JP2017211321A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability against faults in a sensor.SOLUTION: A diaphragm is formed on a central area of a pressure sensor. A first sensor element 31, an insulating mask 33, and a second sensor element 32 are stacked in this order on a surface of the diaphragm opposite to an opening side into which a fuel flows, resulting in forming a sensor element assembly 30. The first sensor element 31 and the second sensor element 32 are individually configured to be able to output a change in voltage depending on a change in a pressure of the fuel to the outside. This duplication of the sensors achieves improvement of reliability.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a pressure sensor, and more particularly, to an improvement in the reliability of a sensor suitable for detecting rail pressure in a common rail fuel injection control device.

In a so-called common rail fuel injection control device, rail pressure is one of the important factors that affect the quality of fuel injection control. Therefore, its detection requires high stability and reliability. It is well known that various techniques have been proposed and put into practical use not only for themselves but also for detection signal processing methods and the like (see, for example, Patent Document 1).
As a sensor used to detect the rail pressure of the common rail fuel injection control device, a sensor that can output one detection signal is usually used.

JP 2009-168616 A

  However, with only one detection signal, if the output becomes abnormal due to sensor failure or disconnection, it may be difficult to immediately determine whether the detection signal is normal, or a reliable suboptimal measure. Therefore, it is difficult to ensure reliability and safety against failure.

  The present invention has been made in view of the above circumstances, and provides a pressure sensor that further improves the reliability against sensor failure.

In order to achieve the above object of the present invention, a pressure sensor according to the present invention comprises:
A first sensor element, an insulating layer, and a second sensor element are sequentially stacked on a surface opposite to one surface of the diaphragm that receives pressure from the object to be measured, and the first and second sensor elements are sequentially stacked. Using a strain gauge,
The first and second sensor elements are configured to be able to output voltage changes corresponding to the deformation of the diaphragm.

  According to the present invention, a voltage change corresponding to the deformation of the diaphragm can be detected by two sensor elements, and each can be output separately, so that the reliability of the sensor can be greatly improved by duplicating the sensor. It has the effect of being able to do it.

It is a longitudinal cross-sectional view of the pressure sensor module in embodiment of this invention. It is a whole perspective view containing the partial longitudinal cross-section of the pressure sensor in embodiment of this invention. It is the top view which showed typically the pressure sensor element assembly which comprises the pressure sensor in embodiment of this invention. It is an equivalent circuit diagram showing the equivalent circuit of the pressure sensor in the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4.
The members and arrangements described below do not limit the present invention and can be variously modified within the scope of the gist of the present invention.
First, a schematic overall configuration of a pressure sensor according to an embodiment of the present invention will be described with reference to FIG.
The pressure sensor module 50 according to the embodiment of the present invention is used for detection of rail pressure used for fuel injection control or the like in a common rail fuel injection control device.

The pressure sensor 2 in the embodiment of the present invention is housed in a casing 1 for attachment to a common rail (not shown), and constitutes a pressure sensor module 50 together with the casing 1.
The pressure sensor module 50 according to the embodiment of the present invention is roughly divided into a casing 1 and a pressure sensor 2.
The casing 1 includes a screw connection portion 3 formed in a column shape, a plate member 4 attached to the screw connection portion 3 so that the pressure sensor 2 is installed therein, and a PCB circuit board disposed on the plate member 4. 5, a metal housing 6 provided so as to cover the PCB circuit board 5, and a connector housing 7 provided so that the metal housing 6 is fixed thereto. .

The screw connection portion 3 is generally formed in a hollow cylindrical shape, and a screw portion 3a that is screwed into a pressure sensor mounting portion of a common rail (not shown) is formed on the outer peripheral surface thereof.
Fuel from a common rail (not shown) flows into the hollow portion 3b formed inside the screw connection portion 3, and reaches the inside of the pressure sensor 2 described later.

A flange 3c is formed on the top side of the screw connection portion 3, that is, a peripheral portion on the side opposite to a portion screwed to a common rail (not shown), and a plate member 4 described later is provided on the flange 3c. It is supposed to be placed.
Further, the portion where the hollow portion 3b on the top side of the screw connection portion 3 is opened is formed so as to protrude the end portion of the pressure sensor 2.

The plate member 4 formed in a generally disc shape is formed with a sensor housing portion 4a having a hollow cylindrical shape at the center thereof, and the pressure sensor 2 is positioned in the sensor housing portion 4a.
The diameter of the sensor storage portion 4a is set to an appropriate size that does not exceed the outer edge portion of the flange 3c, while maintaining an appropriate distance from the pressure sensor 2.
And as for the plate member 4, the peripheral part of the sensor accommodating part 4a is joined to the flange 3c in the surface at the side of the screw connection part 3.

The pressure sensor 2 has two sensor elements 31 and 32 as will be described later, and can detect the fuel pressure (details will be described later). The screw connection portion 3 is exposed in the opposite direction.
A PCB circuit board 5 is disposed on the surface of the plate member 4 on the side where the vicinity of the top of the pressure sensor 2 is exposed.

The PCB circuit board 5 is provided with a communication hole 5a that allows the top of the pressure sensor 2 to be exposed to the connector housing 7 side at a portion of the plate member 4 that is located in the sensor housing portion 4a. And PCB circuit board 5 can be electrically connected. The PCB circuit board 5 is appropriately provided with, for example, a voltage stabilization circuit, a waveform shaping circuit, and the like necessary for the pressure sensor 2.
The metal housing 6 is formed in a generally lid shape and is integrally attached to a lid portion 7a formed in the connector housing 7, and covers the PCB circuit board 5 together with the lid portion 7a of the connector housing 7. The housing portion 8 which is a space in which the PCB circuit board 5 is housed is fixed to the plate member 4 so as to define it.

The connector housing 7 is a part to which a connection cable (not shown) for electrical connection with an electronic control unit (not shown) for controlling the operation of the vehicle is connected, and is a connection formed in a generally cylindrical shape. The portion 7b and a lid portion 7a formed in a lid shape are roughly divided and configured.
As described above, the lid portion 7a secures the housing portion 8 of the PCB circuit board 5 together with the metal housing 6, and is embedded with a plurality of connection pins 9 made of a conductive member. It has become.

  The electrical connection between the PCB circuit board 5 and the pressure sensor 2 is made through a plurality of bonding wires 10, while the PCB circuit board 5 and the receiving portions 9 a of the connection pins 9 are connected. An S-type spring 11 made of a conductive member is disposed, and the PCB circuit board 5 and the connection pin 9 are electrically connected via the S-type spring 11.

    A connection connector (not shown) provided at an end of a connection cable (not shown) is fitted to the connection portion 7b, and a connection plug (not shown) provided inside the connection connector is connected to a connection pin of the connection portion 7b. By inserting 9, electrical connection with an electronic control unit (not shown) (not shown) is possible.

Next, a more specific configuration of the pressure sensor 2 will be described with reference to FIGS. 2 and 3.
The pressure sensor 2 in the embodiment of the present invention is roughly divided into a diaphragm forming body 20 and a sensor element assembly 30 (see FIG. 2).
Diaphragm forming body 20 is generally formed in a hollow bottomed cylindrical shape, and a diaphragm 21 is formed in a central portion on the opposite side of the opening, and is biased by the pressure of fuel flowing in from the opening. It is possible to move.
A sensor element assembly 30 is provided on the diaphragm 21, that is, on the surface opposite to the opening of the diaphragm forming body 20 as described below.

The sensor element assembly 30 in the embodiment of the present invention is configured to include first and second sensor elements 31 and 32 and an insulating mask 33 (see FIG. 3). In FIG. 3, in order to make the drawing easy to understand and understand, the entire first sensor element 31 is shaded and the second sensor element 32 is outlined.
The first and second sensor elements 31, 32 and the insulating mask 33 are configured by laminating the first sensor element 31, the insulating mask 33, and the second sensor element 32 in this order from the diaphragm 21 side. It has become.
These are not based on the manufacturing technique unique to the present invention, but can be manufactured using a conventionally well-known technique such as vacuum deposition or sputtering in the semiconductor manufacturing technique.
The sensor element assembly 30 is entirely covered with an electrically insulating gel member 12 for protection (see FIG. 1).

  Hereinafter, a specific configuration will be described. First, the first and second sensor elements 31 and 32 basically have the same configuration, and the configuration of the first sensor element 31 will be described below. The description of the second sensor element 32 is replaced with the description of the second sensor element 32. After the reference numerals of the constituent elements of the first sensor element 31, the reference numerals of the corresponding constituent elements of the second sensor element 32 are indicated in parentheses. To do.

  The first sensor element 31 includes so-called strain gauges having first sensor elements first to fourth resistors 41a to 41d (second sensor element first to fourth resistors 42a to 42d). It is. Here, as is well known, the first sensor element first to fourth resistor elements 41a to 41d (second sensor element first to fourth resistor elements 42a to 42d) are, for example, Cr. It is made of a so-called metal film such as a (chrome) -N (nitrogen) thin film.

  The first to fourth resistor elements 41a to 41d for the first sensor element (the first to fourth resistor elements 42a to 42d for the second sensor element) are each a strip-shaped first element that is a basic component. The sensor basic metal film 43A (second sensor basic metal film 43B) has a well-known configuration in which each sensor is folded back alternately to form a so-called zigzag folded shape. Yes.

  FIG. 3 is a plan view of the sensor element assembly 30 as viewed from above on the apex side of the diaphragm 21, that is, the surface side opposite to the surface in contact with the fuel. The fourth resistors 41a to 41d (second sensor element first to fourth resistors 42a to 42d) are arranged as described below in the plan view.

First, the first and second resistor elements 41a and 41b for the first sensor element are arranged at an appropriate interval so that their longitudinal axes are positioned in the left-right direction in FIG. 3 and are parallel to each other. Is arranged.
On the other hand, the first and second resistor elements 41c and 41d for the first sensor element are arranged between the first and second resistor elements 41a and 41b for the first sensor element so that the longitudinal axis directions thereof are the upper and lower parts in FIG. They are arranged in a direction so as to be parallel to each other at an appropriate interval.

  The first sensor element first to fourth resistors 41a to 41d and the second sensor element first to fourth resistors 42a to 42d are the first sensor element first to fourth resistors. The first sensors constituting the first sensor elements first to fourth resistors 41a to 41d are located inside the first sensor elements 41a to 41d, and the first sensor elements first to fourth resistors 42a to 42d are located inside the first sensor elements 41a to 41d. Between the basic metal film 43A, the second sensor basic metal film 43B constituting the first to fourth resistor bodies 42a to 42d for the second sensor element is disposed. Yes.

  The first sensor elements first to fourth resistors 41a to 41d (second sensor element first to fourth resistors 42a to 42d) are connected in series so as to form a so-called bridge circuit, As described below, first sensor first to fourth connection electrodes 45a to 45d (first sensor first to second sensors) that are formed in a rectangular shape via connection wiring 44 as described below. 4 connection electrodes 46a to 46d) are connected and arranged as described below.

  First, the first sensor element first connection electrode 45a (second sensor element first connection electrode 46a) is a first sensor element first resistor 41a (second sensor element first connection electrode 46a). 1 resistor 42a) and a first sensor element third resistor 41c (second element third resistor 42c).

  The first sensor element second connection electrode 45b (second sensor element second connection electrode 46b) is a first sensor element first resistor 41a (second sensor element second resistor). 1 resistor 42a) and a first sensor element fourth resistor 41d (second element fourth resistor 42d).

  Furthermore, the first sensor element third connection electrode 45c (second sensor element third connection electrode 46c) is a first sensor element second resistor 41b (second sensor element second electrode). 2 resistor 42b) and the first sensor element fourth resistor 41d (second element fourth resistor 42d).

  Furthermore, the first sensor element fourth connection electrode 45d (second sensor element fourth connection electrode 46d) is a first sensor element second resistor 41b (second sensor element use). The second resistor 42b) is connected to a connection point between the first sensor element third resistor 41c (second element third resistor 42c).

In the arrangement example shown in FIG. 3, the first to fourth connection electrodes 45 a to 45 d for the first sensor element and the first to fourth connection electrodes 46 a to 46 d for the second sensor are It is arranged as described below.
That is, first, the first to fourth connection terminals 46 a to 46 d for the second sensor element are arranged so as to be positioned at the four corners of the rectangle in the vicinity of the periphery of the first and second sensor elements 31 and 32. It has been established.

  In this example, the first and fourth connection electrodes 46a, 46d for the second sensor element are on the left side of the first and second sensor elements 31, 32 (left side in FIG. 3), and the respective longitudinal axes are The first sensor element first and fourth connection electrodes 45a are disposed so as to be along the horizontal direction of the paper and parallel to each other with an appropriate interval therebetween. 45d are arranged in the same manner.

  Also, the second and third connection electrodes 46b, 46c for the second sensor element are on the right side (the right side in FIG. 3) of the first and second sensor elements 31, 32, and the respective longitudinal axes are in the left-right direction on the page. And the second sensor electrodes for the first sensor element 45b and 45c are provided between the first and second connection electrodes 45b and 45c. It is similarly arranged.

  FIG. 4 shows an electrical equivalent circuit of the first sensor element 31, which will be described below. Since the equivalent circuit is basically the same for the second sensor element 32 as well, in FIG. 4, the second sensor element 32 corresponds after the reference numerals of the components constituting the first sensor element 31. The reference numerals of the components are shown in parentheses, and the description of the equivalent circuit of the first sensor element 31 is replaced with the description of the equivalent circuit of the second sensor element 32.

The electrical equivalent circuit of the first sensor element 31 is a so-called bridge circuit as in the prior art.
The first to fourth connection electrodes 45a to 45d for the first sensor element are used for applying a power supply voltage and outputting a voltage change corresponding to the distortion, and which terminal is used in any manner is arbitrary. For example, a predetermined power supply voltage Vcc is applied from the outside to the first connection electrode 45a for the first sensor element, and the third connection electrode 45c for the first sensor element is connected to the ground (GND). On the other hand, the second sensor electrode second and fourth connection electrodes 45b and 45d for the first sensor element may be used as output terminals for obtaining a voltage output ΔV.

The outputs of the first and second sensor elements 31 and 32 are input to an electronic control unit (not shown) that performs engine fuel injection control and the like for use in fuel injection control and the like.
Since the pressure sensor module 50 according to the embodiment of the present invention can obtain two outputs as described above, it can be used in an electronic control unit (not shown) as described below. Further reliability and stability of operation control such as fuel injection control in the fuel injection control device can be ensured.

  For example, in an electronic control unit (not shown), it is preferable that one of the two outputs obtained by the pressure sensor module 50 is used for fuel injection control and the other output is used for failure detection. . In this case, for example, the failure detection is performed by comparing two outputs, and the change in the output used for the fuel injection control or the like is small or stagnant even though the failure detection output has changed. If the sensor element on the side used for fuel injection control or the like is faulty, the pressure sensor module is provisionally provided with the output of the sensor element for failure detection for fuel injection control or the like. The stability of the operation can be ensured without causing instability of the control operation in the fuel injection control or the like due to 50 failures.

  The present invention can be applied to a pressure sensor for which further improvement in reliability is desired as compared with the prior art.

2 ... Pressure sensor 20 ... Diaphragm forming body 21 ... Diaphragm 30 ... Sensor element assembly 31 ... First sensor element 32 ... Second sensor element

Claims (2)

A first sensor element, an insulating layer, and a second sensor element are sequentially stacked on a surface opposite to one surface of the diaphragm that receives pressure from the object to be measured, and the first and second sensor elements are sequentially stacked. Using a strain gauge,
The first sensor element and the second sensor element are configured to be capable of outputting voltage changes according to deformation of the diaphragm, respectively.   The pressure sensor according to claim 1, wherein the object to be measured is fuel in a common rail fuel injection control device, and is attached to a common rail and used for detection of rail pressure.

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