JPH01244215A - Combustion device - Google Patents

Abstract

PURPOSE:To provide a combustion unit having a simple constitution and capable of sensing a rapid variation of combustion state without requiring any separate installation of a combustion sensor by a method wherein a glow plug installed within a combustion chamber serves as a glow-plug on ignition and serves as a combustion sensor during combustion. CONSTITUTION:Fuel supplied from a fuel pipe 9 is evaporated due to a high temperature of a combustion chamber 2 to generate a fuel gas. The gas is ignited by a ceramic glow plug 8. After ignition of fuel, the ceramic glow plug 8 is connected to a combustion sensing circuit 21 and serves as a combustion sensor. That is, a specified current is made to flow from a specified current circuit 30 to the ceramic glow plug 8, the voltage of the ceramic glow plug 8 thus generated is sensed, and this value and a reference voltage of a power supply 29 are compared with each other by a comparator circuit 27. In the case that a detected voltage is higher than the reference voltage, it is judged that the combustion chamber 2 is under its ignited condition. In turn, in the case that it is lower than the reference voltage, it is judged that the flame is not ignited or stop of combustion and then an output voltage of the comparator circuit 27 becomes a voltage for a specified voltage circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a combustor, and more particularly to combustion detection in a combustor.

[Conventional technology]

Conventionally, in a combustor, a glow plug made of nichrome wire is used as an ignition source in a combustion chamber. Further, a combustion detection sensor such as a bimetallic thermos inch is attached to the heat exchanger containing the combustion chamber to detect the combustion state.

[Problem to be solved by the invention]

As in the above configuration, in the conventional combustor, the glow plug and the combustion detection sensor are separately attached, leading to an increase in cost due to an increase in the number of parts.

Furthermore, since the combustion detection sensor is attached outside the combustion chamber, there is a problem in that it takes a long time to detect when a change in the combustion state such as a misfire occurs within the combustion chamber.

The present invention was made in view of the above-mentioned problems, and an object of the present invention is to provide a combustor that has a simple configuration and can quickly detect changes in the combustion state.

[Means for Solving the Problems] Therefore, a combustor according to the present invention includes: a glow plug that is installed in a combustion chamber and whose resistance value changes depending on temperature; and a heat generating circuit that causes the glow plug to generate heat and ignites fuel. and a combustion detection circuit that recognizes a combustion state by detecting a resistance value of the glow plug, and a control means that controls switching of connection of the heat generation circuit and the combustion detection circuit to the glow plug. And so.

[Effect]

According to the above configuration, the glow plug and the heating circuit are connected by the control means at the time of ignition. The heating circuit supplies a heating current to the glow plug to generate heat. Thereafter, the control means disconnects the glow plug from the heat generating circuit and connects the glow plug to the combustion detection circuit.

Here, the glow plug used is a ceramic glow plug whose resistance value changes depending on the temperature. Therefore, the combustion state of the combustor can be recognized by detecting the resistance value of the glow plug installed in the combustion chamber.

[Effects of the Invention] As described above, in the present invention, the glow plug installed in the combustion chamber serves as a glow plug during ignition and as a combustion detection sensor during combustion. For this reason,
There is no need to separately provide a glow plug and a combustion detection sensor, and it is possible to reduce costs and improve work efficiency. Furthermore, since the glow plug is installed within the combustion chamber, it is possible to immediately detect temperature changes due to changes in combustion conditions.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. The overall configuration when an evaporative combustor is applied to a vehicle combustion heater is shown. In FIG. 1, 10 is a substantially cylindrical heater case made of metal. Heat exchanger 1 is installed within heater case 10 and heats heating air. 3 is a combustion air intake pipe, and 4 is a combustion air exhaust pipe, through which air necessary for combustion is taken in and exhausted. The combustion fan 5 has three blades and sends combustion air into the combustion chamber 2 from the combustion air intake pipe 3. The heating fan 7 sucks heating air into the heater case 10. These combustion fan 5 and heating fan 7 are driven by an electric motor 6. The ceramic glow plug 8 has a tip portion made of a ceramic material 8a of Si, +N, (silicon nitride), and the ceramic material 8a is provided in the combustion chamber 2.
inserted inside. A tungsten wire serving as a heat source is embedded inside this ceramic material 8a. The fuel pipe 9 drips fuel from a fuel pump (not shown) into the vicinity of the ceramic material 8a. Reference numeral 11 denotes a drain pipe, which opens to the combustion air exhaust pipe 4. Note that the ceramic material 8a may be one in which the ceramic itself becomes a heat source,
In this case, the ceramic material 8a is made of, for example, Mo5iz (molybdenum silicide).

The operation of the above configuration will be explained.

Since the temperature inside the combustion chamber 2 is high, the fuel supplied from the fuel pipe 9 evaporates into fuel gas, which is ignited by the ceramic glow plug 8 . In contrast, combustion air is fed into the combustion chamber 2 from the combustion air intake pipe 3 by the combustion fan 5 . In the combustion chamber 2, fuel gas and combustion air are mixed and combusted, producing high-temperature gas. The high temperature gas undergoes heat exchange in the heat exchanger 1 and is discharged to the outside from the combustion air exhaust pipe 4.

On the other hand, heating air is drawn into the heater case 10 by a heating fan 7 driven by a motor 6. The sucked heating air passes through the outer wall of the heat exchanger 1, undergoes heat exchange there, becomes warm air, and flows into the vehicle interior from the heater case IO.

FIG. 2 shows a control circuit for a combustion type heater. Reference numeral 21 denotes a combustion detection circuit, which includes a comparison circuit 27, a power supply 29 that generates a basic lightning voltage, a constant current circuit 30, a constant voltage circuit 31, and a resistor 33.
When the main switch 22 composed of a diode 34 is closed, a current is applied to the relay coil 33b via the OR circuit 34. Then,
The normally open relay contact 33a closes and power is supplied to the controller 28. From the moment power is applied, controller 2 applies current to the other input of OR circuit 34. This current is output during the scavenging operation (steps 90 to 110 in FIG. 4) even if the main switch 22 is turned off, and power is supplied to the controller 28.

23a is a normally open relay contact, and this relay contact 23a
When the ceramic glow plug 8 is closed, enough current is supplied from the power source 32 to cause the ceramic glow plug 8 to generate heat as a glow plug. When the relay coil 23b is energized by the controller 28, it closes the relay contact 23a. That is, a circuit constituted by the power supply 32, the relay contact 23a, and the relay coil 23b corresponds to a heat generating circuit.

When the normally open relay contacts 24a and 25a close, power is supplied to the motor 6 and fuel pump 26, respectively. When relay coils 24b and 25b are energized by controller 28, they close corresponding relay contacts 24a and 25a, respectively.

The operation of the above configuration will be explained based on the control circuit shown in FIG. 2 and the flowchart shown in FIG. 4.

When the main switch 22 is closed, the controller 28
Power is supplied to the controller, and the flowchart shown in FIG. 4 starts.

In step 10, the T, timer, and T2 timers are started, and at the same time, current is applied to the relay coil 23b in order to connect the ceramic glow plug 8 and the heating circuit.

In step 20, it is determined whether a predetermined time T has elapsed or not, and when the predetermined time T1 has elapsed, the process proceeds to step 30. This predetermined time T is a preheating time of the combustion chamber.

In step 30, current is applied to the relay coil 25b so that fuel is supplied from the fuel pump 26 to the combustion chamber 2 via the fuel pipe 9. At the same time, by supplying power to the motor 6, current is applied to the relay coil 24b to drive the combustion fan 5 and the heating fan 7.

In step 40, it is determined whether a predetermined time T2 has elapsed, and when the predetermined time T2 has elapsed, the process proceeds to step 50. During this predetermined time T2, the ceramic glow plug 8 generates heat as a glow plug and ignites the fuel.

In step 50, energization to the relay coil 23b is ended, and power supply to the combustion detection circuit 21 is started.

The ceramic glow plug 8 will now be explained. As shown by the solid line A in FIG. 3, the ceramic glow plug 8
The resistance value also increases as the temperature increases. Therefore, at the time of ignition, the ceramic glow plug 8 is connected to the heating circuit and the temperature range shown by B in FIG.
1150°C) and ignites the fuel. Thereafter, the ceramic glow plug 8 is connected to the combustion detection circuit 21 and serves as a combustion detection sensor. That is, a constant current is passed from the constant current circuit 30 to the ceramic glow plug 8, and the voltage Z (v) of the ceramic glow plug 8 generated thereby is detected. The comparison circuit 27 compares this detected voltage Z(v) with the reference voltage Y(v) from the power supply 29. As a result, the detected voltage Z +v+ is equal to the reference voltage Yc
v) If it is larger than , it is determined that the combustion chamber 2 is in a combustion state. At this time, the output voltage A is output from the comparator circuit 27 to the controller 28. is OfV). Conversely, if the detection voltage Z fV) is smaller than the reference voltage Y (I), it is determined that there is no ignition or a misfire during combustion. At this time, the output voltage A (V) of the comparison circuit 27 is equal to the voltage X of the constant voltage circuit. (V).Here, by changing the reference voltage Y (v) according to the characteristics of the combustor, as in the temperature range (500°C to 1100°C) shown by C in Figure 3, , combustion detection set temperature T, can be set arbitrarily.

In step 60, the output type rEA (
v+ is 0. v, judge whether or not. If the output voltage A(v
) is 0. v, otherwise proceed to step 70.

In step 70, based on the determination result in step 60, it is assumed that the combustion chamber 2 is currently in a non-combustion state, and the relay coil 2
4b, 25b is terminated.

That is, when a non-combustion state is detected, the supply of fuel to the combustion chamber 2 and the drive of the motor 6 are immediately stopped.

If it is determined in step 60 that the output voltage A(v) is 0(v), that is, in a normal combustion state, the process proceeds to step 80. In step 80, a determination is made as to whether the main switch 22 has been turned off. If the main switch 22 is not turned off, the process returns to step 60. During subsequent operation of the combustor, steps 60 and 80 are repeated until the main switch 22 is turned off.

If it is detected in step 80 that the main switch 22 has been turned off, the process proceeds to step 90.

In step 90, the T4 timer is started, and at the same time, the power supply to the relay coil 25b is stopped, and the fuel pump 2
Cut off the power supply to 6. In this way, the supply of fuel stops when the main switch 22 is turned off.

In step 100, it is determined whether a predetermined time T4 has elapsed. Then, when the time T1 has elapsed, the process proceeds to step 110. During this predetermined time T4, the motor 6 is driven to send combustion air into the combustion chamber 2, thereby performing a scavenging operation in which combustion gas and fuel gas are discharged to the outside.

In step 110, the relay coil 24b is de-energized and the motor 6 is stopped.

In step 120, it is determined whether the main switch 22 is turned off when the motor 6 stops. At this time, if it is determined that the main switch 22 is turned off, the operation of the system is completely stopped. On the other hand, when the main switch 22 is closed, the process returns to step 10 and control in the initial state is started. That is, even if the main switch 22 is closed during the scavenging operation performed in the steps 90 to 110 by turning off the main switch 22, a new operation cannot be started unless the scavenging operation is completed. do not have.

Hereinafter, the control of the controller 28 according to various cases will be explained in detail based on the drawings. However, in the time charts from FIG. 5 to FIG. 10, the operating state is shown by diagonal lines.

FIG. 5 shows a time chart when the fuel is normally ignited and enters a combustion state, and FIG. 9 shows the temperature change at this time.

The controller 28 starts energizing the relay coil 23b at the same time as the main switch 22 is turned on. After a predetermined time T from the time when the main switch 22 was turned on,
The controller 28 starts energizing the relay coils 24b and 25b, and supplies power to the motor 6 and fuel pump 26. Then, when the ceramic glow plug 8 generates heat as a T2 glow plug for a predetermined period of time, the controller 28 stops supplying power to the heat generating circuit. At the same time, the controller 28
connects the ceramic glow plug 8 and the combustion detection circuit 21, and the ceramic glow plug 8 starts functioning as a combustion detection sensor. Thereafter, when the normal combustion state continues and the main switch 22 is turned off to end the operation, the controller 28
2 is turned off, the supply of power to the fuel pump 26 is stopped. Thereafter, the motor 6 continues to operate for a predetermined time T4 to prevent combustion and fuel gas from accumulating in the heater case 10.

FIG. 6 is a time chart showing the case of misfire, and FIG. 1O shows the temperature change at this time.

The ceramic glow plug 8 generates heat as a glow plug for a predetermined time T2 by a heating circuit.

However, if the fuel is not ignited even after the predetermined time T2 has elapsed, the detected voltage Z (V
), the combustion detection circuit 21 detects misfire after the misfire detection time T3. Then, the controller 2 stops power supply to the fuel pump 26 and motor 6. This misfire detection time T3 is a very short time (approximately 10 to 20
seconds).

FIG. 7 is a time chart when a misfire occurs during combustion, and FIG. 11 shows the temperature change at this time.

If a misfire suddenly occurs from a state where the combustion was normal until then, the ceramic glow plug 8 detects that a misfire has occurred after the misfire detection time T has elapsed.

Then, the controller 28 controls the fuel pump 26 and the motor 6.
Stop supplying power to. This misfire detection time T5
is a very short time (approximately 10 to 20 seconds) required for the temperature inside the fuel chamber 2 to cool down to the combustion detection set temperature T.

FIG. 9 is a time chart when the main switch 22 is turned on again while the main switch 22 is turned off and scavenging operation is being performed.

At this time, even if the main switch 22 is turned on again, the scavenging operation continues for the predetermined time T4. Thereafter, the controller 28 performs control in a normal initial state.

Although the present embodiment has been described using an evaporative combustor, the present invention is also applicable to a low-pressure combustor.

[Brief explanation of the drawing]

Fig. 1 is a control circuit for a combustor heater which is an embodiment of the present invention, Fig. 2 is a sectional view showing the entire configuration of a combustion type heater, and Fig.
The figure is a temperature characteristic diagram of the ceramic glow plug, Figure 4 is a flowchart of the controller 28, Figures 5 to 8 are time charts showing the control of the main amplifier, and Figure 9 is a time chart showing the control of the main amplifier.
Figures 1 to 11 are graphs representing temperature changes of ceramic materials. 8... Ceramic glow plug, 8a... Ceramic material, 21... Combustion detection circuit, 22... Main amplifier ~ f-, 23a... Relay contact (glow plug),
23b... Relay coil (glow plug), 24b...
... Relay contact (motor), 24b... Relay coil (motor), 25a... Relay contact (fuel pump),
25b...Relay coil (fuel pump), 27...
Comparison circuit, 28... Controller, 29... Power supply,
30... constant current circuit, 31... constant voltage circuit, 33a
...Relay contact (controller), 33b...Relay coil (controller), 34...OR circuit. Representative Patent Attorney Takashi Okabe Figure 2 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9!

Claims (1)

[Scope of Claims] A glow plug installed in a combustion chamber and whose resistance value changes depending on temperature; a heat generating circuit that generates heat in the glow plug to ignite fuel; and detecting the resistance value of the glow plug. A combustor comprising: a combustion detection circuit that recognizes a combustion state by; and a control means that controls switching of connection of the heat generation circuit and the combustion detection circuit to the glow plug.