JPH0264431A - Inspecting and calibrating method of fluid pressure sensor - Google Patents

Abstract

PURPOSE:To dispense with special equipment such as a pressure regulating chamber or the like and to enable easy execution of detection and calibration by a method wherein a weight giving an amount of deformation being equal to the one caused by a fluid pressure being used is made to act on a deformation output element of an atmospheric pressure detecting means. CONSTITUTION:In an atmospheric pressure sensor 1, an output circuit is constructed so that an output voltage varies linearly in relation to a change in an atmospheric pressure. While a reference output curve of the sensor 1 is shown by a curve C, it is indefinite actually as shown by curves A and B. After assembling, therefore, an adjusting screw 24 is adjusted under a standard pressure to shift the curves A and B in the direction of a longitudinal axis and thereby to output an initial output V0. Accordingly, the curves A and B turn to be A' and B' respectively. In order to make the curves A' and B' coincide with the curve C, subsequently, a weight 34 weighing corresponding to a barometric pressure 500mB equals to 5,000m above sea level, for instance, is given to the sensor 1, and an output voltage is made to coincide by adjusting a variable resistor 33. Thereby an output curve can be made to coincide with the curve C irrespective of nonuniformity of a spring constant of an atmospheric pressure detecting means 2. Berside, an auxiliary weight 48 is used for correcting the gravity of the weight.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for inspecting and calibrating a sensor that detects fluid pressure such as atmospheric pressure or water pressure. This invention relates to a simple inspection and calibration method for sensors that are extracted as signals.

[Conventional technology]

It is well known that aneroid barometers have been used for barometers, altitude hands, and the like. The aneroid barometer is
It has a structure in which a hollow casing (empty box) is created by connecting the peripheries of two plate-shaped metal plates with concentric folds, and the interior is evacuated. This device measures atmospheric pressure by converting it into the amount of elastic deformation, and has been widely used in the past because of its simple structure and easy handling.

This aneroid barometer has recently come to be used in internal combustion engines as well. That is, fuel for the internal combustion engine needs to be supplied in proportion to the volumetric flow rate of intake air in order to maintain optimal combustion conditions. By the way, as we all know, the density of air is atmospheric pressure.

It varies depending on the temperature, but in the case of a car, it is a flat land (low land)
Because the vehicle travels at high altitudes and at high altitudes, the pressure of the intake air fluctuates greatly.

It depends on the weather conditions, but the atmospheric pressure on flat ground is 1 atm, 101
Even if it is around 3 millibars, it drops significantly to around 500 millibars at a high altitude of 5000 m. Therefore, the amount of change in the ratio of intake air to fuel, that is, the air-fuel ratio (mass ratio) due to atmospheric pressure increases, and atmospheric pressure correction is required.

Therefore, a device has been developed that automatically controls the amount of fuel supplied using an aneroid barometer that is easy to handle.

The aneroid barometer installed in a car needs to be small, so the diameter of the empty chamber is small, at most 20 to 3 inches (In), so it will only shift by about 0.5 W at most when the pressure changes around 500 millibar. Therefore, in order to calibrate indication errors due to variations in the spring constant of individual air cans or to perform automatic control, it is most advantageous to convert the displacement into an electrical signal. is used.

By the way, the conventional method for calibrating a barometric pressure sensor using an aneroid barometer is to place the barometric pressure sensor in a pressure regulating chamber that has been adjusted to the reference pressure for calibration, and the operator also enters the room or uses a small window opened in the pressure regulating chamber. Measures such as performing the work through gloves attached to the body are used.

[Problem to be solved by the invention]

As described above, the conventional method in which a barometric pressure sensor is placed in a reference atmospheric pressure chamber and a worker enters the room or works indirectly from outside through gloves is a device that generates a reference atmospheric pressure,
At the very least, it is necessary to prepare a reference pressure chamber that can accommodate the pressure sensor to be calibrated and perform the necessary operations. Work efficiency is poor as it takes time to adjust the air pressure when putting in and taking out equipment such as air pressure sensors, and inspection and calibration work involves electrical wiring work and adjustment of variable resistors, so work must be done while wearing gloves. In some cases, there is a problem that workability deteriorates.

The present invention has been made focusing on the above problems,
Inspect and calibrate a fluid pressure sensor using an aneroid barometer or a fluid pressure gauge based on a similar measurement principle and having a conversion means for converting the displacement of the fluid pressure gauge into an electrical signal with the same accuracy without using a reference fluid pressure chamber. The purpose is to provide a method that can be used to

[Means to solve the problem]

The configuration of the fluid pressure sensor inspection/calibration method of the present invention to achieve the above object includes a fluid pressure detection means that includes an air container whose interior is at a predetermined atmospheric pressure, and whose shape is elastically deformed by changes in fluid pressure; When calibrating a barometric pressure sensor comprising a conversion means for converting the elastic deformation into an electric signal, a weight that provides a deformation amount equivalent to the deformation amount due to the fluid pressure used for calibrating the fluid pressure sensor is used as the fluid pressure detection means. It is characterized in that it acts on the deformation amount output section of.

The fluid pressure refers to atmospheric pressure, water pressure, etc., and the fluid pressure detection means is, for example, a fluid pressure detection means using an aneroid barometer, a diaphragm provided with concentric waveforms, etc., to facilitate elastic deformation; Fluid pressure detection means set to a predetermined pressure; fluid pressure detection means set to a predetermined pressure on either the outside or the outside of the bellows, apply fluid pressure to the other side, and attach an elastic member such as a spring to bias the other side; Fluid pressure detection means uses a hollow metal flat tube shaped into an arc, spiral, spiral, etc. (Bourdon tube), or other similar means.

The predetermined atmospheric pressure refers to an atmospheric pressure that is necessary and sufficient for measurement, and is usually in a reduced pressure state, but can be set to 1 atm or more if necessary.

Although a conventional differential transformer can be used as the conversion means, the iron core used in the transformer and the empty cup form a vibration system. It is preferable to use the pressure-sensitive conductive member described below because it has disadvantages such as the occurrence of errors due to the pressure-sensitive conductive member described below. The electrical signal to be converted is usually a DC voltage, but is not limited to this, and can also be a signal converted to an alternating voltage, frequency, or the like.

The pressure-sensitive conductive member is made of a rubber-like elastic body made of silicone rubber mixed with and dispersed with carbon particles, for example.
Use of pressure-sensitive conductive rubber whose electrical resistance changes depending on the amount of compression, pressure-sensitive paint that is liquid and forms an elastic body whose electrical resistance changes depending on the amount of compression when applied or gelled. is preferred. In other words, these members have virtually no moving parts (they can be made smaller, and unlike differential transformers, there is no risk of forming or installing a vibration system due to posture errors, and they are inexpensive. It also has advantages such as being advantageous.

The fluid pressure sensor usually has a structure in which a converter is disposed on the displacement side of the fluid pressure detection means, so when a weight is applied, it is not possible to simply suspend the weight from an empty cup.

Therefore, the displacement amount output part of the fluid pressure detection means is provided with an engaging part that engages with a weight, and the weight is slidably attached to a vertically erected guide, and a cantilevered arm is attached from the weight. Applying a load by, for example, providing an engaging portion that extends and engages the arm on the relevant portion of the barometric pressure sensor, or engaging a balance to which the weight is attached to the engaging portion. Can be done.

The weight is determined in advance by calculation or experiment so as to provide a reference displacement with respect to a reference atmospheric pressure. At this time, the load due to the weight acts on the support of the empty bag in the same direction through the empty bag, but since the deformation due to the fluid pressure is expansion and contraction, a force in the opposite direction to that described above acts. Therefore, if it is necessary to take into account the deformation of the support member, it is necessary to take measures such as providing auxiliary equipment to prevent deformation of the support body.

Furthermore, during inspection and calibration work, it is necessary to correct the atmospheric pressure of the working environment. Usually, this is done by increasing or decreasing the weight of the weight according to the atmospheric pressure.

[For production]

Since the weight gives a displacement equivalent to the displacement caused by the atmospheric pressure acting on the atmospheric pressure sensor, inspection and calibration can be easily performed without requiring special equipment such as a pressure regulating chamber.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to an embodiment implemented using an atmospheric pressure sensor with reference to the accompanying drawings.

First, the structure of the atmospheric pressure sensor used in this example will be explained with reference to FIGS. 2 and 3. In the figure, atmospheric pressure sensor 1
In this example, a fluid pressure detection means 2 consisting of an aneroid barometer and a conversion means 6 using a pressure-sensitive conductive rubber sheet 4 are attached to a frame 8.

The fluid pressure detection means 2 consists of an aneroid pressure needle, and is fixed to the frame 8 with a fixing screw 12 via a fixing side boss 10 that is integrally attached to the air cup. A movable boss 14 is integrally attached. The movable boss 14 is partially thinned and provided with a ring-shaped engagement portion 15 for suspending a calibration weight (not shown).

The conversion means 6 for converting changes in atmospheric pressure into electrical signals includes an upper substrate 20 similarly made of a printed wiring board placed on a lower substrate 16 made of a printed wiring board via a spacer 18, and the upper substrate 20 and the lower substrate 16 connected to each other. Pressure-sensitive conductive rubber sheet 4 between
, and a pressure receiving element 22 is attached to the free end side of the upper substrate 20.

The displacement (deformation) of the fluid pressure detection means 2 is transmitted to the pressure sensitive conductive rubber 4 by disposing the movable boss 14 so as to press the pressure receiving element 22 . That is, in this embodiment, the movable boss 14 constitutes the deformation amount output section.

The force (initial pressure) with which the movable boss 14 presses the pressure receiving element 22 is adjusted by an adjustment screw 24 .

That is, the frame 8 has a U-shape, and the side of the lower free end is folded up to form a pedestal 26 into which the adjustment screw 24 is screwed, as shown in FIG.

The adjustment screw 24 is inserted into a through hole 28 provided in the upper arm 8□ of the frame 8, and is screwed into a screw hole 30 provided in the base 26. The pressure force between the movable boss I4 and the pressure receiving element 22 becomes stronger when the adjustment screw 24 is screwed into the pedestal 26, and can be weakened by the return force caused by the elasticity of the frame 8 when it is returned. Note that 32 in the figure is a rib for increasing the longitudinal rigidity of the upper arm 8I.

The electric circuit for detecting the resistance change of the pressure-sensitive conductive rubber 4 consists of an electrode made of printed wiring (not shown), a resistance detection circuit, and an amplification circuit for the output voltage of the circuit. Rubber 4 is placed. 33 in the figure is a variable resistor that adjusts the slope of the atmospheric pressure-output voltage.

Note that the pressure-sensitive conductive rubber 4 acts as an insulator in its free state, and when compressive force is applied, the resistance rapidly decreases, and as the compressive force increases, the rate of decrease in resistance decreases and converges to the final resistance value. It has the property of changing in a curved manner.

Next, the calibration means of this embodiment will be explained with reference to FIGS. 1, 4, and 5. FIG. 1 explains how the barometric pressure sensor I described in FIGS. 2 and 3 is calibrated using a calibration device 35 in which a weight 34 for calibrating the pressure sensor I is suspended directly from the engaging portion 15.

In FIG. 1, the weight 34 is attached to a guide column 38 that is mounted upright on a pedestal 36.

That is, the weight 34 has a hole 40 into which the guide column 38 is inserted, and the engaging portion 1 of the atmospheric pressure sensor 1 is provided at the lower part.
5 is provided with a cantilever-shaped pressurizer 42 that engages with the holder 5. A guide 4 for attaching the barometric pressure sensor 1 to the pedestal 36
4 is provided, and when the atmospheric pressure sensor l to be calibrated is placed here and pressed against the weights 3 and 4 until they stop, the engaging portion 15 engages with the pressurizing element 42.

The manner in which the engaging portion 15 and the pressurizing element 42 engage will be explained with reference to FIG. 4. The presser 42 has a fork-shaped tip 4
5, and has a shape with a slope 46 on the lower surface side. The tip end of the slope 46 is located above the lower surface of the engaging portion 15 provided on the movable boss 14, and when the movable boss 14 is pushed toward the pressurizer 42 (indicated by the arrow in the figure), the engaging portion 15 is The weight 34 is pushed up together with the pressurizer 42, and a load is applied to the atmospheric pressure detection means 2.

Next, a method of calibrating the atmospheric pressure sensor 1 of this embodiment will be explained based on FIG. 5. As shown in the figure, the atmospheric pressure sensor 1 of this embodiment has an output circuit configured such that the output voltage changes linearly with changes in atmospheric pressure. Air pressure sensor 1 of the embodiment
The reference output curve is the output curve shown in C in the figure, but in reality, even those with the same specifications are not constant as shown in output curves A and B. Therefore, after assembling the atmospheric pressure sensor l, we installed the standard atmospheric pressure (
The adjustment screw 24 is adjusted under a pressure of 1 atm (normally 1 atm) to move the output curves A and B in the vertical axis direction and adjust the output to the initial output VO. Therefore, the output curves A and B change to A' and B', respectively. Note that correction for atmospheric pressure above the standard atmospheric pressure can be easily performed by changing the means shown in FIG. 1 so that the atmospheric pressure sensor can be reversely arranged, that is, calibrated with the futherm 8 facing down.

Next, in order to match the output curves A' and B' with the standard output curve C, for example, the atmospheric pressure is set at 500 m, which corresponds to an altitude of 5000 m.
A weight 34 having a weight corresponding to millibar is added to the barometric pressure sensor 1, and the output voltage is made to match the reference output by adjusting the variable resistor 33 (FIG. 2). By doing so, the output curve can be made to match the reference output curve C regardless of variations in the spring constant of the atmospheric pressure detection means 2.

In the case of this embodiment, the diameter of the aneroid barometer used as the atmospheric pressure detection means 1 is 2.4 fins, the weight of the weight corresponding to 500 millibar is 768 gf, and the atmospheric pressure (1
The initial voltage was adjusted to 3.8 V at a pressure of 0.013 mbar), and the output voltage was adjusted to 3.5 V at an atmospheric pressure equivalent to an altitude of 5000 m (500 mbar).

Note that the atmospheric pressure at the location where the calibration work is performed is not necessarily standard atmospheric pressure. Therefore, if the weight of the weight is not corrected, an error will occur in the calibration result. Reference numeral 48 in FIG. 1 is an auxiliary weight for this correction.

The force that deforms the fluid pressure detection means 2 when a predetermined atmospheric pressure acts on the atmospheric pressure sensor 1 used in the embodiment shown in FIG.
If the deflection of the frame 8 is δf, the weight of the weight 34 corresponding to the above atmospheric pressure is W, and the deflection of the frame 8 is δ−1, and the spring constant of the air cup of the atmospheric pressure detection means 2 is KA, then W=F−8 (δ -+δf), and since the amount of deflection of the frame 8 affects the calibration accuracy, it is necessary to manufacture the frame so that the deflection is at least negligible. The atmospheric pressure sensor 1 shown in FIG. 2 used in this embodiment has a structure in which the deflection (δf) due to the upward force is small, but the influence of the deflection (δf) due to the downward force is large. However, in this embodiment, the adjustment screw 24 is screwed in and the upper arm 8. Since the initial output is adjusted by deflecting, the above-mentioned δ- can be made sufficiently small.

FIG. 6 is an explanatory diagram of a main part of the device for canceling the amount of deflection δ-. That is, the upper arm 81 of the atmospheric pressure sensor 1 is the pressurizer 42.
Supporter 5 with a hook to hold it so as not to bend due to
0 is set.

Next, the calibration means according to the second embodiment shown in FIG. 7 will be explained. The second embodiment shows a calibration device 35 that can correct the initial output VO for standard atmospheric pressure also for indoor atmospheric pressure. That is, the inspection/calibration device 35 is mounted on the stand 52
A plate 58, 59 (naturally, it may be used as an upper plate) is suspended from the arms on both sides of a lever 56 which is rotatably supported on a shaft 54 provided in A pressure element 42 similar to that shown in the figure is provided.

The barometric pressure sensor l is supported by a gate-shaped frame 60 that is fixed with a slight gap in the vertical direction. The engagement between the atmospheric pressure sensor 1 and the pressurizing element 42 is the same as that shown in FIG. 1, so the explanation will be omitted.

Next, a calibration method using the inspection/calibration device 35 shown in FIG. 7 will be explained. When the indoor pressure is 1 atm or more, a predetermined correction weight 48 according to the pressure is placed on the plate 58, and the empty bag 2 is adjusted to the standard pressure condition and initialized. Output V. calibrate. If the atmospheric pressure is lower than the standard atmospheric pressure, the weight light is adjusted by compressing the empty cup 2 by placing the weight 48 on the side of the dish 59. Note that if a weight corresponding to the atmospheric pressure at a high altitude is used, calibration for each atmospheric pressure can be performed using the device 35 shown in FIG.

The test/calibration device 35 shown in FIG. 8 represents an embodiment suitable for calibrating a fluid pressure sensor used at a pressure higher than standard pressure. The calibration device 35 has two pulleys 64 attached to a beam 62 protruding from the support 52, and a string 65 suspended from the pulleys 64 connects the plate 58 and the pressurizer 42 to the weight light.
The structure has a suspended base 66. Note that the base 66
A through hole 40 is provided in the hole 40, through which the guide column 38 is inserted so that the presser 42 can be moved up and down horizontally.

The inspection/calibration device 35 shown in FIG. 8 can perform calibration for atmospheric pressure higher than standard atmospheric pressure by placing the weight 34 on a weight plate 58.

Fig. 8 is modified so that a weight placement part is provided at the base 66, and the receiver corrects the standard atmospheric pressure by loading a weight corresponding to the atmospheric pressure at the time of measurement on either the plate 58 or 66. You can also do that.

As mentioned above, barometric pressure sensors used mainly in vehicles and aircraft that are used under atmospheric pressure lower than standard atmospheric pressure, as well as underwater,
It will be appreciated that it may also be used as a calibration means for fluid pressure sensors used at pressures above standard atmospheric pressure, such as in mine shafts.

〔Effect of the invention〕

As explained above, the method for inspecting and calibrating a fluid pressure sensor according to the present invention includes a fluid pressure detecting means that includes an air container whose interior is kept at a predetermined pressure, and whose shape is elastically deformed according to changes in fluid pressure;
When calibrating a barometric pressure sensor comprising a conversion means for converting the elastic deformation into an electric signal, a weight that provides a deformation amount equivalent to the deformation amount due to the fluid pressure used for calibrating the fluid pressure sensor is used as the fluid pressure detection means. Since it is configured to act on the deformation amount output section, the following effects can be obtained. That is, +l) Since equivalent inspection and calibration can be performed without using a pressure regulation chamber to adjust fluid pressure sensors such as barometric pressure sensors and water pressure sensors to the actual pressure, pressure regulation equipment is not required;
The time required for pressure regulation and restoration can be saved.

(2) Electrical wiring for measurement and output adjustment of the fluid pressure sensor installed in the pressure regulating chamber can be performed within normal atmospheric pressure, so work can be done from outside the pressure regulating chamber through gloves, etc. Since there is no need to go in and out of the pressure regulating chamber each time, work efficiency is significantly improved.

(3) With the above, equipment costs and running costs can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is an elevational view of a fluid pressure sensor inspection/calibration device according to one embodiment, FIG. 2 is an elevational view of the air pressure (fluid pressure) sensor shown in FIG. 1, and FIG. 3 is a side view of FIG. 2. Figure 4 is an explanatory diagram of the main parts of Figure 1, and Figure 5 is the atmospheric pressure of the atmospheric pressure sensor shown in Figure 2.
FIG. 6 is a graph showing output voltage characteristics, FIG. 6 is an explanatory diagram of main parts showing a modification of the device shown in FIG. 1, and FIGS. 7 to 8 are diagrams showing another embodiment. DESCRIPTION OF SYMBOLS 1... Air pressure (fluid pressure) sensor, 2... Fluid pressure detection means, 6... Conversion means, 15... Engagement part, 34...
Weight, 35... Inspection/calibration device, 42... Pressure element (
deformation amount output section). atmospheric pressure mbal

Claims (1)

[Claims] When inspecting and calibrating a fluid pressure sensor consisting of an air chamber with a predetermined pressure inside, an air pressure detection means that elastically deforms its shape due to changes in fluid pressure, and a conversion means that converts the elastic deformation into an electrical signal, A method for inspecting and calibrating a fluid pressure sensor, which comprises applying a weight that provides a deformation amount equivalent to the amount of deformation caused by the fluid pressure used for inspecting and calibrating the fluid pressure sensor to the deformation output portion of the atmospheric pressure detection means.