U.S. patent application number 09/778090 was filed with the patent office on 2001-11-22 for method and apparatus for inspecting communicating hole of a cast molded article.
This patent application is currently assigned to RYOEI ENGINEERING CO., LTD.. Invention is credited to Itou, Toyokazu, Satou, Miyuki, Vanegas, Oscar.
Application Number | 20010042408 09/778090 |
Document ID | / |
Family ID | 18653782 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010042408 |
Kind Code |
A1 |
Satou, Miyuki ; et
al. |
November 22, 2001 |
Method and apparatus for inspecting communicating hole of a cast
molded article
Abstract
A transmitter of audible sound waves is disposed at one end of a
communicating hole of a cast molded article such as a cylinder
block, and a receiver of audible sound waves is disposed at the
other end of the communicating hole. The quality of the
communicating hole is determined by receiving audible sound waves
from a transmitter which have passed through the communicating hole
and computing and processing a frequency spectrum of the received
audible sound waves based on a reference frequency spectrum.
Inventors: |
Satou, Miyuki; (Toyota-city,
JP) ; Vanegas, Oscar; (Nagoya-city, JP) ;
Itou, Toyokazu; (Nissin-city, JP) |
Correspondence
Address: |
PARKHURST & WENDEL, L.L.P.
1421 Prince Street, Suite 210
Alexandria
VA
22314-2805
US
|
Assignee: |
RYOEI ENGINEERING CO., LTD.
|
Family ID: |
18653782 |
Appl. No.: |
09/778090 |
Filed: |
February 7, 2001 |
Current U.S.
Class: |
73/587 ;
73/579 |
Current CPC
Class: |
G01N 29/4481 20130101;
G01N 29/12 20130101; G01N 2291/048 20130101; G01N 2291/269
20130101; G01N 29/348 20130101 |
Class at
Publication: |
73/587 ;
73/579 |
International
Class: |
G01H 001/00; G01N
029/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 19, 2000 |
JP |
2000-147624 |
Claims
What is claimed is:
1. A method of inspecting a communicating hole of a cast molded
article, comprising the steps of: emitting an audible sound wave
from one end of a communicating hole of a cast molded article,
receiving the audible sound wave which has passed through said
communicating hole at another end of the communicating hole, and
determining quality of the communicating hole by computing and
processing a frequency spectrum of said received audible sound wave
based on a reference frequency spectrum.
2. The method of inspecting a communicating hole of a cast molded
article according to claim 1, further comprising the step of:
sweeping an audible sound wave emitted from a transmitter from a
low frequency to a high frequency or from a high frequency to a low
frequency.
3. The method of inspecting a communicating hole of a cast molded
article according to claim 1, wherein an audible sound wave emitted
from said transmitter is an audible sound wave of a frequency of 1
to 20,000 Hz.
4. The method of inspecting a communicating hole of a cast molded
article according to claim 1, wherein said computing and processing
computes and processes a frequency spectrum of said received
audible sound wave by means of a neural network.
5. The method of inspecting a communicating hole of a cast molded
article according to claim 4, wherein said computing and processing
outputs a value corresponding to a probability that an inspected
product is good or bad as an output value and determines quality of
the communicating hole based on this output value.
6. An apparatus for inspecting a communicating hole of a cast
molded article, comprising: a transmitter of an audible sound wave
disposed at one end of a communicating hole of a cast molded
article; a receiver disposed at another end of said communicating
hole for receiving the audible sound wave from the transmitter that
has passed through the communicating hole; and a computing and
processing device for determining quality of the communicating hole
by computing and processing a frequency spectrum of the audible
sound wave received by said receiver based on a reference frequency
spectrum.
7. The apparatus for inspecting a communicating hole of a cast
molded article according to claim 6, wherein said transmitter
sweeps said audible sound wave from a low frequency to a high
frequency or from a high frequency to a low frequency.
8. The apparatus for inspecting a communicating hole of a cast
molded article according to claim 6, wherein said transmitter emits
an audible sound wave of a frequency of 1 to 20,000 Hz.
9. The apparatus for inspecting a communicating hole of a cast
molded article according to claim 6, wherein said computing and
processing device computes and processes a frequency spectrum of
said received audible sound wave by means of a neural network.
10. The apparatus for inspecting a communicating hole of a cast
molded article according to claim 9, wherein said computing and
processing device outputs a value corresponding to a probability
that an inspected product is good or bad as an output value.
11. The apparatus for inspecting a communicating hole of a cast
molded article according to claim 10, further comprising: a
plurality of transmitters and/or receivers; and wherein said
computing and processing device determines quality of a
communicating hole based on a frequency spectrum of an audible
sound wave sent and received between said plurality of transmitters
and/or receivers.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method and apparatus for
inspecting a communicating hole of a cast molded article for
inspecting the degree of obstruction of a communicating hole formed
in a cast molded article, and more particularly relates to a method
and apparatus for inspecting a communicating hole of a cast molded
article suitable for inspecting the degree of obstruction of a
communicating hole for cooling water formed within a cast molded
article such as a cylinder block of an engine.
[0003] 2. Description of the Related Art
[0004] A cast molded article such as a cylinder block or a cylinder
head of an automobile is provided with a network of communicating
holes therein for cooling water. These communicating holes are
formed by arranging a core within a mold. However, there are cases
in which heat and the flow of molten metal during cast molding
cause the core to crack and break, obstructing the communicating
hole and making it narrow. Since this type of defect may lead to
poor cooling, poor engine efficiency, and seizure of the engine, it
is necessary to inspect the communicating holes of all products
after cast-molding. However, because the communicating holes of
which there is a complex network inside cast molded articles twist
and bend, they can not be directly visually checked for defects as
can be linear communicating holes.
[0005] Therefore, the quality of communicating holes is determined
using various means such as by manually shining a light into the
opening of a communicating hole and looking at the reflected light
that passes through to the other end, or by passing a wire or the
like through the communicating hole. The quality of complex
communicating holes is determined using such means as an endoscopic
light source capable of bending at the end or observing the inside
with optic fiber. However, with the method of passing a wire
through the communicating hole it was difficult not only to pass
the wire through a communicating hole, but also to know just how
narrow the communicating hole was. Moreover, the operation was
troublesome. Also, an endoscope and optic fiber were not able to be
inserted all the way into the inner portion of complex
communicating holes and much manual labor was required.
[0006] In an attempt to automate inspection, investigations have
also been made into detecting light illuminated into a
communicating hole from an opening thereof with an optical sensor
disposed at an adjoining communicating hole opening, as well as
feeding air into a communicating hole from an opening thereof and
detecting the air pressure and air flow rate at an adjoining
communicating hole opening. However, because the inside of a
communicating hole changes color and its surface becomes rough,
light passed through a communicating hole attenuates to {fraction
(1/100)} or less, so that sufficient determination can not be made.
Also, with the air method, due to the fact that air leaks from
other communicating holes that branch off, the air pressure
attenuates to {fraction (1/1000)} or less at the branching point,
so that sufficient determination can not be made. Therefore,
practical application of either of these methods was difficult. In
addition, it is necessary to fit the air feed hole and pressure
sensor tightly against the communicating hole opening during
measuring so air does not leak, as well as have the light source
and light sensor as close as possible to the communicating hole
opening in order to inhibit attenuation. These make setup prior to
measuring troublesome and time consuming.
SUMMARY OF THE INVENTION
[0007] The object of the present invention is to provide a method
and apparatus for inspecting a communicating hole of a cast molded
article which enables reliable determination of the quality of a
communicating hole of a complex shape formed in a cast molded
article.
[0008] A first aspect of the present invention is a method of
inspecting a communicating hole of a cast molded article, in which
audible sound waves are emitted into one end of a communicating
hole of a cast molded article and the audible sound waves which
passed through the communicating hole are received at the other end
thereof. The frequency spectrum of the received audible sound waves
are then computed and processed based on a reference frequency
spectrum, such that the quality of the communicating hole is
determined.
[0009] Also, a second aspect of the present invention is an
apparatus for inspecting a communicating hole of a cast molded
article, provided with an audible sound wave transmitter disposed
at one end of the communicating hole of a cast molded article, an
audible sound wave receiver disposed at the other end of the
communicating hole for receiving the audible sound waves sent from
the transmitter which has passed through the communicating hole,
and a computing and processing device for determining the quality
of the communicating hole by computing and processing the frequency
spectrum of the audible sound waves received by this receiver based
on a reference frequency spectrum.
[0010] Further, in the first and second aspects above, the audible
sound waves from the transmitter are able to be swept from a low
frequency to a high frequency or from a high frequency to a low
frequency. It is preferable to use audible sound waves of a
frequency of 1 to 20,000 Hz. A plurality of transmitters and/or
receivers may be provided.
[0011] Moreover, the above-mentioned computing and processing in
the first and second aspects enables the frequency spectrum of the
received audible sound waves to be computed and processed by a
neural network.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a block diagram illustrating a preferred
embodiment of the present invention.
[0013] FIG. 2 is a schematic view showing a communicating hole in a
good cylinder block.
[0014] FIG. 3 is a schematic view showing a communicating hole in a
bad cylinder block.
[0015] FIG. 4 is an explanatory view of a state in which a neural
network learns a good product.
[0016] FIG. 5 is an explanatory view of a state in which the neural
network learns a bad product with two defects in a communicating
hole.
[0017] FIG. 6 is an explanatory view of a state in which the neural
network learns a bad product with one defect in a communicating
hole.
[0018] FIG. 7 is an explanatory view of a state in which quality
can not be determined by the neural network.
[0019] FIG. 8 is a graph showing a frequency spectrum of a good
product.
[0020] FIG. 9 is a graph showing a frequency spectrum of a bad
product with two defects in a communicating hole.
[0021] FIG. 10 is a graph showing a frequency spectrum of a bad
product with one defect in a communicating hole.
[0022] FIG. 11 is a graph showing a frequency spectrum of another
bad product with one defect in a communicating hole.
[0023] FIG. 12 is a basic illustration of the neural network.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Next, preferred embodiments of the present invention will be
described in detail. In this embodiment, the cast molded article is
a cylinder head S, with water holes which are non-linear
communicating holes formed therein being the subject of
inspection.
[0025] FIG. 1 shows a configuration of the apparatus of the present
invention. As shown in this figure, a transmitter 1 such as a
speaker for transmitting audible sound waves is provided at an open
end of a communicating hole formed in one end of a cylinder head S
which is a cast molded article. Also, a receiver 3 such as a
microphone is provided at the other end of the opening in the
cylinder head S. The received audible sound waves are converted
into an electrical signal and amplified with an amplifier 4, after
which they are converted into a digital signal by means of an A/D
converter 5 and then input to a computing and processing device 6.
As shown in FIG. 1, EPROM and RAM are connected to this computing
and processing device 6. After being digitized via A/D conversion,
the audible sound waves are temporarily stored in RAM. A
calculation formula of the neural network, which will be mentioned
later, and "weights", operation algorithm, swept frequency data and
the like at each point of waveform of the frequency spectrum are
stored in EPROM.
[0026] The transmitter 1 is connected to an oscillation circuit 2,
which transmits audible sound waves of a frequency swept from 1 to
6,000 Hz, for example. The audible sound waves transmitted from one
of the openings of the communicating hole proceeds inside the
communicating hole, as shown in FIGS. 2 and 3, toward the other
opening of the communicating hole. Inside a non-linear
communicating hole, the audible sound waves reverberate, resonate,
or directly reach the other end of the opening. The audible sound
waves of the swept frequency are then received via a receiver 3
provided at the opening at the other end of the cylinder head S.
Audible sound waves of 1 to 20,000 Hz may also be used depending on
the diameter of the communicating hole. Note that FIG. 2 shows a
communicating hole of a good cylinder block and FIG. 3 shows a
communicating hole of a bad cylinder block.
[0027] In this embodiment, the frequency is swept such that audible
sound waves of 1 to 6,000 Hz go from a low frequency to a high
frequency. Conversely, the frequency may also be swept from high to
low such that the audible sound waves go from 6,000 to 1 Hz. A
plurality of open ends at one end of a cylinder head S may be
provided with a plurality of transmitters 1 from where swept
audible sound waves are transmitted. In this case, the swept
audible sound waves sent from each transmitter 1 are received by a
single receiver 3 provided at the opening at the other end of the
cylinder heads. They may be received by the receivers 3
corresponding to the number of transmitters 1 provided at the open
end at the other end of the cylinder head. This makes it possible
to improve detection accuracy. Furthermore, inspection may be
conducted with a plurality of transmitters 1 and receivers 3
disposed at branching passages or the like within the communicating
hole.
[0028] The receiver 3 detects the audible sound waves sent from the
transmitter 1 when they are propagated through the communicating
hole. Of the audible sound waves which have passed through the
communicating hole, there are those which have reached the opening
of the communicating hole directly, those which have reached the
opening of the communicating hole after reverberating repeatedly,
and those which have reached the opening of the communicating hole
after resonating therein. Accordingly, these sound waves contain
information about the communicating hole. It is thus possible to
know the state of the inside of the communicating hole by analyzing
these sound waves. In addition, if there is a large amount of noise
in the detected frequency spectrum, a filter can be used to
eliminate the noise and reshape the waveforms.
[0029] In this embodiment, the computing and processing device 6
computes and processes the frequency spectrum of the received
audible sound waves via a neural network so as to determine the
quality of the communicating hole. Quality determination by the
neural network is conducted via Back-Propagation
(Error-Back-Propagation Method) formed of an input layer 10, a
middle layer 11, and an output layer 12, as shown in the basic
illustration of FIG. 12. Note that the output layer 12 is formed of
an output layer 12a as a good product and an output layer 12b as a
bad product. Output layers 12a and 12b both output values from "0"
to "1" as their output values. With Back-Propagation learning is
conducted based on inspected good and bad cylinder heads S. With a
good cylinder head S, the output value from the output layer 12a as
a good product converges on a target value of "1". With a bad
cylinder head S, "weights" are obtained such that the output value
from the output layer 12b as a bad product converges on a target
value of "1". Therefore, these output values indicate the
probability of the inspected product being either good or bad. A
"1" for these output values corresponds to the inspected product
being either good or bad. It can therefore be determined that the
closer the output value of the output layer 12a as a good product
is to the target value of "1", the higher the probability that the
inspected product is good. And the closer the output value of the
output layer 12b as a bad product is to the target value of "1" the
higher the probability that the inspected product is bad.
[0030] That is, the above-mentioned "weights" are obtained through
the learning process of the neural network. In a good group of
inspected products, "weights" are learned and obtained such that
the output value from the output layer 12a as a good product
converges on the target value of "1". In a bad group of inspected
products (1), "weights" are learned and obtained such that the
output value from the output layer 12b as a bad product converges
on the target value of "1". At this time, with a bad product in
which the type of defect of the communicating hole differs from
that of the bad product group (1), a bad product group (2) of that
type learns and obtains "weights" such that the output value from
the output layer 12b as a bad product converges on the target value
of "1". That is, in inspecting for good and bad products, the
"weight" data at each point of the waveform of the frequency
spectrum becomes the reference frequency spectrum such that the
output layer 12a as a good product and the output layer 12b as a
bad product each converge on a target value of "1".
[0031] More specifically, with a good cast molded article, the
detected frequency spectrum will have two sizeable peaks, as shown
in FIG. 8. At this time the output layer 12a as a good product of
the neural network outputs a value close to the target value "1". A
cylinder head S1 group having this type of good product frequency
spectrum is learned, as shown in FIG. 4, and "weights" are
obtained. The frequency spectrum which has been "weighted" this
type of good product is used as a reference frequency spectrum.
Also, with a bad product having two defects, the detected frequency
spectrum will have no peaks, as shown in FIG. 9. At this time, the
output layer 12b as a bad product of the neural network outputs a
value close to the target value of "1". A cylinder head S2 group
having this type of bad product frequency spectrum is learned, as
shown in FIG. 5, and "weights" are obtained. The frequency spectrum
which has been "weighted" this type of bad product is used as a
reference frequency spectrum. Also, with the bad product groups S3
and S4 each having one defect, the detected frequency spectrums
become the spectrums shown in FIGS. 10 and 11, respectively. At
this time, the output layer 12b for a bad product of the neural
network outputs a value close to the target value of "1". Cylinder
head S3 and S4 groups having this type of bad product frequency
spectrums are learned, as shown in FIG. 6, respectively, and
"weights" are obtained. The frequency spectrum which has been
"weighted" this type of bad product is used as a reference
frequency spectrum.
[0032] In this way, an actual inspection is conducted with an
apparatus shown in FIG. 1 after the network learns the frequency
spectrum of a good product, the frequency spectrum of a bad product
having two defects, and the frequency spectrum of a bad product
having one defect and the like. The frequency spectrum shown in
FIG. 8 is that of an inspected product that is good. The frequency
spectrum shown in FIG. 9 is that of an inspected product that is
bad with two obstructions. The frequency spectrum shown in FIG. 10
is that of an inspected product that is bad with one obstruction.
The frequency spectrum shown in FIG. 11 is that of a bad product
with one obstruction, which differs from the frequency spectrum of
the bad product shown in FIG. 10. Determining the quality of these
with the neural network enables the deviation to be acceptable,
making it possible to improve inspection accuracy and speed.
Determining quality in this way, then, a cylinder head S that was
determined to be good is shipped to the next process as a good
product, while a cylinder head S that was determined to be bad is
eliminated from the process as a bad product.
[0033] However, there are cases in which an output value is output
for a cylinder head S cast in large quantity which is neither for a
good product nor a bad product. For example, assuming that the
output value at the output layer 12a as a good product is 0.3, and
the output value at the output stage 12b as a bad product is 0.23,
it is difficult to determine whether the inspected product is good
or bad from those values. In a case such as this, an operator will
determine the inspected product to be a "questionable product" (see
FIG. 7). Further, cylinder heads S at high and low temperatures,
depending on the air temperature, are mixed together in the casting
line. This variation of temperature causes the frequency
characteristics to move in the frequency direction (along the
horizontal axis in FIGS. 8 through 11). Therefore at this time, a
cross-correlation function is obtained by means of the computing
and processing device 6 and corrections are made, or the
temperature of the cylinder head S is measured and corrections are
done via the computing and processing device 6.
[0034] Note that in the above-mentioned preferred embodiment, the
neural network is used to determine quality such that the speed and
accuracy of the quality determination is improved. However, when
accuracy and speed are not required, the quality may of course also
be determined based on the peak value of the frequency spectrum
with a computing and processing device, without using a neural
network. Also, in the preferred embodiment, the audible sound waves
are swept from 1 Hz to 6,000 Hz in accordance with the diameter of
the communicating hole to be inspected. However, measurements may
of course also be taken sweeping the audible sound waves from 1 Hz
to 2,000 Hz, depending on the diameter of the communicating hole.
Moreover, in the preferred embodiment the frequency is swept from
low to high. Conversely it may also be swept from high to low. Also
in the preferred embodiment, a single transmitter 1 and a single
receiver 3 are provided, but a plurality of transmitters 1 and
receivers 3 may also be provided, such that audible sound waves
from a single transmitter 1 are received by a plurality of
receivers 3 or audible sound waves from a plurality of transmitters
1 are combined and the resulting composite sweeping waveform is
transmitted and then received by one or a plurality of receivers 3.
Accordingly information regarding corners and complex flow passages
and micro-pores and the like of the communicating hole is able to
be obtained, improving the inspection accuracy even more. In
addition, in the above-mentioned preferred embodiment, the
transmitter 1 and the receiver 3 were disposed at both ends of the
cylinder head S. A local inspection may of course also be conducted
by disposing the transmitter 1 and the receiver 3 suitably within a
communicating hole.
[0035] The present invention has various advantages such as that it
enables an inspection to be conducted using sound waves which was
difficult in the past, by emitting audible sound waves from one end
of a communicating hole, receiving the audible sound waves which
passed through the communicating hole, computing and processing the
frequency spectrum of the audible sound waves based on a reference
frequency spectrum, and determining the quality of the
communicating hole. Further, because audible sound waves, which
expand as opposed to ultrasound, are transmitted, it is possible to
inspect a wide region of the communicating hole. Also, sweeping the
frequency enables an accurate inspection to be conducted even with
communicating holes having different size hole diameters, and
setting a frequency of the audible sound waves to the value from 1
to 20,000 Hz enables the inspection to be done on products having
holes with diameters of various sizes. Moreover, determining the
quality with the neural network improves inspection speed as well
as enhances the inspection accuracy, and determination is able to
be facilitated and inspection efficiency improved by deeming a
product which has a low probability when matched with the target
value of good product bad. Furthermore, providing a plurality of
transmitters enables a variety of combinations of sweeping
waveforms to be created. Accordingly, information is able to be
obtained regarding corners and complex portions or narrow portions
and the like of a communicating hole which are in separate
locations, thereby improving measurement accuracy. Moreover,
providing a plurality of receivers increases the amount of
information able to be obtained, therefore improving the
reliability of quality determination.
* * * * *