Automatic heating appliance with food identifying function

A heating appliance for heating an object within a heating chamber. In the heating chamber are formed rack rails on which a table is located and a heater. The rack rails are stepwise arranged so as to allow the table to take a desired position corresponding to the kind of an object to be heated. The heating applicance includes a distance-measuring sensor for measuring a distance to the table means or the object. A control unit, may comprising a known microcomputer, controls the heater on the basis of the distance measured by the sensor so as to appropriately heat the object in accordance with its kind.

BACKGROUND OF THE INVENTION 
The present invention relates generally to automatic heating appliances, 
and more particularly to such an automatic heating appliance for 
controlling the heating temperature of an object in accordance with the 
kind of the object. The present invention is applicable particularly, but 
not exclusively, to an oven for cooking a food. 
Known are heating appliances such as electric oven and gas oven for heating 
an object with elevation of the temperature of air within a heating 
chamber and convection of the heated air. Such a heating appliance 
generally has a plurality of keys on an operating pannel, which are 
operated in accordance with the kind, class or nature, of the object to be 
heated within the heating chamber because the cooking time period and 
heating temperature are respectively different in accordance with the 
class or nature of the object. The cooking time period and the heating 
temperature are respectively selected by different keys and one of a 
plurality of racks provided within the heating chamber is selected in 
accordance with the class of the object to be heated so as to obtain a 
desired heat distribution. The selection of the keys is troublesome for 
users and an error in selection of the correct rack causes failure of 
cooking of the object. As a result improvement is desirable from the 
viewpoint of simplification of handling the appliance and prevention of 
the cooking failure. 
SUMMARY OF THE INVENTION 
The present invention has been developed in order to eliminate the 
above-mentioned drawbacks inherent to the conventional heating appliances. 
It is therefore an object of the present invention to provide a new and 
improved automatic heating appliance which is capable of automatically and 
appropriately controlling the heating temperature by determining the kind 
or nature of the object to be heated. 
A feature of an automatic heating appliance according to the present 
invention is to detect the class of an object to be heated on the basis of 
the position of the object within a heating chamber or state of gas 
generated from the object in response to heating and automatically control 
the heating temperature of the object in accordance with the class of the 
object, resulting in reduction of the number of operating keys for cooking 
instruction and simplification of operation of the appliance. 
In accordance with the present invention, there is provided a heating 
appliance with a heating chamber, comprising: heating means for heating an 
object which is encased within the heating chamber; table means provided 
within the heating chamber, the object being placed on the table means; 
rack means within the heating chamber so that the table means is held at a 
desired position; sensor means for measuring a distance to the table means 
or the object; and control means for controlling the heating means on the 
basis of the distance measured by the sensor means. 
In accordance with the present invention, there is further provided a 
heating appliance with a heating chamber, comprising: heating means for 
heating an object which is encased within the heating chamber; table means 
provided within the heating chamber, the object being placed on table 
means; rack means including pairs of supporting rails within the heating 
chamber so that the table means is held at a desired position; first 
sensor means for measuring a distance to the table means or the object; 
second sensor means for sensing a vapor and/or gas generated from the 
object; and control means for controlling the heating means on the basis 
of the distance measured by the sensor means and the generation state of 
the gas sensed by the second sensor means.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to FIG. 1, there is illustrated an arrangement of an 
automatic heating appliance according to an embodiment of the present 
invention. In FIG. 1, heating instruction is transmitted to a control 
section 5 through a full-automation key board 4. The keyboard 4 is mounted 
on an operating panel 3 which is illustrated in FIG. 2 in a perspective 
view showing the external appearance of the automatic heating appliance. 
Numerals 1 and 2 represent a housing and a door of the appliance, 
respectively. In response to the heating instruction, the control section 
5, which may comprise a known microcomputer with a central processing unit 
(CPU) and memories, energizes a distance-measuring sensor 6 through a 
drive and detection circuit 18 so as to measure the distance D to a table 
8 on which an object 7 is placed, the distance-measuring sensor being 
provided on the ceiling of a heating chamber 9. Provided within the 
heating chamber 9 are stepwise pairs of rack rails 10, one pair of which 
is selected in accordance with the class of the object 7. For example, the 
upper rack rails 10 are used for cooking of a cookie, the middle rack 
rails 10 are used for cooking of a bread and a chou, and the lower rack 
rails 10 are used for cooking of a cake. The desired position may be 
determined in accordance with the arrangement of the heating chamber 9, 
i.e., heat distribution and so on. The distance-measuring sensor 6 
measures the distance D to the table 8 and this distance measurement 
allows detection of the position of the table 8, which may be arranged as 
illustrated in FIG. 3 such that its flange-portions are placed on the pair 
of the rack rails 10. The detection of the position of the table 8 further 
allows estimation of the kind of the object 7. The result of the 
estimation is indicated on a display section 11 as shown in FIG. 4, the 
display section 12 comprising a class-indicating portion 14 and further 
time-indicating portion 12 and temperature-indicating portion 13. The 
indication of the class of the object 7 to be heated allows confirmation 
of the class of the object 7 by the user. After the indication, the 
control section 5 enerzises upper and lower heaters 16 through a driver 15 
so as to obtain a heating temperature corresponding to the class of the 
object 7 specified by the user. The heaters 16 may be of the electric type 
or gas type. The temperature within the heating chamber 9 is sensed by 
means of a temperature sensor 17 and the sensed temperature information is 
supplied through a detection circuit 19 with an analog-to-digital 
converter to the control section 5 which in turn controls the power supply 
to the heaters 16, i.e., distribution of the power supply to the upper and 
lower heaters 16 and the heating time, in accordance with the appointed 
object class. 
FIG. 5 is a time chart illustrating one example of methods of power supply 
to the upper and lower heaters 16 and controlled temperature obtained as 
the result of the power supply. As understood from FIG. 5, the temperature 
is controllable by control of the energizing time period Tu to the upper 
heater 16 and the energizing time period Td to the lower heater 16. For 
example, the heating temperature is controlled to 160.degree. C. when the 
object 7 is a cookie and to 180.degree. C. when it is a puff. Furthermore, 
the overall heating time period T is determined in accordance with the 
class of the object 7. For example, the time period T is set to 15 minutes 
when it is a cookie and to 25 minutes when it is a puff. 
A description will be made hereinbelow in terms of the distance-measuring 
sensor 6 and the drive and detection circuit 18 with reference to FIGS. 6 
and 7. FIG. 6 is a cross-sectional view showing one example of ultrasonic 
sensor usable as the distance-measuring sensor 6. The ultrasonic sensor 6, 
as shown in FIG. 6, comprises a piezoelectric device 20, a conically 
shaped resonator 22 coupled through a coupling shaft 21 to the 
piezoelectric device 20, terminals 24 coupled through lead lines 23 to the 
piezoelectric device 20, a terminal plate 25 for fixedly securing the 
terminals 24, a case 26, a beam shaping plate 27 for covering an opening 
of the case 26 positioned so as to face the conically shaped resonator 22, 
and an acoustic absorption sheet 28 provided on the terminal plate 25. A 
detailed description thereof will be omitted because the arrangement 
thereof is disclosed in "National Technical Report" Vol. 29, pages 504 to 
514, No. 3, 1983. The distance-measuring sensor 6 is not limited to the 
above-mentioned ultrasonic sensor, but other sensors such as infrared 
sensor are applicable thereto. FIG. 7 is a block diagram showing one 
example of arrangements of the drive and detection circuit 18. The drive 
and detection circutt 18 comprises a transmitting circuit 29 and a 
receiving circuit 30. The transmitting circuit 29 drives the 
distance-measuring sensor 6 in response to a timing control signal from 
the control section 5 and the receiving circuit 30 receives an output 
signal of the distance-measuring sensor 6 corresponding to the echo wave 
returning from the object 7. The output signal of the receiving circuit 30 
is supplied to a comparator 31 where the output signal of the receiving 
circuit 30 is compared with a reference signal. When the level of the 
output signal thereof exceeds the level of the reference signal, the 
output signal thereof is latched and supplied to a data-processing portion 
of the control section 5. The control section 5 counts the time period 
from the transmission to the reception and calculates the distance to the 
table 8 or the object 7 on the basis of the propagating time of the 
ultrasonic wave and then to detect the position of the table 8 and the 
height of the object 7. The detection of the height of the object 7 allows 
discrimination of the kind of the object 7 even if the table 8 takes the 
same position. That is, at the time of the start of heating, the chou is 
lower in height and the bread is higher in height. Furthermore, since the 
condition of expansion of the object 7 can be detected, it is possible to 
determine the kind of the object 7 on the basis of the condition of the 
expansion. 
FIG. 8 is an illustration of an automatic heating appliance according to a 
second embodiment of the present invention which is arranged so that the 
class of an object to be heated is determined on the basis of the position 
of an object-mounting table and the generating state of vapor or gas from 
the object. Parts corresponding to those in FIG. 1 are marked with the 
same numerals and the description thereof will be omitted for brevity. In 
response to operation of a full-automation key 4, a control section 5 
starts heating of an object 7 placed on a table 8 positioned by rack rails 
10 arranged within a heating chamber 9. The heating causes generation of 
vapor or gas from the object 7. The generated vapor or gas is detected by 
a gas sensor 32 which is located at the side wall of the heating chamber 
9. The gas sensor 32 may be a humidity sensor in this embodiment and the 
gas sensor 32 and the detection circuit 33 can be realized in accordance 
with the description in Japanese Patent Provisional Publication No. 
51-134951, for example. The gas-generating information is supplied through 
a detection circuit 33 to the control section 5 to check the generating 
state of the gas or vapor. The control section 5 determines the class of 
the object 7 on the basis of the generating state thereof and the position 
of the table 8 which is measured by means of a distance-measuring sensor 6 
and a drive and detection circuit 18. FIG. 9 is a time chart showing a 
method of determination of the class of the object 7, in which the 
vertical axis represents variation of the output of the sensor 32, i.e., 
absolute humidity, and the horizontal axis represents elapsed time. As 
understood from FIG. 9, the gas-generating state is varied in accordance 
with the kind of the object 7 and therefore the kind of the object 7 can 
be determined by detection of the gas-generating state even if the table 8 
takes the same position. Accordingly, the control section 5 plots the 
outputs of the gas sensor 32 with respect to time and determines the kind 
of the object 7 in accordance with a curve formed by the plotting of the 
outputs. For example, even if the cooking is started as a cake in spite of 
the object 7 being a bread, since the kind of the object 7 can be 
determined in accordance with the gas-generating state, the cooking error 
can be removed by changing the heating temperature at the time of the 
determination of the kind of the object 7. 
It should be understood that the foregoing relates to only preferred 
embodiments of the present invention, and that it is intended to cover all 
changes and modifications of the embodiments of the invention herein used 
for the purposes of the disclosure, which do not constitute departures 
from the spirit and scope of the invention.