Measuring device for physical quantities

Abstract

Measuring device for physical quantities, comprising: a flow sensor that outputs a signal corresponding to a flow rate of a gas, and a signal processing unit that processes an output signal of the flow sensor, wherein the signal processing unit includes a buffer that stores the flow rate data of the gas based on the output signal for a predetermined period, an offset setting unit that sets a zero point of a flow rate waveform based on the flow rate data stored in the buffer, a gain calculation unit that calculates a correction gain by which the flow rate waveform whose zero point has been adjusted is multiplied, a correction calculation unit that performs a correction by multiplying the flow rate waveform whose zero point has been adjusted by the correction gain, and a frequency analysis unit that performs a frequency analysis calculation of the corrected flow rate waveform and stores the data obtained by the calculation in the buffer, wherein the gain calculation unit calculates the correction gain that does not cause overflow in the frequency analysis unit.

Description

Technical area

[0001] The present disclosure relates to a measuring device for physical quantities. Technical background

[0002] To date, inventions related to a waveform measurement method and a flow rate calculation method of an electronic device that measures a waveform output from a frequency output type air flow sensor and calculates a flow rate have been known (see PTL 1 below). The invention described in Patent Citation 1 aims to reduce a flow rate detection error due to a nonlinear relationship between a response delay, a cycle, and a flow rate in a transition region (see Section 0007 and the like in PTL 1).

[0003] To achieve this object, the invention described in PTL 1 calculates an average cycle of all waveforms within a predetermined time interval with respect to a frequency output signal of the air flow sensor, and performs conversion into a flow rate based on the average cycle. This reduces the flow rate detection error due to the influence of aliasing, and further reduces the response log by performing differential correction in the transition region. In addition, instead of calculating the flow rate by converting the average cycle into the flow rate, after calculating the average cycle, an air flow sensor signal is converted into the flow rate for each cycle, and an averaging process is performed in units of the flow rate.This reduces the flow rate detection error due to the nonlinearity of the cycle and flow rate (see section 0008 and the like in PTL 1).

[0004] According to the invention described in PTL 1, it is possible to reduce the flow rate detection error due to aliasing even during intake pulsation at all frequencies, obtaining the flow rate based on the average value of all output waveforms within the specified time interval. Because intake pulsation is a phenomenon caused by the vertical movement of a piston and the resonance of an intake pipe, there is no need to design the intake pipe to avoid a specific frequency for fear of aliasing. At the same time, this means that it is possible to freely set an air flow rate calculation cycle separate from the intake pulsation cycle (see section 0009 and the like in PTL 1). List of citationsPatent literature

[0005] PTL 1: JP 2011-052964 A Summary of the inventionTechnical problem

[0006] In the conventional technique, a process of calculating the average cycle of all waveforms within the specified time interval is carried out uniformly, regardless of the increase or decrease in the air flow rate, and then converting the flow rate based on the average cycle. Under certain conditions, such as when the uniform process is carried out, the frequency analysis error of the air flow rate may increase if the amplitude of the air flow rate is small.

[0007] The present disclosure provides a physical quantity measuring device that can reduce a frequency analysis error of a gas flow rate compared to the prior art. Solution to the problem

[0008] According to one aspect of the present disclosure, a physical quantity measuring device is provided, including a flow rate sensor that outputs a signal corresponding to a flow rate of a gas, and a signal processing unit that processes an output signal of the flow rate sensor, wherein the signal processing unit includes a buffer that stores the flow rate data of the gas based on the output signal for a predetermined period, an offset setting unit that sets a zero point of a flow rate waveform based on the flow rate data stored in the buffer, a gain calculation unit that calculates a correction gain by which the flow rate waveform whose zero point has been adjusted is multiplied, a correction calculation unit that performs a correction by multiplying the flow rate waveform whose zero point has been adjusted,with the correction gain, and a frequency analysis unit that performs a frequency analysis calculation of the corrected flow rate waveform and stores the data obtained by the calculation in the buffer, wherein the gain calculation unit calculates the correction gain that does not cause an overflow in the frequency analysis unit. Advantageous effects of the invention

[0009] According to one aspect of the present disclosure, it is possible to provide a physical quantity measuring device that can reduce the frequency analysis error of the gas flow rate. Brief description of the drawings Fig. 1 is a system diagram illustrating an example of a control system of an electronic fuel injection type internal combustion engine. Fig. 2 is a block diagram of the measuring device for physical quantities used in the Fig. 1 illustrated internal combustion engine control system. Fig. 3 is a front view of the physical quantity measuring device used in the Fig. 1 illustrated internal combustion engine control system. Fig. 4 is a front view of the Fig. 3 illustrated measuring device for physical quantities without a cover. Fig. 5 is a block diagram illustrating a configuration of a portion of the physical quantity measuring apparatus according to a first embodiment. Fig. 6 is a graphical representation showing a process by a signal processing unit of the Fig. 5 illustrates the measuring device for physical quantities. Fig. 7 is a block diagram illustrating a configuration of a portion of the physical quantity measuring apparatus according to a second embodiment. Fig. Fig. 8 is a diagram for describing an example of a process by a signal processing unit of the Fig. 7 illustrated measuring device for physical quantities. Fig. 9 is a diagram for describing an example of a process by a signal processing unit of the Fig. 7 illustrated measuring device for physical quantities. Fig. 10 is a block diagram illustrating a configuration of a portion of the physical quantity measuring apparatus according to a third embodiment. Description of the embodiments

[0010] Hereinafter, embodiments of a physical quantity measuring device according to the present disclosure will be described with reference to the drawings. (First embodiment)

[0011] Fig. 1 is a system diagram of a control system 1 of an electronic fuel injection type internal combustion engine using a physical quantity measuring device 20 according to a first embodiment of the present disclosure.

[0012] In the internal combustion engine control system 1, intake air is drawn from an air cleaner 21 as a measurement gas 2 based on an operation of an internal combustion engine 10 including an engine cylinder 11 and an engine piston 12. The intake air is introduced into a combustion chamber of the engine cylinder 11 via an intake body consisting of a main passage 22, a throttle body 23, and an intake manifold 24. A physical quantity of the measurement gas 2, which is the intake air introduced into the combustion chamber, is measured by the physical quantity measuring device 20. Further, fuel is supplied from a fuel injection valve 14 based on the physical quantity measured by the physical quantity measuring device 20 and introduced into the combustion chamber together with the intake air in a state of air-fuel mixture.

[0013] It is noted that, in the present embodiment, the fuel injection valve 14 is provided in an intake port of the internal combustion engine 10, the fuel injected into the intake port is mixed with the intake air, and the air-fuel mixture of the fuel and the intake air is introduced into the combustion chamber via the intake valve 15 and combusted to generate mechanical energy. The air-fuel mixture introduced into the combustion chamber is in the state where the fuel and air are mixed, and is explosively combusted by the spark ignition of a spark plug 13 to generate mechanical energy. The combusted gas is introduced into an exhaust pipe from an exhaust valve 16 and discharged as the exhaust gas 3 from the exhaust pipe to an outside of a vehicle.

[0014] The flow rate of the measurement gas 2, which is the intake air introduced into the combustion chamber, is controlled by a throttle valve 25, whose opening degree changes based on an operation of an accelerator pedal. In addition, a fuel supply amount is controlled based on the flow rate of the intake air introduced into the combustion chamber. By controlling the opening degree of the throttle valve 25 to control the flow rate of the intake air introduced into the combustion chamber, the mechanical energy generated by the internal combustion engine 10 can be controlled.

[0015] The physical quantity measuring device 20 measures physical quantities such as the flow rate, temperature, humidity, and pressure of the measurement gas, which is the intake air captured by the air filter 21 and flowing through the main duct 22. The physical quantity measuring device 20 outputs an electrical signal corresponding to the physical quantity of the intake air. An output signal of the physical quantity measuring device 20 is input to a control device 4.

[0016] In addition, an output of a throttle angle sensor 26 for measuring the opening degree of the throttle valve 25 is input to the control device 4. Furthermore, an output of a rotation angle sensor 17 is input to the control device 4 to measure a position and state of the engine piston 12, the intake valve 15, or the exhaust valve 16 of the internal combustion engine 10, and a rotational speed of the internal combustion engine 10. An output of an oxygen sensor 28 is input to the control device 4 to measure a mixture ratio of the fuel quantity and the air quantity from the state of the exhaust gas 3.

[0017] The control device 4 calculates a fuel injection amount and ignition timing based on the physical quantity of intake air, which is the output of the physical quantity measuring device 20, and the rotational speed of the internal combustion engine 10, which is measured based on the output of the rotation angle sensor 17. Based on these calculation results, the amount of fuel supplied from the fuel injection valve 14 and the ignition timing at which ignition is performed by the spark plug 13 are controlled. The fuel supply amount or ignition timing is actually finely controlled based on a temperature measured by the physical quantity measuring device 20, a change state of the throttle angle, a change state of the engine speed, and an air-fuel ratio state measured by the oxygen sensor 28.Furthermore, in an idling operating state of the internal combustion engine 10, the control device 4 controls the amount of air bypassing the throttle valve 25 through an idling air control valve 27, thereby controlling the rotational speed of the internal combustion engine 10 in the idling operating state.

[0018] Either the fuel supply amount or the ignition timing, which is the main control variable of the internal combustion engine 10, is calculated using the output of the physical quantity measuring device 20 as the main parameter. Therefore, it is important to improve the measurement accuracy of the physical quantity measuring device 20, suppress change over time, and improve reliability in order to improve the control accuracy and reliability of the vehicle. In particular, in recent years, there has been a very high demand for vehicle fuel efficiency and a very high demand for exhaust gas purification. To meet these demands, it is extremely important to improve the measurement accuracy of the physical quantity of the intake air, which is the measurement gas 2 measured by the physical quantity measuring device 20.In addition, it is important that the measuring device 20 for physical quantities maintains a high level of reliability.

[0019] Vehicles equipped with the physical quantity measuring device 20 are used in environments where temperature or humidity changes are large. It is preferable that the physical quantity measuring device 20 further considers the response to temperature or humidity changes in the use environment and the response to dust, pollutants, or the like. Additionally, the physical quantity measuring device 20 is mounted on the intake pipe, which is affected by the heat generated by the internal combustion engine 10. For this reason, the heat generated by the internal combustion engine 10 is transferred to the physical quantity measuring device 20 via the intake pipe, which is the main passage 22.Because the physical quantity measuring device 20 measures the flow rate of the measurement gas by performing heat transfer with the measurement gas, it is important to suppress the influence of heat from the outside as much as possible.

[0020] As described below, the vehicle-mounted physical quantity measuring device 20 simply solves the problems described in the heading of the problem to be solved by the invention, while achieving the effects described in the heading of the effect of the invention. As described below, the physical quantity measuring device 20 fully considers the above-mentioned various problems, solving various problems, which is required as a product, and achieving various effects.

[0021] The specific problems to be solved by the physical quantity measuring device 20 or the specific effects to be achieved will be described in the description of the following embodiments.

[0022] Fig. 2 is a block diagram showing a configuration of the Fig. 1 illustrates the feature section of the physical quantity measuring device 20. Although the details will be described later, the physical quantity measuring device 20 of the present embodiment is characterized by the following configuration.

[0023] The physical quantity measuring device 20 includes a flow rate sensor 205 that outputs a signal corresponding to the flow rate of the measurement gas 2, and a signal processing unit 260 that processes an output signal of the flow rate sensor 205. The signal processing unit 260 includes a buffer 261, an offset adjustment unit 262, a gain calculation unit 263, a correction calculation unit 264, and a frequency analysis unit 265. The buffer 261 stores the flow rate data of the measurement gas 2 based on the output signal of the flow rate sensor 205 for a predetermined period. The offset adjustment unit 262 adjusts a zero point of a flow rate waveform based on the flow rate data stored in the buffer 261. The gain calculation unit 263 calculates a correction gain to be multiplied by the flow rate waveform whose zero point has been adjusted.The correction calculation unit 264 performs the correction by multiplying the correction gain by the flow rate waveform whose zero point has been adjusted. The frequency analysis unit 265 performs a frequency analysis calculation on the corrected flow rate waveform and stores the data obtained by the calculation in the buffer 261. Then, the gain calculation unit 263 calculates a gain at which the frequency analysis unit 265 does not cause overflow as the correction gain.

[0024] In the Fig. 2, the signal processing unit 260 further includes a flow rate measuring unit 266 and a pulsation correction unit 267. In the example shown in Fig. 2, the physical quantity measuring device 20 further includes a flow rate output unit 270. The flow rate measuring unit 270 includes, for example, a conversion table that records the relationship between the output signal of the flow rate sensor 205 and the flow rate of the measurement gas 2 and converts the output signal of the flow rate sensor 205 into the flow rate data of the measurement gas 2.

[0025] The pulsation correction unit 267 performs the pulsation correction of the flow rate waveform of the measurement gas 2 based on the flow rate data of the measurement gas 2 converted by the flow rate measuring unit 266 and the result of the frequency analysis by the frequency analysis unit 265, and outputs the corrected flow rate data of the measurement gas 2 to the flow rate output unit 270.

[0026] The flow rate output unit 270 outputs the flow rate data of the measurement gas 2 after the pulsation correction input from the signal processing unit 260 to the outside of the physical quantity measuring device 20 via an external terminal.

[0027] The following describes the configuration of the physical quantity measuring device 20 of the present embodiment with respect to the Fig. 3 and Fig. 4 described in detail. Fig. 3 is a front view of the Fig. 1 illustrated measuring device 20 for physical quantities. Fig. 4 is a front view of the measuring device 20 for physical quantities according to Fig. 3 without a cover 202. It is stated that in Fig. 4, an illustration of a sealing material sealing a circuit board 207 is omitted.

[0028] The physical quantity measuring device 20 is used by being inserted into the main channel 22 from a mounting hole provided in a through wall of the main channel 22. The physical quantity measuring device 20 includes a housing 201 and a cover 202 attached to the housing 201. The housing 201 is formed by injection molding a synthetic resin material, and the cover 202 is formed from a plate-like member made of a conductive material such as an aluminum alloy. The cover 202 is formed in the shape of a thin plate and has a wide, flat cooling surface.

[0029] The housing 201 has a flange 211 fixed to the inlet body which is the main channel 22, a connector 212 projecting from the flange 211 and exposed from the inlet body to the outside to make an electrical connection with an external device, and a measuring unit 213 extending to project from the flange 211 toward a center of the main channel 22.

[0030] The flange 211 has, for example, a substantially rectangular shape in a plan view with a predetermined plate thickness and has through holes provided at the corners. The flange 211 is screwed into a screw hole of the main channel 22, for example, by inserting a fastening screw into the through hole provided at the corner, and is thus fastened to the main channel 22.

[0031] The connector 212 has, for example, four external terminals and one correction terminal provided inside it. The external terminals are a terminal for outputting physical quantities, such as flow rate or temperature, which are the measurement results of the physical quantity measuring device 20, and a power supply terminal for supplying DC power to operate the physical quantity measuring device 20. The correction terminal is a terminal used to measure the manufactured physical quantity measuring device 20, obtain correction values ​​for each physical quantity measuring device 20, and store the correction values ​​in a memory within the physical quantity measuring device 20.

[0032] The measuring unit 213 has a thin and long shape extending from the flange 211 toward the center of the main channel 22, and has a wide front surface 221 and a rear surface, and an upstream end surface 223 and a downstream end surface 224, which are a pair of narrow side surfaces. The measuring unit 213 is inserted inward from the mounting hole provided in the main channel 22 and is fixed to the main channel 22 via the flange 211, for example, by bringing the flange 211 into contact with the main channel 22 and fixing the flange 211 to the main channel 22 with a screw.

[0033] The measuring unit 213, in a state where the physical quantity measuring device 20 is attached to the main channel 22, protrudes from an inner wall of the main channel 22 toward a central axis 22a of the main channel 22. Then, the front surface 221 and the back surface are arranged in parallel along the central axis 22a of the main channel 22, and among the narrow upstream end surface 223 and the downstream end surface 224 of the measuring unit 213, the upstream end surface 223 on one side of the measuring unit 213 is arranged in a lateral direction so as to face the upstream side of the main channel 22, and the downstream end surface 224 on the other side of the measuring unit 213 is arranged in the lateral direction so as to face the downstream side of the main channel 22.

[0034] The end face 221 of the measuring unit 213 is flat from the upstream end face 223 to the downstream end face 224 along the lateral direction. On the other hand, the back face of the measuring unit 213 has a corner on the downstream end face 224 side chamfered thereon, and is inclined in a direction gradually approaching the end face as it moves from an intermediate position in the lateral direction to the downstream end face 224. As a result, a cross-sectional shape of the measuring unit 213 is a so-called streamline. Therefore, the measurement gas 2 flowing from the upstream of the main channel 22 can be smoothly introduced downstream along the end face 221 and the back face of the measuring unit 213, whereby a fluid resistance of the measuring unit 213 against the measurement gas 2 can be reduced.

[0035] The measuring unit 213 has a bottom surface 226 on the upstream side of the main channel 22 and a bottom surface 227 on the downstream side of the main channel 22 in a state where one end in a protrusion direction is formed in a stepped shape, and the physical quantity measuring device 20 is attached to the main channel 22. In the measuring unit 213, the bottom surface 227 on the downstream side protrudes in the protrusion direction from the bottom surface 226 on the upstream side, and a stepped surface 228 connecting the bottom surface 226 on the upstream side and the bottom surface 227 on the downstream side is arranged to face the upstream side of the main channel 22.

[0036] Additionally, in the measuring unit 213, an inlet 231 for receiving a portion of the measurement gas 2, such as intake air, into a sub-channel in the measuring unit 213 is opened on the stepped surface 228 of a tip portion 213a located on a side opposite the flange 211 and protruding from the bottom surface 226 on the upstream side. Then, a first outlet 232 and a second outlet 233 for returning the measurement gas 2 received in the sub-channel in the measuring unit 213 to the main channel 22 are opened in the downstream end surface 224 of the tip portion 213a of the measuring unit 213.

[0037] That is, the measuring unit 213 has an upstream end surface 223 as a first wall portion located toward the upstream side in the flow direction of the measurement gas 2 of the main channel 22. In addition, the measuring unit 213 has the stepped surface 228 of the tip portion 213a as a second wall portion located downstream of the upstream end surface 223 as the first wall portion in the flow direction of the measurement gas 2 in the main channel 22 and located toward the upstream side in the flow direction of the measurement gas 2. An inlet 231 of the sub-channel is opened at the stepped surface 228 of this tip portion 213a.

[0038] Because the inlet 231 of the sub-channel is provided in the tip portion 213a of the measuring unit 213, which extends from the flange 211 toward the center of the main channel 22, the physical quantity measuring device 20 cannot take a gas of a portion near a center away from an inner wall surface of the main channel 22 into the sub-channel near the inner wall surface of the main channel 22. Therefore, the physical quantity measuring device 20 can measure the flow rate of the gas in the portion away from the inner wall surface of the main channel 22 and suppress the decrease in measurement accuracy due to the influence of heat or the like.

[0039] Near the inner wall surface of the main channel 22, the temperature of the main channel 22 is easily affected, and the temperature of the measurement gas 2 deviates from the original gas temperature, which is different from the average state of the main gas in the main channel 22. In particular, when the main channel 22 is the intake body of the engine, it is often maintained at a high temperature due to the influence of heat from the engine. For this reason, the gas temperature in the vicinity of the inner wall surface of the main channel 22 is often higher than the original temperature of the main channel 22, which is a factor causing the decrease in measurement accuracy. In addition, the fluid resistance near the inner wall surface of the main channel 22 is large, and the flow velocity is lower than the average flow velocity of the main channel 22.Therefore, when the gas near the inner wall surface of the main channel 22 is taken into the sub-channel as the measurement gas 2, the decrease in the flow velocity with respect to the average flow velocity of the main channel 22 may lead to a measurement error.

[0040] Because the physical quantity measuring device 20 has an inlet 231 provided in the tip portion 213a of the thin and long measuring unit 213 extending from the flange 211 toward the center of the main channel 22, the measurement error related to the decrease in flow velocity near the inner wall surface of the main channel 22 can be reduced. Furthermore, in the physical quantity measuring device 20, not only is the inlet 231 provided in the tip portion 213a of the measuring unit 213 extending from the flange 211 toward the center of the main channel 22, but the first outlet 232 and the second outlet 233 of the sub-channel are also provided in the tip portion 213a of the measuring unit 213, so it is possible to further reduce the measurement error.

[0041] In the physical quantity measuring device 20, the measuring unit 213 has a shape extending along the axis from the outer wall of the main channel 22 toward the center, but the width of the upstream end surface 223 and the downstream end surface 224 is narrower than the width of the end surface 221, and the measuring unit 213 has a plate-like shape. As a result, the physical quantity measuring device 20 can suppress the fluid resistance against the measurement gas 2 to a small value.

[0042] The measuring unit 213 is provided with a sub-channel groove 250 for forming a sub-channel 234 and a circuit chamber 235 for accommodating a circuit board 207. The circuit chamber 235 and the sub-channel groove 250 are recessed in the end surface of the measuring unit 213 and are arranged separately on one side and the other side of the measuring unit 213 in the lateral direction. The circuit chamber 235 is arranged upstream of the main channel 22 in the flow direction of the measurement gas 2, while the sub-channel 234 is arranged downstream of the circuit chamber 235 in the flow direction of the measurement gas 2 in the main channel 22.It is stated that a space can be saved in the flow direction of the measurement gas 2 in the main channel 22 by setting the surface on the upstream side of the wall portion on the upstream side of the circuit chamber 235 as the upstream end surface 223 of the measurement unit 213.

[0043] The sub-channel groove 250, in cooperation with the cover 202, forms the sub-channel 234. The sub-channel 234 extends along the longitudinal direction of the measuring unit 213, which is the direction of protrusion of the measuring unit 213. The sub-channel groove 250 forming the sub-channel 234 has a first sub-channel groove 251 and a second sub-channel groove 252 branching off in the middle of the first sub-channel groove 251.

[0044] The first sub-channel groove 251 is formed to extend along the lateral direction of the measuring unit 213 between the inlet 231 opened in the stepped surface 228 of the tip portion 213a of the measuring unit 213 and the first outlet 232 opened in the downstream end surface 224 of the tip portion 213a of the measuring unit 213. The inlet 231 is opened to face the upstream side in the flow direction of the measurement gas 2 in the main channel 22. A first sub-channel 234a is formed in the cover 202 in the first sub-channel groove 251, extending from the inlet 231 along the central axis 22a of the main channel 22 and reaching the first outlet 232.

[0045] The first sub-channel 234a receives the sample gas 2 flowing in the main channel 22 from the inlet 231 and returns the received sample gas 2 to the main channel 22 from the first outlet 232. The first sub-channel 234a extends from the inlet 231 along the flow direction of the sample gas 2 in the main channel 22 and is connected to the first outlet 232. The first sub-channel 234a has a branch section 236 between the inlet 231 and the first outlet 232.

[0046] The branch portion 236 is provided near the inlet 231 on the upstream side of the measurement gas 2 at the time of forward flow in the first sub-channel 234a extending along the central axis 22a of the main channel 22. As shown in Fig. 1, at the time of forward flow, the measurement gas 2 flows from the air cleaner 21 along the central axis 22a of the main passage 22 toward the internal combustion engine 10. At the time of forward flow, the measurement gas 2 flowing through the main passage 22 is taken into the first sub-passage 234a from the inlet 231, flows toward the first outlet 232 in the first sub-passage 234a, and flows into the second sub-passage 234b from the branch portion 236.

[0047] The second sub-channel groove 252 branches off at an intermediate position of the first sub-channel groove 251 toward a base end portion of the measuring unit 213, ie, the flange 211, and extends in the longitudinal direction of the measuring unit 213, ie, in the direction intersecting the central axis 22a of the main channel 22, e.g., in the direction substantially orthogonal to the central axis 22a.

[0048] Further, the second sub-channel groove 252 extends in a direction that is bent near the flange 211 of the measuring unit 213 and folded back toward the tip portion 213a, e.g., in a U-shape or an arc shape, and in a direction that intersects the longitudinal direction of the measuring unit 213, that is, the central axis 22a of the main channel 22, e.g., in a direction substantially orthogonal to the central axis 22a.

[0049] Finally, the second sub-channel groove 252 is bent toward the downstream end surface 224 of the measuring unit 213, for example, into an arc shape, and is connected to the second outlet 233. The second outlet 233 is opened to face the downstream side in the flow direction of the measurement gas 2 in the main channel 22. The second outlet 233 has an opening area substantially equal to or slightly larger than that of the first outlet 232 and is formed at a position adjacent to the base end portion of the measuring unit 213 from the first outlet 232 in the longitudinal direction.

[0050] In the second sub-channel groove 252, the second sub-channel 234b, which branches off from the first sub-channel 234a toward the flange 211 and reaches the second outlet 233, is formed in the cover 202.

[0051] The second sub-channel 234b allows the measurement gas 2, which branches off and flows in from the first sub-channel 234a, to pass through and returns the measurement gas 2 from the second outlet 233 to the main channel 22. The second sub-channel 234b has a reciprocating path along the longitudinal direction of the measuring unit 213. More specifically, the second sub-channel 234b includes, for example, a linear upstream portion 237, an arcuate or U-shaped bent portion 238, and a linear downstream portion 239.

[0052] The upstream portion 237 branches off, for example, from the branch portion 236 of the first sub-channel 234a and extends substantially linearly in the direction intersecting the central axis 22a of the main channel 22. The upstream portion 237 extends, for example, in a direction substantially orthogonal to the central axis 22a of the main channel 22, i.e., in a direction extending from the branch portion 236 of the first sub-channel 234a toward the flange 211.

[0053] The bent portion 238 is connected, for example, to a downstream end portion of the upstream portion 237 near the flange 211 and is bent to fold back toward the central axis 22a of the main channel 22. The bent portion 238 has, for example, an arc shape or a U-shape and is bent to fold the second sub-channel 234b by 180° in a reverse direction.

[0054] The downstream portion 239 is connected, for example, near the flange 211, to the downstream end portion of the bent portion 238 and extends substantially linearly in the direction of the central axis 22a of the main channel 22. The downstream portion 239 extends, for example, toward the tip portion 213a of the measuring unit 213, substantially parallel to the upstream portion 237 and extends from the branch portion 236 in the first sub-channel 234a toward the downstream side. The downstream portion 239 is connected to the second outlet 233 near the second outlet 233 of the tip portion 213a by being bent in the direction along the central axis 22a of the main channel 22.

[0055] The second sub-channel 234b has a curved shape. Specifically, the upstream portion 237 of the second sub-channel 234b branches off from the branch portion 236 of the first sub-channel 234a, extending in the direction intersecting the central axis 22a of the main channel 22. The curved portion 238 of the second sub-channel 234b is bent to fold back from the upstream portion 237 toward the central axis 22a of the main channel 22. The downstream portion 239 of the second sub-channel 234b extends from the bent portion 238 toward the central axis 22a of the main channel 22. The bent shape of the second sub-channel 234b is formed by the upstream portion 237, the bent portion 238, and the downstream portion 239.

[0056] For example, the second outlet 233 is omitted, the downstream portion 239 of the second sub-channel 234b is connected to the downstream side of the branch portion 236 of the first sub-channel 234a, and the second sub-channel 234b may be connected to the first sub-channel 234a, although this is not illustrated.

[0057] In the second sub-channel 234b, for example, the flow rate sensor 205 is arranged in the upstream section 237.

[0058] More specifically, the flow sensor 205 is arranged in the upstream portion 237 of the second sub-channel 234b, in an intermediate portion between the first sub-channel 234a and the bent portion 238. The above-described bent shape allows the second sub-channel 234b to ensure a longer channel length, and when pulsation occurs in the measurement gas 2 in the main channel 22, the influence on the flow sensor 205 can be reduced.

[0059] According to the above configuration, the sub-channel 234 can be formed along the longitudinal direction, which is the protrusion direction of the measuring unit 213, and the length of the sub-channel 234 can be ensured to be sufficiently long. As a result, the physical quantity measuring device 20 can be provided with the sub-channel 234 having a sufficient length. Therefore, the physical quantity measuring device 20 can suppress the fluid resistance to a small value and measure the physical quantity of the measurement gas 2 with high accuracy.

[0060] Because the first sub-channel 234a extends from the inlet 231 along the lateral direction of the measuring unit 213, that is, the central axis 22a of the main channel 22, and reaches the first outlet 232, foreign matter such as dust entering the first sub-channel 234a from the inlet 231 can be discharged from the first outlet 232 as it is. As a result, it is possible to suppress the intrusion of foreign matter into the second sub-channel 234b and to suppress the influence on the flow sensor 205 arranged in the second sub-channel 234b.

[0061] In the inlet 231 and the first outlet 232 of the first sub-channel 234a, an opening area of ​​the inlet 231 is larger than that of the first outlet 232. By making the opening area of ​​the inlet 231 larger than that of the first outlet 232, the measurement gas 2 flowing into the first sub-channel 234a can be reliably guided to the second sub-channel 234b branching off in the middle of the first sub-channel 234a.

[0062] Near the inlet 231 of the first sub-channel groove 251, a protrusion 253 is provided at the center position of the inlet 231 in the longitudinal direction of the measuring unit 213. The protrusion 253 halves the size of the inlet 231 in the longitudinal direction of the measuring unit 213 and makes the opening areas of each of the halved inlets 231 smaller than the opening areas of the first outlet 232 and the second outlet 233. The protrusion 253 can restrict the size of foreign matter that can enter the first sub-channel 234a from the inlet 231 to be smaller than that of the first outlet 232 and the second outlet 233, and prevent the first outlet 232 or the second outlet 233 from being blocked by the foreign matter.

[0063] The circuit board 207 is housed in the circuit chamber 235 provided on one side of the measuring unit 213 in the lateral direction. The circuit board 207 has a rectangular shape extending along the longitudinal direction of the measuring unit 213 and has a chip package 208, a pressure sensor 204, a temperature / humidity sensor 206, and an intake air temperature sensor 203 mounted on its surface. The circuit board 207 has a mounting portion common to all sensors and can be commonly used for the mounting patterns of various sensors. The surface of the circuit board 207 is arranged substantially parallel to the measurement gas 2 flowing through, for example, the main duct 22. This makes it possible to reduce the thickness of the measuring unit 213 and reduce the pressure loss of the measurement gas 2 flowing through the main duct 22.

[0064] The chip package 208 is mounted on the circuit board 207. The chip package 208 is assembled with, for example, the flow rate sensor 205 and an LSI, which is an electronic component for driving the flow rate sensor 205, and sealed by a compression molding process. The electronic components mounted on the chip package 208 constitute the signal processing unit 260, which processes an output signal of the flow rate sensor 205. The chip package 208 is mounted in a state where a portion of the chip package 208 protrudes from the circuit board 207 at the center position in the longitudinal direction of the circuit board 207 into the second sub-channel 234b, so that the flow rate sensor 205 is disposed in the second sub-channel 234b.

[0065] The chip assembly 208 is arranged between the sub-channel 234 and the circuit chamber 235. As a result, the circuit chamber 235 and the sub-channel 234 are separated, and the nominal flow in the flow sensor 205 arranged in the chip assembly 208 is determined by the shape of the sub-channel 234. Therefore, the sub-channel 234 has no barrier that obstructs the flow of the measurement gas 2, and the stable flow of the measurement gas 2 can be supplied to the flow sensor 205. Therefore, it is possible to miniaturize the measuring unit 213 while maintaining the flow rate sensitivity, noise performance, and pulsation characteristics of the flow sensor.

[0066] It is noted that the flow sensor 205 does not necessarily have to be provided in the chip package 208. For example, the flow sensor 205 may be disposed in the sub-channel 234 by protruding a portion of the circuit board 207, or the flow sensor 205 mounted on the circuit board 207 may be mounted in the sub-channel 234 by a plate-like bracket.

[0067] The flow sensor 205 and the LSI may be integrally formed in the same semiconductor element or may be formed as different semiconductor elements. The flow sensor 205 is sealed with a resin so that the flow measurement unit is at least exposed on its surface. Although the structure in which the LSI is provided in the chip package 208 has been described, the structure in which the LSI is mounted on the circuit board 207 may be used. The advantage of providing the LSI in the chip package 208 is that it is not necessary to mount the LSI on the circuit board 207, which contributes to the miniaturization of the circuit board 207.

[0068] The chip assembly 208 has a recessed groove extending along the flow direction of the measurement gas 2 in the upstream portion of the second sub-channel 234b, and a bottom of the recessed groove is provided with the flow rate sensor 205. The recessed groove of the chip assembly 208 has a squashed shape in which the width gradually tapers from both end portions toward the center in the flow direction of the measurement gas 2 flowing along the upstream portion of the second sub-channel 234b, with the flow rate sensor 205 disposed at the narrowest center. Due to this squashed shape, the measurement gas 2 flowing through the sub-channel 234 is corrected, and the influence of noise can be reduced.

[0069] The pressure sensor 204 is mounted on the base end portion side of the circuit board 207 in the longitudinal direction of the chip package 208, and the temperature / humidity sensor 206 is mounted on a tip side of the circuit board 207 in the longitudinal direction of the chip package 208. A lead of the intake air temperature sensor 203 is connected to the surface of the circuit board 207. The intake air temperature sensor 203 is mounted such that the lead of the intake air temperature sensor 203 is connected to the tip side position of the circuit board 207 in the longitudinal direction of the temperature / humidity sensor 206, and the sensor body 203b is disposed at a position exposed to the outside of the measurement unit 213 so as to protrude from the circuit board 207 in the longitudinal direction.

[0070] The intake air temperature sensor 203 is arranged between the upstream end surface 223 on the flange 211 side of the measuring unit 213 and the stepped surface 228 of the tip portion 213a. The intake air temperature sensor 203 is mounted on the circuit board 207 and is provided so as to be exposed to the outside of the measuring unit 213. The intake air temperature sensor 203 is formed by an axial lead component including a columnar sensor body and a pair of leads projecting away from each other in the axial direction at both end portions of the sensor body. The measuring unit 213 is provided with a protector 202a for protecting the intake air temperature sensor 203.

[0071] The measuring unit 213 includes (1) the pressure sensor 204, (2) the flow rate sensor 205, (3) the temperature / humidity sensor 206, and (4) the intake air temperature sensor 203 in order from the base end portion side toward the tip portion side along its longitudinal direction (in the direction of protrusion of the measuring unit 213). The pressure sensor 204 measures the pressure of the measurement gas 2, while the flow rate sensor 205 measures the flow rate of the measurement gas 2. The temperature / humidity sensor 206 measures the humidity of the measurement gas 2, while the intake air temperature sensor measures the temperature of the measurement gas 2.

[0072] Fig. 5 is a block diagram illustrating a configuration of a portion of the physical quantity measuring device 20 according to a first embodiment of the present disclosure.

[0073] As described above, the physical quantity measuring device 20 includes a flow sensor 205 that outputs a signal corresponding to the flow rate of the gas, and a signal processing unit 260 that processes an output signal of the flow sensor 205. Furthermore, the signal processing unit 260 includes a buffer 261, an offset adjustment unit 262, a gain calculation unit 263, a correction calculation unit 264, and a frequency analysis unit 265, as described above. Fig. 5, the buffer 261 includes a flow rate waveform buffer 261a, an offset waveform buffer 261b, and a correction waveform buffer 261c.

[0074] In the Fig. 5, the flow sensor 205 further comprises a heating resistor 205a and a temperature-sensitive resistor 205b, while the signal processing unit 260 comprises a flow measuring unit 266 as in the example shown in Fig. 2. In the example shown in Fig. 5, the signal processing unit 260 further comprises a minimum value detection unit 268a and a maximum value detection unit 268b. In the example shown in Fig. 5 are a pulsation correction unit 267 and a flow rate output unit 270, which are arranged in Fig. 2 are not illustrated.

[0075] The flow sensor 205 is located on the Fig. 4 and is arranged, for example, in the upstream portion 237 of the sub-channel 234 provided in the measuring unit 213 of the housing 201 constituting the physical quantity measuring device 20, as described above. The flow rate sensor 205 has a pair of temperature-sensitive resistors 205b on both sides of the heating resistor 205a, for example, in the flow direction of the measurement gas 2.

[0076] That is, the flow rate sensor 205 is a thermal flow meter that measures the flow rate of the gas based on the temperature difference between the pair of temperature-sensitive resistors 205b arranged on the upstream and downstream sides of the heating resistor 205a in the flow direction of the measurement gas 2. In addition to the heating resistor 205a and the temperature-sensitive resistor 205b, the flow rate sensor 205 includes, for example, a plurality of fixed resistors (not illustrated), electrode pads for establishing electrical connection with the outside, and the like.

[0077] As described above, the flow rate measuring unit 266 includes, for example, a voltage-flow rate conversion table based on the relationship between the voltage, which is the output signal of the flow rate sensor 205, and the flow rate of the measurement gas 2, and converts the output signal of the flow rate sensor 205 into the flow rate data of the measurement gas 2. The flow rate measuring unit 266 is configured, for example, by electronic components such as an arithmetic unit or a memory device mounted in the chip package 208, a program stored in the memory device, and the like.

[0078] The flow rate waveform buffer 261a stores, for example, the flow rate data of the measurement gas 2 output from the flow rate measuring unit 266 for a predetermined period based on the output signal of the flow rate sensor 205 for a predetermined period. The flow rate waveform buffer 261a is formed, for example, by a storage device such as a memory mounted in the chip package 208. The flow rate data stored in the flow rate waveform buffer 261a is overwritten, for example, with new flow rate data sequentially output from the flow rate measuring unit 266 over time.

[0079] The minimum value detection unit 268a calculates, for example, the minimum value of the flow rate waveform in a graph where a vertical axis represents flow rate and a horizontal axis represents time, based on the flow rate data stored in the flow rate waveform buffer 261a for a predetermined period. The minimum value detection unit 268a is configured, for example, by electronic components such as an arithmetic unit or a storage device mounted in the chip package 208, a program stored in the storage device, and the like.

[0080] The offset setting unit 262 sets a zero point of a flow rate waveform based on the flow rate data stored in the buffer 261. In the Fig. In the example illustrated in Figure 5, the offset setting unit 262 sets the minimum value of the flow rate waveform output from the minimum value detection unit 268a to the zero point of the flow rate waveform, thereby setting the zero point of the flow rate waveform. The offset setting unit 262 is configured, for example, by electronic components such as an arithmetic unit or a storage device mounted in the chip package 208, a program stored in the storage device, and the like.

[0081] The offset waveform buffer 261b stores the flow rate data of the flow rate waveform whose zero point has been adjusted by the offset setting unit 262. The offset waveform buffer 261b is formed, for example, by the storage device such as the memory mounted in the chip package 208.

[0082] The maximum value detection unit 268b detects the maximum value of the flow rate waveform after the zero point adjustment (offset) stored in the offset waveform buffer 261b after the zero point has been adjusted by the offset adjustment unit 262. Here, the maximum value of the flow rate waveform is, for example, the maximum value among a plurality of maximum values ​​of the offset flow rate waveform. The maximum value detection unit 268b is configured, for example, by electronic components such as an arithmetic unit or a memory device mounted in the chip package 208, a program stored in the memory device, and the like.

[0083] The gain calculation unit 263 calculates a correction gain to be multiplied by the flow rate waveform whose zero point has been adjusted. The gain calculation unit 263 calculates, as the correction gain, a gain at which the frequency analysis unit 265 does not cause an overflow. Overflow here is an arithmetic overflow, meaning that the numeric type exceeds the upper limit of the value that can be expressed in the computer's calculation and the error caused by the overflow. The overflow is sometimes also referred to as "digit overflow." The gain calculation unit 263 is configured, for example, by electronic components such as an arithmetic unit or a memory device mounted in the chip package 208, a program stored in the memory device, and the like.

[0084] The gain calculation unit 263 stores, for example, a maximum value at which overflow does not occur in the frequency analysis unit 265, which stores the transition data of the frequency analysis calculation or the calculation results, as a limit value. That is, when the maximum value of the flow rate waveform on which the frequency analysis calculation is performed exceeds this limit value, overflow occurs in the frequency analysis unit 265. The gain calculation unit 263 compares, for example, the limit value with the maximum value of the offset flow rate waveform. Then, the gain calculation unit 263 calculates the correction gain so that the maximum value of the corrected flow rate waveform, which is obtained by multiplying the offset flow rate waveform by the correction gain, becomes equal to or smaller than the above limit value. The gain calculation unit 263 may, for example,calculate the correction gain such that the maximum value of the flow rate waveform obtained by multiplying the offset flow rate waveform by the correction gain is equal to the limit value at which the overflow does not occur in the frequency analysis unit 265.

[0085] The correction calculation unit 264 multiplies the flow rate waveform by the correction gain calculated by the gain calculation unit 263 to correct the flow rate waveform whose zero point has been adjusted by the offset adjustment unit 262. Specifically, the correction calculation unit 264 reads the offset flow rate waveform from the offset waveform buffer 261b and multiplies the correction gain output from the gain calculation unit 263 by the offset flow rate waveform to calculate the offset flow rate waveform data. The correction calculation unit 264 is configured, for example, by electronic components such as an arithmetic unit or a storage device mounted in the chip package 208, a program stored in the storage device, and the like.

[0086] The correction waveform buffer 261c stores the flow rate data of the corrected flow rate waveform obtained by multiplying the flow rate waveform after the zero point adjustment by the offset adjustment unit 262, that is, the offset flow rate waveform, by the correction gain by the correction calculation unit 264. The flow rate of the maximum value of the corrected flow rate waveform is equal to or less than the limit value at which overflow does not occur in the frequency analysis calculation of the frequency analysis unit 265.

[0087] The frequency analysis unit 265 reads the corrected flow rate waveform from the correction waveform buffer 261c and performs the frequency analysis calculation of the corrected flow rate waveform. Furthermore, the frequency analysis unit 265 stores the data obtained by the calculation, such as the transition data in the middle of the calculation or the calculation results, as shown in Fig. 2. Further, the frequency analysis unit 265 stores the calculation results of the frequency analysis calculation in the buffer 261. The frequency analysis unit 265 is configured, for example, by electronic components such as an arithmetic unit or a storage device mounted in the chip package 208, a program stored in the storage device, and the like.

[0088] The pulsation correction unit 267 reads the result of the frequency analysis calculation by the frequency analysis unit 265 from the buffer 261, such as in Fig. 2, although this is not Fig. 5 is omitted. Further, the pulsation correction unit 267 reads, for example, the flow rate waveform output from the flow rate measuring unit 266 and stored in the flow rate waveform buffer 261a of the buffer 261. Then, the flow rate waveform based on the output signal of the flow rate sensor 205 is corrected based on the result of the frequency analysis calculation by the frequency analysis unit 265.

[0089] Further, as described above, the flow rate output unit 270 outputs the flow rate data of the measurement gas 2 whose pulsation is corrected, outputted from the pulsation correction unit 267, to the outside of the physical quantity measuring device 20 via the external terminal of the connector 212, although this is not Fig. 5 is omitted. The flow rate output unit 270 is configured, for example, by electronic components such as an arithmetic unit or a storage device mounted in the chip package 208, a program stored in the storage device, the output terminal, and the like.

[0090] The following describes the operation of the physical quantity measuring device 20 of the present embodiment with respect to Fig. 6 described.

[0091] Fig. 6 are graphical representations (A) to (C) showing a process by the signal processing unit 260 of the Fig. 5. The vertical axis of each graph is the flow rate, while the horizontal axis is time. Graphs (A) to (C) are a graph of the flow rate waveform with the zero point not adjusted, a graph of the flow rate waveform with the zero point adjusted, and a graph of the flow rate waveform after multiplication by the correction gain, respectively.

[0092] As described above, the physical quantity measuring device 20 is arranged in the intake body, which is the main passage 22 through which the measurement gas 2 flows. This is the intake air drawn from the air cleaner 21 of the control system 1 of the electronic fuel injection type internal combustion engine. The physical quantity measuring device 20 measures the physical quantity including the flow rate of the measurement gas 2 flowing through the main passage 22 and outputs the measured physical quantity to the control device 4.

[0093] As described above, the physical quantity measuring device 20 includes a flow rate sensor 205 that outputs a signal corresponding to the flow rate of the measurement gas 2, and a signal processing unit 260 that processes an output signal of the flow rate sensor 205. The signal processing unit 260 includes a buffer 261, an offset adjustment unit 262, a gain calculation unit 263, a correction calculation unit 264, and a frequency analysis unit 265. The buffer 261 stores the flow rate data of the measurement gas 2 based on the output signal of the flow rate sensor 205 for a predetermined period.

[0094] The offset adjustment unit 262 adjusts a zero point of a flow rate waveform based on the flow rate data stored in the buffer 261. The gain calculation unit 263 calculates the correction gain of the flow rate waveform whose zero point has been adjusted. The correction calculation unit 264 performs the correction by multiplying the correction gain by the flow rate waveform whose zero point has been adjusted. The frequency analysis unit 265 performs a frequency analysis calculation of the corrected flow rate waveform and stores the data obtained by the calculation in the buffer 261. Then, the gain calculation unit 263 calculates a gain at which the frequency analysis unit 265 does not cause overflow as the correction gain.

[0095] In this configuration, the flow rate signal waveform can be obtained as shown in the graphical representation (A) after Fig. 6, based on the output signal of the flow rate sensor 205. By performing the zero point adjustment of the flow rate waveform by the offset adjustment unit 262, it is further possible to obtain the offset flow rate waveform as shown in the graph (B) of Fig. 6. Further, the gain calculation unit 263 can calculate the correction gain that does not cause an overflow during the frequency analysis calculation by the frequency analysis unit 265. Further, by multiplying the correction gain by the offset of the flow rate waveform by the correction calculation unit 264, the corrected flow rate waveform can be obtained, as shown in the graphical representation (C) of Fig. 6. Furthermore, the frequency analysis unit 265 may perform the frequency analysis calculation on the corrected flow rate waveform to prevent overflow of the frequency analysis unit 265.

[0096] In addition, with the above configuration, by preventing the corrected flow rate waveform from being extremely reduced after multiplication by the correction gain, it is possible to suppress the deterioration of the amplitude information even when the amplitude of the flow rate waveform whose zero point is adjusted by the offset adjustment unit 262 is relatively large. On the other hand, when the amplitude of the flow rate waveform based on the output signal of the flow rate sensor 205 is relatively small, it is possible to increase the amplitude information of the flow rate waveform by multiplying the correction gain by the flow rate waveform whose zero point is adjusted.Therefore, according to the present embodiment, it is possible to provide the physical quantity measuring device 20 that can improve the accuracy of the result of the frequency analysis of the flow rate waveform and reduce the frequency analysis error of the gas flow rate regardless of the pulsation state of the flow rate waveform.

[0097] Furthermore, in the physical quantity measuring device 20 of the present embodiment, as described above, the signal processing unit 260 stores the flow rate data of the gas based on the output signal of the flow rate sensor 205 for a predetermined period in the buffer 261 including the flow rate waveform buffer 261a. Based on this flow rate data, the signal processing unit 260 can obtain, for example, the flow rate waveform as shown in graph (A). Further, the signal processing unit 260 includes the minimum value detection unit 268a for detecting a minimum value Fmin of the flow rate waveform. The offset setting unit 262 is configured to set this minimum value Fmin to the zero point of the flow rate waveform, as shown in graph (B).

[0098] With this configuration, for example, by performing zero point adjustment, which sets the zero point to the minimum value Fmin of the flow rate waveform as shown in graph (A), it is possible to obtain the offset flow rate waveform shown in graph (B). As a result, frequency analysis can be performed by the frequency analysis unit 265 on the unsigned flow rate data.

[0099] Furthermore, in the physical quantity measuring device 20 of the present embodiment, the signal processing unit 260 includes a maximum value detection unit 268b for detecting a maximum value Fmax of the offset flow rate waveform in which the zero point shown in graph (B) has been set. Furthermore, the gain calculation unit 263 calculates the correction gain so that the maximum value Fmax of the offset flow rate waveform is equal to or less than the limit value at which the frequency analysis unit 265 does not overflow due to the frequency analysis calculation of the frequency analysis unit 265.

[0100] With this configuration, as illustrated in graph (B), by setting the minimum value Fmin of the flow rate waveform to the zero point, it is possible to compare the maximum value Fmax of the flow rate waveform set to the zero point with the limit value at which overflow does not occur in the frequency analysis unit 265 during the frequency analysis calculation by the frequency analysis unit 265. As a result, the maximum value Fmax of the offset flow rate waveform shown in graph (B), which has the highest risk of causing overflow in the frequency analysis unit 265, can be set to be equal to or less than the above limit value. Therefore, it is possible to more reliably prevent the occurrence of overflow in the frequency analysis unit 265 during the frequency analysis calculation by the frequency analysis unit 265.Furthermore, the above configuration can improve the accuracy of the frequency analysis result of the flow rate waveform regardless of the pulsation state of the flow rate waveform.

[0101] More specific, for example, as shown in the graphical representation (B) after Fig. 6, consider the case where the maximum value Fmax of the offset flow rate waveform before multiplication by the correction gain is equal to or greater than the limit value at which the overflow does not occur in the frequency analysis unit 265. In this case, as shown in the graph (C) after Fig. 6, it is possible to calculate the correction gain by the gain calculation unit 263 so that the maximum value Fmax of the flow rate waveform after multiplication by the correction gain becomes as large a value as possible below the limit value at which no overflow occurs in the frequency analysis unit 265. As a result, it is possible to prevent the flow rate waveform from being extremely reduced after multiplication by the correction gain and to suppress deterioration of the amplitude information.

[0102] Furthermore, for example, as shown in the graphical representation (B) after Fig. 6, consider the case where the maximum value Fmax of the offset flow rate waveform before multiplication by the correction gain is smaller than the limit value at which overflow does not occur in the frequency analysis unit 265. In this case, it is possible to calculate the correction gain by the gain calculation unit 263 such that the maximum value Fmax of the flow rate waveform after multiplication by the correction gain becomes a value as large as possible below the limit value at which overflow does not occur in the frequency analysis unit 265. As a result, the flow rate waveform shown in the graphical representation (B) after Fig. 6, in contrast to the reduced flow rate waveform shown in the graph (C) after Fig. 6, whereby the more detailed amplitude information of the flow rate waveform can be obtained.

[0103] In addition, in the physical quantity measuring device 20 according to the present embodiment, the buffer 261 includes a flow rate waveform buffer 261a, an offset waveform buffer 261b, and a correction waveform buffer 261c. The flow rate waveform buffer 261a stores the flow rate data of the gas based on the output signal of the flow rate sensor 205 for a predetermined period. The offset waveform buffer 261b stores the flow rate data of the flow rate waveform whose zero point has been adjusted. The correction waveform buffer 261c stores the flow rate data of the corrected flow rate waveform multiplied by the correction gain.

[0104] With this configuration, it is possible to reduce the risk of losing the data stored in each of the flow rate waveform buffer 261a, the offset waveform buffer 261b, and the correction waveform buffer 261c compared to the case of using a single buffer 261. Specifically, when the frequency analysis process is executed in a time shorter than the time corresponding to the frequency analysis buffer length, it is possible to avoid the loss of the initial data and prevent multiple processes from being executed on a part of the analysis data.

[0105] As described above, according to one aspect of the present disclosure, it is possible to provide the physical quantity measuring device 20 that can reduce the frequency analysis error of the gas flow rate. (Second embodiment)

[0106] Fig. 7 is a block diagram illustrating a configuration of a portion of the physical quantity measuring device 20 according to a second embodiment of the present disclosure.

[0107] Fig. Fig. 8 is a diagram for describing an example of a process by the signal processing unit 260 of the Fig. 7 illustrated measuring device 20 for physical quantities. Fig. Fig. 9 is a diagram for describing another example of the process by the signal processing unit 260 of the Fig. 7 illustrated measuring device 20 for physical quantities.

[0108] The physical quantity measuring device 20 according to the second embodiment differs from that shown in Fig. 5, the physical quantity measuring device 20 according to the first embodiment includes an intermediate value calculation unit 269a and a maximum absolute value calculation unit 269b instead of the minimum value detection unit 268a and the maximum value detection unit 268b. Since the other points of the physical quantity measuring device 20 according to the second embodiment are the same as those of the physical quantity measuring device 20 according to the first embodiment, the same parts are given the same reference numerals, and their descriptions are omitted.

[0109] In the physical quantity measuring device 20 according to the second embodiment, the signal processing unit 260 has, as shown in the graphs (A) of Fig. 8 and Fig. 9, an intermediate value calculation unit 269a that calculates a zero-point correction value Z between the maximum value Fmax and the minimum value Fmin of the flow rate waveform. Further, in the physical quantity measuring device 20 according to the second embodiment, the offset setting unit 262 sets the zero-point correction value Z to the zero point of the flow rate waveform, as shown in graphs (B) of FIG. Fig. 8 and Fig. 9. The intermediate value calculation unit 269a and the maximum absolute value calculation unit 269b are formed by, for example, electronic components such as an arithmetic unit or a storage device mounted in the chip package 208, a program stored in the storage device, and the like.

[0110] With such a configuration, the frequency analysis of the flow rate waveform can be performed by the frequency analysis unit 265 on the flow rate data with a sign, whereby the same effect as that of the physical quantity measuring device 20 according to the first embodiment can be achieved.

[0111] Further, in the physical quantity measuring device 20 according to the second embodiment, the signal processing unit 260 includes the maximum absolute value calculating unit 269b that calculates the maximum absolute value FAmax of the flow rate waveform whose zero point is set as shown in the graphs (B) of FIG. Fig. 8 and Fig. 9. Further, in the physical quantity measuring device 20 of the second embodiment, the gain calculation unit 263 calculates the correction gain so that the maximum absolute value FAmax of the flow rate waveform whose zero point is set becomes as shown in the graphs (B) of FIG. Fig. 8 and Fig. 9 is equal to or less than the limit value at which the overflow does not occur by the frequency analysis calculation of the frequency analysis unit 265 in the frequency analysis unit.

[0112] Here, the maximum absolute value FAmax of the offset flow rate waveform whose zero point is set is shown in the graphs (B) of the Fig. 8 and Fig. 9, an absolute value FA of the flow rate at which the absolute value FA of the flow rate corresponding to each flow rate data of the offset flow rate waveform becomes the maximum in a predetermined period. More specifically, the maximum value detection unit 268b detects, for example, a plurality of maximum values ​​and a plurality of minimum values ​​of the offset flow rate waveform, and performs the calculation on the maximum value defined as the maximum absolute value FAmax among the absolute values ​​FA of the flow rate with the detected maximum value and minimum value.

[0113] With such a configuration, by performing the frequency analysis of the flow rate waveform by the frequency analysis unit 265 on the flow rate data having a sign, it is possible to prevent the occurrence of the overflow in the frequency analysis unit 265 and to achieve the same effect as that of the physical quantity measuring device 20 according to the first embodiment.

[0114] Furthermore, in the physical quantity measuring device 20 according to the second embodiment, as shown in Fig. 8, the intermediate value calculation unit 269a uses the average value of the maximum value Fmax and the minimum value Fmin of the flow rate waveform as the zero point correction value Z of the flow rate waveform in the graphic representation (A).

[0115] With this configuration, the correction gain calculated by the gain calculation unit 263 can be calculated based on the maximum absolute value FAmax of the maximum value Fmax and the minimum value Fmin of the flow rate waveform, which has a high risk of causing overflow in the frequency analysis unit 265. Therefore, by performing frequency analysis of the flow rate waveform by the frequency analysis unit 265 on the signed flow rate data, it is possible to more reliably prevent the occurrence of overflow in the frequency analysis unit 265.

[0116] Further, in the physical quantity measuring device 20 according to the second embodiment, as shown in Fig. 9, for example, the intermediate value calculation unit 269a uses the average value of the flow rate waveform as the zero point correction value Z of the flow rate waveform in the graphic representation (A).

[0117] With this configuration, the correction gain calculated by the gain calculation unit 263 can be calculated based on the maximum absolute value FAmax of the maximum value Fmax or the minimum value Fmin of the flow rate waveform, which has a high risk of causing overflow in the frequency analysis unit 265. Therefore, by performing frequency analysis of the flow rate waveform by the frequency analysis unit 265 on the signed flow rate data, it is possible to more reliably prevent the occurrence of overflow in the frequency analysis unit 265.

[0118] As described above, according to the second embodiment, similarly to the above-described first embodiment, it is possible to provide the physical quantity measuring device 20 which can reduce the frequency analysis error of the gas flow rate. (Third embodiment)

[0119] Fig. 10 is a block diagram illustrating a configuration of a portion of a physical quantity measuring device 20 according to a third embodiment of the present disclosure. The physical quantity measuring device 20 according to the third embodiment differs from that shown in Fig. 7, in that the physical quantity measuring device 20 includes a common buffer 261d instead of the offset waveform buffer 261b and the correction waveform buffer 261c. Since the other points of the physical quantity measuring device 20 according to the third embodiment are the same as those of the physical quantity measuring device 20 according to the second embodiment, the same parts are given the same reference numerals, and their descriptions are omitted.

[0120] In the physical quantity measuring device 20 according to the third embodiment, the buffer 261 includes a flow rate waveform buffer 261a and a common buffer 261d. As described above, the flow rate waveform buffer 261a stores the flow rate data of the gas based on the output signal of the flow rate sensor 205 for a predetermined period. The common buffer 261d stores the flow rate data of the offset flow rate waveform whose zero point has been adjusted by the offset setting unit 262. Furthermore, the common buffer 261d overwrites and stores the flow rate data of the corrected flow rate waveform obtained by multiplying the offset flow rate data by the correction gain by the correction calculation unit 264.

[0121] With this configuration, not only can the same effect as that of the physical quantity measuring device 20 according to the second embodiment described above be achieved, but also the configuration of the buffer 261 can be simplified and the cost of the physical quantity measuring device 20 can be reduced.

[0122] Although the embodiments of the physical quantity measuring device according to the present disclosure have been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and even if there are design changes and the like in the range that does not deviate from the gist of this disclosure, these design changes are included in this disclosure. List of reference symbols 2 Sample gas (gas) 20 Measuring device for physical quantities 205 flow sensor 260 Signal processing unit 261 buffers 261a Flow rate waveform buffer 261b Offset waveform buffer 261c correction waveform buffer 261d common buffer 262 Offset adjustment unit 263 Gain calculation unit 264 Correction calculation unit 265 Frequency analysis unit 268a Minimum value detection unit 268b Maximum value detection unit 269a Intermediate value calculation unit 269b Maximum absolute value calculation unit FAmax maximum absolute value Fmin minimum value Fmax maximum value Z Zero point correction value

Claims

[1] Measuring device for physical quantities, which includes: a flow sensor that outputs a signal corresponding to a flow rate of a gas, and a signal processing unit that processes an output signal of the flow sensor, wherein the signal processing unit includes a buffer that stores the flow rate data of the gas based on the output signal for a predetermined period, an offset setting unit that sets a zero point of a flow rate waveform based on the flow rate data stored in the buffer, a gain calculation unit that calculates a correction gain by which the flow rate waveform whose zero point has been adjusted is multiplied, a correction calculation unit that performs correction by multiplying the flow rate waveform whose zero point has been adjusted by the correction gain, and a frequency analysis unit that performs a frequency analysis calculation of the corrected flow rate waveform and stores the data obtained by the calculation in the buffer, wherein the gain calculation unit calculates the correction gain that does not cause overflow in the frequency analysis unit. [2] A physical quantity measuring device according to claim 1, wherein the signal processing unit has a minimum value detection unit which detects a minimum value of the flow rate signal form, and the offset setting unit sets the minimum value to a zero point of the flow rate waveform. [3] A physical quantity measuring device according to claim 1, wherein the signal processing unit has an intermediate value calculation unit which calculates a zero point correction value between a maximum value and a minimum value of the flow rate signal form, and the offset adjustment unit sets the zero point correction value to the zero point of the flow rate waveform. [4] The physical quantity measuring device according to claim 3, wherein the intermediate value calculating unit calculates an average value of the flow rate waveform as the zero point correction value. [5] The physical quantity measuring device according to claim 3, wherein the intermediate value calculating unit calculates an average value of the maximum value and the minimum value of the flow rate waveform as the zero point correction value. [6] A physical quantity measuring device according to claim 2, wherein the signal processing unit has a maximum value detection unit which detects the maximum value of the flow rate waveform whose zero point has been adjusted, and the gain calculation unit calculates the correction gain such that the maximum value is equal to or less than a limit value at which no overflow occurs due to the frequency analysis calculation in the frequency analysis unit. [7] A physical quantity measuring device according to any one of claims 3 to 5, wherein the signal processing unit has a maximum absolute value calculation unit that calculates a maximum absolute value of the flow rate waveform whose zero point has been adjusted, and the gain calculation unit calculates the correction gain so that the maximum absolute value of the flow rate waveform whose zero point has been adjusted is equal to or less than the limit value at which the overflow does not occur by the frequency analysis calculation in the frequency analysis unit. [8] A physical quantity measuring device according to claim 1, wherein the buffer comprises a flow rate waveform buffer, an offset waveform buffer that stores the flow rate data of the flow rate waveform whose zero point has been adjusted, and a correction waveform buffer that stores the flow rate data of the flow rate waveform obtained by multiplying by the correction gain. [9] A physical quantity measuring device according to claim 1, wherein the buffer comprises a common buffer which stores the flow rate data of the flow rate waveform whose zero point has been adjusted, and overwrites and stores the flow rate data of the flow rate waveform obtained by multiplying the flow rate data by the correction gain.

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