JPH11132880A - Pressure detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain simple constitution of a low cost by installing a contact member formed of functional material whose electric resistance value changes in accordance with mechanical strain, between two electrodes installed in a housing. SOLUTION: Between a pair of electrodes (a terminal 38 and a disk spring 35) installed in a housing 22 fixed on a fluid pressure equipment, a contact member 50 composed of functional material whose electric resistance value changes in accordance with mechanical strain caused by an external force is installed. Thereby the number of idle revolution of an engine can be continuously controlled in accordance with a load pressure of the fluid pressure equipment, with simple structure of low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure detecting device used for detecting pressure in a fluid pressure device.

[0002]

2. Description of the Related Art In a hydraulic power steering apparatus generally used for automobiles and the like, a hydraulic pump is driven by an engine, and hydraulic oil discharged from the hydraulic pump is supplied to the power steering apparatus to assist in steering. It is supposed to do.

[0003] In this type of hydraulic power steering apparatus, in order to prevent an engine stall caused by an increase in the load pressure of a hydraulic pump due to stationary steering or the like during idling of the engine, the idling of the engine is prevented. An up function is provided, and a pressure switch for detecting an increase in the load pressure of the hydraulic pump during idle rotation of the engine is provided for the idle up.

As such a pressure switch, for example, there is a pressure switch described in Japanese Patent Application Laid-Open No. Hei 9-147708 shown in FIG. In FIG. 7, reference numeral 1 denotes a switch housing. The switch housing 1 is attached to a pressure introducing passage 3 formed in a pump housing 2. In this switch housing 1, a piston 4 to which a load pressure acts via a pressure introducing passage 3 is inserted so as to be movable in the axial direction, and a terminal 5 serving as one electrical contact is provided at the upper part. The terminal 5 is mounted on a holding ring 7 via a resin 6 which is an electrical insulator.

A disk spring 8 is provided between the terminal 5 and the piston 4 and forms another electrical contact which is bent by the pressure of the piston 4 and comes into contact with the terminal 5.
Is provided. The disc spring 8 is sandwiched between the retaining ring 7 and the switch housing 1, and is moved from the switch housing 1 to the pump housing 2.
The body is grounded by conducting.

In the pressure switch having the above structure, when the load pressure of the hydraulic pump increases due to stationary steering or the like during idling of the engine, this pressure acts on the piston 4 and the piston 4 Sliding against the force, the disk spring 8 is elastically deformed and brought into contact with the terminal 5, whereby the pump housing 2 and the terminal 5 are electrically connected, and an electric signal for idling up is controlled by the engine. I send it to the device.

[0007]

However, the above-mentioned conventional pressure switch has only a function as an ON-OFF switch which is turned on when the load pressure of the hydraulic pump becomes higher than a predetermined pressure. It has not been possible to control the engine so that the idle speed changes continuously according to the pressure.

In a power steering apparatus, a pressure sensor may be used to continuously change the idle speed according to the load pressure of a hydraulic pump. However, a pressure sensor is generally more structured than a pressure switch. Are complex and expensive, so pressure switches are commonly used.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems. A housing mounted on a fluid pressure device, a pair of electrodes provided in the housing, In a pressure detection device including a contact member provided between these electrodes, the contact member is formed of a functional material whose electric resistance value changes according to mechanical strain caused by external force. Is what you do.

It is desirable that the contact member is fixed to one of the pair of electrodes. Also, one of the pair of electrodes is provided at the bottom of a storage hole formed at one end of the housing, and is bent by the pressure generated by the fluid pressure device and contacts the other electrode via the contact member. Preferably, it is a spring. Also,
It is preferable that the other electrode is a terminal fixed in the accommodation hole via an electric insulator.

Further, it is preferable that a piston is provided on the fluid pressure device side of the housing and the piston presses the disk spring by a pressure generated by the fluid pressure device. Further, a gap may be provided in a steady state between the contact member and the electrode on the side to which the contact member is not fixed.

Further, the contact member and the electrode on the side to which the contact member is not fixed may contact in a steady state.

[0013]

FIG. 1 shows a first embodiment of the present invention.
4 through FIG. In FIG. 1, reference numeral 10 denotes a pump housing of a hydraulic pump. The pump housing 10 has a pressure introduction passage 11 for introducing a load pressure, and a screw hole 12 formed at an open end of the pressure introduction passage 11. Further, the pressure detecting device 20 of the present invention is screwed and fixed in a liquid-tight manner via a seal ring 21.

The housing 22 of the pressure detecting device 20 has a large-diameter storage hole 23 at one end, and a small-diameter sliding hole 24 communicating with the storage hole 23 at the other end.
On the outer periphery of the other end of the housing 22 on the side where the sliding hole 24 is opened, a screw portion 25 that is screwed into the screw hole 12 of the pump housing 10 is formed. A piston 26 is slidably fitted in the sliding hole 24.
6 has a spherical shape facing the storage hole 23. In the sliding hole 24, a concave portion 30 for accommodating the Teflon ring 27, the O-ring 28, and the locking member 29 is formed on the opening side of the sliding hole 24 in order toward the pressure introducing passage 11 side. The outer periphery of the piston 26 is closely fitted to the inner periphery. The Teflon ring 27, the O-ring 28, and the locking member 29 are restrained from moving in the axial direction by crimping inward the end 31 of the housing 22 on the side of the concave portion 30.

A small diameter portion 32 is formed at the end of the piston 26 on the pressure introduction passage 11 side, and the locking member 29 is engaged with a step portion 33 at the base side of the small diameter portion 32 so that the pressure of the piston 26 is reduced. The movement to the introduction passage 11 side is restricted. A stopper ring 34 is attached to the outer periphery of the small diameter portion 32, and the stopper ring 34 is engaged with the locking member 29. Is restricted from moving to.

A disk spring 35 forming one electrode is mounted on the bottom of the storage hole 23, and the outer periphery of the disk spring 35 is held by a holding ring 36 fitted and stored in the storage hole 23. . As shown in FIG. 2, the disk spring 35 has a shape in which cuts 35A are formed in three places from the outer periphery toward the center of a thin metal plate, and a central portion 35B is supported by a flexible portion 35C formed by the cuts 35A. You are.

As shown in FIG. 2 and FIG.
A contact member 50 is joined to 5B, and the contact member 50 is formed of an electronic functional material having an electric resistance characteristic that changes according to mechanical strain. This electronically functional material has such a characteristic that the electrical resistance is large when no stress is applied, that is, when there is no mechanical strain, and the electrical resistance is reduced as the stress is increased, that is, as the mechanical strain is increased. Things.

Here, as the electronic functional material, for example, those described in Japanese Patent Application No. 8-205320 are preferable. It comprises a first phase made of an insulating base material, an insulating second phase that has a similar or lower elastic modulus than the base material and is continuously dispersed in the base material, What is claimed is: 1. A pressure sensing material comprising conductive and semiconductive third phase particles discontinuously dispersed in two phases, wherein said third phase particles have an interval of not more than 1/2 of said third phase particle diameter. The pressure sensing material is discontinuously dispersed in the second phase, and a pressure corresponding to the external load is detected from a state change of the third phase particles corresponding to the external load of the pressure sensing material. Composite material. The interval between the third phase particles is more preferably 1 μm or less. According to this pressure sensing material,
In a wide temperature range from room temperature to 800 ° C., a wide range of pressure (stress) can be measured with high sensitivity.

The pressure sensing material comprises: 69 wt% of a silicon nitride raw material powder having a particle size of 0.2 μm serving as the first phase raw material; 6 wt% yttrium oxide serving as the second phase raw material; A powder mixture obtained by mixing a 30 wt% silicon carbide raw material powder having a particle size of 30 nm, which is a raw material of the third phase, with a ball mill in a wet system and then drying the mixture is uniaxially press-molded at a pressure of 20 MPa, and then subjected to nitrogen at 1850 ° 1
It can be obtained by performing hot pressing for a time.

Such a pressure sensing material (electronic functional material) is fixed to the central portion 35B of the disk spring 35 as a contact member 50. The disc spring 35 has a structure in which, when a certain force or more is applied to the center portion 35B, the bending portion 35C bends and the center portion 35B is elastically displaced. Have been.

Before the holding ring 36 is assembled into the housing 22, a terminal 38 forming the other electrode is mounted on the inner periphery of the holding ring 36 via a resin 37 which is an electric insulator. The tip of the terminal 38 has a spherical shape, and in the initial stage of contact with the contact member 50, the contact area gradually increases.
The resin 37 has a mounting hole 39 for mounting a connector (not shown).

A connection terminal 40 connected to a connector is fixed to the shaft 38a of the terminal 38. The connection terminal 40 is connected to the connector in the mounting hole 39. This connector is connected to the power supply,
The electrical resistance between the pair of electrodes (disk spring 35 and terminal 38) can be detected.
In FIG. 1, reference numeral 41 denotes a guide groove for guiding the connector in the mounting hole 39 when the connector is mounted.

After the holding ring 36 is stored in the storage hole 23, an O-ring 42 is attached to the outer periphery of the resin 37 at the opening of the storage hole 23, and
By crimping and deforming the end 43 on the third side inward,
The ring 42 is elastically deformed to seal the opening of the storage hole 23. In addition, the holding ring 36 is fixed to the housing 22 via the O-ring 42 by caulking the end 43, and the disc spring 35 is positioned.

1 and 3, the state when no load pressure is applied from the pressure introducing passage 11 is shown on the left side of the axis O, and the state when the load pressure is applied is shown on the right side. When the retaining ring 36 to which the terminal 38 is mounted is incorporated into the housing 22, the terminal 3
The distal end of the disk spring 8 is in contact with a contact member 50 provided at a central portion 35B of the disk spring 35 in a free state via a small gap, and comes into contact with the contact member 50 by a slight elastic deformation of the disk spring 35. Has become.

Next, the operation of the pressure detecting device 20 having the above configuration will be described. Terminal 38 and disc spring 3 when steering device is not steered
5 and the contact member 50 are shown on the left side of the axis O in FIG. At this time, since the load pressure does not rise, the disc spring 35
Is not bent, a gap is secured between the terminal 38 and the contact member 50, and the terminal 38 and the disk spring 35 are not electrically conducted.

However, during idle rotation,
When the steering device is relatively small-steered or when the steering device is steered, the load pressure of the hydraulic pump increases, and this load pressure is introduced from the pressure introduction passage 11 to the piston 2.
6, the disc spring 35 is pressed by the piston 26. Since the load pressure rises before the load force overcomes the spring force of the disc spring 35, the disc spring 35
Is bent and the contact member 50 and the terminal 38 come into contact with each other,
The terminal 38 and the disc spring 35 are electrically connected. Terminal 38 in case of stationary steering
The disk spring 35 and the contact member 50 are shown on the right side of the axis O in FIG.

Here, since the contact member 50 is formed of a functional ceramic having an electric resistance characteristic that changes according to mechanical strain as described above, the terminal 3
An electrical resistance corresponding to the load pressure of the hydraulic pump is detected between the disk spring 8 and the disk spring 35. By transmitting the detected value to the engine control device, it becomes possible to continuously change the idle speed according to the load pressure of the hydraulic pump.

FIG. 4 shows the electrical resistance characteristics of the pressure detecting device 20. In a steady state in which the steering device is in a non-steering state (a state in which the hydraulic pump is not loaded), as shown on the left side of the axis O in FIG.
Is non-contact, the electrical resistance is infinite (region A). Therefore, the leakage current can be reduced to zero in a steady state with no load, and no power is consumed.

In a relatively small steering state (a state in which the hydraulic pump is under a low load), the contact member 50 and the terminal 38 are in the initial stage of contact, and a decrease in the electric resistance due to the distortion of the contact member 50 and a decrease in the contact Due to the decrease in the electric resistance due to the increase in the area, a very sensitive region B can be obtained. In the stationary state (when the hydraulic pump is in a middle to large load state), as shown on the right side of the axis O in FIG. A proportional area C can be obtained.

According to the first embodiment, it is possible to easily control the idle speed in accordance with the load pressure of the hydraulic pump, and to simply provide a pressure detecting device which does not consume wasteful power in a steady state. In addition, the configuration can be inexpensive. Next, a second embodiment will be described with reference to FIGS. In the second embodiment, as shown on the left side of the axis O in FIG. 5, a light initial load is applied between the contact member 50 and the terminal 38 in a no-load state, and the pair of electrodes makes very little contact. The point of contact in area
This is different from the first embodiment. In addition, the right side of the axis O in FIG. 6 shows a state in which a load pressure is applied, as in the first embodiment.

A pressure detector 2 according to the second embodiment
FIG. 6 shows the electrical resistance characteristics of No. 0. In a steady state where the steering device is in a non-steering state (a state in which the hydraulic pump is not loaded) and in a relatively small steering state (a state in which the hydraulic pump is lightly loaded), the contact member 50 and the terminal 38 are initially in contact with each other. In addition, an extremely high sensitivity region D can be obtained by a decrease in electric resistance caused by the distortion of the contact member 50 and a decrease in electric resistance caused by an increase in the contact area. In the stationary state (when the hydraulic pump is in a medium to heavy load state),
Since the contact area is saturated after the middle stage of contact, the contact member 50
, A region E proportional to the load pressure can be obtained.

With the above configuration, when a surge pressure acts on the hydraulic pump in a steady state (no load state), collision between the contact member 50 and the terminal 38 is prevented. Therefore, stable electric resistance characteristics can be obtained for a long period of time. At this time, the contact member 50 and the terminal 3
Since the initial load between them is very small, the distortion of the contact member 50 is also very small, and the electric resistance value is extremely large. Therefore, the leakage current can be minimized,
There is very little wasted power consumption.

In the first and second embodiments, the contact member 50 is provided on the disk spring side, but may be provided on the terminal side. In the first embodiment and the second embodiment, the example in which the pressure detection device according to the present invention is applied to a power steering device of an automobile has been described. However, it is possible to apply the pressure detection device to an automobile and other fluid pressure devices. Needless to say

[0034]

As described above, the pressure detecting device according to the present invention is formed between the two electrodes provided in the housing with a functional material whose electric resistance changes according to mechanical strain. Since the contact member is provided, a simple and inexpensive configuration can be achieved. Further, when applied to a power steering device of an automobile, it becomes possible to continuously control the idle speed in accordance with the load pressure of the hydraulic pump.

Further, if a gap is provided between the contact member and the electrode on which the contact member is not fixed in the steady state, the leakage current in the steady state can be reduced to zero, resulting in wasteful power consumption. Consumption can be eliminated. Further, if the contact member is brought into contact with the electrode to which the contact member is not fixed in a steady state, it is possible to prevent collision between the contact member and the electrode when a surge pressure is applied to the fluid pressure device. And stable electrical resistance characteristics can be obtained for a long period of time. At this time, since the initial load between the contact member and the electrode is very small, the leakage current in the steady state can be minimized, and there is almost no wasteful power consumption.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a pressure detecting device according to a first embodiment of the present invention.

FIG. 2 is a view showing an example of the disc spring shown in FIG. 1;

FIG. 3 is an enlarged view of a main part of FIG. 1;

FIG. 4 is a pressure-electric resistance characteristic diagram of FIG.

FIG. 5 is an enlarged view of a main part showing a second embodiment of the present invention.

FIG. 6 is a pressure-electric resistance characteristic diagram of FIG. 6;

FIG. 7 is a sectional view showing a conventional pressure switch.

[Explanation of symbols]

 22 Housing 23 Storage Hole 24 Sliding Hole 26 Piston 35 Disc Spring 38 Terminal 50 Contact Member

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mitsuru Asai 41-Cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory Co., Ltd. 41, Yokomichi, Toyota Central Research Institute, Inc.

Claims (7)

[Claims] 1. A pressure detecting device comprising: a housing attached to a fluid pressure device; a pair of electrodes provided in the housing; and a contact member provided between the electrodes. Is a pressure detecting device formed of a functional material whose electric resistance value changes according to mechanical strain caused by external force. 2. The pressure detecting device according to claim 1, wherein said contact member is fixed to one of said pair of electrodes. 3. One of the pair of electrodes is provided at the bottom of a storage hole formed at one end of the housing, and is bent by the pressure generated by the fluid pressure device to be connected to the other electrode via the contact member. 3. The pressure detecting device according to claim 2, wherein the pressure detecting device is a contacting disk spring. 4. The pressure detecting device according to claim 3, wherein the other electrode is a terminal fixed in the receiving hole via an electric insulator. 5. The device according to claim 3, further comprising a piston provided on the fluid pressure device side of the housing and configured to press the disc spring by a pressure generated by the fluid pressure device. Pressure detector. 6. The pressure detecting device according to claim 2, wherein a gap is provided in a steady state between the contact member and an electrode on a side to which the contact member is not fixed. apparatus. 7. The pressure detecting device according to claim 2, wherein the contact member and the electrode to which the contact member is not fixed are in contact in a steady state.