JPH05180060A - Mounting method for combustion pressure sensor - Google Patents

Abstract

PURPOSE:To prevent a pressure detecting part from receiving damage even in the case that a point end part of a combustion pressure sensor collides against an engine main unit. CONSTITUTION:An inflammable cushion member 20 of parafin or styrene foam is provided on an external surface of a diaphragm 31, normally exposed in a combustion chamber, in a pressure detecting part 3 provided in a point end part of a combustion pressure sensor 1. The sensor 1, in a condition that this cushion member 20 is provided, is mounted to be screwed to a mounting hole, formed in a cylinder head, so that the combustion chamber communicates with the outside. Even when the point end part of the sensor 1 collides against the cylinder head, since this impact energy is absorbed by the cushion member 20 and prevented from being transmitted to the pressure detecting part 3, its damage is prevented. Since the cushion member 20 is burned to disappear after mounting, no influence is given to detection of pressure thereafter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of mounting a combustion pressure sensor for detecting a combustion pressure of an internal combustion engine which has a pressure detecting portion at its tip.

[0002]

2. Description of the Related Art Conventionally, an internal combustion engine has a structure in which a pressure detecting portion for converting combustion pressure into an electric signal is provided at a tip portion thereof, and an amplifying circuit for amplifying an electric signal from the pressure detecting portion is provided in a main body portion. A combustion pressure sensor that is attached to an engine body (for example, a cylinder head) so as to expose a pressure detection portion in a combustion chamber of the engine and detects a combustion pressure during operation of an internal combustion engine is known (Japanese Patent Laid-Open No. 61-107127). .. This type of combustion pressure sensor mounting method is generally provided with a mounting hole that connects the combustion chamber and the outside to the engine body, and a screw is formed on a part of the inner surface of the engine body so that the outer peripheral surface of one of the combustion pressure sensors is also mounted. A screw is formed to screw with the screw. Then, the combustion pressure sensor is inserted into the mounting hole from the outside of the engine body with the pressure detection portion at the tip side, and then the combustion pressure sensor is screwed into the mounting hole to firmly attach the combustion pressure sensor to the engine body. .. In this state, the pressure detection part of the combustion pressure sensor is exposed to the combustion chamber, and the combustion chamber is completely sealed by the screwing of the sensor and the engine body and the gasket provided between them. The sensor is in a state where it can detect the combustion pressure.

[0003]

However, in the conventional method for mounting the combustion pressure sensor, when the tip of the sensor is accidentally applied to the engine body when the combustion pressure sensor is mounted on the engine body, the sensor tip Direct impact may be applied to the pressure detection part provided on the pressure detection part, resulting in deformation or scratches on the diaphragm that constitutes the pressure detection part, or destruction of the piezoelectric element that converts pressure into an electrical signal. There is. When the diaphragm is deformed, the way the combustion pressure is transmitted changes, causing characteristic fluctuations.If the diaphragm is damaged, the diaphragm that is constantly distorted by the combustion pressure may break from the damaged part. This is a factor that greatly reduces the reliability of the completed internal combustion engine.

Therefore, the present invention has been made in view of the above problems. When the combustion pressure sensor is mounted, the transmission of the external force acting on the combustion pressure sensor to the pressure detecting portion is relaxed,
An object of the present invention is to provide a method for mounting a combustion pressure sensor that can prevent damage to the pressure detection unit even when the tip of the combustion pressure sensor collides with the engine body.

[0005]

In order to achieve the above object, the present invention provides a method for mounting a combustion pressure sensor in which a combustion pressure sensor having a pressure detecting portion at its tip is mounted in a hole facing the combustion chamber of an internal combustion engine. In the above configuration, the combustion pressure sensor is mounted with the pressure detection portion of the combustion pressure sensor covered with a combustible buffer member.

[0006]

In the present invention, the buffer member absorbs the energy of the impact even when the tip of the combustion pressure sensor collides with the engine body of the internal combustion engine, and the impact force is transmitted to the pressure detection unit. Alleviate that. As a result, it is possible to prevent damage to the pressure detection unit due to collision. Further, since the cushioning member is a flammable material, the cushioning member is burned by the combustion of the internal combustion engine and disappears from around the pressure detection unit after the combustion pressure sensor is mounted in the hole, and the combustion pressure Does not affect detection.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing the structure of a combustion pressure sensor before mounting in an embodiment of a method for mounting a combustion pressure sensor according to the present invention.

In the figure, reference numeral 2 is a housing made of stainless steel (SUS430), and a screw portion 2a is formed on the outer periphery of the small diameter portion. 3 is provided at the tip of the housing 2, and is a pressure detection unit for converting combustion pressure into a potential difference, as will be described later, 4 is a lead wire extending from the pressure detection unit 3, and 5 is connected to the other end of the lead wire 4. HIC (hybrid IC) amplifier for amplifying the potential difference from the pressure detection unit 3, 6 and 7 guide the lead wire 4 in the housing 2 and a resin spacer for fixing the HIC amplifier 5, and 8 is an iron- A shield case made of a nickel alloy, 9 is provided on the shield case 8, and H
An annular feedthrough capacitor that inserts the lead wire 10 from the IC amplifier 5, 11 is a contact pin support member that supports the contact pin 12 that is connected to the lead wire 10 and is connected to the outside, and 13 is molded by resin. It is a connector housing.

Reference numeral 20 is a flammable cushioning member provided so as to cover the tip portion of the pressure detecting portion 3, which is a main part of the present invention. The cushioning member 20 will be described later in detail.

FIG. 2 is a partial sectional view for explaining the structure of the pressure detecting section 3.

In the figure, 31 is a combustion chamber (not shown).
The diaphragm is exposed to the outside, 32 is zirconia, 33 is a hemispherical portion, 34 and 36 are devitron glass, 35 is a silicon (Si) chip, and 37 is hermetic. When the combustion pressure is applied to the diaphragm 31, the pressure is applied through the zirconia 32 and the hemisphere 33 to the devitron glass 34, 36.
It is transmitted to the Si chip 35 sandwiched between. Then, the resistance incorporated in the Si chip 35 receives strain stress. When the resistance is distorted, the resistance changes due to the piezo effect. Since this resistor is assembled in a bridge as shown in FIG. 3, a potential difference ΔV is generated. This potential difference ΔV is the above H
It is amplified by the IC amplifier 5 and output to the outside.

Here, the zirconia 32 is the diaphragm 3
It is configured such that it is simply sandwiched between the 1 and the hemispherical portion 33 without being adhered, so that the combustion pressure received by the diaphragm 31 is accurately transmitted to the Si chip 35. In this way, the pressure detection unit 3 has a precise structure. Therefore, when the combustion pressure sensor 1 is mounted on the engine body by mistake, if the pressure detection unit 3, particularly the diaphragm 31 not covered by the housing 2, collides with the engine body, the following problems occur. there is a possibility. This problem has already been mentioned above, but will be explained in more detail here.

Scratches and Cracks on Diaphragm 31 Since the diaphragm 31 is constantly strained by combustion pressure, it is considered that if there are scratches or cracks, the diaphragm 31 will rupture from that portion.

Deformation of Diaphragm 31 As described above, the zirconia 32 is not adhered, and the convex portion 31a at the central portion of the diaphragm 31 and the hemispherical portion 3 are not bonded.
It is only sandwiched by 3. Therefore, when the diaphragm 31 is deformed by the impact force, the zirconia 32 is displaced or tilted to change the way of transmitting the combustion pressure and cause the characteristic variation.

Destruction of element When the tip of the combustion pressure sensor 1 is applied to the engine body, the impact is 1
It may exceed 000G (G is gravitational acceleration). With respect to such a strong impact, it is conceivable that breakage may occur at the interface between the devitron glass 34 and the Si chip 35, which is a partly weak material.

Therefore, in this embodiment, as shown in FIG. 1, the combustion pressure sensor 1 is attached to the engine body with the cushioning member 20 having an appropriate thickness dimension provided on the outer surface of the diaphragm 31. By providing the cushioning member 20 on the outer surface of the diaphragm 31, even when the tip portion of the combustion pressure sensor 1 collides with the engine body, the cushioning member 20 absorbs the energy of the impact and is transmitted to the diaphragm 31. It is possible to sufficiently reduce the impact force. As a result, it is possible to prevent most of the above-mentioned problems of the pressure detection unit 3 caused by the impact force due to the collision. The pressure detector 3
Since the outer peripheral portion is covered with the housing 2 made of stainless steel as described above, a sufficient effect can be obtained only by providing the cushioning member 20 on the outer surface of the diaphragm 31 as in this embodiment.

4 and 5 are views for explaining a method of mounting the combustion pressure sensor 1 shown in FIG. 1 on an internal combustion engine. FIG. 4 shows a state before mounting. In the figure, 41 is a cylinder head, 42 is a cylinder block, and 43 is a combustion chamber. The cylinder head 41 is formed with a mounting hole 44 for the combustion pressure sensor 1 that communicates the combustion chamber 43 with the outside, and a screw portion 44a is formed on the inner peripheral surface thereof. On the other hand, in the combustion pressure sensor 1, as described with reference to FIG. 1, the cushioning member 20 is provided on the outer surface of the diaphragm 31, which is the tip of the sensor 1. In order to insert the tip of the combustion pressure sensor 1 into the mounting hole 44, the combustion pressure sensor 1 is set to the position shown in the figure, and then the screw portion 2a of the housing 2 is screwed into the screw portion 44a of the mounting hole 44. . Even if the tip of the sensor 1 accidentally collides with the opening end of the mounting hole 44 or another portion of the cylinder head 41 during the movement of the sensor 1, the pressure detector 3 is Since the outer periphery is covered with the housing 2 as described above and the cushioning member 20 is provided on the outer surface of the diaphragm 31, the pressure detection unit 3 is prevented from being damaged by the collision as described above. In the figure, reference numeral 45 is an annular gasket for preventing the combustion gas from leaking to the outside.

FIG. 5 shows a state where the combustion pressure sensor 1 is completely attached. In FIG. 4, the combustion pressure sensor 1 is firmly fixed to the cylinder head 41 by advancing the screwing of the screw portions 2a and 44a to a predetermined position where the housing 2 and the cylinder head 41 hold the gasket 45 as shown in FIG. And is in a state where the seal by the gasket 45 acts. In this state, the cushioning member 20 is still provided on the outer surface of the diaphragm 31. Here, since the cushioning member 20 is formed of a flammable material as described above, it is burned by combustion of the internal combustion engine during the first operation after the completion of the assembly of the internal combustion engine, and as a result, the combustion pressure sensor 1 has the diaphragm 31. Is in a normal state in which the front surface of is exposed to the combustion chamber 43 side. Therefore, even if the combustion pressure sensor 1 is mounted in the mounting hole 44 while the cushioning member 20 is provided as described above, it does not affect the detection of the combustion pressure of the combustion pressure sensor 1 after the mounting, and the combustion pressure sensor is not affected. 1 can perform stable and accurate combustion pressure detection. In addition, the cushioning member 2
Even if 0 burns, it has no effect on the subsequent operation of the internal combustion engine or purification of exhaust gas.

As described above, the cushioning member 20 provided in the pressure detecting section 3 is required to have excellent cushioning properties and be combustible so that no burnt residue is produced. Currently, as a material satisfying the above requirements and having excellent workability,
Buffering materials such as paraffin and styrofoam are considered suitable.

In the description of the above embodiment, the case where the sensor 1 collides with the engine body (cylinder head 41) has been described. However, when an impact force is applied to the pressure detecting portion 3 in addition to that, for example, it is completed. Even when the combustion pressure sensor is transported to an assembly plant of an internal combustion engine, the cushioning member 20 is used.
Protects the pressure detector 3, and the present invention works effectively.

[0021]

As described above, according to the present invention, the impact pressure transmitted to the pressure detecting portion is alleviated even when the combustion pressure sensor receives an impact force, so that the combustion pressure sensor is mounted on the internal combustion engine. At this time, for example, even when the tip of the combustion pressure sensor collides with the engine body of the internal combustion engine, it is possible to prevent the pressure detection unit from being damaged. Further, since the flammable cushioning member does not affect the detection of the combustion pressure by being burned by the combustion of the internal combustion engine after the combustion pressure sensor is mounted, it is stable and accurate even by the method of mounting the combustion pressure sensor of the present invention. Various combustion pressures can be detected.

[Brief description of drawings]

FIG. 1 is a sectional view of the configuration of a combustion pressure sensor before being mounted in an embodiment of a method for mounting a combustion pressure sensor according to the present invention.

FIG. 2 is a partial cross-sectional view illustrating the configuration of a pressure detection unit in FIG.

FIG. 3 is a diagram illustrating an output signal of a combustion pressure sensor.

FIG. 4 is a diagram illustrating a method for mounting the combustion pressure sensor shown in FIG. 1 on an internal combustion engine, showing a state before the combustion pressure sensor is mounted.

5 is a diagram for explaining a method for mounting the combustion pressure sensor shown in FIG. 1 on an internal combustion engine, showing a state where the combustion pressure sensor is completely mounted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion pressure sensor 2 Housing 2a, 44a Screw part 3 Pressure detection part 5 HIC amplifier 20 Buffer member 31 Diaphragm 32 Zirconia 33 Hemisphere part 34,36 Devitron glass 35 Silicon (Si) chip 37 Hermetic 41 Cylinder head 42 Cylinder block 43 Combustion Chamber 44 Mounting hole 45 Gasket

Claims (1)

[Claims] 1. A method of mounting a combustion pressure sensor, wherein a combustion pressure sensor having a pressure detection portion at its tip is mounted in a hole facing the combustion chamber of an internal combustion engine, wherein the pressure detection portion of the combustion pressure sensor is a flammable buffer. A method for mounting a combustion pressure sensor, characterized in that the combustion pressure sensor is mounted while being covered with a member.