JPH0631396Y2 - Cylinder pressure sensor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sensor for detecting the internal pressure of a cylinder of an internal combustion engine, in which a support body having a displacement conversion element bonded on the surface of a collar is provided.
The spark plug is inserted through the opening provided in the flange, and the inner edge of the flange holds down the end surface of the spark plug so that the spark plug is connected to the outer wall of the cylinder so that it can move like knocking. Not only fast changes,
The internal pressure displacement, which moves slowly, can be reliably detected.

2. Description of the Related Art Recently, in order to improve engine efficiency in an internal combustion engine, research and development has been conducted on a system for detecting the behavior of a cylinder during combustion by a physical sensor and analyzing it to control an optimum ignition timing. A knock sensor is a typical example of a physical sensor used in such a control system. The main purpose of this is to detect knocking caused by abnormal combustion and shift the ignition timing to a position where knocking does not occur, but recently, in order to improve engine efficiency and fuel cost, knocking near the limit where knocking occurs There is a change to a method of advancing the ignition timing and applying feedback control to maintain the optimum ignition timing. In order to effectively realize such complicated control, it is necessary to obtain crank angle information and combustion pressure information in the cylinder and then comprehensively control the ignition timing based on these information.

As means for obtaining the combustion pressure information, a pressure detector is incorporated in an insertion hole provided in the cylinder, or, as shown in FIG. 7, a flange portion 101 of the spark plug 1 and an outer wall surface of the cylinder 2. In the meantime, an attempt has been made to clamp the washer-like piezoelectric element 3 and detect the displacement of the ignition plug 1 due to the change in internal pressure by the piezoelectric element 3.

Problems to be Solved by the Invention However, in the structure in which the pressure sensor is incorporated into the insertion hole provided in the cylinder, it is difficult to secure a mounting space, and the pressure sensor is directly exposed to high temperature. Therefore, it has not been put to practical use.

Further, in the structure shown in FIG. 7, since the piezoelectric element 3 bears a large mass of the ignition plug, it is more preferable than the pressure sensor.
Rather, it works as an accelerometer. Therefore, it is possible to follow a quick response such as a knocking signal, but it is not possible to follow a crank angle-cylinder pressure change that changes relatively slowly. For example, as shown in Fig. 2B, it is possible to follow the knocking signal (a) generated near the maximum pressure point, but it becomes the maximum pressure from ignition to top dead center, and the cylinder pressure change that decreases Cannot follow.

Means for Solving the Problems In order to solve the above-mentioned conventional problems, a cylinder internal pressure sensor according to the present invention is a support body provided with a collar portion having an opening portion at the other end and a coupling portion at the other end. And a displacement conversion element joined to the surface of the collar portion of the support body, the support body passes through the opening, and an ignition plug attached to a cylinder head of an internal combustion engine is inserted. The connecting portion is connected to the outer wall portion of the cylinder head such that the inner end edge of the flange portion holds down the end surface of the spark plug.

By the combustion pressure generated in the cylinder by the ignition explosion,
The spark plug is lifted up. Since the end surface of the spark plug is held down by the inner end edge of the collar portion of the support body connected to the outer wall of the cylinder, the collar portion of the support body is bent and displaced in accordance with the above-described movement of the spark plug.
Since the displacement conversion element is joined to the surface of the collar portion, the displacement conversion element detects the bending displacement of the collar portion due to the change in the cylinder internal pressure. Here, the support body is configured to hold down the end surface of the spark plug and does not carry the mass of the spark plug on its back, so not only a quick response such as a knocking signal but also a crank angle-combustion pressure change characteristic, It can reliably follow gradual changes.

Embodiment FIG. 1 is a partial sectional view of a cylinder internal pressure sensor according to the present invention. In the figure, the same reference numerals as those in FIG. 7 indicate the same components, and 4 is a support and 5 is a displacement conversion element. The support body 4 is formed into a cylindrical shape using a material having excellent heat resistance, such as metal or porcelain, and a connecting portion 41 by a screw is provided on the inner peripheral surface on one end side in the axial direction, and the other end side is formed. The structure is provided by providing a collar 43 having an opening 42. Then, the spark plug 1 mounted on the cylinder 2 of the internal combustion engine is inserted through the opening 42, and the inner end edge of the flange portion 43 holds down the end surface of the flange portion 101 of the spark plug 1 to form a connecting portion. 41 is connected to the outer wall of the cylinder 2. Reference numeral 21 denotes a screw portion connected to the connecting portion 41 of the support body 4.

The displacement conversion element 5 is bonded to the surface of the collar portion 43 of the support body 4. The displacement conversion element 5 can be composed of a piezoelectric element, a strain gauge, or the like. Generally, piezoelectric elements are superior to strain gauges in terms of heat resistance, so piezoelectric elements are more suitable for this type of cylinder internal pressure sensor, but even strain gauges have high heat resistance. If it can be solved, it can be used. In this embodiment, the displacement conversion element 5 is a piezoelectric element. As shown in FIGS. 2 and 3, the electrodes 5 are formed on both surfaces of the piezoelectric element body 51 formed in a donut shape.
2 and 53 are formed in a ring shape, and the electrode 53 is adhesively fixed to the outer surface of the collar portion 43 of the support body 4 by using an adhesive. As shown in FIG. 4, the electrodes 52 and 53 have electrodes (521, 522), (531,
532), it may be formed by being divided into a plurality of parts. Further, as shown in FIG. 5, the displacement conversion element 5 may be joined to the inner surface side of the collar portion 43 of the support body 4. Incidentally, 54, 55
Is a lead wire.

In the cylinder internal pressure sensor having the above-described configuration, as shown in FIG. 6, the ignition plug 1 is lifted upward as shown by an arrow a by the combustion pressure P generated in the inside 22 of the cylinder 2 by ignition explosion. Collar 101 of the spark plug 1
Since the end face of the support body 4 is restrained by the inner edge of the collar portion 43 of the support body 4, the bending displacement of the collar portion 43 of the support body 5 is caused by following the movement of the ignition plug 1 in the direction of the arrow (a). Occurs. Since the displacement conversion element 5 is joined to the surface of the flange portion 43, the bending displacement of the flange portion 43 is converted into an electric signal by the displacement conversion element 5. Here, since the support body 4 is configured to hold down the end surface of the spark plug 1 and does not bear the mass of the spark plug 1, the quick response knocking signal (in the crank angle-cylinder pressure change characteristic of FIG. 8) ( Not only b) but also the slow response crank angle-cylinder pressure change can be reliably followed.

Effect of the Invention As described above, the cylinder internal pressure sensor according to the present invention includes a support body provided with a collar portion having a connecting portion on one end side and an opening portion on the other end side, and the collar portion of the support body. A displacement conversion element bonded on the surface, the support body allows an ignition plug attached to a cylinder of an internal combustion engine to pass through the opening, and the ignition is performed by an inner end edge of the flange portion. Since the connecting portion is connected to the outer wall portion of the cylinder so as to hold down the end surface of the plug, not only a quick response such as a knocking signal but also a loose crank angle-combustion pressure change characteristic. It is possible to provide a cylinder internal pressure sensor suitable for a system that can reliably follow such changes, detects the behavior of the cylinder internal pressure during combustion, and controls the optimum ignition timing. Wear.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a cylinder internal pressure sensor according to the present invention, and FIG. 2 is a cross-sectional view showing an assembly structure of a support and a displacement conversion element which constitute the cylinder internal pressure sensor according to the present invention.
Similar to the drawing, its plan view, FIG. 4 is a plan view of another embodiment, FIG. 5 is a sectional view of another embodiment, and FIG. 6 illustrates the operation of the cylinder pressure sensor according to the present invention. FIG. 7 is a partial sectional view of a conventional cylinder internal pressure sensor, and FIG. 8 is a crank angle-cylinder internal pressure characteristic diagram. DESCRIPTION OF SYMBOLS 1 ... Spark plug, 2 ... Cylinder 4 ... Supporting body, 41 ... Connection part 42 ... Opening part, 43 ... Collar part 5 ... Displacement conversion element

Claims (4)

[Scope of utility model registration request] 1. A support body having a connecting portion on one end side and a collar portion having an opening portion on the other end side, and a displacement conversion element joined to the surface of the collar portion of the support body, The support is
An ignition plug attached to a cylinder of an internal combustion engine is inserted through the opening, and an inner end edge of the flange portion holds down an end surface of the ignition plug, so that the connecting portion is attached to an outer wall portion of the cylinder. Cylinder pressure sensor characterized by being connected. 2. The utility model registration claim characterized in that the displacement conversion element is bonded to the inner surface of the collar portion.
In-cylinder pressure sensor according to item. 3. The utility model registration claim, wherein the displacement conversion element is joined to an outer surface of the collar portion.
In-cylinder pressure sensor according to item. 4. The cylinder pressure sensor according to claim 1, 2, or 3, wherein the displacement conversion element is a piezoelectric element.