JPH03175330A - Apparatus for detecting differential pressure - Google Patents

Abstract

PURPOSE:To remove the fluctuation of stray capacity caused by the fine displacement of a ring by guiding one pressure from the through-hole opened to the bottom surface of the hole of a housing and guiding the other pressure from the through-hole communicating with the differential pressure sensor of a press member. CONSTITUTION:A spring washer 9 as an elastic member is inserted between the left end surface of a ring 2 and the right end surface of a press metal fitting 8. The ring 2 is pressed to the perforated bottom surface of a housing 1 by the energizing force of the washer 9 to be fixed to the housing 1. As a result, the fluctuation of stray capacity caused by the fine displacement of the ring 2 in the axial line direction thereof is removed.

Description

[Detailed description of the invention] [Industrial application field]

The present invention particularly relates to a capacitance type differential pressure detection device that is designed to improve the reproducibility of slope characteristics.

[Conventional technology]

A conventional example will be described with reference to FIG. 3, which is a sectional view thereof. In FIG. 3, reference numeral 1 denotes a columnar housing made of stainless steel, in which a large-diameter bottomed hole is drilled on the left side, and a small-diameter hole is drilled through the bottom surface on the right side. 22
is a thick-walled cylindrical ring made of ceramic, the outer periphery of which fits into the bottomed hole of the housing 1, and three holes for passing through lead bins, which will be described later, are bored in the side wall at right angles to the axis. Reference numeral 6 denotes a differential pressure sensor, which is joined to the right end surface of the presser metal fitting 8 with an insulating plate 7 interposed therebetween. The presser metal fitting 8 is a disc-shaped member having a center hole,
Its outer periphery fits into the bottomed hole of the housing 1, and the right end surface is fitted with a ring 22.
is pressed and fixed against the bottom surface of the bottomed hole of the casing 1, and welded on the inner surface of the bottomed hole. At this time, the differential pressure sensor 6 is positioned so as to be accommodated in the hole in the center of the ring 22. On the other hand, three lead bins 4 are 1-metically sealed to a terminal block 5, and this terminal block 5 is welded to the side wall of the housing 1. Before welding, three ceramic vibrators 3 are inserted into three holes drilled in the side wall of the housing 1, and the corresponding lead pins 4 pass through the center hole of each vibrator 3. This is the order in which the terminal blocks 5 are welded. Each lead pin 4 passes through a hole in the side wall of the ring 22,
The tips are in conductive contact with the outer peripheral surfaces of the fixed and movable electrodes of the differential pressure sensor 6. Although not shown in detail, each lead pin 4 has a structure in which the tip thereof is movable in the axial direction and is biased in the direction of extending outward. A lid 10 has a center hole and is welded to the left end of the housing 1. Annular waveforms are formed on the right end surface of the housing 1 and the left end surface of the lid 10, respectively. Closely opposing this corrugated surface, a seal diaphragm 11 is attached to the housing 1. Each of the peripheral edges of the lid body 10 is welded, and an incompressible fluid such as silicone oil is filled as a sealed liquid in the opposing space and the internal pores and spaces communicating therewith. The pressure acting on the outside of each sealing diaphragm 11 is transmitted via the fill liquid and acts on each side of the movable electrode in the form of an unmarked measuring diaphragm of the differential pressure sensor 6 to displace it. , changes the capacitance between each fixed electrode (not marked). This capacitance is taken out by each lead pin 4, and based on this, the difference between the respective pressures on both sides, that is, the differential pressure is detected.

[Problem to be solved by the invention]

In the conventional technology as explained above, the axis of the bottomed hole of the housing 1 and the bottom surface are not accurately perpendicular to each other, and the ends of each end face of the ring 22 on both sides are not accurately perpendicular to the axis. If the right angle of the right end surface of the presser metal fitting 8 with the axis is not accurate, there may be a slight difference between the ring 22 and the bottom of the bottomed hole of the housing 1, and also between the right end surface of the presser metal fitting 8. This will create a play gap. Moreover, the play between the members may increase due to welding distortion of the presser metal fitting 8 with the housing l. When the ring 22 is slightly displaced in the axial direction due to this play, the stray capacitance formed between the ring 22 and the fixed and movable electrodes will fluctuate. , which would interfere with accurate differential pressure detection based on the capacitance between the movable electrodes. In particular, it reduces the reproducibility of the slope characteristics of the differential pressure detection device. For example, if you now tilt the differential pressure detection device left and right,
The history of the zero point signal error represents the reproducibility of the zero point. In this case, it is assumed that the vibrator 3 is sufficiently firmly fixed so as not to move relative to the housing 1. FIG. 4 is a history diagram, that is, a characteristic diagram of zero point reproducibility. The horizontal axis shows the left and right tilt angles (positive direction to the right, negative direction to the left)
, the error (%) of the zero point signal is plotted on the vertical axis. From the initial state with no tilt, it is tilted 90 degrees to the right, then once it returns to the initial state, it is tilted 90 degrees to the left, and then it returns to the initial state again. The change in zero point signal error when returning is shown by a solid line with an arrow. As is clear from the figure, the maximum variation width of the zero point signal error is 3.5%, and the reproducibility of the zero point is poor. An object of the present invention is to provide a capacitance type differential pressure detection device that solves the above-mentioned problems of the conventional technology and improves the reproducibility of slope characteristics. Means for Solving the Problem] In order to solve this problem, a differential pressure detection device according to the present invention includes: a housing having a bottom and a hole; an outer circumferential surface fitting into the inner surface of the hole; , a ring having a through hole in the center, one end surface of which is in contact with the bottom surface, and in which a capacitance type differential pressure sensor is housed; a holding member having a mating outer circumferential surface, to which the differential pressure sensor is joined via an insulating member, and fixed to the housing; the other end face of the ring and the end face of the holding member opposite thereto; and an elastic member interposed in a pressed state between the two, wherein one pressure is guided from a through hole opening at the bottom of the hole of the housing, and the other is guided from the through hole of the pressing member leading to the differential pressure sensor. pressure is applied.

[For use]

One end surface of the ring is pressed against the bottom surface of the hole in the housing by the elastic member, and the ring is fixed to the housing. As a result, fluctuations in stray capacitance caused by minute displacements of the ring are eliminated.

【Example】

Embodiments of the differential pressure detection device according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of this embodiment. In Figure 1,
The difference between this embodiment and the conventional example shown in FIG. 3 is that a spring washer as an elastic member is interposed between the left end surface of the ring and the right end surface of the holding fitting. Note that the same members as in the conventional example are given the same reference numerals. That is, a spring washer 9 is interposed in a pressed state between each opposing end surface of the ring 2 and the presser metal fitting 8, and the ring 2 is pressed against the bottom surface of the bottomed hole of the housing 1 by the biasing force of the spring washer 9. , is firmly fixed to the housing 1. As a result, fluctuations in stray capacitance caused by minute displacements of the ring 2 in the axial direction are eliminated. FIG. 2 is a characteristic diagram of zero point reproducibility in the slope characteristic in the embodiment, and corresponds to FIG. 4 in the conventional example. As is clear from FIG. 2, the maximum variation width of the zero point signal error in the example is zero, and it can be said that the example has extremely accurate reproducibility.

【Effect of the invention】

As explained above, in this invention, one end surface of the ring is pressed against the bottom surface of the hole in the casing by the elastic member and fixed to the casing, and as a result, the ring is fixed to the casing due to minute displacement of the ring. Stray capacitance fluctuations are eliminated. Therefore, according to the present invention, the maximum fluctuation width of the zero point signal error representing the zero point reproducibility when the device is tilted from side to side, which is one of the tilt characteristics of the differential pressure detection device, is 3.
Although it used to be 5%, it is reduced to almost zero in the example, and there is a remarkable improvement effect in that the cost increase can be kept extremely low.

[Brief explanation of drawings]

Fig. 1 is a sectional view of an embodiment according to the present invention, Fig. 2 is a characteristic diagram showing zero point reproducibility in the embodiment, Fig. 3 is a sectional view of a conventional example, and Fig. 4 shows zero point reproducibility in the conventional example. FIG. Symbol explanation: Housing, 2: Ring, : Pipe, 4: Lead bin, : Differential pressure sensor, : Insulating plate, Calculation (%) 4th side rabbit

Claims (1)

[Claims] 1) A housing in which a hole is drilled and has a bottom surface; an outer peripheral surface fits into the inner surface of the hole, one end surface contacts the bottom surface, and a through hole in which a capacitance type differential pressure sensor is housed. a ring having a center portion thereof; an end surface opposite to the other end surface of the ring; and an outer circumferential surface that fits into the inner surface of the hole, the differential pressure sensor being joined via an insulating member, and the housing a pressing member fixed to the body; and an elastic member interposed in a pressed state between the other end surface of the ring and the opposing end surface of the pressing member; A differential pressure detection device characterized in that one pressure is applied through a through hole that communicates with the differential pressure sensor, and the other pressure is applied through a through hole that communicates with the differential pressure sensor of the holding member.