JP7008006B2 - Pressure detector - Google Patents

Description

The present invention relates to a pressure detection device for measuring pressure in, for example, the combustion chamber of an engine.

Conventionally, the internal combustion engine is equipped with a pressure detecting device for detecting the pressure in the combustion chamber in order to detect the combustion state and knocking, improve the fuel consumption rate, and clean the exhaust gas. Based on the detection result by this pressure detection device, a control device called an ECU (Engine Control Unit) controls the operation of the internal combustion engine and the like.

For example, Patent Document 1 discloses a pressure detection device having a detection unit for detecting pressure and a processing unit for performing various processing on an electric signal obtained by detecting the pressure by the detection unit. This pressure detection device is attached to the internal combustion engine so that the detection unit faces the combustion chamber and the processing unit faces the outside.

The detection unit of the pressure detection device disclosed in Patent Document 1 includes a diaphragm head attached to the tip side, a piezoelectric element for detecting the pressure received by the diaphragm head, and a diaphragm head on one surface of the piezoelectric element. It is composed of a front end side housing for accommodating a front end electrode member provided between them and a rear end electrode member arranged on the other surface of the piezoelectric element. The tip-side housing has a cylindrical shape and is made of a metal material.

The processing unit is housed inside the rear end side housing that fits with the rear end side of the front end side housing described above, and is configured to include a circuit board, a conduction member, and the like.

The circuit board performs various processing using an electric circuit on an electric signal due to a weak electric charge output by a piezoelectric element according to the received pressure, and is used inside the front end housing and on the rear end side housing. It is provided straddling the inside. Further, a conduction member for guiding an electric signal output by the piezoelectric element is connected to this circuit board. This conduction member extends from the circuit board toward the piezoelectric element side.

The conductive member that serves as a path for an electric signal has a rod shape and is made of a metal material. The conduction member is provided with a front end side convex portion at the tip thereof and a rear end side convex portion at the rear end thereof. This conduction member is configured to be inserted and arranged inside the front end side housing, and the front end side thereof is configured to abut on the rear end electrode member contact-arranged with the piezoelectric element. The rear end side of the conduction member is connected to the electrode terminals provided on the circuit board side, and serves to guide the electric signal from the piezoelectric element to the circuit board. Then, various processes are applied to the electric signal. On the other hand, the tip electrode member arranged in contact with the piezoelectric element is electrically connected inside the front end side housing and the rear end side housing, and is connected to the GND electrode of the circuit board. ing

JP-A-2017-150976

According to the configuration of the conventional pressure detection device, at the time of assembly, a rod-shaped conductive member extending from the rear end side housing containing the circuit board is inserted inside the front end side housing, and the tip portion thereof is positioned at an appropriate position. It is necessary to fix the front end housing and the rear end housing by abutting and arranging them in contact with a predetermined portion of the electrode member in a held state. However, the insertion of the rod-shaped and elongated conductive member into the tip-side housing has poor workability, and the assemblability and productivity are impaired. In addition, parts such as a spring coil that forms an electric path in direct contact with the electrode member are also attached to the tip of the conduction member, and this coil spring is located near the insertion portion of the tip-side housing or has an internal structure at the time of insertion. The insertion work was hindered by being caught in an object, and at the same time, the members were damaged.

It is an object of the present invention to improve workability, assemblability and productivity in the process of incorporating a conductive member of a piezoelectric detection device into a housing on the distal end side, and to obtain a good and stable product.

At least, a piezoelectric element that detects a change in pressure, a first housing that houses the piezoelectric element, a processing circuit that electrically processes the output signal output by the piezoelectric element, and a first housing that houses the processing circuit. In a pressure detecting device having two housings and a conduction member connected to the processing circuit and inserted and arranged inside the first housing to conduct an output signal of the piezoelectric element to the processing circuit. A tubular guide member for guiding the conduction member to the inside of the first housing is provided at an end portion of the first housing which is an insertion port of the conduction member, and the first housing and the second housing are provided. It is a pressure detector with a fixed body.

The conduction member is covered with a covering member having a stepped shape portion, and the outer peripheral portion of the stepped shape portion of the covering member and the inner surface of the guide member may be arranged in contact with each other. Further, it is preferable that the end portion of the guide member has a flange portion overhanging in a flange shape, and the flange portion and a part of the stepped shape portion of the covering member are arranged in contact with each other. Further, the guide member is preferably made of an insulating member.

According to the present invention, since the conductive member of the piezoelectric detection device can be easily and accurately incorporated into the front end side housing, it is possible to improve the assemblability and productivity, and it is possible to obtain a good and stable product. can.

The schematic block diagram of the pressure detection system which concerns on this invention. Sectional drawing of the pressure detection apparatus which concerns on embodiment of this invention. FIG. 2 is an enlarged cross-sectional view of part A in FIG. Partially exploded perspective view of the pressure detection device according to the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of a pressure detection system according to the present invention.
The pressure detection system 1 supplies power to the pressure detection device 20 for detecting the pressure (combustion pressure) in the combustion chamber C in the internal combustion engine 10 and the pressure detection device 20, and is based on the pressure detected by the pressure detection device 20. It includes a control device 40 that controls the operation of the internal combustion engine 10, and a connection cable 50 that electrically connects the pressure detection device 20 and the control device 40.

Here, the internal combustion engine 10 whose pressure is to be detected includes a cylinder block 11 in which a cylinder is formed, a piston 12 that reciprocates in the cylinder, and a combustion chamber C that is fastened to the cylinder block 11 together with the piston 12 and the like. It has a cylinder head 13 constituting the above. Further, the cylinder head 13 is provided with a communication hole 13a for communicating the combustion chamber C with the outside. A female screw (not shown) is formed inside the communication hole 13a, and by screwing a male screw (not shown) formed on the outer peripheral surface of the pressure detection device 20, pressure is detected with respect to the internal combustion engine 10. The device 20 is attached. A seal member (not shown) is provided on both ends of the communication hole 13a so as to be interposed between the cylinder head 13 and the pressure detection device 20 to maintain the airtightness in the combustion chamber C. There is.

FIG. 2 is a cross-sectional view of the pressure detection device according to the embodiment of the present invention. Further, FIG. 3 is an enlarged sectional view taken along the line A of FIG. In the following description, in FIG. 2, the left side in the figure is referred to as the “tip side” of the pressure detection device 20, and the right side in the figure is referred to as the “rear end side” of the pressure detection device 20.

The pressure detection device 20 has a first housing 21 on the tip end side, and a diaphragm head 22 is attached to the tip end portion thereof. Further, the piezoelectric element 24 is housed inside to form a pressure detection unit. Further, a second housing 26 is provided on the rear end side, and a circuit board 27 is housed inside the second housing 26, and various processes are applied to the electric signal obtained by detecting the pressure by the detection unit. It constitutes a processing unit. Then, in this pressure detection device 20, the tip end portion (diaphragm head 22) of the first housing faces the combustion chamber C (downward in FIG. 1) with respect to the internal combustion engine 10 shown in FIG. 1, and the rear of the second housing. It is mounted so that the ends face outward (upward in FIG. 1).

The first housing 21 is a member having a hollow structure and forming a cylindrical shape as a whole. The first housing 21 is made of a metal material such as stainless steel, which has both conductivity and high acid resistance. The diaphragm head 22 is attached to the tip of the first housing 21 by laser welding, and the second housing 26 is attached to the rear end side of the first housing 21 by fitting. A male screw 21a that meshes with a female screw (not shown) provided on the inner peripheral surface of the communication hole 13a (see FIG. 1) of the cylinder head 13 is formed on a partial outer peripheral surface of the first housing 21. ..

The diaphragm head 22 is a member having a disk shape as a whole. The diaphragm head 22 is made of a metal material such as stainless steel, which has conductivity and high heat resistance and acid resistance. In particular, in this example, the diaphragm head 22 and the first housing 21 are made of the same material. The diaphragm head 22 has a pressure receiving surface 22a that receives pressure by being exposed to the outside (combustion chamber C side) and a recess provided by cutting out the back surface of the pressure receiving surface 22a in an annular shape. As a result, it has a convex portion 22b that protrudes from the central portion of the back surface of the pressure receiving surface 22a toward the rear end side. The diaphragm head 22 is provided so as to close the opening on the tip end side of the first housing 21. Then, laser welding is applied to the boundary portion between the diaphragm head 22 and the first housing 21 over one circumference of the outer peripheral surface.

Inside the first housing 21, a piezoelectric element 24 serving as a pressure detection element is provided. The piezoelectric element 24 is a member having a columnar shape as a whole, and includes a piezoelectric body that exhibits a piezoelectric action of the piezoelectric vertical effect. The piezoelectric vertical effect means that when an external force is applied to a stress application axis in the same direction as the charge generation axis of the piezoelectric body, charge is generated on the surface of the piezoelectric body in the charge generation axis direction. The piezoelectric element 24 is located inside the first housing 21 and on the rear end side of the diaphragm head 22. The piezoelectric element 24 is housed in the first housing 21 so that the central axis direction is the direction of the stress application axis. The front end side surface of the piezoelectric element 24 is in contact with the rear end side surface of the front end electrode member 23a. On the other hand, the surface on the rear end side of the piezoelectric element 24 is in contact with the surface on the front end side of the rear end electrode member 23b.

As the piezoelectric material that can be used in the piezoelectric element 24, a langasite-based crystal (langasite, langateite, langanite, LGTA) having a piezoelectric longitudinal effect and a piezoelectric lateral effect, a crystal, a gallium phosphate, or the like is used. It can be exemplified. In the piezoelectric element 24 of the present embodiment, a Langasite single crystal is used as the piezoelectric body.

The tip electrode member 23a is a member having a columnar shape as a whole. The tip electrode member 23a is made of a metal material such as stainless steel, which has conductivity and high heat resistance. The tip electrode member 23a is configured to be arranged on the tip side of the piezoelectric element 24. The front end surface of the front end electrode member 23a is in contact with the convex portion 22b of the diaphragm head 22 described above, while the rear end side surface of the front end electrode member 23a is in contact with the front end side surface of the piezoelectric element 33. There is. With this configuration, the pressure received by the pressure receiving surface 22a of the diaphragm head 22 is transmitted to the tip electrode member 23a and the piezoelectric element 24 in contact with the tip electrode member 23a via the convex portion 22b. The tip electrode member 23a is connected to the GND electrode of the circuit board in a configuration in which an electrical connection is made inside the housing. Regarding the connection configuration of the GND electrode, the configuration may be such that the housing is used as a connection path and is grounded to the engine head.

The rear end electrode member 23b is a member having a columnar shape as a whole. The rear end electrode member 23b is made of a metal material such as stainless steel, which has conductivity and high heat resistance. The front end surface of the rear end electrode member 23b is in contact with the rear end side surface of the piezoelectric element 24. On the other hand, the surface on the rear end side of the rear end electrode member 23b is in contact with the surface on the tip end side of the insulating ring 25, and the tip portion of the conduction member 28 forming an electric path described later, and a coil spring attached to the tip portion (not shown). ).

The insulating ring 25 is a member forming an annular shape as a whole. The insulating ring 25 is made of a ceramic material such as alumina, which has insulating properties and high heat resistance.

The conduction member 28 is a member having a rod shape as a whole. The conductive member 28 is made of a conductive metal material such as brass. The conduction member 28 is provided with a tip-side convex portion having a diameter smaller than that of the central portion in the central axial direction at the tip thereof, and a coil spring (not shown) is provided at the tip-side convex portion.

The coil spring is a member having a spiral shape as a whole, and expands and contracts in the central axial direction. This coil spring is made of a metal material such as brass, which has conductivity and is higher in conductivity than the first housing 21. The coil spring is arranged so as to pass through the central hole of the insulating ring 25 provided inside the first housing 21 and reach the rear end electrode member 23b.

Reference numeral 26 denotes a second housing that houses a circuit board 27 constituting a processing circuit that electrically processes the output signal output by the piezoelectric element 24, and is fitted to the rear end side of the first housing 21 described above. It is fixed. A connection member 29 to be connected to the connection cable 50 is provided on the rear end side of the second housing.

The second housing 26 is a member having a hollow structure and forming a cylindrical shape as a whole. The second housing 26 is made of a metal material such as stainless steel, which has conductivity and high acid resistance.

The circuit board 27 is a member having a rectangular plate shape as a whole. The circuit board 27 performs various processes using an electric circuit on an electric signal due to a weak electric charge output by the piezoelectric element 24 according to the received pressure, and is composed of a so-called printed wiring board. The circuit board 27 is molded with a resin except for the lead terminals that are connected to the outside, and the substrate surface thereof is protected as a whole. (Since FIG. 2 is a cross-sectional view, it represents a substrate surface.) The entire circuit board 27 is press-fitted and fixed to the inside of the second housing 26. A terminal for electrical connection with the connection member 29 described above is provided on the rear end side of the circuit board 27, and the processing signal of the circuit board 27 is transmitted to the outside by the connection cable 50 connected to the connection member 29. Has been done.

The conduction member 28 is connected and arranged to a lead terminal 27a provided on the tip end side of the circuit board 27. The conduction member 28 is arranged so as to penetrate a through hole provided in the covering member 30 along the central axial direction, and the convex portion on the tip end side of the conduction member 28 projects toward the tip end side of the tip end of the covering member 30. The convex portion on the rear end side protrudes toward the rear end side from the concave portion provided on the rear end side of the covering member 30. The front end side convex portion of the conduction member 28 has a coil spring (not shown), and is configured to come into contact with the rear end electrode member 23b by being inserted into the center hole of the insulating ring 25. ..

Further, the outer peripheral surface of the central portion of the conduction member 23 in the central axial direction is in contact with the inner peripheral surface of the covering member 30. A cover member 32 made of a metal material is provided on the outer peripheral surface of the covering member 30 in order to be connected to the tip electrode member 23a and to form an electric path for the GND electrode. The cover member 32 is configured so as not to come into contact with the coil spring at the tip portion used for signal transmission. Since the cover member 32 is used as an electric path for the GND electrode, it is not necessary to provide the cover member 32, for example, in the case of a configuration in which the housing itself is used as the connection structure for the GND electrode.

The covering member 30 is a member having a cylindrical shape as a whole. The covering member 30 is made of an insulating resin material (PPS, PBT, PPT, etc.). In the covering member 30 of the present embodiment, PPS is used as a resin material having an insulating property. The outer peripheral surface of the covering member 30 is formed to have three different outer diameter portions between the front end side and the rear end side, and the large outer diameter portion 30a is located at the rear end and is located on the circuit board 27. It is a part connected to. The large outer diameter portion 30a may be configured to cover and store the entire circuit board 27. Further, the inner / outer diameter portion 30b is a portion forming a recess in which the lead terminal 27a provided on the circuit board 27 and the conduction member 28 are connected. Further, the small outer diameter portion 30c is a portion where the conduction member 28 is inserted and arranged. With this configuration, a stepped shape portion 30d is formed between different outer diameter portions of the covering member 30.

FIG. 4 is a partially exploded perspective view of the pressure detection device according to the embodiment of the present invention.
The first housing 21 and the second housing 26 described above are fitted to each other via a guide member 31 to form a pressure detection device 20. In the process of assembling the first housing 21 and the second housing 26, first, the guide member 31 is installed in the rear end opening of the first housing 21. The outer diameter of the guide member 31 is smaller than the inner diameter of the first housing 21, and is inserted and arranged inside the first housing 21.

Subsequently, the tip end portion of the conduction member 28 housed inside the second housing 26 and connected to the circuit board 27 is inserted into the guide member 31. At this time, the covering member 30 covering the conduction member 28 is guided by the guide member 31 and can be accurately inserted into the first housing 21.

As the insertion proceeds, the inner and outer diameter portions 30b of the covering member 30 are guided to the inner wall surface of the guide member 31, and at this point, the radial positioning is accurately determined. In this state, the covering member 30 is press-fitted and fixed to the guide member 31. Press-fitting is performed up to a position where the stepped shape portion 30d of the covering member 30 faces the end portion of the first housing 21.

In this way, since the insertion position is accurately maintained by the guide effect of the guide member 31 until the end, the convex portion at the tip of the conduction member 28 is finally inserted into the central hole of the insulating ring 25. Can also be placed accurately and easily.
At this time, the second housing 26 is coupled so as to be fitted into the outer peripheral portion 21a of the end portion of the first housing 21.

The above-mentioned guide member 31 is a cylindrical member, and the guide member 31 is configured to have a flange portion 31a projecting in a flange shape at an end portion. If the guide member 31 is made of an insulating material, unnecessary electrical connection can be prevented. In particular, in one embodiment of the present invention shown in FIG. 3, for example, a cover member 32 or the like is provided in order to obtain a path for the GND electrode by using a component housed inside. In such a configuration, in particular, a cover member 32 or the like is provided. This is the optimum configuration for insulating the first housing 21 from this.

The flange portion 31a of the guide member 31 is not necessarily provided, and can be appropriately omitted depending on the above-mentioned GND electrode connection structure and other configurations.

The pressure detection device according to the present invention can be used when mounted on an engine to measure pressure in a combustion chamber and detect combustion pressure.

1 Pressure detection system 10 Internal combustion engine 11 Cylinder block 12 Piston 13 Cylinder head 13a Communication hole 20 Pressure detection device 21 First housing 21a End outer periphery 22 Diaphragm head 22a Pressure receiving surface 22b Convex part 23a Tip electrode member 23b Rear end electrode member 24 Piezoelectric element 25 Insulation ring 26 Second housing 27 Circuit board 27a Lead terminal 28 Conduction member 29 Connection member 30 Coating member 30a Large outer diameter part 30b Medium outer diameter part 30c Small outer diameter part 30d Stepped shape part 31 Guide member 31a Flange Part 32 Cover member 40 Control device 50 Connection cable

Claims (4)

at least,
Piezoelectric elements that detect changes in pressure and
The first housing for accommodating the piezoelectric element and
A processing circuit that electrically processes the output signal output by the piezoelectric element,
A second housing for accommodating the processing circuit and
In a pressure detecting device having a conduction member connected to the processing circuit and inserted and arranged inside the first housing and conducting an output signal of the piezoelectric element to the processing circuit.
A cylindrical guide member for guiding the conduction member into the inside of the first housing is provided at an end portion of the first housing which is an insertion port of the conduction member , and the first housing and the first housing are provided. 2 A pressure detection device characterized in that a housing is fixed. The present invention is characterized in that the conductive member is covered with a covering member having a stepped shape portion, and the outer peripheral portion of the stepped shape portion of the covering member and the inner surface of the guide member are contact-arranged. The pressure detection device according to 1. 2. The pressure detector according to. The pressure detection device according to claim 1, 2 or 3, wherein the guide member is made of an insulating member.

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