# Patent

## Title
Fuel injection valve equipped with in-cylinder pressure sensor

## Abstract

A fuel injection valve equipped with an in-cylinder pressure sensor is provided in which a fuel injection valve is fitted into an injection valve mounting hole provided in an engine, the fuel injection valve injecting fuel from a front end of a valve housing part into a combustion chamber of the engine, and the in-cylinder pressure sensor, which is cylindrical and has a front end facing the combustion chamber, and a cylindrical signal circuit tube fitted and connected to an inner peripheral face of a rear end of the in-cylinder pressure sensor are fitted and fixed to an outer peripheral face of the valve housing part, housed in the injection valve mounting hole, of the fuel injection valve. In such fuel injection valve, the signal transmission device connected to an in-cylinder pressure sensor does not vibrate within an injection valve mounting hole, thus enabling its durability to be ensured.

## Background
TECHNICAL FIELD
The present invention relates to an improvement of a fuel injection valve equipped with an in-cylinder pressure sensor in which a fuel injection valve is fitted into an injection valve mounting hole provided in an engine, the fuel injection valve directly injecting fuel from a front end of a valve housing into a combustion chamber of the engine, an in-cylinder pressure sensor is attached to the valve housing, the in-cylinder pressure sensor detecting a pressure of the combustion chamber, and signal transmission means is connected to the in-cylinder pressure sensor, the signal transmission means transmitting an output signal thereof to an outside.
BACKGROUND ART
Such a fuel injection valve equipped with an in-cylinder pressure sensor is already known, as disclosed in Patent Document 1.
RELATED ART DOCUMENTS
Patent Documents
Patent Document 1: Japanese Patent Application Laid-open No. 9-53483
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
In the fuel injection valve equipped with an in-cylinder pressure sensor described in Patent Document 1, as signal transmission means for transmitting an output signal from an in-cylinder pressure sensor to the outside, a lead is connected to the in-cylinder pressure sensor, and this is pulled outside while carrying out wiring on one side of a fuel injection valve within an injection valve mounting hole of an engine.
In such an arrangement the lead, which has flexibility, vibrates upon being subjected to vibration of the engine, and there is a possibility that it will make contact with an inner face of the injection valve mounting hole and be damaged.
The present invention has been accomplished in light of such circumstances, and it is an object thereof to provide a fuel injection valve equipped with an in-cylinder pressure sensor in which signal transmission means connected to an in-cylinder pressure sensor does not vibrate within an injection valve mounting hole, thus enabling its durability to be ensured.
Means for Solving the Problems
In order to attain the above object, according to a first aspect of the present invention, there is provided a fuel injection valve equipped with an in-cylinder pressure sensor in which a fuel injection valve is fitted into an injection valve mounting hole provided in an engine, the fuel injection valve directly injecting fuel from a front end of a valve housing part into a combustion chamber of the engine, an in-cylinder pressure sensor is attached to the valve housing part, the in-cylinder pressure sensor detecting a pressure of the combustion chamber, and signal transmission means is connected to the in-cylinder pressure sensor, the signal transmission means transmitting an output signal thereof to an outside, characterized in that the in-cylinder pressure sensor, which is cylindrical and has a front end facing the combustion chamber, and a cylindrical signal circuit tube, as part of the signal transmission means, fitted and connected to an inner peripheral face of a rear end of the in-cylinder pressure sensor are fitted and fixed to an outer peripheral face of the valve housing part, housed in the injection valve mounting hole, of the fuel injection valve.
Further, according to a second aspect of the present invention, in addition to the first aspect, an insulating layer covering the signal circuit tube is formed on an outer periphery of the fuel injection valve.
Furthermore, according to a third aspect of the present invention, in addition to the second aspect, a support ring abutting against a rear end face of the in-cylinder pressure sensor is hermetically fitted around an outer peripheral face of a front end part of the insulating layer, and this support ring is welded to the rear end of the in-cylinder pressure sensor.
Effects of the Invention
In accordance with the first aspect of the present invention, due to the cylindrical in-cylinder pressure sensor, which has the front end facing the combustion chamber, and the cylindrical signal circuit tube, as part of the signal transmission means, which is fitted and connected to the inner peripheral face of the rear end part of the in-cylinder pressure sensor, being fitted around and fixed to the outer peripheral face of the valve housing part, housed in the injection valve mounting hole, of the fuel injection valve, it is unnecessary to employ special positioning when fitting and connecting together the in-cylinder pressure sensor and the signal circuit tube, which are both cylindrical, and the ease of assembly is good. Moreover, since the signal circuit tube fitted around the outer peripheral face of the valve housing part does not vibrate even when subjected to vibration of the engine, even if it is housed within the injection valve mounting hole, it does not make contact with the inner face of the injection valve mounting hole, thus enabling the durability thereof to be maintained.
In accordance with the second aspect of the present invention, due to the insulating layer covering the signal circuit tube being formed on the outer periphery of the fuel injection valve, it is possible by this insulating layer to reliably prevent the signal circuit tube from making contact with the inner face of the injection valve mounting hole while protecting the signal circuit tube.
In accordance with the third aspect of the present invention, due to the support ring abutting against the rear end face of the in-cylinder pressure sensor being hermetically fitted around the outer peripheral face of the front end part of the insulating layer and due to this support ring being joined to the rear end of the in-cylinder pressure sensor by the circumferential weld, it is possible to enhance the support strength for the in-cylinder pressure sensor and it is also possible to ensure a sealed state between the support ring and the insulating layer and in-cylinder pressure sensor.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a cutaway side view of an essential part of a fuel injection valve equipped with an in-cylinder pressure sensor related to the present invention in a state in which it is fitted into an engine. (first embodiment)
FIG. 2 is an enlarged view of part 2 in FIG. 1. (first embodiment)
FIG. 3 is an enlarged sectional view along line 3-3 in FIG. 1. (first embodiment)



EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS


    E Engine
    Ec Combustion chamber
    I Electromagnetic fuel injection valve
    2 Valve housing part
    7 Injection valve mounting hole
    10 In-cylinder pressure sensor
    11 Signal circuit tube
    23 Insulating layer
    25 Signal transmission means
    28 Support ring
    30 Circumferential weld


MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention is explained by reference to the attached drawings.
First Embodiment
First, in FIG. 1, mounted on a cylinder head Eh of an engine E are a fuel injection valve I that can inject fuel directly into a combustion chamber Ec and a fuel distribution pipe D that distributes fuel to the fuel injection valve I. In the fuel injection valve I, the combustion chamber Ec side is defined as the front and the fuel distribution pipe D side is defined as the rear. The fuel injection valve I is formed by coaxially connecting in sequence from the front end toward the rear end a cylindrical valve housing part 2, an intermediate linking part 3, an electromagnetic coil part 4, and a fuel injection tube part 5. When the electromagnetic coil part 4 is energized, a valve within the valve housing part 2 is opened, and the fuel injection tube part 5 injects directly into the combustion chamber Ec fuel that has been fed from the fuel distribution pipe D.
In the fuel injection valve I, the external diameter increases in the order: valve housing part 2, intermediate linking part 3, and electromagnetic coil part 4, the electromagnetic coil part 4 having formed on its rear part a coupler 6 protruding toward one side thereof.
Provided in the cylinder head Eh is an injection valve mounting hole 7 opening on a ceiling face of the combustion chamber Ec, the valve housing part 2 and the intermediate linking part 3 being fitted into the injection valve mounting hole 7, and the fuel injection valve I being mounted on the cylinder head Eh so that a front end face of the electromagnetic coil part 4 abuts against an outer face of the cylinder head Eh.
The valve housing part 2 is provided with a dispensing tip 111 at a front end portion thereof, for dispensing fuel outwardly and into the combustion chamber. As shown in FIGS. 1 and 2, fitted around the outer periphery of the valve housing part 2 are a cylindrical in-cylinder pressure sensor 10, having a front end directly facing the combustion chamber Ec, and a cylindrical signal circuit tube 11 fitted into and electrically connected to the inner periphery of a rear end part of the in-cylinder pressure sensor 10. As shown in FIG. 2, the in-cylinder pressure sensor has an internal annular groove 100 formed inside of a rear end portion thereof, for nestingly receiving a front end portion of the signal circuit tube 11. The inner peripheral edge at the front end of the in-cylinder pressure sensor 10 is joined to the valve housing part 2 by means of a circumferential weld 12. An external annular seal groove 13 is formed on the outer periphery of an intermediate part of the in-cylinder pressure sensor 10, and a seal member 14 that is in intimate contact with an inner peripheral face of the injection valve mounting hole 7 is fitted into the annular seal groove 13. The in-cylinder pressure sensor 10 is formed from, for example, a piezoelectric element.
The rear end of the signal circuit tube 11 extends to a rear end part of the valve housing part 2, and a signal wire 15 extending to the vicinity of the rear end of the electromagnetic coil part 4 via one side of the intermediate linking part 3 and electromagnetic coil part 4 is connected to the rear end of the signal circuit tube 11.
The electromagnetic coil part 4 is formed from a synthetic resin bobbin 17 fitted around the outer periphery of a fixed core 16 that opens the valve within the valve housing part 2 by attraction, a coil 18 wound around the bobbin 17, and a coil housing 19 made of a magnetic material and housing the bobbin 17 and the coil 18. A terminal support part 20 is formed integrally with a rear end part of the bobbin 17, and this terminal support part 20 retains a pair of power supply terminals 21 and a signal terminal 22, the power supply terminals 21 being connected to opposite terminals 18a of the wire of the coil 18, and the signal terminal 22 being connected to the terminal of the signal wire 15.
An insulating layer 23, made of a synthetic resin, is molded on outer peripheral faces of the coil housing 19 and the signal circuit tube 11 so as to continuously cover them.
As shown in FIG. 1 and FIG. 3, the coupler 6 is formed integrally with a rear part of the insulating layer 23 covering the electromagnetic coil part 4, the coupler 6 protruding to one side of the insulating layer 23, base parts of the power supply terminal 21 and the signal terminal 22 being embedded in the coupler 6, and connection end parts thereof being disposed within a connection opening of the coupler 6. In the illustrated example, the connection end part of the signal terminal 22 is disposed between the connection end parts of the pair of power supply terminals 21.
In the above, the signal circuit tube 11, the signal wire 15, and the signal terminal 22 form signal transmission means 25 for transmitting an output signal of the in-cylinder pressure sensor 10 to the outside.
An annular recess 27 is formed on the outer periphery of a front end part of the insulating layer 23, a rear end face of the in-cylinder pressure sensor 10 facing the annular recess 27, in this annular recess 27 a support ring 28 made of a metal (e.g. stainless steel) abutting against the rear end face of the in-cylinder pressure sensor 10 is hermetically fitted around an outer peripheral face of the insulating layer 23 via an adhesive 29, and parts of the support ring 28 and the in-cylinder pressure sensor 10 that abut against each other are joined by a circumferential weld 30.
The operation of this embodiment is now explained.
In the engine E, the fuel injection valve I injects fuel directly into the combustion chamber Ec through a fuel discharge hole opening formed in the dispensing tip 111 at the front end of the valve housing part 2 with predetermined timing. After the fuel has been discharged and ignited, the in-cylinder pressure sensor 10 is subjected to the pressure within the combustion chamber Ec, is compressed in the axial direction, and outputs a voltage signal that depends on the amount of strain, the output signal is transmitted to an electronic control unit (not illustrated) connected to the signal terminal 22 via the signal circuit tube 11 and the signal wire 15, and the pressure of the combustion chamber Ec, that is, the in-cylinder pressure, is calculated there and is utilized for knocking control, etc. It will be understood from the foregoing that the signal circuit tube 11 is electrically conductive, which enables it to transmit the output signal from the in-cylinder pressure sensor 10 to the signal wire 15.
Since the cylindrical in-cylinder pressure sensor 10, which has the front end facing the combustion chamber Ec, and the cylindrical signal circuit tube 11, which is fitted into and connected to the inner peripheral face of the rear end part of the in-cylinder pressure sensor 10, are fitted around and fixed to the outer peripheral face of the valve housing part 2 of the fuel injection valve I housed in the injection valve mounting hole 7 provided in the cylinder head Eh, it is unnecessary to employ special positioning when fitting and connecting together the in-cylinder pressure sensor 10 and the signal circuit tube 11, which are both cylindrical, and the ease of assembly is good. Moreover, since the signal circuit tube 11 fitted around the outer peripheral face of the valve housing part 2 does not vibrate even when subjected to vibration of the engine E, even if it is housed within the injection valve mounting hole 7, it does not make contact with the inner face of the injection valve mounting hole 7, thus enabling the durability thereof to be maintained.
Furthermore, since the outer peripheral face of the signal circuit tube 11 is covered by the insulating layer 23, it is possible by this insulating layer 23 to reliably prevent the signal circuit tube 11 from making contact with the inner face of the injection valve mounting hole 7 while protecting the signal circuit tube 11.
Moreover, since the inner peripheral edge of the front end part of the cylindrical in-cylinder pressure sensor 10 is joined to the valve housing part 2 by the circumferential weld 12, and the rear end part thereof is joined to the support ring 28 hermetically fitted to the insulating layer 23 on the outer periphery of the signal circuit tube 11 by the circumferential weld 30, the in-cylinder pressure sensor 10 is supported via two positions at the front and rear ends, thereby enhancing the support strength therefor. Furthermore, since the in-cylinder pressure sensor 10 and the valve housing part 2 are hermetically joined by the circumferential weld 12, it is possible to prevent high pressure gas from the combustion chamber Ec entering therebetween.
An embodiment of the present invention is explained above, but the present invention is not limited thereto and may be modified in variety of ways as long as the modifications do not depart from the spirit and scope thereof.

## Claims

1. A fuel injection valve equipped with an in-cylinder pressure sensor, in which
the fuel injection valve is configured to be fitted into an injection valve mounting hole provided in an engine, the fuel injection valve capable of directly injecting fuel from a dispensing tip situated at a front end of a valve housing part thereof into a combustion chamber of the engine,
the in-cylinder pressure sensor is coaxial with, and attached to the valve housing part and surrounds the front end of the valve housing part in an area proximate the dispensing tip, the in-cylinder pressure sensor operable to detect a pressure of the combustion chamber, and
a signal transmission device is connected to the in-cylinder pressure sensor, the signal transmission device configured to transmit an output signal thereof to an outside, wherein:
the in-cylinder pressure sensor, which is cylindrical, has a front end configured for placement directly facing the combustion chamber, said front end being substantially aligned with said dispensing tip;

an electrically conductive cylindrical signal circuit tube, as part of the signal transmission device, surrounds a portion of the valve housing part, and is fitted and connected to an inner peripheral face of a rear end of the in-cylinder pressure sensor, and
the in-cylinder pressure sensor and the cylindrical signal circuit tube are fitted and fixed to an outer peripheral face of the valve housing part of the fuel injection valve.

2. The fuel injection valve equipped with an in-cylinder pressure sensor according to claim 1, wherein an insulating layer covers the signal circuit tube.

3. The fuel injection valve equipped with an in-cylinder pressure sensor according to claim 2,
wherein a support ring abutting against a rear end face of the in-cylinder pressure sensor is hermetically fitted around an outer peripheral face of a front end part of the insulating layer, and this support ring is welded to the rear end of the in-cylinder pressure sensor.