Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
2000-07-19
2004-12-07
Deb, Anjan K. (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S690000
Reexamination Certificate
active
06828806
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrostatic capacitance sensor, an electrostatic capacitance sensor component, an object mounting body and an object mounting apparatus, and more particularly, to an electrostatic capacitance sensor which is a nearby-object detecting sensor utilizing a variation in electrostatic capacitance and which can be utilized for an FA (Factory Automation) device, an inspecting device, a robot, a semiconductor manufacturing apparatus and the like, an electrostatic capacitance sensor component for such an electrostatic capacitance sensor, an object mounting body including such an electrostatic capacitance sensor component, and an object mounting apparatus having such an electrostatic capacitance sensor.
2. Description of the Related Art
FIG. 15
shows a sensor and a front stage of an amplifier of a conventional electrostatic capacitance nearby-object detector described in Japanese Patent Application Laid-open No. H7-29467. In
FIG. 15
, a sensor
111
comprises a three-layer printed substrate
112
. A first layer pattern formed on one face of the printed substrate
112
is a detecting electrode
112
a
disposed to be opposed to an object detecting region. An inside pattern of the printed substrate
112
is a second layer pattern for shielding the detecting electrode
112
a,
i.e., an in-phase shield pattern
112
b.
A third layer pattern formed on the other face of the printed substrate
112
is a shield earth pattern
112
c.
The shield earth pattern
112
c
is a pattern for reducing an influence of noise from outside acting on the detecting electrode
112
a
and the in-phase shield pattern
112
b.
The patterns
112
a
and
112
b
are respectively connected to a core wire and a coated wire of the shield cable
113
, and connected to a side of a main circuit
114
. In the main circuit
114
, the core wire to which the detecting electrode
112
a
is connected is connected to an input terminal of a buffer circuit
115
. An output terminal of the buffer circuit
115
is connected to the coated wire of the shield cable
113
, and connected to an input terminal of a Schmitt trigger circuit
116
. A feedback resistance R is connected between an output terminal of the Schmitt trigger circuit
116
and an input terminal of the buffer circuit
115
.
If a grounded object approaches the detecting electrode
112
a,
an electrostatic capacitance Cd therebetween is increased. The buffer circuit
115
and the Schmitt trigger circuit
116
constitute an oscillation circuit
117
which oscillates with the electrostatic capacitance Cd and the feedback resistance R as the time constant components, and an output of the oscillation circuit
117
is connected to a periodic counter
118
. The periodic counter
118
measures an oscillating period of the oscillation circuit
117
, and an output of the periodic counter
118
is applied to a linearizer
119
. The linearizer
119
linearizes a periodical variation to be a variation in a distance to the object. An output of the linearizer
119
is input to a display circuit
120
and a comparison circuit
121
. The comparison circuit
121
discriminates input signals with respect to a predetermined threshold value, and a judging signal indicative of whether there exists an object is output from an output circuit
122
.
According to the above structure, since the detecting electrode
112
a
and the in-phase shield pattern
112
b
are connected to the input and output terminals of the buffer circuit
115
through the shield cable
113
, the detecting electrode
112
a
and the in-phase shield pattern
112
b
are always at the same phase and same voltage. Therefore, the detecting electrode
112
a
does not receive an influence of the electrostatic capacitance between the detecting electrode
112
a
and the in-phase shield pattern
112
b.
Thus, a sensor section having the detecting electrode and an electronic circuit section can be separated from each other by the shield cable
113
.
As described above, according to Japanese Patent Application Laid-open No. H7-29467, the sensor comprises the first layer pattern
112
a
of the detecting electrode for detecting the object, the second layer pattern
112
b
for the shield, and the grounded third layer electrode pattern. The amplifier and the detecting electrode are connected through the shield cable
113
, and the separate ground wire is provided. This structure has the following problems:
(1) This structure requires a detecting electrode wire, a shield wire and a grounding wire, and the structure is complicated and the cost is increased.
(2) This structure requires a detecting electrode, a shield electrode and a grounding electrode, and the structure is complicated and the cost is increased.
SUMMARY OF THE INVENTION
It is, therefore, a main object of the present invention to provide an electrostatic capacitance sensor of a simple structure, an electrostatic capacitance sensor component for such an electrostatic capacitance sensor, an object mounting body including such an electrostatic capacitance sensor component, and an object mounting apparatus having such an electrostatic capacitance sensor.
According to a first aspect of the present invention, there is provided an electrostatic capacitance sensor, comprising
an electrostatic capacitance detector,
an operational amplifier in which a feedback impedance circuit is connected between an output terminal and an inverse input terminal of the operational amplifier,
a signal line connected between the inverse input terminal of the operational amplifier and the electrostatic capacitance detector,
an alternating-current signal generator connected to a non-inverse input terminal of the operational amplifier, and
a shield for shielding at least a portion of the signal line, the shield being connected to the non-inverse input terminal of the operational amplifier and the alternating-current signal generator, wherein
the electrostatic capacitance detector comprises a detecting electrode and a shield electrode,
the detecting electrode comprises a detector-detecting electrode for detecting an object to be detected and an electrode introducer-detecting electrode for introducing an electrode to the detector-detecting electrode,
the shield electrode is connected to the shield, and
at least a portion of the electrode introducer-detecting electrode is shielded by the shield electrode.
According to a second aspect of the present invention, there is provided an object mounting body for mounting an object to be mounted, comprising a detecting electrode and a shield electrode, wherein
the detecting electrode comprises a detector-detecting electrode for detecting an object to be detected and an electrode introducer-detecting electrode for introducing an electrode to the detector-detecting electrode,
the detecting electrode and the shield electrode are flat plate-like electrodes and laminated such that they become layers different from each other, and
the detecting electrode and the shield electrode are provided such that the detecting electrode and the shield electrode are not superposed, and at least a portion of the electrode introducer-detecting electrode and the shield electrode are superposed as viewed from the laminated direction of the detecting electrode and the shield electrode.
According to a third aspect of the present invention, there is provided an electrostatic capacitance sensor component, comprising an electrostatic capacitance detector having a detecting electrode and a first shield electrode, and a flat plate-like second shield electrode laminated with the detecting electrode such that the second shield electrode and the detecting electrode become layers different from each other, wherein
the detecting electrode comprises a detector-detecting electrode for detecting an object to be detected and an electrode introducer-detecting electrode for introducing an electrode to the detector-detecting electrode,
the detector-detecting electrode is a flat plate-like electrode, the detecting elect
Hiroshima Tatsuo
Hirota Yoshihiro
Matsumoto Toshiyuki
Deb Anjan K.
Sumitomo Metal Industries Ltd.
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