JP2000241275A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easy-to-assemble Hall element type pressure sensor excellent in linearity and a stable and rigid fixing mechanism with respect to a Hall element. SOLUTION: The pressure sensor comprises a diaphragm 1 being flexed upon receiving a pressure to be measured, a first magnet 4 secured to the diaphragm, a second magnet 8 of same polarity secured oppositely to the first magnet 4, and a Hall element 9 comprising a Hall IC disposed between first and second magnets. The diaphragm 1 is provided with a central opening and substantially disc-like shape having inner circumferential part secured with the first magnet 4 and outer circumferential part being fitted fixedly in the case 5 of the pressure sensor. Consequently, the diaphragm is held in the case without being supported by other resilient body. Furthermore, the Hall element 9 is held in a recess 14 made in a housing 7 being held in the case 5 while being pressed by a leaf spring 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor for detecting a pressure of a fluid, and more particularly, to a pressure sensor for fixing a magnet on a diaphragm which bends under the pressure of an object to be measured.
The present invention relates to a pressure sensor that converts the displacement of the magnet into electrical characteristics using a Hall element.

[0002]

2. Description of the Related Art JP-A-56-155824 discloses that
A pressure sensor combining a semiconductor Hall element, a magnet, and a diaphragm is disclosed. In this pressure sensor, one of a pair of magnets of the same polarity is fixed to the base and the other is fixed to the center of the diaphragm so that they are opposed to each other, and a Hall element is arranged between these magnets. , The diaphragm is displaced by the pressure of the detection target.

[0003] When the pressure applied to the diaphragm changes, the position of the magnet fixed to the center changes, and as a result, the strength of the magnetic field passing through the Hall element changes and its electrical characteristics change. The electrical characteristics and the amount of change are detected as pressure and the amount of change in the pressure.

In a pressure sensor using a Hall element disclosed in the above-mentioned patent document, a structure using a diaphragm having a bellows-like or wavy cross-sectional shape is shown as a preferred embodiment. However, in the case of a diaphragm having such a wavy cross-sectional shape, it may be difficult to set a highly reproducible relationship between the pressure acting on the diaphragm and the displacement of a magnet fixed to the center thereof. is there.

Japanese Patent Application Laid-Open No. 8-327483 discloses a pressure sensor using the above-mentioned Hall element, which comprises a rigid pressure plate holding a magnet at the center and a flexible member formed around the pressure plate. A structure using a diaphragm is disclosed. Further, in this pressure sensor, springs (coil springs) are arranged above and below the diaphragm.

[0006]

Problems to be Solved by the Invention
No. 483 discloses a pressure sensor in which coil springs are arranged on both upper and lower sides of a diaphragm. As a result, the relationship between the pressure and the amount of deflection of the diaphragm becomes complicated in consideration of the elasticity of each of the diaphragm and the coil spring, and good linearity may not be realized depending on how the respective elasticities are balanced. Therefore, one object of the present invention is to
It is to provide a pressure sensor having good linearity.

In the pressure sensor disclosed in JP-A-8-327483, a Hall element such as a Hall IC housed in a package made of resin or the like is fixed to the inner wall surface of the case by bonding. I have. However, when such a pressure sensor is used as a vehicle component to which a large vibration and a large thermal stress are applied, the strength of the bonding between the Hall element and the case is deteriorated with time, and finally the separation and detachment occur. There is also a possibility of doing it.

Therefore, the present inventor has considered a fixing method as illustrated in FIG.
That is, a method in which the package 21 of the Hall IC is inserted into a concave portion formed in the case, and the terminal 22 is fixed to a conductor portion around a small hole of the printed wiring board 23 fixed inside the case 20 by soldering.

However, when vibration is applied to such a structure, mechanical resonance is performed with the terminal 22 being a cantilever having the soldering point as a fulcrum and the package 21 being a mass held at the tip of the cantilever. Occurs. As a result, the position of the Hall IC varies and the measured value varies. Also, under the condition that temperature change is added to vibration, fatigue occurs at the soldered part due to external force and thermal strain applied from the cantilever,
There is a problem that cracks may occur and breakage may occur.

Accordingly, another object of the present invention is to provide a Hall IC
It is another object of the present invention to provide a stable and robust fixing mechanism for a Hall element such as the above. Still another object of the present invention is to provide a pressure sensor which requires a small number of assembling steps and is easy to assemble.

[0011]

According to the pressure sensor of the present invention, which solves the above-mentioned problems of the prior art, the diaphragm has an opening formed at the center thereof, has a substantially disk shape, and has an inner peripheral portion. Means that the first magnet is fixed, and the outer periphery thereof is clamped and fixed in the case of the pressure sensor, so that the pressure sensor is held in the case without being supported by another elastic body, so that good linearity is obtained. Is realized.
The Hall element formed of a Hall IC or the like in a package is held in the concave portion formed in the housing held in the case while being pressed by the pressing force of the leaf spring, so that the Hall element is stable and robust. A fixing mechanism is realized.

According to a preferred embodiment of the present invention, the leaf spring comprises a peripheral portion held by the case, and a plurality of cantilevers extending radially from the peripheral portion to a central portion, The Hall elements are pressed by the tip portions of these cantilever beams.

According to another preferred embodiment of the present invention,
The second magnet is housed in a bottom of a recess formed in the housing, and the Hall element is held on the second magnet with a shim having a constant thickness interposed.

According to still another preferred embodiment of the present invention, the housing presses the outer peripheral portion of the diaphragm against a step formed inside the case via a bush, thereby forming the diaphragm. An outer peripheral portion is sandwiched and fixed in the case, and has an outer peripheral portion for clamping and fixing the leaf spring between the bush and the bush.

According to still another preferred embodiment of the present invention, the housing is fixed inside the case by swaging an end of the case, and the housing is
In order to supply power to the Hall element and output an electric signal, the Hall element is formed integrally with a connector portion of the housing that protrudes outside the case. Further, after being assembled separately into a portion including the first magnet and a portion including the second magnet, these two portions are finally integrated. Other preferred embodiments of the present invention will be described together with the following examples.

[0016]

FIG. 1 is a sectional view showing the structure of a pressure sensor according to an embodiment of the present invention. In FIG. 1, 1 is a diaphragm, 2 is a magnet holder, 4 is a magnet (first magnet), 5 is a case, 6 is a bush, 7 is a housing, 8 is a magnet (second magnet), 9 is a Hall IC, 10 is a thin plate spring, 11 is a shim, 12 is a circuit board, 13 is a terminal of a Hall IC, 16
Is a connector part of the housing.

The diaphragm 1 has a disk shape with an opening formed in the center, and is made of a metal having high strength and rigidity, such as stainless steel. This is because, in the present embodiment, a hydraulic pressure of about several tens of kgf / cm ² is assumed as the pressure to be measured.

A circular opening is formed at the center of the diaphragm 1, and the body (boss) of the magnet holder 2 is inserted into the opening, and the tip of the body 2 is caulked. Thereby, the magnet holder 2 is firmly fixed to the central portion of the diaphragm 1. A cylindrical magnet 4 is placed inside an opening formed in the head of the magnet holder 2.
The magnet 4 is held inside the magnet holder 2 by fitting. As a material of the magnet holder 2, a non-magnetic metal or the like is used.

The disk-shaped diaphragm 1 is fixed to the inside of the case 5 by its outer peripheral portion being clamped inside the case 5. The diaphragm 1 is joined to a shoulder 5c formed inside a case 5 made of a metal such as low carbon steel by a precision welding method, and hermetically sealed together with fixing is performed. Thereafter, the annular bush 6 is pressed into the case 5. The diaphragm 1 is further pressed and held while being welded to the shoulder 5c by the housing 7 via the bush 6 and the thin plate spring 10.

When the housing 7 is pressed against the outer peripheral portion of the diaphragm 1 by inserting the housing 7 into the case 5 from above, the upper end 5e of the case 5 is swaged to the shoulder of the housing 7. This is performed when the connection between the case 5 and the housing 7 is completed.

A cylindrical magnet 8 is held inside a small-diameter circular recess 14 formed at the back of the center of the housing 7, and a Hall IC 9 containing a package is held inside the groove via a shim 11. You. The distance between the magnet 8 and the Hall IC is kept constant by the thickness of the shim 11.
Then, the second magnet 8 and the Hall IC 9 are held inside the housing 7 by the Hall IC 9 being pressed toward the inside of the housing 7 by the leaf spring 10. The outer peripheral portion of the leaf spring 10 is sandwiched between the outer peripheral portion of the housing 7 and the bush 6.

As shown in the plan view of FIG. 2, the leaf spring 10 has an annular peripheral portion 10e and a peripheral portion 10e.
And four plate-like cantilevers 10a, 10b, 10c, 10d extending radially from
Hall ICs 9 indicated by dotted lines are pressed into the recesses by the tip portions of these cantilever beams 10a to 10d. As shown in the partially enlarged view of FIG. 3, the distal ends of the cantilevers 10a to 10d are formed with a smooth curved portion having a large radius of curvature depending on the direction in which the mold is removed.

As described above, by forming a curved portion at the tip of the cantilever which is brought into contact with the surface of the resin package of the Hall IC 9, the resin can be formed by the tip of the cantilever under a vibration environment. Is designed so that it is not removed. Instead of curving the tip of each cantilever, a flat portion may be formed at the tip as shown in the partial enlarged view of FIG. Can be avoided.

Referring again to FIG. 1, inside the housing 7, a printed wiring board 12 on which a surge protection circuit for supplying power to the Hall IC 9 and the like are formed is held. The tip of the terminal 13 of the Hall IC 9 is passed through a small hole formed in the printed wiring board 12, and the tip of the terminal 13 is fixed to a metal layer formed around the small hole by soldering. .

The terminals 13 of the Hall IC 9 are connected to pins 16b and 16c of a connector portion 16 of the housing 7 formed integrally with the housing 7 via a printed wiring board 12. A cable is connected to the connector portion 16 of the housing via a connector (not shown), and the detected pressure converted into electrical characteristics is transferred via the cable.

The inside of the case 5 is partitioned by the diaphragm 1 into a chamber 5a which is connected to a pressure source to be detected through a pressure introducing pipe 5d and a chamber 5b which is maintained at atmospheric pressure. For this reason, sufficient airtight sealing is performed between the diaphragm 1 and the magnet holder 2 by a precision welding method using a laser.

As described above, first, the diaphragm 1 including the magnet 4 and the case 5 and the housing 7 including the magnet 8 and the Hall IC 9 are separately assembled into two parts. Finally, the housing 7 is inserted into the case 5 with the bush 6 interposed therebetween.
Are crimped on the shoulder of the housing 7 so that these two parts are integrated.

At the time of the final assembly, a Hall IC
The position where the magnetic flux density of the coil 9 becomes zero is adjusted by the thickness of the shim 11 interposed between the Hall IC 9 and the magnet 8, and the electrical characteristics are measured immediately before the end 5e of the case 5 is swaged. If the measurement result of the electric characteristics is good, the end portion 5e is caulked. If the measurement result of the electric characteristics is bad, the position of the Hall IC 9 is adjusted by changing the shim to a shim having a different thickness, and then the measurement of the electric characteristics immediately before the caulking is repeated again.

[0029]

As described above in detail, in the pressure sensor of the present invention, since the diaphragm has a substantially disk shape, the pressure sensor is compared with the conventional bellows shape and the diaphragm structure formed by combination with a coil spring. In addition, there is an advantage that the relationship between the pressure and the amount of deflection is simplified, and a pressure sensor with good linearity and reproducibility can be realized.

Further, in the pressure sensor of the present invention, the Hall element formed of a Hall IC or the like in a package is held in the recess while being pressed by a leaf spring pressing force against the recess formed in the housing held in the case. With such a configuration, it does not move even under a vibration environment unique to a vehicle or the like, and the accuracy of pressure detection is ensured. Further, unlike the case of joining with an adhesive, no thermal stress is generated in the joint, and the joint is not cracked or broken due to this, and high reliability and long life can be realized.

According to a preferred embodiment of the present invention, first, a case having a diaphragm and one magnet and a housing having a Hall element and the other magnet are separately assembled, and thereafter, both are assembled. Since the final assembly is completed by being connected, there are advantages that the number of assembling steps is reduced and the assembling work is facilitated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a pressure sensor according to an embodiment of the present invention.

FIG. 2 is a plan view showing a configuration of a leaf spring 10 of FIG.

FIG. 3 is a partially enlarged view showing a shape of a distal end portion of the leaf spring 10;

FIG. 4 is a partially enlarged view showing another example of the shape of the distal end portion of the leaf spring 10. FIG.

FIG. 5 is a partially enlarged view showing an example of a fixing method of a Hall element not according to the present invention.

[Explanation of symbols]

 1 Diaphragm 2 Magnet holder 4,8 Magnet 5 Case 6 Bush 7 Housing 9 Hall IC 10 Leaf spring 10a-10d Cantilever 10e Circular peripheral part 11 Shim 16 Housing connector

Claims (10)

[Claims] A first diaphragm fixed to the diaphragm, a second magnet fixed opposite to the first magnet, the first magnet fixed to the diaphragm, the first magnet fixed to the diaphragm; A pressure sensor having a Hall element comprising a packaged Hall IC and the like disposed between the second magnets, wherein the diaphragm has an opening at the center thereof and has a substantially disk shape; The first magnet is fixed to the inner peripheral portion, and the outer peripheral portion is held and fixed in the case without being supported by another elastic body by being clamped and fixed in the case of the pressure sensor. A pressure sensor, wherein the Hall element is held while being pressed by a pressing force of a leaf spring in a recess formed in a housing held in the case. 2. The cantilever according to claim 1, wherein the leaf spring comprises a peripheral portion held by the case, and a plurality of cantilevers extending radially from the peripheral portion to a central portion. A pressure sensor for pressing the Hall element by a tip portion of the pressure sensor. 3. The device according to claim 1, wherein the second magnet is accommodated in a bottom of a recess formed in the housing, and the hole is formed on the second magnet with a shim having a constant thickness interposed therebetween. A pressure sensor characterized by holding an element. 4. The housing according to claim 1, wherein the housing presses an outer peripheral portion of the diaphragm to a step formed inside the case via a bush, thereby pressing an outer peripheral portion of the diaphragm to the case. A pressure sensor having an outer peripheral portion that is sandwiched and fixed inside and the leaf spring is sandwiched and fixed between the bush and the bush. 5. The pressure sensor according to claim 1, wherein the housing is fixed inside the case by caulking an end of the case. 6. The housing according to claim 1, wherein the housing is formed integrally with a connector portion of the housing protruding outside the case to supply power to the Hall element and output an electric signal. Pressure sensor characterized in that: 7. The method according to claim 1, wherein the parts including the first magnet and the parts including the second magnet are assembled separately and then these two parts are finally integrated. A pressure sensor having a structure. 8. The method according to claim 1, wherein a position where the magnetic flux density of the Hall element becomes zero is adjusted by a thickness of a shim interposed between the Hall element and the second magnet. Pressure sensor. 9. The method according to claim 3, wherein the position where the magnetic flux density of the Hall element becomes zero is adjusted by the thickness of a shim interposed between the Hall element and the second magnet. Pressure sensor. 10. The assembling method according to claim 9, wherein the assembling is performed such that the electrical characteristics are measured immediately before caulking the end of the case, and if the result is good, the caulking is performed. The pressure sensor according to claim 1, wherein after the position of the Hall element is adjusted based on the thickness of the shim, the measurement of the electrical characteristics immediately before the caulking is repeated.