JP2006078379A - Pressure sensor and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure sensor that can be adjusted externally and electrically in a state of unadjusted final product form. <P>SOLUTION: A ceramic pressure-sensitive element 20 in which a strain gauge resistor is deposited on a diaphragm 21, a signal amplifying section 30 composed of an ASIC 31, and a connector 40 in which two power terminals 42, 43 and one output terminal 44 are provided are assembled to the final product form. At adjustment, the output of the output buffer of the ASIC 31 is set to a high-impedance state and the output terminal 44 is switched to an input port, and adjustment data are inputted to the ASIC 31 via it, for writing to a non-volatile register, thus dispensing with each adjustment prior to assembly and enabling overall adjustment, including the influence due to stress that the pressure-sensitive element 20 receives at assembling. The pressure sensor can be manufactured, in advance, regardless of the final output characteristics due to the electrical adjustment being writing of adjustment data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pressure sensor and a manufacturing method thereof, and more particularly to a pressure sensor for detecting a pressure of a refrigerant gas used in an air conditioner system for an automobile and a manufacturing method thereof.

  Since the air conditioner system for automobiles is a relatively large load for the engine that drives the vehicle, it is considered that the engine control is also optimally controlled according to the operating condition of the air conditioner system. In an automotive air conditioner system, one of the information necessary for engine control is the pressure of refrigerant gas on the suction side and discharge side of a compressor directly driven by the engine, and a pressure sensor is used to detect the pressure. Yes.

  Generally, in order to reduce the size and weight of a pressure sensor for an air conditioner for an automobile, it is necessary to electronically detect the pressure of the refrigerant gas. As such a pressure sensor, a sensor that detects a change in pressure by a change in capacitance (for example, see Patent Document 1) and a sensor that detects a change in resistance of a strain gauge resistor (for example, see Patent Document 2). Are known.

  The pressure sensor using the strain gauge resistance is composed of a pressure sensitive element in which a strain gauge resistance is attached to the diaphragm of the pressure sensitive part, and a detection signal corresponding to a change in the resistance value of the gauge resistance connected to the output of the pressure sensitive element. And a signal amplification circuit for amplifying and outputting the signal.

  The use temperature range of the pressure sensor used in the automotive air conditioner system is set to -40 ° C to + 135 ° C. Both the pressure-sensitive element of the pressure sensor and the signal amplifier circuit have a large temperature dependency in which characteristics change depending on the environmental temperature. Therefore, temperature compensation is performed in order to eliminate the temperature dependence within the operating temperature range. For this temperature compensation, an adjustment resistor for temperature compensation is provided in the pressure-sensitive element, and the adjustment resistor is adjusted by trimming with a laser, for example. In addition to the temperature adjustment, the pressure-sensitive element is adjusted for offset and span. Similarly, the signal amplifier circuit also adjusts characteristics such as temperature drift and offset, and various adjustments are made to reduce the measurement error as a whole when assembled by connecting pressure sensitive elements. Yes.

On the other hand, the pressure sensitive element is connected to the signal amplifier circuit and installed in the measurement jig, and trimming of the adjustment resistor in the pressure sensitive element is performed with the signal amplifier circuit connected, so that signal amplification An adjustment method is also known in which adjustment to be performed on the circuit side is completed on the pressure-sensitive element side, and the adjustment process is simplified (for example, see Patent Document 3). Thereafter, the adjusted pressure-sensitive element is removed from the measuring jig and assembled into a final product form in the final assembly process.
JP 2002-202215 A Japanese Utility Model Publication No. 2-89339 Japanese Patent Laid-Open No. 2002-310826 (FIG. 7)

  However, in the conventional pressure sensor using a strain gauge resistor, the resistance value of the adjusting resistor is adjusted by laser trimming. This is because the adjusting resistor is cut with a laser, and this causes mechanical damage. In the long term, there has been a problem that cracks and the like enter from there and become characteristically unstable.

  This invention is made | formed in view of such a point, and it aims at providing the pressure sensor which can be electrically adjusted from the outside in the state of the unadjusted final product form, and its manufacturing method.

  In the present invention, in order to solve the above problem, a pressure sensitive element formed by attaching a strain gauge resistance to the pressure sensitive part, a signal amplifying part for amplifying and outputting an output signal of the pressure sensitive element, and two A pressure sensor having a non-volatile storage means for storing adjustment data for correcting characteristics, wherein the signal amplification section includes: a power supply terminal; and a connector provided with one output terminal. An output buffer connected to the output terminal, the output state of which can be switched to a state of outputting an amplified output signal of the pressure sensitive element or a high impedance state, and an output buffer connected to the output terminal, An input / output for switching the output buffer to the high-impedance state in response to an input of a predetermined digital signal and writing the adjustment data to the storage means And a interface unit, a pressure sensor, characterized in that to be written into the storage means the data generated by the externally input from the output terminal is provided.

  According to such a pressure sensor, it can be electrically adjusted from the outside in the state assembled to the final product form without any adjustment. During the test, the measurement data output from the output terminal of the connector is acquired, and the adjustment data generated based on the measurement data is written to the storage means. At that time, the output buffer is switched to the high impedance state, and the connector The output terminal is used as an input port, and adjustment data is written to the storage means via the input / output interface unit. As described above, measurement and adjustment are performed in the state of the final product using the output terminal of the connector, so that the optimum adjustment point may be shifted due to stress applied to the pressure sensitive element that senses pressure during assembly. In addition, the adjustment is not performed by mechanically damaging it, but by performing it electrically, there is no characteristic change due to the occurrence of cracks at the damaged part, and stable characteristics can be obtained. .

  Further, according to the present invention, a pressure sensitive element formed by attaching a strain gauge resistor to the pressure sensitive part, a signal amplifying part for amplifying and outputting an output signal of the pressure sensitive element, two power supply terminals, And a connector provided with one output terminal, wherein the signal amplifying unit includes a non-volatile storage unit that stores adjustment data for correcting the characteristics. The signal amplification unit and the connector are assembled in a final product form, while maintaining the output state of the signal amplification unit to which the output terminal is connected in a high impedance state, based on the measurement data output from the output terminal A pressure sensor manufacturing method is provided, wherein the adjustment data generated in the step is input from the output terminal and written to the storage means to correct the characteristics of the pressure sensor. That.

  According to such a pressure sensor manufacturing method, the adjustment data is written in the storage means by using the output terminal of the connector that outputs the measurement data, so that the special input for writing the adjustment data is performed. Since it is not necessary to provide a pin and adjustment can be performed in the state of the final product form, the final output characteristic can be obtained easily and accurately.

  The pressure sensor of the present invention is measured and adjusted using one output terminal of the connector in a state assembled in a final product form. Since the measurement and adjustment device is connected by a connector, the connection is reliable, and measurement data at a minute level is not measured by contacting the probe, so that accurate and reliable data measurement can be performed. Since measurement and adjustment are performed in the final product form, adjustment including stress applied to the pressure-sensitive element by assembly is possible, and adjustment can be performed accurately. In addition, the pressure sensor can be adjusted freely by changing the output characteristics specifications, or once adjusted, it can be readjusted later. In addition, since the same product can be prepared regardless of the final output characteristics, there is an advantage that the cost can be reduced due to the mass production effect.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings, taking as an example a case where the embodiment is applied to a pressure sensor that detects the pressure of refrigerant gas in an automotive air conditioner.
FIG. 1 is a cross-sectional view showing the configuration of the pressure sensor.

  The illustrated pressure sensor is used to detect the pressure of refrigerant gas in an automotive air conditioner system, and includes a housing part 10, a pressure sensitive element 20, a signal amplifying part 30, and a connector 40.

  The housing part 10 is connected from a connection part 11 for introducing the refrigerant gas from the piping of the refrigeration cycle of the automotive air conditioner system, an outer cylinder part 12 provided on the opposite side of the connection part 11 from these boundary parts. It is integrally formed by a pin 13 extending in the axial direction in the portion 11 and a cylindrical protrusion 14 extending in the axial direction in the opposite direction to the pin 13 and extending in the axial direction. Yes. The pin 13 is used to push open a valve provided on the pipe side when the pipe of the air conditioner system is connected to the connection part 11 of the housing part 10. A communication hole 15 that communicates with the hollow portion of the cylindrical protrusion 14 is provided beside the pin 13 so that the pressure of the refrigerant gas introduced into the connection portion 11 can be sensed by the pressure sensitive element 20. .

  The pressure-sensitive element 20 is formed by integrally forming a thick cylindrical base material and a diaphragm 21 constituting a pressure-sensitive portion thinly formed at the center so as to close one end surface thereof, using a ceramic material. It is fitted in the space between the outer cylinder part 12 and the cylindrical projection part 14 of the part 10.

  A plurality of strain gauge resistors for measuring the amount of strain of the diaphragm 21 deformed by the introduction of refrigerant gas pressure is attached to the surface of the diaphragm 21 opposite to the cavity of the pressure sensitive element 20. . An O-ring 22 is disposed between the inner wall of the cavity portion of the pressure-sensitive element 20 and the cylindrical protruding portion 14 of the housing portion 10, whereby the cavity of the pressure-sensitive element 20 is connected from the connection portion 11 through the communication hole 15. The refrigerant gas introduced into the section is prevented from leaking to the atmosphere via the connector 40. The O-ring 22 is prevented from falling off by a washer 23 fixed to the tip end portion of the cylindrical protruding portion 14 by caulking.

  The signal amplification unit 30 includes a flexible circuit board and an ASIC (Application Specific Integrated Circuit) 31 that is mounted on the flexible circuit board and processes a signal detected by the strain gauge resistance of the pressure-sensitive element 20.

  The connector 40 is fitted in the outer cylinder part 12 of the housing part 10 so as to receive the outer peripheral part of the pressure-sensitive element 20, and is fixed to the housing part 10 by caulking the tip of the outer cylinder part 12. . The connector 40 has a waterproof structure in which an O-ring 41 is provided around a portion located in the outer cylinder portion 12.

  The connector 40 is provided with two power supply terminals 42 and 43 and one output terminal 44, one end of which is connected to the flexible circuit board of the signal amplifying unit 30. The power terminals 42 and 43 and the output terminal 44 are connected to an air conditioner control circuit (not shown). The power terminals 42 and 43 are supplied with power from the air conditioner control circuit, and the pressure measurement signal output from the ASIC 31 of the signal amplifier 30 is supplied to the air conditioner control circuit via the output terminal 44.

FIG. 2 is a block diagram showing a configuration example of the ASIC.
The strain gauge resistance attached to the pressure sensitive element 20 is composed of four resistors R1, R2, R3, and R4, and constitutes a bridge circuit. The output of the bridge circuit is input to the ASIC 31.

  The ASIC 31 includes an input amplifier 51 for inputting the output of the bridge circuit, a variable gain amplifier 52 whose gain is set by a digital value given from the outside, an amplifier 53 having a gain of 1 or more, and an output buffer 54. The output of the output buffer 54 is connected to the output terminal 44 of the connector 40. The output buffer 54 has an analog switch function inside, and functions as a normal buffer circuit when the analog switch is closed by a signal applied to the output enable terminal, and outputs when the analog switch is open. It has a function of switching the state to a high impedance state.

  The ASIC 31 also includes a serial input / output interface circuit 55 connected to the output of the output buffer 54, and one of the outputs is connected to the output enable terminal of the output buffer 54. Another output of the serial input / output interface circuit 55 is connected to an offset register 56, an offset temperature coefficient register 57, a gain register 58 and a gain temperature coefficient register 59. For the offset register 56, the offset temperature coefficient register 57, the gain register 58, and the gain temperature coefficient register 59, nonvolatile storage means such as an EEPROM (Electronically Erasable and Programmable Read Only Memory) is used.

  The offset register 56 is connected to a digital / analog converter 60, and the output of the digital / analog converter 60 is connected to an adder 61 provided between the input amplifier 51 and the variable gain amplifier 52. The offset temperature coefficient register 57 is connected to the digital / analog converter 62, and the output of the digital / analog converter 62 is connected to the adder 61. The gain register 58 is connected to the gain setting input terminal of the variable gain amplifier 52. The gain temperature coefficient register 59 is connected to a digital / analog converter 63, and the output of the digital / analog converter 63 is connected to an adder 64 provided between the amplifier 53 and the output buffer 54. Yes.

  Here, the pressure sensitive element 20 including the bridge circuit of the strain gauge resistance, the signal amplifying unit including the ASIC 31, and the connector 40 including the power supply terminals 42 and 43 and the output terminal 44 are assembled in the final product form, and this is used for measurement. A measuring and adjusting device for measuring and adjusting is connected to the connector 40 and installed in the jig. The measuring jig can reproduce the installation environment of the pressure sensor according to the specification by varying the pressure and temperature applied to the pressure sensor.

  In order to adjust the pressure sensor, first, the characteristics of the unadjusted pressure sensor when the pressure and temperature are changed by the measurement and adjustment device are measured, and adjustment data is generated based on the measurement data. Next, the measuring and adjusting device inputs a predetermined digital signal to the output terminal 44. When the predetermined digital signal is detected by the serial input / output interface circuit 55, the serial input / output interface circuit 55 gives an output invalid signal to the output enable terminal of the output buffer 54, and changes the output state of the output buffer 54 to a high impedance state. The output terminal 44 is switched to a digital signal input port.

  When receiving the generated adjustment data from the measurement and adjustment device, the serial input / output interface circuit 55 writes and stores the generated adjustment data in the offset register 56, the offset temperature coefficient register 57, the gain register 58, and the gain temperature coefficient register 59. The adjustment data written in the offset register 56 is converted into an analog signal by the digital / analog converter 60, and a value obtained by correcting the offset of the power supply voltage is added to the adder 61. As a result, the output characteristics of the pressure sensor are translated, and the offset voltage is adjusted to the target voltage. Similarly, the adjustment data written in the offset temperature coefficient register 57 is converted into an analog signal by the digital / analog converter 62, and the value obtained by correcting the offset temperature coefficient with respect to the voltage of the power supply is supplied to the adder 61. Add. Thereby, the temperature change of the output of the pressure sensor is corrected. The adjustment data written in the gain register 58 is input to the gain setting input terminal of the variable gain amplifier 52, and the gain of the variable gain amplifier 52 is controlled by a digital signal to adjust the slope of the output characteristic of the pressure sensor. The adjustment data written in the gain temperature coefficient register 59 is converted into an analog signal by the digital / analog converter 63, and the value obtained by correcting the gain temperature coefficient for the output signal of the variable gain amplifier 52 is added. Add to vessel 64. Thereby, the temperature change of the inclination of the output characteristic of the pressure sensor is corrected.

  In this way, adjustment data is input from the output terminal 44 and written to the offset register 56, the offset temperature coefficient register 57, the gain register 58, and the gain temperature coefficient register 59 by the serial input / output interface circuit 55. The characteristics can be corrected.

It is sectional drawing which shows the structure of a pressure sensor. It is a block diagram which shows the structural example of ASIC.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Housing part 11 Connection part 12 Outer cylinder part 13 Pin 14 Cylindrical protrusion 15 Communication hole 20 Pressure sensitive element 21 Diaphragm 22 O-ring 23 Washer 30 Signal amplification part 31 ASIC
40 connector 41 O-ring 42, 43 power supply terminal 44 output terminal 51 input amplifier 52 variable gain amplifier 53 amplifier 54 output buffer 55 serial input / output interface circuit 56 offset register 57 offset temperature coefficient register 58 gain register 59 gain temperature coefficient register 60 digital Analog converter 61 Adder 62 Digital / analog converter 63 Digital / analog converter 64 Adder

Claims (5)

A pressure sensitive element having a strain gauge resistor attached to the pressure sensitive part, a signal amplifying part for amplifying and outputting an output signal of the pressure sensitive element, two power supply terminals and one output terminal are provided. A pressure sensor having a non-volatile storage means for storing adjustment data for correcting the characteristics;
The signal amplifying unit is connected to the output terminal and connected to the output terminal, and an output buffer capable of switching an output state to a state of outputting an amplified output signal of the pressure sensitive element or a high impedance state. An input / output interface unit that switches the output buffer to the high impedance state in response to an input of a predetermined digital signal through the output terminal and writes the adjustment data to the storage unit; The pressure sensor characterized in that the adjustment data generated in (1) is input from the output terminal and written to the storage means.   The pressure sensor according to claim 1, wherein the pressure sensitive element is a ceramic diaphragm or a metal diaphragm. A pressure sensitive element having a strain gauge resistor attached to the pressure sensitive part, a signal amplifying part for amplifying and outputting an output signal of the pressure sensitive element, two power supply terminals and one output terminal are provided. In the method of manufacturing a pressure sensor, the signal amplifying unit includes nonvolatile storage means for storing adjustment data for correcting characteristics.
Assembling the pressure-sensitive element, the signal amplifier, and the connector into a final product form,
While maintaining the output state of the signal amplifier connected to the output terminal in a high impedance state, the adjustment data generated based on the measurement data output from the output terminal is input from the output terminal and Correcting the characteristics of the pressure sensor by writing to the storage means;
A method of manufacturing a pressure sensor, characterized in that it is configured as described above.   4. The method of manufacturing a pressure sensor according to claim 3, wherein the pressure sensitive element is a ceramic or a metal diaphragm. The adjustment data includes offset data for correcting an offset value of the output of the pressure sensor, offset temperature coefficient data for correcting a temperature change of the output of the pressure sensor, gain data for correcting an inclination of an output characteristic of the pressure sensor, 4. The method of manufacturing a pressure sensor according to claim 3, further comprising gain temperature coefficient data for correcting a temperature change in the inclination of the output characteristic of the pressure sensor.

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