentially shifted, and when all the outputs become H, the output of the NAND circuit NA1 also changes from L to H. This operation is an AND circuit
The output of AN3 is H and the output of NAND circuit NA2 is L.
The transistor Q5 is turned off and the heater is cut off, but the other output lines connected to its collector are instantaneously switched to H, so the output via the inverter circuit IN1 and D-FF is sent to the AND circuit AN4. For a moment, the simultaneous H level condition is met, and memories M1 and M2 become H level, and the AND circuit AN5
The output becomes H and the fan motor output circuit BM
transistor Q1 is turned on. Then, the output K1 is applied and the fan motor starts rotating. Thus, safe pre-combustion within the furnace is confirmed and the combustion gases are discharged to the outside by the fan. Also, depending on the initial operation, the inverter circuit IN
The H signal via 2 is sent to memories M3, M4 and the timer.
Reset TA and TB in advance. During this time, the first L input of the pre-purge shift register TSR takes a predetermined time to reach the final output. When the L signal is sent out, each output signal is again filled with the H signal, the H signal is shifted, and the H level is transmitted from the final terminal to the input shift terminal of the matching circuit MP. At this time, the matching circuit
The output Q terminal of MP is inverted to H level for the first time, and an H signal is input to the trial shift register TSR. As a result of this operation, the H signal synchronized with the clock of the trial clock generator OSC1 starts a shift operation. However, when that shift signal reaches the first output terminal of the register, the inverter circuit
Since IN3 is connected, matching circuit MP is immediately reset. Then, the output of the matching circuit MP is returned to the L level again, so the input of the shift register TSR also becomes L, continuing the shifting operation of the H signal with only one output. In the process, AND circuit AN7
When the signal via V1C sets the memory M3, the input H condition of the AND circuit AN8 is established, and the transistor Q2 of the first valve control circuit V1C turns on, opening the pilot valve in the case of gas. 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 timers TA and TB start operating. When the timer TA times up, the transistor Q3 of the ignition control circuit IGC is immediately activated.
The ignition operation is performed by the load K3. Subsequently, due to the time-up of the timer TB, the transistor Q4 of the second valve control circuit V2C is turned on, the valve K4 is activated, and the entire ignition is completed.

However, if even one through fault occurs in the flip-flop circuits that make up the trial shift register TSR (the L level of the input appears as is at the output and does not switch to the H level), the AND circuit AN2 is immediately inverted to L, and the AND circuit AN2 is immediately inverted to L. Circuit AN7
In addition to switching the output of
3. The output level of the NAND circuit NA2 is sequentially switched, and the output of the inverter gate IN2 becomes H level, and the memory M3 is reset and the ignition control circuit IGC below the first valve control circuit V1C,
A failsafe command to cut off the input is given to the second valve control circuit V2C.

In addition, if there is a failure in ignition, the flame detector FD monitors the ignition situation, so as soon as a misfire is confirmed, an H level output pulse signal is generated from the differentiating circuit 2, and the NAND circuit NA1 switches the first and second input gates of
Once the output of NA2 is switched to L, transistor Q5
Return to off state and switch its output to H level,
The signal H for returning to the initial stage 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. Thus, 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 indicated, and if ignition is not successful, an alarm signal is output, and the failure is communicated by an alarm or other means. NAND circuit also works when fuel is detected to be out of fuel.
Invert the output of NA1 to L, AND circuit AN8
Since the output of the AND circuit AN5 is made to be L, the output circuit for the fan motor BM, the first valve control circuit V1C, and the ignition control circuit are
Naturally, IGC and second valve control circuit V2C are switched off to perform fail-safe operation.

Therefore, according to the present invention, from the generation of the thermorequest signal that promotes ignition, the rotation of the fan motor, the ON operation of the safety switch heater in the furnace, and the operation of the ignition control circuit following the opening of the pilot valve, the pilot ignition, and the main control. The series of sequence operations with the valve opening operation is linked with the timer operation of the pre-purge shift register and the sequential operation of the trial shift register, and the extremely precise timing operation leads to ignition and complete fire, so anyone can make a mistake. In addition to ensuring safe operation, the final output load will never operate in a dangerous manner even if a through failure occurs in a circuit such as a flip-flop that makes up the trial shift register at the start of an ignition operation or during combustion equipment operation. This is to quickly stop the output load. In addition, even in the event of a misfire, a safety confirmation operation can always be carried out in conjunction with the flame detector, and even in the event of fuel shortage, the load output is guided to a fail-safe operation, resulting in reliable operation. In addition to ensuring performance, a highly functional digital combustion control device can be constructed using 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 In the digital combustion control device that enters the ignition trial operation after the pre-purge operation time ends, the thermo request signal generator TH generates a signal that prompts the initial ignition of the combustion device, and the pulse frequency divided from the time the power is turned on. a trial clock generating section OSC1 that generates a signal, a trial shift register TSR that transfers a signal by a pulse from the trial clock generating section, and a trial shift register TSR that performs signal transition after the pre-purge operation time ends.
A matching circuit with a memory function that provides an output signal to the input gate of the TSR and returns the output signal of the inverter gate IN3 connected to the first output port of the trial shift register to the reset terminal.
MP, a first AND circuit AN2 whose inputs are all output ports other than the first output port of the trial shift register TSR, and the first AND circuit
A second AND circuit AN7 that obtains a logical product between the output signal of AN2 and the reset signal of the matching circuit MP.
, a memory circuit M3 whose set input is the output signal of the second AND circuit AN7, and the memory circuit M3.
a third AND circuit AN8 which obtains a logical product between the output signal of the thermostat and the output signal of the thermo-required signal generator TH
and receiving the output signal of the third AND circuit, the first
First valve control circuit V1 that opens and closes the valve
A digital combustion control device characterized by being equipped with C.