BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a pot type oil burner, and more particularly to
a pot type oil burner capable of suppressing diffusion of an incomplete combustion
gas generated during the extinction operation of the pot type oil burner into a room
while preventing the generation of the same gas.
Description of the related art
[0002] In generally, when the pot type oil burner is to be extinguished, the supply of a
fuel into a pot is stopped and a combustion fan for feeding combustion air into the
pot and a convection fan for feeding blowing air into a room are maintained to be
rotated, and the fuel remaining in the pot is continuously combusted, thereby burning
out the fuel in the pot and thus carrying out the extinction. The rotation of the
combustion fan and the convection fan is continued until a frame body of the burner
and the pot reaches a low temperature so that the frame body can be prevented from
reaching a high temperature. However, a bad odor is generated in a process for completely
burning out the unburnt fuel.
[0003] Therefore, there has conventionally been proposed a technique for preventing the
bad odor from being generated during the extinction of the pot type oil burner. In
a technique described in Japanese Utility Model Publication No. 3-35956 (1991), a
combustion fan and a convection fan for feeding air into a room together with a combustion
gas are stopped immediately after an extinction operation. According to this technique,
an incomplete combustion gas can be prevented from being flowing from a pot, and furthermore,
oxidization of an unburnt gas remaining in the pot in a high temperature state is
accelerated therein in order to suppress the generation of a bad odor. In the pot
type oil burner, however, even if a very long time passes after the extinction operation
is started, the fuel remaining in a fuel feeding pipe may enter into the pot in some
cases. For this reason, when the fan are stopped as in the conventional art, the fuel
is collected in the pot and it takes a long time to decrease the temperature of the
pot. Therefore, a frame body having the pot accommodated therein is locally heated
and is brought into a dangerous state.
[0004] According to the technique described in the Japanese Utility Model Publication No.
60-36833 (1985), the direction of rotation of an indoor fan is reversed during the
extinction operation and a combustion gas is bllowed out from the back side of a frame
body of a burner. In the conventional art, a bad odor (an unburnt gas) can be prevented
from blown out toward the side of a user of the burner during extinction such that
the user does not smell the bad odor or malodor. However, a driving motor capable
of instantaneously reversing the rotational direction is a very special motor, and
an inexpensive motor such as an AC induction motor to be generally used cannot be
utilized.
[0005] Moreover, there has conventionally been proposed that the structure of the pot is
devised to reduce a fuel remaining in a liquid state in the pot as much as possible,
thereby lessening the amount of generation of the bad odor. However, this technique
cannot sufficiently prevent the user from smelling the bad odor (incomplete combustion
gas).
[0006] It is an object of the present invention to provide a pot type oil burner capable
of preventing the user from being noticing or feeling the generation of an incomplete
combustion gas.
[0007] It is another object of the present invention to provide a pot type oil burner capable
of preventing a flame from going out during extinction operation, thereby lessening
the amount of generation of the incomplete combustion gas.
[0008] It is a further object of the present invention to provide a pot type oil burner
capable of preventing the user from noticing or feeling the generation of the incomplete
combustion gas by using a fan having an inexpensive motor as a driving source.
SUMMARY OF THE INVENTION
[0009] A pot type oil burner to be improved by the present invention comprises a frame body
having an air outlet in a front part thereof, a cylindrical bottomed pot provided
in the frame body and having a large number of through holes for air flow on a peripheral
wall, a combustion fan including a first motor as a driving source and serving to
supply combustion air into the pot through the through holes, combustion fan control
means for controlling rotation of the first motor, thereby controlling an amount of
air flow from the combustion fan, fuel feeding means for feeding a fuel into the pot
through a fuel feeding pipe, fuel feeding control means for controlling a driving
operation of the fuel feeding means, an electric heater to be energized from a start
of ignition to a start of combustion, thereby heating the pot, heater control means
for controlling the energization to the electric heater, a convection fan including
a second motor as a driving source, attached to the frame body to feed air from an
outside of the frame body into the frame body and to blow out the air into a room
through the air outlet together with a combustion gas discharged from the pot, fan
control means for controlling rotation of the second motor, thereby controlling an
amount of air flow from the fan, and a control command generator for giving a control
command to the combustion fan control means, the fuel feeding control means, the heater
control means and the convection fan control means, respectively.
[0010] In the present invention, the control command generator is operated in the following
manner. First of all, the control command generator outputs a fuel feeding stop command
for stopping the driving operation of the fuel feeding means to the fuel feeding control
means and outputs a heater energization command to the heater control means, in order
to energize the heater for a predetermined first time period which is longer than
a time period required for completely ending combustion, when an extinction command
is input. Moreover, the control command generator outputs a rotation decrease command
for decreasing the rotation of the second motor to the convection fan control means
so as to decrease the amount of air from the convection fan after a predetermined
second time period equivalent to a time period to be considered to start incomplete
combustion after the extinction command is input passes, while a predetermined third
time period to be considered to be required for reducing a combustion flame or extinguishing
the flame in the pot then passes. Then, the control command generator outputs a fan
stop command for stopping the combustion fan and the convection fan to the combustion
fan control means and the convection fan control means after the first time period
is ended.
[0011] In the present invention, the supply of the fuel is stopped during the extinction
operation. Originally, the electric heater which is used for only the ignition operation
is also used for the extinction to heat the pot such that the combustion flame does
not go out in the pot during the extinction operation. Accordingly, it is possible
to almost completely combust the unburnt gas in the pot. After the extinction is completed,
a cracked gas is generated if the fuel remains in the pot. Consequently, a bad odor
having a hard irritating smell is sprayed onto a user through the wind of the convection
fan. However, even if the fuel remaining in the fuel pipe enters the pot after the
extinction is completed, the fuel is oxidized with the air fed into the pot through
the combustion fan in the high temperature atmosphere heated by the electric heater.
Consequently, it is possible to prevent the bad odor from being generated from the
fuel remaining in the pot.
[0012] In the present invention, particularly, the rotational speed of the convection fan
is decreased for a period in which incomplete combustion might be generated after
the extinction operation is started (that is, in the third time period) or thereafter
(after the combustion flame is reduced or the extinction is carried out). Consequently,
the flow velocity of the air blown out of the air outlet of the frame body is decreased.
As a result, the air containing an incomplete combustion gas is raised in the room
space without reaching the user present in the forward part of the frame body. Therefore,
it is hard for the user to notice the generation of the incomplete combustion gas.
The degree of the decrease in the rotation of the convection fan belongs to the range
of design items. It is preferable that the rotational speed should be decreased without
locally raising the temperature of the frame body such that the air containing the
combustion gas blown out of the air outlet can be raised upward as rapidly as possible
or immediately.
[0013] After the combustion of the unburnt gas is completed, it is preferable that the rotational
speed of the convection fan should be raised. Thus, the frame body and the pot can
be cooled in the early stage.
[0014] It is preferable that the speed of the convection fan should be decreased in a short
time . If the forced braking means is provided on the motor for the convection fan,
the rotational speed of the convection fan can be forcedly decreased to be a low speed.
[0015] Moreover, the rotational speed of the convection fan may be maintained to be constant
in a low speed region or may be reduced gradually. However, if the rotational speed
of the convection fan is reduced as required or more, there is a possibility that
the temperature of the frame body might be raised excessively. The rotational speed
of the motor to be used as the driving source of the convection fan is monitored by
the rotational speed detecting means. If the rotational speed of the motor is decreased
lower than a predetermined rotational speed, it is preferable that the rotational
speed of the convection fan should be increased.
[0016] Moreover, when the combustion flame in the pot is reduced, the incomplete combustion
gas is easily generated. Therefore, the flame detecting means for detecting a flame
is used to detect the size or the height of the flame in the pot. If the size of the
flame is smaller than a predetermined size, the rotational speed of the combustion
fan may be decreased. Thus, the extinction can be carried out with an almost good
balance of an air / fuel ratio between the unburnt gas and the air. Consequently,
the amount of generation of the incomplete combustion gas can be decreased. According
to the pot type oil burner of the present invention, ignition and combustion in a
normal combustion state are controlled in the same manner as a conventional product.
[0017] These objects as well as other objects, features and advantages of the present invention
will become more apparent to those skilled in the art from the following description
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018]
Fig. 1 is a schematic sectional view showing a pot type oil burner according to an
embodiment of the present invention;
Fig. 2 is a block diagram showing the structure of a combustion control device to
be used in the embodiment; and
FIG. 3 is a flow chart showing an algorithm of software to be used in the case in
which a main part of control command generating means illustrated in Fig. 2 is constructed
by utilizing a microcomputer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0019] An embodiment of the present invention will be described below in detail with reference
to the drawings. Fig. 1 is a sectional view showing an example of the structure of
a pot type oil burner (a hot air type heater or a fan heater) according to the present
invention. Since a basic structure is well known, it will be described briefly. In
Fig. 1, the reference numeral 1 denotes a frame body having an hot air outlet 3 provided
on a front wall. The inside of the frame body 1 is partitioned into three chambers
by partition walls 5 and 7. The chamber formed between the partition walls 5 and 7
acts as a flow path 9. A convection fan 11 for feeding the room air into the flow
path 9 is provided in the frame body 1. The convection fan 11 has an inexpensive motor
13 such as an AC induction motor as a driving source. A pot 15 is provided in the
chamber formed under the partition wall 7. The pot 15 in a cylindrical shape having
a bottom and is provided with a large number of through holes 17 at a peripheral wall
with cause an air to flow into the pot 15. A cylinder 19 is provided on the outside
of the pot 15, and an air duct 21 is formed between the pot 15 and the cylinder 19.
A hole for causing the air to pass is formed in a bottom wall portion of the cylinder
19, and a combustion fan 23 is provided under the bottom wall portion. The combustion
fan 23 is rotated by using a motor 25 as a driving source. In this specification,
the motor 25 constitutes a first motor, and the motor 13 constitutes a second motor.
When the combustion fan 23 is rotated, the air is sucked through a sucking port 27
and is supplied from the air duct 21 into the pot 15 through the through holes 17.
[0020] A combustion cylinder 29 forming a combustion chamber 28 is provided on the pot 15.
The combustion chamber 28 is opened toward the flow path 9, and room air sucked through
the convection fan 11 is mixed with a hot combustion gas flowing from the combustion
chamber 28 and is blown out as hot air from a hot air outlet 3 provided in the front
wall of the frame body 1. Moreover, an electric heater 31 constituted by a ceramic
heater or the like is provided to penetrate through the peripheral wall portion of
the pot 3. The heater 31 is provided to form a small gap together with the bottom
portion of the pot 15, and serves to heat the bottom wall portion of the pot 15 and
a stabilizing member 16 in the pot 15. Furthermore, the reference numeral 33 denotes
an oil pan for receiving a fuel from a fuel tank which is not shown and for forming
a constant oil surface therein. Moreover, the reference numeral 35 denotes a fuel
pump including an electromagnetic pump provided on the oil pan 33, and draws up the
fuel in the oil pan 33 through the fuel pump 35 and supplies the fuel into the pot
15 through a fuel feeding pipe 37. The pump 35 constitutes fuel feeding means.
[0021] Well-known flame detecting means 39 for detecting the size or height of a combustion
flame in the pot 15 is provided above the opening of the pot 15. The flame detecting
means 39 serves to detect that the combustion flame is generated in a normal condition
or not, and to detect the top position of the flame based on a difference between
a current (flame current) I obtained when the flame touches an electrode of the flame
detecting means 39 and a current obtained when it does not touch the same electrode.
Accordingly, the output of the flame detecting means 39 is the current I. When the
flame detecting means 39 does not detect the flame, the combustion flame is very small
and is brought into an extinction state soon or completely goes out.
[0022] A control switch including an ignition switch 41 and an extinction switch 43 is provided
on a top plate of the frame body 1, and a combustion control device 45 (Fig. 2) which
is not shown is provided in a space formed below the top plate.
[0023] Fig. 2 is a block diagram schematically showing the structure of the main part of
the combustion control device 45. Fig. 3 is a flow chart showing an algorithm of software
to be used in the case in which the main control portion of a control command generator
47 used in the combustion control device 45 during an extinction operation is constructed
by using a microcomputer. The ignition operation and the combustion control operation
which are to be carried out after pressing down the ignition switch 43 are executed
through the ignition and combustion control section 46. The ignition and combustion
control section 46 serves to control the electric heater 31, the first and second
motors 25 and 13 and the fuel pump 35 to be the fuel feeding means, to carry out the
ignition operation and the combustion operation. The operations are well known and
will be briefly described because they are not particularly related to the gist of
the present invention. When the ignition switch 43 is turned on, the ignition and
combustion control section 46 energizes the electric heater 31 to heat the pot 15.
When the temperature of the pot 15 increases equivalent to that obtained during normal
combustion, the ignition and combustion control section 46 gives commands to fuel
feeding control means 51 and combustion fan control means 49 so that the fuel feeding
means 35 and the combustion fan 23 supply the fuel and the air to the pot 15. At this
time, the inside of the pot 15 to which the fuel and the air are supplied is set in
a high temperature atmosphere. Therefore, the combustion is starts combustion immediately.
Moreover, when the combustion is started in the pot 15, the ignition and combustion
control section 46 outputs a command to fan control means 55, thereby rotating the
convection fan 11. As a result, the hot combustion gas and the room air are blown
out from the hot air duct 3 into the room together.
[0024] The combustion control device 45 includes the combustion fan control means 49, fuel
feeding control means 51, heater control means 53, fan control means 55, forced braking
means 57 and rotational speed detecting means 59 in addition to the ignition and combustion
control section 46 and the control command generator 47. The combustion fan control
means 49 controls the rotation of the first motor 25 of the combustion fan 23, thereby
controlling the amount of air flow from the combustion fan 23. The fuel feeding control
means 51 controls the driving operation of the fuel feeding means 35. The heater control
means 53 controls the energization to the electric heater 31. Furthermore, the convection
fan control means 55 controls the rotational speed of the second motor 13 of the convection
fan 11, thereby controlling the amount of air flow from the convection fan 11. Moreover,
the forced braking means 57 causes a DC current to flow to an exciting winding of
the second motor 13, thereby forcibly applying braking, and is operated in accordance
with a command from the convection fan control means 55.
[0025] The control command generator 47 includes fuel feeding stop command generating means
61 for outputting a fuel feeding stop command for stopping the driving operation of
the fuel feeding means 35 to the fuel feeding control means 51 when the extinction
switch is pressed down to input a command for extinction. The fuel feeding stop command
generating means 61 has the function of detecting the input of the extinction command.
At steps ST1 and ST2 in Fig. 3, the fuel feeding stop command generating means 61
is realized.
[0026] When the extinction switch 41 outputs an extinction command, a first timer 63 starts
counting and counts a predetermined first time period T1 (time) which is longer than
a time period required for completely ending the combustion in the pot 15. Heater
energization command generating means 65 outputs, to the heater control means 53,
a heater energization command for energizing the heater 31 to heat the pot 15 until
the first timer 63 completely counts the first time period T1. When the first timer
63 ends the counting, the heater energization command generating means 65 stops the
output of the heater energization command so that the energization of the heater 31
is stopped. In the example of Fig. 3, the first timer 63 is realized by steps ST1,
ST3 and ST17. Moreover, the heater energization command generating means 65 is realized
by steps ST3 and ST18.
[0027] Furthermore, when a second timer 67 receives the extinction command, the second timer
67 starts counting a second time period T2 required for reducing the combustion flame
in such manner to start generating incomplete combustion. In other words, the second
time period T2 is equivalent to a time period for which a large amount of unburnt
gases remaining in the pot 15 can combust in the normal combustion in the pot 15.
However, it is a matter of course that the time period T1 does not need to be accurate
and may be previously obtained by an experiment roughly to some extent. For the second
time period T2, the air flows in a path shown in a solid-line arrow and the combustion
gas generated in the pot 15 is blown out far away from the hot air outlet 3 together
with the indoor air. When the second time period T2 passes, the amount of the unburnt
gas in the pot 15 is decreased so that a good balance between the amount of the air
to be supplied to the pot 15 and the remaining unburnt gas cannot be obtained and
an incomplete combustion gas having a bad odor is generated. After the second timer
67 completes the counting of the second time period T2, a third timer 69 starts to
count a third time period T3 required for almost completely combusting the unburnt
gas remaining in the pot 15 (or required for considerably reducing the combustion
flame or extinguishing the flame). The third time period T3 may also be predetermined
by an experiment roughly to some extent. First rotation decrease command generating
means 71 outputs a rotation decrease command for decreasing the rotational speed of
the second motor 13 to the convection fan control means 55 to reduce the amount of
air of the convection fan 11 while the third timer 69 carries out the counting the
third time period T3 after the second timer 67 ends to count the second time period
T2. The degree of a decrease in a rotational speed in response to the rotation decrease
command is determined such that the hot air blown out of the outlet 3 of the frame
body 1 is raised upward (toward a ceiling in the room) according to a natural convection
as early as possible and the temperature of the frame body 1 is not locally raised.
For example, in the case in which the second motor 13 is rotated at 1500 rpm, the
rotational speed of the second motor 13 can be reduced to approximately 500 rpm. In
the case in which the rotational speed of the second motor 13 is reduced to a predetermined
low speed, it is preferable that the rotational speed should be reduced in a time
which is as short as possible. When the time is prolonged, there is a higher possibility
that the incomplete combustion gas might reach a place where the user is present.
In the case in which an induction motor is to be phase-controlled, it is difficult
to rapidly reduce the rotational speed. In this example, therefore, the forced braking
means 57 is used. The forced braking means 57 serves to cause a DC current to flow
to the exciting winding of the second motor 13, thereby applying DC braking. When
the rotation decrease command is input to the convection fan control means 55, the
forced braking means 57 applies the forced braking to the second motor 13 in a short
time. Preferably, a time for which the braking is applied is approximately one second,
for example. After the braking is released, the second motor 13 is rotated at a low
speed under control of the convection fan control means 55 in response to the rotation
decrease command. The convection fan control means 55 is operated to reduce the rotational
speed of the second motor 13 to be a predetermined low speed while receiving the rotation
decrease command, and carries out control such that the second motor 13 is rotated
at rated speed if the rotation decrease command is not given. In this state, the flow
of the hot air shown in a broken-line arrow of Fig. 1 is obtained. The hot air is
sent to the outside through the hot air outlet 3 and is exactly fed toward the ceiling
in the room through a natural convection. As a result, a bad odor contained in the
combustion gas does not reach the user who is front in the forward of the frame body
1, and the user does not notice the generation of the bad odor. The conditions for
stopping the fan will be described later. In the example of Fig. 3, the second timer
67 is realized by steps ST1, ST5 and ST6 and the third timer 69 is realized by steps
ST8 and ST12.
[0028] In this example, the electric heater 31 is set in a heating state for the third time
period T3 and the inside of the pot 15 is maintained at a high temperature in the
same manner as that in the combustion. At this time, accordingly, even if the combustion
air is continuously fed into the pot 15, the pot 15 can be prevented from being cooled
by the air and the combustion flame is not extinguished easily. Therefore, the combustion
can be continuously carried out until the unburnt gas is gone, and a large amount
of incomplete combustion gas can be prevented from being generated rapidly. When the
third time period T3 is set to such a time, the bad odor generated during the extinction
of the combustion flame has already been almost decreased at the end of the third
time period T3 even if the extinction time period is varied due to the amount of fuel
remaining in the pot 15 and the amount of unburnt gas. Consequently, even if the rotational
speed of the convection fan 11 is then increased, the user does not smell the bad
odor.
[0029] In this example, the convection fan control means 55 gradually reduces the rotational
speed of the second motor upon receipt of the rotation decrease command such that
the incomplete combustion gas is not blown out far away if possible. In order to implement
the foregoing, after the rotational speed of the convection fan 11 is reduced by the
forced braking means 57, the deceleration operation of the forced braking means 57
is then stopped and the energization of the second motor 13 is stopped. Consequently,
such a change in the rotational speed can be implemented easily. After the energization
of the second motor 13 is stopped, the second motor 13 is continuously rotated with
inertia. Therefore the rotational speed of the fan 11 is gradually reduced so that
the discharge amount of the combustion gas and the rotational speed can also be caused
to approximate to each other. Referring to the reduction in the rotational speed with
the inertia, however, the rotation of the fan 11 is sometimes stopped before the third
timer 69 completes the counting depending on the conditions of disturbance in which
a blast is jetted onto the fan 11 or when the user does not carry out maintenance
in years so that the fan is dusty or the fan is out of lubricating oil. If such a
situation occurs and the combustion is being continuously carried out at that time,
the air feeding path 9 and the frame body 1 are instantaneously set to a high temperature
after the air feeding is stopped, and particularly, a large amount of dust sticks
to the air feeding path 9 and the convection fan 11 when maintenance failures are
caused so that the dust might be ignited to cause fire accidents. In order to eliminate
such problem, in this example, the rotational speed of the motor 13 to be used as
the driving source of the convection fan 11 is monitored through the rotational speed
detecting means 59 such as an optical type encoder utilizing a photosensor. If the
rotational speed of the motor 13 is set to be equal to or lower than a predetermined
rotational speed Vref, reset means 73 resets the third timer 69 to bring the third
timer 69 into a counting completion state in order to stop the reduction in the rotational
speed of the motor 13. Consequently, the first rotation decrease command generating
means 71 stops the output of the rotation decrease command and the convection fan
control means 55 carries out control to reset the rotational speed of the second motor
13 to an original rotational speed. For the rotational speed detecting means 59, it
is possible to use a magnetic encoder having a combination of a hole element and a
magnet.
[0030] In the example of Fig. 3, the first rotation decrease command generating means 71
is realized by steps ST7 and ST13 and the reset means 73 is realized by steps ST10
and ST11.
[0031] When the first timer 63 completes the counting, fan stop command generating means
75 outputs a fan stop command for stopping the combustion fan 23 and the convection
fan 11 to the combustion fan control means 49 and the convection fan control means
55. It is also possible to propose that the fan stop command is outputted immediately
after the first timer 63 completes the counting. In this example, the fan stop command
is output with some delay. In the example of Fig. 3, the fan stop command generating
means 75 is realized by a step ST19.
[0032] Moreover, when the combustion flame in the pot 15 is reduced, the incomplete combustion
gas is easily generated. In this example, the size of a flame in the pot 15 is detected
by using the flame detecting means 39 for detecting a flame. If the flame has a smaller
size than a predetermined size, the rotational speed of the first motor 25 for driving
the combustion fan 23 is reduced. When the flame is reduced, the rotational speed
of the first motor 25 for driving the combustion fan is decreased. When the flame
is reduced, the amount of air required for the combustion of the unburnt gas is reduced.
Consequently, the rotational speed of the combustion fan 23 is reduced to decrease
the amount of air flow. Thus, complete combustion can be almost obtained. Second rotation
decrease command generating means 75 decides that the combustion flame becomes smaller
than a predetermined size by comparing an output I of the flame detecting means 31
with a reference value Iref. When the relationship of I < Iref is established, a rotation
decrease command for decreasing the rotation of the first motor 25 is output to the
combustion fan control means 49. Thus, the extinction can be carried out with a good
balance of an air/fuel ratio of the unburnt gas to the air, and the amount of generation
of the incomplete combustion gas can be decreased. In the case in which the rotational
speed of the combustion fan 23 is reduced to decrease the amount of air flow, it is
preferable that the amount of air flow of the combustion fan 23 should be maintained
to be small after the complete extinction. Thus, the pot 15 to be heated by the electric
heater 31 and the stabilizing member 16 in the pot 15 are cooled with difficulty depending
on the amount of air flow. Consequently, even if the fuel flows out of the fuel feeding
pipe 37 after the complete extinction, the oxidization of the fuel is instantaneously
accelerated so that the generation of the bad odor can be lessened. In the example
of Fig. 3, the second rotation decrease command generating means 75 is realized by
steps ST14, ST15 and ST16.
[0033] It is preferable that the first time period T1 of the first timer 63 should be set
to a time in which the electric heater 31 should be continuously conducted after the
flow of the fuel out of the fuel feeding pipe 37 is stopped, and furthermore, the
combustion fan 23 and the convection fan 11 continue the rotation for a while to cool
the inside of the frame member 1 down to a safe temperature.
1. A pot type oil burner comprising:
a frame body(1) having an air outlet(3) in a front part thereof;
a cylindrical bottomed pot (15) provided in the frame body and having a large number
of through holes (17) for air flow on a peripheral wall;
a combustion fan(23) including a first motor(25) as a driving source and serving to
supply combustion air into the pot(15) through the through holes(17);
combustion fan control means(49) for controlling rotation of the first motor (25),
thereby controlling an amount of air flow from the combustion fan(23);
fuel feeding means(35) for feeding a fuel into the pot through a fuel feeding pipe(37);
fuel feeding control means (51) for controlling a driving operation of the fuel feeding
means(35);
an electric heater(31) to be energized from a start of ignition to a start of combustion,
to heat the pot(15);
heater control means(53) for controlling the energization to the electric heater(31);
a convection fan(11) including a second motor(13) as a driving source, attached to
the frame body(1) to feed air from an outside of the frame body into the frame body
and to blow out the air into a room through the air outlet together with a combustion
gas discharged from the pot;
convection fan control means(55) for controlling rotation of the second motor (13)
, thereby controlling an amount of air flow from the convection fan(11); and
a control command generator(47) for giving a control command to the combustion fan
control means(49), the fuel feeding control means (51), the heater control means (53)
and the convection fan control means(55), respectively, characterized in that
the control command generator(47) outputs a fuel feeding stop command for stopping
the driving operation of the fuel feeding means(35) to the fuel feeding control means(51)
and outputs a heater energization command to the heater control means(53), in order
to energize the heater(31) for a predetermined first time period which is longer than
a time period required for completely ending combustion, when an extinction command
is input,
outputs a rotation decrease command for decreasing the rotation of the second motor(13)
to the convection fan control means (55) so as to decrease the amount of air from
the convection fan(11), after a predetermined second time period equivalent to a time
period to be considered to start incomplete combustion after the extinction command
is input passes, while a predetermined third time period to be considered to be required
for reducing a combustion flame or extinguishing the flame in the pot then passes,
and
outputs a fan stop command for stopping the combustion fan (23) and the convection
fan (11) to the combustion fan control means(49) and the convection fan control means(55)
after the first time period is ended.
2. The pot type oil burner according to claim 1, wherein the control command generator(47)
includes:
fuel feeding stop command generating means(61) for outputting a fuel feeding stop
command to stop the driving operation of the fuel feeding means(35) to the fuel feeding
control means(51) when an extinction command is input;
a first timer(63) for starting counting when inputting the extinction command, and
for counting a predetermined first time period which is longer than a time period
required for completely ending combustion;
heater energization command generating means(65) for energizing the heater(31), thereby
outputting, to the heater control means(53), a heater energization command for heating
the pot(15) until the first timer(63) completes the counting;
a second timer(67) for counting a second time period at the end of which period the
combustion flame in the pot is so small that incomplete combustion gas is generated,
after inputting the extinction command;
a third timer(69) for counting a third time period at the end of which period the
combustion flame is considerably reduced or completely extinguished in the pot after
the second timer (67) completes the counting;
rotation decrease command generating means(71) for outputting, to the convection fan
control means (55), a rotation decrease command to decrease the rotation of the second
motor(13) so as to decrease an amount of air flow of the convection fan(11) while
the third timer(69) carries out the counting; and
fan stop command generating means(75) for outputting a fan stop command to stop the
combustion fan(23) and the convection fan(11) to the combustion fan control means
(49) and the convection fan control means(55) after the first timer(63) completes
the counting.
3. The pot type oil burner according to claim 2, wherein the rotation decrease command
generating means (71) outputs the rotation decrease command to decrease the rotational
speed of the second motor(13) such that the air blown out of the air outlet(3) is
raised upward as soon as possible.
4. The pot type oil burner according to claim 2, further comprising rotation increase
command generating means (59,71,73) for outputting, to the convection fan control
means(55), a rotation increase command to increase the rotational speed of the second
motor(13) after the third time period passes.
5. The pot type oil burner according to claim 2, wherein the fan stop command generating
means (75) outputs the fan stop command to stop the combustion fan(23) and the convection
fan(11) after the heater de-energization command is output.
6. The pot type oil burner according to claim 1, further comprising forced braking means(57)
for forcedly applying braking to the second motor(13),
the convection fan control means(55) serving to operate the forced braking means(57),
thereby rapidly decreasing the rotational speed of the second motor(13) of the convection
fan(11) when inputting the rotation decrease command.
7. The pot type oil burner according to claim 6, wherein the convection fan control means(55)
is constituted so as to gradually decrease the rotational speed of the second motor
(13) after operating the forced braking means(57),
the control command generator (47) further includes reset means(73) for resetting
the third timer(65) and rotational speed detecting means(59) for detecting a rotational
speed of the second motor(13), and
the reset means(73) is operated to reset the third timer(69), thereby bringing the
third timer into a counting completion state when the rotational speed detected by
the rotational speed detecting means (59) is equal to or lower than a predetermined
rotational speed.
8. The pot type oil burner according to claim 6, wherein the second motor(13) is an AC
inductor motor and the forced braking means(57) causes a DC current to flow to an
exciting winding of the AC induction motor.
9. The pot type oil burner according to claim 1, further comprising flame detecting means(39)
for detecting a size of a combustion flame in the pot,
the control command generator(47) further including another rotation decrease command
generating means(75) for outputting, to the combustion fan control means(49), another
rotation decrease command for decreasing the rotational speed of the first motor (25)
to decrease an amount of air flow of the combustion fan(23) when the flame detecting
means (39) detects that the combustion flame is smaller than a predetermined size.