Microwave probe and rotary body detecting apparatus using the same

A microwave probe has a cylindrical support made of stabilized zirconia being excellent in heat insulation, and the cylindrical support is threadably installed at a partitioning wall to partition an atmosphere of high temperature. The support is provided at the center with a through hole, and an antenna for transmitting or receiving microwave is installed at one opening of the through hole positioning at outside of the partitioning wall, and a metal ring member is installed at other opening of the through hole positioning within the partitioning wall. The transmitting and receiving antenna and the ring member are fixed to respective openings by a ceramic adhesive which is filled in the through hole and excellent in heat insulation. A part of the ring member projects in the atmosphere. A rotary body breakage detecting apparatus has the microwave probe installed at a cabinet wall to cover a wing body rotating in an atmosphere of high temperature, and a microwave oscillator and a microwave detector are connected to the probe through a circulator. A breakage detecting circuit is connected to the microwave detector. The breakage detecting circuit detects that peak value of the receiving signal outputted from the detector (the signal pulsating with rotation of the wing body) varies beyond a prescribed range, and generates signal informing the breakage of the wing body.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a microwave probe having a thermal 
insulating structure and a detecting apparatus to detect breakage of a 
rotarybody in an atmospher of high temperature using the probe. 
2. Description of the Prior Art 
In recent years, microwave circuits can be constituted using a quite 
compact IC structure by development of a solid state circuit element, a 
microstrip and the like. With this devlopement, application of microwave 
has been tried in various measuring fields other than communication. In 
U.S. Pat. No. 4,384,480 for example, method and apparatus are disclosed 
where microwave is transmitted into a combustion chamber of an engine and 
top dead center position of a piston is determined from the received 
waveform. 
For such purpose, a microwave probe must be installed on a wall of a 
combustion chamber rising to a high temperature beyond 1000.degree. C. In 
a probe structure of the prior art, the heat from this combustion chamber 
may be conducted to a coaxial cable or a circuit device connected to the 
probe, and therefore the deterioration of such connected device is apt to 
occur. On the other hand, in order to detect breakage of a rotary body 
rotating at high speed in an atmosphere of high temperature, such as a 
turbine, an apparatus to detect abnormal vibration or abnormal sound in a 
rotary shaft has been proposed in the prior art. In this apparatus, 
however, the broken portion cannot be specified securely and reliability 
of the detection is not very high. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a microwave probe which can detect 
behavior of a body in an atmosphere of high temperature. 
Another object of the invention is to provide a microwave probe which is 
installed at a partitioning wall to partition an atmosphere of high 
temperature and excellent in heat insulation. 
A further object of the invention is to provide a rotary body breakage 
detecting apparatus which can securely detect breakage of a rotary body 
rotating in an atmosphere of high temperature. 
Still another object of the invention is to provide a rotary body breakage 
detecting apparatus which can securely detect breakage of a rotary body 
using the microwave probe. 
A microwave probe of the invention comprises a support fixed to a 
partitioning wall for partitioning an atmosphere of high temperature, and 
the support is made of heat insulating material. The support is provided 
at one end outside the partitioning wall with an antenna for transmitting 
or receiving microwave, and at other end exposing in the atmosphere with a 
conductive ring, member projecting partly in the atmosphere. 
According to a microwave probe of above-mentioned structure, microwave is 
transmitted or received in an atmosphere of high temperature at favorable 
condition, and at the same time the heat transmission to the antenna is 
prevented effectively. 
In a rotary body breakage detecting apparatus of the invention, the 
microwave probe is installed at a wall of a cabinet to cover a rotary body 
to be detected in an atmosphere of high temperature, microwave is 
transmitted or received from the probe into the cabinet, and if level of 
receiving signal obtained corresponding to intensity of receiving 
microwave varies beyond a prescribed level, breakage detecting means 
generates breakage signal of the rotary body. 
According to a breakage detecting apparatus of above-mentioned structure, 
breakage of a rotary body can be securely detected.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a first embodiment of the invention. In the figure, symbol A 
designates a partitioning wall to seal an atmoshere of high temperature, 
for example, a cylinder wall of an engine or a case wall of a turbine, 
which is at a high temperature from the atmosphere. The partitioning wall 
A is provided with a through hole A1, and a threaded portion is formed on 
an inner circumferential surface of the through hole A1. A microwave probe 
1 according to the invention is fixed to the through hole A1. 
The probe 1 has a cylindrical support 11 which is threadably installed to 
the through hole A1 by a metal thread ring 12 fitted to the outer 
circumference of the support 11. The support 11 is made of a material 
having heat insulating and electric insulating property, such as 
stabilized zirconia or fire brick. The support 11 has a through hole 11a 
formed at the center, and an SAM type coaxial plug 13 having known 
structure is installed on the upper opening of the through hole 11a. An 
inner conductor projects from the lower surface of the coaxial plug 13, 
and the top end of the inner conductor is bent and short circuited towards 
an outer conductor in order to form a loop antenna 14. The coaxial plug 13 
is connected through a coaxial cable to a microwave oscillator or a 
microwave detector. 
A ring member 15 formed of metal conductor is spaced from the loop antenna 
14 and installed at the lower opening of the through hole 11a, and the 
ring member 15 and the coaxial plug 13 are fixed by a ceramic adhesive 16 
("Sumiceram" of Sumitomo Chemical Co., Ltd. in the embodiment) which is 
injected in the through hole 11a and has excellent heat insulation 
properties. In this state, the lower half of the ring member 15 projects 
in the atmosphere. 
In the probe 1 of above-mentioned structure, microwave transmitted from the 
loop antenna 14 is effectively electromagnetically coupled to the ring 
member 15 and then emitted with little attenuation from the lower half of 
the ring member 15 into the atmosphere of high temperature. 
Microwave projected in the atmosphere of high temperature is caught by the 
ring member 15 and received by the antenna 14 spaced from the ring member 
15. Heat transmission from the atmosphere of high temperature to the 
coaxial plug 13 is effectively inhibited since the loop antenna 14 and the 
ring member 15 are spaced from each other in the heat insulating adhesive 
16. Also, heat transmission from the partitioning wall A of high 
temperature to the coaxial plug 13 is effectively inhibited by the support 
11 of heat insulating material. Consequently, deterioratio of the coaxial 
cable or the like to be connected to the coaxial plug 13 prevented. 
FIG. 2 shows a second embodiment of the invention. In the figure, a 
dielectric resonator 17 as a microwave relaying means is installed at a 
prescribed position between a loop antenna 14 and a ring member 15. 
Microwave is transmitted or received through the resonator 17, and thereby 
a distance between the antenna 14 and the ring member 15 may be increased 
with little attenuation of microwave and therefore the heat transmission 
can be effectively inhibited. 
In place of the resonator 17, another ring member having the same 
constitution as that of the ring member 15 may be used. 
If the antenna 14, the ring member 15 and the resonator 17 are embedded 
directly into the support 11 in the above embodiments, the adhesive 16 is 
not necessary. Although the antenna 14 need not be a loop antenna, 
microwave can be effectively transmitted or received in this constitution 
of loop antenna. 
Following embodiments disclose rotary body breakage detecting apparatuses 
using a microwave probe in the above embodiments already described. 
FIG. 3 shows a third embodiment of the invention. In the figure, a wing 
body 2, e.g. a turbine fan, is fixed to the top end of a rotary shaft 21 
and rotated as a rotary body. The wing body is covered by a metal cabinet 
A as partitioning wall. The cabinet A is provided with microwave probes 
1A, 1B on opposite side walls. The probe 1A is connected through a coaxial 
cable 31 to a microwave oscillator 4. On the other hand, the probe 1B is 
connected through a coaxial cable 32 to a microwave detector 5, and the 
receiving signal 5a generated from the detector 5 is inputted to a 
breakage detecting circuit 6. Microwave transmitted at a definite 
frequency from the probe 1A into the cabinet A is resonated in the cabinet 
A as a resonance cvity and then comes to the probe 1B. 
FIG. 4 shows a circuit diagram of the detecting circuit 6. In the figure, 
an a.c. amplifier 601 amplifies the receiving signal 5a of the detector 5 
(FIG. 3) and outputs amplified signal 601a. Comparators 602, 603, 604 
compare the amplified output 601a with constant voltages V1, V2, V3 
respectively. If the former is greater than the latter, the comparators 
602, 603 604 generate output signals 602a, 603a, 604a at "H" level 
respectively. Numeral 605 designates an RS flip-flop, numberal 607 a 
D-type flip-flop, numeral 609 a current amplifier, numeral 610 a 
thyristor, and numeral 611 a warning lamp. 
Operation of an apparatus having the above-mentioned constitution will now 
be described referring to FIG. 5. 
Microwave transmitted from the microwave probe 1A is resonated in the 
cabinet A. Since a space formed within the cabinet A varies with rotation 
of the wing body 2, the resonance intensity varies periodically. 
Consequently, the amplification signal obtained by amplifying the 
receiving signal 5a pulsates periodically as shown in FIG. 5(1). The 
figure illustrates that the wing body 2 of four wings is detected, and 
symbols 1, 1', 1", 2, 3, 3', 4, 4' on the upper side of the signal 
waveform represent that pulsating parts correspond tot he first through 
fourth wings. In the case of four wings, the same space if formed four 
times per one revolution of the rotary shaft 21, thereby the same waveform 
is repeated at a prescribed period. As seen from the figure, voltage V1 is 
set to a value so that if the signal 601a pulsates, it necessarily goes 
across the voltage level. On the other hand, voltages V2, V3 are set so 
that if there is no breakage in the wing body 2, the peak value of the 
pulsation is always positioned between both voltage levels (at 1, 2, 3, 4 
in FIG. 5(1)). 
If there is no breakage in the wing body 2, signal 602a (FIG. 5(2)) and 
signal 603a (FIG. 5(3)) are outputted in pulse form corresponding to the 
pulsation of signal 601a, but signal 604a (FIG. 5(4)) is not outputted. 
On the contrary, if a part of the wing body 2 is broken, a space formed 
within the cabinet A is no longer a repetition of the same space, but a 
peak value of pulsation of the signal 601a varies during one revolution of 
the rotary shaft 21 (at 1', 2', 3', 4' in FIG. 5(1)). Consequently, the 
peak value of the signal 601a becomes lower than voltage V2 (at 1' in FIG. 
5(1)) or higher than voltage V3 (at 4' in FIG. 5(1)). In the former case, 
the signal 603a is not outputted, thereby output signal 605a (FIG. 5(5)) 
of the flip-flop 605 is inputted to the flip-flop 607, which is set to 
generate output signal 607a (FIG. 5(6)). The signal 607a is inputted to 
the OR gate 608. On the contrary, in the latter case, output signal 604a 
(FIG. 5(4)) is generated from the comparator 604 is also inputted to the 
OR gate 608. 
Output signal 608a (FIG. 5(7)) of the OR gate 608 is inputted to the 
current amplifier 609, and the warning lamp 611 is lit by the thyristor 
610. 
The microwave probe 1A in the embodiment may be used both for transmitting 
and receiving, thereby the probe 1B may be omitted. This constitution is 
shown as a fourth embodiment of the invention in FIG. 6. In the figure, 
the probe 1A is connected through a circulator 7 to a microwave oscillator 
4 and a microwave detector 5. Microwave generated from the oscillator 4 is 
transmitted by the circulator 7 to the probe 1A and emitted into the 
cabinet A, and microwave received by the probe 1A is transmitted by the 
circulator 7 to the detector 5. 
FIG. 7 shows a fifth embodiment of the invention, and a breakage detecting 
apparatus in the embodiment detects breakage of a rotary shaft 21 in 
addition to breakage of the wing body 2. In FIG. 7, a metal cabinet A' is 
installed to cover the rotary shaft 21 thereby a microwave resonance 
cavity is constituted. The cabinet A' is provided with a probe 1A' for 
transmitting and receiving microwave, and the probe 1A' is connected 
through a circulator 7' to the microwave oscillator 4' and the microwave 
detector 5'. Receiving signal 5'a generated from the detector 5' is 
inputted to a breakage detecting circuit 6. 
FIG. 8 shows a circuit diagram of the detecting circuit 6. In the figure, 
comparators 612, 613 compare the receiving signal 5'a with constant 
voltages V4, V5 respectively. If the former is greater than the latter, 
the comparators 612, 613 generate an output signal at an "H" level. 
Numerals 615, 619 designate D-type flip-flops, numeral 616 a current 
amplifier, numeral 617 a thyristor, and numeral 618 a warning lamp. A 
circuit enclosed by dash-and-dot line in FIG. 8 is the same as that of the 
third embodiment enclosed by dash-and-dot line in FIG. 4. 
If the wing body 2 is broken, the flip-flop 619 is set by signal 608a and 
the warngin lamp 611 is lit through the thyristor 610. Then the flip-flop 
615 is reset by the output signal 619a of the flip-flop 619. 
When the rotary shaft 21 is in the normal state, the receiving signal 5'a 
is at a constant level between voltages V4, V5 (at left hafl in FIG. 
9(1)), and signal 614a (FIG. 9(2)) resulting from output signal of the 
comparator 612 inverted by the inverter 614 and output signal 613a (FIG. 
9(3)) of the comparator 613 are at "L" level. If the rotary shaft 21 is 
broken, the receiving signal 5'a becomes lower than voltage V4 (solid line 
at right half in FIG. 9(1)) or higher than this (broken line at right half 
in FIG. 9(1)), thereby the signal 614a or the signal 613a becomes "H" 
level. Consequently, the flip-flop 615 is set, and the warning lamp 618 is 
lit through the current amplifier 616 and the thyristor 617. Then the 
flip-flop 619 is reset by output signal 615a of the flip-flop 615. Thus, 
breakage of the wing body 2 and breakage of the rotary shaft 21 can be 
discriminated distinctly. 
FIG. 10 shows a circuit diagram of a breakage detecting circuit 6 in a 
sixth embodiment of the invention. Using the detecting circuit 6 of the 
embodiment, breakage of the wing body 2 and breakage of the rotary shaft 
21 can be discriminated distinctly even by apparatus constitution in FIG. 
6. In FIG. 10, an a.c. amplifier 620 amplifies receiving signal 5a of the 
detector 5 (FIG. 6) and outputs amplification signal 620a. Comparators 
621, 622 compare the amplification signal 620a with constant voltages V1, 
V2. If the former is greater than the latter, the comparators 621, 622 
generate output signals 621a, 622a at "H" level respectively. A counter 
623 outputs count-up pules 623a at every pulse input of the prescribed 
number (specified to 5 being equal to the wing number of the wing body 2 
in this embodiment). Numeral 624 designates a D-type flip-flop, and 
D-terminal of the flip-flop 624 is connected to powe source V at "H" 
level. A counter 626 counts input pulse 625a and generates count output, 
and an indicator 627 indicates the count output. The comparator 622 and 
the flip-flop 624 constitute an initial breakage detecting circuit 62. 
Operation of a breakage detecting circuit in above-mentioned constitution 
will now be described referring of FIG. 11. 
Amplification signal 620a by amplifying the receiving signal 5a pulsates 
periodically with rotation of the wing body 2 as shown in FIG. 11(1). 
Voltage V1 is set to value so that if the signal 620a pulsates it 
necessarily comes across the voltage level. Voltage V2 is set to value so 
that if there is no breakage in the wing body 2 or the rotary shaft 21, 
peak vlaue of the pulsation does not exceed the voltage level. 
Consequently, the comparator 621 outputs pulse signal 621a (FIG. 11(2)) at 
every pulsation of the signal 620a. The counter 623 outputs pulse signal 
623a (FIG. 11(4)) at every input of the signal 621a of five pulses, that 
is, at every one revolution of the rotary shaft 21. 
If the wing body 2 or the rotary shaft 21 begins to be broken, a space 
formed with in the cabinet A becomes no more repetition of the same space, 
but the resonance intensity of microwave varies thereby peak value of the 
signal 620a exceeds voltage V2 (at point X in FIG. 11(1)). Thereby pulse 
signal 622a (FIG. 11(3)) is outputted from the comparator 622 and output 
signal 62a (FIG. 11(5)) of the flip-flop 624 is set to "H" level. The 
signal 62a as initial breakage signal opens the AND gate 625, and the 
signal 623a is inputted as signal 625a (FIG. 11(6)) to the counter 626 and 
counted. The count value is indicated in the indicator 627. 
If the wing body 2 or the rotary shaft 21 is broken completely, the 
rotation is stopped and therefore pulsation of the signal 620a is stopped 
(at point Y in FIG. 11(1)). Consequently, the signal 623a is no more 
outputted, and the counter 626 stores the rotation number from starting of 
breakage of the wing body 2 to the complete breakage. 
According to an experiment of the inventors, the rotation number from 
starting of breakage to the complete breakage is clearly different at 
breakage of the wing body 2 and at breakage of the rotary shaft 21. The 
rotation number is 1-2 in the former and several tens in the latter. 
Consequently, whether the broken part is at the wing body 2 or at the 
rotary shaft 21 can be securely discriminated from the count number of the 
counter 626 indicated on the indicator 627. 
Although the pulsating number of receiving signal is represented in terms 
of the rotation number in the above embodiment, the pulsating number may 
be directly indicated in integration. 
The voltage V2 may be set to a value so that the amplification signal 620a 
does not become lower than the voltage V2 at normal state. 
As above described, a microwave probe of the invention has a constitution 
where an antenna for transmitting or receiving microwave and a conductive 
ring member to be coupled electromagnetically thereto are spaced from each 
other and held at one end and other end of a support made of heat 
insulating material. In this constitution, microwave can be transmitted or 
received in favorable condition and at the same time the heat transmission 
to the antenna can be effectively inhibited. 
A rotary body breakage detecting apparatus of the invention has 
constitution where the microwave probe is installed at a cabinet wall 
formed to cover a rotary body, microwave is transitted in the cabinet and 
resonated within the cabinet and then received, and if the receiving 
intensity comes beyond a prescribed region the breakage of the rotary body 
can be knwon. In this constitution, breakage of a wing body or the like 
rotating in connection to the rotary shaft can be directly detected and 
the broken position can be determined distinctly.