JP2548688Y2 - Pressure sensor - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor for detecting a change in a cylinder internal pressure of an internal combustion engine by a piezoelectric element.

[0002]

2. Description of the Related Art A detection element such as a piezoelectric element and a pressure transmission rod is housed in a metal shell mounted in a screw hole for mounting a sensor provided in a cylinder head of an internal combustion engine, and a lower end face located in a cylinder. A pressure sensor is known in which a diaphragm is sealed to the piezoelectric element, and the internal pressure of the cylinder is propagated to the piezoelectric element through the diaphragm and the pressure transmission rod, and an electric signal proportional to the magnitude of the internal pressure of the cylinder is taken out from the element. is there.

[0003]

[Problem to be Solved by the Invention] This type of pressure sensor
In this case, as shown in FIG.
Insert the transfer cable 30 and connect the signal transfer cable 3
0 and, via the hand electrode and the various conductive member of the piezoelectric element 11
And the lead wire 31 electrically connected to the
So that the rear end is electrically connected by welding
Then, the metal cap 26 is placed on the upper end of the metal shell 1.
By welding. By the way, this signal
The connection between the transfer cable 30 and the lead wire 31 is made of metal.
The joining should be performed with the cap 26 opened.
You. Therefore, it is possible to make this work possible, or
Lead wires to prevent them from being cut
31 has a sufficient length. For this reason,
When the metal cap 26 is attached to the metal shell 1,
The wire 31 is wound in a spiral shape as shown in FIG.
The inner surface of the hole 4 is easily contacted. Meanwhile, metal
To fix the cap 26 to the metal shell 1, a metal cap
The flange 27 of the loop 26 is attached to the edge of the metal shell 1 by argon welding or the like.
It is performed by means of. This welding heat causes the metal key
The cap 26 and the upper part of the metal shell 1 become hot.
U. However, the defective pressure sensor is disassembled and various adjustments are made.
If you look at it, one of the reasons is that the lead
When the wire 31 is in contact with the inner surface of the shaft hole 4,
Due to the transient welding heat of the metal shell 1,
The coating material such as fluororesin coating the lead wire 31
And the lead wire 31 is electrically connected to the metal shell 1 or the like.
As a result, the signal cannot be extracted.
I knew there was something. The purpose of the present invention is to eliminate such a problem.

[0004]

According to the present invention, there is provided a metal member in which a number of protrusions are formed on an outer peripheral surface of an upper portion of a shaft hole of a metal shell through which a lead wire of a signal carrying cable is inserted. A heat shielding cylinder made of a material is provided.

[0005]

The projection of the heat shield cylinder comes into contact with the inner surface of the shaft hole to make point contact. Therefore, even when the metal shell and the metal cap become hot when welding the metal cap, the heat shield cylinder is only in point contact, and the heat is shut off by the air layer between the inner surface of the shaft hole and the heat shield cylinder, High temperature is prevented. Therefore, even if the lead wire passing through the inside of the heat shield tube comes into contact with the inner surface of the tube, the coating does not melt, electrical insulation between the lead wire and the metal shell is ensured, and signal from the signal carrying cable is Output can be taken out favorably.

[0006]

FIG. 1 shows an embodiment of the present invention, in which 1 is a male screw 2 screwed to a cylinder head on the outer periphery of a lower end 1a, and a tightening tool such as a wrench on the outer periphery of a substantially middle portion 1b of the entire length. A metal shell having a bolt structure formed with a matching hexagonal portion 3, and a shaft hole 4 is formed therein. The shaft hole 4 penetrates from the lower end portion 1a side to the upper end portion 1c side, and is configured by connecting mounting holes 4a and 4b, screw holes 4c and mounting holes 4d. The mounting hole 4a has a smaller diameter than the mounting hole 4b, and a step portion is formed therebetween.

A pressure transmission rod 9 is inserted into the small-diameter mounting hole 4a, and the lower end thereof is argon-welded to a metal diaphragm 6 joined so as to hermetically seal the end surface of the lower end 1a of the metal shell 1. ing. The metal diaphragm 6 needs to have heat resistance, and is preferably made of, for example, a heat-resistant metal material such as Inconel or SUS630. Further, a disc spring 7 is provided between the stepped portion of the mounting holes 4a and 4b of the metal shell 1 and the pressure transmission rod 9 to support a large diameter portion of the pressure transmission rod 9, and the disc spring 7 It absorbs the strain caused by the difference between the thermal expansion and the heat transfer of each component, and the stress caused by elongation due to the tightening torque at the male screw portion.

In the mounting hole 4b, an annular packing 10, a piezoelectric element 11 having electrodes formed on the front and back surfaces, terminal members 12, 13, an annular packing 14, an electric insulating ring 15, and a metal plate 16 are arranged from the side closer to the mounting hole 4a. Etc. are sequentially arranged in a laminated state,
The metal shell 1 is insulated from the metal shell 1 by an insulating material 17 covering the periphery of the stacked body 8. An upright tongue piece 13a projects from the upper surface of the terminal member 13.

A hemispherical surface is formed at the upper end of the abutment 16, and a holding screw 18 having a conical concave surface on the hemispherical surface is screwed into the screw hole 4c. The adhesive is fixed by an adhesive and tightly attached, and an appropriate preload is applied to the piezoelectric element 11 by the tightening action via the pad 16 and the like. The fund 1
6, a hole is formed at the center of each of the holding screws 18, and an insertion hole 20 is formed together with the electric insulating ring 14 in the assembled state. Then, an insulating tube 21 is fitted into the insertion hole 20, the upright tongue 13 a is inserted into the insulating tube 21, and a lead wire 31 connected to a core wire of a signal carrying cable 30 described later is made upright. The connection with the tongue piece 13a is made in the insulating tube.

A step seat 25 is formed at the mouth of the mounting hole 4d on the upper end 1c side, and a metal cap 26 having a flange 27 to be seated therein is fitted and argon welded.
The signal carrying cable 3 is provided inside the metal cap 26.
0 is inserted and fixed at one end of the cable 30 as described above.
Is connected to the upright tongue piece 13a. Reference numeral 37 denotes a rubber tube closely fitted between the signal carrying cable 30 and the cap 26.

In this configuration, the holding screw 18
And the metal cap 26, the lead wire 31 is wound slightly and inserted loosely, so that even if tension is applied to the cable 30 or an external impact is applied, the lead wire 31 is The connection between the piezoelectric element 11 and the standing tongue piece 13a is prevented from being broken, and the electrical connection with the piezoelectric element 11 is ensured. The lead wire 31 and the upright tongue piece 13
The inside and outside of the tube 21 are filled with a heat-resistant resin such as silicone rubber in order to prevent disconnection from the tube a and prevent the insulating tube 21 from coming off due to vibration or the like. Further, the lead wire is coated with a fluororesin.

As shown in FIGS. 2 and 3, a heat shield cylinder 35 made of a metal material according to the present invention is disposed between the holding screw 18 and the metal cap 26. Are wound appropriately in the heat shielding cylinder 35 and loosely inserted therethrough. The heat shield cylinder 35 has countless projections 36 formed on the outer surface thereof, and is configured by winding a metal plate. Then, the spring force is generated in the radial direction by the restoring force due to the winding, and each projection 36 comes into contact with the inner surface of the shaft hole 4 to be stably held. It is desirable that the heat shield cylinder 35 has poor heat conductivity, and for example, a stainless material is used. still,
The heat shielding cylinder 35 may be formed in a cylindrical shape in advance.

In such a structure, the metal cap 2
When argon is welded to the metal shell 1, the welded portion is heated, and the metal cap 26 and the upper part of the metal shell 1 become hot. By the way, this heat shielding cylinder 35 is
Is fitted in contact with the inner surface of the shaft hole 4, so that even if the metal shell 1 or the like is heated to a high temperature, there is a limit to the heat transfer due to the point contact of the projection 36, which is secured by the projection 36. The heat conduction is cut off by the air layer between the heat shield cylinder 35 and the inner surface of the shaft hole 4. Moreover, since the heat shield cylinder 35 is made of metal, the emissivity is small, and the heat reception by the heat radiation from the metal shell 1 is small.

Therefore, even when the metal shell 1 is heated, the heat shield cylinder 35 does not become hot, and therefore the lead wire 31 inserted through the heat shield cylinder 35 is in contact with the inner surface thereof. In addition, the coating does not melt to cause insulation failure. Thus, the lead wire 31 is protected by the heat shield cylinder 35, and is prevented from being affected by heat during welding.

[0015]

[Effect of the Invention] As described above, the pressure sensor of the present invention
On the upper inner surface of the metal shell 1 through which the lead wire 31 of the signal carrying cable 30 is inserted, a heat shield cylinder 35 made of a metal material and having innumerable protrusions 36 in contact with the inner surface of the shaft hole 4 is formed. Therefore, even if the metal shell 1 and the metal cap 26 are rapidly heated when the metal cap 26 is welded, the lead wire 31 is protected by the heat shield cylinder 35, and the lead wire coating is not melted. 31 and metal shell 1
There is an excellent effect that electrical insulation with the like can be ensured and an appropriate signal output can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view of a pressure sensor showing one embodiment of the present invention.

FIG. 2 is a perspective view of a heat shield cylinder 35.

FIG. 3 is an enlarged vertical sectional side view of a main part.

FIG. 4 is a vertical sectional side view showing a problem of the conventional configuration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal shell 4 Shaft hole 9 Pressure transmission rod 11 Piezoelectric element 26 Metal cap 30 Signal transmission cable 31 Lead wire 35 Heat shield cylinder 36 Projection

Claims (1)

(57) [Scope of request for utility model registration] 1. A detection element such as a pressure transmission rod or a piezoelectric element is housed in a shaft hole formed in a metal shell mounted on a cylinder of an internal combustion engine, and an opening end of the shaft hole is formed by a metal diaphragm. The metal cap is welded to the upper end of the metal shell, and a signal carrying cable is inserted into the shaft hole from the metal cap, and a lead wire of the signal carrying cable is electrically connected to one electrode of the piezoelectric element. In the pressure sensor configured to be connected, a metal material in which a myriad of projections that are in contact with the inner surface of the shaft hole are formed on the outer peripheral surface of the upper portion of the shaft hole of the metal shell through which the lead wire of the signal carrying cable is inserted. A pressure sensor, comprising a heat shield tube made of: