JP2000277232A - Spark plug with built-in pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spark plug equipped with a built-in pressure sensor capable of enhancing efficiency of the plug mounting works. SOLUTION: This spark plug is structured with a plug body 11 accommodated in and fixed to one end of an outer cylinder 24 capable of being accommodated in a plug mounting hole, while a connector 70 is fixed to the other end. An ignition coil consisting of a primary coil 65 wound on a primary bobbin 64 and a secondary coil 63 wound on a secondary bobbin 62 is accommodated inside the outer cylinder 24 and connected with a terminal 13 by lead wires 26. The output of a pressure sensor accommodated in a sensor case 50 is outputted to a pin 74 of a connector 70 via an impedance conversion circuit on a circuit board 67 via a tape electric wired 60. To the primary coil 65, a battery voltage is supplied from a pin (not shown).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark plug having a built-in pressure sensor for detecting a pressure in a combustion chamber of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, a spark plug having a built-in pressure sensor for detecting a pressure in a combustion chamber of an internal combustion engine has been used for detecting a combustion state and knocking, or improving a fuel consumption rate and purifying exhaust gas. It has been known. FIG.
FIG. 3 is an explanatory view showing a conventional spark plug with a built-in pressure sensor including a partial cross section. The spark plug 200 with a built-in pressure sensor has an insulator 2 made of alumina or the like.
0 is provided. The insulator 20 has a corrugation portion 22 formed on the rear end side and a leg long portion 24 formed on the front end side. Inside the insulator 20, the central shaft 1
A shaft hole 26 is formed along the line 8. The terminal 13 is accommodated in the inner rear end side of the shaft hole 26, and the rear end of the terminal 13 protrudes from the rear end of the corrugation portion 22. The center electrode 12 electrically connected to the terminal 13 is housed inside the shaft hole 26 and at the tip end of the terminal 13. The center electrode 12 is formed in a rod shape from a nickel alloy such as Inconel.
The tip of 2 protrudes from the tip of the leg long part 24.

[0003] The distal end side of the insulator 20 is housed inside a metallic shell 30 formed in a cylindrical shape.
A male screw portion 31 for screwing into a female screw portion formed in the engine head is formed on the outer peripheral surface of the tip of the engine head. The ground electrode 16 is fixed to the tip of the metal shell 30, and a spark discharge occurs between the tip of the ground electrode 16 and the tip of the center electrode 12. A metal sensor case 50 having a built-in pressure sensor is formed on the outer peripheral surface on the rear end side of the male screw portion 31. The sensor case 50 has a diameter larger than the nominal diameter of the male screw portion 31 and is formed to protrude in a brim shape.

A ring-shaped plate packing 51 is provided on the inner bottom surface of the sensor case 50, and a ring-shaped piezoelectric element 53 is provided on the plate packing 51 so as to overlap. A ring-shaped electrode plate 54 is provided on the piezoelectric element 53 in an overlapping manner, and a ring-shaped insulating plate 55 is provided on the electrode plate 54 in an overlapping manner. A terminal 54a is formed on the electrode plate 54 so as to protrude therefrom.
And the conductor 56a of the lead wire 56 are connected.
The pressure sensor is constituted by the insulating plate 55, the electrode plate 54, the terminal 54a, the piezoelectric element 53 and the plate packing 51.

The center electrode 12 and the ground electrode 16
When the air-fuel mixture in the combustion chamber is ignited by the spark discharge during the combustion and the air-fuel mixture burns, and pressure is generated in the combustion chamber, the pressure is transmitted to the piezoelectric element 53 via the gasket 40 and the insulating plate 51. According to the transmitted pressure, the piezoelectric element 5
3, a voltage due to the piezoelectric effect is generated, and a signal having the voltage is output from the electrode plate 54 through the lead wire 56 to an impedance conversion circuit (not shown). Subsequently, the impedance conversion circuit converts the impedance of the input signal, and converts the converted signal into an ECU provided in the vehicle.
Output to Then, the ECU executes the determination of knocking, the calculation of the fuel consumption rate, and the like based on the received signal, and sends the result to a predetermined control circuit to perform combustion control.

[0006]

However, in the above-described conventional spark plug 200 with a built-in pressure sensor, the lead wire 56 is led out from the sensor case 50 as shown in FIG. When the is mounted in the plug mounting hole of the internal combustion engine, it hinders the mounting operation. The spark plug 20 with a built-in pressure sensor
In addition to connecting the high voltage cable to the terminal 13 of the
Since it is necessary to route the wire 6 and connect it to a predetermined terminal, it is troublesome. That is, the conventional spark plug 200 with a built-in pressure sensor has a problem in that the processing of the lead wire 56 is troublesome and the efficiency of the plug mounting work is reduced.

Accordingly, an object of the present invention is to realize a spark plug with a built-in pressure sensor that can increase the efficiency of the plug mounting operation.

[0008]

Means for Solving the Problems, Functions and Effects The present invention achieves the above object by claim 1 to claim 6.
In the invention described in the above, the pressure sensor for detecting the pressure of the combustion chamber of the internal combustion engine, a plug body having a discharge unit for performing a discharge in the combustion chamber, a sensor output terminal for extracting the output of the pressure sensor, A connection member to which a voltage supply terminal for supplying a voltage to the portion is attached, and a tubular member that can be accommodated in a plug attachment hole provided in the internal combustion engine, and one end of the tubular member has the plug The main body is housed and fixed with the discharge portion protruding from the one end, and the connection member is attached to the other end of the cylindrical member, the sensor output terminal and the pressure sensor, and the voltage supply The terminal and the discharge part are each electrically connected inside the tubular member, and employ a technical means called a spark plug with a built-in pressure sensor.

That is, the sensor output terminal of the connection member attached to the other end of the tubular member and the pressure sensor of the plug body fixedly accommodated in one end of the tubular member are electrically connected inside the tubular member. Because it is connected, as before,
When the plug body is mounted in the plug mounting hole, the lead wire does not interfere. In addition, there is no need to perform the operation of routing the lead wires and connecting to the terminals. Therefore, a spark plug with a built-in pressure sensor that can increase the efficiency of the plug mounting operation can be realized. Further, a supply terminal for supplying a voltage to the discharge portion is attached to the connection member, and the voltage supply terminal and the discharge portion of the plug body are electrically connected inside the tubular member. For example, as described in an embodiment of the invention to be described later, using a cable with a plug that can be connected to both the sensor output terminal and the voltage supply terminal at a time allows more efficient operation than connecting each terminal. Can be enhanced.

According to a second aspect of the present invention, in the spark plug with a built-in pressure sensor according to the first aspect, an impedance conversion circuit for converting the output impedance of the pressure sensor is provided inside the cylindrical member. The impedance conversion circuit employs a technical means of being electrically connected to the sensor output terminal.

That is, since the output of the pressure sensor has a high impedance, if the lead wire is led out of the plug mounting hole and connected to the terminal without converting the impedance as in the prior art, the waterproofness of the connection portion becomes a problem. ,
Although the reliability of pressure detection is impaired, by providing the impedance conversion circuit inside the tubular member, there is no problem of waterproofness, and the reliability of pressure detection can be improved.

According to a third aspect of the present invention, in the spark plug with a built-in pressure sensor according to the first or second aspect, the tightening portion for applying a tool for tightening and fixing the plug body to the plug mounting hole is provided. Employ the technical means of being provided.

That is, a tool can be applied to the fastening portion to fasten and fix the plug body to the plug attachment hole, thereby facilitating the work of attaching the plug.

According to a fourth aspect of the present invention, in the spark plug with a built-in pressure sensor according to any one of the first to third aspects, an ignition coil is provided inside the cylindrical member, and the ignition coil is provided. The coil employs a technical means that it is electrically connected to the voltage supply terminal and the discharge unit.

In other words, by providing the ignition coil inside the tubular member, the space for mounting the ignition coil can be reduced as in the conventional case, so that the space (for example, engine room) in which the internal combustion engine is provided can be reduced. Space saving can be achieved. In addition, since the distance from the ignition coil to the discharge unit can be shortened, the loss of the supply voltage can be reduced, and the ignitability can be improved.

According to a fifth aspect of the present invention, in the spark plug with the built-in pressure sensor according to the third or fourth aspect, the fastening portion is formed on an outer peripheral surface of the connection member. Is adopted.

That is, since the connecting member is attached to the other end of the cylindrical member and is located on the opening side of the plug mounting hole, a fastening portion is formed on the outer peripheral surface of the connecting member, so that the connecting member is used. Tightening work becomes easy.

According to a sixth aspect of the present invention, in the spark plug with a built-in pressure sensor according to any one of the first to fifth aspects, the tubular member is formed of a magnetic material. Adopt means.

That is, since the sensor output terminal and the pressure sensor are electrically connected inside the tubular member, noise is mixed into the output of the pressure sensor by forming the tubular member from a magnetic material, It is possible to eliminate a situation in which the accuracy of pressure detection is reduced. In the case where the impedance conversion circuit is provided inside the cylindrical member, the cylindrical member is formed of a magnetic material to prevent noise from being mixed into the impedance conversion circuit and reduce the pressure detection accuracy. Can also.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a spark plug with a built-in pressure sensor according to the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view showing a spark plug with a built-in pressure sensor of the present embodiment, including a partial cross-sectional view. FIG.
The same reference numerals are used for the same components as the conventional spark plug 200 with a built-in pressure sensor shown in FIG.

The spark plug 10 with a built-in pressure sensor includes:
A cylindrical outer cylinder 24 is provided, and a cylindrical inner cylinder 23 is fixed to an inner surface of one end of the outer cylinder 24. The plug main body 11 is housed and fixed to the inner cylinder 23, and a connector 70 is attached to the other end of the outer cylinder 24.
The plug body 11 has a state in which a discharge portion including the center electrode 12 and the ground electrode 16 is projected from the outer cylinder 24, and the outer peripheral surface of the sensor case 50 and the inner peripheral surface of the inner cylinder 23 are fixed. . In the present embodiment, the inner cylinder 23 and the outer cylinder 24 are formed of a ferromagnetic material such as SUS430. The outer cylinder 24 has a thickness of 1 mm and an outer diameter of 23 mm, and the inner cylinder 23 has a thickness of 1.4 mm and an outer diameter of 22 mm.
mm. Further, the inner cylinder 23 and the outer cylinder 2
4, the inner cylinder 23 and the sensor case 50, and the outer cylinder 24 and the connector 70 are respectively fixed by laser welding.

A cylindrical primary bobbin 64 is housed inside the outer cylinder 24, and a primary coil 65 is wound around the outer peripheral surface of the primary bobbin 64. Primary bobbin 6
4, a secondary bobbin 62 formed in a screw shape is accommodated therein, and an outer peripheral surface of the secondary bobbin 62 is
A secondary coil 63 is wound between the screws 62a, and a rod-shaped iron core 61 is housed inside the secondary bobbin 62. Column-shaped lower end 62 of secondary bobbin 62
“b” is connected to the electrode member 27 having a T-shaped vertical section. The secondary coil 63 is connected to the electrode member 27 through the inside of the bottom 62b.

The rod-like member 27a formed at the lower part of the electrode member 27 is inserted into the upper part of the joint block 25 whose horizontal cross section has a long hole shape, and the terminal of the plug body 11 is inserted at the lower part of the joint block 25. 13 is inserted. The terminal 13 and the electrode member 27 are connected by the conducting wire 26. A window 25a is formed in the center of the joint block 25 in a horizontal direction so that the connection of the conductor 26 can be performed through the window 25a. In the present embodiment, the joint block 25 is formed of a synthetic resin.

A circuit board 67 provided with an impedance conversion circuit (indicated by 65a in FIG. 3) for converting the output impedance of the pressure sensor is mounted on the upper surface of the cylindrical upper end 66 of the secondary bobbin 62. I have. The input terminal of the circuit board 67 is connected to the pressure sensor by a tape wire 60. Here, the tape electric wire has a structure in which a sheet-like resin is bonded to a conductive wire such as a copper wire, and a copper foil is bonded. The upper portion of the circuit board 67 is filled with silicone rubber 68 for waterproofing. As shown in FIG. 3, the impedance conversion circuit 65a
Is an operational amplifier IC1, a resistor R2 for determining a negative input bias voltage of the operational amplifier IC1, and an operational amplifier IC1.
R3, R that determine the threshold voltage of the + input of
4 and a resistor R1 and a capacitor C1 forming a negative feedback circuit. In the present embodiment, the output voltage of the impedance conversion circuit 65a when the electric charge generated from the piezoelectric element of the pressure sensor is 100 pC is about 5.5 mV.

Next, the configuration of the connector 70 will be described with reference to FIGS. FIG. 2A is a front explanatory view including a partial cross section of the connector 70, and FIG.
(B) is an explanatory plan view of the connector 70. FIG.
FIG. 4A is an explanatory diagram showing a plane of a plug connected to the connector shown in FIG. 2 and a connection relationship between pin connection terminals, and FIG. 4B is a front explanatory diagram of the plug. Connector 70
Is provided with a cylindrical pedestal 76, and the pedestal 76 is housed and fixed to the inner surface at the other end of the outer cylinder 24.
A board 79 is fixed to the upper surface of the pedestal 76, and five pins 71 to 75 are respectively inserted and fixed to the board 79 in a direction perpendicular to the plate surface direction of the board 79. I have. Pins 73 and 7 protruding from the lower surface of substrate 79
4 and 75 have lead wires 73a and 74, respectively.
a and 75a are connected. Although not shown, the pin 7
Lead wires are also connected to the base ends of 1, 72, respectively.

On the upper surface of the pedestal 76, a fastening portion 77 having an outer peripheral surface formed in the shape of a hexagonal nut is formed.
A cylindrical base 78 is fixed inside the fastening portion so as to surround each pin. In this embodiment, the board 79 is formed of a synthetic resin,
The outer diameter φ1 of the pedestal 77 is 22 mm. FIG.
As shown in (A), the plug 96 is formed in a shape corresponding to the inner surface shape of the base 78 of the connector 70, and an elongated hole-shaped pin connection is formed at a position corresponding to the pins 71 to 75 of the connector 70. Terminals 91 to 95 are formed.
The pin connection terminals 91 to 95 are formed of a conductive member, and lead wires 93a, 94a, and 95a are connected to base ends of the pin connection terminals 93, 94, and 95, respectively. Although not shown, lead wires are also connected to the base ends of the pin connection terminals 91 and 92, respectively, and each lead wire is housed inside the cable 97.

A protrusion 78a is formed on the base 78 of the connector 70 so as to protrude from the inner surface of the base, and a recess 96a having a shape corresponding to the protrusion 78a is formed on the plug 96. That is, the plug 9 is inserted so that the projection 78a of the base 78 is accommodated in the recess 96a of the plug 96.
When the connector 6 is connected to the connector 70, the pins 71 to 75 of the connector 70 are necessarily inserted and connected to the pin connection terminals 91 to 95 of the plug 96, respectively.

The pin connection terminal 91 is connected to an igniter 102 provided in the vehicle.
Is connected to a battery 100 provided in the vehicle. The pin connection terminal 93 is a ground terminal, and the pin connection terminal 94 is a pressure detection circuit 104 provided in the vehicle.
, And the pin connection terminal 95 is connected to the regulator circuit 108. Also, pins 71 and 72
The primary coil 6 is connected to the primary coil 6 through lead holes 66a and 66b formed through the upper end 66 of the secondary bobbin 62.
The pin 71 supplies an igniter signal from the igniter 102 to the primary coil 65 via a pin connection terminal 91, and the pin 72 connects to the battery 100 via a pin connection terminal 92. A voltage is supplied to the primary coil 65. The pin 73 is a ground terminal, and the pin 74 is connected to the output of the impedance conversion circuit 67a provided on the circuit board 67, and outputs the output signal of the impedance conversion circuit 67a to the pin connection terminal 94.

Further, the pin 75 supplies a constant voltage supplied from the regulator circuit 108 via the pin connection terminal 95 to the impedance conversion circuit 67a. In the present embodiment, the voltage of the battery is +12 V, and the constant voltage supplied from the regulator circuit is +5 V.

Next, the steps from the mounting of the spark plug 10 with a built-in pressure sensor having the above configuration to the detection of pressure will be described. First,
The outer cylinder 24 is housed in the plug mounting hole with the plug body 11 facing downward, and the male screw 31 is screwed into the female screw formed at the bottom of the plug mounting hole by turning the outer cylinder 24 by hand. Then, when the screw cannot be screwed in by hand, a plug wrench is applied to the tightening portion 77 of the connector 70, and the male screw portion 31 is tightened and fixed to the female screw portion by the plug wrench. Next, the plug 96 is connected along the base 78 of the connector 70. When the ignition key is turned, the primary coil 6 is transferred from the battery 100 through the pin connection terminal 92 and the pin 72 of the plug 96.
5, a high voltage boosted by the secondary coil is supplied to the plug main body 11 through the electrode member 27 and the conducting wire 26, and discharge is performed between the center electrode 12 and the ground electrode 16.

The discharge ignites the air-fuel mixture in the combustion chamber, and the combustion of the air-fuel mixture increases the pressure in the combustion chamber. Subsequently, the pressure is transmitted to the piezoelectric element 53 via the gasket 40 and the insulating plate 51, and a voltage is generated in the piezoelectric element 53 by a piezoelectric effect. Subsequently, the signal having the voltage is input from the terminal 54 a of the electrode plate 54 to the impedance conversion circuit 67 a provided on the circuit board 67 through the tape wire 60 and is amplified. The amplified signal is output to the pressure detection circuit 104 via the pin 74 and the pin connection terminal 94, and the pressure detection circuit 104
From the ECU 106. And the ECU 10
6 detects knocking based on the acquired signal,
Alternatively, the combustion consumption rate is calculated, and the combustion control is performed based on those results.

As described above, in the spark plug 10 with a built-in pressure sensor of the present embodiment, the pressure sensor and the connector 70 for extracting the output of the pressure sensor to the outside are electrically connected inside the outer cylinder 24. Therefore, the lead wire 56 (FIG. 5) does not interfere with the plug tightening work as in the related art. Moreover, with only a very simple operation of connecting the plug 96 to the connector 70,
The output of the pressure sensor and the supply of the voltage to the plug body 11 can be simultaneously performed, and the connection of the high-voltage cable to the plug and the connection of the lead wire 56 of the pressure sensor to the terminal are separately performed as in the related art. Work efficiency can be improved as compared with the case of performing.

Further, since the circuit board 67 provided with the impedance conversion circuit 67a having a high output impedance is provided inside the outer cylinder 24, there is no problem of waterproofing, so that the reliability of pressure detection can be improved. Can be.
In particular, since the outer cylinder 24 and the inner cylinder 23 are formed of a ferromagnetic material, it is possible to eliminate a situation in which noise is mixed in the output of the pressure sensor and the accuracy of pressure detection is reduced.

The pin 74 corresponds to the output terminal of the present invention, and the pin 72 corresponds to the voltage supply terminal. The connector 70 corresponds to the connection member, and the inner cylinder 23 and the outer cylinder 2
4 corresponds to a cylindrical member.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a spark plug with a built-in pressure sensor according to an embodiment of the present invention, including a partial cross-sectional view.

FIG. 2A is a front explanatory view showing a partial cross section of the connector 70, and FIG.
FIG.

FIG. 3 is an explanatory diagram illustrating a configuration of an impedance conversion circuit.

FIG. 4A is an explanatory diagram showing a plane of a plug connected to the connector shown in FIG. 2 and a connection relationship between pin connection terminals, and FIG. 4B is a front explanatory diagram of the plug; .

FIG. 5 is an explanatory view showing a conventional spark plug with a built-in pressure sensor including a partial cross section.

[Explanation of symbols]

 Reference Signs List 10 Spark plug with built-in pressure sensor 11 Plug body 23 Inner cylinder (cylindrical member) 24 Outer cylinder (cylindrical member) 25 Joint block 26 Conductor 50 Sensor case 60 Tape wire 61 Iron core 62 Secondary bobbin 63 Secondary coil 64 Primary Bobbin 65 Primary coil 67 Circuit board 68 Silicon rubber 70 Connector (connection member) 72 pin (voltage supply terminal) 74 pin (output terminal) 77 Fastening part

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitsuru Kondo 14-18, Takatsuji-cho, Mizuho-ku, Nagoya-shi Inside Japan Special Ceramics Co., Ltd. (72) Inventor Takahiro Suzuki 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi F term in reference (reference) 2F055 AA23 BB14 CC14 EE23 FF43 GG11 3G019 KA23 KA28 KD17 KD20 5G059 AA10 CC02 JJ19 KK01 KK14 KK30

Claims (6)

[Claims] 1. A plug body having a pressure sensor for detecting a pressure in a combustion chamber of an internal combustion engine, a discharge unit for discharging in the combustion chamber, a sensor output terminal for extracting an output of the pressure sensor, and the discharge unit A connection member provided with a voltage supply terminal for supplying a voltage to the internal combustion engine, and a cylindrical member accommodating in a plug mounting hole provided in the internal combustion engine. Is fixedly accommodated in a state where the discharge portion is projected from the one end, and the other end of the tubular member is attached with the connection member, the sensor output terminal and the pressure sensor, and the voltage supply terminal. A spark plug with a built-in pressure sensor, wherein the spark plug and the discharge unit are electrically connected to each other inside the tubular member. 2. An impedance conversion circuit for converting an output impedance of the pressure sensor is provided inside the cylindrical member, and the impedance conversion circuit is electrically connected to the sensor output terminal. The spark plug with a built-in pressure sensor according to claim 1. 3. The spark plug with a built-in pressure sensor according to claim 1, further comprising a tightening portion to which a tool for tightening and fixing the plug main body to the plug mounting hole is provided. . 4. An ignition coil is provided inside the cylindrical member, and the ignition coil is electrically connected to the voltage supply terminal and the discharge unit. Any one of 3
4. A spark plug with a built-in pressure sensor according to (1). 5. The spark plug with a built-in pressure sensor according to claim 3, wherein the fastening portion is formed on an outer peripheral surface of the connection member. 6. The spark plug with a built-in pressure sensor according to claim 1, wherein the tubular member is formed of a magnetic material.