JPS5814971B2 - negative pressure gauge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for accurately and reliably measuring atmospheric pressure below atmospheric pressure by applying a piezoresistive effect element.

BACKGROUND OF THE INVENTION It is desired to measure the pressure inside a carburetor for the purpose of fuel supply, monitoring, and control in order to obtain optimal combustion efficiency in automobile engines and the like.

Negative pressure gauges mounted on such automobile engines are required to have high reliability because they are used over a wide range of ambient temperatures (and under harsh conditions such as vibration).

It is also necessary that the structure is suitable for mass production.

An object of the present invention is to provide a negative pressure gauge that satisfies these conditions.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a side sectional view showing the configuration of the negative pressure gauge of the present invention.

In the figure, 1 is a pressure receiving plate, and a flexible member 2 with pleats on the periphery.
The outer flat portion 3 is fixed to the inside of the cylindrical casing 4.

The pressure receiving plate 1 further has a cylindrical collar 5 adhesively fixed to its lower surface, and a pleated flexible member 6 on the lower peripheral edge of the collar 5.
is fixed and supported and fixed to the housing 4 by a fixing collar 1 and a pressure plate supporting ring 8.

On the other hand, a pin 9 is attached to a part of the pressure receiving plate 1 in order to transmit the force received by the pressure receiving plate to the piezoelectric transducer.

The other end of the pin 9 is connected to a beam 10 as a rotatable hinge as shown in FIG.
0 so that no rotational distortion occurs.

The other end of the beam 10 is a ring-shaped insulator 1 as shown in FIG.
Piezoresistance effect elements 14 and 15 made of a pair of semiconductors are rotatably supported by support pins 13 in cut grooves 12 provided in the beam 10, sandwiched between the upper and lower surfaces of the beam 10 and the insulator 11, and bonded together. Fixed.

The piezoresistance effect elements 14 and 15 are inserted into grooves 16 and 1γ provided in the beam 10, and further fixed with an adhesive.

The insulator 11 supporting the beam 10 and the piezoresistive elements 14 and 15 is further fixed to a fixed base 20 via a ring support 18 with an adjusting screw 19.

The lower part of the cylindrical casing 4 is hermetically sealed by a lower cap 21, and a glass pipe 22 is inserted into the center of the lower cap 21, through which the air is exhausted.

Further, the upper part of the pressure receiving plate 1 is hermetically sealed with an upper cap 23, and the atmospheric pressure to be measured is introduced through a hole pipe 24.

When the inside of the airtight chamber constituted by the pressure receiving plate 1, the cylindrical casing 4, and the lower cap 21 is evacuated through the glass pipe 22 to create a vacuum, the pressure receiving plate 1 is pulled downward from the neutral position. stand still.

In this position, the position of the insulator 11 shall be adjusted using the fixing base 20 and the adjustment screw 19 so that the beam 10 is exactly horizontal, that is, extends to the piezoresistive elements 14 and 15, and no force such as compression is applied. do.

In this state, when a pressure lower than the atmospheric pressure to be measured is introduced into the airtight chamber closed by the pressure receiving plate 1 and the upper cap 23 through the air hole pipe 24, the pressure receiving plate 1 moves downward because the lower airtight chamber is a vacuum. Move from the lowered position to the position where it balances with the atmospheric pressure just introduced.

At this time, the force received by the pressure plate 1 is transmitted to the beam 10 through the pin 9, and as the tip of the beam 10 is pulled upward, elongation and compression strains are applied to the pair of piezoresistive elements 14 and 15, respectively. It will be done.

As a result, the resistance values of the pair of piezoresistance effect elements 14 and 15 change depending on the amount of strain.

This change in electrical resistance is extracted as an electrical signal by a bridge circuit shown in FIG. 4, which uses these elements as arms.

E in Figure 4.

is a DC power supply, Ro is the resistance value of the piezoresistance effect element 14.15, RL is the load resistance, and eo is the output signal voltage.

The change in resistance R8 causes the pixel elements 14 and 15 to operate in a push-pull manner, resulting in a signal output voltage e.

is expressed as, where the change in R0 is ΔR, and the DC power supply voltage E.

and is proportional to the resistance change ΔR.

By arranging two piezoresistance effect elements close to each other and configuring and operating a bridge circuit in this manner, the temperature characteristics of the elements cancel each other out, resulting in extremely good temperature characteristics as a whole.

Furthermore, as mentioned above, when no negative pressure is applied to be measured, both piezoresistive elements are at the neutral position,
When negative pressure is introduced from the air hole pipe 24, the pressure receiving plate 1 is pulled upward, the tip of the beam 10 moves upward, and an unbalanced strain is applied to the piezoresistive elements 14 and 15. As long as negative air pressure is not applied, no strain is applied to the piezoresistive element and its fixed portion, and there is little risk of creep.

As described above, in the present invention, the other end of the pin 9 whose one end is fixed to the pressure receiving plate 1 is rotatably coupled to the free end of the beam 10 whose one end is rotatably supported by the pin 13 on the fixed member. , the free end of this beam 10 is driven by the displacement of the pressure receiving plate 1 due to a pressure change, and a pair of piezoresistive effect elements 14 and 15 are provided between both surfaces of the beam in the driving direction and the fixed member, and the pressure receiving plate is Since it directly applies compression and expansion force to the piezoresistive effect element by the displacement of Without this, it is possible to accurately detect a change in resistance with respect to a change in pressure.

[Brief explanation of drawings]

The figures show an embodiment of the present invention, in which FIG. 1 is a side sectional view, and FIG. 2 is a sectional view of the main part showing the state in which the piezoresistive effect element is installed.
Fig. 3 is a side view of the pin and beam attachment part, and Fig. 4 shows the bridge circuit. 1...Pressure plate, 10...Beam, 14, 15
...Piezoresistance effect element.

Claims (1)

[Claims] 1 One chamber partitioned into two chambers by a pressure receiving plate is made almost evacuated, and the other end of the pin connected to the pressure receiving plate is attached to the free end of a beam whose one end is rotatably supported by a fixed member in the vacuum chamber. A pair of piezoresistance effect elements are attached between both sides of the beam in the rotating direction and the fixed member, which are connected at a hinge part, and partitioned by a pressure plate by a bridge circuit having the pair of piezoresistance effect elements as arms. A negative pressure gauge that measures the negative pressure in the other chamber.