Abstrict A compact and light flow meter having a rapid response includes
a main body having a groove portion opened in the upper portion
and also having connecting portions for communicating the groove
portion and the exterior at both ends of the groove portion; a detachable
cover body sealing the opened upper portion of the groove portion
having a rectangular sectional shape in which a measured fluid is
flowed; and a circuit substrate coming in close contact with the
external face of the cover body. A sensor hole opened to the measuring
chamber is arranged in the cover body; and a flow sensor is arranged
in the circuit substrate so as to be arranged within the sensor
hole and set a detecting face to face the measuring chamber.
Claims 1. A flow meter comprising: a main body having a groove portion
opened in the upper portion and also having connecting portions
for communicating said groove portion and the exterior at both ends
of the groove portion; a detachable cover body sealing the opened
upper portion of said groove portion to constitute a measuring chamber
having a rectangular sectional shape in which a measured fluid is
flowed; and a circuit substrate coming in close contact with the
external face of said cover body; wherein a sensor hole opened to
said measuring chamber is arranged in said cover body; and a flow
sensor is arranged in said circuit substrate so as to be arranged
within said sensor hole and set a detecting face to face said measuring
chamber.
2. The flow meter according to claim 1 wherein the detecting face
of said flow sensor is arranged on the outer face side from the
inner face of said cover body, or on the same plane as the inner
face of said cover body.
3. The flow meter according to claim 1 wherein net bodies are
engaged with grooves arranged in said main body and said cover body
and are fixed on the upstream side and the downstream side of said
flow sensor of said measuring chamber.
4. The flow meter according to claim 1 wherein said connecting
portion has a joint member constructed by a hard material.
5. The flow meter according to claim 2 wherein net bodies are
engaged with grooves arranged in said main body and said cover body
and are fixed on the upstream side and the downstream side of said
flow sensor of said measuring chamber.
6. The flow meter according to claim 2 wherein said connecting
portion has a joint member constructed by a hard material.
7. The flow meter according to claim 3 wherein said connecting
portion has a joint member constructed by a hard material.
8. The flow meter according to claim 5 wherein said connecting
portion has a joint member constructed by a hard material.
Description BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a flow meter.
[0003] 2. Background Art
[0004] In a chip mounter, etc. for sucking an IC chip in a vacuum
and holding and conveying the IC chip, it is judged whether the
IC chip is appropriately sucked and held by monitoring the existence
of an air flow of a vacuum flow path. When a compact and light flow
meter is mounted to the head of such a chip mounter requiring a
high speed operation and the existence of the air flow is monitored,
high speed responsibility is more important than the accuracy of
a flow rate. In patent literatures 1 and 2 the high speed responsibility
is improved by devising the structure of a flow sensor.
[0005] [Patent literature 1] JP-A-6-66612
[0006] [Patent literature 2] JP-A-2003-240618
[0007] However, a fluid has inertia even when any high speed sensor
is used. Accordingly, the fluid is intended to be continuously flowed
within the flow meter even when the flow path is interrupted. Otherwise,
the fluid is intended to stay in the same place even when the flow
path is opened. Therefore, a problem exists in that a change in
the flow velocity of a measured fluid within the flow meter is delayed
and delay is caused in detection.
SUMMARY OF THE INVENTION
[0008] Therefore, an object of the present invention is to provide
a compact and light flow meter having a rapid response.
[0009] To solve the above problems, the flow meter of the present
invention comprises:
[0010] a main body having a groove portion opened in the upper
portion and also having connecting portions for communicating the
groove portion and the exterior at both ends of the groove portion;
[0011] a cover body detachably attached and constituting a measuring
chamber in which the opened upper portion of the groove portion
is sealed and a measured fluid having a rectangular sectional shape
is flowed; and
[0012] a circuit substrate coming in close contact with the external
face of the cover body;
[0013] wherein a sensor hole opened to the measuring chamber is
arranged in the cover body; and
[0014] a flow sensor is arranged in the circuit substrate so as
to be arranged within the sensor hole and set a detecting face to
face the measuring chamber.
[0015] In accordance with this construction, the groove portion
of the main body of the flow meter is sealed by the cover body and
the measuring chamber having a rectangular sectional shape is constructed.
Accordingly, while the connecting portions for connection to external
piping, etc. for flowing the measured fluid are arranged at both
ends of the measuring chamber in the flow meter, it is possible
to arrange the measuring chamber for flowing the measured fluid
and having a rectangular sectional area wider than that of the flow
path of the connecting portion. Since the sectional area of the
measuring chamber is increased and the flow velocity within the
measuring chamber is reduced as much as possible, kinetic energy
of the measured fluid is reduced and the measured fluid within the
flow meter can be set to be rapidly stopped when the flow path is
interrupted. Accordingly, the response of the flow meter can be
set to a high speed response.
[0016] Further, in the flow meter of the present invention, the
detecting face for measuring the flow velocity of the flow sensor
may be arranged on the outer face side from the inner face of the
cover body, or on the same plane as the inner face of the cover
body.
[0017] In accordance with this construction, the detecting face
of the flow sensor has no direction in which the upstream measured
fluid is continuously flowed by inertia at the interrupting time
of the flow path. Accordingly, the delay of a flow velocity change
due to the inertia is small and the high speed responsibility of
a flow rate measurement is excellent.
[0018] Further, in the flow meter of the present invention, net
bodies may be engaged with grooves arranged in the main body and
the cover body and may be fixed on the upstream side and the downstream
side of the flow sensor of the measuring chamber.
[0019] In accordance with this construction, the flow of the measured
fluid within the measuring chamber can be rectified by the net body.
Further, since one end of the net body is engaged by arranging the
groove in the cover body, there is no gap between the cover body
and the net body, and no disturbance is caused in the upstream of
the flow sensor. Thus, a high accuracy flow rate measurement can
be made.
[0020] Further, in the flow meter of the present invention, the
connecting portion may have a joint member constructed by a hard
material.
[0021] In accordance with this construction, the connecting portion
engaged with a joint, etc. for connection to the flow path of the
measured fluid can be made compact and set to high strength so that
the flow meter can be made compact and light in weight.
[0022] As mentioned above, in accordance with the present invention,
it is possible to provide a compact flow meter light in weight and
having a rapid response.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a perspective view of a flow meter in an embodiment
mode of the present invention.
[0024] FIG. 2 is an exploded perspective view of the flow meter
of FIG. 1.
[0025] FIG. 3 is a sectional view of the flow meter of FIG. 1 in
a flow perpendicular direction.
[0026] FIG. 4 is a sectional view of the flow meter of FIG. 1 in
a flow direction.
[0027] FIG. 5 is a partial enlarged view of a flow sensor of FIG.
4.
[0028] FIG. 6 is a graph showing output waveforms of the flow meter
of the present invention and a conventional flow meter.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] FIG. 1 shows the external appearance of a flow meter 1 in
an embodiment mode of the present invention. FIG. 2 shows a disassembled
situation of the flow meter 1. The flow meter 1 approximately has
a rectangular parallelepiped outer shape constructed by a main body
2 and a cover 3. Four net bodies 4 in total, a cover body 5 a first
circuit substrate 6 and a second circuit substrate 7 are stored
into the flow meter 1.
[0030] Further, the construction of the flow meter 1 will be explained
in detail with reference to FIG. 3 showing a cutting situation in
the short direction in the central portion of the flow meter 1
and FIG. 4 showing a cutting situation in the long direction.
[0031] The main body 2 has two attaching holes 9 in a bottom wall
8. Further, the main body 2 has a groove portion 11 in which the
upper portion constructed by the bottom wall 8 and side walls 10
on both sides is opened. Two thin grooves 12 perpendicular to the
longitudinal direction are arranged near each of both ends of the
groove portion 11. Further, a joint member 13 having circular screw
holes manufactured by a metal at both ends of the groove portion
11 is buried at a molding time so as to communicate the interior
of the groove portion 11 and the exterior of the main body 2 and
is molded by resin. The outside of the upper end of the side wall
10 is further extended above the groove portion 11 and forms a
guide wall 14. An elastic piece 16 having an engaging hole 15 is
projected at each of the upper ends of both the guide walls 14.
[0032] A concave groove 17 is formed on the side face of the cover
3. An engaging projection 18 engaged with the engaging hole 15 of
the above elastic piece 16 is projected in the bottom of the concave
groove 17.
[0033] The net body 4 is greater by a turn than the section of
the groove portion 11 and is a mesh manufactured by a metal and
having a rectangular shape and engaged with the groove 12.
[0034] The cover body 5 is arranged within the guide wall 14 and
constitutes a measuring chamber 19 in which an opening portion of
the upper portion of the groove portion 11 is sealed and a measured
fluid having a rectangular sectional shape is flowed. A sensor hole
20 opened to the upper portion of the measuring chamber 19 is arranged
at the center of the cover body 5. A thin groove 21 is arranged
so as to be connected to the groove 12 of the main body on the inner
face of the measuring chamber 19 near both ends of the cover body
5. The groove 21 is engaged with the upper end of the net body 4.
[0035] The first circuit substrate 6 is arranged so as to come
in close contact with the outer face of the cover body 5 in the
upper portion of the cover body 5 and seals the sensor hole 20
of the cover body 5. A flow sensor 22 is arranged on the lower face
of the first circuit substrate 6 so as to be arranged within the
sensor hole 20. A male type internal connector 23 is arranged on
the upper face of the first circuit substrate 6.
[0036] In the second circuit substrate 7 a female type internal
connector 24 engaged with the male type internal connector 23 of
the first circuit substrate is arranged on the lower face of the
second circuit substrate 7. An external connector 25 is further
arranged in the second circuit substrate 7. The flow meter 1 can
be electrically connected to an external control device through
a connector hole 26 formed in the cover 3.
[0037] FIG. 5 shows a situation in which a portion of the flow
sensor 22 of FIG. 4 is enlarged. In the flow sensor 22 a heating
body 28 and measuring temperature bodies 29 30 located before and
after the heating body 28 are arranged on a detecting face 27. The
flow sensor 22 is constructed by a thermal type flow sensor chip
in which the flow velocity is calculated from the difference in
temperature between before and after the heating body 28 by measuring
the temperature of the measured fluid by the measuring temperature
bodies 29 30. The detecting face 27 of the flow sensor 22 is arranged
so as to be located outside the measuring chamber 19 by a distance
D (about 0.05 mm) from the inner face of the cover body 5. The sensor
hole 20 has a size able to form gaps G (about 0.7 mm) on both sides
of the flow meter 1 in the longitudinal direction in the flow sensor
22.
[0038] In the flow meter 1 having the above construction, the joint
member 13 is connected to the flow path of the measured fluid and
is fixed by the attaching hole 9 so as to flow the measured fluid
in the direction of the arrow shown in FIG. 1. As shown in FIG.
4 the measured fluid is flowed from the direction of the arrow
to the joint member 13 and is rectified through two net bodies
4 and passes through the measuring chamber 19 and is further flowed
out through two net bodies 4 and the joint member 13. The flow rate
of the measured fluid is measured by the flow sensor 22 while the
measured fluid passes through the measuring chamber 19. Thus, it
is possible to detect interruption and opening of the flow path
connected to the flow meter 1.
[0039] In the flow meter 1 the groove portion 11 opened in the
upper portion is arranged in the main body 2 and the measuring
chamber 19 is constructed by sealing the groove portion 11 by the
cover body 5. Accordingly, it is not necessary to arrange a trimming
die for molding so as to extend one end of the measuring chamber
19 to the exterior. Therefore, it is possible to integrally mold
a connection portion having a flow path thinner than the measuring
chamber 19 before and after the measuring chamber 19. The measuring
chamber 19 can be set to a rectangular sectional shape so as to
maximize the sectional area within the rectangular parallelepiped
flow meter 1 without being restrained to the structure of the connecting
portion. Thus, the flow velocity of the measured fluid within the
measuring chamber 19 is lowly restrained and kinetic energy of the
measured fluid can be reduced. Therefore, when the flow path is
interrupted in the exterior of the flow meter 1 the measured fluid
within the measuring chamber 19 is small in inertia force and is
rapidly stopped. Thus, the flow meter 1 can rapidly detect the stoppage
of the fluid by the flow sensor 22. Further, when the flow rate
is instantaneously increased, it is not necessary to greatly accelerate
the measured fluid within the measuring chamber 19. Accordingly,
the influence of the inertia is small and it is possible to achieve
a stationary speed for a short time, and the flow meter 1 can detect
a speed change of the measured fluid for a short time.
[0040] The flow of the measured fluid within the measuring chamber
19 is different in speed in accordance with places, and is approximately
stopped due to friction in positions adjacent to the bottom wall
8 of the main body 2 the side wall 10 and the cover body 5. A flow
velocity distribution for maximizing the flow velocity at the center
of the measuring chamber 19 can be formed. In the flow meter 1
the detecting face 27 of the flow sensor 22 is arranged slightly
outside the inner face of the cover body 5 (may be also arranged
on the same plane as the inner face of the cover body 5). Accordingly,
the flow rate is measured by heat transfer due to the measured fluid
having a comparatively low flow velocity near the cover body 5.
Therefore, even when the flow rate is instantaneously changed, the
delay of the detection due to the inertia of the measured fluid
is reduced so that a high speed response is obtained.
[0041] The groove 20 and the groove 21 are arranged in the bottom
wall 8 of the main body 2 the side wall 10 and the cover body 5
near both ends of the measuring chamber 19. The net bodies 4 are
engaged with these grooves and are fixed. Therefore, the flow of
the measured fluid within the measuring chamber 19 is rectified
by passing through the net bodies 4 and becomes a stable laminar
flow approximately having no turbulent flow, and the flow rate can
be measured with high accuracy. In particular, when there is a gap
between the cover body 5 and the net body 4 the measured fluid
entering from the gap becomes an irregular disturbance, and this
disturbance is flowed toward the flow sensor 22. Therefore, this
disturbance becomes a cause of a reduction in measuring accuracy.
However, since the groove 21 is arranged in the cover body 5 and
the net body 4 is engaged with the groove 21 in the flow meter 1
no gap is generated between the cover body 5 and the net body 4.
Therefore, no flow near the flow sensor 22 is disturbed and the
measuring accuracy is high.
[0042] In the flow meter 1 the connecting portion for connection
to the flow path is integrally molded by burying the joint member
13 in molding the main body 2 by resin. Since the joint member 13
obtained by precisely processing a hard material is used, a structure
of the connecting portion smaller than that formed by the resin
molding and high in strength and precise and having a high general
purpose property is obtained. Thus, the flow meter 1 is compact
and light in weight. The joint member 13 can be buried and molded
since the measuring chamber 19 is constructed by the groove portion
11 arranged in the main body 2 and the cover body 5 so that it is
not necessary to arrange a trimming die for molding the measuring
chamber 19 in the connection portions at both ends of the measuring
chamber 19 as mentioned above.
[0043] FIG. 6 shows an example of response output waveforms when
the conventional flow meter and the flow meter 1 of this embodiment
mode are arranged within the flow path of a vacuum circuit and the
flow path is instantaneously interrupted. The flow meter 1 outputs
a voltage proportional to the flow rate, and outputs 1 V when the
flow rate is zero. When the flow meter 1 is used in a chip mounter
and chip suction holding is confirmed, it is judged that the chip
is appropriately held when the output voltage is 1 V. As shown in
FIG. 6 in the conventional example showing the output waveform
of the conventional flow meter, about 28 milliseconds are required
until the output voltage is completely lowered to 1 V or less by
the influence of inertia of the air. However, in the embodiment
showing the output of the flow meter 1 of this embodiment mode,
the time required to lower the output voltage to 1 V or less is
about 3 milliseconds. Accordingly, it has been confirmed that the
flow meter is operated at very high speed.
[0044] The flow meter of the present invention can be also applied
to a semiconductor wafer chuck, an adsorbing device of a thin film
part, flow rate monitoring of an air duct, air-fuel ratio management
of a fuel device, flow control, etc. as well as the high speed mounting
machine of the chip mounter. |