JP6228861B2 - Glow plug integrated combustion pressure sensor - Google Patents

Description

  The present invention relates to a glow plug integrated combustion pressure sensor provided in an internal combustion engine and provided integrally with a glow plug to detect a combustion chamber pressure.

In order to detect the combustion pressure in the combustion chamber of an internal combustion engine, various types of glow plug integrated combustion pressure sensors in which a pressure detecting piezoelectric element is provided in the glow plug have been proposed.
For example, Patent Document 1 is a ceramic heater extending along an axis, a columnar base formed of an insulating ceramic, a resistance heating element embedded in the base and generating resistance by energization, and the resistance The ceramic heater that is electrically connected to the heating element and has an electrode extraction portion that is exposed on the outer surface of the rear end portion of the ceramic heater, and the ceramic heater is housed inside with the tip of the ceramic heater protruding. A cylindrical housing that secures hermeticity inside the housing, and elastically deforms the housing and the ceramic heater while being connected directly or via another member. A movable member that allows displacement along the axis with respect to the housing, and the inside of the housing A pressure sensor disposed on the rear end side of the ceramic heater and detecting the pressure of the combustion gas based on the displacement of the ceramic heater, and a load transmission disposed in the housing on the rear end side of the movable member A cylindrical load transmission member that is a member, is fitted into the rear end portion of the ceramic heater, is connected directly to the housing or via another member, and transmits the displacement of the ceramic heater to the pressure sensor; There is disclosed a glow plug comprising: a thermal plug having a thermal conductivity greater than that of the base of the ceramic heater.

Further, in Patent Document 2, a cylindrical housing attached to the engine so that one end side is located on the combustion chamber side of the engine, and held inside the housing so that one end side is exposed from the one end of the housing. A pipe member, a heat generating member provided in the pipe member and generating heat when energized, one end side of which is connected to the heat generating member inside the pipe member to be electrically connected, and the other end side of the housing. A metal center shaft housed in the housing so as to protrude from the other end, and a force acting on the pipe member as the combustion pressure of the engine is generated are transmitted through the center shaft to reduce the combustion pressure. A glow plug with a combustion pressure sensor comprising a combustion pressure sensor for detection is disclosed.
In the glow plug with a pressure sensor of Patent Document 2, the pressure sensor is assembled by applying a preload to the housing by the fastening axial force of the fixed nut and the middle shaft screw portion, the middle shaft is distorted by the combustion pressure, and the preload of the fixed nut is loosened. Thus, the output from the pressure sensor is configured.

JP 2013-228175 A JP 2003-316996 A

However, in the conventional glow plug integrated combustion pressure sensor as disclosed in Patent Document 1, the ceramic heater and the housing are connected using a movable member that allows the displacement of the ceramic heater by elastic deformation.
In the vicinity of the tip of the glow plug facing the combustion chamber, a deposit made of unburned fuel, carbon, fuel modifier, etc. is easily formed, accumulates between the movable member and the housing, and the movement of the movable member is hindered. There is a risk that the combustion pressure cannot be detected accurately.
In order to make such a movable member elastically deformable, the rigidity of the movable part made of the elastic member is inevitably reduced.

In general, the vicinity of the tip of the glow plug is exposed to a severe cooling cycle, so that the thermal stress on the movable member becomes large, and there is a possibility that the movable member having low rigidity may be cracked due to metal fatigue.
Furthermore, since the ceramic heater itself is used as a load transmission member, there is a risk of disconnection of the connection portion between the electrode take-out portion and the housing and the transmission sleeve that are connected to the heating element built in the ceramic heater.

  On the other hand, in the method of detecting the loosening of the preload as disclosed in Patent Document 2, the maximum preload that can be applied depends on the strength limit of the tensile strength of the central shaft, so that the combustion pressure is large enough to exceed the maximum preload. If this is added, the combustion pressure may not be measured.

  SUMMARY OF THE INVENTION In view of the above circumstances, the present invention has an object to provide a glow plug integrated combustion pressure sensor that is excellent in durability without causing a decrease in detection accuracy due to deposit.

  In the glow plug integrated combustion pressure sensor (8, 8a) of the present invention, a glow plug (1) provided in the internal combustion engine (9) and generating heat when energized, and a tip thereof to the combustion chamber (90) of the internal combustion engine. A combustion pressure detector (5) including a cylindrical fixing member (2) for fixing the glow plug so as to be located inside the communication hole (913) facing the piezoelectric element (50) for detecting pressure by a piezoelectric effect. ), A load transmission member (4) for transmitting the combustion pressure generated in the combustion chamber to the combustion pressure detection unit, and energization control to the glow plug and input / output control to the combustion pressure detection unit A control unit (6) and an input / output unit (7) for input / output between the control unit and the outside, and these are integrally housed in a cylindrical housing (3), Glow plug for heating and detecting the combustion pressure A body-type combustion pressure sensor, wherein the housing has an outer cylindrical portion (30) extending in a cylindrical shape in the axial direction, a load transmission member locking portion (31) projecting in an annular shape toward the inside on the tip side, A male screw part (32) provided on the base end side of the outer cylinder part, and screwed into a female screw part (912) of a plug hole (910) provided in an engine head (91) of the internal combustion engine, and the male screw And an element accommodating portion (33) provided at a position exposed from the engine head further on the base end side of the portion, wherein the load transmitting material is held inside the outer tube portion, and one end is engaged with the load transmitting member. An inner cylinder part (40) that abuts against the stop part and the other end is exposed to the inside of the element housing part, and extends in the inner cylinder part, and has a bowl shape toward the outer diameter direction inside the element housing part Of the detection part fixed to the inside of the element housing part. It is characterized in that the flange is brought into contact with the lower surface.

According to the present invention, when the combustion pressure P _SYL generated inside the combustion chamber acts on the engine head and the engine head is compressed and deformed, the fixing member extends from the tip of the external thread portion of the outer cylinder portion. Thus, the load transmission member is relatively pushed up to the proximal end side.
At this time, the flange portion compresses the detection portion, and the combustion pressure P _SYL can be calculated from the amount of charge generated in proportion to the load at that time.

Furthermore, if the combustion pressure is detected in the direction of reducing the precompression load as in the prior art, it is not possible to add a precompression load exceeding the tensile strength limit of the central shaft. However, depending on the tensile strength of the middle shaft, measurement may not be possible if combustion pressure exceeding the maximum precompression load is generated.
However, in the present invention, the precompression load can be accurately adjusted at the time of assembly, and the combustion pressure P _SYL acts in the compression direction of the piezoelectric element via the load transmission member. A high combustion pressure P _SYL can be detected without depending on the tensile strength of the central shaft or the like used in the copper passage with the part.

Further, in the present invention, since the glow plug is not used as a pressure transmission medium as in the prior art, the combustion pressure _PSYL may cause disconnection in the conduction path from the glow plug to the control unit. In addition, since there is no movable part as in the prior art, there is no problem that the mobility is lowered and the detection accuracy is lowered due to the deposit.

Sectional drawing which shows the outline | summary of the glow plug integrated combustion pressure sensor in the 1st Embodiment of this invention FIG. 1A is an enlarged sectional view showing a seal structure between a heating element fixing member and an engine head used in the glow plug integrated combustion pressure sensor of FIG. 1A. FIG. 1B is an enlarged sectional view showing a modification of FIG. Sectional drawing which shows the operation principle of the glow plug integrated combustion pressure sensor of this invention FIG. 2A is an enlarged view of the main part showing a difference in relative position of the load transmission member depending on the presence or absence of combustion pressure Sectional drawing which shows the glow plug integrated combustion pressure sensor in the 2nd Embodiment of this invention.

Referring to FIGS. 1A, 1B, 1C, 2A, and 2B, an outline of a glow plug integrated combustion pressure sensor 8 (hereinafter referred to as an integrated sensor 8) according to the first embodiment of the present invention. explain.
In the following description, the side facing the combustion chamber 90 of the internal combustion engine 9 is the front end side, and the side connected to the outside is the base end side.
The integrated sensor 8 includes a glow plug 1 that generates heat when energized, a fixing member 2 that holds and fixes the glow plug 1, and the fixing member 2 is held in an airtight manner 3 in a plug hole 911 provided in the engine head 91 of the internal combustion engine 9. A housing 3 for carrying out, a load transmission member 4 for transmitting the combustion pressure P _SYL generated in the combustion chamber, a detection unit 5 for detecting the pressure transmitted by the load transmission member 4, and an energization control and detection unit for the glow plug 1 5 includes a control unit 6 that performs input / output control to 5 and an input / output unit 7 that is connected to the outside.

  In the integrated sensor 8 of the present invention, the housing 3 has an outer cylindrical portion 30 that extends in a cylindrical shape in the axial direction, a load transmission member locking portion 31 that protrudes in an annular shape toward the inside at the distal end side, and the internal combustion engine 9. The internal thread portion 912 of the plug hole 910 provided in the engine head 91 is screwed into the external thread portion 32 provided on the proximal end side of the outer cylinder portion 30. The element accommodating portion 33 provided at a position exposed from 91 is provided, the load transmitting member 4 is held inside the outer cylinder portion 30, one end abuts on the load transmitting member locking portion 31, and the other end is the element. An inner cylindrical portion 40 exposed inside the accommodating portion 33, and a flange portion 41 extending in the inner cylindrical portion 40 and extending in a bowl shape toward the outer diameter direction inside the element accommodating portion 33. The flange 41 is brought into contact with the lower surface of the detection unit 5 fixed in the unit 33. The features.

A so-called ceramic heater is used for the glow plug 1 in the present embodiment.
The glow plug 1 includes an insulator 13 formed in a rod shape extending in the axial direction, a resistance heating element 10 embedded in the insulator 13 and formed in a U-shape, and end portions of the resistance heating element 10. To the ground-side lead portion 11 and the energization-side lead portion 12 that are connected to the ground and pulled out to the surface at a predetermined position of the insulator 13, and the ground terminal 110 and the energization-side lead portion 12 provided in connection with the ground-side lead portion 11 It is comprised by the electricity supply terminal 120 provided by connecting to.

For the resistance heating element 10, for example, a known conductive ceramic material such as tungsten carbide (WC), molybdenum disilicide (MoSi ₂ ), tungsten disilicide (WSi ₂ ) or the like is used, and a known method such as injection molding is used. It is formed in a substantially U shape.
The ground side lead portion 11 and the energization side lead portion 12 are formed in a predetermined shape using a known conductive material such as tungsten (W), and are connected to respective ends of the substantially U-shaped resistance heating element 10. Yes.

The insulator 13 is made of a known insulating ceramic such as silicon nitride Si ₃ N ₄ and covers the resistance heating element 10, the ground side lead portion 11, and the energization side lead portion 12.
The insulator 13 is integrally sintered by a known method such as hot pressing in a state where the resistance heating element 10, the ground side lead portion 11, and the energization side lead portion 12 are embedded inside.

  The ground terminal 110 and the energization terminal 120 are connected to the respective ends of the ground-side lead portion 11 and the energization-side lead portion 12 exposed to predetermined positions on the surface of the insulator 13 by cutting after the insulator 13 is sintered. Thus, the resistance heating element 10 formed by a known method such as film printing or plating and embedded in the insulator 13 can be energized.

The current-carrying terminal 120 is connected to the long shaft-shaped middle shaft 122 via a cylindrical relay sleeve 121, and is a board connection lead drawn from the control circuit board 60 via a terminal fitting 123 provided at the base end of the middle shaft 122. Connected to the unit 124.
Since the base end side of the middle shaft 122 is held by the elastically deformable substrate connection lead portion 124, no load is applied in the axial direction, and disconnection or the like occurs in the conduction path from the glow plug 1 to the control circuit substrate 60. There is no risk of harming the conduction reliability.

The relay sleeve 121, the center shaft 122, the terminal fitting 123, and the board connection lead portion 124 are made of a known metal material having excellent conductivity such as copper, aluminum, stainless steel, iron-nickel alloy or the like.
The ground terminal 110 is electrically connected to the engine head 91 via the fixing member 2 and is in a grounded state.
In the present invention, if a part of the energization path connecting the glow plug 1 and the control circuit board 60 can be elastically deformed inside the element housing portion 33 having a relatively low temperature, the combustion pressure P _SYL When the housing 3 is compressed and deformed, the base end side is elastically connected by the board connecting lead portion 124, so that the middle shaft 122 is not distorted.

The fixing member 2 (hereinafter referred to as the fixing member 2) is made of a metal material having high heat resistance such as stainless steel, carbon steel, iron-nickel alloy or the like.
Moreover, the fixing member 2 is formed thick so that the rigidity becomes high.
The fixing member 2 is formed in a top-shaped cylindrical shape, and is formed on the base end side of the press-contact portion 20 formed so as to project in a bowl shape in the radial direction. It is comprised by the part 21 and the cylindrical front side holding | maintenance part 22 formed in the front end side.

The glow plug 1 is accommodated and fixed inside the fixing member 2.
From the base end side of the fixing member 2, the base end side of the glow plug 1 is exposed, and the energization terminal 120 and the middle shaft 122 can be connected.
From the distal end side of the fixing member 2, the distal end side of the glow plug 1 in which the resistance heating element 10 is embedded is exposed.

A brazing material 24 is poured into the gap between the inner peripheral surface of the base end side holding portion 21 and the outer peripheral surface of the glow plug 1 and the gap between the tip side holding portion 22 and the outer peripheral surface of the glow plug 1, and is fixed to the glow plug 1. The member 2 is firmly joined.
At the same time, conduction between the ground terminal 110 formed on the surface of the glow plug 1 and the inner peripheral surface of the fixing member 2 is achieved.
In addition, an annular groove is formed at the boundary between the inner peripheral surface of the base end side tubular portion 21 and the outer peripheral surface of the glow plug 1, and a sealing member 23 such as a brazing material or a molten glass is disposed. The connection between the plug 1 and the fixing member 2 is made stronger.

A pressure contact portion horizontal surface 201 orthogonal to the axis of the glow plug 1 is formed on the proximal end side of the pressure contact portion 20, and a frustoconical pressure contact is formed on the distal end side so that the diameter decreases toward the tip. A partial inclined surface 200 is formed.
A lower end surface of a housing outer cylinder portion 30 to be described later is brought into contact with the pressure contact portion horizontal surface 201 so that an axial force when the housing 3 is helically fixed to the engine head 91 acts.
The pressure contact portion inclined surface 200 abuts on a seating inclined surface 912 provided on the engine head 91 and is pressed by an axial force from the housing outer cylinder portion 30 to be in a close contact state.
Since a compressive force acts on the pressure contact portion 20 in the axial direction, the brazing material 24 is prevented from flowing into the gap between the inner peripheral surface of the pressure contact portion 20 and the surface of the glow plug 1, so that the brazing material 24 due to residual stress is introduced. You may make it prevent peeling of.

The housing 3 is made of a known metal material such as stainless steel, iron, nickel, iron-nickel alloy, or carbon steel.
The housing 3 is substantially cylindrical and has a housing outer cylinder portion 30 (hereinafter referred to as an outer cylinder portion 30) that abuts against the pressure contact portion horizontal surface 201 of the fixing member 2 and presses in the axial direction, and a distal end side of the outer cylinder portion 30. The inner cylinder locking portion 31 that protrudes in an annular shape so as to become smaller in diameter toward the inside at the predetermined position, the male screw portion 32 provided on the outer periphery of the proximal end of the outer cylinder portion 30, and the outer cylinder portion 30 are the engine. An element accommodating portion 33 extending to a position exposed from the head 91, a fixed washer 34 for fixing the combustion pressure detecting portion 2 inside the element accommodating portion 33, and a base end side fixed washer 34 are fixed to the element accommodating portion 33 by welding. And a hexagonal portion 36 for screwing the male screw portion 32 of the housing 3 to the female screw portion 910 provided in the engine head 91.

The outer cylinder part 30 is formed in the cylinder shape extended in an axial direction.
A male screw portion 32 and a hexagonal portion 36 are provided on the outer periphery of the base end side of the outer cylinder portion 30.
The distal end of the outer cylinder part 30 is in contact with the horizontal surface 201 of the bowl-shaped seal part 20 provided on the fixing member 2.
The axial force when the male screw portion 32 is screwed into the female screw portion 910 provided at the base end of the plug hole 911 of the engine head 91 acts on the pressure contact portion horizontal surface 201 via the outer cylinder portion 30.

Between the plug hole 911 of the housing head 91 and the through hole 913 communicating with the combustion chamber 90, a mortar-shaped seating inclined surface 912 that is reduced in diameter toward the combustion chamber side is formed. .
As shown in FIG. 1B, the pressure contact portion inclined surface 200 pressed by the outer cylinder portion 30 is in close contact with the seating inclined surface 912 and is sealed so that gas does not leak from the combustion chamber 90.
Further, as shown in FIG. 1C, the press contact portion 20a is formed so that the press contact portion inclined surface 200a becomes a curved surface so as to be convex toward the tip side, and the inclination angle of the seating inclined surface 912a is changed to the press contact portion inclined surface. You may form so that it may contact | connect 200a.
It is sufficient that the fixing member 2 and the engine head 91 can be hermetically sealed by pressing the horizontal surface 201 of the pressure contact portion 20 by the axial force of the outer cylinder portion 30, so that the pressure contact portion inclined surface 200 and the seating inclined surface 912 are separated from each other. The metal seal structure generally used in order to ensure airtightness can be appropriately adopted by being pressed against each other.

The element accommodating portion 33 is provided at a position where the outer cylinder portion 30 is exposed from the engine head 91.
The element accommodating portion 33 accommodates the combustion pressure detecting portion 5 and the control portion 6 at a position exposed on the proximal end side of the engine head 91.

The load transmission member 4 includes a load transmission inner cylinder portion 40 (hereinafter referred to as an inner cylinder portion 40) that extends in a cylindrical shape, and a flange-shaped load transmission flange portion that extends at the end of the inner cylinder portion 40 and extends in the radial direction. 41 (hereinafter referred to as a collar 41).
The load transmitting member 4 is made of a metal material that is at least equal to or harder than the outer cylinder part 30 or is thicker than the outer cylinder part 30 using a metal material of the same material as the outer cylinder 30. By forming, it is possible to exhibit rigidity that is at least equal to or higher than that of the outer cylinder portion 30.
As described above, the housing 3 is required to have a strength that can withstand compression and a strength that does not cause plastic deformation. The housing 3 has a sufficiently high compressive strength so that it does not buckle when a helical axial force is applied. In order to guarantee the linearity of the output, a proof stress that can be used in the elastic deformation region is necessary.
On the other hand, in addition to the proof stress required for the housing 3, it is desirable that the load transmitting member 4 has a higher rigidity. This is because it is important for the load transmitting member 4 to transmit the load change resulting from the distortion of the housing 3 to the combustion pressure detecting unit 5 without loss.

The inner cylinder part 40 is slidably held inside the outer cylinder part 30, one end is supported by being in contact with the inner cylinder locking part 31, and the other end is a male provided at the base end of the outer cylinder part 30. It is exposed to the base end side from the screw portion 32 and the hexagonal portion 36.
The flange 41 extends in the outer diameter direction on the inner side of the element accommodating portion 33 and is in contact with the bottom surface of the combustion pressure detecting portion 5 accommodated in the element accommodating portion 33.
An inner shaft 120 is disposed inside the inner cylinder portion 40.
A cylindrical middle shaft insulating member 125 is disposed between the inner tube portion 40 and the middle shaft 122, and electrical insulation between the inner tube portion 40 and the middle shaft 122 is ensured.

The middle shaft insulating member 125 can secure electrical insulation with the inner tube portion 40 while holding the middle shaft 122 at the center of the inner tube portion 40, and heat resistance to the extent that it can resist heat dissipation from the glow plug 1 is secured. For example, the material is not particularly limited.
For example, a hard material obtained by sintering an insulating material such as alumina, mullite, silica, titania, spinel into a cylindrical shape may be interposed between the middle shaft 122 and the inner cylindrical portion 40, or a silicone resin or silicone rubber. Alternatively, a heat-resistant and insulating resin material such as fluororesin or fluororubber may be used as a coating film that covers the middle shaft 122.
Further, in the present embodiment, an example in which the middle shaft insulating member 125 is formed in a cylindrical shape is shown, but it is not always necessary to cover the entire length of the middle shaft 122, and silicone rubber, fluorine resin rubber, etc. A plurality of O-rings or the like made of an elastic member having insulating properties and heat resistance may be provided between the middle shaft 122 and the inner cylinder portion 40 to hold the middle shaft 122 in the middle.

The detection unit 5 accommodates the piezoelectric element 50 that generates a charge by compression, a detection electrode 51 that extracts the charge generated in the piezoelectric element 50, a signal line 52 that connects the detection electrode 51 and the control unit 6, and the piezoelectric element 50. The sensor housing 53 functions as a ground electrode.
A central shaft 122 is disposed at the center of the detection unit 5 in an electrically insulated state.
For the piezoelectric element 50, a known piezoelectric material such as quartz, PZT, lithium niobate, polyvinylidene fluoride, or the like can be used.
In this embodiment, two piezoelectric elements 50 formed in a donut disk shape are stacked with their polarization directions aligned so that the inside becomes a positive electrode, and a detection electrode 51 is interposed therebetween.
In this embodiment, an example in which two piezoelectric elements 50 are stacked is shown. However, in the present invention, the number of piezoelectric elements is not limited, and the detection electrodes are arranged between piezoelectric elements whose polarization directions are aligned in a certain direction. Alternatively, a piezo stack in which the same poles are connected by alternately interposing electrodes and ground electrodes may be used. By increasing the number of piezoelectric elements, it is possible to increase the amount of charge generated when the combustion pressure P _SYL is transmitted and mechanical stress is applied, thereby improving measurement accuracy.

The outer peripheral surface and inner peripheral surface of the piezoelectric element 50 are covered with an insulating coating 501 such as silicone resin or fluororesin.
In the signal line 52, the surface of the core wire 520 made of a highly conductive material such as copper is covered with an insulating coating 522.
A connection portion 521 is provided on the inner peripheral surface side of the detection electrode 51, one end portion of the core wire 520 of the signal line 52 is connected, and the base end side is passed through the inner diameter of the detection element 50 through the signal line connection terminal 523. Is connected to a substrate lead 524 drawn from the control circuit board 61 provided on the board.

  In addition, since the substrate lead 524 is formed with a flexible portion that can be elastically deformed, stress concentration on the connection portion 521 can be alleviated and connection failure can be prevented. In the present invention, the method of drawing out the signal line 52 is not particularly limited, and the signal line 52 may be drawn out from the outer peripheral surface side of the detection electrode 51 to the control unit 6 side while being insulated from the sensor housing 52.

The sensor housing 53 is made of a metal material such as stainless steel, iron, nickel, or iron-nickel alloy, and includes a housing portion 530 that houses the piezoelectric element 50 and the detection electrode 51, and a lid portion 531.
The sensor housing 53 is electrically connected to the surface of the piezoelectric element 50 and exhibits a function as a ground electrode.
The lower surface side of the sensor housing 53 is in contact with the flange 41 of the load transmission member 4.
A fixed washer 35 is disposed in contact with the upper surface side of the sensor housing 53, and the fixed washer 35 is joined to the element housing portion 35 by providing a joint portion 37.

The controller 6 includes a glow plug energization control device (GUC) 60 and a control circuit board 61.
The GCU 60 calculates the duty for energizing the glow plug 1 according to the drive signal SI transmitted from the outside, supplies predetermined power, and controls the temperature of the heating element.
In addition, a self-diagnosis circuit (not shown) can be provided to determine whether the glow plug 1 is deteriorated or disconnected, and the self-diagnosis signal DI can be transmitted to the outside.
In addition to energization control to the glow plug 1, the GCU 60 has a specific function such as determining its own cylinder position, protecting the semiconductor element from reverse power connection, and performing abnormality diagnosis. This can be changed as appropriate.

The control circuit board 61 supplies a control voltage for controlling the GCU 60 by adjusting a power supply voltage supplied from the outside, or a power supply circuit for supplying the power adjusted by the GCU 60 to the glow plug 1. A charge pump circuit or the like is provided for handling the charge generated in the combustion pressure detection unit 5 of the engine head as a voltage as the combustion pressure P _SYL in the combustion chamber 90 rises.
When the engine head 91 is distorted by the combustion pressure P _SYL in the combustion chamber 90 and the outer cylinder part 30 is compressed and deformed, the load transmission member 4 supported by the inner cylinder locking part 31 provided in the outer cylinder part 30 is relatively moved. Thus, the detection unit 5 sandwiched between the flange 41 and the fixed washer 35 is compressed.

A charge proportional to the load applied to the piezoelectric element 50 is generated, which is converted into a voltage that is easy to handle by a charge pump provided in the control circuit unit 61, and calculated by an ECU or the like provided outside. A signal indicating _SYL is output.
In addition, what kind of signal the combustion pressure _PSYL is transmitted to the outside can be appropriately selected.
For example, the combustion pressure P _SYL itself may be transmitted as serial data to the outside, or the combustion pressure P _SYL is determined as a threshold by a self-diagnosis device provided in the GCU 60 to check whether there is a combustion abnormality such as misfire or knocking. These results can be output to the outside as a self-diagnosis signal DI together with other abnormality detection results such as disconnection of the energization path to the glow plug 1 and deterioration of the glow plug 1.

The input / output unit 7 is connected to an unillustrated DC power source and an engine control device (hereinafter referred to as ECU) provided via an unillustrated connector wire harness, an energizing terminal 70, a signal terminal 71, a connector. A base 72 and a connector housing 73 are included.
The energizing terminal 70 and the signal terminal 71 are made of a metal material having excellent conductivity such as copper, aluminum, nickel, iron, and stainless steel.
The energization terminal 70 is constituted by a power supply terminal and a grounding terminal, and serves to supply a voltage to the control circuit 6 and to perform grounding.

The signal terminal 71 is a drive signal terminal that transmits a drive signal SI oscillated from the ECU according to the operation state of the internal combustion engine 9 to the control unit 6, and a sensor that transmits the combustion pressure P _SYL detected by the detection unit 5 to the ECU. The output terminal includes a self-diagnosis signal terminal for transmitting a self-diagnosis signal DI from the control unit 6 to the ECU.
It is possible to appropriately change what signals are specifically input / output via the signal terminal 71.

A known insulating resin material is used for the connector base 72 and the connector housing 73.
The energizing terminal 70 and the signal terminal 71 are embedded and fixed in the connector base 72, and one end thereof is exposed in a connector housing 73 formed in a cylindrical shape, and can be connected to the outside.

The other ends of the electric terminal 70 and the signal terminal 71 are exposed to the control unit 6 side, and are connected to predetermined positions of the GCU 60 and the control circuit board 61.
The connector housing 73 electrically connects each terminal and the counterpart terminal in the connector housing 73 by fitting with a connector harness (not shown).

A communication hole 913 formed in the engine head 91 communicates the combustion chamber 90 and the plug hole 911.
The tip of the glow plug 1 is disposed in the communication hole 913, and the glow plug 1 generates heat when energized. The mixture introduced into the fuel chamber 90 is heated to assist ignition, or the combustion exhaust is heated. To assist in exhaust purification.

The effects of the present invention will be described in detail with reference to FIGS. 2A and 2B.
If the tightening torque when the male screw portion 35 provided in the housing 3 is screwed into the female screw portion 910 provided in the engine head 91 is increased to a certain level or more, the outer cylinder portion 30 is distorted, The inner cylinder part 40 of the load transmission member 4 supported by the provided inner cylinder locking part 31 is relatively pushed up to the proximal end side.

At this time, the proximal end side of the piezoelectric element 50 accommodated in the sensor housing 53 is fixed by the fixed washer 35, and the distal end side is pressed by the flange portion 41 of the load transmitting member 4, so that the compression load on the piezoelectric element 50 is reduced. Will increase.
Since the tightening torque can be quantitatively monitored from the electric charge generated in the piezoelectric element 50 due to the piezoelectric effect, excessive tightening is prevented, and the precompression load applied to the detection unit 5 is constant. The integrated sensor 8 can also be assembled to the engine head 91.

If the tightening torque at this time exceeds the tensile strength of the outer cylinder part 30 or exceeds the compression limit of the piezoelectric element 50, the yield value of the outer cylinder part 30 may be exceeded and plastic deformation may be caused. 50 may cause measurement damage, and if the piezoelectric element 50 is excessively compressed at the time of assembly, it may not be detected even if a combustion pressure is applied.
However, in the sensor 8 of the present invention, not only the combustion pressure but also the tightening torque can be detected by the detection unit 5, so that excessive tightening after assembly can be avoided and the combustion pressure can be detected stably.

Further, when the combustion pressure P _SYL in the combustion chamber 90 acts on the engine head 91 and the engine head 91 is compressed and deformed, the pressure contact portion 20 provided on the fixing member 2 from the tip of the external thread portion 32 of the outer cylinder portion 30. The distance to the position where the inclined surface 200 abuts against the engine head seating inclined surface 912 is shortened, and the load transmitting member 4 is pushed up to the base end accordingly.
At this time, the flange part 41 compresses the detection part 5, and the combustion pressure _PSYL can be calculated from the amount of charge generated in proportion to the load at that time.

If the combustion pressure is applied in the direction of reducing the precompression load and the combustion pressure is detected as in the past, it is not possible to apply a precompression load that exceeds the tensile strength limit of the center shaft. If the load depends on the tensile strength of the middle shaft and a combustion pressure exceeding the maximum precompression load is generated, measurement may not be possible.
However, the integrated sensor 8 of the present invention can accurately adjust the precompression load during assembly, and the combustion pressure P _SYL acts in the compression direction of the piezoelectric element 50 via the load transmission member 4. A high combustion pressure P _SYL can be detected without depending on the tensile strength of 122.

Furthermore, since the integrated sensor 8 of the present invention does not use the heating element or the central shaft as a pressure transmission medium, the combustion pressure P _SYL causes disconnection in the conduction path from the heating element 1 to the control unit 6. There is no fear.
In addition, no movable part is provided, and the conventional deposit does not cause a problem that the mobility is lowered and the detection accuracy is lowered.

In the integrated sensor 8 of the present invention, the control circuit board 61 and the middle shaft 122 are connected when the load transmitting member 4 is relatively moved in accordance with a change in the distortion of the engine head 91 caused by a change in the combustion pressure _PSYL. The connecting 123 is elastically expanded and contracted in the axial direction.
However, since the control unit 6 is disposed in the element housing portion 33 provided in a relatively low temperature environment exposed to the base end side from the engine head 91, the control unit 6 is movable to be elastically deformed in a conventional high temperature environment. The risk of metal fatigue is low compared to the part, and the stress on the conduction path from the control part 6 to the glow plug 1 is small compared with the case where a heating element, a central shaft, etc. are used as a pressure transmission medium, and over a long period of time. It is possible to maintain high conduction reliability.

With reference to FIG. 3, the integrated sensor 8a in the 2nd Embodiment of this invention is demonstrated.
In addition, since the same code | symbol is attached | subjected about the same structure as the said embodiment, and the code | symbol of the alphabet is attached as a branch number to a different location, the overlapping description is abbreviate | omitted and it demonstrates focusing on the characteristic part in this embodiment. To do.
In the above-described embodiment, an example in which a so-called ceramic glow plug 1 is used as a heating element has been shown. However, the present invention does not limit the type of the heating element, and as in this embodiment, a so-called heating element is used. A metal glow plug 1a can also be used.
Furthermore, in the said embodiment, in order to energize the glow plug 1, the example which used the center axis | shaft extended in a long axis shape was shown, However, In this invention, the center axis | shaft is not used as a pressure transmission medium. For this reason, it is not necessary to use a rigid material, and the conductive wire 122a covered with the flexible insulating coating 122 may be used as in this embodiment.
By using the conductive wire 122a having flexibility, it is not necessary to form a flexible portion that elastically expands and contracts in the substrate connection lead portion 124a that is to be connected to the printed circuit board 61.

In the present invention, as shown in the previous embodiment, it is not always necessary to use a connector structure for connection to the outside, and a power supply for connecting the power supply voltages + B and GND of the power supply device provided outside to the control unit. A conductive line 70a and a signal line 71a for exchanging a drive signal SI, a self-diagnosis signal DI, and a combustion pressure signal PI between the control unit 6 and an ECU provided outside are bundled by a grommet 72a made of heat-resistant rubber. In addition, the input / output unit 7a may be provided by providing a crimped portion 73a on the base end side of the element housing portion 33 so as to be hermetically sealed.
Furthermore, the configuration shown in the present embodiment may be used in combination with the integrated sensor 8 in the first embodiment.

1 Glow plug 122 Middle shaft 124
125 Middle shaft insulating member 2 Fixing member 20 Pressure contact portion 200 Pressure contact portion inclined surface 201 Pressure contact portion horizontal surface 21 Base end side holding portion
22 End-side holding part 23 Sealing member 3 Housing 30 Outer cylinder part 31 Load transmission member locking part 32 Male thread part 33 Element housing part 4 Load transmission member 40 Load transmission inner cylinder part 41 Load transmission collar part
5 Combustion pressure detector 50 Piezoelectric element (arrow indicates polarization direction)
6 Control part 7 Input / output part 8 Glow plug integrated combustion pressure sensor 9 Internal combustion engine 90 Combustion chamber 91 Engine head 910 Glow plug fixing screw part 911 Plug hole 912 Seal part seating taper surface 913 Communication hole

Claims (4)

The glow plug (1) provided in the internal combustion engine (9) and generating heat when energized, and the glow plug so that the tip thereof is located inside the communication hole (913) facing the combustion chamber (90) provided in the internal combustion engine A cylindrical fixing member (2) for fixing the pressure, a combustion pressure detection part (5) having a piezoelectric element (50) for detecting pressure by a piezoelectric effect, and combustion generated in the combustion chamber to the combustion pressure detection part A load transmitting member (4) for transmitting pressure, a control unit (6) for controlling energization to the glow plug and controlling input / output to the combustion pressure detecting unit, and input / output between the control unit and the outside And an input / output unit (7) that is integrally housed in a cylindrical housing (3), and that is integrated with a glow plug for the purpose of heating the combustion chamber and detecting the combustion pressure A sensor,
An outer cylinder portion (30) in which the housing extends in a cylindrical shape in the axial direction, a load transmission member locking portion (31) projecting annularly inward at the tip end side, and an engine head (91) of the internal combustion engine Threaded into the female threaded portion (912) of the plug hole (910) provided in the outer cylindrical portion, the male threaded portion (32) provided on the proximal end side of the outer cylinder portion, and the proximal end side of the male threaded portion Comprising an element accommodating portion (33) provided at a position exposed from the engine head;
An inner cylinder portion (40) in which the load transmission material is held inside the outer cylinder portion, one end abuts on the load transmission member locking portion, and the other end is exposed inside the element housing portion; A flange portion (41) extending in an inner cylinder portion and extending in a bowl shape toward the outer diameter direction inside the element housing portion;
A glow plug integrated combustion pressure sensor (8, 8a) characterized in that the flange is brought into contact with the lower surface of the detection part fixed inside the element housing part. A pressure contact portion (20) in which the fixing member projects in a radial shape in a radial direction, a proximal end side holding portion (21) provided on the proximal end side, and a distal end side holding portion (22) provided on the distal end side; Comprising
The pressure contact portion has a pressure contact portion horizontal surface (201) provided on the base end side so as to be orthogonal to the axis of the glow plug, and a truncated cone shape whose diameter decreases toward the tip. And a press-contact portion inclined surface (200) provided on the tip side thereof,
The lower end surface of the outer cylinder part is brought into contact with the horizontal surface of the pressure contact part,
The said press-contact part inclination surface was made to contact | abut to the seat inclination surface (912) provided so that it might become small diameter toward the front-end | tip between the said plug hole and the said communication hole of the said engine head. Glow plug integrated combustion pressure sensor (8, 8a)   3. The glow plug according to claim 1, wherein at least a part of a conduction path for conducting electricity between the glow plug and the control unit includes a lead portion (124) that is elastically deformable inside the element housing portion. Body combustion pressure sensor (8, 8a)   The glow plug integrated combustion pressure sensor (8) according to any one of claims 1 to 3, wherein the glow plug is a ceramic glow plug.

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