JP2013125023A - Pressure measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a detection (measurement) error by temperature drift of a pressure sensor on the basis of a simple and inexpensive configuration.SOLUTION: A pressure measuring instrument includes a pressure sensor 25, temperature stabilization means 26 for stabilizing the detection part temperature of the pressure sensor 25 to a prescribed level, learning means (with reference to Fig.2, Fig.3) for storing an output value of the pressure sensor 25 as a learning value of a zero point output while the detection part temperature of the pressure sensor 25 is stabilized to the prescribed level, and arithmetic means for outputting a pressure measurement value calculated from the output value of the pressure sensor 25 and the learning value while the detection part temperature of the pressure sensor 25 is stabilized to the prescribed level.

Description

  The present invention relates to a pressure measuring device, and more particularly to a technique for preventing a detection (measurement) error due to a temperature drift of a pressure sensor.

  The pressure sensor is used, for example, to measure the pressure of a fluid flowing through a pipe. The pressure sensor has temperature dependence, and the output of the pressure sensor varies according to the temperature change. That is, when the temperature of the pressure sensor changes, the output of the pressure sensor drifts with respect to the same fluid pressure. This variation is called temperature drift. As a conventional technique for dealing with this temperature drift, a technique disclosed in Patent Document 1 is known.

  In such a conventional technique, memory means for storing the temperature drift characteristics of the pressure sensor (relationship between the temperature and the output of the pressure sensor) is provided, and the temperature of the pressure sensor is determined from the temperature detected by the temperature sensor and the data of the memory means. The output of the pressure sensor is corrected so as to eliminate the calculated value (output drift amount) by calculating the output drift amount.

JP 2003-194648 A

  In such a conventional technique, there is a problem that the amount of data stored in the memory means becomes enormous and the setting of the memory means is expensive.

  The present invention has been made in view of such problems. By maintaining the temperature environment around the pressure sensor in a stable state, the pressure sensor can be easily detected while reducing the data setting cost. (Measurement) An object of the present invention is to provide a pressure measuring device with improved accuracy.

  The present invention relates to a pressure sensor, temperature stabilization means for stabilizing the temperature of the detection unit of the pressure sensor to a predetermined level, and an output value of the pressure sensor in a state where the temperature of the detection unit of the pressure sensor is stabilized to a predetermined level. Learning means for storing a zero point output as a learning value, and a pressure measurement value calculated from the output value of the pressure sensor and the learning value in a state where the detection unit temperature of the pressure sensor is stabilized at the predetermined level. And a calculating means for outputting.

  In the present invention, even in the learning process of storing the output value of the pressure sensor as the learning value of the zero point output by the temperature stabilizing unit that stabilizes the temperature of the detection part of the pressure sensor at a predetermined level, the output value of the pressure sensor Also in the arithmetic processing for outputting the pressure measurement value calculated from the learning value, these are performed in a state where the detection unit temperature of the pressure sensor is stabilized at a predetermined level. That is, since the fluctuation of the temperature sensor detection unit temperature is suppressed to a predetermined level, the output of the calculation means (the pressure measurement value calculated from the pressure sensor output value and the learned value) is the temperature. It contains almost no drift error. Even if an error corresponding to the temperature drift occurs, the error is limited to a very small fluctuation occurring in the temperature of the detection portion of the pressure sensor in a state where the error is stabilized at a predetermined level. Accordingly, the temperature stabilization means for stabilizing the detection part temperature of the pressure sensor to a predetermined level can increase the pressure measurement accuracy based on the detection of the pressure sensor based on a simple and inexpensive configuration.

It is a general | schematic block diagram explaining embodiment of this invention. It is a flowchart explaining a learning means similarly. It is a characteristic view explaining an effect similarly. It is a flowchart explaining another learning means.

  A pressure measuring device according to an embodiment of the present invention will be described based on the drawings. 1 to 3 show examples of application to a control system of an internal combustion engine.

  In FIG. 1, reference numeral 10 denotes an internal combustion engine (engine). The internal combustion engine 10 has a water jacket (not shown) formed around each cylinder, and constitutes a circulation path of an engine cooling system.

  11 is an intake passage, 12 is an exhaust passage, and intake air flows through the intake passage 11 and is supplied from the intake manifold 13 to each cylinder. The exhaust from each cylinder flows from the exhaust manifold 14 through the exhaust passage 12 and is discharged to the outside.

  A compressor of a turbocharger 15 is interposed in the intake passage 11, and an intercooler 16 (device for cooling the supercharged air) is provided in the intake passage downstream of the compressor. A turbine of a turbocharger 15 is interposed in the exhaust passage 12 and rotates with exhaust energy to drive a coaxial compressor.

  Reference numeral 18 denotes an EGR (exhaust gas recirculation device) passage (EGR pipe) that connects between the exhaust manifold 14 and the intake passage 11. The EGR pipe 18 is provided with an EGR cooler 19 (equipment for cooling EGR gas) and an EGR valve 20 (EGR gas amount adjusting valve).

  In order to control the opening degree (EGR gas amount) of the EGR valve 20, means for detecting the engine operating state (for example, an engine rotation sensor or an engine load sensor) and the opening degree (EGR) of the EGR valve 20 based on the detection signal. And a control unit (not shown) for controlling the gas amount.

  In order to detect the actual amount of EGR gas, a venturi 21 is set in the EGR passage 18 and a pressure sensor 25 for detecting the pressure on the upstream side thereof is provided. The control unit determines the actual EGR amount based on the target opening degree (target value of the EGR amount) corresponding to the engine operating state and the actual value of the EGR amount calculated from the measured pressure based on the output of the pressure sensor 25. The opening degree of the EGR valve 20 is controlled so that the value = the target value of the EGR amount.

  Since the output of the pressure sensor 25 includes a temperature drift, a temperature stabilization means 26 for stabilizing the detection unit temperature of the pressure sensor 25 to a predetermined level is provided to cope with this.

  The temperature stabilization means 26 includes a heat insulator 27 (heat retention chamber) formed so as to surround the detection portion of the pressure sensor 25. The warmer 27 constitutes a passage through which fluid flows, and coolant that circulates through the engine cooling system is used as fluid flowing through the passage in the warmer 27.

  Specifically, the warmer 27 is interposed in the circulation path of the engine cooling water. 28 is a pipe (cooling water passage) for connecting the warmer 27 to the water jacket of the engine cylinder block, and 29 is a pipe (cooling water passage) for connecting the warmer 27 to the water jacket of the engine cylinder head.

  During engine operation, the cooling water of the engine cooling system circulates via the heat retaining device 27. The engine cooling water is maintained at a predetermined level (predetermined temperature range) by the action of a radiator or the like when the water temperature rises above a predetermined value during engine operation. The ambient temperature around the 25 detection units is stabilized in a predetermined temperature range.

  The warmer 27 is formed so as to enclose the pressure sensor 25, and defines a chamber (pressure chamber) around the detection portion of the pressure sensor 25. The pressure sensor 25 is disposed away from the EGR passage 18. The chamber (not shown) is connected to one end of a tube (pressure guiding pipe), and the other end of the tube is opened upstream of the venturi 21 in the EGR passage 18. The pressure on the upstream side of the venturi 21 is introduced through a tube (pressure guiding pipe) into the chamber of the pressure sensor 25 away from the EGR passage 18.

  In a control unit (not shown), learning means (FIG. 5) stores an output value (voltage value) of the pressure sensor 25 as a learning value of zero point output in a state where the detection unit temperature of the pressure sensor 25 is stabilized at a predetermined level. 2), and a calculation means for outputting a pressure measurement value calculated from the output (voltage) of the pressure sensor 25 and the learning value in a state where the detection unit temperature of the pressure sensor 25 is also stabilized at a predetermined level. Provided.

  FIG. 2 is a flowchart for explaining the processing contents of the learning means. When the internal combustion engine 10 (engine) is started in S1, the process proceeds to S2, and based on the detection signal of the water temperature sensor that detects the cooling water temperature of the engine cooling system. Then, it is determined whether the engine coolant temperature is equal to or higher than a predetermined value.

  If the determination in S2 is NO, the process waits until the determination in S2 becomes YES (the determination in S2 is repeated). If the determination in S2 is YES, the process proceeds to S3 and the timer is activated. The timer measures the passage of a predetermined time. Here, the predetermined time means an engine operation time required to keep the engine cooling water temperature in a stabilized state at a predetermined level until the output decrease of the pressure sensor 25 settles after the engine stop described later.

  In S4, it is determined whether or not the timer measurement (elapse of a predetermined time) has ended. When the determination of S4 is NO, the process waits until the determination of S4 becomes YES (the determination of S4 is repeated).

  If the determination in S4 is YES, the process proceeds to S5 and the learning condition is satisfied. In S6, it is determined whether the key is off. When the determination in S6 is NO, the process waits until the determination in S6 becomes YES (the determination in S6 is repeated). If the determination in S6 is YES, the process proceeds to S7, and it is determined in S7 that the engine is stopped. As the engine stops, the pressure in the EGR passage rapidly decreases, so the output (voltage) of the pressure sensor 25 also suddenly decreases to 0 and stabilizes. In S7, it is determined whether the output decrease of the pressure sensor 25 is in a stable state after the engine is stopped.

  If the determination in S7 is NO, the process waits until the determination in S7 becomes YES (repeats the determination in S7). If the determination in S7 is YES, the process proceeds to S8, and the stabilized output value of the pressure sensor 25 is stored as a learning value for zero point output.

  Therefore, after the internal combustion engine 10 is started, the engine coolant temperature becomes equal to or higher than the predetermined temperature, and the temperature stabilization time of the pressure sensor 25 that is the learning condition of the pressure sensor 25 is obtained from that point. After the stabilization time has elapsed, the internal combustion engine is stopped by key-off, and when the output drop of the pressure sensor 25 is stabilized, the output of the pressure sensor 25 at that time is stored as a learning value of zero point output.

  In the control unit, it is determined whether or not the temperature of the detection portion of the pressure sensor 25 is stabilized at a predetermined level from the coolant temperature during engine operation. Under the condition that this determination is YES, the calculation means is the pressure sensor. The pressure measurement value calculated from the output of 25 and the learning value is output. The opening degree of the EGR valve is controlled based on the measured pressure value (output of the calculation means) and the target value of the EGR amount corresponding to the engine operating state.

  With such a configuration, during engine operation, the ambient temperature (indoor temperature) around the detection portion of the pressure sensor 25 is maintained in a stabilized state at a predetermined level by the engine cooling water circulating in the warmer 27.

  In this learning process, the process of S8 (the zero point output storage process) is also performed in a state where the ambient temperature around the detection portion of the pressure sensor 25 is stabilized at a predetermined level. During engine operation, fluctuations in the ambient temperature around the detection part of the pressure sensor 25 are suppressed to a predetermined level by the engine cooling water circulating in the heat retaining device 27, so that the output of the calculation means (output of the pressure sensor 25) And the pressure measurement value calculated from the learned value) contain almost no error due to temperature drift.

  Even if an error due to temperature drift occurs in the pressure measurement value, the error is limited to a very small fluctuation occurring in the ambient temperature around the detection portion of the pressure sensor 25 as shown in FIG. In FIG. 3, a solid line Td is an output characteristic of the pressure sensor 25, and the ambient temperature (sensor temperature in the figure) around the detection portion of the pressure sensor 25 is stabilized between A and B ° C. during engine operation. It is.

  As a result, temperature stabilization means for stabilizing the ambient temperature around the detection portion of the pressure sensor 25 to a predetermined level is provided, so that the accuracy of pressure measurement based on the output of the pressure sensor 25 is effectively based on a simple and inexpensive configuration. Can be increased.

  The learning process in FIG. 2 is performed only once after the manufacture of the vehicle is completed. In a vehicle manufacturing factory, it is desirable to be performed at a stage before shipment (carrying out from the factory to a dealer).

  FIG. 4 is a flowchart for explaining the processing contents of another learning means. Unlike the learning process of FIG. 2, this process is arbitrarily executed when necessary (such as during periodic inspection).

  In S1, it is determined whether or not the pressure sensor drift correction (zero point output correction) is necessary. For example, it is determined whether a learning switch (artificial operation switch) is on.

  When the determination of S1 is YES, the process proceeds to S2, and when the determination of S1 is NO, this learning process is terminated. When the internal combustion engine 10 (engine) is started in S2, the process proceeds to S3. In S3, it is determined whether the engine cooling water temperature is equal to or higher than a predetermined value based on a detection signal from a water temperature sensor that detects the engine cooling water temperature.

  When the determination of S3 is NO, the process waits until the determination of S3 becomes YES (repeats the determination of S2). If the determination in S3 is YES, the process proceeds to S4 and the timer is activated. The timer measures the passage of a predetermined time. Here, the predetermined time means an engine operation time required to keep the engine cooling water temperature in a stabilized state at a predetermined level until the output decrease of the pressure sensor 25 settles after the engine stop described later.

  In S5, it is determined whether the timer measurement (elapse of a predetermined time) has ended. When the determination at S55 is NO, the process waits until the determination at S5 becomes YES (the determination at S4 is repeated). If the determination in S5 is YES, the process proceeds to S6 and the learning condition is satisfied. In S7, it is determined whether or not the key has been turned off within a predetermined time from the establishment of the learning condition. If the determination in S7 is NO, this process ends. If the determination in S7 is YES, the process proceeds to S8. In S8, it is determined whether or not the engine is stopped. As the engine stops, the pressure in the EGR passage rapidly decreases, so the output (voltage) of the pressure sensor 25 also suddenly decreases to 0 and stabilizes. In S8, it is determined whether the output decrease of the pressure sensor 25 is in a stable state after the engine is stopped.

  If the determination in S8 is NO, the process waits until the determination in S8 becomes YES (repeats the determination in S8). If the determination in S8 is YES, the process proceeds to S9, and the stabilized output value of the pressure sensor 25 is stored as a learning value for zero point output.

  Therefore, after the internal combustion engine 10 is started, the engine coolant temperature becomes equal to or higher than a predetermined temperature, and the temperature stabilization time of the pressure sensor 25 that is a learning condition of the pressure sensor 25 is waited from that time. After the stabilization time has elapsed, when the internal combustion engine is stopped by key-off and the output drop of the pressure sensor 25 is stabilized, the output of the pressure sensor 25 at that time is stored as a learning value of zero point output.

  In the control unit, it is determined whether or not the temperature of the detection portion of the pressure sensor 25 is stabilized at a predetermined level from the coolant temperature during engine operation. Under the condition that this determination is YES, the calculation means is the pressure sensor. The pressure measurement value calculated from the output of 25 and the learning value is output. The opening degree of the EGR valve is controlled based on the measured pressure value (output of the calculation means) and the target value of the EGR amount corresponding to the engine operating state.

  In this learning process, the process of S9 (the zero point output storage process) is also performed in a state where the ambient temperature around the detection portion of the pressure sensor 25 is stabilized at a predetermined level. During engine operation, fluctuations in the ambient temperature around the detection part of the pressure sensor 25 are suppressed to a predetermined level by the engine cooling water circulating in the heat retaining device 27, so that the output of the calculation means (output of the pressure sensor 25) And the pressure measurement value calculated from the learning value) contain almost no error due to temperature drift (see FIG. 3).

  As the learning means, any one of the processing in FIG. 2 and the processing in FIG. 4 may be set. Also, when both are set, the process of FIG. 2 is selected at the time of correction (zero point output storage process) for the first time after the vehicle is manufactured, and the process of FIG. 3 is selected at the second and subsequent corrections. In this case, the stored value of S8 in FIG. 2 (the learned value of zero point output) is updated to the stored value of S9 in FIG. 3 (the learned value of zero point output).

  The pressure measuring device according to the present invention is not limited to a pressure sensor used for controlling an internal combustion engine, and any pressure detection method is used for pressure sensors applied to various fields, and there is a temperature drift. It can be used widely.

10 Internal combustion engine
DESCRIPTION OF SYMBOLS 11 Intake passage 12 Exhaust passage 18 EGR passage 20 EGR valve 25 Pressure sensor 26 Temperature stabilization means 27 Incubator 28, 29 Engine cooling water piping

Claims (5)

  A pressure sensor, temperature stabilization means for stabilizing the temperature of the detection part of the pressure sensor to a predetermined level, and output of the pressure sensor in a state where the temperature of the detection part of the pressure sensor is stabilized at a predetermined level. Learning means for storing as a learned value, and computing means for outputting a pressure measurement value calculated from the output value of the pressure sensor and the learned value in a state where the detection unit temperature of the pressure sensor is stabilized at the predetermined level And a pressure measuring device.   The temperature stabilization means includes a warmer formed so as to surround the detection portion of the pressure sensor, and the warmer constitutes a passage through which a fluid flows, and the warmer in the warmer 2. The pressure measuring device according to claim 1, wherein cooling water circulating in a cooling system of the internal combustion engine is used as a fluid flowing through the passage.   The learning means waits until the engine cooling water temperature becomes equal to or higher than a predetermined temperature after the internal combustion engine is started and a predetermined time elapses from that point, and after the internal combustion engine is stopped, the engine cooling water temperature is stabilized to be equal to or higher than the predetermined temperature. 3. The pressure measuring device according to claim 2, wherein when the output drop of the pressure sensor is stabilized, the stabilized output value is stored as a learning value of the zero point output.   2. The pressure sensor includes: a chamber defined by the warmer so as to surround a detection unit of the pressure sensor; and a conduit for guiding the pressure of a measurement target to the chamber. The pressure measuring device according to any one of claims 3 to 4.   The pressure measuring device according to any one of claims 1 to 4, wherein the pressure sensor is a pressure sensor used to control an EGR amount of an internal combustion engine.

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