Combustion heater

A combustion heater includes a burner cylinder defining therein a combustion chamber. The burner cylinder has a peripheral wall thereof having a number of air inlet holes formed therein, one bottomed end thereof having an end wall formed with at least one opening, and another open end thereof having a peripheral edge. A wick is exposed to the combustion chamber for impregnating with liquid fuel. The peripheral edge of the open end of the burner cylinder is disposed in close contact with the wick. The end wall of the bottomed end of same is opposed to the wick. The burner cylinder has a radially extending reflecting portion formed by the end wall of the bottomed end thereof.

BACKGROUND OF THE INVENTION 
This invention relates to a combustion heater for use in vehicles with a 
hot storage for preserving foods, etc. in a hot state, or the like, and 
more particularly to a combustion heater of this kind which is adapted to 
vaporize liquid fuel supplied to the wick, and ignite and burn a mixture 
of combustion air and vaporized liquid fuel within a combustion chamber. 
Conventionally, a combustion heater of this kind has been proposed e.g. by 
U.S. Ser. No. 07/479,087 assigned to the same assignee as the present 
application, now abandoned. The proposed combustion heater comprises, as 
shown in FIG. 1, a burner cylinder 104 having a peripheral wall thereof 
formed with a number of air inlet holes 104b to define a combustion 
chamber 104a therein, a wick 106 for impregnating with liquid fuel, a wick 
holder 107 holding the wick 106 exposed to the combustion chamber 104a , a 
shaft 122 secured at one end thereof to the wick holder 107 in a manner 
projecting into the combustion chamber 104a, and a flange member 121 
radially extending from the other end of the shaft 122 in a manner facing 
the wick 106. 
According to the proposed combustion heater, the flange member 121 
functions as follows: When combustion air radially flows straight toward 
the axis of the burner cylinder 104 through the air inlet holes 104b, the 
flowing combustion air is apt to concentrate in the diametrical centeral 
zone of the combustion chamber 104a so that a flame rich with air occurs 
in the same zone, forming excess air in the diametrical central zone as 
well as an unburnt gas in a peripheral zone in the burner cylinder 104. 
However, the excess air is guided together with the flame by the flange 
member 121 radially outwardly toward the peripheral zone, wherefrom it 
flows through a gap provided between an outer peripheral surface of the 
flange member 121 and an inner peripheral surface of the burner cylinder 
104 while being mixed with the unburnt gas. On the other hand, when 
combustion air flows swirlingly into the combustion chamber 104a, the 
vaporized fuel in the peripheral zone in the burner cylinder 104 is pushed 
by the swirling combustion air to the diametrical central zone so that a 
flame rich with fuel occurs in the diametrical central zone, forming an 
unburnt gas in the diametrical central zone as well as excess air in the 
peripheral zone in the burner cylinder 104. However, the unburnt gas is 
guided together with the flame by the flange member 121 radially outwardly 
toward the peripheral zone, wherefrom it flows through the gap between the 
outer peripheral surface of the flange member 121 and the inner peripheral 
surface of the burner cylinder 104 while being mixed with the excess air. 
The flange member 121 also serves to transfer heat to the wick 106 by 
conduction through the shaft 122, as well as to the opposed end face of 
the wick 106 by radiation, thereby enhancing the degree of fuel 
vaporization by the wick 106. 
However, the proposed combustion heater had the disadvantage that the wick 
106 has a limited effective surface area from which liquid fuel is 
vaporized because the shaft 122 extends through the wick 106, thereby 
resulting in reduced combustion efficiency. 
Further, the wick 106 is held between the wick holder 107 and the burner 
cylinder 104 with a peripheral edge thereof abutting against an opposed 
open end edge of the burner cylinder 106 having a small surface area. 
Therefore, it is difficult to stably hold the wick 106 in place. 
Another disadvantage with the proposed combustion heater is that the flange 
member 121 requires time-consuming machining to manufacture, causing an 
increased manufacturing cost. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide a combustion heater which has 
an enhanced degree of fuel vaporization by the wick. 
It is a further object of the invention to assure positive holding of the 
wick in place. 
It is another object of the invention to facilitate the manufacture of the 
combustion heater and hence reduce the manufacturing cost. 
To attain the above objects, the present invention provides a combustion 
heater including a burner cylinder defining therein a combustion chamber, 
the burner cylinder having a peripheral wall thereof having a number of 
air inlet holes formed therein, one bottomed end thereof having an end 
wall formed with at least one opening, and another open end thereof having 
a peripheral edge, a wick exposed to the combustion chamber for being 
impregnated with liquid fuel, the peripheral edge of the open end of the 
burner cylinder being disposed in close contact with the wick, the end 
wall of the bottomed end being opposed to the wick, and a wick holding the 
wick in place. 
The combustion heater according to the present invention is characterized 
by the improvement wherein the burhner cylinder has a radially extending 
reflecting portion formed by the end wall of the bottomed end thereof. 
Preferably, the reflecting portion is formed at a location radially inward 
of the at least one opening. 
More preferably, the peripheral edge of the open end is radially inwardly 
curved. The above and other objects, features, and advantages of the 
invention will be more apparent from the ensuing detailed description 
taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION 
The invention will now be described in detail with reference to the 
drawings showing embodiments thereof. 
FIG. 2 shows a combustion heater according to an embodiment of the 
invention, which is adapted to heat a space within a hot storage installed 
on a vehicle or the like. The combustion heater is essentially composed to 
a burner 1, and a heat exchanger 2. 
The burner 1 comprises a burner cylinder 4 defining therein a combustion 
chamber 3, a heat insulating covering 5 fitted over an outer peripheral 
surface of the burner cylinder 4, a wick 6 in the form of a disk formed of 
ceramic fiber and exposed to the combustion chamber 3, a wick holder 7 
holding the wick 6 in place, and a burner casing 8. 
As shown in FIGS. 3 and 4, the burner cylinder 4 is generally in the form 
of a bottomed cylinder, and formed, e.g. of stainless steel, which has an 
open end 4a with a peripheral edge 4a' thereof radially inwardly curved 
and an opposite or bottomed end 4d having an end wall 4d' formed with four 
openings 4c circumferentially arranged at equal intervals, through which a 
combustion gas generated in the burner cylinder 4 is discharged into the 
interior of a combustion tube 14, hereinafter referred to. A radially 
extending reflecting wall portion 4e is formed by a diametrical central 
portion of the end wall 4d', i.e. at a location radially inward of the 
openings 4c. The inwardly curved open end edge 4a' is disposed in close 
contact with an opposed end face of the wick 6. 
The burner cylinder 4 has a peripheral wall thereof formed therein with a 
number of air inlet holes 4b, whereas the heat insulating covering 5 also 
has a peripheral wall thereof formed therein with a number of air inlet 
holes 5a at locations corresponding respectively to the air inlet holes 4b 
of the burner cylinder 4. An air passage 9 is defined between an outer 
peripheral surface of the heat insulating covering 5 and an inner 
peripheral surface of the burner casing 8. Combustion air supplied by a 
blower, not shown, travels in the air passage 9, and then through the air 
inlet holes 4b, 5a into the combustion chamber 3. 
The wick holder 7 is formed therein with a fuel supply passage 11 having 
one end thereof connected to a fuel supply pipe, not shown, extending from 
a fuel pump, not shown, and the other end thereof opening in an opposed 
end face of the wick 6, whereby liquid fuel is supplied from the fuel pump 
to the wick 6. 
A glow plug 12 is removably fitted through a peripheral wall 8c of the 
burner casing 8 with its ignition tip 12a projected into the combustion 
chamber 3. Similarly, an ignition sensor 13 is also removably fitted 
through the peripheral wall 8c with its flame sensing tip 13a projected 
into the combustion chamber 3. 
In the heat exchanger 2, the combustion tube 14 is disposed such that 
combustion gas with a flame having a high temperature generated in the 
combustion chamber 3 is introduced into the interior thereof through the 
openings 4c of the burner cylinder 4. The combustion tube 14 is formed 
integrally with the heat insulating covering 5, and fixed by bolts 10 to 
mounting protuberances 8a formed on an inner peripheral surface of the 
burner casing 8 through a mounting member 21 secured to an outer 
peripheral surface of the burner cylinder 14. 
An inner cylinder 8d is disposed around the combustion tube 14, which 
extends integrally from the burner casing 8 to a location somewhat axially 
outward of the other end 14b of the combustion tube 14 to define 
therebetween a combustion gas passage A. Further, an exhaust port 8e is 
formed in a lower portion of the burner casing 8 close to the heat 
exchanger 2, through which combustion gas having passed the combustion gas 
passage A is discharged to the outside. Combustion gas introduced into the 
combustion tube 14 travels through the other open end 14b and the 
combustion gas passage A, and exits from the exhaust port 8e to the 
outside. 
A heat exchanger casing or outer cylinder 15 is disposed around the inner 
cylinder 8d to define a heating air passage B therebetween. The heat 
exchanger casing 15 has one end 15b thereof fixed to mounting portions 8f 
of the burner casing 8 by bolts 16 and the other end 15c thereof having an 
outer peripheral surface to which an end portion 17a of a duct 17 is 
secured by bolts 18. The heat exchanger casing 15 has a heating air inlet 
port 15a formed in an upper end portion thereof close to the burner 1, 
through which heating air (cold air) from a hot storage, not shown, is 
supplied into the heating air passage B of the heat exchanger 2. 
The inner cylinder 8d has one end thereof remote from the burner 1, which 
is closed by a closing member 22 having a combustion gas-guide surface 
22c, so that the duct 17 cooperates with the closing member 22 to form a 
passage C communicating with the heating air passage B, and an outlet 17b 
through which heating air (warm air), which has been heated while passing 
through the heating air passage B, is discharged. The combustion gas-guide 
surface 22c also serves to deflect combustion gas glowing through the 
outer end 14b of the combustion tube 14 into the combustion gas passage A. 
A plurality of fins 19 are formed on an inner peripheral surface of the 
inner cylinder 8d in a manner axially extending and arranged at 
circumferentially equal intervals so that the heat of combustion gas 
travelling in the combustion gas passage A can be efficiently transferred 
to the inner cylinder 8d. On the other hand, a plurality of fins 20 are 
formed on an outer peripheral surface of the inner cylinder 8d in a manner 
axially extending and arranged at circumferentially equal intervals so 
that heating air introduced from the heating air inlet hole 15a is 
efficiently heated by the heat of the inner cylinder 8d while travelling 
in the heating air passage B. 
The operation of the combustion heater constructed as above will be 
explained hereinbelow: 
When an operating switch, not shown, is turned on to start heating of the 
space within the hot storage, combustion air is first supplied by the 
blower, not shown, into the combustion chamber 3 through the air passage 9 
and the air inlet holes 5b, 4b of the heat insulating covering 5 and the 
burner cylinder 4. On the other hand, liquid fuel is supplied from the 
fuel pump through the fuel passage 11 to the wick 6, to permeate same. 
Then, the glow plug 12 is energized to heat the igniter 12a, which 
vaporizes liquid fuel in the wick 6 and lights up the resulting mixture of 
vaporized fuel and combustion air to generate a flame within the 
combustion chamber 3. 
As a result, the reflecting portion 4e is heated by the flame to a high 
temperature, so that the heat of the reflecting portion 4e is transferred 
by thermal radiation to the opposed end face of the wick 6, as shown by 
the arrows D in FIG. 2, thereby enhancing the degree of fuel vaporization 
by the wick 6. 
When combustion air flows straight toward the axis of the burner cylinder 
4, as shown by the arrows in FIG. 5 (a), the flowing combustion air is apt 
to concentrate in the diametrical central zone of the burner cylinder 4 so 
that a flame rich with air occurs in the same zone, whereby part of the 
air in the zone does not take part in the combustion, forming excess air 
there. On the other hand, a flame rich with fuel occurs in a peripheral 
zone in the burner cylinder 4, forming an unburnt gas there. However, the 
excess air in the diametrically central zone is guided radially outward by 
the reflecting portion 4e to the peripheral zone in the burner cylinder 4 
where it is mixed with the unburnt gas and flows together therewith 
through the openings 4c while being thoroughly mixed with each other, 
thereby improving the combustion efficiency within the combustion chamber 
3. 
On the other hand, when combustion air flows swirlingly into the combustion 
chamber 3, as shown by the arrows in FIG. 5 (b), the vaporoized fuel in 
the peripheral zone in the burner cylinder 4 is pushed by the swirling 
combustion air to the diametrically central zone in the burner cylinder 4 
so that a flame rich with fuel occurs in the latter zone, whereby part of 
the fuel in the zone does not take part in the combustion, forming an 
unburnt gas there. On the other hand, a flame rich with air occurs in the 
peripheral zone close to the inner peripheral surface of the burner 
cylinder 4, forming excess air there. However, the unburnt gas in the 
diametrically central zone is guided radially outward by the reflecting 
portion 4e to the peripheral zone where it is mixed with the excess air 
and flows together therewith through the outlet holes 4c while being 
thoroughly mixed with each other, thereby improving the combustion 
efficiency within the combustion chamber 3. 
The combustion gas in the combustion chamber 3. is smoothly introduced 
together with a flame through the outlet holes 4c into the combustion tube 
14 of the heat exchanger 2, and then travels through the combustion gas 
passage A while heating the inner cylinder 8d, and exits through the 
exhaust port 8e to the outside. 
On the other hand, heating air from the hot storage is supplied through the 
air inlet hole 15a, and travels through the heating air passage B while 
being heated by the hot inner cylinder 8d. The heating air thus heated 
passes through the passage C within the duct 17 and is discharged through 
the heating air outlet 17b into the hot storage, to heat the space within 
the hot storage. 
As described above, according to the invention, the radially inwardly 
curved opening end edge 4a' of the burner cylinder 4 serves to increase 
the effective contact area with the opposed end face of the wick 6, 
thereby positively holding the wick 6 in place in cooperation with the 
wick holder 7. Further, since the reflecting portion 4e is formed on the 
end wall 4d' of the burner cylinder 4, instead of providing a flange 
member secured on one end of a shaft secured to the wick holder 7, there 
is no necessity of forming a shaft-fitting through hole through the wick 6 
along its axis, thereby increasing the effective fuel vaporizing area or 
degree of fuel dispersion into the combustion chamber 3 and hence the fuel 
combustion efficiency. Further, no machining is required for forming the 
reflecting portion 4e of the burner cylinder 4, which greatly simplifies 
or facilitates the manufacture of the combustion heater with reduced 
component parts, thereby reducing the total manufacturing cost. 
In the above described embodiment, four openings 4c are formed in the 
bottomed wall 4d of the burner cylinder 4. Alternatively, three openings 
4c may be formed, as shown in FIG. 6, providing substantially the same 
results as in the above described embodiment.