JPH05332871A - Indicator - Google Patents

Abstract

PURPOSE:To obtain a diaphragm type indicator without errors in attachment, errors caused by temperature change at a part to be attached and errors caused by temperature change in fluid, whose pressure is to be measured. CONSTITUTION:A ring-shaped gap is formed between the surrounding part of a diaphragm 1 and a main-body screw part 3. Heat resisting rubber bodies 2a and 2b are embedded in the gap. The rear surface of the diaphragm 1 is connected to an elastic part 4 such as a strain generating tube, and the strain generated in the elastic part 4 is detected. In consideration for use in an internal combustion engine and the like, the rear surface of the diaphragm, the elastic part 4 and a strain detecting part 5 are cooled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid pressure measuring device.

[0002]

2. Description of the Related Art Diaphragm-type acupressure gauges have been used to measure fluctuating pressure such as cylinder internal pressure of an internal combustion engine. As shown in FIG. 7, the acupressure meter includes a metal diaphragm, an elastic component such as a strain-flexing cylinder or a piezoelectric element, and a portion for detecting strain generated in the elastic component. The periphery of the diaphragm is fixed to the threaded portion of the main body by welding or the like. One end of the elastic component is joined to the back surface of the diaphragm and the other end is fixed to the main body. There is also a type that does not have an elastic body part and directly detects the deflection of the diaphragm. Normally, a cooling mechanism such as water cooling is provided, but there is also a non-cooling type.

When pressure is applied to the diaphragm of such a acupressure meter, the diaphragm bends and strain occurs in the elastic component. By detecting this strain, the pressure applied to the diaphragm is known.

[0004]

If the periphery of the diaphragm is fixed to the threaded portion of the main body, various errors will occur and the measurement accuracy will decrease, as described below.

(A) For example, consider mounting a finger pressure gauge by screwing it into a cylinder head or the like. At this time, the threaded portion of the main body generally extends. Due to the extension of the threaded portion of the main body, the diaphragm also comes out to the surface side. However, since the elastic body part is connected to the back surface of the diaphragm and the other end of this elastic body part is fixed to the main body, the central part of the diaphragm is dented and the elastic body part is stretched. When such elastic strain occurs in the elastic component, an indication value appears as if negative pressure is applied to the diaphragm. In other words, just by attaching the acupressure gauge, the finger degree of the acupressure gauge changes.

(B) Next, consider that the temperature of the attached portion changes after the acupressure meter is attached. If the internal combustion engine is installed, the temperature will rise. Then, first, the attached portion thermally expands. Thereby, the main body screw portion is stretched. In addition, the temperature of the threaded portion of the main body also rises, causing thermal expansion. When the temperature of the attached portion rises in this way, the main body screw portion of the acupressure meter extends. Then, similarly to the case of (a), elongation strain occurs in the elastic body component. On the contrary, when the temperature of the mounted part drops,
A contraction strain occurs in the elastic component. Even if the temperature of the attached portion changes after the acupressure meter is attached in this way, the finger degree of the acupressure meter changes.

(C) Consider also the case where the temperature of the fluid whose pressure is to be measured is different from the temperature of the cooling water. For example, the temperature of the gas in the cylinder of an internal combustion engine exceeds 2000 ° C during combustion. In such a case, the temperature of the surface of the diaphragm rises. Since the back side is water-cooled, the temperature does not rise much. In this way, a temperature distribution is generated inside the diaphragm, and a temperature difference occurs between the front and back. Then, due to thermal expansion, the diaphragm is generally deformed so as to pop out to the surface side. Since the periphery of the diaphragm is fixed to the threaded portion of the main body, and the elastic body component is connected to the back surface of the diaphragm, elongation strain occurs in this elastic body component. On the contrary, when the fluid temperature becomes lower than the temperature of the cooling water, the diaphragm is deformed to the back side, and the elastic component is distorted by contraction. Thus, even when the temperature of the fluid whose pressure is to be measured changes, the finger pressure of the acupressure meter changes.

As described above, in the fixed-periphery diaphragm type acupressure meter, there is a finger change, that is, an error, which should not be present. In the case of measuring the pressure in the cylinder of an internal combustion engine, these errors reach several percent of the rated pressure of the acupressure gauge.
For example, it is almost impossible to determine the atmospheric pressure line. As described above, it is very difficult to measure the pressure with high accuracy by the peripheral fixed diaphragm type acupressure meter. The problem to be solved by the present invention is to provide a acupressure meter without the above-mentioned error.

[0009]

The acupressure meter of the present invention solves the problems clarified in the preceding paragraph and has the following structure. 1 to 4 are overall views of the acupressure meter. 5 and 6 are views of a portion in which a rubber-like object is embedded in the annular gap.

The periphery of the diaphragm is not fixed to the screw portion of the main body, but is separated from each other. This is an annular gap, and this gap is filled with a heat-resistant rubber-like object.
Alternatively, a ring-shaped part is made of a heat-resistant rubber-like object and fitted into the annular gap. The reason for using a rubber-like object is that the surface of the diaphragm is subject to the pressure to be measured, so that the front and back sides must be isolated from each other, but the connection between the periphery of the diaphragm and the threaded part of the main body should be as loose as possible.

In this acupressure meter, since the periphery of the diaphragm is substantially floated from the main body in this way, a component for supporting the diaphragm on the back surface of the diaphragm is indispensable. An elastic body component such as a strain generating cylinder or a piezoelectric element is used for this. One end of the elastic component is joined to the back surface of the diaphragm, and the other end is fixed to the main body. Then, the strain generated in the elastic component is detected. There are various methods for the configuration of the rubber-like object in the gap around the diaphragm and the strain detection of the elastic body part. This is described in the example section. Since this acupressure meter can be used at high temperature such as measuring the pressure in the cylinder of the internal combustion engine, the back surface of the diaphragm, the elastic component and the strain detecting section are cooled.

[0012]

As can be seen from the above description, in the acupressure meter of the present invention, when pressure is applied to the diaphragm, this force is almost received by the elastic member. The body thread is also subjected to force via the rubber-like object around the diaphragm, but only slightly. Due to the pressure, a contraction strain is generated in the elastic body part. By detecting this strain, the pressure applied to the diaphragm is known.

Next, the reason why the three types of errors that have occurred in the peripheral fixed diaphragm type acupressure meter do not occur in the present acupressure meter will be explained. (A) The same applies to this acupressure meter that the main body thread portion is extended by attaching the acupressure meter. In the acupressure meter in which a rubber-like object is buried, when the main body screw portion extends, the outer periphery of the rubber-like object adhered to the main body screw portion appears on the diaphragm surface side together with the main body screw portion. However, the periphery of the diaphragm is bonded to the inner circumference of the rubber-like object, and it hardly moves here. The reason can be understood by comparing the elastic rigidity of the rubber-like object with the elastic rigidity of the diaphragm and the elastic body part. Diaphragm and elastic parts are much stiffer than rubber-like objects. Therefore, even if the threaded portion of the main body extends, the diaphragm and the elastic body component are hardly deformed, and the deformation occurs exclusively in the rubber-like object portion. Therefore, the elastic component is not distorted, and the change of the finger index can be eliminated. The same explanation can be applied to the case where a ring-shaped rubber-like object is fitted in the gap. In this way, in this acupressure meter, an error does not occur by attaching the acupressure meter.

(B) Even when the expansion of the main body screw portion is based on the temperature rise of the attached portion and the main body screw portion, the diaphragm and the elastic body component are not deformed as in the case of (a). If the temperature is not rising but is falling, the screw part of the main body contracts. In this case, the rubber-like object is only deformed with the opposite sign to that at the time of ascending, and the diaphragm and the elastic member are not deformed as in the case of ascending. As described above, in the acupressure meter, even if the temperature of the attached portion changes after the acupressure meter is attached, an error due to this does not occur.

(C) Since the back surface of the diaphragm is cooled also in this acupressure meter, when the temperature of the fluid whose pressure is to be measured is different from the cooling water temperature, a temperature difference occurs between the front and back surfaces of the diaphragm, and the diaphragm is thermally deformed. .. However, from the comparison between the stiffness of the rubber-like object and the stiffness of the diaphragm and the elastic body component, the axial component of the thermal deformation of the diaphragm becomes almost equal to the amount of displacement between the inner and outer circumferences of the rubber-like object, and the diaphragm and the elastic body component The junction hardly moves. That is, the elastic body part is hardly deformed. That is, even if the fluid temperature changes, the error does not occur.
As described above, it is understood that the various errors that have occurred in the peripheral fixed diaphragm type acupressure meter do not occur in this acupressure meter.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the acupressure meter of the present invention, there are various methods as described below regarding the construction of a rubber-like object in the annular gap between the periphery of the diaphragm and the threaded portion of the main body and the strain detection of the elastic member. A. Regarding the configuration of the rubber-like object (a) A configuration in which, for example, RTV silicone rubber is used as the rubber-like object to fill the annular gap. This is shown in FIG. (B) A ring-shaped part made of a rubber-like object is fitted in the annular gap. This is shown in FIG.

B. Regarding Strain Detection Method (a) A strain detection method in which a metal cylinder is used as the elastic body component and a strain gauge is attached to the surface thereof. This is shown in FIG. (B) A strain detection method in which a metal cylinder is used as the elastic component, and an electrostatic capacitance is formed between the electrode that moves by expansion and contraction of the cylinder and the electrode that is fixed to the main body. This is shown in FIG. (C) A metal cylinder is used as the elastic component, and the ferromagnetic piece is moved by the expansion and contraction of the cylinder. Meanwhile, the coil is fixed to the main body. When a magnetic circuit is formed by the ferromagnetic piece and this coil, the inductance of the coil changes according to the expansion and contraction of the metal cylinder. Distortion detection method using this. This is shown in FIG. (D) A strain detection method in which a piezoelectric element is used as an elastic component and electric charges generated in the piezoelectric element are extracted. This is shown in FIG. The acupressure meter of the present invention can be constructed by using any combination of the above A and B.

[0018]

As described above, the acupressure meter of the present invention is, in principle, an acupressure error which should not occur in the conventional fixed peripheral diaphragm type acupressure meter. The effects of this acupressure meter are summarized as follows. (A) An error does not occur when the finger pressure gauge is screwed into the measured portion and attached. (B) The error does not occur even if the temperature of the attached portion changes. (C) Even if the temperature of the fluid whose pressure is to be measured changes, this does not cause an error.

From the above (a) and (b), the acupressure meter of the present invention makes it possible to determine the atmospheric pressure line when measuring the pressure in the cylinder of an internal combustion engine, for example. Further, from (c), the pressure of a high temperature fluid such as combustion gas or conversely the temperature of a low temperature fluid can be measured without error. It is possible to perform highly accurate measurement in other general pressure measurement.

[Brief description of drawings]

FIG. 1 is a acupressure meter in which the elastic component is a metal cylinder and has a strain gauge type detection unit. FIG. 2 shows a acupressure meter in which the elastic component is a metal cylinder and has a capacitance type detection unit. FIG. 3 shows a acupressure meter in which the elastic component is a metal cylinder and has an inductance type detection unit. FIG. 4 shows a finger pressure gauge in which the elastic component and the detection unit are piezoelectric elements. FIG. 5 shows a configuration in which a rubber-like object is filled in the annular gap. Figure 6
Shows a structure in which a ring-shaped part made of a rubber-like object is fitted in the annular gap. FIG. 7 shows a conventional diaphragm type acupressure meter in which the periphery of the diaphragm is fixed to the threaded portion of the main body by welding or the like. As an example, the one with a strain gauge type detector is taken up.

[Explanation of symbols]

1, 11, 21, 31, 41 Diaphragm 2a, 12a, 22a, 32a Mechanism for filling a rubber-like object in the annular gap 2b, 12b, 22b, 32b Mechanism for fitting a ring-shaped part made of a rubber-like object in the annular gap 3 , 13, 23, 33, 43 Main body screw part 4, 14, 24, 34, 44 Elastic body part (metal cylinder or piezoelectric element) 5, 15, 25, 35, 45 Strain detection part (strain gauge type, capacitance Type, inductance type, piezoelectric type) 6, 16, 26, 36, 46 Cooling mechanism 7, 17, 27, 37, 47 Output signal extraction section

Claims (1)

[Claims] 1. A diaphragm (1, 11, 21, 3)
Utilizing the phenomenon that the diaphragm (1 etc.) bends when pressure is applied to 1), in a finger pressure gauge equipped with a cooling mechanism (7, 17, 27, 37), (a) diaphragm (1 etc.) and main body screw part (3, 1
3, 23, 33) and an annular gap is formed between the rubber-like objects (2a, 12a, 22a, 32a, 2b,
12b, 22b, 32b) to secure airtightness, and (b) an elastic component (4, 14, 24, 3) that is joined to the diaphragm (1 or the like) and supports the diaphragm (1 or the like).
4), and (c) a portion (5, 15, 25, 35) for detecting the strain generated in the elastic component (4, etc.).