JP2001241372A - Combustion pressure sensor structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict attenuation of an output signal of a combustion pressure sensor, and reduce electric noise to the output signal in a glow plug provided with the combustion pressure sensor. SOLUTION: A glow plug 100 is provided with a plug main body part 200 mounted on an engine head 1 in an engine room, a combustion pressure sensor 300 mounted on the plug main body part 200 to convert force following combustion pressure acting on the plug main body part 200 into an electric signal based on piezoelectric characteristics of a piezoelectric ceramic 321, and a connector 400 electrically connected to the piezoelectric ceramic 321 of the combustion pressure sensor 300 through a lead wire 500, and provided with a stay 426 which can be installed in the engine room. In the connector 400, a charge amplifier 410 as an amplifying means to amplify the electric signal from the piezoelectric ceramic 321 is included.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure (for example, a glow plug, a spark plug, an injector, a bolt, etc.) attached to an engine disposed in an engine room, and an engine mounted on the structure. A combustion pressure sensor for detecting a combustion pressure.

[0002]

2. Description of the Related Art As this kind of combustion pressure sensor structure,
For example, there has been proposed a glow plug with a combustion pressure sensor used as a start-up assist device in an engine such as a diesel engine as described in Japanese Patent Application Laid-Open No. Hei 7-139736. This plug is mounted on a diesel engine of a vehicle, and has a plug body (glow heater) as a structure having a heating element that generates heat when energized, and a piezoelectric ceramic (piezoelectric) that applies a force accompanying a combustion pressure acting on the plug body. And a combustion pressure sensor (pressure sensor) that converts the electric signal into an electric signal based on the piezoelectric characteristics of the element.

In such a configuration, the combustion pressure generated in the engine is detected as a displacement of a plug body attached to the engine, and this displacement is applied to the piezoelectric ceramics of the combustion pressure sensor. It is transmitted as fluctuation of the shaft load due to the tightening force, converted into an electric signal, and output as a combustion pressure. And
This output signal (combustion pressure) is input to an external circuit (e.g., an ECU of a vehicle) provided outside the engine room via a wiring member extending from the sensor, and is used for various controls of the engine.

[0004]

However, in general, the impedance of piezoelectric ceramics is extremely high, from several hundred KΩ to several tens of MΩ, so that the electric charge generated from the piezoelectric ceramics in the combustion pressure sensor is limited to dust, water, or condensation. For example, it easily leaks to the case or other wiring. Therefore, the output signal from the combustion pressure sensor is significantly divided on the way to the external circuit, and as a result, the output signal is attenuated.

In the combustion pressure sensor, the output signal is extremely weak due to the characteristics of the piezoelectric ceramics.
It is necessary to minimize the attenuation of the output signal, and it is necessary to consider the electrical noise resistance of the input signal (output signal from the combustion pressure sensor) reaching the external circuit.

Heretofore, conventionally, an amplifying means is provided near an external circuit provided outside the engine room, and the amplifying means amplifies an output signal from the sensor. Wiring from the sensor to the amplifying means is provided. The member is long (for example, 1 m
.About.2 m), electrical noise is likely to be added to the weak output signal of the sensor.

Incidentally, from the viewpoint of resistance to electric noise, computerization of diesel engines has recently been advanced,
In particular, injectors for fuel injection are no exception, and electromagneticization is rapidly being introduced. As a result, for example, in the injector close to the combustion pressure sensor, a current of as much as tens of amperes flows, a wire parallel running noise accompanying a current change at the time of its operation, or a relay contact noise generated from a head lamp or a hazard lamp, Electric noise sources are scattered everywhere, such as inductive noise from the outside, and it goes without saying that it is necessary to take measures against electric noise for the output signal of the sensor.

[0008] Such a problem is caused not only by a glow plug with a combustion pressure sensor but also by a structure (for example, a spark plug, an injector, a bolt, etc.) attached to an engine provided in an engine room, and the structure. It is considered that a common problem occurs in a combustion pressure sensor structure including a combustion pressure sensor attached to a body and converting a combustion pressure of an engine into an electric signal.

In view of the above problems, the present invention has a combustion pressure sensor structure including a structure attached to an engine, and a combustion pressure sensor attached to the structure and converting a combustion pressure of the engine into an electric signal. It is an object of the present invention to suppress the attenuation of an output signal of a combustion pressure sensor and to reduce electric noise for the output signal.

[0010]

The present inventors have focused on amplifying the output signal of the combustion pressure sensor near the sensor and have come up with a means for solving the above-mentioned object. That is, according to the first aspect of the present invention, a wiring member (500) having one end electrically connected to the piezoelectric element (321) of the combustion pressure sensor (300) is provided on the other end of the wiring member. Connector (4) for making an electrical connection to the circuit
00), and an amplifying means (410) for amplifying an electric signal from the piezoelectric element is built in the connector.

According to the present invention, the amplifying means for amplifying the electric signal (output signal of the combustion pressure sensor) from the piezoelectric element can be arranged in the engine room together with the connector. Therefore, the output signal of the combustion pressure sensor can be amplified in the vicinity of the sensor, and the length of the wiring member from the combustion pressure sensor to the amplifying means can be shorter than before. Thus, according to the present invention,
It is possible to suppress the attenuation of the output signal of the combustion pressure sensor and reduce the electrical noise with respect to the output signal.

According to the second aspect of the present invention, the combustion pressure sensor (600) and the amplifying means (410) for amplifying the electric signal from the piezoelectric element (321) are molded with resin and integrated and built in. It is characterized by:

Since the amplification means is built in the combustion pressure sensor itself, the output signal of the combustion pressure sensor is amplified in the sensor, so that the output signal of the sensor can be suppressed from being attenuated. Since a wiring member for connecting the sensor and the amplifying unit is not required, electric noise with respect to the output signal can be reduced.

According to the third aspect of the present invention, there is provided a wiring member (500) having one end electrically connected to the piezoelectric element (321) of the combustion pressure sensor (300) and the other end of the wiring member. And a connector (400a) for making an electrical connection to an external circuit, and an amplifying means (4) for amplifying an electric signal from the piezoelectric element at an intermediate portion of the wiring member.
10) is interposed and set.

According to the present invention, the amplifying means can be arranged in the engine room, and the output signal of the combustion pressure sensor can be amplified near the sensor. Electrical noise with respect to the output signal can be reduced.

According to a fourth aspect of the present invention, the wiring member (500) according to the first or third aspect is electrically shielded by an electrically shielded covering member (503). According to a fifth aspect of the present invention, there is provided the amplifying means (410) according to the above inventions.
Is electrically shielded. With such a configuration as in the inventions of claims 4 and 5, it is possible to make it more difficult for electric noise to be applied to an electric signal (output signal of the combustion pressure sensor) from the piezoelectric element.

In the invention according to claim 6, the amplifying means (4
10) is molded with resin (413, 611), and the waterproofing and dustproofing of the amplifying means are ensured, so that the leak can be prevented and the attenuation of the output signal of the combustion pressure sensor is higher. It can be suppressed at the level.

In the invention according to claim 7, the amplifying means (4
10) a filter circuit (416, 41) for removing electrical noise in the electrical signal from the piezoelectric element (321).
The feature (7) is provided, and electric noise with respect to the electric signal (output signal of the combustion pressure sensor) from the piezoelectric element can be effectively removed.

According to the first and third aspects of the present invention, the connector (400) and the amplifying means (41) are respectively provided.
0), a mounting portion (42) that can be mounted in the engine room.
By providing 6), the connector and the amplifying means can be easily mounted in the engine room.

The reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment)
The combustion pressure sensor structure of the present invention will be described as being embodied in a glow plug with a combustion pressure sensor. FIG. 1 shows a glow plug 100 with a combustion pressure sensor according to a first embodiment.
FIG. 1 is a partial longitudinal sectional view showing an overall outline of a diesel engine mounted on an engine head (mounted portion of an internal combustion engine according to the present invention) 1 of a diesel engine.

The glow plug 100 has a plug body (structure in the present invention) 200 having a heating element and serving as a medium for transmitting combustion pressure, and acts on the plug body 200 according to the combustion pressure of the engine. A combustion pressure sensor 300, which is a means for converting a force (strain displacement of the plug body) into an electric signal based on the piezoelectric characteristics of the piezoelectric element, and an amplifying means for amplifying the electric signal from the piezoelectric element, have an external circuit (a In the embodiment, a connector 400 that can be electrically connected to an ECU of a vehicle) and a lead wire 500 as a wiring member that electrically connects the connector 400 and the combustion pressure sensor 300.
And is provided.

The engine head 1 is formed with screw holes (glow holes) penetrating from the outer surface to the internal combustion chamber 1a for each cylinder. In the axial direction (longitudinal direction). The plug main body 200 has a hollow pipe-shaped housing 201 made of metal, and is screwed and fixed to a screw hole of the engine head 1 with a mounting screw 201a formed on an outer peripheral surface thereof.

The plug body (structure) 200 is a hollow pipe-shaped sheath tube 20 held in a housing 201.
2 is provided. The sheath tube 202 is made of a heat-resistant and corrosion-resistant alloy (for example, stainless steel SUS310 or the like), and has a closed end (lower side in FIG. 1) and an open other end (upper side in FIG. 1). A heating coil 203 made of a resistance wire such as NiCr and CoFe is provided inside the distal end of the sheath tube 202, and one end of a metal rod-shaped center shaft 204 is partially inserted into the other end of the sheath tube 202. It is arranged in the form.

One end of the heating coil 203 is connected to a sheath tube 202.
And the other end of the heating coil 203 is connected to the center shaft 20.
4 at one end. A space between the heating coil 203 and the central shaft 204 and the sheath tube 202 is filled with insulating powder 205 having heat resistance, such as magnesium oxide.

The sheath tube 202 is subjected to a drawing process by swaging, whereby the denseness of the insulating powder 205 filled therein is improved, and the sheath tube 202, the central shaft 204 and the center tube 204 are interposed via the insulating powder 205. The heating coil 203 is firmly held and fixed.

Here, in a portion of the sheath tube 202 including the heating coil 203, the sheath tube 20
2. A heating element 206 is constituted by the heating coil 203 and the insulating powder 205. And the heating element 206
The distal end (the distal end of the sheath tube 202) is joined and held inside the housing 201 so that the distal end is exposed. Heating element 206 (outer peripheral surface of sheath tube 202) and housing 2
Bonding with the fixing member 01 can be performed by fixing by press fitting or brazing such as silver brazing.

Further, inside the upper end side of the housing 201, a washer 20 made of an insulating bakelite material is provided.
7. O-ring 208 made of silicon or fluoro rubber
Are inserted and arranged on the center shaft 204. Here, the washer 207 is for centering the center shaft 204,
The ring 208 is for ensuring waterproofness and airtightness inside the housing 201.

The center shaft 204 is connected to the center shaft 2 via an insulating bush 209 made of an insulating resin such as phenol.
It is fixed to the housing 201 by a fixing nut 210 along a terminal screw 204a provided on the housing 04. Here, the insulating bush 209 is connected to the center shaft 204 and the housing 20.
It also has a function of preventing short-circuit due to contact with 1.

The connecting bar 2 is fixed and electrically connected to a terminal screw 204a provided on the other end side of the center shaft 204 by a terminal nut 211. This connecting bar 2 is connected to a power source (not shown),
It is grounded to the engine head 1 via the center shaft 204, the heating coil 203, the sheath tube 202, and the housing 201. As a result, the heating element 206 generates heat in the glow plug 100, and can assist ignition start of the diesel engine.

The heating element 206 may be, for example, a heating element made of conductive ceramics containing silicon nitride and molybdenum silicide in addition to a so-called metal heating element based on the above-described metal resistance wire. A so-called ceramic heating element may be used, which is sintered so as to be included in an insulator made of insulating ceramic as a component.

Next, the combustion pressure sensor 300 has a substantially ring shape as a whole. As shown in FIG. 1, a portion of the plug body (structure) 200 protruding in the axial direction from the surface of the engine head 1 is formed. Are fixed to the outer peripheral surface of the protruding portion and are arranged so as to contact the surface of the engine head 1. 2A and 2B are enlarged views showing details of the combustion pressure sensor (pressure sensor) 300 in FIG. 1, wherein FIG. 2A is a longitudinal sectional view, and FIG. .

The combustion pressure sensor 300 is roughly divided into a nut (sensor fixing portion) 310 for attaching the sensor main body to the plug main body (structure) 200 and an electric signal (charge) according to a force accompanying the combustion pressure. Generated piezoelectric element section 320
And a lead 330 for taking out an electric signal generated by the piezoelectric element 320 and guiding it to the lead wire 500, and a pedestal for holding the piezoelectric element 320 together with the nut 310 and fixing a part of the lead 330. 340 and a metal case 35 for dustproofing and waterproofing the piezoelectric element section 320.
0.

First, the nut 310 and the lead 330 will be described. The nut 310 is made of metal, and is provided with a mounting screw 2 provided on the housing 201 of the plug body 200.
A screw portion 311 and a hexagonal portion 312 for mounting and fixing the sensor main body via 01a are fixed to the outer periphery of the housing 201. A large-diameter portion 313 and a small-diameter portion 314 are sequentially formed below the hexagonal portion 312, and a heat-shrinkable insulating tube 315 made of silicon is tightly fixed to the outer peripheral surface of the small-diameter portion 314. .

The lead portion 330 is a portion for electrically connecting the piezoelectric element portion 320 and one end of the lead wire 500. The electrode 330, the insulator 332, the fixture 333, and one end of the lead wire 500 are connected to each other. It is provided as a component.

The electrode 331 is annular and made of metal.
The insulator 332 includes the electrode 331 and the nut 310.
And insulates both 331 and 310 from each other, and is made of an insulating material such as mica or alumina in a ring shape. These electrode 331 and insulator 33
2 is fitted on the outer edge of the small diameter portion 314 of the nut 310 covered with the insulating tube 315.

Here, the lead wire 500 extends from the innermost part to the outermost part, and has a conductive signal output line 501, an insulating insulating coating 502, a conductive ground side shield line 503,
It has a configuration in which insulating insulating coatings 504 are sequentially laminated, and the signal extraction line 501 and the ground side shield line 503 are electrically insulated. As shown in FIG. 2, the lead wire 500 has a configuration in which a signal extraction wire 501, an insulating coating 502, and a ground-side shield wire 503 are partially exposed at one end side in this order from the front end.

At one end of the lead wire 500, a signal extraction wire 501 is connected to a hole 316 formed in the nut 310.
Notch 332 formed in insulator 332
a, it is welded and connected to the electrode 331 at a hole 331a formed in the electrode 331. In addition, lead wire 5
The other end of 00 is connected to a connector 400 as shown in FIG.

The fixing bracket 333 is connected to the lead wire 500.
Is fixed to the nut 310 and has a hollow pipe shape, and is provided on the outer periphery of one end of the lead wire 500. Here, an upper portion of the hole 316 formed in the nut 310 is configured as a fixing bracket holding hole 316 a for holding the fixing bracket 333, and the holding hole 31.
A part of the fixture 333 is inserted and fixed to 6a.

The fixing member 333 is caulked and fixed to the lead wire 500, and the earth side shield wire 503 and the fixing member 333 are electrically connected. The outer periphery of the fixing bracket 333 protruding from the fixing bracket holding hole 316a is covered with a heat-shrinkable insulating coating 333a made of silicon.

Next, the piezoelectric element portion 320 has a hollow portion having an annular shape corresponding to the small diameter portion 314 of the nut 310,
Like the electrode 331, it is disposed along the outer peripheral surface of the small diameter portion 314 via the insulating tube 315. Here, FIG. 3 shows a detailed explanatory view of the piezoelectric element section 320.
In FIG. 3, (a) shows the washer 32 on the signal extraction side.
2 is a perspective view of a single unit, and FIG.

As shown in FIG. 3B, the piezoelectric element 320
Is a three-layer piezoelectric ceramic (piezoelectric element in the present invention)
321 is combined with a signal extraction side washer ring 322 and a ground side washer ring 323 to form a laminated structure. Each piezoelectric ceramic 321 has a disk ring shape of the same dimensions and is made of lead titanate, lead zirconate titanate, or the like.

Also, the signal extraction side washer ring 322
As shown in FIG. 3 (a), the same thin metal plates 322a and 322b having a thin annular shape are arranged in two upper and lower portions, and at least a part thereof is pressed by press working so as to be joined by the outer peripheral side surface portion 322c. It was produced.

The ground side washer ring 323 is also
As shown in FIGS. 3B and 2A, the signal extraction washer ring 322 and the same metal plate 323a, 323b are manufactured by the same shape and manufacturing method.
Are arranged in two upper and lower sheets, and at least a part thereof is connected by an outer peripheral side surface portion 323c (see FIG. 2A).

In the piezoelectric element section 320, as shown in FIG. 3B, a metal plate 322a, a piezoelectric ceramic 321, a metal plate 323a, a piezoelectric ceramic 321,
Metal plate 322b, piezoelectric ceramic 321, metal plate 32
In the order of 3b, the outer peripheral side surfaces 322c and 323c of the both washer rings 322, 323 are arranged in a laminated manner so as not to come into contact with each other.

Next, together with the nut 310, the piezoelectric element 3
A pedestal 340 for holding the lead 20 and fixing a part of the lead portion 330 has a substantially annular shape made of metal. The pedestal 340 is provided on the end surface on the contact side with the engine head 1 as shown in FIG.
As shown in (b), it corresponds to the oval detent 317 formed at the end of the small diameter portion 314 of the nut 310, and
A similar oval-shaped stopper 341 that can be easily fitted to the stopper 317 is formed.

The outer edge of the base 340 is, for example, SU
A metal cylindrical metal case 350 made of S304 is provided, and the metal case 350 covers the entire outer periphery of the combustion pressure sensor 300. The metal case 350 is made by drawing a thin metal plate having a thickness of 0.5 mm or less into a cylindrical shape, and is joined to the pedestal 340 by laser welding or brazing such as copper brazing. .

In the pedestal 340 integrated with the metal case 350, the rotation stopper 341 and the rotation stopper 317 of the nut 310 exactly face each other.
Further, the inner diameter portion 342 of the pedestal 340 and the O-ring 343 made of silicon or fluoro rubber fitted and fitted in a notch groove provided near the center of the small diameter portion 314 of the nut 310 are both in close contact. .

The metal case 350 has a nut 310
Of the metal case 350 and the large-diameter portion 313 of the nut 310 are joined all around by YAG laser welding.

In this way, the base 340 is pressed against the surface of the engine head 1 by the axial force (screw tightening force) of the nut 310. And the piezoelectric element section 3
20, the electrode 331 and the insulator 332 are interposed and fixed between the nut 310 and the pedestal 340 by the axial force of the nut 310.

The method of assembling the combustion pressure sensor 300 is as follows.
It is as follows. First, at one end of the lead wire 500, the signal extraction line 501 is welded to the hole 331a of the electrode 331. Further, the fixing bracket 333 is fitted into the fixing bracket holding hole 316a of the nut 310, and joined by welding or brazing such as a copper brazing. Further, the insulator 332 is attached to the small diameter portion 314 of the nut 310.

The fixing bracket 333 and the insulator 3
32 is attached to the nut 310 to which the lead wire 50 is attached.
The electrode 331 to which one end of the lead wire 500 is connected is fitted into the small-diameter portion 314 of the nut 310 while the other end of 0 is inserted into the hole 316 from the insulator 332 side.
After disposing the electrode 331 at a predetermined position, the fixing bracket 333,
The ground-side shield wire 503 is simultaneously caulked and fixed.

After that, a part of the lead wire 500 and the fixing bracket 333 are covered with an insulating coating 333a to achieve dustproof and waterproof. As a result, the ground-side shield wire 503 and the fixture 333 are also electrically connected.

Next, a piezoelectric element section 320 comprising a piezoelectric ceramic 321 and both washer rings 322 and 323
Into the small diameter portion 314 of the nut 310. And
The pedestal 340 integrated with the metal case 350 by brazing or the like is inserted into the small-diameter portion 314 of the nut 310, and the swivel bearing 317 and the swivel stopper 341 are aligned. Then, the metal case 350 and the large-diameter portion 313 of the nut are laser-welded in a state where the pedestal 340 and the nut 310 are pressed so as to be in close contact with each other.

Thus, the combustion pressure sensor 300 is completed. The combustion pressure sensor 300 is inserted into the plug main body 200 from the heating element 206 side, and the mounting screw 201a of the housing 201 and the nut 3 are positioned at predetermined positions.
Attachment is performed by screwing with ten screw portions 311 and hexagonal portions 312.

The combustion pressure sensor 300 includes the combustion chamber 1a
Plug body (structure) 20 due to the generation of combustion pressure in the chamber
The force applied to zero (load variation in the plug axis direction) is converted into an electric signal (charge) based on the piezoelectric characteristics of the piezoelectric element section 320. This electric signal is sent from the lead wire 500 to the connector 400. Here, the combustion pressure sensor 300 has several features as follows.

The first feature is shown in FIG. 4, which shows the direction of the electrode surface of the piezoelectric ceramic 321 polarized positively and negatively when the constituent elements are arranged in a stack in the piezoelectric element portion 320. , The signal extraction washer 32
2 is that the electrode surface on the side that contacts the ground side washer ring 323 is positive, and the electrode surface on the side that contacts the washer ring 323 is negative. As a result, the three piezoelectric ceramics 321 are electrically connected in parallel, and the output sensitivities of the three piezoelectric ceramics 321 are added up, so that the sensitivity can be greatly improved.

The second feature is that the rotation stopper 317 of the nut 310 and the rotation stopper 341 of the pedestal 340 rotate the combustion pressure sensor 300 via the mounting screw 201 a provided on the housing 201 of the plug body 200. In the case of mounting, it plays a role of directly transmitting the rotation axial force of the nut 310 to the pedestal 340.

As a result, first, the laser welding portion between the metal case 350 and the nut 310 made of a thin metal plate having a thickness of 0.5 mm or less and the brazing portion with the pedestal 340 generate excessive torsional stress and shear stress. , And damage to these joints and the metal case 350 can be prevented.

Further, since the nut 310 and the pedestal 340 rotate in conjunction with each other, there is no disconnection of the signal extraction line 501 connected to the electrode 331, and the insulator 332 and the insulator 332 sandwiching both of them are connected. Ceramics 321
With regard to (1), since the torsional stress, which is the largest factor of crack generation, is not applied, cracks can be prevented.

The third feature is that in the metal case 350, the spring constant (Kg / mm), which is an index of rigidity, is minimized by reducing the thickness of the metal case 350 to 0.5 mm or less. Thereby, the piezoelectric ceramics 32 associated with the combustion pressure
A minute change in the axial direction of the plug acting on the plug 1 can be reliably transmitted without being restrained or suppressed by the metal case 350.

The fourth feature is that the piezoelectric ceramic 321 as a signal source and the signal output line 501 as a signal transmission path are connected to the nut 31 grounded to the engine head 1.
0, the metal case 350, the pedestal 340, the ground-side shielded wire 503, and the fixing bracket 333. Accordingly, it is possible to provide the combustion pressure sensor 300 that blocks external electric noise and has extremely high resistance to electric noise.

The fifth feature is that in the small space between the pedestal 340 and the nut 310 that are not metallically joined, the O-ring 343 is used, and the lead wire that is caulked and fixed via the fixing bracket 333. In 500, a heat-shrinkable insulating coating 333a made of silicon is used to achieve complete sealing from the outside. As a result, it is possible to provide the combustion pressure sensor 300 having extremely high waterproof and dustproof properties.

A sixth feature is that when assembling the metal case 350 integrated with the pedestal 340 to the large diameter portion 313 of the nut 310, at least one of the nut 310 or the pedestal 340 is fixed, and the insulator 332 and the electrode 33 are fixed.
1. Piezoelectric ceramic 321 and both washers 3
That is, the laser welding is performed in a state where the pressures 22, 22 are pressed. This makes it possible to significantly compress and narrow the minute space generated by the superposition of a plurality of parts, and to more minutely detect minute displacement due to the combustion pressure.

Next, the connector 400 provided at the other end of the lead wire 500 and incorporating the amplifying means will be described. FIG. 5A is an overall sectional view of the connector 400, and FIG.
FIG. This connector 400
It has a metal cover 420 that houses a charge amplifier 410 as an amplifying means of the present invention. This metal cover 4
Reference numeral 20 denotes a hollow pipe having a different diameter, and is manufactured by drawing a metal plate.

The small diameter opening 421 of the metal cover 420
A metal-made, hollow-pipe-shaped fixture 422 is fitted from the outside. This fixture 422 is
Is joined to the end of the metal cover 420 by welding or brazing such as copper brazing through a flange 422a provided in the metal cover 420.

On the other hand, the large-diameter opening 423 of the metal cover 420
A metal cap 424 in a brim-like (flange-like) shape is fitted in the. Part of the metal cap 424 is inscribed in the inner edge of the large-diameter opening 423 so that the position can be fixed.
a is formed.

The other end of the lead wire 500 penetrates through the hollow hole of the fixture 422 and faces the inside of the metal cover 420. The lead wire 500 is arranged on the other end side in the same manner as the above-described one end side, in order from the tip end, to the signal extraction line 501,
The insulation coating 502 and the ground-side shield wire 503 are partially exposed.

At the other end of the lead wire 500, the insulating cover 504 and the earth-side shield wire 503 are simultaneously caulked and fixed via the fixture 422, so that the earth-side shield wire 503 and the fixture 422 are separated from each other. It is electrically connected.

The charge amplifier 410 is an IC chip using a silicon chip or the like. The charge amplifier 410 has an input terminal 411 and an output terminal 412 including three terminals of signal output, GND, and power supply. Molded. Here, as the resin 413, for example, a thermoplastic resin such as polyphenylene sulfide (PPS), nylon, or polybutylene terephthalate (PBT), or
Silicon potting agent can be adopted.

The input terminal 4 of the charge amplifier 410
Numeral 11 is connected to the signal extraction wire 501 of the lead wire 500 penetrating into the hollow hole of the fixing bracket 422 by welding via an input terminal 411. Meanwhile, charge amplifier 4
10 through the terminal through hole 424 a formed in the metal cap 424.
It is drawn out of 0.

Here, the charge amplifier (amplifying means) 41
FIG. 6 shows a circuit configuration of 0. The charge amplifier 410
At least a charge amplifying / voltage converting circuit 414 for amplifying the charge from the piezoelectric element section 320 and converting it to a voltage, and an amplifier circuit 415 for amplifying the voltage from the charge amplifying / voltage converting circuit 414 are provided. In the present embodiment, the charge amplifier 410 further includes a high-pass filter 416 of, for example, 0.5 Hz between the two circuits 414 and 415, and a low-pass filter 417 of, for example, 5 KHz at a stage subsequent to the amplifier circuit 415.

Note that a gain adjustment and offset adjustment circuit, which is a correction circuit, may be set in the amplification circuit 415 as necessary. Further, instead of making the high-pass filter 416 and the low-pass filter 417 independent, a band-pass filter may be used. In this case, the amplification circuit 415
It is desirable to place it before.

In the charge amplifier 410 having the amplifying circuit 415, for example, when performing combustion control, an electric signal from the piezoelectric element section 320 of the combustion pressure sensor 300 is used.
It is possible to amplify and convert to an operating voltage of 0 to 3.5 V that can be directly input into an ECU (external circuit).

The built-in high-pass filter 416 allows drift of a low-frequency pyroelectric output (so-called base voltage) of 0.1 Hz to several tens Hz, which is peculiar to piezoelectric ceramics and is caused by a temperature change. For example, several KH such as the natural vibration of the glow plug and the nozzle seating vibration when the injector operates.
Electrical and mechanical vibration noise such as high-frequency mechanical vibration of z to several tens KHz can be removed.

The large-diameter opening 423 of the metal cover 420
The metal cap 424 is covered with a cap-shaped connector 425 made of, for example, PPS, nylon, PBT, or the like. This connector 425 is connected to the connector 425 shown in FIG.
As shown in the figure, the output terminals 4 of the three charge amplifiers 410
12 are formed so as to be exposed so that other wiring members (not shown) extending from the ECU can be connected thereto.

A stay (attachment portion in the present invention) 426 having a screw hole is joined to the metal cover 420 by welding or the like.
00 is mounted and fixed at an appropriate place in the engine room. A notch groove 427 is formed in a portion of the outer peripheral side surface of the metal cover 420 which is covered by the connector portion 425, and the notch groove 427 and the connector portion 4 are formed.
The hooking of the connector portion 425 enhances the tensile strength in the axial direction and prevents the connector portion 425 from rotating.

The connector 400 is formed as follows. First, lead wires 50 are placed inside metal cover 420.
0 is connected to the charge amplifier 410, and the metal cap 424 is matched with the metal cover 420. In this state, the output terminal 412 is placed and fixed in an injection mold for forming the connector portion 425, and further, in order to prevent contact between the output terminal 412 and the metal cap 424 and to fix the position, the output terminal 412 is provided with an injection core. Hold and fix with a mold.

Then, for example, PPS, nylon, PB
The connector portion 425 is formed by injecting a thermoplastic resin such as T into an injection mold and performing injection molding. At this time, the resin 41 is inserted through the terminal through hole 424a of the metal cap 424.
3 is filled in the metal cover 420, and the charge amplifier 410 is simultaneously molded. As described above, the resin filling into the metal cover 420 and the output terminal 4 are performed in a single process.
12 can be held and fixed, and the connector portion 425 can be formed.

As a result, the charge amplifier 410 formed into an IC chip and molded with a resin is connected to the signal output line 501.
And the resin molding is performed again, and the dustproof / waterproof effect is greatly improved. In addition, the charge amplifier 410
Is entirely covered by a grounded metal cover 420, a metal cap 424, a fixing bracket 422, and the like, so that electrical noise resistance can be secured.

As described above, the glow plug 100 of the present embodiment includes the plug body 200, the combustion pressure sensor 300,
It comprises a connector 400 and a lead wire 500. Next, the mechanism of detecting the combustion pressure in the glow plug 100 will be described throughout.

The plug body 200 of the glow plug 100 is mounted in a screw hole (glow hole) provided in the engine head 1, and the combustion pressure sensor 300 is
The plug main body 200 is mounted so that a load is applied to the piezoelectric ceramics 321 of the piezoelectric element portion 320 in the axial direction of the plug via the mounting screw 201a of the housing 201.
It is attached to.

When the diesel engine is started, a voltage is applied from a power source (not shown) to the plug main body 200 via the connecting bar 2, and the engine head 1 is connected via the center shaft 204, the heat generating coil 203, the sheath tube 202, and the housing 201. Grounded. Thereby, the heating element 2
06 generates heat and can assist ignition start of the diesel engine. After the engine is started, the combustion pressure generated in the engine depends on the heating element 206 and the housing 201.
To the mounting screw 201a.

Subsequently, the combustion pressure transmitted to the mounting screw 201a reduces the tightening torque of the glow plug 100 on the engine head 1. Accordingly, the load applied to the piezoelectric ceramics 321 via the screw portion 311 of the nut 310 in the combustion pressure sensor 300 is reduced (that is, the load applied to the piezoelectric ceramics 321 changes). Ceramics 32
The generated charge of the electric signal output according to the piezoelectric characteristic of 1 changes.

The signal is output from a signal extraction side washer ring 322, a signal extraction line 501 via an electrode 331, and a grounded washer ring 323, a pedestal 340, a housing 201, a mounting screw 201a, and a screw portion. The signal is output to the ground side shield line 503 via the line 311.

Then, the output signal is input to the charge amplifier 410 of the connector 400 connected via the lead wire 500. The input signal is sequentially processed by the charge amplification / voltage conversion circuit 414, the high-pass filter 416, the amplification circuit 415, and the low-pass filter 417, and then input from the output terminal 412 of the charge amplifier 410 to the ECU. As an electric signal,
For example, it is applied to combustion control. The above is the entire mechanism of detecting the combustion pressure in the glow plug 100.

According to the glow plug having the connector with a built-in charge amplifier as in the present embodiment, the connector 400 amplifies the electric signal (output signal of the combustion pressure sensor 300) from the piezoelectric ceramic 321 (the output signal of the combustion pressure sensor 300). Amplifying means) 410 is incorporated. Therefore, the charge amplifier 410 and the connector 400 can be arranged in the engine room near the combustion pressure sensor 300 (for example, in an engine head or a head cover).

As a result, the output signal of the combustion pressure sensor 300 can be amplified in the vicinity of the sensor 300, and the lead (wiring member) 500 connecting the combustion pressure sensor 300 and the charge amplifier 410 is also different from the conventional one. The length can be minimized (for example, 30 cm or less), the electrostatic stray capacitance of the lead wire 500 can be reduced, and the attenuation of the output signal can be suppressed. Therefore, according to the glow plug 100, it is possible to suppress the attenuation of the output signal of the sensor 300 and to reduce the electrical noise with respect to the output signal.

In this embodiment, the lead wire 500
Are shielded electrically by a grounded shield wire (covering member according to the present invention) 503, and the ground shield wire 503 and the metal cover 4 are further shielded.
It is assumed that the charge amplifier 410 is also electrically shielded via the device 20 and the like. Therefore, electric noise is less likely to be applied to the electric signal (output signal of the combustion pressure sensor 300) from the piezoelectric ceramic 321.

Further, according to the present embodiment, since the charge amplifier 410 is molded with the resin 413, the connector 400 can be miniaturized, and the charge amplifier 410 and the connector 400 can be integrated. A waterproof and dustproof structure can be realized. Therefore, dust
Leakage of the output signal of the combustion pressure sensor 300 due to water, dew condensation, or the like can be prevented, and attenuation of the output signal of the combustion pressure sensor 300 can be suppressed at a higher level.

Further, according to the present embodiment, the charge amplifier 410 is provided with a filter circuit for removing electric noise in the electric signal from the piezoelectric ceramic 321 as a filter circuit.
A high-pass filter 416 and a low-pass filter 417 are provided.
1 can effectively remove electrical noise from the electrical signal (output signal of the combustion pressure sensor).

As a result, the charge amplifier 410
The input signal from the ECU to the ECU can be a combustion pressure signal having an extremely excellent S / N ratio. Further, the above noise signal peculiar to the glow plug with a combustion pressure sensor using piezoelectric ceramics, that is, electric and mechanical such as drift of the low frequency pyroelectric output, natural vibration of the glow plug, and nozzle seating vibration at the time of injector operation, etc. Elimination of typical vibration noise can be processed on the charge amplifier 410 side, and the general versatility of the input signal to the ECU is maintained, so that the burden of remodeling the hardware on the ECU side can be reduced.

Next, the effects of the present embodiment will be described more specifically with reference to FIGS. FIG.
8 are waveform diagrams showing test results when the engine condition is idling, FIG. 7 is a glow plug 100 with a combustion pressure sensor of the present embodiment, and FIG.
1 shows a conventional glow plug with a combustion pressure sensor mounted near an ECU in a vehicle cabin.

7 and 8, (a) is a graph showing a comparison between the output waveforms of the glow plug with the combustion pressure sensor and the acupressure meter, (b) is the output from the glow plug with the combustion pressure sensor on the vertical axis, FIG. 4 shows a correlation output waveform diagram in which the output from the acupressure meter is plotted on the horizontal axis. Here, the acupressure meter employs, for example, an in-cylinder sensor directly mounted in the combustion chamber.

As can be seen from FIG. 7, the output waveform of the glow plug 100 of this embodiment has substantially the same shape as the output waveform from the tonometer, and the correlation output waveform has substantially the same value both when the pressure rises and when the pressure decreases. And no electrical noise was detected. On the other hand, in the output waveform of the conventional device, as shown in FIG. 8, the output peak value H1 is reduced by about 20% as compared with the output peak value H2 of the acupressure meter, and the correlation output waveform also shows an ellipse.
The output waveform also has a time delay.

In the prior art, regular electric noise N1 is observed especially in the vicinity immediately before the pressure rise due to combustion (point α), that is, at the fuel injection timing of the electromagnetic injector. This electric noise N1 obscures the above-mentioned α point, and as a result, greatly affects, for example, the detection of the pressure rise value in the cylinder due to the combustion necessary for combustion control and the detection accuracy and the accuracy of the combustion start timing, and the precision. Becomes

On the other hand, according to the glow plug 100 of the present embodiment, the amplification of the output signal near the combustion pressure sensor 300, the shortening of the lead wire 500, and the
In addition, the electric shield of the charge amplifier 410 and the like can suppress the attenuation of the output signal and reduce the noise at the time of operating the injector. The combustion pressure signal from the glow plug 100 enables accurate combustion control. Becomes

Next, FIG. 9 shows a comparison between the present embodiment and a conventional glow plug with a combustion pressure sensor showing the influence of main relay contact noise caused by the operation of all 10 evaluation items such as a headlamp and a hazard lamp. It is a chart (engine conditions are idling). In FIG. 9, ○ indicates that electric noise was not observed, and × indicates that electric noise was observed.

In the present embodiment, except for the radio and door lock, the output signal from the sensor 300 can be applied to eight items requiring a relatively large current, for which electric noise has been observed in the conventional device. , No electrical noise was observed,
The effectiveness of electric noise resistance has been confirmed.

FIG. 10 is a waveform diagram showing an example of relay contact noise generated in a conventional glow plug with a combustion pressure sensor. FIG. 10A shows a headlamp ON / O.
At the time of FF, (b) shows an example of the influence on the output signal of the sensor when the hazard lamp blinks. Here, the reason for taking up the relay contact noise as a problem is that unlike the noise generated when the injector is operated, it is generated accidentally (that is, it is unexpected noise).

In FIG. 10B, when the hazard lamp flickers, the electric noise N3 is generated at a position away from the peak value of the pressure increase due to combustion. However, in FIG. 10A, the head lamp is turned on. At the time of / OFF, the electric noise N2 is accidentally generated near the peak value of the pressure rise accompanying the combustion.

For this reason, for example, in the combustion control, if the peak value of the pressure rise using the peak hold circuit is calculated, the result will be a value obtained by adding the generated noise to the actual value. Value is determined to be extremely large, the fuel injection amount is reduced, or EGR
Attempts to increase the amount to reduce the combustion pressure to the target combustion pressure.

As a result, irregularities such as a sudden decrease in engine output and fluctuations in rotation occur, and the driver feels discomfort such as shock and engine vibration. From such a viewpoint, it is indispensable to improve the S / N ratio by removing electric noise from the output signal, and according to the present embodiment, these problems can be prevented.

Next, FIG. 11 is a waveform chart showing the effect of removing the mechanical and electrical noise signals by the low-pass filter 417 of this embodiment. FIG. 11 shows the test results when the engine condition is 2000 rpm and the load is full.
(A) is an output waveform comparison diagram between a conventional glow plug with a combustion pressure sensor without a low-pass filter and a pressure gauge,
(B) is the present embodiment, and shows a comparison diagram of output waveforms with a 5 KHz low-pass filter 417 interposed therebetween. As can be seen from this figure, the intervening low-pass filter 417 eliminates high-frequency mechanical vibration noise from the surroundings of the engine that is continuously generated.

Next, the effect of removing the mechanical and electrical noise signals by the high-pass filter 416 will be described with reference to FIGS. FIG. 12 is a comparison diagram of output waveforms when 64 outputs of the conventional glow plug with a combustion pressure sensor without a high-pass filter and the acupressure meter are continuously taken in, and (a) shows a case where the engine condition is idling. ,
(B) shows the test results when the engine condition is 1200 rpm and the load is 40 N · m.

Due to the pyroelectric output peculiar to piezoelectric ceramics, the drift width of the output base voltage in the conventional glow plug with a combustion pressure sensor is
It can be seen that the value is significantly higher than that of the tonometer.

FIG. 13 shows a case where the set frequency of the interposed high-pass filter 416 in this embodiment is changed (0.
(1 Hz, 0.5 Hz) is a numerical comparison of the drift width with the acupressure meter using the combustion pressure peak ratio.
The combustion pressure peak ratio referred to here is a continuous combustion pressure output 6
The four waveforms show the ratio of the combustion pressure peak value to the maximum drift width, and the smaller the value, the better.

For example, when the drift width D and the combustion pressure peak value P shown in FIG. 12A are used and the maximum value of the drift width D is Dmax, the combustion pressure peak ratio becomes (Dmax
/ P) × 100. In FIG. 13, for comparison, a conventional glow plug with a combustion pressure sensor,
That is, the combustion pressure peak ratio without the high-pass filter is also shown.

As a result, with the interposition of the 0.5 Hz high-pass filter 416, the drift width becomes 1/4 to 1 of the conventional one.
/ 5, and as can be seen from FIG. 13, the combustion pressure peak ratio shows almost the same value as that of the acupressure meter. As described above, in the present embodiment, with the intervention of the high-pass filter 416,
Noise due to the low frequency pyroelectric output specific to piezoelectric ceramics can be removed.

(Second Embodiment) In the second embodiment, the plug main body 200 has the same structure as that of the first embodiment, but the lead wire is eliminated, and the combustion pressure sensor itself and the piezoelectric element are separated. The difference is that a charge amplifier (amplifying means) 410 for amplifying an electric signal from the ceramics (piezoelectric element) 321 is molded with resin, and is integrated and incorporated.

FIG. 14 is a detailed enlarged view of the combustion pressure sensor 600 in the glow plug 100 with a combustion pressure sensor according to the present embodiment, in which (a) is a longitudinal section, and (b) is C in (a).
FIG. In the drawings, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description will be simplified.

The combustion pressure sensor 600 according to the present embodiment is roughly divided into a sensor fixing portion 310 for attaching the sensor main body to the plug main body 200, and a piezoelectric member for generating an electric signal (charge) according to a force accompanying the combustion pressure. Ceramics 321;
An electrode 331 for extracting an electric signal generated by the piezoelectric ceramic 321, a pedestal 340 for holding the piezoelectric ceramic 321 and the electrode 331 together with the sensor fixing portion 310, and a metal for dustproof and waterproof the piezoelectric ceramic 321. Case section 350 and connector section 61 containing charge amplifier 410 connected to electrode 331
0.

The sensor fixing portion 310 of the present embodiment is different from a fixing nut 318 for mounting and fixing the sensor main body via a mounting screw 201a provided on the housing 201 of the plug main body 200. It is a body and includes a pressing portion 319 as a portion for pressing down the piezoelectric ceramic 321 and the electrode 331 by the axial force of the fixing nut 318.

The fixing nut 318 has the same configuration as the hexagonal portion 312 of the nut 310 in the first embodiment.
The holding portion 319 corresponds to a portion of the nut 310 except for the hexagonal portion 312, and has a large diameter portion 313 and a small diameter portion 314. However, unlike the first embodiment, holes for guiding the lead wires are not formed in the fixing nut 318 and the pressing portion 319.

Further, no screw portion is formed on the inner peripheral surface of the holding portion 319, and the holding portion 319 is freely rotatable around the axis of the housing 201. Also,
An insulating tube 315 is tightly fixed to the outer peripheral surface of the small diameter portion 314 of the holding portion 319.

A pair of annular piezoelectric ceramics 321 is
A laminated structure is formed with the annular electrode 331 interposed therebetween. This laminate is fitted into the outer edge of the small diameter portion 314 of the holding portion 319 covered with the insulating tube 315,
The holding portion 319 is sandwiched between the large-diameter portion 313 and the pedestal 340 by an axial force of 18. Then, the input terminal 411 of the charge amplifier 410 is welded and connected to a hole formed on the outer peripheral side surface of the electrode 331 through a slit or a hole formed in the metal case 350.

The connector section 610 is molded with a resin 611 so as to surround the charge amplifier 410, the metal case 350, and the base 340 connected to the electrode 331. Charge amplifier 410 in connector section 610
The output terminal 412 has a shape that allows another wiring member (not shown) extending from the ECU to be connected to the output terminal 412. And the connector part 610 is provided with the fixing nut 3.
When the tightening is not performed at 18, the housing 2 is integrated with the other parts of the sensor except the fixing nut 318.
01 is freely rotatable around the axis.

The combustion pressure sensor 600 is mounted on the plug main body 200 such that a load is applied to the piezoelectric ceramic 321 in the axial direction of the plug via the mounting screw 201a of the housing 201.

Since the load applied to the piezoelectric ceramic 321 via the fixing nut 318 of the combustion pressure sensor 600 is reduced by the combustion pressure transmitted to the mounting screw 201a, the piezoelectric characteristics of the piezoelectric ceramic 321 are reduced. The generated charge of the electric signal output along the line changes. The output signal is input to the charge amplifier 410 via the electrode 331, subjected to signal processing, and then input from the output terminal 412 to the ECU.

According to the glow plug having the combustion amplifier with a built-in charge amplifier as in the present embodiment, the charge amplifier 410 is built in the combustion pressure sensor 600 itself. By amplifying in the sensor, attenuation of the output signal of the sensor can be suppressed.

Further, according to the present embodiment, by eliminating the lead wire connecting the sensor and the charge amplifier 410, the factor of attenuation in output sensitivity is eliminated, and the influence on line parallel noise can be reduced. Electrical noise with respect to the output signal can be reduced. However, the charge amplifier 41
The 0 input terminal 411 is simply molded with the resin 611, that is, is partially exposed to electric noise. Therefore, compared to the completely shielded first embodiment described above, The electrical noise resistance may be slightly inferior.

Further, the combustion pressure sensor 600 of the present embodiment
If there is enough space for mounting the combustion pressure sensor,
Although particularly effective, in order to further expand the range of application, the configuration is such that it can freely rotate around the axis of the housing 201 when the fixing nut 318 is not tightened.

By adopting the above rotatable configuration, the sensor 600 can be provided with a mounting direction at the time of mounting, and can be mounted only by rotating the fixing nut 318 without rotating the protruding connector portion 610. Therefore, it is possible to reduce the space required for mounting by rotation.

Further, according to the present embodiment, the holding portion 31
9, piezoelectric ceramics 321, electrodes 331, pedestal 340
By integrating the sensor portion composed of the metal case 350 and the connector portion 610 with the built-in charge amplifier 410 by injection molding of the resin 611, a reliable waterproof and dustproof structure in the charge amplifier 410 can be realized at the same time. .

As a result, it is possible to prevent the output signal of the combustion pressure sensor 600 from leaking due to dust, water, dew, or the like, and to suppress the attenuation of the output signal of the combustion pressure sensor 600 at a higher level. Furthermore, compared to the first embodiment, the total number of parts and the number of working steps can be reduced by half, and a combustion pressure sensor having a low cost and a simple structure can be provided.

Further, according to the present embodiment, since the connector with a built-in charge amplifier connected by a lead wire as in the first embodiment is eliminated, the lead wire is disconnected due to the mounting and the charge due to the impact dent is caused. The amplifier is not damaged, and on the other hand, the mounting is performed by the fixing nut 318, and the impact wrench can be used. Therefore, both the reliability and the mounting workability are further improved.

(Other Embodiments) In the first embodiment, the charge amplifier 410 having the stay (attachment portion) 426 attachable to the engine room is connected to the lead wire 5.
00 may be set in the middle of 00. Also in this case, the charge amplifier 410 can be arranged in the engine room, and the output signal of the combustion pressure sensor 300 can be amplified near the sensor, so that the attenuation of the output signal of the combustion pressure sensor is suppressed and Electrical noise can be reduced. However, in this case, as shown in FIG. 15, three lead wires 500 at the subsequent stage of the charge amplifier 410 are required to connect to the three output terminals 412 of the charge amplifier 410, and three lead wires 500 are required. Connection becomes complicated.

The charge amplifier need not be an IC chip, but may be a general circuit board having a shape and size applicable to the above embodiments. The circuit configuration of the charge amplifier (amplifying means) 410 may be as shown in FIG. In FIG. 16, the charge amplification /
An output differentiating / integrating circuit 414 a for differentiating and integrating the output, and an output differentiating / integrating circuit 414 a
Current / voltage conversion circuit 414 for converting the current from
b.

Also, in the above embodiment, the lead wire 500
Cover 4 of connector 400 provided on the other end side of
Although a stay (attachment part) 426 is provided in the charge amplifier (amplification means) 410 interposed and set in the middle of the lead wire 500 or 20, the connector and the amplification means can be easily attached in the engine room. The stays 426 may not be provided. In this case, the connector 400 and the charge amplifier may be adhered to an appropriate place in the engine room, or may be fixed with a separate bracket or the like.

In the above embodiment, a glow plug with a combustion pressure sensor has been described as an example of a combustion pressure sensor structure. Structure (eg, injectors, bolts,
The present invention is applicable to a combustion pressure sensor structure including a spark plug and the like, and a combustion pressure sensor attached to the structure to detect a combustion pressure of an engine.

FIG. 17 shows an example of application to a spark plug 700.
FIG. 18 shows an example of application to the injector 800, and FIG. 19 shows an example of application to the bolt 900. In FIG. 17, a spark plug (structure according to the present invention) 70
0 is a mounting screw 701a formed on the housing 701.
To the engine head 1 of a gasoline engine.

In FIG. 18, an injector (structure according to the present invention) 800 for injecting fuel from a fuel pump into a combustion chamber 1a is mounted on an engine head 1 of a gasoline or diesel engine by a fixing bolt 801 and a mounting bolt 801. It is attached by a screw 801a. FIG.
9, a bolt (a structure according to the present invention) 900 as a member exposed to the combustion chamber 1 a in the engine head 1.
Are attached to the engine head 1.

In FIGS. 17 to 19, the combustion pressure sensor (pressure sensor) 300 includes
900, mounting screws 701a, 801a, 901a
The combustion pressure of the engine is detected by converting a force accompanying the combustion pressure acting on these structures into an electric signal based on the piezoelectric characteristics of the piezoelectric element 321.

In the examples shown in FIGS. 17 to 19, the combustion pressure sensor 300, the connector 400, and the lead wire 500 have the same configuration as in the first embodiment, and their effects are also the same. Also, in the examples shown in FIGS. 17 to 19, the second embodiment and FIGS.
Of course, the modification shown in FIG. 6 can be applied.

[Brief description of the drawings]

FIG. 1 is an overall schematic sectional view of a glow plug with a combustion pressure sensor according to a first embodiment of the present invention.

FIG. 2 is an enlarged detailed explanatory view showing a combustion pressure sensor in FIG. 1;

FIG. 3 is a detailed explanatory view of a piezoelectric element section in FIG. 2;

FIG. 4 is a diagram showing the directionality of an electrode surface in the piezoelectric element section in FIG.

FIG. 5 is an enlarged detailed explanatory view showing the connector in FIG. 1;

FIG. 6 is a circuit configuration diagram of an amplification unit (charge amplifier) according to the present invention.

FIG. 7 is a waveform chart showing an effect of removing noise accompanying fuel injection in the first embodiment.

FIG. 8 is a waveform diagram showing the influence of noise during fuel injection in the related art.

FIG. 9 is a table showing the effect of removing relay contact noise in the first embodiment.

FIG. 10 is a waveform diagram showing an example of a conventional relay contact noise.

FIG. 11 is a waveform chart showing a noise removing effect by the low-pass filter according to the first embodiment.

FIG. 12 is a waveform diagram showing the influence of noise when a conventional high-pass filter is not interposed.

FIG. 13 is a diagram illustrating a noise removing effect by a high-pass filter according to the first embodiment.

FIG. 14 is a detailed explanatory view of a combustion pressure sensor in a glow plug with a combustion pressure sensor according to a second embodiment of the present invention.

FIG. 15 is a diagram showing an example in which a charge amplifier according to the present invention is set in the middle of a lead wire.

FIG. 16 is a diagram showing another example of the circuit configuration of the amplification means (charge amplifier) according to the present invention.

FIG. 17 is a diagram showing an example in which the present invention is applied to a spark plug as a structure.

FIG. 18 is a diagram showing an example in which the present invention is applied to an injector as a structure.

FIG. 19 is a diagram showing an example in which the present invention is applied to a bolt as a structure.

[Explanation of symbols]

1: engine head, 200: plug body, 300,
600: combustion pressure sensor, 321: piezoelectric ceramics, 4
00, 400a: connector, 410: charge amplifier,
413, 611: resin, 416: high-pass filter, 4
17: low-pass filter, 426: stay, 500: lead wire, 503: earth side shield wire.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F055 AA23 BB14 CC11 DD09 EE23 FF11 FF38 GG44 HH11 3G019 CC07 KA28 KD17 KD19 3G084 DA04 FA21

Claims (9)

[Claims] 1. A structure (200, 700, 80) attached to an engine (1) disposed in an engine room.
0, 900) and a combustion pressure sensor (30) attached to the structure and converting a force associated with the combustion pressure of the engine acting on the structure into an electric signal based on the piezoelectric characteristics of the piezoelectric element (321).
0), a wiring member (500) having one end electrically connected to the piezoelectric element of the combustion pressure sensor; and an external circuit provided at the other end of the wiring member. And a connector (400) for making an electrical connection with the combustion pressure sensor, wherein the connector incorporates amplifying means (410) for amplifying an electric signal from the piezoelectric element. Structure. 2. A structure (200, 700, 800, 900) attached to an engine (1), and a piezoelectric element (200) attached to the structure and applying a force acting on the structure with a combustion pressure of the engine. 321) converts the combustion pressure sensor (60) into an electric signal based on the piezoelectric characteristic.
0), wherein the combustion pressure sensor is molded and integrated with resin and amplifying means (410) for amplifying an electric signal from the piezoelectric element. A combustion pressure sensor structure characterized by the above-mentioned. 3. A structure (200, 700, 80) mounted on an engine (1) disposed in an engine room.
0, 900), and a combustion pressure sensor (300) attached to the structure and converting a force accompanying a combustion pressure acting on the structure into an electric signal based on the piezoelectric characteristics of the piezoelectric element (321). In the combustion pressure sensor structure, a wiring member (500) having one end electrically connected to the piezoelectric element of the combustion pressure sensor; and a wiring member provided at the other end of the wiring member, for electrically connecting to an external circuit. And an amplifying means (410) for amplifying an electric signal from the piezoelectric element is provided at an intermediate portion of the wiring member. body. 4. The combustion pressure according to claim 1, wherein the wiring member (500) is electrically shielded by a coating member (503) that is electrically shielded. Sensor structure. 5. The combustion pressure sensor structure according to claim 1, wherein the amplification means is electrically shielded. 6. The amplifying means (410) includes a resin (41).
The combustion pressure sensor structure according to any one of claims 1 to 5, characterized in that the combustion pressure sensor structure is molded by (3, 611). 7. The amplifying means (410) has a filter circuit (416, 417) for removing electrical noise in an electrical signal from the piezoelectric element (321). Any one of claims 1 to 6
6. A combustion pressure sensor structure according to any one of the preceding claims. 8. The combustion pressure sensor structure according to claim 1, wherein the connector (400) has a mounting portion (426) that can be mounted in the engine room. 9. The combustion pressure sensor structure according to claim 3, wherein the amplifying means has a mounting portion mountable in the engine room.