Method of and system for electrically processing vacuum pressure information suitable for use in vacuum unit

A method of and a system for electrically processing vacuum pressure information, which is suitable for use in a vacuum unit. Pressure values are detected and a desired pressure value lower than the highest vacuum pressure value of the detected pressure values is displayed on a displaying device in digital form. The desired pressure value is stored in a storing device. Each of pressure values relative to vacuum, which are detected by a pressure detecting element held in front of a passage communicating with a vacuum port, is converted into a digital signal. The so-converted digital signal is digitally displayed on the displaying device. The desired pressure value stored in the storing device is compared with each of the detected pressure values relative to the vacuum, and information about faulty points is displayed on the displaying device based on the result of comparison.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method of and a system for electrically 
processing vacuum pressure information, which is suitable for use in a 
vacuum unit. 
2. Description of the Related Art 
A vacuum unit is used in a state in which it has been coupled to a suction 
pad or cup for attracting a work and feeding the same, for example. In 
this case, a pressure switch is disposed in the vacuum unit and detected 
pressure values is then compared with a preset pressure value to thereby 
determine whether or not the work has been attracted by the suction cup. 
There is also known a vacuum unit of a type wherein a failure in the 
operation of the vacuum unit is detected to thereby produce a failure 
signal and visually display the same. 
In this type of vacuum unit, however, the reason that a desired vacuum 
pressure value cannot be obtained can be based on various factors. For 
example, it is realized that even mere clogging due to dust or the like 
included in a fluid tends to be developed in a directional control valve, 
an ejector, a filter or a silencer or the like. It is thus difficult to 
specify failure or faulty points and quickly replace parts with others so 
as to restart the vacuum unit even if a failure signal is produced. 
SUMMARY OF THE INVENTION 
It is a general object of the present invention to provide a method of and 
a system for electrically processing vacuum pressure information, which is 
employed in a vacuum unit, wherein a desired pressure value can be set in 
a relatively simple manner and failure points can be visually displayed. 
It is a principal object of the present invention to provide a method of 
and a system for electrically processing vacuum pressure information, 
which is employed in a vacuum unit, wherein failure points in the vacuum 
unit can be promptly specified and hence parts can be easily replaced by 
others. 
It is another object of the present invention to provide a method of 
electrically processing vacuum pressure information, which is suitable for 
use in a vacuum unit, the method being executed by a vacuum control 
apparatus and comprising the steps of detecting pressure values, 
displaying a desired pressure value lower than the highest vacuum pressure 
value of the detected pressure values on displaying means in digital form, 
storing the desired pressure value in storing means, converting each of 
pressure values relative to vacuum into a digital signal, the pressure 
values being detected by a pressure detecting element held in front of a 
passage which communicates with a vacuum port, and thereafter digitally 
displaying the so-converted digital signal on the displaying means, 
comparing the desired pressure value stored in the storing means with each 
of the detected pressure values relative to the vacuum, and displaying 
information about failure points on the displaying means based on the 
result of comparison. 
It is a further object of the present invention to provide a method of 
electrically processing vacuum pressure information wherein the desired 
pressure value stored in the storing means comprises a first pressure 
value lower than the highest vacuum pressure value, which has been 
determined from the detected pressure values and a second pressure value 
lower than the first pressure value, and a predetermined pressure width 
for avoiding chattering action is specified by the first and second 
pressure values. 
It is a still further object of the present invention to provide a method 
of electrically processing vacuum pressure information wherein when each 
of the detected pressure values relative to the vacuum is lower than the 
desired pressure value plural times in succession upon comparison of the 
desired pressure value stored in the storing means with each of the 
detected pressure values relative to the vacuum, a failure-point 
indicating signal is produced as a predetermined signal. 
It is a still further object of the present invention to provide a system 
for electrically processing vacuum pressure information, which is suitable 
for use in a vacuum unit activated to cause components such as a valve 
body, an ejector, a silencer, a filter, etc. to communicate with one 
another through a predetermined passage, the system comprising setting 
means for setting a desired pressure value, a pressure sensor disposed on 
either one of the upstream and downstream sides of at least one of the 
components, determining means for comparing a pressure value produced from 
the pressure sensor with the set desired pressure value to thereby 
determine that the vacuum unit has been brought to an improper state when 
the result of comparison shows a predetermined pressure value, and 
displaying means for displaying information about failure points thereon 
based on the result of comparison by the determining means. 
It is a still further object of the present invention to provide a system 
for electrically processing vacuum pressure information wherein pressure 
sensors are provided on a fluid supply side corresponding to the upstream 
side of the ejector of the components and a fluid inlet side corresponding 
to the downstream side of the ejector respectively. 
It is a still further object of the present invention to provide a system 
for electrically processing vacuum pressure information wherein the 
setting means is capable of setting the flow rate of air and a flow-meter 
is provided on the fluid inlet side corresponding to the downstream side 
of the ejector. 
It is a still further object of the present invention to provide a system 
for electrically processing vacuum pressure information wherein the 
determining means includes means for counting the number of pressure 
values lower in vacuum than the set pressure value and for producing a 
signal indicative of an improper state when the counted number of the 
pressure values has reached a predetermined value. 
It is a still further object of the present invention to provide a system 
for electrically processing vacuum pressure information, further including 
displaying means for digitally displaying a vacuum pressure value detected 
by a detecting means for detecting the vacuum pressure value. 
It is a still further object of the present invention to provide a system 
for electrically processing vacuum pressure information, further including 
displaying means for digitally displaying at least a pressure value used 
for the determination of the improper state and a pressure value used for 
the failure precognition. 
The above and other objects, features and advantages of the present 
invention will become apparent from the following description and the 
appended claims, taken in conjunction with the accompanying drawings in 
which preferred embodiments of the present invention are shown by way of 
illustrative example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A vacuum pressure information processing apparatus or system incorporated 
in a vacuum unit according to the present invention will hereinafter be 
described in detail with reference to the accompanying drawings in which 
preferred embodiments are shown by way of illustrative example in 
connection with a method of processing vacuum pressure information. 
A vacuum pressure information processing system 10 incorporated in a vacuum 
unit according to the present invention will first be described with 
reference to FIG. 1. 
In FIG. 1, reference symbol W indicates a work and reference numeral 12 
indicates a suction pad or cup (hereinafter called a "work suction cup") 
used to feed the work, which is mounted on a delivering means employed in 
a vacuum system. The pressure information processing system 10 comprises a 
semiconductor pressure sensor 16 for detecting the value of pressurized 
air Ap so as to output a detected signal therefrom, a constant-current 
circuit 18 and an amplifier 20. Further, the pressure information 
processing system 10 also includes an A/D converter 22 for converting a 
signal outputted from the amplifier 20, i.e., an analog signal 
corresponding to the value of the pressurized air Ap into a digital 
detection signal S.sub.2, and a controller 30 comprised of a one-chip 
microcomputer or the like. The controller 30 is provided with a one-chip 
multi CPU 30a having superb high performance, a ROM 30b with a program 
stored therein, and an I/O 30c or the like, and includes set-value up/down 
switches S.sub.W1, S.sub.W2 each used to set a pressure value as 
reference, a set switch S.sub.W3 for setting a pressure value at the time 
that the set value has been changed, and a reset switch S.sub.W4 for 
resetting the set value, all of which are electrically connected to the 
controller 30. Also connected to the controller 30 are an EE(E.sup.2)PROM 
32 capable of storing information therein and retaining the information 
therein when a power source is turned off, and an LCD driver 34 and an LCD 
38 which are used to visually display set values and information. 
The vacuum unit incorporating the pressure information processing system 
constructed as described above therein will now be shown in FIGS. 2 and 3. 
Referring first to FIG. 2, reference numeral 50 indicates the vacuum unit. 
The vacuum unit 50 basically comprises a valve block 52, an ejector 54, a 
filter block 56, a control block 58 and a monitor 60. The blocks 52, 56, 
58 and the ejector 54 are integrally formed by either a diecast or a 
plastic. The valve block 52 has an unillustrated poppet valve disposed 
therein for feeding compressed air to the ejector 54 and blocking the 
same, and first and second pilot-operated electromagnetic valves. The 
first and second pilot-operated electromagnetic valves are of 
pilot-operated electromagnetic valves used for a compressed-air feed valve 
62 and a vacuum break valve 64 respectively, each of which is of a 
normally-closed type. Each of the first and second pilot-operated 
electromagnetic valves may be constructed as a normally open type valve or 
a valve with a detent in order to prevent the work W from falling upon 
power failure. 
The filter block 56 is provided adjacent to the valve block 52. The filter 
block 56 has an air feed port 66 defined therein, which communicates with 
a compressed-air feed source 65 and an air inlet port 68 defined therein, 
which communicates with the work suction cup 12. Further, the filter block 
56 has a filter 70 and a silencer 72 both disposed therein and passages 
defined therein, which are used to cause the ejector 54 and the valve 
block 52 to communicate with the filter 70 and the silencer 72. There are 
defined in predetermined positions of the passages, a plurality of holes, 
and provided thereat pressure sensors 74, 76, 78, 80, 82, a pressure 
switch 84 and a flowmeter 86 in a connected state, which are constructed 
so as to have the pressure information processing system 10 shown in FIG. 
1 built-in (see FIG. 3). The flowmeter 86 may be a type in which an 
information processing circuit is incorporated in a known mass flowmeter. 
Alternatively, the flowmeter 86 may be used as a differential pressure 
type flowmeter for measuring the flow rate in accordance with the 
measurement of pressure. 
The ejector 54 is disposed adjacent to the filter block 56. The silencer 72 
is disposed in the side face of the ejector 54 and serves to silence sound 
produced by pressurized air fed from the ejector 54. 
The control block 58 includes therein the A/D converter 22 for receiving a 
signal sent from the semiconductor pressure sensor 16 (including a 
differential pressure type sensor and a capacity type sensor, for example) 
comprised of a piezo or the like, the controller 30, the E.sup.2 PROM 32, 
etc. The control block 58 detects the pressure and the flow rate at each 
of the positions where the pressure sensors 74, 76, 78, 80, 82, the 
pressure switch 84 and the flowmeter 86 have been disposed, in accordance 
with signals supplied from the pressure sensors 74, 76, 78, 80, 82, the 
pressure switch 84 and the flowmeter 86, and compares the pressure and 
flow rate thus detected with a preset value so as to produce a failure 
precognition signal S.sub.4. The failure precognition signal S.sub.4 
enables a failure in, for example, the ejector or the like to be digitally 
displayed by way of, for example, an English character or other character. 
It is needless to say that the valve block 52, the ejector 54 and the 
filter block 56 are constructed in such a manner that pressurized fluids 
can flow through internal passages. An electrically-connecting block 90 is 
disposed between the valve block 52 and both the control block 58 and the 
monitor 60. 
The vacuum unit 50 may be provided in continuation by a manifold. In the 
vacuum unit 50 as well, a serial transmitting means, a wireless means and 
a LAN means can be used so as to enable an attendant control signal for 
the diagnosis of failure and information other than the signals from the 
valves and the switches to be transmitted or received to and from the 
external device and other control devices near the vacuum unit 50 and to 
enable mutual control with respect to the external device and other 
control devices. These controllers, i.e., the above respective means may 
be dispersively disposed in a CPU of a sensor. Alternatively, each of them 
may be disposed in a suitable position in the manifold. These controllers 
can carry out operations such as timer control for and setting of the 
valves and switches, etc. in unitary form. 
In the vacuum unit 50 constructed as described above, when an operation 
start instruction signal is first input, compressed air is introduced from 
the compressed-air feed source 65 through the air feed port 66 so as to 
produce a vacuum in the ejector 54. The vacuum thus produced brings the 
work suction cup 12 connected to the air inlet port 68 of the filter block 
56 to the negative pressure, i.e., vacuum. Thus, the work suction cup 12 
attracts and holds the work W in accordance with the operation of a 
conveying means such as a robot. Then, the work suction cup 12 is 
inactivated to release the work W. As a result, the pressure (vacuum) 
successively applied to the pressure sensor disposed in the vacuum unit 
50, e.g., the semiconductor pressure sensor 16 in the pressure sensor 80 
for detecting air suction pressure (vacuum pressure) of the ejector 54, is 
represented in the form of pressure values sequentially varied as 
illustrated in FIG. 4, i.e., P.sub.O1, P.sub.O2, P.sub.O3, . . . , 
P.sub.ON+1. As is easily understood from the drawing at this time, there 
is often a situation in which the highest vacuum pressure value (degree of 
vacuum) is reduced with the elapse of time owing to leakage of the vacuum 
pressure from the work suction cup 12 side and clogging of the filter, for 
example. A signal corresponding to each of the pressure changes or values 
P.sub.O1, P.sub.O2, P.sub.O3, . . . , P.sub.ON+1 is supplied via the 
semiconductor pressure sensor 16 and the amplifier 20 to the A/D converter 
22 where it is converted into a digital detection signal S.sub.2, which 
is, in turn, input to the controller 30. 
In the controller 30, the maximum value (P.sub.max) of the pressure change 
P.sub.O1 first specifies a first address of the E.sup.2 PROM 32 and is 
stored thereat. 
Then, the switch S.sub.W3 is turned ON to compute threshold values 
PH.sub.1a, PH.sub.1b for providing a differential pressure A therebetween, 
which are stored in the E.sup.2 PROM 32. At this case, a second address of 
the E.sup.2 PROM 32 is specified and 70% (threshold value PH.sub.1a) of 
the maximum value (P.sub.max) is computed and stored at the specified 
second address. Then, a third address of the E.sup.2 PROM 32 is specified 
and 65% (threshold value PH.sub.1b) of the maximum value (P.sub.max) is 
computed and stored at the specified third address. 
Now, a pressure switch signal S.sub.6, which appears depending on the 
pressure changes P.sub.O1 through P.sub.ON+1 is continuously produced in 
association with the threshold values PH.sub.1a, PH.sub.1b. The pressure 
switch signal S.sub.6 is used for full-closed control of various control 
driving means such as a delivering device and for information processing 
in an FMS, a CIM, etc. Further, an assembling machine and a processing 
machine or the like can be brought to a high level. 
Then, a fourth address of the E.sup.2 PROM 32 is specified and 80% 
(threshold value Ph) of the maximum value (P.sub.max) is computed and 
stored at the specified fourth address. 
The threshold value Ph represents a point reduced by 20% of the normal 
highest vacuum pressure value, i.e., the maximum value (P.sub.max, the 
maximum degree of vacuum) of the pressure change P.sub.O1. Pressure values 
below the threshold value Ph are regarded as being unwanted or improper 
pressure states. 
Then, the improper pressure values or changes below the threshold value Ph 
corresponding to the failure precognition determining vacuum, i.e., the 
pressure changes P.sub.O2 through P.sub.ON+1 (each corresponding to the 
digital detection signal S.sub.2 as a signal, for example) of the pressure 
changes P.sub.O1 through P.sub.ON+1 are cumulatively stored six times. 
When the improper pressure values thus stored have coincided with improper 
set values counted six times, which have been previously set by the 
switches S.sub.W1, S.sub.W2 and S.sub.W3, the failure precognition signal 
S.sub.4 is continuously produced. 
A process for producing the failure precognition signal S.sub.4, for 
example, is carried out by executing the program of the controller 30. In 
addition, information on such a process is stored in the E.sup.2 PROM 32. 
When the controller 30 is activated again after the power source has been 
turned off, the failure precognition signal S.sub.4 is produced based on 
the operation state of the controller 30, thereby making it possible to 
read the information again from the E.sup.2 PROM 32. 
As described above, the pressure information processing system 10 
automatically and accurately sets the threshold values PH.sub.1a, 
PH.sub.1b and Ph with respect to the maximum value (P.sub.max) of the 
pressure change P.sub.O1 and hence self-diagnoses whether or not a failure 
in the operation of the vacuum unit 50 has occurred. 
Incidentally, 70%, 65% and 80%, which are of the threshold values of 
PH.sub.1a, PH.sub.1b and Ph, can be changed. These changed values are 
cleared by turning ON the reset switch S.sub.W4. Afterwards, the up/down 
switches S.sub.W1, S.sub.W2 may be turned ON to set these values using the 
switch S.sub.W3 after a change in the numerical value based on a 5% step 
has been made, for example. 
Incidentally, in the above-described embodiment, the threshold values 
PH.sub.1a, PH.sub.1b and the threshold value Ph are digitally set with 
respect to the maximum value (P.sub.max) of the pressure change P.sub.O1. 
However, as an alternative, a pressure curve indicative of the pressure 
change P.sub.O1 is stored as data and the threshold values PH.sub.1a, 
PH.sub.1b and Ph can also be set in the same manner as described above. 
On the other hand, the above threshold values can also be set in the 
following manner. First of all, the work W is attracted in advance. At 
this time, the pressure sensors 76, 80 detect pressure P.sub.S for feeding 
the compressed air to the ejector 54 and vacuum pressure P.sub.V generated 
from the ejector 54, respectively. A curve (80% line in FIG. 5) in which 
the value of the vacuum pressure P.sub.V is 80%, is set with respect to a 
P.sub.S -P.sub.V curve obtained from the pressure P.sub.S and the vacuum 
pressure P.sub.V. After such a curve setting has been completed, the 
vacuum unit 50 is actually operated to cause the pressure sensors 76, 80 
to detect the feed pressure P.sub.S and the vacuum pressure P.sub.V 
respectively. When the detected feed pressure P.sub.S and vacuum pressure 
P.sub.V do not fall within a range (indicated by oblique lines in FIG. 5) 
between the P.sub.S -P.sub.V curve and the 80% line, the failure 
precognition signal S.sub.4 is produced from the controller 30. 
Furthermore, the threshold values may also be set in the following manner. 
First of all, the pressure sensor 80 and the flowmeter 86 detect in 
advance vacuum pressure P.sub.V produced from the ejector 54, which 
corresponds to the pressure P.sub.S for feeding given air to the ejector 
54, and an inlet or suction flow rate Q of the ejector 54, respectively. 
Then, a threshold-value straight line is set with respect to a Q-P.sub.V 
straight line determined from the detected vacuum pressure P.sub.V and the 
suction flow rate Q as shown in FIG. 6. When the vacuum pressure P.sub.V 
and the suction flow rate Q do not fall within a range indicated by 
oblique lines, the failure precognition signal S.sub.4 is produced. 
Thus, when it is recognized that the vacuum unit 50 fails to operate in the 
normal manner, the controller 30 is activated to cause the pressure 
sensors 74, 76, 78, 80, 82 to detect pressure values respectively and to 
calculate the differences in pressure between the respective pressure 
values thus detected. It is thus possible to specify any one which causes 
a failure in operation from the air feed valve 62, the vacuum break valve 
64, the ejector 54, the silencer 72, the filter 70 and the work suction 
cup 12 depending on variations in both the pressure values and the 
differential pressure. For example, when the difference between the 
pressure detected by the pressure sensor 80 disposed on the upstream side 
and the pressure detected by the pressure sensor 82 disposed on the 
downstream side, i.e., the differential pressure exceeds a predetermined 
threshold value, a "failure in the filter" signal is displayed on the 
monitor 60 by using the LCD 38. 
Thus, the controller 30 can automatically recognize a failure in the 
operation of the vacuum unit 50 because the pressure sensors 74, 76, 78, 
80, 82 and the flowmeter 86 are placed in suitable positions in the vacuum 
unit 50. At the same time, the pressure sensors 74, 76, 78, 80, 82 can 
specify failure points or positions of the air feed valve 62, the ejector 
54, the filter 70, etc. 
Other embodiments showing vacuum pressure information processing systems of 
the present invention will hereinafter be described with reference to 
FIGS. 7 through 12. 
Referring now to FIGS. 7 and 8, reference numeral 150 indicates a vacuum 
control apparatus. The vacuum control apparatus 150 basically comprises a 
valve block 152, an ejector 154, a detecting unit 156, a filter 158 and a 
connecting member 160. The valve block 152 has air inlet ports 162, 164, 
166 defined therein, a poppet valve 153 disposed therein for feeding 
compressed air to the ejector 154 and blocking the same, and first and 
second electromagnetic valves 168, 170 mounted on the upper surface 
thereof. The first electromagnetic valve 168 is used as a compressed-air 
feed valve, whereas the second electromagnetic valve 170 is used as an 
electromagnetic valve for the vacuum break. In order to supply electric 
power and a control signal such as an ON/OFF signal to the outside via 
unillustrated conductors, the first and second electromagnetic valves 168 
and 170 are provided with first and second connectors 168a, 170a 
respectively. The ejector 154 is provided adjacent to the valve block 152. 
In addition, the ejector 154 has a nozzle 155 and a diffuser 157 both 
disposed therein and a silencer 172 mounted on the upper surface thereof. 
The silencer 172 serves to silence sound generated by pressurized air 
produced from the diffuser 157 of the ejector 154. The detecting unit 156 
detects pressure under vacuum and includes the semiconductor pressure 
sensor 16 disposed therein. The detecting unit 156 also includes, on the 
upper surface thereof, a connector 174, a digital display unit 176, a 
set-value up switch S.sub.W1, a set-value down switch S.sub.W2, a set 
switch S.sub.W3, a reset switch S.sub.W4, and display units 178, 180. The 
digital display unit 176 can carry out visual representation of "failure" 
or "break down", etc. in either English or other language, for example. 
The filter 158 has a main body 161 disposed therein, which includes a 
hydrophobic material and serves to prevent water or moisture from entering 
therein. In addition, the filter 158 is detachably mounted on the 
connecting member 160 by a control 182. It is needless to say that each of 
the valve block 152, the ejector 154, the silencer 172, the detecting unit 
156 and the filter 158 is in a communication state in such a manner that 
pressurized fluids can flow through each of internal passages. In 
particular, there are disposed in the detecting unit 156, the 
semiconductor pressure sensor 16 (including a differential pressure type 
sensor or a capacity type sensor, for example) comprised of a piezo or the 
like, the constant-current circuit 18, the amplifier 20, the A/D converter 
22, the controller 30, the EE(E.sup.2)PROM 32, the LCD driver 34, etc. as 
already described in FIG. 1. The connector 174 can be 
electrically-connected with conductors to produce the failure precognition 
signal S.sub.4 and the pressure switch signal S.sub.6 shown in FIG. 1. The 
connector 174 can also be connected with a power source relative to the 
detecting unit 156, and a control signal line or conductor. In addition, 
the connector 174 can provide a communication function for another vacuum 
control apparatus, an external control apparatus, etc. so as to supply 
pressure detection information or control information therefrom. 
In the vacuum control apparatus constructed as described above, when an 
operation start instruction signal is first input, pressurized air is 
introduced from the air inlet port 166 so as to produce a vacuum in the 
ejector 154. At this case, the air feed ports 162, 164 have been sealed 
with blank caps respectively. The so-produced vacuum brings the work 
suction cup 12 coupled to an unillustrated port of the connecting member 
160 to the negative pressure, i.e., vacuum. Thus, the work suction cup 12 
attracts and holds the work W in accordance with the operation of a 
conveying means such as a robot. Then, the work suction cup 12 is 
inactivated to release the work W. As a result, the pressure (vacuum) 
successively applied to the semiconductor pressure sensor 16 in the 
detecting unit 156 is represented in the form of pressure values 
sequentially varied as illustrated in FIG. 10, i.e., P.sub.O1, P.sub.O2, 
P.sub.O3, . . . , P.sub.ON+1. As is easily understood from the drawing at 
this time, there is often a case in which the highest vacuum pressure 
value (degree of vacuum) is reduced with the elapse of time owing to 
leakage of the vacuum pressure from the work suction cup 12 side and 
clogging of the filter 158, for example. 
A signal corresponding to each of the pressure values P.sub.O1, P.sub.O2, 
P.sub.O3, . . . , P.sub.ON+1 is supplied via the semiconductor pressure 
sensor 16 and the amplifier 20 to the A/D converter 22 where it is 
converted into a digital detection signal S.sub.2, which is, in turn, 
input to the controller 30. 
The controller 30 has a program stored therein, which will be described 
later. Firstly, peak-held values of the pressure values P.sub.O1, 
P.sub.O2, P.sub.O3, . . . , P.sub.ON+1 under a predetermined mode specify 
a first address of the EE(E.sup.2)PROM 32 and are stored thereat. The 
values referred to above are successively displayed on the LCD 38 of the 
digital display unit 176 together with the previous respective values. 
Then, the mode is shifted from the predetermined mode to a second mode and 
the threshold value for producing the pressure switch signal S.sub.6 
relative to each of the pressure values P.sub.O1, P.sub.O2, P.sub.O3, . . 
. , P.sub.ON+1, i.e., a so-called differential pressure PH.sub.1, is set 
by the switches S.sub.W1 through S.sub.W4 under this second mode. 
Thereafter, the second mode is further changed to a third mode so as to 
set a failure precognition determining vacuum Ph which defines a point 
reduced by, for example, 20% of the normal highest vacuum pressure value 
(maximum degree of vacuum) as a pressure value for making a failure 
precognition judgment. Then, the vacuum thus set specifies a third address 
and is stored thereat in the EE(E.sup.2)PROM 32. An arithmetical operation 
on the differential pressure PH.sub.1 is performed and the result of its 
operation may be stored in the EE(E.sup.2)PROM 32 as a value reduced by 
several percent to several tens percent from the maximum value (P.sub.max) 
of the pressure change P.sub.O1. 
Further, unwanted or improper pressure values below the failure 
precognition determining vacuum Ph among the pressure values P.sub.O1, 
P.sub.O2, P.sub.O3, . . . , P.sub.ON+1 are set up (counted for setting) 
six times, for example. Such set values or the like are visually displayed 
on the LCD 38. 
After the above pressure-value setting process has been completed, the 
pressure switch signal S.sub.6 corresponding to the differential pressure 
PH.sub.1 with respect to each of the pressure values P.sub.O1, P.sub.O2, 
P.sub.O3, . . . , P.sub.ON+1 or information about the differential 
pressure P.sub.H1 is continuously produced in such a manner as to be used 
for full-closed control of each of various control driving means such as a 
delivering means and for information processing in an FMS, a CIM, etc. 
On the other hand, unwanted or improper vacuum-value data Pd (corresponding 
to the digital detection signal S.sub.2 as a signal, for example) below 
the Ph among the pressure values P.sub.O1, P.sub.O2, P.sub.O3, . . . , 
P.sub.ON+1 is continuously produced six times. That is, when the count of 
the improper vacuum-value data Pd is performed six times, the failure 
precognition signal S.sub.4 is continuously produced. 
At this time, information about the production of the failure precognition 
signal S.sub.4 or the like is stored in the EE(E.sup.2)PROM 32 and the 
information can be read again from the EE(E.sup.2)PROM 32 when the 
controller 30 is activated again after the power source has been turned 
off. 
The sequential control of the controller 30 for producing the failure 
precognition signal S.sub.4 based on the program stored in the ROM 30b 
will now be described below. 
The present program is executed in such a manner that the controller 30 
starts its operation in response to the input of the operation start 
instruction signal for the entire apparatus to the controller 30 (see 
FIGS. 11 and 12). 
1) A process for taking in the failure precognition signal S.sub.4 is 
executed in Step 101 (see FIGS. 11 and 12). 
2) A process for determining whether or not the failure precognition signal 
S.sub.4 has been produced is executed in Step 102. If the answer is 
determined to be YES, then the routine procedure proceeds to Step 103. If 
the answer is determined to be NO, then the routine procedure proceeds to 
Step 105. 
3) A process for determining whether or not an ON signal has been produced 
when the switch S.sub.W4 is turned on is executed in Step 103. If the 
answer is determined to be NO, then the routine procedure is returned to 
Step 103. If the answer is determined to be YES, then the routine 
procedure proceeds to the next Step 104. 
4) A process for stopping the delivery of the failure precognition signal 
S.sub.4 from the controller 30 is executed in Step 104. 
A process for stopping the delivery of the failure precognition signal 
S.sub.4 continuously produced till now in Steps 101 through 104 from the 
controller 30 is executed. 
5) A process for allowing the controller 30 to take in the digital 
detection signal S.sub.2 is executed in Step 105. 
6) A process for determining whether or not the pressure switch signal 
S.sub.6 has been produced is executed in Step 106. If the answer is 
determined to be YES, then the routine procedure proceeds to the next Step 
107. If the answer is determined to be NO, then the routine procedure 
proceeds to Step 110. 
7) A process for bringing a flag .sub.SON F to 1 when the pressure switch 
signal S.sub.6 is in an ON state, is executed in Step 107. If the pressure 
switch signal S.sub.6 is in an OFF state, then the flag .sub.SON F is 
brought to 0, and hence the flag .sub.SON F is down (reset). 
8) A process for determining whether or not the vacuum-value data Pd (the 
highest vacuum pressure value of the digital detection signal S.sub.2) is 
greater than the failure precognition determining vacuum Ph (i.e., Pd&gt;Ph) 
is executed in Step 108. If the answer is determined to be NO, it is then 
determined that the vacuum-value data Pd is normal, and hence the routine 
procedure proceeds to "RETURN". If the answer is determined to be YES, 
then the routine procedure proceeds to the next Step 109. 
9) A process for bringing a flag .sub.ED F to 1 when the vacuum-value data 
Pd exceeds the failure precognition determining vacuum Ph at the time that 
the pressure switch signal S.sub.6 is in the ON state, is executed in Step 
109. Thereafter, the routine procedure proceeds to "RETURN". 
10) If the answer is determined to be NO in Step 106, then a process for 
determining whether or not the flag .sub.SON F has been brought to 1 is 
executed in Step 110. If the answer is determined to be NO, then the 
routine procedure proceeds to "RETURN". If the answer is determined to be 
YES, then the routine procedure proceeds to the next Step 111. 
11) A process for determining whether or not the flag .sub.ED F has been 
brought to 1 is executed in Step 111. If the answer is determined to be 
YES, then the routine procedure proceeds to Step 115. If the answer is 
determined to be NO, then the routine procedure proceeds to the next Step 
112. 
12) A process for performing an increment in the unwanted or improper count 
(six times) is executed in Step 112. 
13) A process for comparing each of values obtained by performing the 
increment in the improper count (six times) with each of set counts (six 
times) so as to determine based on the result of comparison whether or not 
they coincide with each other, is executed in Step 113. If the answer is 
determined to be YES, then the routine procedure proceeds to the next Step 
114. If the answer is determined to be NO, then the routine procedure 
proceeds to Step 116. 
14) A process for delivering the failure precognition signal S.sub.4 from 
the controller provided that each incremented value (six times) in Step 
113 is regarded as each set count (six times), is executed in Step 114. 
Thereafter, the routine procedure proceeds to "RETURN" to start the next 
determining process. 
15) If the answer is determined to be YES in Step 106, i.e., if the 
vacuum-value data Pd exceeds the failure precognition determining vacuum 
Ph in the ON state of the pressure switch signal S.sub.6, then a process 
for bringing its undesired result to a normal state so as to clear the 
unwanted or improper count is executed in Step 115. 
16) A process for bringing the flag .sub.ED F to 0 is executed in Step 116, 
followed by proceeding to the next Step 117. 
17) A process for bringing the flag .sub.SON F to 0 is executed in Step 
117. Thereafter, the routine procedure proceeds to "RETURN" to start the 
next determining process again. 
Thus, when the improper count with respect to the failure precognition 
determining vacuum Ph coincides with the preset number of times, i.e., the 
preset count at the time that the highest vacuum pressure value is lowered 
with the elapse of time by repeatedly performing a process for delivering 
the work W, for example, the failure precognition signal S.sub.4 is 
produced so as to previously provide effective information about the time 
when devices such as the filter, the ejector, etc. should be replaced by 
new ones due to the clogging of the filter 158, the deterioration in 
performance of the ejector, etc. In addition to the supply of such 
effective information, the pressure values such as the failure 
precognition determining vacuum Ph, the differential pressure PH.sub.1, 
etc. can be accurately and easily set up and distinctly displayed together 
with the present pressure value. 
In the illustrated embodiment, the number of times n (unwanted or improper 
count) in which the vacuum-value data cannot reach the failure 
precognition determining vacuum Ph and the preset number of times N (set 
count) are six times in succession. In addition, the failure precognition 
signal S.sub.4 is produced, that is, the failure precognition signal 
S.sub.4 indicative of the pressure value disabling the normal work 
delivering process or the like is produced to provide information about a 
pre-judgment. 
A criterion for such a previous judgment can be changed depending on the 
construction and the operational state of the delivering means. Thus, such 
a criterion is applied to, for example, a case in which a more effective 
and experimental value, e.g., vacuum-value data Pd produced one time 
cannot reach the failure precognition determining vacuum Ph, a case in 
which the rate at which the vacuum-value data Pd cannot reach the failure 
precognition determining vacuum Ph within a predetermined number of times, 
exceeds a predetermined value, and a case in which the rate at which the 
vacuum-value data Pd cannot reach the failure precognition determining 
vacuum Ph during a predetermined period of time, exceeds a given value. In 
this case, a program based on the above criterion may be executed so as to 
produce the failure precognition signal S.sub.4 in a manner similar to the 
aforementioned embodiment. 
FIG. 9 shows an embodiment different from the embodiment illustrative of 
the vacuum control apparatus 150 of FIG. 8 in which the ejector has been 
incorporated. This embodiment is constructed such that a vacuum pump (not 
shown) as an alternative to the ejector 154 is coupled to a port 166. 
Therefore, a poppet valve 153 has substantially the same shape as that of 
the poppet valve shown in FIG. 8. However, the poppet valve 153 is reset 
by a coil spring 180. The remaining construction of the present embodiment 
is identical to that of the vacuum control apparatus 150 shown in FIG. 8, 
and its detailed description will therefore be omitted. Incidentally, 
operations and effects of the vacuum control apparatus 150 shown in FIG. 9 
are substantially identical to those of the vacuum control apparatus shown 
in FIG. 8. 
Further, the vacuum control apparatuses shown in FIGS. 8 and 9 can also be 
plurally provided in continuation with one another and manifolded. The 
vacuum control apparatus may be set up so as to have the arrangement shown 
in FIG. 5, which is disclosed in Japanese Patent Application Laid-Open 
Publication No. 63-154900, for example. Moreover, valves and sensor 
control portions (reference numerals 168a, 170a, 174 in the present 
embodiment) may be integrally formed to carry out processes such as 
control for electromagnetic valves, confirmation for the attraction of a 
work, precognition of a failure and ON/OFF control of each valve. In the 
above-described embodiment, the threshold values are set up in digital 
form with respect to the maximum value of the pressure values which vary 
with time. However, as an alternative to the above method, there is a 
method wherein information about curves indicative of changes in pressure 
is stored and various threshold values can be set based on the curve 
information. 
The vacuum unit according to the present invention can bring about the 
following advantages. 
Internal pressures of the vacuum unit are detected by a pressure sensor 
disposed on either one of the upstream stream and downstream sides of at 
least one of components provided inside the vacuum unit. In addition, 
threshold values relative to the internal pressures are set by a setting 
means and a detected pressure value is compared with each of these 
threshold values, thereby confirming a failure in the operation of the 
vacuum unit. Further, a failure such as clogging of a filter can be 
confirmed from variations in pressure of the individual components and 
hence failure or faulty points can be specified. It is therefore possible 
to quickly repair the faulty points or parts in the vacuum unit or replace 
same with new ones. 
Having now fully described the invention, it will be apparent to those 
skilled in the art that many changes and modifications can be made without 
departing from the spirit or scope of the invention as set forth herein.