JP5044423B2 - Pressure detection device - Google Patents

Description

  The present invention relates to a pressure detection device, and more particularly to a pressure detection device that receives an input pressure on a pressure receiving member and outputs a pressure detection signal corresponding to the state change.

  As a pressure detection device that detects the pressure of a fluid such as gas or liquid, a pressure detection device that receives a pressure of a fluid on a pressure receiving member to change the state of the pressure receiving member and outputs a pressure detection signal corresponding to the change is known. It has been.

  As a conventional pressure detection device of this type, for example, as a mechanical vibration type that detects the intake air pressure of an internal combustion engine for a vehicle, a vibrator and a detector are attached to a vibrating body with one end opening that receives air pressure, and vibration is generated. Some devices obtain electrical pressure by detecting the resonance frequency of a vibrating body that changes due to the pressure difference between the inside and outside of the body. In this device, a double system in which a vibrator and a detector are attached to the vibrating body in pairs. By adopting the sensor configuration, the reliability of the electrical signal detection system having lower reliability than that of the vibrating body is increased (for example, see Patent Document 1).

Of the two sensors with different sensitivity characteristics related to photoelectric conversion, a low-sensitivity sensor is used for a wide illuminance region and a high-sensitivity sensor is used for a low illuminance region. There is also known an electronic imaging device that achieves both a wide dynamic range and high resolution (see, for example, Patent Document 2).
JP 05-34223 A JP 08-340486 A

  However, in the conventional pressure detection device having the above-described double sensor configuration, the linearity of the pressure sensitivity is reduced in the pressure region on the low pressure side or the high pressure side due to the configuration of the vibrating body. Yields are low because the detection errors of the detectors must be kept within the allowable error in the entire pressure range, and the cost is high, or the pressure measurement range (hereinafter simply referred to as the measurement range) is narrow There was a problem of becoming.

  On the other hand, as in the case of the above-described conventional electronic imaging apparatus, in the case where the dynamic range is widened simply by combining two sensors having different sensitivities and measurement ranges, the pressure receiving member is a common pressure sensitive member. The present invention is not applicable to pressure detection devices, particularly pressure detection devices that require high pressure sensitivity in the entire pressure detection region in order to detect the fuel pressure used for calculating the fuel injection amount.

  Therefore, in the conventional pressure detection device in which the sensors are duplicated, sensors having the same measurement range and the same pressure sensitivity are used, and each sensor has a linearity compared to the required level in order to cover the entire measurement range. For example, sufficient pressure detection accuracy has not been obtained in response to demands for higher common rail pressure and precise fuel injection amount control in recent diesel engines.

  The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a low-cost pressure detection device capable of obtaining high pressure sensitivity in a wide range of total pressure detection regions.

In order to achieve the above object, the pressure detection device according to the present invention detects (1) a pressure receiving member that receives an input pressure, and changes in the state of the pressure receiving member according to the input pressure, First pressure detection means and second pressure detection means for outputting pressure detection signals corresponding to changes in different offset amounts and output ranges with respect to the same measurement pressure range, and pressure from the first pressure detection means A pressure detection signal indicating either a large or small pressure value on the side having a small detection error with respect to a preset detection characteristic reference is selected from the detection signal and the pressure detection signal from the second pressure detection means. includes an output selecting means for determining the measurement value indicating the detected pressure, wherein the offset amount while the direction of the first pressure detecting means is less than said second pressure detecting means, the output range The first pressure detection means is larger than the second pressure detection means, and the difference between the pressure detection signal of the first pressure detection means and the pressure detection signal of the second pressure detection means is preset. The offset amount and the output range in the first pressure detection means and the second pressure detection means are set to be always smaller than the set threshold value, and the pressure of the first pressure detection means The difference is set to be larger than the threshold when an abnormality occurs in either the detection signal or the pressure detection signal of the second pressure detection means .

With this configuration, a pressure detection signal with a small offset amount is output from the pressure detection means having a wide output range among the first pressure detection means and the second pressure detection means in response to a change in the state of the pressure receiving member. By outputting a pressure detection signal with a large offset amount from the narrow pressure detection means, two types of pressure detection signals corresponding to the input pressure are detected, and the pressure detection signal from the pressure detection means having a narrow output range on the low pressure side. The pressure detection signal from the pressure detection means having a wide output range tends to increase on the high pressure side, and is output respectively. Of these pressure detection signals, the pressure detection signal that is close to the required linear characteristic and has a smaller detection error is selected, and the measurement value is determined. Therefore, while using a plurality of pressure detection means having relatively similar sensitivities, pressure detection accuracy that cannot be obtained by themselves can be obtained, and the yield can be improved. In addition, when the difference between the signal levels of the pressure detection signals of the two pressure detection means becomes larger than the threshold value, it becomes possible to detect that an abnormality has occurred in one of the pressure detection means, and the reliability due to the duplication of the pressure detection means. Improvements can be made. The different offset amount and output range in the present invention may be due to, for example, a difference in characteristics of the detection element that detects a change in the state of the pressure receiving member, or due to a difference in characteristic adjustment of the detection element. In the latter case, for example, a single detection element having high reliability may be used. Further, the pressure receiving member may be one having a plurality of detection sites resulting equivalent strain may be a plurality of receiving members, in the latter case it is also possible to produce a difference in detection characteristics by the pressure-receiving member .

  In the pressure detecting device having the configuration described in (1) above, (2) the first pressure detecting means and the second pressure detecting means are configured so that the pressure receiving member is distorted according to the input pressure. And a first sensor and a second sensor that output a pressure detection signal corresponding to the strain, and an offset amount and output of the pressure detection signal from the first sensor with respect to a pressure measurement range input to the pressure receiving member It is preferable that the characteristic adjustment circuit is configured to set the offset and the output range of the pressure detection signal from the second sensor with respect to the measurement range to different sizes.

  With this configuration, while improving reliability by the dual sensor configuration of the same measurement range, pressure detection accuracy that cannot be achieved by the conventional dual sensor configuration can be obtained, and the yield can be improved. Note that the term “duplex” as used herein means that a double component that constitutes a part of the multiple configuration is included.

  In the pressure detection device having the configuration described in (2) above, (3) the first sensor and the second sensor are sensors of the same specification, and the first pressure that causes the same strain among the pressure receiving members is generated. It is preferable to be mounted on the detection site and the second detection site.

  With this configuration, the existing dual sensor configuration employs a characteristic adjustment circuit that makes the offset amount and output range of the output signals of these sensors different from each other. By simply executing the process of selecting a detection signal, highly accurate pressure detection is possible, and a pressure detection device with high pressure detection accuracy can be obtained at low cost.

In the pressure detection device according to the above (2) or (3), (4) a characteristic that the pressure receiving member causes the distortion in accordance with a change in the input pressure is a measurement of the input pressure. The output selection means has a characteristic of approaching a straight line corresponding to the detection characteristic reference in the intermediate region of the range and moving away from the straight line to the smaller side of the distortion outside the intermediate region of the measurement range. Preferably, the measurement value is determined by selecting a pressure detection signal indicating a high pressure from the pressure detection signal from the pressure detection means and the pressure detection signal from the second pressure detection means.

  With this configuration, the detection characteristic in which the error increases from the ideal straight line to the smaller distortion side in the pressure region outside the intermediate region due to the strain characteristic according to the pressure of the pressure receiving member, and two pressure detections with different linear characteristic slopes By selecting a pressure detection signal indicating a high pressure among the pressure detection signals from the means, linearity can be improved and high pressure detection accuracy can be achieved.

In the pressure detection device according to (4) , (5) the first sensor has a small detection error with respect to the detection characteristic reference on the high pressure side of the measurement range, and the second sensor The detection error with respect to the detection characteristic reference is small on the low pressure side of the measurement range, and the output selection means uses a pressure detection signal indicating either the large or small pressure value on the low pressure side of the measurement range. More preferably, the pressure detection signal from the second sensor is selected, and the pressure detection signal from the first sensor is selected on the high pressure side of the measurement range .

  Further, in the pressure detection device according to the above (1) to (5), (6) the pressure receiving member receives the pressure of the fuel stored in the pressure accumulation state in the fuel pressure accumulation means of the internal combustion engine for the vehicle, and the output It is also preferable that the selecting means is constituted by an electronic control unit that controls the operation of the internal combustion engine.

  In this case, the linearity is good, and a low-cost pressure detection device capable of obtaining sufficient pressure detection accuracy with respect to the demand for high pressure accumulation level of the fuel pressure accumulation means and precise fuel injection amount control is obtained. Further, if the difference between the offset amount and the output range between the first and second pressure detecting means is set within a range where the abnormality can be detected, the abnormality detection of the pressure sensor and the reliability of the fuel pressure control are improved, and the accumulated pressure is increased. It is also possible to omit a pressure limiter that defines the upper limit value of the fuel pressure.

According to the present invention, the pressure detection signal from the pressure detection means having a narrow output range on the low pressure side from the first pressure detection means and the second pressure detection means having different offset amounts and output ranges of the pressure detection signal output. Since the pressure detection signal from the pressure detection means with a wide output range tends to increase on the high pressure side, and each pressure detection signal is output, the required linearity of these pressure detection signals Selects the pressure detection signal that is close to the characteristic and has the least detection error, determines the measurement value, and uses multiple pressure detection means with similar sensitivities, but provides pressure detection accuracy that cannot be obtained by themselves. Thus, it is possible to provide a low-cost pressure detection device with good yield. In addition, when the difference between the signal levels of the pressure detection signals of the two pressure detection means is larger than the threshold value, it is possible to detect that an abnormality has occurred in one of the pressure detection means, and the reliability of the pressure detection means is increased by duplication of the pressure detection means. A pressure detection device that can be improved can be provided.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a schematic block diagram of a pressure detection device according to the first embodiment of the present invention.

  First, the configuration will be described.

  As shown in FIG. 1, the pressure detection device of the present embodiment receives at least one pressure receiving member that receives the pressure of an input fluid and generates a strain corresponding to the pressure, for example, first and second pressure receiving members of the same specification. The members 11A and 11B (hereinafter referred to as pressure receiving members 11A and 11B are simply referred to as pressure receiving members 11) and the pressure change of the pressure receiving member 11 according to the pressure input to the pressure receiving member 11, for example, the change in strain amount are the same. First pressure detecting means 12 and second pressure detecting means 13 for detecting in a measurement range (a range in which the amount of change in strain can be measured) and outputting a pressure detection signal corresponding to the state change are provided. Yes.

  The pressure receiving member 11 is configured by a bottomed cylindrical stem, and a pressure-sensitive portion 11a on the bottom side thereof is formed relatively thin compared to the cylindrical portion 11b, and on the inner side of the cylindrical portion 11b. A pressure introducing hole 11h is formed, and a male screw 11c is formed on the outer periphery of the cylindrical portion 11b. The pressure receiving member 11 is fastened and fixed to one end portion of a common rail C, which is a fuel pressure accumulating means of a vehicular diesel engine (internal combustion engine), for example, by screw connection. Further, the pressure introducing hole 11h of the pressure receiving member 11 is opened in the common rail C, and the pressure of the fuel (fluid) accumulated in the common rail C is directly applied to the pressure sensing portion 11a of the pressure receiving member 11 from the pressure introducing hole 11h side. It comes to act on. When the pressure of the fuel in the common rail C increases due to the operation of the engine, the pressure receiving member 11 receives the fuel pressure on the inner surface side of the pressure sensing portion 11a, and the atmospheric pressure on the outer surface side (back side) of the pressure sensing portion 11a. In response, the pressure-sensitive part 11a is distorted so as to bend outward. Further, when the pressure of the fuel is reduced, the pressure sensitive portion 11a of the pressure receiving member 11 is elastically recovered inward and the strain generated in the pressure sensitive portion 11a is reduced.

  FIG. 2 is a graph showing the strain characteristics of the detection site on the outer surface side of the pressure-sensitive part 11a located at a specific radial position from the central axis of the pressure receiving member 11. The vertical axis is the strain amount at the detection site, and the horizontal axis is the horizontal axis. This is the pressure received by the pressure sensing part 11a of the pressure receiving member 11 (hereinafter also referred to as pressure receiving pressure).

  As shown in the figure, the pressure sensing part 11a of the pressure sensing member 11 which is a mechanical pressure sensing part has a very large pressure receiving pressure as it approaches the low pressure region where the pressure receiving pressure is very small and the elastic limit. In the high pressure region, the linearity of the pressure sensitivity decreases. Therefore, a pressure range in which a certain degree of linearity is obtained in the strain amount change of the pressure-sensitive member 11a of the pressure receiving member 11 is used as a measurement range (a range in which pressure can be measured) of the pressure detection device of the present embodiment. .

  The first pressure detecting means 12 and the second pressure detecting means 13 detect and detect the strain amount of the pressure sensing part 11a of the pressure receiving member 11 corresponding to the pressure receiving pressure (input pressure) of the pressure receiving member 11, respectively. The first sensor 21 and the second sensor 22 that output a pressure detection signal corresponding to the strain amount, and a characteristic adjustment circuit 23 that adjusts these characteristics. The characteristic adjustment circuit 23 detects the offset amount and output range of the pressure detection signal vs1 from the first sensor 21 with respect to the measurement range Rpv of the pressure input to the pressure receiving member 11, and the pressure detection from the second sensor 22 with respect to the same measurement range. The offset amount and the output range of the signal vs2 are configured to be different from each other, and have gain setting units 24a and 24b and offset adjustment units 25a and 25b.

  That is, the first pressure detection unit 12 and the second pressure detection unit 13 output pressure detection signals corresponding to changes in the strain amount of the pressure sensing portion 11a of the pressure receiving member 11 with different offset amounts and output ranges. It is like that. The offset amount here corresponds to the measurement value (output signal value) when detecting the lowest pressure in the measurement range, and the output range is the measurement when detecting the lowest pressure in the measurement range. It means the fluctuation range of the measured value from the value to the measured value when detecting the highest pressure.

  Specifically, the first sensor 21 and the second sensor 22 are composed of sensors of the same specification, and each of the pressure sensing portions 11a of the pressure receiving member 11 is detected at a detection site that generates equivalent strain, for example, a central detection site. It is installed. In addition, each sensor 21, 22 has two Wheatstone bridge circuits in which thin-film semiconductor strain resistors 21 a, 22 a are integrally attached to a pressure sensing part 11 a of a pressure receiving member 11, which is a special alloy diaphragm, via a glass film (not shown). The ASIC (Application Specific Integrated Circuit) is detected based on the detection voltages of the thin film semiconductor strain resistors 21a and 22a. And signal processing units 21b and 22b with built-in EEPROM (Electronically Erasable and Programmable Read Only Memory), respectively, perform known trimming processing, calibration correction, etc., thereby performing offset amount and amplification gain correction, temperature compensation, etc. Then, pressure detection signals vs1 and vs2 are output.

  The characteristic adjustment circuit 23 includes different characteristic adjustment data stored in the EEPROM in the two signal processing units 21b and 22b, and is configured as, for example, a part of the two signal processing units 21b and 22b. All or part of the ECU 30 is configured as one of functional units of the ECU 30 described later. Even in a conventional pressure detection device having a dual sensor configuration, sensor output offset amount correction and gain adjustment (sensitivity adjustment) are performed by a known trimming process or the like. Adjustment is made to the detection characteristics (sensitivity and output characteristics). On the other hand, in the present embodiment, the conditions for adjusting the characteristics of the first sensor 21 and the second sensor 22 are made different from each other, and the detection characteristics as shown in FIGS. 3A and 3B are obtained. It is the structure which produces the difference of.

  For this reason, the gain setting units 24a and 24b of the characteristic adjustment circuit 23 input values of the pressure detection signal vs1 from the first sensor 21 and the pressure detection signal vs2 from the second sensor 22 (hereinafter simply referred to as input values vs1 and vs2). The gain setting unit 24a multiplies the input value vs1 by the gain k1 and the gain setting unit 24b inputs the input value vs2. Is multiplied by a gain k2 different from the gain k1.

  In addition, the offset adjustment units 25a and 25b of the characteristic adjustment circuit 23 are configured to set different offset amounts Sf1 and Sf2 with respect to the pressure detection signals vs1 and k1 and vs2 and k2 from the gain setting units 24a and 24b, for example. Offset data to an offset ADC (not shown) in the processing units 21b and 22b is stored in the EEPROM as different values, and different offset amounts are set.

  As shown in FIGS. 3A and 3B, the difference between the gain k1 and the gain k2 set by the gain setting units 24a and 24b and the offset amounts Sf1 and Sf2 set by the offset adjusting units 25a and 25b are set. Due to this, the pressure detection signal vs1 · k1 output from the offset adjustment unit 25a (which means vs1 · k1 + Sf1 including the offset amount, simply referred to as vs1 · k1) is a measurement of the pressure input to the pressure receiving member 11. Is within the range of the output range Rg1 with respect to the range in which measurement is possible, ie, the measurement range Rpv. On the other hand, the pressure detection signal vs 2 · k 2 output from the offset adjustment unit 25 b (which is the meaning of vs 2 · k 2 + Sf 2 including the offset amount, simply referred to as vs 2 · k 2) is the output range Rg 1 with respect to the measurement range Rpv. It fluctuates within the range of the different output range Rg2. In FIG. 3, the case where the output range Rg1 is larger than the output range Rg2 is illustrated, but of course, the magnitude relationship may be reversed.

  The pressure detection signals vs1 · k1 and vs2 · k2 output from the offset adjusters 25a and 25b are respectively taken into an ECU (electronic control unit) 30 that electronically controls the vehicle internal combustion engine.

  Although the detailed hardware configuration is not illustrated, the ECU 30 is used for backup such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an EEPROM (Electronically Erasable and Programmable Read Only Memory), and the like. Non-volatile memory, an input interface circuit including an A / D converter and a buffer, and an output interface circuit including a drive circuit and the like are configured. In the backup memory by the CPU according to a control program stored in the ROM in advance. On the basis of the map information, set value information, sensor information, etc., while performing data processing with the RAM and executing arithmetic processing to execute known electronic control, the function of the output selecting means described later or further The function of the characteristic adjustment circuit 23 is exhibited.

  The ECU 30 adjusts an offset adjustment corresponding to the pressure detection signal vs1 · k1 from the offset adjustment unit 25 a corresponding to the pressure detection signal from the first pressure detection means 12 and the pressure detection signal from the second pressure detection means 13. Among the pressure detection signals vs2 and k2 from the unit 25b, a pressure detection signal indicating either the large or small pressure value on the side where the detection error is small is selected. It has the function of the output selection part 26 (output selection means) which determines the measured value which shows detected pressure. That is, the output selection unit 26 generates either the large or small pressure value on the side where the detection error is small when the pressure value vs1 · k1 is the first function and the pressure detection signal vs2 · k2 is the second function. Functions as a composite function.

  In the present embodiment, as shown in FIG. 2, the characteristic that the pressure receiving member 11 is distorted in accordance with the change in pressure input to the pressure sensing portion 11a is within the intermediate region of the input pressure measurement range Rpv. The low pressure side and the high pressure side, which are close to a straight line and are outside the intermediate region of the measurement range Rpv, have a characteristic of moving away from the straight line to the side with less strain. Therefore, as shown in FIG. 4, the output selection unit 26 indicates a higher pressure among the pressure detection signals vs1 · k1 from the first pressure detection means 12 and the pressure detection signals vs2 · k2 from the second sensor. The measurement value Pd is determined by selecting the pressure detection signal.

  In this case, with respect to the straight line Fn corresponding to the detection characteristic reference, the pressure detection signal vs 2 · k 2 corresponding to the output of the second sensor 22 exclusively in the pressure region on the low pressure side corresponds to the output of the first sensor 21. The pressure value is larger than vs1 · k1, and the pressure detection signal vs1 · k1 corresponding to the output of the first sensor 21 is larger than the pressure detection signal vs2 · k2 corresponding to the output of the second sensor 22 in the pressure region on the high pressure side. It tends to be a value.

  On the other hand, in the characteristic adjustment circuit 23 of the present embodiment, the difference (the signal level) between the pressure detection signal vs1 · k1 of the first pressure detection means 12 and the pressure detection signal vs2 · k2 that is the pressure detection signal from the second sensor. (The absolute value of the difference) is a threshold value Dpm (difference between the two pressure detection signals vs1 · k1, vs2 · k2 for detecting an abnormality in one of the first pressure detection means 12 and the second pressure detection means 13). No sign in the figure; in the first pressure detection means 12 and the second pressure detection means 13 so as to be always smaller than | (vs1 · k1 + Sf1) − (vs2 · k2 + Sf2) | <normal when Dpm) Offset amounts Sf1, Sf2 and output ranges Rg1, Rg2 of pressure detection signals vs1, k1, vs2, k2 are set, respectively. The method for setting the abnormality detection threshold value Dpm is well known and will not be described in detail. However, the value of the abnormality detection threshold value Dpm is determined from the maximum difference during normal fluctuation of the pressure detection signals vs1 · k1 and vs2 · k2. Is several times larger. In other words, the difference between the offset amount and the output range between the first pressure detection means 12 and the second pressure detection means 13 is sufficiently larger than the difference in the detected pressure value when an abnormality occurs in either one of them. It is small, for example, larger than the detection error, but within several times that value.

  Next, the operation will be described.

  In the present embodiment configured as described above, when high-pressure fuel discharged from the high-pressure fuel pump is supplied to the common rail C that is the pressure accumulating means during operation of the diesel engine for the vehicle, the fuel in the common rail C The pressure is received by the pressure sensing part 11 a of the pressure receiving member 11.

  At this time, from the first pressure detection means 12 and the second pressure detection means 13 having different linear characteristics required for the pressure detection device, from the second pressure detection means 13 having a narrow output range on the low pressure side. The pressure value vs2 · k2 which is the pressure detection signal of the pressure increases, and the pressure value vs1 · k1 which is the pressure detection signal from the first pressure detection means 12 having a wide output range tends to increase on the high pressure side. Pressure values vs1 · k1 and pressure values vs2 · k2 are output, respectively. Of these pressure values vs1 · k1 and vs2 · k2, the pressure value vs2 · k2 or vs1 · k1 on the high pressure side, which is close to the required linearity, that is, the straight line Fn corresponding to the detection reference characteristic and has a small detection error. Is selected, and the measured value Pd is determined. Therefore, while using a plurality of sensors 21 and 22 having similar sensitivities, as shown in FIG. 4, the pressure detection device of this embodiment is used for each of the detection errors e1 and e2 (see FIG. 3). The detection error epi is sufficiently reduced, and high pressure detection accuracy is obtained.

  In addition, the margin of the detection error epi with respect to the allowable error increases, the detection error on the high voltage side of the measurement range Rpv is managed within the allowable error for the first sensor 21, and the measurement range for the second sensor 22 is measured. Since it is only necessary to manage the detection error on the low pressure side of Rpv within an allowable error, the yield when manufacturing the detection device unit from the pressure receiving member 11 to the characteristic adjustment circuit 23 is greatly improved. . In this case, if the first sensor 21 and the second sensor 22 are selected from the characteristics immediately after manufacture of each sensor or the characteristics close to those shown in FIG. 3A or FIG. With the characteristic adjustment amount, the offset amount and the output range can be made different at a specific ratio.

  In the present embodiment, the first pressure detection means 12 and the second pressure detection means 13 detect the strain of the pressure receiving member 11 corresponding to the input pressure, and output pressure detection signals vs1 and vs2. The first sensor 21 and the second sensor 22 that are different from each other, the offset amount Sf1 of the pressure detection signal vs1 · k1 relative to the measurement range Rpv, and the offset amount Sf2 of the pressure detection signal vs2 · k2 and the output range Rg2 are different in magnitude. Pressure adjustment accuracy that could not be achieved with the conventional dual sensor configuration, while improving the reliability of the pressure inspection device with the dual sensor configuration. Can be obtained, and the yield can be improved.

  Furthermore, since the first sensor 21 and the second sensor 22 are sensors of the same specification and are mounted on the first detection site and the second detection site that cause the same strain in the pressure receiving member 11, the existing sensor Adopts a new characteristic adjustment circuit 23 that makes the offset amount and output range different from each other in the double sensor configuration of the same measurement range, and close to the required linear characteristic (linearity), detection A sensor abnormality can be detected only by executing the processing of the output selection unit 26 that selects the pressure detection signal on the side with less error and determines the measured value Pd, and yet can detect pressure with high accuracy. It becomes a cost pressure sensing device.

  In addition, the characteristic that the pressure receiving member 11 generates distortion according to the change in the input pressure approaches the straight line Ls (see FIG. 2) corresponding to the detection characteristic reference in the intermediate region of the input pressure measurement range Ppv. In the pressure region on the low pressure side and the high pressure side that are outside the intermediate region of the measurement range Rpv, the pressure selection unit 26 has a characteristic of moving away from the straight line Ls to the side where the strain is small. The pressure value vs1 · k1 or vs2 · k2 indicating a high pressure is selected and measured from the pressure value vs1 · k1 that is the detection signal and the pressure value vs2 · k2 that is the pressure detection signal from the second pressure detection means 13. Since the value Pd is determined, the detection characteristic in which the error increases from the ideal straight line Fn to the smaller distortion side in the pressure region outside the intermediate region due to the distortion characteristic of the pressure sensing portion 11a of the pressure receiving member 11 is expressed as a linear characteristic. By selecting a pressure detection signal indicating a high pressure from the pressure detection signals vs1 · k1 and vs2 · k2 from the two pressure detection means 12 and 13 having different inclinations, linearity can be obtained without impairing the continuity of the measurement values. High pressure detection accuracy can be achieved.

  In addition, in this embodiment, the difference (absolute value) in signal level between the pressure detection signal vs1 · k1 of the first pressure detection means 12 and the pressure detection signal vs2 · k2 of the second pressure detection means 13 is The first pressure detection means 12 and the second pressure detection means are always smaller than the threshold value Dpm for detecting any abnormality of the first pressure detection means 12 and the second pressure detection means 13. Since the offset amounts Sf1 and Sf2 and the output ranges Rg1 and Rg2 at 13 are set, respectively, a plurality of pressure detecting means 12 and 13 having similar sensitivities are used, and pressure detection accuracy that cannot be obtained by themselves can be obtained. The difference between the signal levels of the pressure detection signals vs1 · k1 and vs2 · k2 of both the pressure detection means 12 and 13 is not only the threshold value Dpm for abnormality detection. When even larger Ri, can detect that the abnormality in one of the pressure detecting means 12 and 13 occurs, it is possible to improve the reliability of the pressure sensor according to duplexing sensor.

  Moreover, in this embodiment, the pressure receiving member 11 receives the pressure of the fuel stored in the pressure accumulation state on the common rail C which is the fuel pressure accumulation means of the diesel engine for the vehicle, and the output selection unit 26 controls the operation of the engine. Since it is configured by the ECU 30, the pressure detection characteristic has good linearity, and low pressure that can provide sufficient pressure detection accuracy to meet the demand for higher pressure accumulation level of the common rail C and precise fuel injection amount control. It can be set as a pressure detection apparatus. Further, by setting the offset amounts Sf1 and Sf2 between the first and second pressure detection means 12 and 13 and the difference between the output ranges Rg1 and Rg2 as described above, the abnormality can be detected. Thus, the reliability of the fuel pressure control is improved, and a pressure limiter that defines the upper limit value of the accumulated fuel pressure can be omitted, and the manufacturing cost of the pressure detection device can be reduced.

  Thus, according to the pressure detection device of the present embodiment, from the first pressure detection means 12 and the second pressure detection means 13 having different slopes of the linear characteristics (linearity) required as the pressure detection device, On the low pressure side, the pressure value vs2 · k2, which is a pressure detection signal from the second pressure detection means 13 with a narrow output range, becomes large, and on the high pressure side, the pressure detection from the first pressure detection means 12 with a wide output range. Since the pressure values vs1 · k1, which are signals, tend to increase and pressure detection signals are output, the pressure values vs1 · k1 and vs2 · k2 are close to the required linear characteristics, and detection errors are detected. The pressure value vs1 · k1 or vs2 · k2 on the side having a smaller value is selected to determine the measurement value Pd, and while using a plurality of pressure detection means 12 and 13 having similar sensitivities, they alone Obtained is not obtained pressure detection accuracy, it can yield to provide a pressure detecting apparatus good low cost.

(Second Embodiment)
FIG. 5 is a schematic block diagram of a pressure detection device according to the second embodiment of the present invention. Although this embodiment is different from the first embodiment in the number of pressure receiving members, most of the other configurations are the same as those in the first embodiment. Therefore, in the following description, the common configurations are described above. Differences will be described in detail using the same reference numerals as those in the first embodiment.

  As shown in FIG. 5, the pressure detection apparatus of the present embodiment receives one pressure receiving member 11 that receives the pressure of the input fluid and generates a strain corresponding to the pressure, and the pressure input to the pressure receiving member 11. The first pressure detecting means 12 and the second pressure detecting means 13 for detecting a change in the state of the pressure receiving member 11 corresponding thereto, for example, a change in the amount of strain in the same measurement range and outputting a pressure detection signal corresponding to the state change. And.

  The first pressure detection means 12 and the second pressure detection means 13 detect the strain amount of the pressure sensing part 11a of the pressure receiving member 11 according to the pressure received by the pressure receiving member 11, respectively, and correspond to the detected strain amount. The first sensor 21 and the second sensor 22 that output pressure detection signals, and the characteristic adjustment circuit 23 similar to that of the above-described first embodiment for adjusting these characteristics, are used to sense the common pressure receiving member 11. Pressure detection signals corresponding to changes in the strain amount of the pressure unit 11a are output with different offset amounts and output ranges.

  Specifically, the first sensor 21 and the second sensor 22 are configured by sensors having the same specifications as those in the first embodiment described above, and detection that causes distortion equivalent to each other in the pressure-sensitive portion 11a of the pressure receiving member 11 is performed. The first detection part and the second detection part, which are opposite positions on the same circumference of the part, for example, the pressure sensing unit 11a, are respectively attached.

  Even in this configuration, when high-pressure fuel discharged from the high-pressure fuel pump is supplied to the common rail C during operation of the vehicle diesel engine, the fuel pressure in the common rail C is changed to the pressure-sensitive portion of the pressure receiving member 11. The pressure is received by 11a. At this time, from the first pressure detection means 12 and the second pressure detection means 13 having different linear characteristics required for the pressure detection device, from the second pressure detection means 13 having a narrow output range on the low pressure side. The pressure value vs2 · k2 which is the pressure detection signal of the pressure increases, and the pressure value vs1 · k1 which is the pressure detection signal from the first pressure detection means 12 having a wide output range tends to increase on the high pressure side. Pressure values vs1 · k1 and pressure values vs2 · k2 are output, respectively. Of these pressure values vs1 · k1 and vs2 · k2, the pressure value vs2 · k2 or vs1 · k1 on the high pressure side, which is close to the required linearity, that is, the straight line Fn corresponding to the detection reference characteristic and has a small detection error. Is selected, and the measured value Pd is determined. Therefore, the same effect as that of the first embodiment can be expected.

  In each of the above-described embodiments, the first sensor 21 and the second sensor 22 have the same specification. However, for example, the resistance value of the bridge circuit inside the sensor is made different from that of the first sensor 21. The detection characteristic itself of the second sensor 22 is slightly different, or the shape and thickness of the detection part in the pressure sensing part 11a of the pressure receiving member 11 and the sensor mounting position are set so that the pressure sensitivity is slightly different. Is also possible. That is, the first pressure detection means and the second pressure detection means referred to in the present invention are limited to those in which the sensors having the same specification are duplicated and the offset amount and the output range are made different by the signal processing units 21b and 22b. It is not a thing.

  Further, in each of the above-described embodiments, a double sensor configuration is used, but it is also possible to adopt a sensor configuration in which three or more layers are multiplexed. In this case, the pressure detection characteristics of three or more pressure detection means The slopes of the straight lines indicating the reference characteristics are different from each other, and the pressure detection signals from the respective pressure detection means are used in a region close to the ideal straight line.

  Further, the first pressure detection means and the second pressure detection means are integrated with only the thin-film semiconductor strain resistance 21a as a common / single detection element, for example, via the glass film on the pressure sensing portion 11a of the pressure receiving member 11. One Wheatstone bridge circuit may be configured by mounting. In this case, the single thin-film semiconductor strain resistance detection signal is processed by the signal processing unit 21b including one ASIC and EEPROM, and subsequent characteristic adjustment such as gain adjustment and offset adjustment is performed by the characteristic adjustment circuit 23. Two types of pressure detection signals vs1 · k1 and vs1 · k2 are generated by taking in heavy. Even if it does so, the linearity as a pressure detection apparatus can be improved.

  In each of the above-described embodiments, the characteristic adjustment circuit 23 performs the offset amount setting after executing the gain adjustment first, but conversely, the characteristic adjustment circuit 23 may perform the gain adjustment after setting the offset amount.

  Further, the change in the state of the pressure receiving member detected by the pressure detecting means is not limited to the strain, and the pressure value can be calculated from the difference in resonance frequency as described in Patent Document 1, or the displacement and deformation amount of the pressure receiving unit can be calculated. The pressure value may be calculated by detection.

  Furthermore, depending on the form of the pressure receiving member, unlike the above-described embodiments in which the sensitivity characteristic is convex upward, it may be convex downward. In that case, from the first and second pressure detecting means, Any one of the large and small pressure values on the side where the detection error is small becomes a pressure detection signal indicating a small pressure value. Further, when the characteristic curve meanders, it can be considered as a combination of a case where the characteristic curve is convex upward and a case where the characteristic curve is downward.

  As described above, the pressure detection device according to the present invention has an output range on the low pressure side from the first pressure detection unit and the second pressure detection unit that have different linear characteristics required for the pressure detection device. The pressure detection signal from the narrow pressure detection means tends to increase, and the pressure detection signal from the pressure detection means with a wide output range tends to increase on the high pressure side. Select the pressure detection signal that is close to the required linear characteristic among the pressure detection signals of the above, and determine the measurement value by selecting the pressure detection signal on the side where the detection error is small, while using a plurality of pressure detection means having similar sensitivity, Therefore, it is possible to provide a low-cost pressure detection device that can provide pressure detection accuracy that is not obtained by the above-mentioned method and that has a good yield. The pressure input is useful for pressure detection device which outputs a pressure detection signal corresponding to the state change is receiving the pressure receiving member.

1 is a schematic block configuration diagram of a pressure detection device according to a first embodiment of the present invention. It is a graph which shows the distortion characteristic of the detection site | part in a specific radial position from the pressure-sensitive part center of the pressure receiving member of the pressure detection apparatus which concerns on 1st Embodiment of this invention, A vertical axis | shaft is the distortion amount in the detection site | part, a horizontal axis Indicates the pressure received by the pressure-sensitive portion of the pressure-receiving member. It is a characteristic view which shows the detection characteristic of the 1st pressure detection means of the pressure detection apparatus which concerns on 1st Embodiment of this invention, and a 2nd pressure detection means. It is a characteristic view which shows the final detection characteristic which selectively uses the pressure detection signal from the 1st pressure detection means of the pressure detection apparatus which concerns on 1st Embodiment of this invention, and a 2nd pressure detection means. It is a schematic block block diagram of the pressure detection apparatus which concerns on 2nd Embodiment of this invention.

Explanation of symbols

11, 11A, 11B Pressure receiving member 11a Pressure sensing portion 11b Tubular portion 12 First pressure detecting means 13 Second pressure detecting means 21 First sensor 22 Second sensor 23 Characteristic adjusting circuits 24a, 24b Gain setting portions 25a, 25b Offset adjustment unit 26 Output selection unit (output selection means)
30 ECU (Electronic Control Unit)
epi detection error k1, k2 gain Pd measured value Rg1, Rg2 pressure detection signal output range vs1, k1, vs2, k2 pressure detection signal (pressure value)

Claims (6)

A pressure receiving member that receives the input pressure;
A first pressure that detects a change in the state of the pressure receiving member in accordance with the input pressure and outputs a pressure detection signal corresponding to the change in the state with a different offset amount and output range for the same measurement pressure range. Detection means and second pressure detection means;
Of the pressure detection signal from the first pressure detection means and the pressure detection signal from the second pressure detection means, one of the large and small pressures on the side having a small detection error with respect to a preset detection characteristic reference An output selecting means for selecting a pressure detection signal indicating a value and determining a measurement value indicating the detected pressure; and
The offset amount is smaller in the first pressure detection means than in the second pressure detection means, while the output range is larger in the first pressure detection means than in the second pressure detection means. The first pressure detection means and the first pressure detection means and the pressure detection signal of the first pressure detection means and the pressure detection signal of the second pressure detection means are always smaller than a preset threshold value. The offset amount and the output range in the second pressure detecting means are set, respectively.
The difference is set to be larger than the threshold when an abnormality occurs in any one of the pressure detection signal of the first pressure detection means and the pressure detection signal of the second pressure detection means. Pressure detection device. The first pressure detection means and the second pressure detection means are:
A first sensor and a second sensor, each detecting a strain of the pressure receiving member corresponding to the input pressure, and outputting a pressure detection signal corresponding to the strain;
The offset amount and output range of the pressure detection signal from the first sensor with respect to the measurement range of the pressure input to the pressure receiving member, and the offset amount and output range of the pressure detection signal from the second sensor with respect to the measurement range The pressure detection device according to claim 1, wherein the pressure detection device is configured by a characteristic adjustment circuit that sets different sizes.   The first sensor and the second sensor are sensors of the same specification, and are attached to a first detection site and a second detection site that generate equivalent strains in the pressure receiving member. Item 3. The pressure detection device according to Item 2. The characteristic in which the pressure-receiving member generates the distortion in response to the change in the input pressure approaches a straight line corresponding to the detection characteristic reference in the intermediate region of the input pressure measurement range, and the middle of the measurement range Having a characteristic of moving away from the straight line to the smaller side of the strain outside the region;
The output selection means selects the pressure detection signal indicating a high pressure from the pressure detection signal from the first pressure detection means and the pressure detection signal from the second pressure detection means, and determines the measurement value. The pressure detection device according to claim 2 or claim 3 , wherein The first sensor has a small detection error with respect to the detection characteristic reference on the high pressure side of the measurement range, and the second sensor has a small detection error with respect to the detection characteristic reference on the low pressure side of the measurement range. And
The output selection means selects a pressure detection signal from the second sensor on the low pressure side of the measurement range as a pressure detection signal indicating one of the large and small pressure values, and on the high pressure side of the measurement range. The pressure detection device according to claim 4, wherein a pressure detection signal from the first sensor is selected.   The pressure receiving member receives a pressure of fuel stored in a pressure accumulation state in a fuel pressure accumulation means of an internal combustion engine for a vehicle, and the output selection means is constituted by an electronic control unit that controls the operation of the internal combustion engine. The pressure detection device according to any one of claims 1 to 5.

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