Measuring and testing – Fluid pressure gauge – Mounting and connection
Reexamination Certificate
2000-12-22
2003-06-10
Williams, Hezron (Department: 2855)
Measuring and testing
Fluid pressure gauge
Mounting and connection
C073S116070
Reexamination Certificate
active
06575039
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
The present invention is related to Japanese patent application No. Hei. 11-366457, filed Dec. 24, 1999; the contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to a combustion pressure sensor, and more particularly, to a combustion pressure sensor screwed into a tapped hole formed on an engine.
BACKGROUND OF THE INVENTNION
In JP-A No. H7-139736 a glow plug with a combustion pressure sensor used as a starting auxiliary device for an engine such as a diesel engine or the like is described. A general structural schematic cross sectional view of a conventional glow plug with combustion pressure sensor is shown in FIG.
14
A.
FIG. 14B
shows the outer peripheral shape of the top view of the hexagonal portion
201
b
of the housing
201
shown in
FIG. 14A
for comparison with a combustion pressure sensor
30
.
A glow plug with combustion pressure sensor J
1
is provided with a plug body (unique to the glow plug)
200
that holds a heater
206
(heated when a current is supplied in the housing
201
) a combustion pressure sensor (pressure sensor)
30
fixed to the plug body
200
for detecting a combustion pressure in an engine based on combustion pressure force exerted on the plug body
200
, and a lead wire
500
outputting a signal from the combustion pressure sensor
30
.
One end of the plug body
200
is inserted into a tapped hole
1
b
formed on an engine head
1
of a diesel engine. The plug body
200
is screw-fixed to the engine head
1
. For the screw fixing, a fixing screw
201
a
formed on the outer peripheral surface of the housing
201
of the plug body
200
is screwed by turning the plug body
200
round the axis by means of the hexagonal portion
201
b
formed on the other end of the housing
201
.
The spark plug function of the glow plug J
1
will be described herein under. A voltage is applied to a middle shaft
204
from a power source though a connecting bar
2
, and earthed to the engine head
1
through a heater coil
203
, a sheathed tube
202
, and the housing
201
. Thereby, the heater
206
comprising the heater coil
203
and sheathed tube
202
is heated for auxiliary ignition starting of the diesel engine.
The combustion pressure sensor
30
is a ring-shaped component having a through hole
30
a
and an inside screw portion
311
. The plug body
200
is inserted into the through hole
30
a
, and the combustion sensor
30
is fixed to the fixing screw
201
a
of the plug body
200
by means of screw fixing. Furthermore, the one end of the lead wire
500
is connected electrically to the top end surface of the combustion pressure sensor
30
with interposition of a fixing metal member
333
. The other end of the lead wire
500
is provided with a connector
400
for connecting to an external terminal for leading out the sensor signal to the external (ECU or the like of a vehicle).
The combustion pressure is detected as described herein. A combustion pressure generated in a combustion chamber
1
a
is transmitted to the fixing screw
201
a
through the heater
206
and the housing
201
. Because the housing
201
is pushed up in the axial direction of the screw hole
1
b
and concomitantly deformed slightly, the load of the combustion pressure sensor
30
is relaxed. The sensor
30
converts the load change to an electrical signal and thus the combustion pressure is thereby detected.
A sequential work for attaching the glow plug with combustion pressure sensor J
1
will be described with reference to FIG.
15
and FIG.
16
. The combustion pressure sensor
30
is inserted previously along the fixing screw
201
a
of the housing
201
of the plug body
200
to attach the combustion pressure sensor
30
temporarily. At that time, because the outside diameter of the hexagonal portion
201
b
of the plug body
200
is larger than the inside diameter of the through hole
30
a
of the combustion pressure sensor
30
as shown in
FIG. 14B
, the plug body
200
is inserted into the through hole
30
a
of the combustion pressure sensor
30
from the heater
206
side (the insertion side to the screw hole
1
b
).
The plug body
200
is inserted into the screw hole
1
b
of the engine head
1
in this state, the hexagonal portion
201
b
is turned round the axis by use of a plug wrench
900
(refer to FIG.
15
), only the plug body
200
is fastened to the screw hole
1
b
for holding and fixing. Then, the hexagonal portion
312
of a nut of the combustion pressure sensor
30
is turned round the axis along the fixing screw
201
a
of the housing
201
for fastening to hold and fix the bottom surface of the combustion pressure sensor
30
against the pedestal surface (surface)
1
e
of the engine head
1
.
However, as the result of examination of the sequential attachment of the conventional glow plug J
1
conducted by the inventors of the present invention, the problem described herein under was found. The hexagonal portion (nut portion)
201
b
of the plug body
200
into which a plug wrench
900
is inserted is located as close as possible to the lead wire
500
and the fixing metal member
333
of the combustion pressure sensor
30
.
The reason why these components are located so close as described hereinabove is that addition of the vibration noise (for example, the frequency is 5 kHz or lower) generated from the plug body
200
itself to the combustion pressure detected by means of the combustion pressure sensor
30
is reduced more as the top end surface of the hexagonal portion
201
b
of the plug body
200
is located closer to the top end surface of the hexagonal portion
312
of the combustion pressure sensor
30
. Specifically, as the length of the portion not held and fixed by means of other member and opened out of the plug body
200
is shorter. The close location is the important factor for securing the performance.
Therefore, in fastening the plug body
200
, when a plug wrench
900
is fit on the hexagonal portion
201
b
as shown in
FIG. 15
, the end of the plug wrench
900
can touch the lead wire
500
and break the lead wire
500
due to bending or nicking or deformation or breaking of the fixing metal member
333
.
Careful and cautious work is required to avoid interference between the plug wrench
900
and the lead wire
500
of the combustion pressure sensor
30
and entanglement between the lead wire
500
and the connector
400
and the portion around the engine.
As described hereinabove, when the glow plug J
1
has a conventional combustion pressure sensor, there are workability and working efficiency problems due to the lead wire
500
connected to the combustion pressure sensor
30
. Such problems are common not only for the glow plug with combustion pressure sensor but also for a structure that is screw-fixed to a screw hole formed on an engine by turning the one end of the structure that has been inserted into the screw hole round the axis and a combustion pressure sensor provided with a combustion pressure sensor attached to the structure (simply referred to as combustion pressure sensor hereinafter).
SUMMARY OF THE INVENTNION
It is therefore an object of the present invention to improve the workability in forming a combustion pressure sensor without adverse effects on a lead wire connected to a combustion pressure sensor.
To accomplish these and other objects, the invention described in a first aspect provides a combustion pressure sensor characterized in that the outer diameter of the end including the nut portion of the structure inserted into the screw hole is smaller than the inside diameter of the through hole of the combustion pressure sensor. Therefore, the structure can be inserted into the through hole of the combustion pressure sensor from the other end of the structure.
In the present invention, because the structure can be inserted from the nut portion side end (the other end), the sensor can be attached to the structure after the structure has been screw-connected to the screw hole of the engine. Therefore, the adverse ef
Hattori Kouichi
Murai Hiroyuki
Denso Corporation
Mack Corey D.
Williams Hezron
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