JPH04118642U - pressure sensor - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the piezoelectric material from being damaged even when abnormally high pressure is applied to a pressure sensor using a piezoelectric material. [Structure] A pressure receiving rod 4 is inserted into the small diameter cylindrical portion 2B of the casing body 2, and the tip side of the small diameter cylindrical portion 2B is caulked at the position of the small diameter shaft portion 4D of the pressure receiving rod 4 to form a reduced diameter portion 2E. . Then, the pressure receiving portion 4E of the pressure receiving rod 4 protruding outward from the reduced diameter portion 2E is separated from the tip surface of the reduced diameter portion 2E by an axial clearance C, thereby regulating displacement of the pressure receiving rod 4 due to excessive combustion pressure. .

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention can be used as a combustion pressure sensor for detecting combustion pressure, etc. of, for example, an automobile engine. The present invention relates to a pressure sensor suitable for use.

0002

[Conventional technology]

In general, a stepped cylindrical case with a large-diameter cylindrical portion at one end and a small-diameter cylindrical portion at the other end. casing, and a pressure sensor that is inserted through the small diameter cylindrical portion of the casing and that is applied from the outside. A pressure-receiving rod that displaces in the axial direction according to the force, and a A pressure detection signal is provided in the large-diameter cylindrical portion of the casing and responds to the displacement of the pressure receiving rod. a piezoelectric body that outputs a signal, and the casing so that the contact portion is in contact with the piezoelectric body. A controller installed inside the large-diameter cylindrical part of the piezoelectric body to derive the pressure detection signal from the piezoelectric body to the outside. A pressure sensor as a combustion pressure sensor consisting of a tact plate is, for example, It is known from Publication No. 2-140429 and the like.

0003 This type of combustion pressure sensor measures the combustion pressure within the engine cylinder. In some cases, a stepped hole is provided in the cylinder head to connect the combustion chamber to the outside of the cylinder head. The combustion pressure sensor is inserted into the stepped hole from the outside of the cylinder head, and the stepped hole is inserted into the stepped hole. Fix the combustion pressure sensor to the cylinder head by placing it in contact with the stepped part of the hole and using a spring, etc. That's what I do.

0004 The air-fuel mixture sucked into the combustion chamber of the engine is then ignited by the spark plug. Then, this air-fuel mixture burns and a very high combustion pressure is generated in the combustion chamber, and this combustion pressure is received by the pressure receiving part of the pressure receiving rod exposed from the tip of the small diameter cylindrical part of the combustion pressure sensor. Press the pressure receiving rod in the axial direction with a pressure that corresponds to the combustion pressure. This allows this combustion pressure is transmitted to the piezoelectric body provided inside the casing of the combustion pressure sensor via the pressure receiving rod. It will be done. At this time, the piezoelectric body is compressed according to the combustion pressure, and an electromotive force corresponding to the combustion pressure is generated. This is used as a pressure detection signal to be sent to an external controller via a contact plate, etc. output to the control unit. The control unit then detects this pressure. Based on the signal, determine whether the combustion pressure is large or small and control the engine ignition timing or It is designed to detect the load status of the engine.

[0005]

[Problem that the idea aims to solve]

By the way, in the above-mentioned conventional technology, the pressure receiving rod is located inside the small diameter cylindrical part of the casing. One end of the pressure receiving rod is disposed within the large diameter cylinder of the casing. Because it comes into contact with the piezoelectric body, the cylinder may be damaged due to knocking, etc. When abnormal high pressure occurs inside the piezoelectric body, this high pressure is transmitted to the piezoelectric body through the pressure receiving rod. , an excessive pressure in the compression direction is applied to the piezoelectric body, and the piezoelectric body exhibits a characteristic line 10 shown in FIG. The problem is that it breaks at the damage point 100A like 0 or deteriorates early. There is.

[0006] This invention was devised in view of the above-mentioned problems of the conventional technology. Prevents excessive pressure from being transmitted to the piezoelectric material even if excessive pressure is applied to the A pressure sensor that can improve durability and extend the lifespan of piezoelectric materials. The purpose is to provide support.

[0007]

[Means to solve the problem]

The feature of the configuration adopted by this invention in order to solve the above-mentioned problems is that the pressure receiving rod is On the other end side, there is a small diameter shaft part located inside the small diameter cylindrical part of the casing, and a smaller diameter shaft part that is larger than the small diameter shaft part. a large-diameter pressure-receiving portion that is formed in a large-diameter diameter and protrudes outward from the tip of the small-diameter cylindrical portion of the casing; and a small diameter shaft portion of the pressure receiving rod is provided on the tip side of the small diameter cylindrical portion of the casing. The diameter is reduced so as to surround it from the outer circumferential side, and the tip surface is axially away from the pressure receiving part of the pressure receiving rod. The reason is that the diameter-reduced portions are formed spaced apart from each other with a clearance in the opposite direction.

[0008]

[Effect]

With the above configuration, when pressure is applied to the pressure receiving part from the outside, the pressure receiving rod Shaft the inside of the small diameter cylindrical part of the casing within the clearance with the tip of the reduced diameter part of the small diameter cylindrical part. This pressure is transmitted to the piezoelectric body by displacing it in the direction, and the piezoelectric body responds to the pressure at this time. Can output pressure detection signal. When excessive pressure is applied to the pressure receiving part, Make sure that the pressure receiving part comes into contact with the tip of the reduced diameter part and the pressure receiving rod is displaced greatly in the axial direction. This can prevent excessive pressure from being applied to the piezoelectric body.

[0009]

【Example】

Below, the case where the pressure sensor according to the embodiment of the present invention is used as a combustion pressure sensor is as follows. This will be explained in detail based on an example and FIGS. 1 to 3.

0010 In the figure, 1 indicates a casing that constitutes the combustion pressure sensor body, and the casing 1 is A stepped cylindrical casing body 2 and one end side of the casing body 2 are covered. It is composed of a cover 3, which will be described later, attached to the casing body 2.

[0011] Here, the casing body 2 is formed into a stepped cylindrical shape from a metal material such as a copper alloy. The large diameter cylindrical part 2A on the upper side, the small diameter cylindrical part 2B on the lower side, and the large diameter cylindrical part 2A and the small diameter cylindrical part 2A on the upper side. It is located between the diameter cylindrical part 2B and gradually tapers downward, and the inner surface is tapered. It is composed of a shoulder portion 2C and a step portion 2D. And the casing book The large diameter cylindrical portion 2A and step portion 2D of the body 2 are formed thickly, and the small diameter portion 2B is formed thinly. has been done. In addition, a pressure receiving rod 4, which will be described later, is inserted inside the lower end side of the small diameter cylindrical portion 2B. It is formed as a reduced diameter part 2E by caulking from the outside in the radial direction while the part is passed through. The upper end side of the reduced diameter part 2E has a tapered bend that applies a spring force in the axial direction to the reduced diameter part 2E. It is on the 2nd floor.

0012 3 is a step fixed to the upper end side of the casing body 2 using means such as laser welding. A cylindrical cover is shown, and the cover 3 has a small diameter protrusion 3A that protrudes upward. A lead wire 12, which will be described later, is inserted into the small diameter protrusion 3A to detect combustion pressure. The signal is output to the outside.

[0013] Reference numeral 4 denotes a pressure receiving rod inserted into the small diameter cylindrical portion 2B of the casing body 2. The pressure receiving rod 4 is made of a metal material such as aluminum and has a stepped cylindrical shape. The upper end side becomes a tapered conical part 4A, and the small diameter cylindrical part of the casing body 2 A shaft portion 4B extending in the axial direction inside 2B, and a tapered portion 4C provided below the shaft portion 4B. A small diameter shaft is formed to have a small diameter and extends in the axial direction inside the reduced diameter part 2E on the lower side of the small diameter cylindrical part 2B. portion 4D, and an outer shape corresponding to the inner diameter of the small diameter cylindrical portion 2B on the lower side of the small diameter shaft portion 4D. It is formed by a large diameter pressure receiving part 4E protruding outward from the tip of the reduced diameter part 2E. has been completed.

[0014] Here, the pressure receiving rod 4 is inserted into the large diameter cylindrical portion 2A within the small diameter cylindrical portion 2B of the casing body 2. It is inserted from the side, and the outer peripheral surface of the conical part 4A is brought into contact with the shoulder part 2C of the casing body 2. In this state, by screwing in a set screw 8 (described later), the conical part 4A and shoulder part 2C are connected. There is a metal seal between the two. Moreover, on the outer peripheral side of the small diameter shaft portion 4D of the pressure receiving rod 4, The reduced diameter portion 2E of the casing body 2 is reduced in diameter by means such as caulking as described above, and the reduced diameter portion 2E is The portion 2E surrounds the outer peripheral side of the small diameter shaft portion 4D. At this time, the casing body The bent portion 2F of No. 2 surrounds the outer circumferential side of the tapered portion 4C of the pressure receiving rod 4, and the diameter is reduced. The tip end surface of the portion 2E is an annular step located between the small diameter shaft portion 4D of the pressure receiving rod 4 and the pressure receiving portion 4E. 4F through a small axial clearance C (see Figure 2). Ru.

[0015] The pressure receiving rod 4 has a pressure receiving portion 4E located at the tip of the reduced diameter portion 2E of the casing body 2. For example, the pressure receiving part 4E projects into the combustion chamber of the engine. By receiving the pressure of This displacement is transmitted as combustion pressure to a piezoelectric body 6, which will be described later.

[0016] 5 is the large diameter of the casing body 2 so as to come into contact with the conical portion 4A of the pressure receiving rod 4. A lower plate provided in the cylindrical portion 2A, the lower plate 5 is made of insulating ceramic. A pressure-receiving rod is formed into a disk shape from a metal material, and is pressed in the axial direction by combustion pressure. The displacement of the electrode 4 is transmitted to the piezoelectric body 6 via a contact plate 9, etc., which will be described later. , to prevent the high temperature inside the combustion chamber of the engine from being transmitted to the piezoelectric body 6. Ru.

[0017] Reference numeral 6 denotes a contact plate located within the large diameter cylindrical portion 2A of the casing body 2 and described later. A piezoelectric body provided on the contact portion 9A of the chip 9 is shown, and the piezoelectric body 6 is, for example, a chip. It is formed as an annular flat plate from a piezoelectric material such as lead tannate, and there are sheets on both end surfaces. An upper electrode and a lower electrode (both not shown) are provided. Here, the pressure The lower electrode of the electric body 6 contacts the contact portion 9A of the contact plate 9, and the upper electrode The poles include an annular upper plate 7 made of a conductive metal material and a stopper to be described later. It is grounded on the casing body 2 side via the same 8. Then, the piezoelectric body 6 When the pressure rod 4 receives combustion pressure in the combustion chamber, this combustion pressure is transferred to the lower plate 5. It is compressed in the axial direction by receiving it through the Electric power is output to the outside as a pressure detection signal of combustion pressure.

[0018] 8 indicates a set screw screwed into the large diameter cylindrical portion 2A of the casing body 2 from above. , the setscrew 8 is formed from a conductive metal material into a substantially cylindrical shape, and has a substantially cylindrical shape on its outer circumferential surface. A screw 8A is provided. Then, the set screw 8 is pressed through the upper plate 7. Press the electric body 6 downward and apply an initial load to the piezoelectric body 6 between it and the pressure receiving rod 4. It is something.

[0019] 9 is a conductive gold plate provided inside the casing body 2 through the set screw 8 etc. The contact plate 9 is made of metal material, and the contact plate 9 has a lower end side. The contact portion 9A is located in a disk shape and contacts the upper electrode of the piezoelectric body 6. and protrudes upward in the axial direction from the inner peripheral side of the contact portion 9A, and the upper end side is a lead. The contact plate is composed of a cylindrical shaft portion 9B which is caulked and fixed to the wire 12. 9 includes a lower insulating tube 10, an upper insulating tube 11, and a lower plate 5, which will be described later. It is insulated from the casing body 2 by. and the contact play 9 connects the pressure detection signal from the piezoelectric body 6 to an external control via a lead wire 12. output to a unit (not shown).

[0020] 10 is a lower insulator provided on the outer circumferential side of the contact portion 9A of the contact plate 9. The lower insulating tube 10 is made of a heat-shrinkable insulating resin material and has a large diameter. It is formed into a cylindrical shape. The lower insulating tube 10 has a lower plate on the inner circumference side. 5, piezoelectric body 6, contact part 9A, etc. are heated by hot air etc. It contracts and surrounds the contact portion 9A and the like.

[0021] Reference numeral 11 denotes an upper insulating tube provided on the outer peripheral side of the shaft portion 9B of the contact plate 9. The upper insulating tube 11 is formed from a heat-shrinkable insulating resin material into a small-diameter cylindrical shape. The upper insulating tube 11 is connected to the outer peripheral side of the shaft portion 9B by the set screw 8 and the casing body. It is designed to be insulated from 2.

[0022] 12 is a lead crimped and fixed to the upper end side of the shaft portion 9B of the contact plate 9. The wire 13 is fitted and fixed to the upper end side of the small diameter protrusion 3A of the cover 3 by means such as caulking. The seal member 13 serves to prevent the lead wire 12 from coming off. In addition, it is designed to prevent rainwater from outside from entering into the cover 3.

[0023] The combustion pressure sensor according to this embodiment has the configuration described above. When installing the sensor, it is attached to the engine cylinder in much the same way as in the prior art. Position the stepped portion 2D of the casing body 2 by bringing it into contact with the stepped hole provided in the pad, Install so that the pressure receiving part 4E of the pressure receiving rod 4 that protrudes downward faces into the combustion chamber. It will be done. The air-fuel mixture sucked into the combustion chamber of the engine is then passed through the spark plug. When ignited, this air-fuel mixture burns, creating very high combustion pressure in the combustion chamber. The combustion pressure is received by the pressure receiving part 4E protruding from the reduced diameter part 2E of the casing body 2. The pressure rod 4 is displaced in the axial direction within the small diameter cylindrical portion 2B according to the combustion pressure.

[0024] Thus, this combustion pressure is transmitted from the pressure receiving rod 4 to the piezoelectric body 6 via the lower plate 5, etc. The piezoelectric body 6 converts the electromotive force corresponding to the combustion pressure into a pressure detection signal. output to an external control unit via the control plate 9, lead wire 12, etc. Ru.

[0025] Therefore, in this embodiment, the pressure receiving rod 4 is placed inside the small diameter cylindrical portion 2B of the casing body 2. With the small-diameter shaft part 4D inserted, the lower end side of the thin-walled small-diameter cylinder part 2B is By caulking from the side, the small diameter shaft portion 4D and tapered portion 4F of the pressure receiving rod 4 are A reduced diameter portion 2E and a tapered bent portion 2F are formed to surround the pressure rod 4 from the side. A small clearance C is formed between the stepped portion 4F and the tip of the reduced diameter portion 2E of the casing body 2. Therefore, when combustion pressure acts on the pressure receiving portion 4E of the pressure receiving rod 4 from the outside, the pressure receiving portion 4E of the pressure receiving rod 4 The rod 4 is displaced in the axial direction within the range of this clearance C, and the combustion pressure at this time is It can be transmitted to the piezoelectric body 6, and the piezoelectric body 6 outputs a pressure detection signal corresponding to the combustion pressure. I can do it.

[0026] Additionally, the engine may knock, causing abnormally high combustion pressure in the combustion chamber. In this case, even if the displacement amount of the pressure receiving rod 4 exceeds the range of the clearance C, Does the annular stepped portion 4F of the pressure receiving rod 4 come into contact with the tip of the reduced diameter portion 2E of the casing body 2? Therefore, the displacement of the pressure receiving rod 4 can be restricted, and excessive compressive force can be applied to the casing. Acting on the piezoelectric body 6 inside the main body 2 can be prevented. And in this case, the annular step 4F strongly collides with the tip of the reduced diameter part 2E, the reduced diameter part 2E of the casing body 2 is elastically deformed in the axial direction by the tapered bent portion 2F, and elastically resists the displacement of the pressure receiving rod 4. It can be sexually buffered, and the pressure detection signal from the piezoelectric body 6 follows the characteristic line 1 shown in FIG. 4, and the piezoelectric body 6 is damaged in the middle as shown by the characteristic line 100 described in the prior art. can be effectively prevented from occurring.

[0027] Therefore, according to this embodiment, the piezoelectric body 6 is not subjected to excessive pressure during knocking, etc. Prevents deterioration and damage, ensuring improved durability and reliability be able to.

[0028] In addition, the small diameter cylindrical portion 2B of the casing body 2 is formed thin, and the inside of this small diameter cylindrical portion 2B is Insert the small diameter shaft part 4D of the pressure receiving rod 4 into the small diameter shaft part 4, and insert the lower end side of the small diameter cylinder part 2B into the small diameter shaft part 4. Since the diameter is reduced on the outer circumferential side of D as the reduced diameter part 2E, the tip of the casing body 2 The stepped hole in the cylinder head can also be formed into a small diameter. This not only improves the strength of the cylinder head, etc., but also improves the strength of the cylinder head. The unevenness near the stepped hole of the door can be minimized as much as possible, stagnation of combustion gas is achieved, and combustion efficiency is improved. This makes it possible to solve problems such as worsening the performance.

[0029] Furthermore, in the combustion pressure sensor according to this embodiment, there is no need for a diaphragm or the like, and the pressure receiving Since the combustion pressure is directly received by the head 4, it is easy to obtain a highly sensitive combustion pressure sensor. Various effects can be achieved, such as the ability to

[0030] Note that in the above embodiment, a combustion pressure sensor that detects the combustion pressure of an engine is taken as an example. However, the present invention is not limited to this, for example, the gas pressure of the reaction vessel, etc. It can also be used as a pressure sensor for detecting.

[0031] Further, in the embodiment described above, the upper plate 7 is formed in an annular shape from a conductive metal material. However, instead of this, for example, a dish plate made of conductive metal material may be used. It is also possible to use rice.

[0032]

[Effect of the idea]

As detailed above, in this invention, the small diameter cylindrical part of the casing is attached to the other end of the pressure receiving rod. a small diameter shaft portion located inside the casing; A large diameter pressure receiving part protrudes outward from the tip of the small diameter cylindrical part, and the small diameter of the casing is The tip side of the cylindrical portion has a diameter reduced so as to surround the small diameter shaft portion of the pressure receiving rod from the outer periphery. , the tip surface is separated from the pressure receiving part of the pressure receiving rod via an axial clearance. Because the reduced diameter part is formed, if high pressure exceeding the normal measurement range is applied to the pressure receiving rod, If the pressure receiving part of the pressure receiving rod is on the tip side of the small diameter cylindrical part of the casing, The displacement of the pressure-receiving rod can be restricted by contacting the rod, and excessive pressure can be applied to the piezoelectric body inside the casing. transmission can be prevented. Therefore, it is possible to reliably prevent damage to the piezoelectric body and increase durability. It is possible to improve the sensitivity and reliability of pressure detection. It has various effects such as:

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a combustion pressure sensor according to an embodiment of the present invention.

FIG. 2 is an enlarged view of main parts in FIG. 1.

FIG. 3 is a characteristic diagram showing the relationship between combustion pressure and a pressure detection signal of a piezoelectric body.

[Explanation of symbols]

1 Casing 2 Casing body 2A Large diameter cylinder part 2B Small diameter cylinder part 2C Shoulder 2D stepped section 2E Reduced diameter part 2F bending section 3 Cover 4 Pressure receiving rod 4B Shaft part 4D Small diameter shaft part 4E Pressure receiving part 6 Piezoelectric body 8 Set screw 9 Contact plate 9A Contact part C Clearance

Claims (1)

[Scope of utility model registration request] Claim 1: A stepped cylindrical casing having a large-diameter cylindrical portion at one end and a small-diameter cylindrical portion at the other end; a pressure-receiving rod that is displaced in the axial direction; a piezoelectric body that is located at one end of the pressure-receiving rod and is provided within the large-diameter cylindrical portion of the casing and outputs a pressure detection signal in accordance with the displacement of the pressure-receiving rod; and a contact. The other end side of the pressure-receiving rod includes a contact plate that is provided in the large-diameter cylindrical portion of the casing so that a part contacts the piezoelectric body, and that derives a pressure detection signal from the piezoelectric body to the outside. is provided with a small-diameter shaft portion located within the small-diameter cylindrical portion of the casing, and a large-diameter pressure receiving portion formed to have a larger diameter than the small-diameter shaft portion and protrude to the outside from the tip of the small-diameter cylindrical portion of the casing, The small-diameter cylindrical portion of the casing has a reduced diameter on the tip side so as to surround the small-diameter shaft portion of the pressure-receiving rod from the outer peripheral side, and the tip surface is spaced apart from the pressure-receiving portion of the pressure-receiving rod via an axial clearance. A pressure sensor characterized by forming a part.