JP2011080876A - Pressure detection unit and gas meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a space-saving pressure detection unit and a gas meter. <P>SOLUTION: The pressure detection unit 47 includes: a pressure sensor S; a usual pressure detection circuit 47a for measuring pressure based on a signal from the pressure sensor S; a pressure change detection circuit 47b for detecting a pressure change based on the signal from the pressure sensor S; and a switching circuit 47c for switching the output destination of the signal from the pressure sensor S between the usual pressure detection circuit 47a and the pressure change detection circuit 47b. When a pressure change is not detected by the pressure change detection circuit 47b, the switching circuit 47c adopts the pressure change detection circuit 47b as the output destination, and when a pressure change is detected by the pressure change detection circuit 47b, the switching circuit switches the output destination to the usual pressure detection circuit 47a. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pressure detection unit and a gas meter.

  2. Description of the Related Art Conventionally, a pressure sensor that processes a semiconductor substrate to form a thin film diaphragm and outputs a pressure signal corresponding to the amount of diaphragm displacement that changes when pressure is applied is known. In this pressure sensor, a piezoresistor is formed on the diaphragm, and a pressure signal based on the resistance value of the piezoresistor that changes due to the displacement of the diaphragm is output (for example, see Patent Document 1).

JP 2008-82969 A

  The present applicant has invented the technique of Japanese Patent Application No. 2009-130463. In the present invention, a trigger generator is provided in the gas flow path. This trigger generating device has a diaphragm, and when the pressure change occurs, the diaphragm is changed so that the movable contact on the diaphragm comes into contact with the fixed contact provided in a fixed manner to detect the pressure change. Yes. Then, a trigger signal generated when the movable contact and the fixed contact come into contact with each other can be input to a microcomputer and the pressure sensor can be driven by the microcomputer to start pressure measurement.

  However, in the case of the technique of Japanese Patent Application No. 2009-130463, it is a configuration that only detects pressure changes. For this reason, in order to detect pressure change and start pressure measurement, two pressure sensors and a trigger generation device are required, which is disadvantageous in terms of space. In this specification, a part of the technology of Japanese Patent Application No. 2009-130463 is described. However, this description does not recognize the publicity of the technology of Japanese Patent Application No. 2009-130463.

  The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a pressure detection unit and a gas meter capable of saving space.

  The pressure detection unit of the present invention includes a pressure sensor that operates by supplying a current from a power supply, a pressure detection unit that measures pressure based on a signal from the pressure sensor, and a pressure change based on a signal from the pressure sensor. Pressure change detection means for detecting; and switching means for switching between an input state in which a signal from the pressure sensor is input to the pressure detection means and a non-input state in which the signal is not input. The switching means includes the pressure change detection means. When the pressure change is not detected by the above, the non-input state is set, and when the pressure change is detected by the pressure change detecting means, the input state is switched.

  According to this pressure detection unit, the pressure detection means for measuring the pressure based on the signal from the pressure sensor, the pressure change detection means for detecting the pressure change based on the signal from the pressure sensor, and the signal from the pressure sensor. Switching means for switching between an input state to be input to the pressure detection means and a non-input state not to be input. When no pressure change is detected by the pressure change detection means, a non-input state is detected, and the pressure change is detected by the pressure change detection means. Switch to the input state. For this reason, when no pressure change is detected, the signal from the pressure sensor is not input to the pressure detection means but is input to the pressure change detection means to detect the pressure change. On the other hand, when there is a pressure change, a signal from the pressure sensor is input to the pressure detection means, and the pressure is measured. Thereby, a pressure change can be detected and pressure measurement can be started. In particular, pressure change detection and pressure measurement are performed based on a signal from a pressure sensor, and the pressure sensor function is shared. This eliminates the need for the pressure sensor and the trigger generator, and can realize the same function as the trigger generator using the signal of the pressure sensor. Accordingly, it is possible to provide a pressure detection unit capable of saving space.

  In the pressure detection unit of the present invention, a normal current supply path for supplying a normal current from the power supply to the pressure sensor in the input state, and a low current lower than a normal current from the power supply to the pressure sensor in the non-input state. A low current supply path for supplying a current, and the switching means includes the normal current supply path and the low current supply path according to whether the signal output destination is the pressure detection means or the pressure change detection means. Is preferably switched.

  According to this pressure detection unit, the low current supply path for supplying a low current lower than the normal current from the power source to the pressure sensor in the non-input state is provided. Here, gas is not always used in ordinary households, but rather, the time when it is not used is longer. For this reason, it can be said that the time when the gas is not used and the pressure change does not occur is long, and the current consumption can be suppressed by supplying the low current in the non-input state.

  In the pressure detection unit of the present invention, the low current supply path includes a current supply path connecting the power source and the pressure sensor, and a resistor provided on the current supply path, and the normal current The supply path preferably has a bypass path that bypasses the resistor and connects the power source and the pressure sensor.

  According to this pressure detection unit, the low current supply path has a current supply path connecting the power source and the pressure sensor, and a resistor provided on the current supply path, and the normal current supply path bypasses the resistor. Thus, a bypass path connecting the power source and the pressure sensor is provided. For this reason, when a low current is supplied, it is only necessary to supply a current via a resistor, and it is not necessary to provide a plurality of power supplies. Therefore, the configuration can be simplified.

  Further, in the pressure detection unit of the present invention, the switching unit is configured to switch the output destination of the signal from the pressure sensor between the pressure detection unit and the pressure change detection unit, and the pressure change detection unit detects the pressure by the pressure change detection unit. When no change is detected, the signal output destination is set to the non-input state as the pressure change detection means, and when a pressure change is detected by the pressure change detection means, the signal output destination is switched to the pressure detection means and the input state It is preferable that

  According to this pressure detection unit, when a pressure change is not detected, the signal output destination is set to the non-input state as the pressure change detection means, and when a pressure change is detected, the signal output destination is switched to the pressure detection means and the input state is set. To do. For this reason, when no pressure change is detected and there is no need for pressure detection, no signal from the pressure sensor is input to the pressure detection means. When pressure change is detected and pressure detection is required, a signal from the pressure sensor is input to the pressure detection means. Thus, the output destination of the signal from the pressure sensor can be matched to the situation.

  In the pressure detection unit of the present invention, it is preferable that the switching means return to the non-input state after a predetermined number of seconds have elapsed since switching to the input state.

  According to this pressure detection unit, the switching means returns to the non-input state after a predetermined number of seconds have elapsed after switching to the input state. For this reason, the signal output destination from the pressure sensor is returned to the pressure change detecting means after a predetermined number of seconds have elapsed since switching to the pressure detecting means. Therefore, after the pressure change is detected and the pressure measurement is performed, the pressure change is detected again after a predetermined number of seconds. For example, after detecting the pressure change due to the start of use of the first gas appliance, two pressure changes are detected. It is possible to detect a change in pressure due to the start of use of the eye gas appliance. Therefore, it is possible to appropriately detect a pressure change.

  In the pressure detection unit of the present invention, it is preferable that a signal from the pressure sensor is branched and one is input to the pressure change detection means and the other is input to the switching means.

  According to this pressure detection unit, the signal from the pressure sensor is branched, and one is input to the pressure change detection means and the other is input to the switching means. For this reason, a signal from the pressure sensor is always input to the pressure change detecting means. For example, after detecting a pressure change due to the start of use of the first gas appliance, the start of use of the second gas appliance is detected. A pressure change can be detected. Therefore, it is possible to appropriately detect a pressure change.

  Further, in the pressure detection unit of the present invention, the pressure change detecting means sets the amplification factor to a predetermined value in a state where no pressure change is detected, and detects the pressure change and the amplification factor when the switching means enters the input state. Is preferably smaller than the predetermined value.

  According to this pressure detection unit, the amplification factor is set to a predetermined value in a state where no pressure change is detected, and the amplification factor is set to a value smaller than the predetermined value when the pressure change is detected and the switching unit is in the input state. For this reason, in a state where no pressure change is detected, the amplification factor is increased, and it is possible to more clearly grasp that the pressure change has occurred.

  Moreover, the gas meter of the present invention is characterized by incorporating the above-described pressure detection unit.

  According to this gas meter, since the gas meter incorporates the pressure detection unit described above, a gas meter capable of saving space can be provided.

  According to the present invention, space saving can be achieved.

1 is a configuration diagram of a gas supply system including a gas meter according to an embodiment of the present invention. It is a block diagram which shows the detail of the gas meter shown in FIG. FIG. 3 is a configuration diagram showing the inside of μCOM shown in FIG. 2. It is a block diagram which shows the detail of the pressure detection unit shown in FIG. It is the schematic of the pressure sensor shown in FIG. 4, (a) shows the top view, (b) has shown sectional drawing. It is a state diagram explaining operation | movement to the pressure detection unit which concerns on this embodiment, (a) shows the example whose signal output destination is a pressure change detection circuit, (b) is a signal output destination is a normal pressure detection circuit. An example is shown. It is a block diagram which shows the detail of the pressure detection unit which concerns on 2nd Embodiment. It is a state diagram explaining operation | movement to the pressure detection unit which concerns on 2nd Embodiment, (a) shows the example whose signal output destination is a pressure change detection circuit, (b) is a signal output destination is a normal pressure detection circuit. An example is shown.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a gas supply system including a gas meter according to an embodiment of the present invention. The gas supply system 1 supplies fuel gas to each gas appliance 10, and includes a plurality of gas appliances 10, a gas supply source regulator 20, pipes 31 and 32, and a gas meter 40. .

  The adjuster 20 adjusts the fuel gas from the upstream to a predetermined pressure and flows it through the first pipe 31. The adjuster 20 has a configuration in which, for example, the fuel gas is adjusted to a pressure of about 2.9 kPa and flows through the first pipe 31. The first pipe 31 connects the regulator 20 and the gas meter 40. The second pipe 32 is a pipe that connects the gas meter 40 and the gas appliance 10. The gas meter 40 measures the flow rate of the fuel gas and displays the integrated flow rate. In such a gas supply system 1, a flow path connected to the first pipe 31 and the second pipe 32 is formed in the gas meter 40, and the fuel gas flowing through the regulator 20 flows from the first pipe 31 to the gas meter 40, And the gas appliance 10 is reached through the second pipe 32 and burned in the gas appliance 10.

  The gas appliance 10 is a gas combustion device such as a gas stove, a fan heater, a water heater, and a table stove. The gas appliance 10 includes those having a governor and those having no governor. In addition, the gas appliance 10 includes those that can be controlled by PID (Proportional Integral Derivative) and those that cannot.

  FIG. 2 is a configuration diagram showing details of the gas meter 40 shown in FIG. The gas meter 40 shown in FIG. 2 is an ultrasonic gas meter, and is disposed 2 opposite to each other so as to be separated by a distance L in the gas flow path and to form an angle θ with respect to the gas flow direction Y. There are two acoustic transducers TD1, TD2. In the example illustrated in FIG. 2, an ultrasonic gas meter is used as an example of the gas meter 40, but the gas meter 40 is not limited to the ultrasonic gas meter.

  The two acoustic transducers TD1, TD2 are composed of, for example, piezoelectric vibrators that operate at an ultrasonic frequency. The gas flow path is provided with a gas shut-off valve 46 that shuts off the gas flow path by closing the valve upstream of both acoustic transducers TD1 and TD2.

  Each transducer TD1, TD2 is connected to a transmission circuit 42 and a reception circuit 43 via transducer interface (I / F) circuits 41a, 41b, respectively. The transmission circuit 42 transmits, in the form of pulse bursts, a signal for driving one of the transducers TD1 and TD2 to generate an ultrasonic signal under the control of the microcomputer (μCOM) 44.

  The receiving circuit 43 incorporates an amplifier 43a that receives signals from the other transducers TD1 and TD2 that have received the ultrasonic signal that has passed through the gas flow path and amplifies the ultrasonic signal to a predetermined intensity. The amplification degree of the amplifier 43 a can be adjusted by the μCOM 44. Further, the display unit 45 is connected to the μCOM 44.

  Further, the gas meter 40 has a pressure detection unit 47 built therein. The pressure detection unit 47 detects the pressure in the gas flow path and transmits a signal corresponding to the pressure value to the μCOM 44.

  FIG. 3 is a block diagram showing the inside of the μCOM 44 shown in FIG. As shown in FIG. 3, the μCOM 44 includes a central processing unit (CPU) 44a that performs various processes according to a program, a ROM 44b that is a read-only memory that stores a program for processing performed by the CPU 44a, and various types of CPU 44a. A RAM 44c, which is a readable / writable memory having a work area used in the processing process and a data storage area for storing various data, is incorporated. These are connected to each other by a bus line 44d.

  Further, the CPU 44a has a measurement function of measuring the gas flow rate at every sampling time using the two transducers TD1 and TD2, and multiplying the measured gas flow rate by the cross-sectional area of the gas flow path to measure the instantaneous flow rate. . Further, based on the pressure value detected by the pressure detection unit 47, the CPU 44a determines whether the gas instrument 10 being used is a gas instrument with a governor, a gas instrument without a governor 10, or a gas instrument with a PID control function. Or a gas leaking determination function. In addition, the CPU 44 a also has a gas appliance discriminating function for discriminating the type (for example, a fan heater or a gas stove) of the gas appliance 10 being used based on the pressure value detected by the pressure detection unit 47. The determination function and the gas appliance determination function perform determination and determination based on the vibration waveform of the gas pressure within a few seconds immediately after the start of gas use or immediately after the occurrence of gas leakage. At this time, these functions perform determination and discrimination by capturing characteristics of the vibration waveform or performing matching using Fourier transform.

  FIG. 4 is a block diagram showing details of the pressure detection unit 47 shown in FIG. As shown in FIG. 4, the pressure detection unit 47 includes a pressure sensor S, a normal pressure detection circuit (pressure detection means) 47a, a pressure change detection circuit (pressure change detection means) 47b, and a switching circuit (switching means) 47c. And.

  The pressure sensor S operates by supplying current from a power source, and transmits a signal corresponding to the pressure in the flow path. FIG. 5 is a schematic diagram of the pressure sensor S shown in FIG. 4, (a) shows a top view, and (b) shows a cross-sectional view. As shown in FIGS. 5 (a) and 5 (b), the pressure sensor S is a detection element that detects the bending of the diaphragm D caused by the pressure of the external fluid and the thin-walled diaphragm D that is provided to be flexible. First to fourth piezoresistors R1 to R4. These piezoresistors R1 to R4 change in resistance value due to the deflection of the diaphragm D that occurs when the gas pressure in the flow path changes. For example, when the diaphragm D is not bent, the resistance value is about 1 kΩ. It is what has.

  Further, as shown in FIG. 5A, the second and fourth piezoresistors R2 and R4 are located on the center side of the diaphragm D with respect to the first and third piezoresistors R1 and R3. For this reason, the amount of change in the resistance values of the second and fourth piezoresistors R2 and R4 caused by the deflection of the diaphragm D is different from the amount of change in the resistance values of the first and third piezoresistors R1 and R3.

  Reference is again made to FIG. As shown in FIG. 5, in the pressure sensor S, the first and fourth piezoresistors R1 and R4 and the second and third piezoresistors R2 and R3 are connected in parallel with a connection point A on the power supply side as a branch point. . Specifically, the first piezoresistor R1 has one end connected to the connection point A and the other end connected to one end of the fourth piezoresistor R4. The other end of the fourth piezoresistor R4 is grounded via a connection point D. Similarly, the second piezoresistor R1 has one end connected to the connection point A and the other end connected to one end of the third piezoresistor R3. The other end of the third piezoresistor R3 is grounded via a connection point D.

  A connection point B between the first and fourth piezoresistors R1 and R4 and a connection point C between the second and third piezoresistors R2 and R3 are connected to a normal pressure detection circuit 47a and a pressure change detection circuit 47b via a switching circuit 47c. Connected to the side. For this reason, the normal pressure detection circuit 47a and the pressure change detection circuit 47b receive the divided voltage values of the first and fourth piezo resistors R1 and R4 and the divided voltage values of the second and third piezo resistors R2 and R3. It becomes.

  The normal pressure detection circuit 47a measures pressure based on a signal from the pressure sensor S. That is, the normal pressure detection circuit 47a measures the pressure from the partial pressure values at the connection points B and C. As described above, the amount of change in the resistance values of the second and fourth piezoresistors R2 and R4 caused by the deflection of the diaphragm D is different from the amount of change in the resistance values of the first and third piezoresistors R1 and R3. For this reason, the partial pressure values at the connection points B and C differ depending on the applied pressure, and the normal pressure detection circuit 47a calculates the pressure from the partial pressure value. In addition, the normal pressure detection circuit 47 a transmits a signal corresponding to the measured pressure to the μCOM 44 after measuring the pressure.

  In this embodiment, the pressure sensor S is exemplified as a piezoresistive pressure sensor. However, the pressure sensor S is not limited to this, and may be a pressure sensor using carbon nanotubes, or a capacitance pressure sensor. There may be.

  The pressure change detection circuit 47b detects a pressure change based on a signal from the pressure sensor S. That is, the pressure change detection circuit 47b detects a pressure change from the partial pressure values at the connection points B and C. The pressure change detection circuit 47b is composed of, for example, a differential circuit, an amplifier, and the like, and outputs a trigger signal indicating a pressure change when the pressure changes. Note that the pressure change detection circuit 47b is not limited to a differentiation circuit or an amplifier, but may have other circuit configurations such as an integration circuit or a differential amplifier circuit.

  The switching circuit 47c switches between an input state in which a signal from the pressure sensor S is input to the normal pressure detection circuit 47a and a non-input state in which the signal is not input. Specifically, the switching circuit 47c is configured to switch the output destination of the signal from the pressure sensor S between the normal pressure detection circuit 47a and the pressure change detection circuit 47b, and the first to fifth contacts P1 to P5, the first First to third switches SW1 to SW3 are provided.

  When the signal output destination is the pressure change detection circuit 47b, the switching circuit 47c connects the first switch SW1 to the first contact P1 and connects the second switch SW2 to the third contact P3. As a result, the partial pressure values at the connection points B and C are input to the pressure change detection circuit 47b, and the non-input state is established. Further, when the signal output destination is the normal pressure detection circuit 47a, the switching circuit 47c connects the first switch SW1 to the second contact P2 and connects the second switch SW2 to the fourth contact P4. As a result, the partial pressure values at the connection points B and C are input to the normal pressure detection circuit 47a to enter the input state.

  The normal pressure detection circuit 47a, the pressure change detection circuit 47b, and the switching circuit 47c are preferably configured by analog circuits (including switching ICs). This is because if these are constituted by a microcomputer, power consumption by the microcomputer occurs, and the power consumption becomes large.

  Furthermore, the pressure sensor S has a normal current supply path 47d and a low current supply path 47e. The normal current supply path 47d is a path for supplying a normal current to the pressure sensor S when the signal output destination is the normal pressure detection circuit 47a. The low current supply path 47e is a path for supplying a low current lower than the normal current to the pressure sensor S when the signal output destination is the pressure change detection circuit 47b.

  More specifically, the low current supply path 47e includes a current supply path L1 that connects the power source and the connection point A of the pressure sensor S, and a resistor Rz that is provided on the current supply path L1. In this path 47e, a low current is supplied to the pressure sensor S by supplying the current from the power source to the pressure sensor S via the resistor Rz. The normal current supply path 47d has a bypass path L2 that bypasses the resistor Rz and connects the power source and the connection point A of the pressure sensor S. In this path 47d, the normal current is supplied to the pressure sensor S by supplying the current from the power source to the pressure sensor S without passing through the resistor Rz.

  The normal current supply path 47d is connected to the pressure sensor S via the switching circuit 47c, and includes a third switch SW3 and a fifth contact P5. The normal current supply path 47d supplies the normal current to the pressure sensor S when the third switch SW3 is connected to the fifth contact P5.

  Next, the operation of the pressure detection unit 47 according to this embodiment will be described with reference to FIG. FIG. 6 is a state diagram for explaining the operation of the pressure detection unit 47 according to the present embodiment, in which (a) shows an example in which the signal output destination is the pressure change detection circuit 47b, and (b) shows the signal output destination. An example of the normal pressure detection circuit 47a is shown.

  First, when there is no gas leakage and no gas is used, that is, when no pressure change is detected, the switching circuit 47c detects the signal output destination as a pressure change as shown in FIG. The circuit 47b is used. Therefore, the first switch SW1 is connected to the first contact P1, the second switch SW2 is connected to the third contact P3, and the normal pressure detection circuit 47a is in a non-input state.

  When no pressure change is detected, the third switch SW3 is not connected to the contact P5, and the current from the power source is supplied to the pressure sensor S through the low current supply path 47e. That is, a low current is supplied to the pressure sensor S. Thus, in this embodiment, when there is no pressure change, a low current is supplied to the pressure sensor S. Here, gas is not always used in homes and the like, but rather, the time when it is not used is longer. For this reason, it can be said that the time during which no gas is used (including gas leakage) and no pressure change occurs is long, and the current consumption is suppressed by supplying a low current to the pressure sensor S.

  In the present embodiment, the low current is, for example, about 1 μA. For this reason, the pressure sensor S is driven with a current of about 1 μA, and is easily affected by noise. Therefore, it can be said that the pressure sensor S and the group including the switching circuit 47c and the pressure change detection circuit 47b are desirably arranged close to each other. This is because the influence of noise can be reduced.

  Next, when a gas leak occurs or when a gas is used, that is, when a pressure change occurs, the diaphragm D of the pressure sensor S bends. As a result, the resistance values of the first to fourth piezoresistors R1 to R4 change. Specifically, the resistance value R1 of the first piezoresistor R1 changes to R11. Similarly, the resistance value R2 of the second piezoresistor R2 changes to R2 ', the resistance value R3 of the third piezoresistor R3 changes to R31, and the resistance value R4 of the fourth piezoresistor R4 changes to R4'. The pressure change detection circuit 47b recognizes the change in the resistance value from the change in the partial pressure value at the connection points B and C, and detects the pressure change.

  The pressure change detection circuit 47b outputs a trigger signal when detecting a pressure change. Then, the trigger signal is input to the switching circuit 47c. When the trigger signal is input, the switching circuit 47c activates the third switch SW3 and connects the third switch SW3 and the fifth contact P5. As a result, the current from the power source is supplied to the pressure sensor S via the normal current supply path 47d.

  Furthermore, when the trigger signal is input, the switching circuit 47c operates the first and second switches SW1 and SW2, connects the first switch SW1 and the second contact P2, and also connects the second switch SW2 and the fourth contact P4. And connect. Thereby, the signal output destination of the pressure sensor S is switched to the normal pressure detection circuit 47a. That is, the normal pressure detection circuit 47a is switched to the input state. Then, the normal pressure detection circuit 47a measures the pressure based on the signal from the pressure sensor S.

  Next, it is assumed that a predetermined number of seconds (for example, 1 second) has elapsed since the signal output destination of the pressure sensor S was switched from the pressure change detection circuit 47b to the normal pressure detection circuit 47a. At this time, the switching circuit 47c operates the first and second switches SW1 and SW2, connects the first switch SW1 and the first contact P1, and connects the second switch SW2 and the third contact P3. As a result, the signal output destination of the pressure sensor S is switched to the pressure change detection circuit 47b, and the normal pressure detection circuit 47a returns to the non-input state.

  Further, the switching circuit 47c operates the third switch SW3 to release the connection relationship between the third switch SW3 and the fifth contact P5. As a result, the current from the power source is supplied to the pressure sensor S through the low current supply path 47e. That is, the initial state is restored.

  Thus, according to the pressure detection unit 47 according to the present embodiment, the normal pressure detection circuit 47a that measures the pressure based on the signal from the pressure sensor S, and the pressure change based on the signal from the pressure sensor S. A pressure change detection circuit 47b for detecting, and a switching circuit 47c for switching between an input state in which a signal from the pressure sensor S is input to the normal pressure detection circuit 47a and a non-input state in which the signal is not input is provided. When no change is detected, a non-input state is set, and when a pressure change is detected by the pressure change detection circuit 47b, the input state is switched. Therefore, when no pressure change is detected, the signal from the pressure sensor S is not input to the normal pressure detection circuit 47a but is input to the pressure change detection circuit 47b to detect the pressure change. On the other hand, when there is a pressure change, the signal from the pressure sensor S is normally input to the pressure detection circuit 47a, and the pressure is measured. Thereby, a pressure change can be detected and pressure measurement can be started. In particular, pressure change detection and pressure measurement are performed based on a signal from the pressure sensor S, and the pressure sensor function is shared. This eliminates the need for the pressure sensor and the trigger generating device, and the function similar to that of the trigger generating device can be realized using the signal of the pressure sensor S. Therefore, it is possible to provide the pressure detection unit 47 capable of saving space.

  More specifically, when the pressure sensor of Patent Document 1 and the trigger generation device of Japanese Patent Application No. 2009-130463 are simply combined, two diaphragms are required: a pressure sensor diaphragm and a trigger generation device diaphragm. In this embodiment, a single diaphragm D can detect a pressure change and measure a pressure, thereby saving space.

  In addition, a low current supply path 47e that supplies a low current lower than the normal current from the power source to the pressure sensor S in a non-input state is provided. Here, gas is not always used in ordinary households, but rather, the time when it is not used is longer. For this reason, it can be said that the time when the gas is not used and the pressure change does not occur is long, and the current consumption can be suppressed by supplying the low current in the non-input state.

  The low current supply path 47e has a current supply path L1 that connects the power source and the pressure sensor S, and a resistor Rz provided on the current supply path L1, and the normal current supply path 47d has a resistance Rz. A bypass path L2 that bypasses and connects the power source and the pressure sensor S is provided. For this reason, when a low current is supplied, it is only necessary to supply a current through the resistor Rz, and it is not necessary to provide a plurality of power sources. Therefore, the configuration can be simplified.

  When no pressure change is detected, the signal output destination is set to the non-input state as the pressure change detection circuit 47b. When a pressure change is detected, the signal output destination is switched to the normal pressure detection circuit 47a to enter the input state. For this reason, when no pressure change is detected and pressure detection is not necessary, the signal from the pressure sensor S is not input to the normal pressure detection circuit 47a. When pressure change is detected and pressure detection is required, a signal from the pressure sensor S is input to the normal pressure detection circuit 47a. Thus, the output destination of the signal from the pressure sensor S can be matched with the situation.

  The switching circuit 47c returns to the non-input state after a predetermined number of seconds have elapsed since switching to the input state. For this reason, after the pressure change is detected and the pressure measurement is performed, the pressure change is detected again after a predetermined number of seconds. For example, after detecting the pressure change due to the start of use of the first gas appliance, It is possible to detect a pressure change due to the start of use of the first gas appliance. Therefore, it is possible to appropriately detect a pressure change.

  In particular, as in the technology of Japanese Patent Application No. 2009-071233 invented by the present applicant, when determining the use of the gas appliance 10 based on the pressure waveform within a few seconds from the time of the pressure change, the pressure for a predetermined number of seconds. Measurement is sufficient, and pressure change detection and pressure measurement can be performed more appropriately.

  Furthermore, according to the gas meter 40 according to the present embodiment, since the pressure detection unit 47 is built in, the gas meter 40 capable of saving space can be provided. In particular, since the pressure detection unit 47 is designed to save space, it is easy to incorporate in the gas meter 40 and is advantageous in design and the like.

  Next, a second embodiment of the present invention will be described. The pressure detection unit 47 according to the second embodiment is the same as that of the first embodiment, but the configuration is partially different. Only differences from the first embodiment will be described below.

  FIG. 7 is a configuration diagram showing details of the pressure detection unit according to the second embodiment. As shown in FIG. 7, the pressure detection unit 47 includes branch points E and F that branch the signal from the pressure sensor S. One of the signals from the pressure sensor S is input to the pressure change detection circuit 47b via the branch points E and F, and the other is input to the switching circuit 47c. For this reason, in the second embodiment, a signal from the pressure sensor S is always input to the pressure change detection circuit 47b.

  Furthermore, in the second embodiment, the switching circuit 47c does not have the first contact P1 and the third contact P3. Specifically, the switching circuit 47c includes first to third switches SW1 to SW3, and includes second and fourth contacts P2 and P4 connected to the normal pressure detection circuit 47a, and a normal current supply path 47d. And a fifth contact to be formed.

  Furthermore, in the second embodiment, the pressure change detection circuit 47b can adjust the amplification factor. Specifically, the pressure change detection circuit 47b sets the amplification factor to a predetermined value in a state where no pressure change is detected, that is, a non-input state, and when the pressure change is detected and the switching circuit 47c enters the input state. Is set to a smaller value.

  Next, the operation of the pressure detection unit 47 according to the second embodiment will be described with reference to FIG. FIG. 8 is a state diagram for explaining the operation of the pressure detection unit 47 according to the second embodiment, in which (a) shows an example in which the signal output destination is the pressure change detection circuit 47b, and (b) shows the signal output destination. Shows an example in which is a normal pressure detection circuit 47a.

  First, when no gas leak occurs and no gas is used, that is, when no pressure change is detected, the switching circuit 47c is in a non-input state as shown in FIG. . For this reason, the first switch SW1 is not connected to the second contact P2, and the second switch SW2 is not connected to the fourth contact P4.

  When no pressure change is detected, the third switch SW3 is not connected to the contact P5, and the current from the power source is supplied to the pressure sensor S through the low current supply path 47e. That is, a low current is supplied to the pressure sensor S. In this case, the pressure change detection circuit 47b sets the amplification factor to a predetermined value so that the pressure change can be accurately captured even by a small signal from the pressure sensor S.

  Next, when a gas leak occurs or when a gas is used, that is, when a pressure change occurs, the diaphragm D of the pressure sensor S bends. As a result, the resistance values of the first to fourth piezoresistors R1 to R4 change. Specifically, the resistance value R1 of the first piezoresistor R1 changes to R11. Similarly, the resistance value R2 of the second piezoresistor R2 changes to R2 ', the resistance value R3 of the third piezoresistor R3 changes to R31, and the resistance value R4 of the fourth piezoresistor R4 changes to R4'. The pressure change detection circuit 47b recognizes the change in the resistance value from the change in the partial pressure value at the connection points B and C, and detects the pressure change.

  The pressure change detection circuit 47b outputs a trigger signal when detecting a pressure change. Then, the trigger signal is input to the switching circuit 47c. When the trigger signal is input, the switching circuit 47c activates the third switch SW3 and connects the third switch SW3 and the fifth contact P5. As a result, the current from the power source is supplied to the pressure sensor S via the normal current supply path 47d.

  Furthermore, when the trigger signal is input, the switching circuit 47c operates the first and second switches SW1 and SW2, connects the first switch SW1 and the second contact P2, and also connects the second switch SW2 and the fourth contact P4. And connect. Thereby, the signal output destination of the pressure sensor S is switched to the normal pressure detection circuit 47a. That is, the normal pressure detection circuit 47a is switched to the input state. Then, the normal pressure detection circuit 47a measures the pressure based on the signal from the pressure sensor S.

  In this case, the pressure change detection circuit 47b sets the amplification factor to a value smaller than a predetermined value. That is, since a normal current flows through the pressure sensor S via the normal current supply path 47d, the signal from the pressure sensor S is relatively large, and even if the amplification factor is lowered, a pressure change can be detected without any problem. The circuit 47b sets the amplification factor to a value smaller than a predetermined value.

  Next, it is assumed that a predetermined number of seconds (for example, 1 second) has elapsed since the signal output destination of the pressure sensor S was switched from the pressure change detection circuit 47b to the normal pressure detection circuit 47a. At this time, the switching circuit 47c activates the first and second switches SW1 and SW2, the connection relationship between the first switch SW1 and the second contact P2 is released, and the second switch SW2 and the fourth contact P4. The connection relationship of is released. As a result, the normal pressure detection circuit 47a returns to the non-input state.

  Further, the switching circuit 47c operates the third switch SW3 to release the connection relationship between the third switch SW3 and the fifth contact P5. As a result, the current from the power source is supplied to the pressure sensor S through the low current supply path 47e. That is, the initial state is restored.

  As described above, according to the pressure detection unit 47 according to the second embodiment, it is possible to provide the pressure detection unit 47 capable of saving space as in the first embodiment. In addition, current consumption can be suppressed and the configuration can be simplified.

  Furthermore, according to the second embodiment, the signal from the pressure sensor S is branched, and one is input to the pressure change detection circuit 47b and the other is input to the switching circuit 47c. For this reason, a signal from the pressure sensor S is always input to the pressure change detection circuit 47b. For example, after the pressure change due to the start of use of the first gas appliance is detected, the use of the second gas appliance is used. A pressure change due to the start can be detected. Therefore, it is possible to appropriately detect a pressure change.

  Further, the amplification factor is set to a predetermined value in a state where no pressure change is detected, and the amplification factor is set to a value smaller than the predetermined value when the pressure change is detected and the switching circuit 47c is in the input state. For this reason, in a state where no pressure change is detected, the amplification factor is increased, and it is possible to more clearly grasp that the pressure change has occurred.

  In particular, when a low current is supplied to the pressure sensor S in a non-input state, the signal from the pressure sensor S is also small, so that the pressure change is captured based on a small signal by setting the amplification degree to a predetermined value. Can do. In addition, when the normal current is supplied to the pressure sensor S in the input state, the signal from the pressure sensor S is large to some extent, so that it is possible to capture the pressure change without any problem even if the amplification degree is smaller than a predetermined value. Can do.

  Furthermore, according to the gas meter 40 which concerns on 2nd Embodiment, the gas meter 40 which can aim at space saving can be provided similarly to 1st Embodiment.

  As described above, the present invention has been described based on the embodiment, but the present invention is not limited to the above embodiment, and may be modified without departing from the gist of the present invention.

  For example, in the present embodiment, the pressure detection unit 47 exists as an internal configuration of the gas meter 40, but not limited to this, the pressure detection unit 47 is taken out from the gas meter 40 and arranged in the first pipe 31 and the second pipe 32. May be. In this case, in addition to the pressure detection unit 47, it is desirable to integrate the function of determining gas leakage based on the pressure value measured by the pressure detection unit 47 and arrange the functions in the first and second pipes 31 and 32. This is because it is possible to determine a gas leak upstream or downstream of the gas meter 40. In particular, when arranged in the first and second pipes 31 and 32, it is desirable to configure the normal pressure detection circuit 47a, the pressure change detection circuit 47b, and the switching circuit 47c with a microcomputer. This is because space can be saved by incorporating the function of determining gas leakage and the circuits 47a to 47c in the microcomputer.

  Further, in the present embodiment, the case where the pressure change detection circuit 47b does not detect a pressure change indicates that there is no change in the gas flow rate, and thus it can be said that there is little need for flow rate measurement. Therefore, the trigger signal from the pressure change detection circuit 47b is configured to be output to the μCOM 44, the flow rate is measured in detail when the trigger signal is input, and the flow rate measurement interval is usually once every 2 seconds when the trigger signal is not input. For example, once every 10 seconds. This is because current consumption can be further reduced.

  Further, in the present embodiment, the pressure detection unit 47 measures the pressure value by the normal pressure detection circuit 47a. However, the pressure detection unit 47 is not limited to this, and the function of the normal pressure detection circuit 47a may be provided in the μCOM 44. .

DESCRIPTION OF SYMBOLS 1 ... Gas supply system 10 ... Gas appliance 20 ... Regulator 31 ... 1st piping 32 ... 2nd piping 40 ... Gas meter (pressure detection unit)
41a, 41b ... Transducer I / F circuit 42 ... Transmission circuit 43 ... Reception circuit 43a ... Amplifier 44 ... μCOM
44a ... CPU
44b ... ROM
44c ... RAM
44d ... Bus line 45 ... Display 46 ... Gas shutoff valve 47 ... Pressure detection unit 47a ... Normal pressure detection circuit (pressure detection means)
47b ... Pressure change detection circuit (pressure change detection means)
47c ... switching circuit (switching means)
47d ... Normal current supply path 47e ... Low current supply paths A to D ... Connection points E, F ... Branch point L1 ... Current supply path L2 ... Bypass paths P1-P5 ... Contacts R1-R4 ... Piezoresistors Rz ... Resistance S ... Pressure Sensors SW1 to SW3 ... Switches TD1, TD2 ... Acoustic transducer

Claims (8)

A pressure sensor that operates by supplying current from the power supply;
Pressure detecting means for measuring pressure based on a signal from the pressure sensor;
Pressure change detecting means for detecting a pressure change based on a signal from the pressure sensor;
Switching means for switching between an input state in which a signal from the pressure sensor is input to the pressure detection unit and a non-input state in which the signal is not input;
The pressure detecting unit, wherein the switching means is set to a non-input state when no pressure change is detected by the pressure change detecting means, and is switched to an input state when a pressure change is detected by the pressure change detecting means. A normal current supply path for supplying a normal current from the power source to the pressure sensor in the input state;
A low current supply path for supplying a low current lower than a normal current from the power source to the pressure sensor in the non-input state;
The pressure detection unit according to claim 1, further comprising: The low current supply path has a current supply path that connects the power source and the pressure sensor, and a resistor provided on the current supply path,
The pressure detection unit according to claim 2, wherein the normal current supply path includes a bypass path that bypasses the resistor and connects the power source and the pressure sensor. The switching means is configured to switch the output destination of the signal from the pressure sensor between the pressure detecting means and the pressure change detecting means, and when the pressure change is not detected by the pressure change detecting means, the signal output destination is selected. 2. The non-input state as the pressure change detection means, and when a pressure change is detected by the pressure change detection means, a signal output destination is switched to the pressure detection means to enter the input state. The pressure detection unit according to claim 3. The pressure detection unit according to claim 4, wherein the switching unit returns to the non-input state after a predetermined number of seconds have elapsed since switching to the input state. 4. The signal according to claim 1, wherein a signal from the pressure sensor is branched and one of the signals is input to the pressure change detection unit and the other is input to the switching unit. 5. Pressure detection unit. The pressure change detection means sets the amplification factor to a predetermined value when no pressure change is detected, and sets the amplification factor to a value smaller than the predetermined value when the pressure change is detected and the switching means enters the input state. The pressure detection unit according to claim 6. A gas meter comprising the pressure detection unit according to any one of claims 1 to 7.

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