DETECTION DEVICE FOR PHYSICAL QUANTITIES

Abstract

Detection device (300) for physical quantities, comprising: a flow rate measuring element equipped with a heating element (608) and measuring a flow rate of a measurement target fluid; a heating element control unit (201) that switches a control state of the heating element (608) to either a heat generation state or a heat generation suppression state; and a signal processing unit (415) containing a buffer (801, 802) and a frequency analysis block (806) and processing a measured value of the flow rate measuring element using a main frequency calculated by the frequency analysis block (806), wherein the measured value for a past specified period is recorded in the buffer (801, 802), the frequency analysis block (806) calculates the main frequency by performing a frequency analysis of the measured value recorded in the buffer (801, 802), the signal processing unit (415), when an occurrence of an event is detected, performs a calculation using the main frequency calculated immediately before for a predetermined period from the occurrence of the event, and the event is a sudden change in the measured value and a switching of the control state performed by the heating element control unit (201), wherein the signal processing unit (415) stops the operation of the frequency analysis block (806) when the occurrence of the event is detected and continuously uses the main frequency immediately before the event occurs.

Description

Technical area

[0001] The present invention relates to a detection device for physical quantities. Technical background

[0002] A physical quantity detection device that heats a heating element and measures a flow rate is known. PTL 1 discloses an air flow meter equipped with a passage forming element that forms a passage through which a portion of intake air drawn into an engine passes, a flow rate sensor that measures an intake air flow rate passing through the passage, and an intake air temperature sensor that measures an intake air temperature. The air flow meter includes a second temperature sensor that is provided independently of the intake air temperature sensor and measures the temperature at a location affected by heat transferred to the passage forming element, and response compensation means for compensating a response delay of an output difference between an intake air temperature signal measured by the intake air temperature sensor.and a second temperature signal measured by the second temperature sensor based on a flow rate signal measured by the flow rate sensor, and the intake air temperature signal measured by the intake air temperature sensor is corrected based on an output difference compensated by the response compensation means.

[0003] PTL 2 shows a physical quantity detection device comprising a flow rate detection unit configured to include a heating element for measuring a flow rate of a fluid to be measured; a heating element control unit configured to switch a control state of the heating element to any one of a heating state and a heating-inhibiting state; and a signal processing unit configured to process a measured value of the flow rate detection unit. When the heating element control unit switches the control state, the signal processing unit processes an estimated value determined based on a measured value of the flow rate detection unit before the switching during a predetermined period immediately after the switching. Citation listPatent literature PTL 1: JP 2016-109625 A PTL 2: DE 10 2018 006040 T5 Summary of the inventionTechnical problem

[0004] In the invention described in PTL 1, the measurement accuracy is deteriorated after a heating state is changed or after a flow rate is changed. Solution to the problem

[0005] A physical quantity detection device according to a first aspect of the present invention includes a flow rate measuring element equipped with a heating element and measuring a flow rate of a measurement target fluid; a heating element control unit that switches a control state of the heating element to either a heat generation state or a heat generation suppression state; and a signal processing unit that includes a buffer and a frequency analysis block and processes a measured value of the flow rate measuring element using a main frequency calculated by the frequency analysis block, wherein the measured value for a past predetermined period is recorded in the buffer, the frequency analysis block calculates the main frequency by performing frequency analysis of the measured value recorded in the buffer, the signal processing unit, when an occurrence of an event is detected,performs a calculation using the main frequency calculated immediately before for a predetermined period from the occurrence of the event, and the event is a sudden change in the measured value and a change in the control state performed by the heating element control unit, wherein the signal processing unit then, when the occurrence of the event is detected, stops the operation of the frequency analysis block and continuously uses the main frequency immediately before the event occurs. Advantageous effects of the invention

[0006] According to the present invention, it is possible to reduce accuracy deterioration after switching the heating state or after changing the flow rate. Short description of the drawing [ Fig. 1] Fig. 1 is a cross-sectional view of a physical quantity detection device 300. [ Fig. 2] Fig. 2 is an enlarged view of a printed circuit board 400. [ Fig. 3] Fig. 3 is a diagram showing a configuration of an ECU 200 and a physical quantity detection device 300 according to a first embodiment. [ Fig. 4] Fig. 4 is a diagram showing an output characteristic of a flow rate detection circuit 601. [ Fig. 5] Fig. 5 is a diagram showing an output characteristic of a first flow rate characteristic adjustment block 800. [ Fig. 6] Fig. 6 is a diagram showing the selection of a first filter selection unit 807 and a second filter selection unit 808. [ Fig. 7] Fig. 7 is a diagram showing an operation example of the physical quantity detecting device 300. [ Fig. 8] Fig. 8 is a diagram showing a configuration of an ECU 200 and a physical quantity detection device 300 according to a second embodiment. [ Fig. 9] Fig. 9 is a diagram showing an overview of the operation of a flow rate presence and absence determining unit 839. [ Fig. 10] Fig. 10 is a diagram showing a configuration of an ECU 200 and a physical quantity detection device 300 according to a third embodiment. [ Fig. 11] Fig. 11 is a diagram showing a configuration of an ECU 200 and a physical quantity detection device 300 according to a fourth embodiment. [ Fig. 12] Fig. 12 is a diagram showing a configuration of an ECU 200 and a physical quantity detection device 300 according to a fifth embodiment. Description of the embodiments-First embodiment-

[0007] In the following, a first embodiment of a detection device for physical quantities will be described with reference to Fig. 1 to Fig. 7. In the present embodiment, although the physical quantity detecting device targets intake air of an internal combustion engine, the measurement target of the physical quantity detecting device 300 is not limited thereto. (Hardware configuration)

[0008] Fig. 1 is a cross-sectional view of the physical quantity detection device 300. The physical quantity detection device 300 includes a housing 302, a front cover 303, and a rear cover 304. The housing 302 is formed by molding a synthetic resin material. The housing 302 has a flange 311 for fixing the physical quantity detection device 300 to an intake pipe through which intake air of an internal combustion engine flows, an external connection unit 321 protruding from the flange 311 and having a connector for electrically connecting to an electronic control unit (hereinafter referred to as ECU) 200, and a measuring unit 331 extending so as to protrude from the flange 311 toward the center of the intake pipe. Various communication means can be used for communication between the physical quantity detection device 300 and the ECU 200, and may include, for example, a communication cable, a power cable, a data cable, a data line, a data link, a data cable, a data link ... B.a LIN (local area network), which is a type of in-vehicle network, is used.

[0009] The measuring unit 331 is integrally formed with a circuit board 400 by injection molding when the housing 302 is formed. The circuit board 400 includes a flow rate detection circuit 601 that measures the flow rate of a measurement target gas and a temperature detection unit 451 that detects the temperature of the measurement target gas. The flow rate detection circuit 601 includes a flow rate detection unit 602 and a processing unit 604. The flow rate detection unit 602 and the temperature detection unit 451 are arranged at positions exposed to the measurement target gas.

[0010] Fig. 2 is an enlarged view of the circuit board 400. The circuit board 400 includes a board main body 401, a first protrusion 403, and a second protrusion 450. A microcomputer 415 is mounted on the board main body 401, a flow rate detection circuit 601 coated with a synthetic resin material 418 is mounted on the first protrusion 403, and a temperature detection unit 451 is mounted on the second protrusion 450. The microcomputer 415 is connected to the flow rate detection circuit 601 and the temperature detection unit 451 through a signal line (not shown). The flow rate detection circuit 601 includes a heating element 608, which will be described later, and measures the flow rate when the heating element 608 comes into contact with a measurement target fluid in a heat-generating state.A pressure sensor and a humidity sensor, which are detection elements, are provided on a back surface of the plate main body 401. (Functional configuration)

[0011] Fig. 3 is a diagram showing the configurations of the ECU 200 and the physical quantity detection device 300. (200 ECU)

[0012] The ECU 200, which is connected to the physical quantity detection device 300, includes a heater control external instruction unit 201 and a flow rate receiving unit 202. The heater control external instruction unit 201 operates the heater control external instruction unit 201 through a predetermined operation algorithm to indicate the control state of the heater 608 provided in the physical quantity detection device 300. Specifically, the heater 608 is controlled to a heat generation state or a heat generation suppression state. However, the physical quantity detection device 300 outputs a measured value to the ECU 200 regardless of the control state of the heater 608. (Detection device for physical quantities 300)

[0013] The physical quantity detection device 300 includes a flow rate detection circuit 601 and a microcomputer 415 that processes the output value of the flow rate detection circuit 601. The functional configurations of the flow rate detection circuit 601 and the microcomputer 415 are described below. Each function of the flow rate detection circuit 601 is implemented by hardware or software, as described later. Each function of the microcomputer 415 is implemented by a hardware circuit. However, the function of the microcomputer 415 can be implemented by software processing. (Flow rate detection circuit 601)

[0014] The flow rate detection circuit 601 includes a processing unit 604 and a flow rate detection unit 602. The processing unit 604 includes a heater control internal instruction receiving unit 833, a heat generation control bridge 640, and a CPU 612, which is a central arithmetic unit. The flow rate detection unit 602 includes a heater 608 and a flow rate detection bridge 650. The flow rate detection circuit 601 controls the heater 608 according to the instruction of the heater control internal instruction unit 832 provided in the microcomputer 415 and outputs the measured value to the first flow rate setting block 800. However, the measured value is output regardless of the instruction content of the heater control internal instruction unit 832.

[0015] The heating element control internal instruction receiving unit 833 of the processing unit 604 is hardware that communicates with the heating element control processing unit 830. The heating element control internal instruction receiving unit 833 causes the heat generation control bridge 640 to control the heating element 608 in accordance with the instructions of the heating element control internal instruction unit 832. Specifically, the heating element control internal instruction unit 832 issues an instruction to switch between the heat generation state of the control state and the heat generation suppression state.When the heater control internal instruction receiving unit 833 is instructed by the heater control internal instruction unit 832 to switch to the heating state, the heater control internal instruction receiving unit 833 causes the heat generation control bridge 640 to control a heating value of the heater 608 such that the temperature of the measurement target gas becomes a predetermined temperature higher than an initial temperature, for example, increases by 100°C. This control is referred to as "heat generation state" control.

[0016] When the heater control internal instruction receiving unit 833 is instructed by the heater control internal instruction unit 832 to switch to the heat generation suppression state, the heater control internal instruction receiving unit 833 performs control of not performing heat generation of the heater 608 using the heat generation control bridge 640. This control is referred to as "heat generation suppression state" control. Furthermore, the heater control internal instruction receiving unit 833 controls the power supply to the heater 608 according to the instruction of the heater control internal instruction unit 832.Specifically, when the heat generation state is instructed, the heater control internal instruction receiving unit 833 supplies power to the heater 608, and when the heat generation suppression state is instructed, the heater control internal instruction receiving unit 833 turns off the power supply to the heater 608.

[0017] The heat generation control bridge 640 of the processing unit 604 is a bridge circuit including four temperature measuring resistors. The heat generation control bridge 640 is heated by the heating element 608 via the measurement target gas, and the resistance value changes. When the heat generation state is instructed, the CPU 612 monitors the resistance value of the heat generation control bridge 640 and controls the heating value of the heating element 608 so that the temperature of the measurement target gas becomes a predetermined temperature higher than the initial temperature, for example, increases by 100°C. When the heat generation suppression state is instructed, the CPU 612 controls the heating value of the heating element 608 so as not to cause the heating element 608 to perform heat generation. The CPU 612 realizes the above-described function by expanding and executing a program stored in a ROM (not shown) to a RAM (not shown).However, the CPU 612 does not need to perform any control when the heat generation suppression state is instructed.

[0018] The flow rate detection bridge 650 of the flow rate detection unit 602 is a bridge circuit including four temperature measuring resistors. The four temperature measuring resistors are arranged along the flow of the measurement target gas. Specifically, two temperature measuring resistors are arranged upstream of the heating element 608 in the flow path of the measurement target gas, and the other two temperature measuring resistors are arranged downstream of the heating element 608 in the flow path of the measurement target gas. Therefore, the temperature measuring resistor installed on the upstream side of the heating element 608 is cooled by the flow of the measurement target gas, and the temperature measuring resistor installed on the downstream side of the heating element 608 is heated by the measurement target gas heated by the heating element 608.The flow detection bridge 650 outputs a temperature difference between the temperature measuring resistors as a potential difference. (Microcomputer 415)

[0019] The microcomputer 415 includes a heating element control processing unit 830, a heating element control switching control processing unit 837, a first flow rate characteristic adjustment block 800, a first flow rate buffer 801, a second flow rate buffer 802, an average flow rate calculation block 803, a first amplitude amount calculation block 804a, an amplitude ratio calculation block 805, a frequency analysis block 806, a second flow rate characteristic adjustment block 809, and a flow rate correction filter 810. (Microcomputer | Heating Element Control Processing Unit 830)

[0020] The heater control processing unit 830 includes a heater control external instruction receiving unit 831 that receives instructions from the heater control external instruction unit 201 included in the ECU 200, and a heater control internal instruction unit 832. The heater control internal instruction unit 832 instructs the heater control internal instruction receiving unit 833 to change the control state of the heater 608 in accordance with the instruction from the heater control external instruction unit 201 sent via the heater control external instruction receiving unit 831. (Microcomputer | Heating Element Control Switch Control Processing Unit 837)

[0021] The heater control switching control processing unit 837 monitors the instruction of the heater control internal instruction unit 832 and detects a change from the heat generation suppression control state to the heat generation state and a change from the heat generation state to the heat generation suppression state. The heater control switching control processing unit 837 then determines which of the first to third states, to be described below, corresponds to the current state. Furthermore, the heater control switching control processing unit 837 transmits the determined state to the frequency analysis block 806. Hereinafter, the change of the instruction of the heater control internal instruction unit 832 from the heat generation suppression state to the heat generation state and the change from the heat generation state to the heat generation suppression state are also referred to as an "event."

[0022] A first state is a state within a predetermined period of time Tres immediately after detecting the change from the heat generation suppression state to the heat generation suppression state. A second state is a state within a predetermined period of time Tres immediately after detecting the change from the heat generation suppression state to the heat generation suppression state. A third state is another state, in other words, a state that lasts longer than a predetermined period of time Tres after detecting the change from the heat generation suppression state to the heat generation suppression state, and longer than a predetermined period of time Tres after detecting the change from the heat generation suppression state to the heat generation suppression state.The predetermined period Tres is a period obtained from the temperature response of the heating element 608 and the flow rate detection bridge 650, and information thereof calculated by an experiment conducted in advance is stored in the microcomputer 415. (Microcomputer | First Flow Characteristic Adjustment Block 800)

[0023] The first flow rate characteristic adjustment block 800 imparts desired characteristics to the flow rate signal output from the flow rate detection circuit 601. The first flow rate characteristic adjustment block 800 outputs the imparted characteristics to the first flow rate buffer 801 and the second flow rate buffer 802, the first filter selection unit 807, the moving average filter 811 and the low-pass filter 812, and a pulsation error reduction filter 813.

[0024] Fig. 4 and Fig. 5 are diagrams for explaining the operation of the first flow characteristic adjusting block 800. Fig. Fig. 4 is a diagram showing the output characteristics of the flow rate detection circuit 601, and Fig. 5 is a diagram showing the output characteristic of the first flow characteristic adjustment block 800. As shown in Fig. 4, the output of the flow detection circuit 601 tends to increase monotonically with respect to an increase in the actual flow rate. However, the increase width of the output of the flow detection circuit 601 is not always constant with respect to the increase width of the actual flow rate and disturbs the processing in the microcomputer 415. Therefore, the first flow characteristic adjustment block 800 gives the flow signal output from the flow detection circuit 601 desired characteristics such that it has the characteristics shown in Fig. 5 are shown. (Microcomputer | First Flow Buffer 801)

[0025] The first flow rate buffer 801 temporarily stores the output value of the first flow rate characteristic adjustment block 800. The first flow rate buffer 801 contains the flow rate value converted by the first flow rate characteristic adjustment block 800 by the flow rate of at least the pulsation cycle or more from the most recent output. The pulsation cycle of the flow rate is obtained by the calculation of the frequency analysis block 806, which will be described later. (Microcomputer | Second Flow Buffer 802)

[0026] The second flow rate buffer 802 contains the flow rate of at least the pulsation cycle or more from the most recent output. However, the size of the second flow rate buffer 802 may be the same as or different from that of the first flow rate buffer 801. The second flow rate buffer 802 deletes the old output value when the number of stored output values exceeds a predetermined number. Hereinafter, the time during which all the data stored in the second flow rate buffer 802 is replaced is referred to as a "second buffer time." In other words, the second flow rate buffer 802 stores the output value of the first flow rate characteristic adjustment block 800 after the time back by the second buffer time from the current time. (Microcomputer | Average Flow Calculation Block 803)

[0027] The average flow rate calculation block 803 refers to the first flow rate buffer 801 and calculates an average value of the output values of the first flow rate characteristic adjustment block 800. The average flow rate calculation block 803 outputs the calculation result to the amplitude ratio calculation block 805, the second filter selection unit 808, and the pulsation error reduction filter 813. (Microcomputer | First amplitude calculation block 804a)

[0028] The first amplitude magnitude calculation block 804a calculates a difference between a maximum value of the flow rate value stored in the first flow rate buffer 801 and a minimum value of the flow rate value stored in the first flow rate buffer 801 as an amplitude magnitude. The first amplitude magnitude calculation block 804a outputs the calculation result to the amplitude ratio calculation block 805. (Microcomputer | Amplitude Ratio Calculation Block 805)

[0029] The amplitude ratio calculation block 805 calculates the amplitude ratio by dividing the amplitude magnitude calculated by the first amplitude magnitude calculation block 804a by the average flow rate calculated by the average flow rate calculation block 803. The amplitude ratio calculation block 805 outputs the calculation result to the first filter selection unit 807 and the pulsation error reduction filter 813. (Microcomputer | Frequency Analysis Block 806)

[0030] The frequency analysis block 806 performs two operations based on the output of the heating element control switching control processing unit 837. The frequency analysis block 806 performs a main operation when the output of the heating element control switching control processing unit 837 is in the third state, and the frequency analysis block 806 performs a secondary operation when the output of the heating element control switching control processing unit 837 is in the first state or the second state. The main operation of the frequency analysis block 806 is to obtain a spectrum for each analysis frequency by performing a discrete Fourier transform on the flow rate value stored in the second flow rate buffer 802 and output the pulsation frequency, as described later. The secondary operation is to repeatedly output the pulsation frequency that was output immediately before.

[0031] The details of the main operations are described. The analysis frequency in the main operation is determined based on the characteristics of the measurement target fluid, which is a measurement target of the known physical quantity detection device 300. For example, when the measurement target fluid is engine exhaust gas, the measurement frequency is calculated from the number of engine cylinders and the engine speed range. Further, the power spectral density for each analysis frequency obtained is referred to, and the dominant frequency, that is, the frequency exhibiting the maximum power spectral density, is set as the pulsation frequency of the measurement target gas. An inverse of the pulsation frequency is the pulsation cycle, which determines the number of flow rate values temporarily recorded by the first flow rate buffer 801 and the second flow rate buffer 802.The frequency analysis block 806 outputs the pulsation frequency to the first filter selection unit 807 and the pulsation error reduction filter 813, and records the most recent pulsation frequency in a preliminary storage area (not shown).

[0032] The frequency analysis block 806 reads the pulsation frequency from the aforementioned preliminary storage area and outputs it when the secondary operation is performed. However, when the first filter selection unit 807 and the pulsation error reduction filter 813 detect information of the pulsation frequency by reading the data of the predetermined area in the data memory, the frequency analysis block 806 does not need to perform processing as a secondary operation. This is because the data is written to the data memory due to the main operation, and the written data is not erased unless a new write operation is performed. (Microcomputer | Second Flow Characteristic Adjustment Block 809)

[0033] The second flow rate characteristic adjustment block 809 imparts desired characteristics to the output value after the flow rate correction filter to enable calculation using the output of the physical quantity detection device 300 in a later process. That is, the calculation of the second flow rate characteristic adjustment block 809 also imparts the characteristics depending on the ECU 200 in which the post-processing is performed. (Microcomputer | Flow Correction Filter 810)

[0034] The flow rate correction filter 810 includes a moving average filter 811, a low-pass filter 812, a first filter selection unit 807, a second filter selection unit 808, and a pulsation error reduction filter 813. The moving average filter 811 calculates the moving average with a predetermined number of samplings on the output of the first flow rate characteristic adjustment block 800 as the processing target and outputs the moving average to the second filter selection unit 808. The low-pass filter 812 applies a predetermined low-pass filter to the output of the first flow rate characteristic adjustment block 800 as a processing target and outputs the output to the second filter selection unit 808.

[0035] The first filter selection unit 807 compares the amplitude ratio calculated by the amplitude ratio calculation block 805 with an amplitude ratio threshold 807a and compares the pulsation frequency calculated by a frequency analysis block 806 with a frequency threshold 807b. The first filter selection unit 807 outputs the outputs of all of the first flow rate characteristic adjustment block 800, the second filter selection unit 808, and the pulsation error reduction filter 813 to the second flow rate characteristic adjustment block 809 based on these comparisons. As a reminder, the first filter selection unit 807 can output the output of the first flow rate characteristic adjustment block 800 to the second flow rate characteristic adjustment block 809 as is, without passing through a filter.

[0036] When the amplitude ratio calculated by the amplitude ratio calculation block 805 is greater than the amplitude ratio threshold 807a and the pulsation frequency calculated by a frequency analysis block 806 is greater than the frequency threshold 807b, the first filter selection unit 807 selects the output of the pulsation error reduction filter 813. When the amplitude ratio calculated by the amplitude ratio calculation block 805 is equal to or less than the amplitude ratio threshold 807a and the flow rate average value calculated by the average flow rate calculation block 803 is equal to or less than the frequency threshold 807b, the first filter selection unit 807 selects the output of the second filter selection unit 808.When the amplitude ratio calculated by the amplitude ratio calculation block 805 is greater than the amplitude ratio threshold 807a and the pulsation frequency calculated by a frequency analysis block 806 is equal to or less than the frequency threshold 807b, and when the amplitude ratio calculated by the amplitude ratio calculation block 805 is equal to or less than the amplitude ratio threshold 807a and the average flow rate calculated by the average flow rate calculation block 803 is greater than the frequency threshold 807b, the first filter selection unit 807 does not perform the filtering processing. That is, in this case, the output of the first flow rate characteristic adjustment block 800 is output to the second flow rate characteristic adjustment block 809 as is.

[0037] The second filter selection unit 808 compares the average flow rate calculated by the average flow rate calculation block 803 with the flow rate threshold 808a. The second filter selection unit 808 outputs the output of the low-pass filter 812 to the first filter selection unit 807 when the average flow rate calculated by the average flow rate calculation block 803 is greater than the flow rate threshold 808a. The second filter selection unit 808 outputs the output of the moving average filter 811 to the first filter selection unit 807 when the average flow rate calculated by the average flow rate calculation block 803 is equal to or less than the flow rate threshold 808a.

[0038] Fig. 6 is a diagram showing the selection of the first filter selection unit 807 and the second filter selection unit 808. In Fig. 6, a region is substantially divided into four, and a lower left region is further divided into two. The first filter selection unit 807 determines which of the four large regions is selected, and the second filter selection unit 808 determines which of the two lower left regions is selected. In this way, the two filter selection units evaluate a magnitude correlation between the amplitude ratio calculated by the amplitude ratio calculation block 805 and the amplitude ratio threshold 807a, a magnitude correlation between the pulsation frequency calculated by a frequency analysis block 806 and the frequency threshold 807b, and a magnitude correlation between the flow rate average value calculated by the average flow rate calculation block 803 and the flow rate threshold 808a. (Microcomputer | Pulsation Error Reduction Filter 813)

[0039] The pulsation error reduction filter 813 calculates a measured value obtained by reducing the influence of pulsation from the output of the first flow rate characteristic adjustment block 800 using the outputs of the average flow rate calculation block 803, the amplitude ratio calculation block 805, and the frequency analysis block 806, and outputs the measured value to the first filter selection unit 807. Specifically, the pulsation error reduction filter 813 outputs one in which a frequency response correction flow rate and a flow rate dependency correction flow rate, to be described below, are added to the output of the first flow rate characteristic adjustment block 800.

[0040] The frequency response correction flow rate is the product of the frequency response gain and the output of the average flow rate calculation block 803. The frequency response gain is determined based on the output of the amplitude ratio calculation block 805 and the output of the frequency analysis block 806, with reference to a predetermined first table. For example, in the first table, the output of the amplitude ratio calculation block 805 is described on a horizontal axis, and the output of the frequency analysis block 806 is described on a vertical axis. Any interpolation operations, such as ratio interpolation, are performed as needed.

[0041] The flow rate dependency correction flow rate is the product of the fluctuation of the flow rate dependency correction gain and the frequency response correction flow rate. The flow rate dependency correction gain is determined based on the frequency response correction flow rate and the output of the amplitude ratio calculation block 805 with reference to a predetermined second table. In the second table, for example, the frequency response correction flow rate is described on a horizontal axis, and the output of the amplitude ratio calculation block 805 is described on a vertical axis.

[0042] Any interpolation operations, such as ratio interpolation, are performed as needed. The "fluctuation" of the flow-dependent correction gain is a difference of 1. For example, if the flow-dependent correction gain is "1.5," the fluctuation of the flow-dependent correction gain is "0.5." (Operational example)

[0043] The physical quantity detection device 300 detects the intake air quantity of the internal combustion engine. However, since the internal combustion engine may be stopped in a vehicle equipped with an idle stop function or a hybrid vehicle, there is a period of time during which intake air is absent. When the operation of the internal combustion engine is stopped, there is a risk of contamination of the flow rate detection bridge 650 due to the arrival of unburned gasoline from the engine side to the physical quantity detection device 300. Furthermore, in a hybrid vehicle or the like, it is conceivable to inhibit heat generation of the heating element 608 in order to prevent wasteful power consumption due to heat generation of the heating element 608 in a state where it is clear that intake air is absent.Although a problem may occur when the output of the flow rate detection circuit 601 is used as it is while the operation of the internal combustion engine is restarted or the like, the physical quantity detection device 300 solves this problem.

[0044] Fig. 7 is a diagram showing an example of operation of the physical quantity detection device 300, specifically an output of the frequency analysis block 806 of the physical quantity detection device 300. However, in order to explain the effect of the physical quantity detection device 300, the output of the flow rate detection circuit 601 and the result of simply performing the frequency analysis will also be described together. Fig. 7, a horizontal axis represents time. In Fig. 7, a time t12 represents the switching time from the heat generation state to the heat generation suppression state. Furthermore, in Fig. 7(a) to Fig. 7(c) the actual flow rate of the target fluid in the area shown in the graph is always zero and is in Fig. 7(d) to Fig. 7(f) the actual flow rate of the target fluid in the range shown in the graph is always a constant value.

[0045] Fig. 7(a) and Fig. 7(d) show the output of the flow rate detection circuit 601, Fig. 7(b) and Fig. 7(e) show the results of a simple frequency analysis and Fig. 7(c) and Fig. 7(f) show the output of the frequency analysis block 806. The results of the simple frequency analysis shown in Fig. 7(b) and Fig. 7(e) are pulsation frequencies when the frequency analysis is always performed ignoring the output of the heater control switching control processing unit 837. The signal shown in Fig. 7(a) is inputted from the flow rate detection circuit 601 to the microcomputer 415 and the signal shown in Fig. 7(c) is output by processing of the heater control switching control processing unit 837 and the frequency analysis block 806. The same also applies to a relationship between Fig. 7(d) and Fig. 7(f).

[0046] As in Fig. As shown in Figure 7(a), when the control state of the heating element 608 is switched from the heat generation suppression state to the heat generation state in a state where the actual flow rate of the measurement target fluid is zero, the flow rate measurement value increases sharply at switching time t12, then gradually decreases and is set to a stable value. The period from time t12 until the flow rate measurement value is set is Tres, and this period represents the temperature response between the heating element 608 and the flow rate detection bridge 650. The adjustment reaches, for example, the range of plus or minus 2% of the stable value.

[0047] In this case, when the calculation of the pulsation frequency by the frequency analysis block 806 continues, the output increases and decreases repeatedly around the time t12 as shown in Fig. 7(b), and after a short time, it settles at a constant value. However, the frequency analysis block 806 changes the operation depending on the output of the heater control switching control processing unit 837. In this example, the output of the heater control switching control processing unit 837 is switched from the third state to the first state at time t12. Therefore, the frequency analysis block 806 continues the output immediately before time t12 from time t12 to the period Tres. When the period Tres elapses from time t12, since the output of the heater control switching control processing unit 837 reaches the third state, the calculation is restarted, and the calculation result is output. Therefore, it can be seen that Fig. 7(c), which is the output of the frequency analysis block 806, a shorter period in which the output is not stable, compared to Fig. 7(b), in which the calculation continues.

[0048] Furthermore, as in Fig. 7(d) to Fig. 7(f), the same effect can be confirmed even when the flow rate of the measurement target fluid has a certain constant value. That is, the output of the flow rate detection circuit 601 gradually increases from time t12, as shown in Fig. 7(d), and when the calculation continues, the period in which the output is not stable is a long time, as shown in Fig. 7(e). However, by stopping the calculation based on the output of the heater control switching control processing unit 837, the period in which the output is not stable can be shortened, as shown in Fig. 7(f).

[0049] According to the above first embodiment, the following effects can be obtained. (1) The physical quantity detection device 300 includes a flow rate detection unit 602 that includes a heating element 608 and measures the flow rate of the measurement target fluid; a heating element control internal instruction receiving unit 833 that switches the control state of the heating element 608 to a heat generation state and a heat generation suppression state; and a microcomputer 415 that includes a second flow rate buffer 802 and a frequency analysis block 806, and is a signal processing unit that processes a measured value of the flow rate detection unit 602 using the pulsation frequency calculated by the frequency analysis block 806. The measured values for the past predetermined period are recorded in the second flow rate buffer 802.The frequency analysis block 806 calculates the pulsation frequency by performing frequency analysis on the measured value recorded in the second flow rate buffer 802. When the microcomputer 415 detects the switching of the control state by the heater control internal instruction receiving unit 833, the microcomputer 415 performs a calculation using the pulsation frequency calculated immediately before for a predetermined period Tres from the switching. Therefore, as shown in FIG. Fig. 7, it is possible to shorten the period in which the output is unstable after the control state is switched and to reduce the decrease in measurement accuracy. (2) When the switching of the control state is detected by the heating element control internal instruction receiving unit 833, the microcomputer 415 stops the operation of the frequency analysis block 806 and continuously uses the pulsation frequency immediately before the switching of the control state. Accordingly, the power consumption of the frequency analysis block 806 can be reduced. (3) The microcomputer 415 performs processing using the calculated value of the frequency analysis block 806 after the predetermined time period Tres has elapsed. Therefore, the microcomputer 415 can detect the most recent pulsation frequency and perform a calculation based on the frequency. (4) The predetermined time period Tres is equal to or longer than the time period required for the temperature response of the flow rate detection unit 602. Therefore, it is possible to reduce the deterioration of accuracy by setting the time period or more required for the temperature response, which is a physical limitation, to the predetermined time period Tres. (5) The microcomputer 415 includes a heater control external instruction receiving unit 831 that receives a signal for controlling the heater 608 from the outside. The heater control internal instruction unit 832 changes the control state of the heater 608 based on the operation instruction of the heater control external instruction receiving unit 831. Therefore, it is possible to appropriately save power according to the operation instruction of the device that uses the output of the physical quantity detection device 300. For example, when the ECU 200 that uses the output of the physical quantity detection device 300 does not refer to the output of the physical quantity detection device 300 for a certain period of time, by instructing the heat generation suppression state to the physical quantity detection device 300, unnecessary heating of the heater 608 can be avoided. (Modified Example 1)

[0050] In the aforementioned first embodiment, the microcomputer 415 includes a second filter selection unit 808 that selects either the moving average filter 811 or the low-pass filter 812. However, the microcomputer 415 may include only one of the moving average filter 811 and the low-pass filter 812. In this case, the second filter selection unit 808 may also be omitted. (Modified Example 2)

[0051] In the aforementioned first embodiment, the physical quantity detection device 300 measures the flow rate, temperature, pressure, and humidity. However, the physical quantity detection device 300 only needs to measure at least the flow rate and does not need to measure at least one of the other four physical quantities. (Modified Example 3)

[0052] When the microcomputer 415 detects that the instruction of the heater control internal instruction unit 832 is changed from the heat generation suppression state to the heat generation state or from the heat generation state to the heat generation suppression state, the microcomputer 415 may continue the operation of the frequency analysis block 806 without updating the second flow rate buffer 802. For example, the first flow rate characteristic adjustment block 800 may refer to the output of the heater control switching control processing unit 837, and the output may be supplied only to the second flow rate buffer 802 when the output is in the third state. In this case, since the operation of the frequency analysis block 806 continues, the logic for controlling the operation of the frequency analysis block 806 can be simplified and the design can be diversified. (Modified Example 4)

[0053] The predetermined time period Tres may be equal to or longer than the second buffer time, that is, the time for replacing all data stored in the second flow rate buffer 802. However, it is desirable that the predetermined time period Tres be equal to or longer than the time period required for the temperature response of the flow rate detection unit 602 and equal to or longer than the second buffer time. When a predetermined time period Tres is equal to or longer than the second buffer time, when the frequency analysis block 806 restarts the frequency analysis, a stable output is possible because the previous measured value before the control state change does not remain in the second flow rate buffer 802. (Modified Example 5)

[0054] The frequency analysis block 806 may perform a main operation when the output of the heating element control switching control processing unit 837 is in the second state. In other words, the frequency analysis block 806 may repeatedly output the pulsation frequency output immediately before only in a predetermined period Tres immediately after detecting the change from the first state, that is, from the heat generation suppression state to the heat generation state. -Second embodiment-

[0055] A second embodiment of the physical quantity detection device will be described with reference to Fig. 8 to Fig. 9 described.

[0056] In the following description, the same components as in the first embodiment are denoted by the same reference numerals, and differences will be mainly described. Points not specifically described are the same as in the first embodiment. This embodiment differs from the first embodiment mainly in that the heater control processing unit 830 of the physical quantity detection device 300 does not include the heater control external instruction receiving unit 831.

[0057] Fig. 8 is a diagram showing a configuration of a physical quantity detection device 300 according to the second embodiment. A hardware configuration of the physical quantity detection device 300 in the present embodiment is the same as that of the first embodiment. A functional configuration of the physical quantity detection device 300 in the present embodiment is different from that of the first embodiment in that the heater control external instruction receiving unit 831 is removed, a flow rate presence and absence determination unit 839 is added, and the operation of the heater control internal instruction unit 832 is different.

[0058] The flow rate presence / absence determination unit 839 determines whether the flow rate detected by the flow rate detection unit 602 is a value indicating zero, in other words, whether the actual flow rate is zero, using the calculated value of the average flow rate calculation block 803 and the calculated value of the first amplitude amount calculation block 804a. Further, the flow rate presence / absence determination unit 839 instructs control of the heat generation state when it is determined that the actual flow rate is not zero, and instructs control of the heat generation suppression state when it is determined that the actual flow rate is zero.The flow rate presence and absence determination unit 839 determines the presence and absence of the actual flow rate from the calculated value of the average flow rate calculation block 803 and the calculated value of the first amplitude amount calculation block 804a as follows.

[0059] Fig. 9 is a diagram showing an operational overview of the flow rate presence / absence determination unit 839. The flow rate presence / absence determination unit 839 compares the calculated value of the average flow rate calculation block 803 with the average flow rate threshold 845a and compares the calculated value of the first amplitude amount calculation block 804a with the amplitude amount threshold 845b. Further, when determining that both calculated values are below the threshold, the flow rate presence / absence determination unit 839 determines that the actual flow rate is zero and issues an instruction to control the heat generation suppression state.In other cases, the flow rate presence / absence determination unit 839 determines that the actual flow rate is not zero and issues an instruction to control the heat generation state. However, the presence / absence of the actual flow rate determined by the flow rate presence / absence determination unit 839 does not mean strictly zero, but rather "relatively small."

[0060] Specifically, when the average flow rate calculated by the average flow rate calculation block 803 is greater than the average flow rate threshold 845a or when the calculated value of the first amplitude amount calculation block 804a is greater than the amplitude amount threshold 845b, the flow rate presence and absence determination unit 839 determines that the actual flow rate is not zero and instructs the heater control internal instruction unit 832 to control the heat generation state.When the average flow rate calculated by the average flow rate calculation block 803 is equal to or less than the average flow rate threshold 845a and the calculated value of the first amplitude amount calculation block 804a is equal to or less than the amplitude amount threshold 845b, the flow rate presence and absence determination unit 839 determines that the actual flow rate is zero and instructs the heater control internal instruction unit 832 to control the heat generation suppression state.

[0061] According to the above second embodiment, the following effects can be obtained.

[0062] (6) The physical quantity detection device 300 includes the first flow rate buffer 801, the average flow rate calculation block 803, the first amplitude calculation block 804a, and the flow rate presence and absence determination unit 839, which determines the presence and absence of the flow rate of the measurement target fluid and outputs an operation instruction to the heat generation control bridge 640 and the CPU 612 via the heater control internal instruction unit 832. The heat generation control bridge 640 and the CPU 612 operate based on the operation instruction of the flow rate presence and absence determination unit 839.When the average flow rate is equal to or less than the average flow rate threshold 845a and the amplitude amount is equal to or less than the amplitude amount threshold 845b, the flow rate presence / absence determination unit 839 determines that the flow rate of the measurement target fluid is zero and is controlled to enter the heat generation suppression state. When the average flow rate is greater than the average flow rate threshold 845a or when the amplitude amount is greater than the amplitude amount threshold 845b, the flow rate presence / absence determination unit 839 determines that the flow rate of the measurement target fluid is not zero and is controlled to enter the heat generation suppression state.Therefore, since the physical quantity detecting device 300 controls the heating element 608 without receiving an operation instruction from the external ECU 200, the control can be performed based on the actual environment, and further, improvement in stain resistance and further power saving of the flow rate detecting bridge 650 are realized. -Third embodiment-

[0063] A third embodiment of the physical quantity detection device will be described with reference to Fig. 10. In the following description, the same components as in the first embodiment and the second embodiment are designated by the same reference numerals, and differences will be mainly described. Points not specifically described are the same as in the first embodiment. This embodiment differs from the second embodiment mainly in that it includes a heater control external instruction receiving unit 831.

[0064] Fig. 10 is a diagram showing a configuration of a physical quantity detection device 300 according to the third embodiment. A hardware configuration of the physical quantity detection device 300 in the present embodiment is the same as that of the third embodiment. The functional configuration of the physical quantity detection device 300 in the present embodiment differs from that of the third embodiment in that a heater control external instruction receiving unit 831 is added and the operation of the heater control internal instruction unit 832 is different.

[0065] The operation of the heater control external instruction receiving unit 831 is the same as in the first embodiment. The heater control internal instruction unit 832 instructs the heater control internal instruction receiving unit 833 to change the control state of the heater 608 in accordance with the instruction of the heater control external instruction unit 201 transmitted via the heater control external instruction receiving unit 831 and the instruction of the flow rate presence / absence determination unit 839. When the instruction of the heater control external instruction unit 201 and the instruction of the flow rate presence / absence determination unit 839 are different from each other, the heater control internal instruction unit 832 gives priority to the instruction of the heater control external instruction unit 201.

[0066] According to the aforementioned third embodiment, the physical quantity detection device can be used not only by connecting it to an ECU equipped with the heater control external instruction unit 201, but also by connecting it to an ECU not equipped with the heater control external instruction unit 201. Furthermore, when the ECU to be connected includes the heater control external instruction unit 201, power saving based on the operation of the ECU can be achieved because the ECU's instruction for the operation of the heater 608 is prioritized. (Modified example of the third embodiment)

[0067] In the aforementioned third embodiment, when the instruction of the heating element control external instruction unit 201 and the instruction of the flow rate presence / absence determination unit 839 are different from each other, the heating element control internal instruction unit 832 gives priority to the instruction of the heating element control external instruction unit 201. However, when the instruction of the heating element control external instruction unit 201 and the instruction of the flow rate presence / absence determination unit 839 are different from each other, the heating element control internal instruction unit 832 may give priority to the instruction of the flow rate presence / absence determination unit 839.According to this modified example, since the transition to the heat generation suppression state is performed by the determination of the presence and absence of a flow rate by the determination unit 839, the power consumption of the physical quantity detection device 300 can be suppressed. -Fourth embodiment-

[0068] A fourth embodiment of the physical quantity detection device will be described with reference to Fig. 11. In the following description, the same components as in the first to third embodiments are denoted by the same reference numerals, and differences will be mainly described. Points not specifically described are the same as in the third embodiment. The present embodiment differs from the third embodiment mainly in that an amplitude determination unit 860 is also provided such that frequency analysis is not performed even when a change in the flow rate is large.

[0069] Fig. 11 is a diagram showing the configuration of the physical quantity detection device 300 according to the fourth embodiment. A hardware configuration of the physical quantity detection device 300 in the present embodiment is the same as that of the third embodiment. A functional configuration of the physical quantity detection device 300 in the present embodiment differs from that of the third embodiment in that the amplitude magnitude determination unit 860 is further provided. (Microcomputer | Amplitude Determination Unit 860)

[0070] The amplitude magnitude determination unit 860 determines whether the amplitude magnitude output from the first amplitude magnitude calculation block 804a is greater than a predetermined threshold value, and outputs the determination result to the frequency analysis block 806. For example, the amplitude magnitude determination unit 860 outputs a signal indicating an excessive amplitude when the amplitude magnitude is greater than a predetermined threshold value, and does not output a signal indicating an excessive amplitude when the amplitude magnitude is equal to or less than a predetermined threshold value. In the present embodiment, the fact that the amplitude magnitude output from the first amplitude magnitude calculation block 804a is greater than a predetermined threshold value, in other words, that the measured value suddenly changes, is also referred to as an "event" occurring.

[0071] The frequency analysis block 806 performs the secondary operation itself in the period in which the amplitude amount determination unit 860 outputs the signal having an excessive amplitude and in the second buffer time after the output of the signal having an excessive amplitude is finished.In other words, the amplitude amount determination unit 860 performs the secondary operation in a case corresponding to any one of the following cases: a case where the output of the heater control switching control processing unit 837 is in the first state, a case where the output of the heater control switching control processing unit 837 is in the second state, a case where the amplitude amount determination unit 860 outputs a signal having an excessive amplitude, and a case where the amplitude amount determination unit 860 is in the second buffer time after the output of the signal having the excessive amplitude is finished.

[0072] According to the aforementioned fourth embodiment, the following operational effects can be obtained in addition to the first embodiment. That is, even when the measured value changes abruptly, since the frequency analysis block 806 repeatedly outputs the pulsation frequency calculated immediately before, it is possible to shorten the period during which the output is unstable after the control state is switched and reduce deterioration in measurement accuracy. -Fifth embodiment-

[0073] A fifth embodiment of the physical quantity detection device will be described with reference to Fig. 12. In the following description, the same components as in the first to fourth embodiments are denoted by the same reference numerals, and differences will be mainly described. Points not specifically described are the same as in the fourth embodiment. This embodiment differs from the fourth embodiment mainly in that it includes a second amplitude magnitude calculation block 861.

[0074] Fig.12 is a diagram showing a configuration of the physical quantity detection device 300 according to the fifth embodiment. A hardware configuration of the physical quantity detection device 300 in the present embodiment is the same as that of the fourth embodiment. A functional configuration of the physical quantity detection device 300 in the present embodiment is different from that of the fourth embodiment in that a second amplitude amount calculation block 804b is further provided. The second amplitude amount calculation block 804b calculates a difference between a maximum value of the flow rate value stored in the second flow rate buffer 802 and a minimum value of the flow rate value stored in the second flow rate buffer 802 as an amplitude amount and outputs it to the amplitude amount determination unit 860.

[0075] In the present embodiment, the amplitude magnitude determination unit 860 determines whether the output of the second amplitude magnitude calculation block 804b is greater than the predetermined threshold instead of the output of the first amplitude magnitude calculation block 804a, and outputs the determination result to the frequency analysis block 806. The operation of the frequency analysis block 806 is the same as in the fourth embodiment. In the present embodiment, a state in which the amplitude magnitude output of the second amplitude magnitude calculation block 804b is greater than a predetermined threshold is also referred to as an "event" occurring.

[0076] All of the above-mentioned embodiments and modified examples can be combined with each other. Although various embodiments and modified examples have been described above, the present invention is not limited to the contents thereof. Other aspects conceivable within the scope of the technical concept of the present invention are also included within the scope of the present invention. List of reference symbols 300 Detection device for physical quantities 415 microcomputers 601 Flow rate detection circuit 602 Flow rate detection unit 604 processing unit 608 Heating element 640 Heat generation control bridge 650 Flow detection bridge 803 Average flow calculation block 804a first amplitude calculation block 804b second amplitude calculation block 805 Amplitude ratio calculation block 806 Frequency analysis block 810 Flow correction filter 811 Moving average filter 812 low-pass filter 813 Pulsation error reduction filter 830 Heating Element Control Processing Unit 831 Heating element control external instruction receiving unit 832 Heating Element Control Internal Display Unit 833 Heating element control internal instruction receiving unit 837 Heating element control switching control processing unit 839 Unit of determination of the presence and absence of a flow rate 860 Amplitude determination unit

Claims

[1] Detection device (300) for physical quantities, comprising: a flow rate measuring element equipped with a heating element (608) and measuring a flow rate of a measurement target fluid; a heating element control unit (201) that switches a control state of the heating element (608) to either a heat generation state or a heat generation suppression state; and a signal processing unit (415) containing a buffer (801, 802) and a frequency analysis block (806) and processing a measured value of the flow rate measuring element using a main frequency calculated by the frequency analysis block (806), wherein the measured value for a past specified period is recorded in the buffer (801, 802), the frequency analysis block (806) calculates the main frequency by performing a frequency analysis of the measured value recorded in the buffer (801, 802), the signal processing unit (415), when an occurrence of an event is detected, performs a calculation using the main frequency calculated immediately before for a predetermined period from the occurrence of the event, and the event is a sudden change in the measured value and a switching of the control state performed by the heating element control unit (201), wherein the signal processing unit (415) stops the operation of the frequency analysis block (806) when the occurrence of the event is detected and continuously uses the main frequency immediately before the event occurs. [2] The physical quantity detection device (300) according to claim 1, wherein the signal processing unit (415) performs processing using a calculated value of the frequency analysis block (806) after the lapse of the predetermined period of time. [3] The physical quantity detection device (300) according to claim 1, wherein the predetermined period of time is equal to or longer than a period of time required for a temperature response of the flow rate measuring element. [4] The physical quantity detection device (300) according to claim 1, wherein the predetermined period of time is equal to or longer than a period of time in which the buffer (801, 802) is completely updated. [5] A physical quantity detection device (300) according to claim 1, further comprising: a signal receiving unit (831) which receives a signal for controlling the heating element (608) from outside, wherein the heating element control unit (201) changes the control of the heating element (608) based on the signal. [6] A physical quantity detection device (300) according to claim 1, further comprising: a buffer (801, 802) which temporarily records measured values for a past predetermined period of time; an average flow rate calculation block that calculates an average flow rate, which is an average of the flow rate, with reference to the buffer (801, 802); an amplitude amount calculation block that calculates an amplitude amount, which is an amplitude of the flow rate, with reference to the buffer (801, 802); and a flow rate presence and absence determination unit (602) that determines a presence and absence of the flow rate of the measurement target fluid and outputs an operation instruction to the heater control unit (201), wherein the heating element control unit (201) operates on the basis of the operating instruction, and the flow rate presence and absence determination unit (602) determines that the flow rate of the measurement target fluid is zero when the average flow rate is equal to or less than a predetermined first threshold and the amplitude amount is equal to or less than a predetermined second threshold, and controls the heating element control unit (201) to reach the heat generation suppression state, and the flow rate presence and absence determination unit (602) determines that the flow rate of the measurement target fluid is not zero when the average flow rate is greater than the predetermined first threshold or when the amplitude amount is greater than the predetermined second threshold, and controls the heating element control unit (201) to reach the heat generation state. [7] A physical quantity detection device (300) according to claim 1, further comprising: a signal receiving unit (831) that receives a signal for controlling the heating element (608) from outside; a buffer (801, 802) which temporarily records measured values for a past predetermined period of time; an average flow rate calculation block (803) that calculates the average flow rate, which is an average of the flow rate, with reference to the buffer (801, 802); an amplitude amount calculation block (804) that calculates an amplitude amount, which is an amplitude of the flow rate, with reference to the buffer (801, 802); and a flow rate presence and absence determination unit (602) which determines the presence and absence of the flow rate of the measurement target fluid and outputs an operation instruction to the heater control unit (201), wherein the heating element control unit (201) operates on the basis of the signal and the operating instruction, and the flow rate presence and absence determination unit (602) determines that the flow rate of the measurement target fluid is zero when the average flow rate is equal to or less than a predetermined first threshold and the amplitude amount is equal to or less than a predetermined second threshold, and controls the heating element control unit (201) to reach the heat generation suppression state, and the flow rate presence and absence determination unit (602) determines that the flow rate of the measurement target fluid is not zero when the average flow rate is greater than the predetermined first threshold or when the amplitude amount is greater than the predetermined second threshold, and controls the heating element control unit (201) to reach the heat generation state. [8] The physical quantity detection device (300) according to claim 7, wherein the heater control unit (201) prioritizes the signal over the operation instruction.

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