JP3873040B2 - Pressure sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a pressure sensor, a laminated piezoelectric material, and a method for manufacturing the same, and more particularly, a pressure sensor that can be suitably used in a high temperature and high pressure environment such as in a cylinder of an internal combustion engine.ToRelated.
[0002]
[Prior art]
2. Description of the Related Art A pressure sensor provided with a piezoelectric element is conventionally known as a sensor for detecting pressure under a high temperature and high pressure environment such as in a cylinder of an internal combustion engine. Piezoelectric elements are compact and have excellent characteristics such as flat and high-speed response characteristics up to 50 kHz and continuous use at high temperatures. Various piezoelectric elements have been proposed as pressure sensing elements. It has been. Examples of pressure sensors including piezoelectric elements include those using quartz, those using gallium phosphate, those using lithium niobate, and those using langasite (see Patent Document 1 and Patent Document 2). ).
[0003]
There are various types of pressure sensors using piezoelectric elements, but there is a method of detecting a charge signal appearing on the surface of a piezoelectric element by applying a pressure (external force) to be detected to the piezoelectric element via a pressure transmission member. Basic method. As an example of the pressure sensor, two piezoelectric elements are arranged so that the electrodes are sandwiched with the same polarity facing each other, and a charge signal is taken out from the electrodes (see Patent Document 2). Transmitted to a piezoelectric sensor formed in a ring shape via a pressure receiving rod, and an output signal of the piezoelectric element is taken out (see Patent Document 3), and a piezoelectric element attached to a spark plug attached to a cylinder head (See Patent Document 4), and those using the horizontal axis effect of a piezoelectric element (see Patent Document 2).
[0004]
[Patent Document 1]
JP-A-5-172680
[Patent Document 2]
JP-A-10-54773
[Patent Document 3]
JP-A-7-77474
[Patent Document 4]
Japanese Patent Laid-Open No. 11-94675
[0005]
[Problems to be solved by the invention]
As described above, a pressure sensor using a piezoelectric element can be used at high temperatures and high pressures, such as when measuring the pressure in a cylinder of an internal combustion engine, and has sufficient durability and stability. Therefore, various requirements such as excellent response characteristics and excellent output sensitivity are required. In addition, when pressure is detected by attaching to an engine of an internal combustion engine, it is possible to withstand mechanical vibrations, and downsizing is required to facilitate attachment to a cylinder head or the like.
In particular, regarding the pressure measurement of the object to be measured, the structure of the piezoelectric element as the sensor part that directly detects the pressure and the signal extraction mechanism are important, and the structure is highly reliable and easy to produce. Is required.
[0006]
  The present invention has been made in order to solve the problems required for pressure sensors using these piezoelectric elements. The object of the present invention is to reduce the pressure in a high temperature environment such as the pressure in a cylinder of an internal combustion engine. A pressure sensor that has large fluctuations, has stable and reliable sensitivity even in environments with large mechanical vibrations, has excellent durability, is easy to assemble and manufacture, and can be downsized.SaIt is something to be offered.
[0007]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention comprises the following arrangement.
  That is, a pressure sensor provided with a diaphragm at the front end portion of the main body formed in a cylindrical shape and capable of detecting the pressure acting through the diaphragm by a sensor unit including a piezoelectric element disposed behind the diaphragm. In the above, as the sensor unit, a plurality of piezoelectric elements are bonded so that their joint surfaces have the same polarity.PressureStacked in the direction of the charge generation axis of the electrocrystal and formed into an integral block body,TheBlock bodyArranged perpendicular to the charge generation axisOne side of stress application axisThe positive electrode or negative electrode is formed on the end surface of the electrode, and the polarity opposite to that of the one end surface is formed on the other end surface.A laminated piezoelectric body in which an electrode to be formed is used, and the diaphragm is formed at the rear part of the diaphragm part integrally with the diaphragm part that receives pressure from the object to be measured, and an end surface of the laminated piezoelectric body Abuts against one end surface by surface contact, It was formed in a block shape with a square end face shapeFormed on a diaphragm head having an electrode portion, electrically insulated from the main body and abutted on the other end face of the multilayer piezoelectric body by surface contact on the rear side of the multilayer piezoelectric body, It is formed in a block shape with a square end face shapeIn addition, an electrode portion to which a lead pin for detecting an electric charge generated in the laminated piezoelectric body is connected is provided.
[0008]
  Also,A first inner body that is in contact with an electrode portion disposed on the rear side of the multilayer piezoelectric body via an insulating member, and a front portion that is in contact with a rear portion of the first inner body; A first inner body, a second inner body for applying a preload to the laminated piezoelectric body via the insulating member and the electrode portion, and a rear portion of the first inner body having a conical concave surface And the front part of the second inner body is formed as a spherical convex surface, so that the axes coincide automatically when preloading is applied, and an eccentric load acts on the laminated piezoelectric body. And the durability of the laminated piezoelectric material can be improved.
[0009]
  Also,A langasite crystal is preferably used as the piezoelectric element constituting the laminated piezoelectric material. Langasite crystals include langasite (La _Three Ga _Five SiO ₁₄ ), Langanite ( La _Three Ga _5.5 Nd _0.5 O ₁₄ ) , Langate ( La _Three Ga _5.5 Ta _0.5 O ₁₄ ) Etc.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail.
FIG. 1 is a cross-sectional view showing the overall configuration of an embodiment of a pressure sensor according to the present invention. The pressure sensor according to the present embodiment is attached to a measured object such as a cylinder head of an internal combustion engine so as to be able to measure the pressure. A piezoelectric element having a horizontal axis effect is formed inside a cylindrical body 10. A multilayer piezoelectric body 30 utilizing the action is mounted, and the charge generated in the multilayer piezoelectric body 30 due to fluctuations in the pressure of the object to be measured is detected by a lead pin 40 provided so as to be inserted through the main body 10. It is what has been.
[0013]
One of the structural features of the pressure sensor according to the present embodiment is that a laminated piezoelectric body 30 in which a plurality of piezoelectric elements utilizing the horizontal axis effect are laminated is used in the sensor portion that detects the pressure of the object to be measured. It is in.
The horizontal axis effect of a piezoelectric element refers to the action of generating an electric charge on the surface of the piezoelectric element in the direction of the charge generation axis when an external force is applied to a stress application axis that is arranged orthogonal to the charge generation axis of the piezoelectric element. . In this embodiment, a langasite crystal is used as the piezoelectric element. However, in a piezoelectric element such as a langasite crystal or quartz crystal, it is known that a charge proportional to an external force is generated on the surface of the piezoelectric element due to the horizontal axis effect. It has been. This horizontal axis effect depends on the ratio of the length in the stress application axis direction to the length (thickness) in the charge generation axis direction, and the thickness in the charge generation axis direction is reduced and the length in the stress application axis direction is increased. By doing so, a larger output can be obtained.
[0014]
In the present embodiment, a laminated piezoelectric body 30 is formed by laminating a plurality of thinly formed piezoelectric elements. In this way, the action of the horizontal axis effect of the piezoelectric element can be used effectively, and by using a plurality of piezoelectric elements, the charge generated in the piezoelectric element can be efficiently collected to increase the sensitivity of the sensor. Can be raised. In addition, by stacking a plurality of piezoelectric elements into an integrated block shape, a large pressure generated in the cylinder portion of the internal combustion engine is applied to the piezoelectric element that is fragile and difficult to apply a large external force. It becomes possible. Since the laminated piezoelectric body 30 is formed by laminating piezoelectric elements formed in a thin plate shape, it looks like a square column with a flat end surface.
[0015]
Details of the structure of the laminated piezoelectric body 30 and the manufacturing method thereof will be described later. Next, the configuration of each part of the pressure sensor of the present embodiment will be described.
As shown in FIG. 1, the attachment side of the main body 10 to the object to be measured is formed to have a slightly smaller diameter than the base body side of the main body 10, and an attachment screw 11 is provided on the outer peripheral surface of the small diameter portion. . As a result, the pressure sensor can be easily fixed by being screwed into a measured object such as a cylinder head of an internal combustion engine.
A diaphragm head 12 is welded and sealed to the front end portion of the main body 10. The diaphragm head 12 is exposed to the measured object so that the pressure of the measured object acts on the diaphragm part 12a, the flange part 12b formed on the peripheral edge of the diaphragm head 12, and the diaphragm part 12a. It consists of the electrode part 14 integrally formed with the diaphragm part 12a in the rear surface.
[0016]
In FIG. 2, the cross section of the structure of the front-end part vicinity of a pressure sensor is expanded and shown. The electrode part 14 is provided so as to extend from the diaphragm part 12 a to the inside of the main body 10, and is formed in a block shape in which the end face shape contacting the end face of the laminated piezoelectric body 30 is a quadrangle. The electrode portion 14 abuts on one (front side) end surface of the multilayer piezoelectric body 30 to apply a pressing force to the multilayer piezoelectric body 30 in accordance with a pressure change on the measured object side. In addition to being formed into an end face shape large enough to press the entire surface, the pressure receiving surface 12c of the diaphragm portion 12a and the pressure transmission surface 12d of the electrode portion 14 are formed in parallel and smooth surfaces. As a result, the pressure received by the diaphragm 12a can be applied to the laminated piezoelectric body 30 evenly.
[0017]
In the present embodiment, since the diaphragm portion 12a, the flange portion 12b, and the electrode portion 14 are formed as a single unit, for example, compared to a method in which the diaphragm is formed separately and attached by welding, The number of points can be reduced, the assembly becomes easy, the problem that the welded part is exposed to pressure and high temperature, causing corrosion, etc. can be solved, and the durability of the pressure sensor can be improved. There are advantages.
Further, by making the diaphragm portion 12a and the electrode portion 14 into an integral structure, the pressure received by the diaphragm portion 12a can be efficiently transmitted to the laminated piezoelectric body 30 via the electrode portion 14. The electrode portion 14 is interposed between the diaphragm portion 12 a and the laminated piezoelectric body 30 and has an action of transmitting the pressure from the measured body to the laminated piezoelectric body 30, and at the same time, can be used as an electrode in contact with the laminated piezoelectric body 30. It is functioning.
[0018]
Reference numeral 16 denotes an electrode portion that comes into contact with the other (rear surface side) end face of the laminated piezoelectric body 30. The tip of the lead pin 40 is fixed to the electrode portion 16, and a charge signal is taken out from the electrode portion 16. Similarly to the end face shape of the laminated piezoelectric body 30, the electrode portion 16 is also formed in a block shape whose end face is a square shape. The electrode portion 16 abuts against the end face of the laminated piezoelectric body 30 to press the laminated piezoelectric body 30 and to take out a charge signal from the laminated piezoelectric body 30.
Reference numeral 18 denotes an insulating ring as an insulating member that electrically insulates the electrode portion 16, and 20 denotes an insulating sleeve having a cylindrical cross section for guiding and supporting the outer periphery of the insulating ring 18, the electrode portion 16, and the laminated piezoelectric body 30. In this embodiment, both the insulating ring 18 and the insulating sleeve 20 are formed of alumina ceramic.
[0019]
The electrode portion 14 provided on the diaphragm head 12 disposed on the front side of the laminated piezoelectric body 30 is electrically connected to the main body 10, and thereby becomes a ground potential. On the other hand, the electrode part 16 arrange | positioned at the back of the laminated piezoelectric material 30 is electrically insulated with respect to the main body 10 as above-mentioned, and can take out an electric charge signal.
The laminated piezoelectric body 30 is used in a state where a certain preload is applied to the stress application axis. The electrode portion 16 also serves to apply a certain preload to the laminated piezoelectric body 30 between the electrode portion 14 and in this embodiment, the end surfaces of the electrode portion 14 and the electrode portion 16 are formed as smooth surfaces. Thus, the preload acts evenly on the entire laminated piezoelectric body 30.
[0020]
As shown in FIG. 1, in order to apply a preload to the laminated piezoelectric body 30, in this embodiment, the first inner body 22 is brought into contact with the rear surface of the insulating ring 18, and the first inner body 22 is in contact with the rear surface. The two inner bodies 24 are in contact with each other. The first inner body 22 is inserted into the main body 10 and is movably provided in the axial direction of the main body 10, whereas the second inner body 24 is a screw 26 provided on the inner peripheral surface of the main body 10. Are screwed together on the rear side to act as preload screws. Reference numeral 27 denotes a screw provided on the outer peripheral surface of the second inner body 24, and is screwed into a screw 26 provided on the inner peripheral surface of the main body 10.
[0021]
In the present embodiment, the rear portion of the first inner body 22 is formed as a conical concave surface 22a, and the front portion of the second inner body 24 is formed as a spherical convex surface 24a. As described above, the contact portion between the first inner body 22 and the second inner body 24 is formed as the conical concave surface 22a and the spherical convex surface 24a, so that the first inner body 22 and the second inner body 24 are in contact with each other. The body 24 abuts linearly, and when the preload is applied for alignment, the shaft centers automatically coincide with each other, so that an uneven load on the first inner body can be prevented. It is possible to suppress an uneven load from acting on the laminated piezoelectric body 30 when the is applied. As a result, it is possible to prevent the laminated piezoelectric body 30 from being chipped, and it is possible to improve the durability of the laminated piezoelectric body 30.
[0022]
The preload applied to the laminated piezoelectric body 30 can be adjusted by adjusting the screwing position of the second inner body 24. The sensitivity and linearity of the laminated piezoelectric body 30 can be adjusted by adjusting the preload applied to the laminated piezoelectric body 30.
The preload adjustment is performed by fixing the first inner body 22 to the main body 10 by laser welding or the like when the second inner body 24 is moved to a predetermined adjustment position (screwed position). After that, the second inner body 24 may be fixed to the main body 10 by laser welding or the like in the same manner as the first inner body 22, or after the first inner body 22 is fixed to the main body 10, You may remove it.
[0023]
The lead pin 40 passes through the inside of the first inner body 22 and the second inner body 24 and is pulled out to the other end side of the main body 10 and connected to the receptacle 28. A connector of a detector is connected to the receptacle 28 so that a charge signal output from the lead pin 40 is detected.
Reference numeral 42 denotes an insulating pipe extrapolated to the lead pin 40. The insulating pipe 42 prevents the lead pin 40 from vibrating and the like to contact the first inner body 22 and the second inner body 24 to be electrically connected to the main body 10 and to prevent electric charge from leaking. Make. In the present embodiment, the insulating pipe 42 is made of alumina ceramic.
[0024]
The pressure sensor formed in this manner is installed by screwing into a cylinder head or the like of an internal combustion engine so that the pressure fluctuation of the measured object acts on the diaphragm portion 12a of the diaphragm head 12, and the electrode portion 14 and the electrode When the pressure fluctuation acts in the stress application axis direction of the laminated piezoelectric body 30 clamped by the portion 16, the charge generated in the laminated piezoelectric body 30 is detected via the lead pin 40, and the pressure of the measured object is detected. Will be.
[0025]
As described above, in the pressure sensor according to the present embodiment, the sensor unit is configured by using the laminated piezoelectric body 30 in which a plurality of piezoelectric elements are stacked using the horizontal axis effect of the piezoelectric elements. Below, the structure of the laminated piezoelectric material 30 and its manufacturing method are demonstrated.
In this embodiment, a langasite crystal is used as the piezoelectric element, the charge generation axis is the X axis (X axis 0 ° cut), the stress application axis is the Y axis (Y axis 0 ° cut), and the optical axis is the Z axis. It is said. Hereinafter, the charge generation axis is referred to as the X axis, the stress application axis is referred to as the Y axis, and the optical axis is referred to as the Z axis.
FIG. 3 is an explanatory view showing the configuration of the electrode arrangement and the like of the laminated piezoelectric body 30 used in the pressure sensor of this embodiment. As described above, the laminated piezoelectric body 30 utilizes the action of generating an electric charge in the X-axis direction when a force is applied in the Y-axis direction of the piezoelectric element. In the case of forming 30, it is necessary to efficiently collect positive charges and negative charges generated on both surfaces of each piezoelectric element in the X-axis direction when an external force is applied in the Y-axis direction.
[0026]
As shown in FIG. 3, when the piezoelectric elements are sequentially laminated in the X-axis direction, the method employed in the present embodiment as a method of forming the laminated piezoelectric body 30 is firstly the X-axis direction of each piezoelectric element. Lamination is performed so that the positive and negative polarities are alternately reversed so that the opposing surfaces of the piezoelectric elements have the same polarity. Thus, the bonding surface of the piezoelectric element becomes a positive pole and a negative pole for each layer. For the positive pole, charges are collected on one pole, for example, the electrode part 14 of the diaphragm head 12, and for the negative pole, charges are collected on the other pole, in this case, the electrode part 16.
[0027]
FIG. 3 shows a state in which a laminated piezoelectric body 30 is formed by laminating four piezoelectric elements 31, 32, 33, and 34. In order to detect the amount of electric charge generated on the surface of each piezoelectric element constituting the laminated piezoelectric body 30, a base film is formed on the bonding surfaces of the piezoelectric elements 31 to 34 by sputtering or vapor deposition, and a conductive material such as solder is used. The piezoelectric elements 31 to 34 are stacked and integrated in the X-axis direction. As a result, the bonding surfaces of the piezoelectric elements 31 to 34 have the same polarity, and a block body of the piezoelectric element in which the conductor layer 36 for taking out electric charges is formed on the bonding surfaces is formed.
[0028]
Next, the electrode film 37 is formed by metallization or the like on both end surfaces in the Y-axis direction of the block body, and the conductor layer 36 and the electrode film 37 formed on the bonding surfaces of the piezoelectric elements 31 to 34 are electrically connected. .
In the state where the electrode films 37 are formed on both end faces of the block body, the conductor layers 36 formed on the bonding surfaces of the piezoelectric elements 31 to 34 are all electrically short-circuited with the electrode film 37. The electrode separation grooves 35 are formed by grinding both end faces in the Y-axis direction into U shapes in cross-sectional shapes in accordance with the joining positions of the piezoelectric elements 31 to 34. The electrode separation groove 35 is ground at each end face for every two piezoelectric elements, so that the position where the electrode separation groove 35 is formed differs from one end face to the other end face by one step.
By forming the electrode separation groove 35 in this way, an electrode 38a that is electrically connected to the positive electrode is formed on the end surface that contacts the electrode portion 14 on the diaphragm head 12 side, and the end surface that contacts the electrode portion 16 on the lead pin 40 side is formed. An electrode 38b is formed which is electrically connected to the negative electrode.
[0029]
In the present embodiment, the end face of the block body is ground in a U shape with a cross-sectional shape to eliminate the electrical short circuit between the conductor layer 36 that becomes the positive electrode and the conductor layer 36 that becomes the negative electrode. The method of separating the negative electrode is not limited to the method of grinding the block body. For example, when the electrode film 37 is formed on the end surface of the block body, the electrode 38a that is electrically connected to the positive electrode is formed on one end surface of the block body. It is also possible to form a pattern and pattern the electrode 38b that is conductive to the negative pole on the other end face of the block body.
However, in the method of grinding the end face of the block body to form the electrode separation groove 35, the conductor layer 36 is partially engraved in accordance with the bonding position of the piezoelectric element, so that the positive electrode and the negative electrode can be surely provided. There is an advantage that it can be electrically cut off.
[0030]
In the embodiment shown in FIG. 3, the positive electrode is electrically connected to the electrode portion 14 and the negative electrode is electrically connected to the electrode portion 16, and the negative charge is detected via the lead pin 40 in the detection portion. It is in a state. The direction in which the laminated piezoelectric body 30 is disposed between the electrode portion 14 and the electrode portion 16 can be arbitrarily selected. Contrary to the arrangement of FIG. It is also possible to arrange so that the plus pole is brought into contact with. In this case, the detection unit detects a positive charge. In either case, the electrode portion 14 is at ground potential.
[0031]
Below, the example which actually produced the laminated piezoelectric material 30 according to the method mentioned above is demonstrated. FIG. 5 is a flowchart showing the manufacturing process of the laminated piezoelectric body 30.
First, a langasite crystal having a Y-axis dimension and an optical axis dimension of 20 mm × 20 mm is ground, and a thicknessing process (step 50) in the X-axis direction is performed. In the present embodiment, the thickness is processed so that the thickness of the X axis is 0.34 mm.
Next, a film forming process (step 51) was performed on the bonding surface of the langasite crystal. In this embodiment, the base film (Ti / Pt / Au) is formed on the bonding surface of the langasite crystal by sputtering.
Next, in order to stack the langasite crystals and bond them together (step 52), a solder film (AuSn) is formed on the base film, and the four langasite crystals are stacked in the X-axis direction with the polar directions aligned. Reflow was performed at 400 ° C. to form a laminate.
[0032]
Next, the laminate was ground and dimensioned in the Y-axis direction (step 53). In the present embodiment, the length in the Y-axis direction is set to 3 mm. As a result, the size of the laminate was 1.4 mm (X axis) × 3.0 mm (Y axis) × 20 mm (optical axis).
Next, metallization (Ti / Au) is performed on the four surfaces in the X-axis direction and the Y-axis direction of the laminate (step 54), electrode films 37 are formed on both end surfaces in the Y-axis direction, and both end surfaces in the X-axis direction are formed. A conductor film 39 is formed on the substrate. The conductor film 39 is formed by metallizing both end faces in the X-axis direction because the conductor films 39 on the upper and lower surfaces of the laminate are formed on both end faces in the Y-axis direction via the corners. This is to make it electrically conductive with 37.
[0033]
Next, electrode separation grooves 35 are formed on both end surfaces in the Y-axis direction of the laminate (step 55). The electrode separation groove 35 is formed by grinding in a U-shaped cross section in accordance with the bonding surface of the langasite crystal. The laminated body is elongated (20 mm) in the Z-axis direction, and the electrode separation grooves 35 can be formed collectively by grinding the laminated body in the Z-axis direction.
Next, the multilayer body is cut at predetermined lengths in the Z-axis direction to form individual block bodies (multilayer piezoelectric bodies) (step 56). In this embodiment, the laminated body was cut so that the length of the block body in the Z-axis direction was 1.4 mm.
Finally, an insulating coating material was applied to the four surfaces excluding the electrodes 38a and 38b on the end surface in the Y-axis direction of the block body formed in the individual piece and the electrode separation groove 35 (step 57), and the laminated piezoelectric body 30 was obtained. .
[0034]
FIG. 4 is a perspective view of the laminated piezoelectric body 30 thus obtained. The laminated piezoelectric body 30 is formed by laminating four piezoelectric elements so that the overall shape is a quadrangular prism. The size of the laminated piezoelectric body 30 is 1.4 mm (X axis) × 3.0 mm (Y axis) × 1.4 mm (Z axis).
The laminated piezoelectric body 30 is joined with a conductor layer formed on the joint surface in the X-axis direction, and a conductor film 39 formed by metallization is formed on the upper and lower surfaces. In addition, in the Y-axis direction, electrode separation grooves 35 are formed on both end faces, and the electrode 38 formed on one end face or the other end face in the Y-axis direction is electrically connected to the positive or negative conductor layer 36. Will be connected to.
[0035]
By mounting the laminated piezoelectric body 30 of this embodiment on a pressure sensor having a diaphragm thickness of 0.1 mm and a diameter of 3.2 mm, a charge output of 20 pC / bar could be obtained. This horizontal-axis effect type pressure sensor can obtain 4 to 5 times the output sensitivity as compared with the pressure sensor using two conventional vertical-axis effect type Langasite crystals, and the S / N ratio. Was also improved 4 to 5 times.
As described above, in the method of manufacturing the laminated piezoelectric body 30 according to the present embodiment, the langasite crystals are laminated and processed in a block shape, so that the processing becomes easy and the laminated body is cut into individual pieces. Thus, since it is a product, there is an advantage that mass production is easy and miniaturization is easy.
[0036]
In the pressure sensor according to the present invention, the electrode portions 14 and 16 are arranged in surface contact with both end faces of the laminated piezoelectric body 30. Accordingly, the heat received by the diaphragm head 12 is quickly transmitted to the internal structure, and the temperature of the entire pressure sensor is reduced due to the arrangement in which the first inner body 22 is in firm contact with the main body 10. Becomes uniform in a short time. This makes it possible to suppress temperature drift and improve pressure detection accuracy.
[0037]
Note that when a langasite crystal is used as the piezoelectric element, the langasite crystal does not have pyroelectricity and does not have a Curie point. There is an advantage that the piezoelectric characteristics can be maintained. Thereby, it can be suitably used for pressure measurement under a high temperature environment such as measuring the pressure in the cylinder of the internal combustion engine.
Of course, the pressure sensor according to the present invention can be used not only for measuring the pressure in the cylinder but also for measuring pressures for various uses such as exhaust pressure and fuel injection pressure.
[0038]
【The invention's effect】
  According to the pressure sensor of the present invention, as described above, it is possible to increase the output by the sensor unit and improve the sensitivity by using a plurality of stacked horizontal axis effect type piezoelectric elements. It can be provided as a highly accurate and highly reliable pressure sensor. In addition, the sensor unit can be downsized, and the pressure sensor can be reduced in diameter and size.
  Further, the multilayer piezoelectric body according to the present invention can be used as a sensitive sensor by using a plurality of piezoelectric elements, and can be suitably used for pressure detection of a cylinder of an internal combustion engine..
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing the overall configuration of an embodiment of a pressure sensor according to the present invention.
FIG. 2 is a cross-sectional view showing a configuration in the vicinity of a front end portion of a pressure sensor.
FIG. 3 is an explanatory diagram showing a configuration of a laminated piezoelectric material.
FIG. 4 is a perspective view of a laminated piezoelectric material.
FIG. 5 is a flowchart showing a manufacturing process of a laminated piezoelectric material.
[Explanation of symbols]
10 Body
11 Screw
12 Diaphragm head
12a Diaphragm part
12c Pressure receiving surface
12d Pressure transmission surface
14, 16 electrode part
18 Insulation ring
20 Insulation sleeve
22 First inner body
22a Concave
24 Second inner body
24a Convex surface
28 Receptacle
30 Multilayer piezoelectric body
31, 32, 33, 34 Piezoelectric element
35 Electrode separation groove
36 Conductor layer
37 Electrode film
38, 38a, 38b electrode
39 Conductor film
40 Lead pin
42 Insulated pipe

Claims (3)

In a pressure sensor provided with a diaphragm at a front end portion of a main body formed in a cylindrical shape and capable of detecting a pressure acting through the diaphragm by a sensor unit including a piezoelectric element disposed behind the diaphragm,
As the sensor unit, a plurality of piezoelectric elements, thereby forming a block body of the integrally stacked on the charge generation axis direction as pressure conductive crystal bonding surface is the same polarity, the charge generating axis of the block body One of the positive and negative electrodes is formed on one end face in the stress application axis direction, which is arranged perpendicular to the electrode, and the other end face is provided with an electrode having a polarity opposite to that of the one end face. The formed laminated piezoelectric material is used,
Said diaphragm, and a diaphragm portion for receiving the pressure from the object to be measured, is formed in the rear of the diaphragm portion integrally with the diaphragm portion, the end face abuts the surface contact with the one end surface of the laminated piezoelectric element, the end face shape It is formed in a diaphragm head provided with an electrode part formed in a block shape to be a square ,
On the rear side of the multilayer piezoelectric body, the end surface is formed in a block shape having a quadrangular shape that is electrically insulated from the main body and abuts against the other end surface of the multilayer piezoelectric body by surface contact. A pressure sensor comprising an electrode portion to which a lead pin for detecting an electric charge generated in a piezoelectric body is connected. A first inner body that is in contact with an electrode portion disposed on the rear side of the multilayer piezoelectric body via an insulating member, and a front portion that is in contact with a rear portion of the first inner body; A second inner body for applying a preload to the laminated piezoelectric body via the first inner body, the insulating member and the electrode portion;
2. The pressure sensor according to claim 1 , wherein a rear portion of the first inner body is formed as a conical concave surface, and a front portion of the second inner body is formed as a spherical convex surface . 3. The pressure sensor according to claim 1 , wherein a langasite crystal is used as the piezoelectric element constituting the laminated piezoelectric body .

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