JPH0324978B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a combustion pressure detection device for an internal combustion engine.

(Prior art) In order to improve the fuel efficiency and output of an internal combustion engine, it is extremely meaningful to understand the actual combustion state. By doing so, it is possible to generate the best fuel efficiency and output while avoiding knocking.

As a method of grasping the combustion state, it is often done to detect the combustion gas pressure within the cylinder.
The ones shown in Figures to Figure 9 are known (Special Publication No. 41-5154, SAE Technical Paper
750883 etc.).

Spark plug screw hole 11 provided in cylinder head 10
The ignition plug 12 is screwed together, and at that time, a pressure sensor 15 as a washer is inserted between the ignition plug 12 and the mounting seat surface 14, and they are tightened together.

The pressure sensor 15 includes two piezoelectric elements 17 on both sides of a ring-shaped center electrode 16.
Further, on the outside thereof, an upper surface electrode 18 and a lower surface electrode 1 are formed.
9 are sequentially laminated, and their inner and outer peripheries are fixed together with an insulating mold member 20.

A lead wire 21 is taken out from the center electrode 16 through the mold member 20.

Since the pressure sensor 15 is tightened as a washer for the ignition plug 12, when the combustion pressure in the cylinder acts on the ignition plug 12, the tightening force increases or decreases, and as a result, the electric charge generated by the piezoelectric element 17 changes to the combustion pressure. It changes accordingly.

In this way, the combustion pressure of the internal combustion engine can be accurately extracted as an electrical signal.

(Problem to be Solved by the Invention) However, in this case, since there is no sealing means for preventing water or oil around the pressure sensor 15, rainwater or oil from the outside may leak between the ignition plug 12 and the mounting surface 14. If it accumulates between them, it tends to invade the piezoelectric element 17 and the center electrode 16, resulting in a decrease in insulation resistance, a shortfall in output, and corrosion of the electrodes.

Further, the lead wire 21 tends to pick up ignition noise from the ignition plug 12, which sometimes interferes with accurate measurement of combustion pressure.

(Means for Solving the Problems) The present invention includes a ring-shaped pressure sensor inserted into the mounting surface of an ignition plug that is screwed into the cylinder head.
In a pressure detection device for an internal combustion engine that measures the cylinder internal pressure based on the output of the pressure sensor, a cylindrical guide member is coupled to the outer periphery of the pressure sensor, and this guide member is inserted into the spark plug insertion hole of the cylinder head. On the other hand, a sealing member is fitted to the upper outer periphery of this guide member, and this sealing member is brought into close contact with the cylinder head and the plug boot of the ignition plug.

(Function) Therefore, rainwater and the like do not enter the area around the ignition plug from the outside, and the pressure sensor can be reliably prevented from corrosion.

(Example) Examples of the present invention will be described below based on FIGS. 1 to 6.

A cylindrical guide member 30 is fitted around the outer periphery of the pressure sensor 15 . The guide member 30 is press-molded from a metal plate, and is inserted and supported in a spark plug insertion hole 31 formed in the cylinder head 10.

The guide member 30 has a stepped portion 3 whose lower part is narrowed.
2, and a slit 33 is formed in this stepped portion 32 to facilitate insertion of the pressure sensor 15. The pressure sensor 15 is inserted and held in the stepped portion 32, and is positioned in the vertical direction by locking claws 34 cut and raised inward on the circumferential surface of the guide member 30.

A plurality of protrusions 35 are provided on the outer periphery of the guide member 30, and the spark plug insertion hole 31 of the cylinder head 10 is provided with a plurality of protrusions 35.
Make sure that the fit is tight.

A cylindrical seal member 36 made of a material with good adhesion such as rubber is provided on the upper outer periphery of the guide member 30.
are fitted.

A locking pawl 37 cut and raised on the upper outer periphery of the guide member 30 comes into elastic contact with the inner circumferential annular groove 38 of the seal member 36, allowing the seal member 36 to slightly slide relative to the guide member 30 in the axial direction. ing.

The ignition plug 12 is inserted into the guide member 30 and tightly screwed into the ignition plug threaded hole 11 while in contact with the pressure sensor 15 via the gasket 39.

A plug boot 40 is fitted into the upper part of the spark plug 12, and at this time, a flange portion 41 formed on the plug boot 40 is in close contact with the upper end of the seal member 36 all around. On the other hand, the lower end of the seal member 36 is connected to the boss portion 4 of the spark plug insertion hole 31 of the cylinder head 10.
2, and thereby reliably prevents rainwater etc. from entering the vicinity of the ignition plug 12, that is, the inner and outer peripheries of the guide member 30 from the outside.

The pressure sensor 15 has substantially the same structure as described above, but a protective tube 43 is fitted to the lead wire 21 connected to the center electrode 16, and a stopper is provided on the outer periphery of the guide member 30. This extended end is hooked onto a tool 44, and is taken out to the outside by passing through a lead wire take-out hole 45 provided in the seal member 36 in an airtight manner.

Note that the spark plug insertion hole 31 of the cylinder head 10
A vertical groove 46 for guiding the lead wire 21 is formed in a part of the sealing member 36, and this part bulges out so as to cover the upper end of the vertical groove 46.

With the above configuration, the pressure sensor 15 is integrated with the cylindrical guide member 30, and the guide member 30 is inserted into the spark plug insertion hole 31 of the cylinder head 10.
By inserting the lower electrode 19 into the mounting seat surface 14, the lower electrode 19 can be brought into close contact with the mounting seat surface 14. After this, the ignition plug 12 is inserted into the guide member 30 and screwed into the ignition plug screw hole 11, but at this time, the guide member 30 is firmly held in the ignition plug insertion hole 31, so the ignition plug The pressure sensor 15 does not rotate as the pressure sensor 12 is tightened.

When the plug boot 40 is fitted to the spark plug 12, the flange portion 41 comes into close contact with the upper end of the seal member 36, and the lower end of the seal member 36 comes into close contact with the boss portion 42 of the cylinder head 10, so that rainwater and oil from the outside can As a result, the corrosion resistance of the pressure sensor 15 can be significantly improved.

Furthermore, since the sealing member 36 can slightly slide relative to the guide member 30, even if there is a dimensional error in the guide member 30, it can be reliably brought into close contact with the boss portion 42 of the cylinder head 10.

(Effects of the Invention) As described above, according to the present invention, a pressure sensor is coupled to a guide member inserted and held in a spark plug insertion hole of a cylinder head, and a plug boot and a spark plug insertion hole are connected to an upper part of the guide member. Since a sealing member that tightly contacts the boss portion of the pressure sensor is attached, it is possible to reliably prevent rainwater, oil, etc. from entering the area around the pressure sensor, and the corrosion resistance of the pressure sensor can be significantly improved.

In addition, mounting and positioning of the pressure sensor are easier, and since the lead wire is shielded by the guide member, accurate output can always be obtained without being affected by ignition noise.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a sectional view as well, Fig. 3 is an enlarged sectional view of a sensor portion, Fig. 4 is a perspective view of a guide member, and Fig. 5 is a sealing member. 6 is a plan view, FIG. 7 is a sectional view of the conventional example, FIG. 8 is a sectional view of the sensor portion, and FIG. 9 is a plan view thereof. 10... Cylinder head, 11... Spark plug screw hole,
12... Ignition plug, 14... Mounting seat surface, 15... Pressure sensor, 16... Center electrode, 17... Piezoelectric element, 18... Top surface electrode, 19... Bottom surface electrode, 20... Mold member,
21... Lead wire, 30... Guide member, 31... Spark plug insertion hole, 36... Seal member, 40... Plug boot, 41... Flange portion, 42... Boss portion, 43... Protection tube, 45... Lead wire extraction hole, 46 ...Vertical groove.

Claims (1)

[Claims] 1. In a pressure detection device for an internal combustion engine in which a ring-shaped pressure sensor is sandwiched between the mounting surface of an ignition plug that is screwed into a cylinder head, and the cylinder internal pressure is measured by the output of this pressure sensor, the outer periphery of the pressure sensor is A cylindrical guide member is connected to the
The guide member is inserted and held in the spark plug insertion hole of the cylinder head, and a seal member is fitted to the upper outer periphery of the guide member, and this seal member is brought into close contact with the cylinder head and the plug boot of the spark plug. pressure detection device.