Combustion heater

In a combustion heater, a fuel feed unit supplies a fuel uniformly into a burner so as to prevent incomplete combustion in the burner. When a vaporization member is provided in the burner, the fuel feed unit supplies the fuel uniformly all over the surface of the vaporization member so that the incomplete combustion in the burner is also prevented. In addition or alternatively, the fuel feed unit includes a fuel feed pipe and a valve unit which is provided at a tip portion of the fuel feed pipe, so as to prevent emissions of an unburned fuel. In addition or alternatively, a temperature of the fuel supplied to the burner is monitored, and an operation of the fuel feed unit or an air feed unit for supplying combustion air to the burner is controlled based on the monitored fuel temperature so as to provide a desirable air-fuel mixture for preventing incomplete combustion in the burner. An amount of the fuel supplied to the burner or an oxygen concentration in an exhaust gas after combustion in the burner may be monitored instead of the fuel temperature.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a combustion heater, and more 
specifically, to the combustion heater which aims to prevent incomplete 
combustion and so forth for improving emissions in the exhaust gas, such 
as, HC emissions and evaporative emissions. 
2. Description of the Prior Art 
As is known in the art, the combustion heater is arranged to burn up a 
portion of an engine fuel with a burner for heating water to be conducted 
to a radiator in a vehicular compartment. The combustion heater is used as 
an auxiliary vehicle heater before a temperature of engine cooling water 
increases to a given high value. 
In the burner of the combustion heater, the supplied fuel is vaporized and 
mixed with combustion air, and this mixture is ignited and burned using a 
heater or a glow plug. 
FIG. 25 shows one example of the conventional combustion heaters. In the 
figure, a housing 1 has a double-wall structure at its half to form a 
fluid passage 13 for water to be conducted to a radiator (not shown). A 
burner 2 is arranged in the housing 1. The burner 2 has a burner tube 
which is provided with a vaporization plate 4 at one axial end thereof. 
The vaporization plate 4 is prepared by forming ceramic fibers into a 
plate shape. An open end of a fuel feed pipe 73 is in abutment with the 
vaporization plate 4. Fuel is fed to the fuel feed pipe 73 from a pump 72 
in a fuel tank 71 via a fuel cutoff valve 76. The fuel then reaches the 
vaporization plate 4 where the fuel is dispersed over the entirety of the 
vaporization plate 4 due to the capillary action. The vaporization plate 4 
is heated by a glow plug 9 provided adjacent thereto. Accordingly, the 
fuel is vaporized from the vaporization plate 4 and then mixed with 
combustion air introduced into the burner tube via air introducing holes 
211 so as to be ignited to burn. 
The combustion heater using such a vaporization plate is disclosed in, such 
as, Japanese First (unexamined) Patent Publication No. 1-262214, Japanese 
First (unexamined) Patent Publication No. 4-73503, Japanese First 
(unexamined) Patent Publication No. 4-214105 equivalent to U.S. Pat. No. 
5,088,918, or U.S. Pat. No. 4,538,985. 
However, in the foregoing conventional combustion heaters, a fuel density 
is the highest at the contacting portion between the fuel feed pipe 73 and 
the vaporization plate 4 and is lowered toward peripheral areas thereof. 
Accordingly, a distribution of the fuel dispersed over the vaporization 
plate 4 does not become uniform. Further, the fuel dispersed in such a 
non-uniform manner is ignited by the glow plug 9 which has a relatively 
small heating range. Accordingly, at the start of combustion, incomplete 
combustion is caused at a portion where the fuel density is high, so as to 
increase an amount of HC emissions. 
Further, at the time of extinction of flame when the fuel supply is 
stopped, the fuel remaining in a fuel passage from the fuel cutoff valve 
76 to the open end of the fuel feed pipe 73 is gradually dispersed to the 
vaporization plate 4 and then vaporized. As a result, the unburned fuel is 
exhausted to cause a problem of the evaporative emissions. 
Further, the fuel fed to the fuel feed pipe 73 is gradually increased in 
temperature due to the ongoing operation of the pump 72 and thus reduced 
in viscosity. This lowers flow resistance of the fuel passage against the 
fuel to increase a supply amount of the fuel to a value greater than a 
given initial value. As a result, the mixture of the fuel and the 
combustion air becomes richer to deteriorate the emissions in the exhaust 
gas. 
For further prior art information, Japanese First (unexamined) Patent 
Publication No. 60-29505 shows a catalytic heater in which fuel is 
atomized using an ultrasonic vibrator, and Japanese First (unexamined) 
Patent Publication No. 2-82007 shows a vaporization oil burner in which a 
temperature sensor is provided in a fuel vaporizer so as to prevent 
generation of odor by closing a fuel nozzle until a temperature in the 
fuel vaporizer is lowered to a given value. 
SUMMARY OF THE INVENTION 
In view of the foregoing, it is an object of the present invention to 
provide an improved combustion heater which aims to solve one or more of 
the aforementioned drawbacks of the conventional combustion heaters. 
According to one aspect of the present invention, a combustion heater 
having a burner in a housing provided with a fluid passage for heating a 
fluid introduced in the fluid passage comprises a vaporization member 
provided in the burner for vaporizing a fuel supplied to the burner; fuel 
feed means for supplying the fuel uniformly essentially all over the 
surface of the vaporization member; air feed means for supplying 
combustion air to the burner depending on an amount of the fuel supplied 
by the fuel feed means; and ignition means for igniting the supplied fuel 
in the burner. 
According to another aspect of the present invention, a combustion heater 
having a burner in a housing provided with a fluid passage for heating a 
fluid introduced in the fluid passage comprises a fuel feed pipe for 
supplying a fuel to the burner; air feed means for supplying combustion 
air to the burner depending on a supply amount of the fuel; ignition means 
for igniting the supplied fuel in the burner; and a valve unit provided at 
a tip portion of the fuel feed pipe for opening/closing the fuel feed 
pipe. 
According to another aspect of the present invention, a combustion heater 
having a burner in a housing provided with a fluid passage for heating a 
fluid introduced in the fluid passage comprises temperature detecting 
means for detecting a temperature of a fuel supplied to the burner; fuel 
adjusting means for adjusting an amount of the fuel supplied to the 
burner; air adjusting means for adjusting an amount of air supplied to the 
burner; and adjusting amount setting means for variably setting an 
adjusting amount of at least one of the fuel adjusting means and the air 
adjusting means based on the detected fuel temperature. 
According to another aspect of the present invention, a combustion heater 
having a burner in a housing provided with a fluid passage for heating a 
fluid introduced in the fluid passage comprises fuel supply amount 
detecting means for detecting an amount of a fuel supplied to the burner; 
air adjusting means for adjusting an amount of air supplied to the burner; 
and adjusting amount setting means for variably setting an adjusting 
amount of the air adjusting means based on the detected fuel supply 
amount. 
According to another aspect of the present invention, a combustion heater 
having a burner in a housing provided with a fluid passage for heating a 
fluid introduced in the fluid passage comprises oxygen concentration 
detecting means for detecting an oxygen concentration in an exhaust gas 
after combustion in the burner; fuel adjusting means for adjusting an 
amount of a fuel supplied to the burner; air adjusting means for adjusting 
an amount of air supplied to the burner; and adjusting amount setting 
means for variably setting an adjusting amount of at least one of the fuel 
adjusting means and the air adjusting means based on the detected oxygen 
concentration.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Now, preferred embodiments of the present invention will be described 
hereinbelow with reference to the accompanying drawings. 
FIG. 1 is a sectional view showing a combustion heater according to a first 
preferred embodiment of the present invention. In FIG. 1, the same or like 
elements are designated by the same reference numerals as those in FIG. 
25. 
In FIG. 1, a housing 1 of the combustion heater includes a pair of housing 
halves 11 and 12 which are fixed to each other at their open ends with a 
partition plate 14 interposed therebetween. The housing half 11 has an 
upper wall formed with an air inlet 15 and a lower wall formed with an 
exhaust-gas outlet 16. The housing half 12 has a double-wall structure to 
form a fluid passage 13. The fluid passage 13 communicates with a water 
inlet 17 formed at a lower wall of the housing half 12 and with a water 
outlet 18 formed at an upper wall of the housing half 12 for conducting 
water, as a heat transfer medium, to a radiator (not shown) provided in a 
vehicular compartment. 
In the housing 1, a burner 2 is fixedly disposed at the center thereof. The 
burner 2 has a burner tube which is composed of a mixture tube 21 and a 
combustion tube 22 projecting from opposite sides of the partition plate 
14, respectively. The combustion tube 22 is a cylindrical body having a 
relatively large diameter as compared with the mixture tube 21 which is 
also a cylindrical body. The combustion tube 22 is located in an interior 
space of the housing half 12 which communicates with the exhaust-gas 
outlet 16 via a through hole 142 formed at the partition plate 14. The 
mixture tube 21 is located in an interior space of the housing half 11 
which communicates with the air inlet 15. The mixture tube 21 is formed 
with a small hole 212 at its axial end remote from the partition plate 14. 
The interior of the mixture tube 21 communicates with the interior of the 
combustion tube 22 via an opening 141 formed at the center of the 
partition plate 14. 
A fuel feed pipe 73 is arranged to penetrate an axial end wall of the 
housing half 11 remote from the partition plate 14. A tip of the fuel feed 
pipe 73 passes through the small hole 212 of the mixture tube 21 and is 
exposed to the interior of the mixture tube 21. A fuel cutoff valve 31 is 
provided at a portion 731 of the fuel feed pipe 73 close to the tip 
thereof and between the foregoing axial end walls of the housing half 11 
and the mixture tube 21 for adjusting a supply amount of the fuel by 
opening/closing the fuel feed pipe 73. The fuel cutoff valve 31 is in the 
form of an electromagnetic valve or a check valve. The fuel feed pipe 73 
extends to reach a pump 72 provided in a fuel tank 71. Further, a number 
of air introducing holes 211 are formed at the circumferential wall of the 
mixture tube 21. 
A glow plug 9 extends through the circumferential wall of the mixture tube 
21 to reach the neighborhood of the tip of the fuel feed pipe 73. The glow 
plug 9 is of the known type which has been used in the automotive engine. 
An electronic control unit (ECU) 6 is provided for opening/closing the fuel 
cutoff valve 31 and for energizing the glow plug 9. The ECU 6 further 
controls an operation of an air pump 82 provided at an air feed pipe 81 
extending to reach the air inlet 15. 
An operation of the combustion heater having the foregoing structure will 
be described hereinbelow. 
At the time of ignition, the glow plug 9 is energized so as to increase a 
surface temperature thereof to an ignitable temperature of the fuel. 
Subsequently, the fuel cutoff valve 31 is opened to feed the fuel into the 
mixture tube 21, and the air pump 82 is driven to introduce combustion air 
into the mixture tube 21 via the air introducing holes 211. As a result, 
the fuel is vaporized near the surface of the glow plug 9 and then mixed 
with the combustion air so as to start combustion. Flame is ejected 
through an opening 222 of the combustion tube 22. The water flowing in the 
fluid passage 13 is heated by the flame and fed to the radiator so as to 
perform heating in the vehicular compartment. Burned gas as a result of 
the combustion is discharged through the exhaust-gas outlet 16. 
On the other hand, at the time of extinction of flame, the fuel cutoff 
valve 31 is closed. However, since the fuel cutoff valve 31 is provided 
close to the tip of the fuel feed pipe 73 in this preferred embodiment, 
the evaporative emissions, that is, the emissions of the unburned fuel 
caused by vaporization of the fuel remaining in the fuel feed pipe 73, are 
effectively prevented as opposed to the aforementioned prior art. 
Now, a second preferred embodiment of the present invention will be 
described hereinbelow. 
FIG. 2 is a sectional view showing a combustion heater according to the 
second preferred embodiment, wherein the same or like elements are 
designated by the same reference numerals as those in FIG. 1. 
As appreciated from FIG. 2, the fuel supply structure of the foregoing 
first preferred embodiment can also be applied to the combustion heater of 
a type shown in FIG. 2. Specifically, in the figure, a burner 2 is 
surrounded by a guide tube 24 having a larger diameter. A combustion tube 
22 is closed at its axial end remote from a fuel feed pipe 73. A number of 
flame ejecting holes 223 are formed at a circumferential wall of the 
combustion tube 22. An open end 23 of the combustion tube 22 close to the 
fuel feed pipe 73 is fixed to an axial end wall of a housing half 11. In 
the housing half 11 is formed an air flow passage 19 which extends from an 
air inlet 15 to reach the open end 23 of the combustion tube 22. 
Flame is ejected outward through, the flame ejecting holes 223 and then 
guided by the guide tube 24 toward a wall of a housing 1 where a fluid 
passage 13 is provided. 
As appreciated from the foregoing description, the foregoing advantage 
achieved in the first preferred embodiment can also be achieved in this 
preferred embodiment. 
Now, a third preferred embodiment of the present invention will be 
described hereinbelow. 
FIG. 3 is a sectional view showing a combustion heater according to the 
third preferred embodiment, wherein the same or like elements are 
designated by the same reference numerals as those in FIG. 1. 
As shown in FIG. 3, in this preferred embodiment, a known electromagnetic 
fuel injection valve 33 installed in the automotive engine is used instead 
of the fuel cutoff valve 31 of the first preferred embodiment shown in 
FIG. 1. Specifically, the fuel injection valve 33 is arranged to penetrate 
an axial end wall of a housing half 11 remote from a partition plate 14. 
Further, a tip of the fuel injection valve 33 is mounted in a small hole 
212 of a mixture tube 21 and exposed to the interior of the mixture tube 
21. A fuel inject/on pressure of the fuel injection valve 33 is about 3 
kg/cm.sup.2. 
The fuel injection valve 33 is connected with a tip of a fuel feed pipe 73 
extending from a pump 72 provided in a fuel tank 71 so as to be supplied 
with the fuel therefrom. A return pipe 75 provided with a relief valve 74 
is connected to the fuel feed pipe 73 at an appropriate portion thereof 
from the pump 72 to the fuel injection valve 33 for returning an excess 
fuel to the fuel tank 71. 
In the combustion heater having the foregoing structure, the fuel injection 
valve 33 works to spray the fuel uniformly into the mixture tube 21. 
Accordingly, at the time of ignition, HC emissions are effectively 
suppressed by preventing the incomplete combustion which would be 
otherwise caused at the portion where the fuel density is high as in the 
aforementioned prior art. 
The fuel injection valve 33 further works to adjust a supply amount of the 
fuel by opening/closing the fuel feed pipe 73 at the tip of the fuel feed 
pipe 73. Accordingly, at the time of extinction of flame, the problem of 
emissions of the unburned fuel remaining in the fuel feed pipe 73 is also 
solved. 
As appreciated, since the fuel injection valve 33 can cut the fuel supply 
by closing the fuel feed pipe 73, it is not necessary to provide the fuel 
cutoff valve separately. 
Now, a fourth preferred embodiment of the present invention will be 
described hereinbelow. 
FIG. 4 is a sectional view showing a combustion heater according to the 
fourth preferred embodiment, wherein the same or like elements are 
designated by the same reference numerals as those in FIG. 2. 
As shown in FIG. 4, in this preferred embodiment, a fuel injection valve 33 
which is the same as that used in the third preferred embodiment is used 
instead of the fuel cutoff valve 31 of the second preferred embodiment 
shown in FIG. 2. The fuel injection valve 33 is provided at a tip of a 
fuel feed pipe 73 as in the third preferred embodiment. 
As appreciated, the foregoing advantage achieved in the third preferred 
embodiment can also be achieved in this preferred embodiment. 
Now, a fifth preferred embodiment of the present invention will be 
described hereinbelow. 
FIG. 5 is a sectional view showing a combustion heater according to the 
fifth preferred embodiment, wherein the same or like elements are 
designated by the same reference numerals as those in FIGS. 1 and 15. 
In FIG. 5, a spray nozzle 32 is arranged to penetrate an axial end wall of 
a housing half 11. The spray nozzle 32 is connected with a tip of a fuel 
feed pipe 73 extending from a pump 72 provided in a fuel tank 71. A tip of 
the spray nozzle 32 is located in a small hole 212 of a mixture tube 21. 
The spray nozzle 32 is capable of spraying the fuel in a wide range. 
In the mixture tube 21, a vaporization plate 4 in the form of a porous disk 
body made of, such as, foam metal is disposed forward of the spray nozzle 
32. In this preferred embodiment, the foam metal is nickel foam metal 
formed of pure nickel, nickel chrome or the like. The vaporization plate 4 
is arranged to confront the tip of the spray nozzle 32 and cross laterally 
the inside of the mixture tube 21. 
In the combustion heater having the foregoing structure, at the time of 
ignition, the fuel is sprayed all over the surface of the vaporization 
plate 4 from the spray nozzle 32 and then vaporized. The vaporized fuel is 
mixed with the combustion air in the neighborhood of a surface of a glow 
plug 9 and ignited to burn. Since the fuel is supplied uniformly all over 
the surface of the vaporization plate 4 by the spray nozzle 32, a 
distribution of the fuel on the vaporization plate 4 becomes uniform. This 
effectively solves the problem of HC emissions caused by the incomplete 
combustion at the portion of the vaporization plate 4 where the fuel 
density is high. 
Now, a sixth preferred embodiment of the present invention will be 
described hereinbelow. 
As shown in FIGS. 6 and 7, in this preferred embodiment, a heater element 
51 is arranged on a side, remote from the spray nozzle 32, of the 
vaporization plate 4 in the foregoing fifth preferred embodiment. The 
heater element 51 is in the form of a sheath heater where a heater 
conductor is embedded at the center of a linear insulating member having a 
circular cross section. The heater element 51 is fixed to the foregoing 
side of the vaporization plate 4 in a curved or bent shape for increasing 
a contact area between the heater element 51 and the vaporization plate 4. 
The other structure is the same as that in the fifth preferred embodiment. 
In the combustion heater having the foregoing structure, the fuel is 
supplied uniformly all over the surface of the vaporization plate 4 by the 
spray nozzle 32, and further is efficiently vaporized by the heater 
element 51 provided on the foregoing side of the vaporization plate 4. 
Accordingly, HC emissions due to the incomplete combustion are prevented 
more effectively. 
In the sixth preferred embodiment, the heater element 51 may also be used 
for an ignition purpose and the glow plug 9 may be omitted. 
Now, a seventh preferred embodiment of the present invention will be 
described hereinbelow. 
As shown in FIGS. 8 and 9, in this preferred embodiment, a pair of glow 
plugs 52 are used instead of the sheath heater 51 in the foregoing sixth 
preferred embodiment. The number of the glow plugs 52 may be more than 
two. The other structure is the same as that in the sixth preferred 
embodiment. 
In the seventh preferred embodiment, the advantage is achieved similar to 
that in the foregoing sixth preferred embodiment. 
Now, an eighth preferred embodiment of the present invention will be 
described hereinbelow. 
FIG. 10 is a sectional view showing a combustion heater according to the 
eighth preferred embodiment, wherein the same or like elements are 
designated by the same reference numerals as those in FIGS. 3 and 5. 
As shown in FIG. 10, in this preferred embodiment, a fuel injection valve 
33 is used instead of the spray nozzle 32 of the fifth preferred 
embodiment shown in FIG. 5. The fuel injection valve 33 is arranged to 
confront a vaporization plate 4. 
In this preferred embodiment, the foregoing advantage achieved in the fifth 
preferred embodiment can also be achieved. 
Specifically, at the time of ignition, the fuel is injected all over the 
surface of the vaporization plate 4 from the fuel injection valve 33 and 
then vaporized. The vaporized fuel is mixed with the combustion air in the 
neighborhood of a heated surface of a glow plug 9 and starts to burn. 
Since the fuel is supplied uniformly all over the surface of the 
vaporization plate 4 by the fuel injection valve 33, a distribution of the 
fuel on the vaporization plate 4 becomes uniform. This effectively solves 
the problem of HC emissions caused by the incomplete combustion at the 
portion of the vaporization plate 4 where the fuel density is high. 
Now, a ninth preferred embodiment of the present invention will be 
described hereinbelow. 
FIG. 11 is a sectional view showing a combustion heater according to the 
ninth preferred embodiment, wherein the same or like elements are 
designated by the same reference numerals as those in FIG. 4. 
As shown in FIG. 11, in this preferred embodiment, a tubular vaporization 
member 4 is provided on an inner circumferential surface of the combustion 
tube 22 at a side of the open end 23 thereof in the foregoing fourth 
preferred embodiment shown in FIG. 4. The tubular vaporization member 4 is 
in the form of a porous body made of, such as, foam metal. 
In the combustion heater having the foregoing structure, the fuel injected 
from a fuel injection valve 33 is uniformly dispersed onto an inner 
circumferential surface of the tubular vaporization member 4. The fuel is 
then efficiently vaporized from the vaporization member 4 heated by a 
heater element 51 mounted onto the inner circumferential surface of the 
vaporization member 4. The heater element 51 is in the form of a sheath 
heater where a heater conductor is embedded at the center of a linear 
insulating member having a circular cross section. The heater element 51 
is fixed to the inner circumferential surface of the vaporization member 4 
in a curved or bent shape for increasing a contact area between the heater 
element 51 and the vaporization member 4, as in the foregoing sixth 
preferred embodiment. Accordingly, at the time of ignition, HC emissions 
due to the incomplete combustion can be effectively prevented. Further, at 
the time of extinction of flame, the problem of the evaporative emissions 
can be avoided. 
Now, a tenth preferred embodiment of the present invention will be 
described hereinbelow. 
FIG. 12 is a sectional view showing a combustion heater according to the 
tenth preferred embodiment, wherein the same or like elements are 
designated by the same reference numerals as those in FIG. 11. 
As shown in FIG. 12, in this preferred embodiment, a spray nozzle 32 along 
with a fuel cutoff valve 76 which are the same as those in FIG. 5 are 
provided instead of the fuel injection valve 33 in the foregoing ninth 
preferred embodiment. 
In this preferred embodiment, the foregoing advantage achieved in the ninth 
preferred embodiment can also be achieved. 
Now, an eleventh preferred embodiment of the present invention will be 
described hereinbelow. 
As shown in FIG. 13, in this preferred embodiment, a spark plug 92 used in 
the automotive engine is provided at a recessed portion of the upper wall 
of the housing half 11 instead of the glow plug 9 in the foregoing first 
preferred embodiment shown in FIG. 1. The spark plug 92 is arranged to 
penetrate the upper wall of the housing half 11 and further the 
circumferential wall of the mixture tube 21 so as to expose a tip of the 
spark plug 92 to the interior of the mixture tube 21. The other structure 
is the same as that in the first preferred embodiment. 
In the combustion heater having the foregoing structure, the mixture of the 
fuel and the combustion air is reliably ignited by means of spark 
discharge generated by the spark plug 92. 
Now, a twelfth preferred embodiment of the present invention will be 
described hereinbelow. 
As shown in FIG. 14, in this preferred embodiment, a spark plug 92 used in 
the automotive engine is provided at a recessed portion of the upper wall 
of the housing half 12 instead of the glow plug 9 in the foregoing second 
preferred embodiment shown in FIG. 2. The spark plug 92 is arranged to 
penetrate the upper wall of the housing half 12, the guide tube 24 and 
further the circumferential wall of the combustion tube 22 so as to expose 
a tip of the spark plug 92 to the interior of the combustion tube 22. The 
other structure is the same as that in the second preferred embodiment 
except that the fluid passage 13 is formed shorter for providing a space 
for the spark plug 92. 
In this preferred embodiment, the foregoing advantage achieved in the 
eleventh preferred embodiment can also be achieved. 
Now, a thirteenth preferred embodiment of the present invention will be 
described hereinbelow. 
FIG. 15 is a sectional view showing a combustion heater according to the 
thirteenth preferred embodiment, wherein the same or like elements are 
designated by the same reference numerals as those in FIG. 10. 
As shown in FIG. 15, in this preferred embodiment, a temperature sensor 61 
is provided in a fuel feed pipe 73 upstream of and close to a fuel 
injection valve 33 for measuring a temperature of the fuel flowing into 
the fuel injection valve 33. Further, a number of fins 122 are provided on 
an inner circumferential surface of a housing half 12 for improving heat 
exchange efficiency. The fins 122 are arranged at constant intervals in a 
circumferential direction of the inner surface of the housing half 12. 
Each of the fins 122 is in the form of an elongate plate and extends 
axially of a housing 1. 
At the time of ignition, the fuel is injected all over the surface of a 
vaporization plate 4 from the fuel injection valve 33 and then vaporized. 
The vaporized fuel is mixed with the combustion air in the neighborhood of 
a heated surface of a glow plug 9 and starts to burn. Since the fuel is 
supplied uniformly all over the surface of the vaporization plate 4 by the 
fuel injection valve 33, a distribution of the fuel on the vaporization 
plate 4 becomes uniform. This effectively solves the problem of HC 
emissions caused by the incomplete combustion at the portion of the 
vaporization plate 4 where the fuel density is high. 
FIG. 16 shows a time-domain variation of a voltage applied to the fuel 
injection valve 33 while a temperature of the fuel is low. The applied 
voltage to the fuel injection valve 33 is controlled by an ECU 6. The ECU 
6 controls, via the applied voltage, an operation of the fuel injection 
valve 33, that is, an adjusting amount of the fuel injection valve 33 
relative to the fuel, for adjusting a supply amount of the fuel to the 
burner 2. As appreciated from FIG. 16, the fuel supply to the vaporization 
plate 4, that is, to the burner 2 is performed in a pulsed fashion. 
Specifically, a constant voltage is applied to the fuel injection valve 33 
for a constant time at every given period. While the voltage is applied, 
the fuel injection valve 33 is opened to inject a constant amount of the 
fuel. 
On the other hand, when the fuel temperature increases, the viscosity of 
the fuel is lowered. As a result, even when the fuel injection valve 33 is 
opened for the same time period, an amount of the fuel injected for that 
time period is increased to enrich the mixture of the fuel and the 
combustion air. This causes the incomplete combustion to deteriorate the 
emissions in the exhaust gas. 
Accordingly, in this preferred embodiment, when the fuel temperature 
monitored through an output of the temperature sensor 61 exceeds a given 
value, the ECU 6 prolongs the fuel injection period with the fuel 
injection time being unchanged, as shown in FIG. 17, that is, from a 
broken line to a solid line in FIG. 17. With this arrangement, the fuel 
supply amount to the vaporization plate 4 per unit time is not increased, 
but is kept constant. 
As appreciated from the foregoing description, by controlling the fuel 
injection period of the fuel injection valve 33 depending on the output of 
the temperature sensor 61 monitoring the fuel temperature, the fuel amount 
supplied to the vaporization plate 4 can be held constant regardless of 
the fuel temperature so that a stoichiometric air-fuel ratio is maintained 
to prevent deterioration of the emissions in the exhaust gas. 
Now, a fourteenth preferred embodiment of the present invention will be 
described hereinbelow. 
In this preferred embodiment, the fuel injection time is controlled 
depending on the monitored fuel temperature, while the fuel injection 
period is kept constant. Accordingly, when the fuel temperature is 
increased, the fuel injection time is decreased from a broken line to a 
solid line as shown in FIG. 18. The other structure is the same as that in 
the thirteenth preferred embodiment. 
As appreciated, the foregoing advantage achieved in the thirteenth 
preferred embodiment can also be achieved in this preferred embodiment. 
Now, a fifteenth preferred embodiment of the present Invention will be 
described hereinbelow. 
FIG. 19 is a sectional view showing a main portion of a combustion heater 
according to the fifteenth preferred embodiment, wherein the same or like 
elements are designated by the same reference numerals as those in FIG. 
15. The other structure not shown in FIG. 19 is the same as that in FIG. 
15. 
As shown in FIG. 19, in this preferred embodiment, three fuel injection 
valves 33A, 33B and 33C are provided instead of the fuel injection valve 
33 shown in FIG. 15. The number of the fuel injection valves is not 
limited to three. As shown in FIG. 20, the ECU 6 reduces the number of the 
working fuel injection valve as the fuel temperature increases, while the 
fuel injection period and time are kept constant. 
As appreciated, the foregoing advantage achieved in the thirteenth or 
fourteenth preferred embodiment can also be achieved in this preferred 
embodiment. 
Now, a sixteenth preferred embodiment of the present invention will be 
described hereinbelow. 
In this preferred embodiment, the ECU 6 controls an operation of the air 
pump 82, that is, an adjusting amount of the air pump 82 relative to the 
air, for adjusting a supply amount of the combustion air to the mixture 
tube 21 depending on the monitored fuel temperature, while the fuel 
injection period and time are held constant. Accordingly, as shown in FIG. 
21, when the fuel temperature is increased to make the fuel supply amount 
larger, the air supply amount is increased correspondingly. The other 
structure is the same as that in the foregoing thirteenth preferred 
embodiment shown in FIG. 15. 
As appreciated, the foregoing advantage achieved in the thirteenth, 
fourteenth or fifteenth preferred embodiment can also be achieved in this 
preferred embodiment. 
Now, a seventeenth preferred embodiment of the present invention will be 
described hereinbelow. 
FIG. 22 is a sectional view showing a main portion of a combustion heater 
according to the seventeenth preferred embodiment, wherein the same or 
like elements are designated by the same reference numerals as those in 
FIG. 15. The other structure not shown in FIG. 22 is the same as that in 
FIG. 15. 
As shown in FIG. 22, in this preferred embodiment, a temperature sensor 61 
is provided in the neighborhood of a fuel injection valve 33 and in a 
housing half 11. Accordingly, instead of directly measuring the fuel 
temperature, the temperature sensor 61 monitors an ambient air temperature 
having a good temperature relationship to the fuel temperature. 
In this preferred embodiment, the fuel injection period, the fuel injection 
time or the air supply amount may be controlled as in the foregoing 
thirteenth, fourteenth or sixteenth preferred embodiment. Alternatively, 
it may be arranged that a plurality of the fuel injection valves are 
provided as in the foregoing fifteenth preferred embodiment, that the 
temperature sensor 61 is provided in the neighborhood of the fuel 
injection valves and in the housing half 11, and that the operation of the 
fuel injection valves is controlled as in the foregoing fifteenth 
preferred embodiment. As appreciated, the advantage achieved in the 
foregoing corresponding preferred embodiment can also be achieved in this 
preferred embodiment. 
Now, an eighteenth preferred embodiment of the present invention will be 
described hereinbelow. 
FIG. 23 is a sectional view showing a main portion of a combustion heater 
according to the eighteenth preferred embodiment, wherein the same or like 
elements are designated by the same reference numerals as those in FIG. 
15. The other structure not shown in FIG. 23 is the same as that in FIG. 
15. 
As shown in FIG. 23, in this preferred embodiment, a flow sensor 62 is 
provided in a fuel feed pipe 73 instead of the temperature sensor 61 shown 
in FIG. 15, for directly monitoring a variation of the fuel flow. A supply 
amount of the combustion air to a mixture tube 21 is controlled depending 
on the monitored fuel flow. 
As appreciated, this preferred embodiment is also effective as in the 
foregoing thirteenth to seventeenth preferred embodiments. 
Now, a nineteenth preferred embodiment of the present invention will be 
described hereinbelow. 
FIG. 24 is a sectional view showing a main portion of a combustion heater 
according to the nineteenth preferred embodiment, wherein the same or like 
elements are designated by the same reference numerals as those in FIG. 
15. The other structure not shown in FIG. 24 is the same as that in FIG. 
15. 
As shown in FIG. 24, in this preferred embodiment, an air amount sensor 64 
is provided in an air feed pipe 81 for monitoring an air supply amount to 
a mixture tube 21, and an oxygen concentration sensor 63 is provided in an 
exhaust-gas outlet 16 for monitoring an oxygen concentration in the 
exhaust gas after combustion in the burner 2. A deviation of an actual 
air-fuel ratio from a target air-fuel ratio is monitored based on outputs 
from these sensors, and a supply amount of the fuel or the combustion air 
is controlled based on the monitored deviation. 
As appreciated, this preferred embodiment is also effective as in the 
foregoing thirteenth to eighteenth preferred embodiments. 
In any of the foregoing thirteenth to nineteenth preferred embodiments, the 
fuel injection valve/valves may be replaced by either of the other fuel 
feed means employed in the foregoing preferred embodiments and the prior 
art shown in FIG. 25. 
It is to be understood that this invention is not to be limited to the 
preferred embodiments and modifications described above, and that various 
changes and modifications may be made without departing from the spirit 
and scope of the invention as defined in the appended claims.