JP2012078228A - Air flow rate measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate elimination of an application error in a thermal type air flow rate measuring device for measuring flow rate of intake air.SOLUTION: In an air flow rate measuring device, three terminals 54-56 are provided in a heating resistor 6 and the heating resister 6 is energized via the terminals 54-56 to generate a heating value difference between upstream side and downstream side heating resistors 48 and 49 of the heating register 6, which are respectively near to upstream side and downstream side temperature measuring resistors 7-10. Accordingly, thermal influence received by the upstream side temperature measuring resistors 7 and 8 from the heating resistor 6 and thermal influence received by the downstream side temperature measuring resistors 9 and 10 from the heating resistor 6 are made different from each other, a temperature difference-flow rate characteristic to be a reference for flow rate measurement is freely changed, and a shift of a detection value by the application error can be canceled. As a result, the application error can be easily eliminated, even if a large number of kinds of sensors are not prepared in the air flow rate measuring device.

Description

  In the present invention, for example, a flow rate of intake air (hereinafter abbreviated as an intake air amount) is generated by generating a heat transfer phenomenon between air sucked into an internal combustion engine (hereinafter also referred to as intake air). The present invention relates to a thermal air flow rate measuring device that measures the air flow rate).

  Conventionally, in the measurement of intake air amount, the thermal air flow rate that generates a detection value equivalent to the mass flow rate by generating a heat transfer phenomenon with the intake air from the advantage that the mass flow rate can be directly measured as the flow rate Measuring devices are widely used (in the following description, the direction from the air cleaner to the internal combustion engine is referred to as the forward direction, and the direction from the internal combustion engine to the air cleaner is referred to as the reverse direction with respect to the direction of intake air flow. A state in which no air is flowing in either the direction or the reverse direction is referred to as no wind.)

  For example, as shown in FIG. 14, the sensor 100 </ b> A of the conventional air flow rate measuring device 100 is arranged on the upstream side of the heating resistor 101 and the heating resistor 101 that generates heat when energized. An upstream temperature sensing resistor 102 that is affected, and a downstream temperature sensing resistor 103 that is disposed downstream of the heating resistor 101 and that is thermally influenced by the heating resistor 101, is provided upstream and downstream. The resistance temperature detectors 102 and 103 are provided symmetrically with respect to the direction in which the intake air flows with the heating resistor 101 interposed therebetween.

  In addition, the sensor 100A is configured so that, for example, the temperature difference between the temperature of the intake air and the temperature of the heating resistor 101 that is not thermally influenced by the heating resistor 101 becomes a constant value. Control heat generation. As a result, a temperature distribution corresponding to the intake air amount is formed along the flow direction of the intake air, and a temperature difference corresponding to the intake air amount is generated between the upstream and downstream temperature measuring resistors 102 and 103. A detection value corresponding to the mass flow rate of the intake air amount is obtained by using an electrical signal corresponding to this temperature difference (note that the temperature difference is determined from the temperature of the downstream resistance temperature detector 103 to the upstream resistance temperature detector 102. Defined as the reduced temperature of.)

  That is, in the no-wind state, a temperature-symmetrical temperature distribution is formed on the upstream and downstream sides of the heating resistor 101 with respect to the flow direction of the intake air, and the temperature difference between the upstream and downstream temperature measuring resistors 102 and 103 is zero. It almost agrees.

  Further, when the flow of the intake air is generated in the forward direction, the temperature decreases on the upstream side of the heating resistor 101 and the temperature increases on the downstream side of the heating resistor 101, and therefore, the upstream and downstream temperature measuring resistors 102. , 103 has a positive temperature difference, and when a flow of intake air is generated in the opposite direction, the temperature rises on the upstream side of the heating resistor 101 and decreases on the downstream side of the heating resistor 101. Therefore, a negative temperature difference is generated between the upstream and downstream resistance thermometers 102 and 103.

  By the way, according to the conventional air flow rate measuring apparatus 100, the correlation between the temperature difference and the air flow rate (hereinafter referred to as the temperature difference-flow rate characteristic) is as shown in FIG. Convex in the direction of air flow in the direction, convex down in the range of negative air flow and air flow in the reverse direction, and the points of temperature difference = zero and air flow rate = zero It is point-symmetric with respect to the center.

  Thereby, for example, when the flow of the intake air in the intake passage pulsates in accordance with the opening / closing of the valve of the internal combustion engine, the pulsation average value of the intake air amount is detected as a numerical value that is biased to the minus side with respect to the true value. Therefore, in order to eliminate the shift of the detected value to the minus side due to the detection of the pulsation average value biased to the minus side, the air flow rate measuring device 100 is linear in the intake passage as shown in FIG. A configuration in which an internal flow path 105 that bypasses the flow is formed and the sensor 100A is arranged in the internal flow path 105 is widely adopted.

  In other words, when the flow path length when the air flow path is not taken into the internal flow path 105 and goes straight through the intake path is L1, and the flow path length of the internal flow path 105 is L2, the air flow rate measuring device 100 is an internal part that bypasses the linear flow. By forming the flow path 105 and arranging the sensor 100A in the internal flow path 105, a correction function for increasing the detection value according to L2 / L1 is provided.

  However, even if the shift of the detected value to the minus side is eliminated by arranging the sensor 100A in the internal flow path 105, the detected value is on the minus side or the plus side when the air flow measuring device 100 is incorporated in a vehicle and used. It will shift to and will contain errors. That is, the mode of air cleaner and the pulsation condition are different for each vehicle, and an error of the detection value occurs due to this difference (in the following description, when the air flow rate measuring device is incorporated in a vehicle and used, An error that occurs due to a difference in the mode of air cleaner and pulsation conditions for each vehicle is called an application error.)

  Here, in Patent Document 1, the distance from the heating resistor in the air flow direction is made different between the upstream temperature measuring resistor and the downstream temperature measuring resistor, or the shape of the heating resistor is set upstream. The thermal effect of the heating resistor on the upstream resistance temperature detector and the thermal effect of the heating resistor on the downstream resistance temperature detector are different from each other in the no wind condition. A configuration to be applied is disclosed. Patent Document 2 discloses that the thermal characteristics of the upstream and downstream resistance thermometers are made different by connecting a resistor not thermally affected by the heating resistor to the downstream resistance thermometer. A configuration is disclosed.

However, according to the configuration of Patent Document 1, in order to eliminate the application error, for each vehicle, the distance between the heating resistor and each of the upstream and downstream temperature measuring resistors is set, or the shape of the heating resistor is set. Need to be set. Moreover, according to the structure of patent document 2, in order to eliminate an application error, it is necessary to change the resistor connected to a downstream resistance temperature sensor for every vehicle.
For this reason, even if which structure of patent document 1 and 2 is employ | adopted, in order to eliminate an application error, it is necessary to prepare an enormous variety of sensors, and it is complicated as a solution for an application error.

Japanese Patent No. 2666163 Japanese Patent No. 3718198

  The present invention has been made to solve the above-described problems, and an object of the present invention is to facilitate the elimination of application errors in a thermal air flow measurement device that measures the flow rate of intake air. .

[Means of Claim 1]
According to the first aspect of the present invention, the air flow rate measuring device measures the flow rate of the air sucked into the internal combustion engine by generating a heat transfer phenomenon with the air sucked into the internal combustion engine. In addition, the air flow rate measuring device includes a heating resistor that generates heat when energized, an upstream temperature measuring resistor that is disposed upstream of the heating resistor and is thermally affected by the heating resistor, and a downstream of the heating resistor. And a downstream resistance temperature detector which is arranged on the side and receives thermal influence from the heating resistor.

  The heating resistor has three or more terminals for receiving energization, and when the heating resistor is energized through the three or more terminals, when the air is not flowing, the upstream side measurement is performed. The thermal effect that the temperature resistor receives from the heating resistor is different from the thermal effect that the downstream temperature measuring resistor receives from the heating resistor.

  By providing three or more terminals to the heating resistor and energizing the heating resistor through these terminals, the resistance portion close to the upstream resistance thermometer and the downstream resistance resistor among the heating resistors It is possible to generate a difference in heat generation between the resistance portion and the resistance portion close to. In other words, for example, by connecting a variable resistor in series to each of the resistance parts close to the upstream and downstream resistance thermometers, the resistance value of each variable resistor can be set freely, so that the upstream temperature measurement The calorific value difference between the resistance portion close to the resistor and the resistance portion close to the downstream resistance temperature detector can be freely manipulated.

For this reason, the thermal effect that the upstream resistance temperature detector receives from the heating resistor differs from the thermal effect that the downstream resistance resistor receives from the heating resistor, so that the temperature difference that is the reference for flow rate measurement − The flow characteristics can be changed freely.
Therefore, the temperature difference-flow rate characteristic can be easily changed to one suitable for eliminating the application error, so that it is possible to easily eliminate the application error without arranging a huge number of types of air flow measuring devices. it can.

[Means of claim 2]
According to the means of claim 2, the air flow rate measuring device includes a semiconductor substrate having a cavity and having a surface covered with an electrical insulating film, and includes a heating resistor, an upstream temperature measuring resistor, and a downstream temperature measuring resistor. Is provided as a semiconductor film on a membrane that is a part of the electrical insulating film and covers the cavity.
The temperature difference-flow rate characteristic can be changed, for example, by providing a difference in the amount of heat generated by energization of the upstream side and downstream side resistance thermometers.

  However, when providing a heating resistor or upstream or downstream resistance temperature detector on the membrane, the upstream and downstream resistance resistors are provided on the membrane closer to the periphery than the heating resistor. Heat is easily lost to the semiconductor substrate. For this reason, if there is a difference in the amount of heat generated by the energization of the upstream and downstream resistance thermometers, it is necessary to increase the energization amount to the upstream and downstream resistance thermometers. Will become bigger.

  On the other hand, when there is a difference in the amount of heat generated in the heating resistor, the power consumption does not change much. For this reason, it is possible to change the temperature difference-flow rate characteristic without increasing the power consumption by providing a difference in the amount of heat generated in the heating resistor.

[Means of claim 3]
According to the third aspect of the present invention, the upstream side resistance temperature detector and the downstream side resistance temperature detector are provided in line symmetry with respect to the direction of air flow with the heating resistor interposed therebetween.
When a heating resistor, upstream side, or downstream side resistance temperature detector is installed on the membrane, the resistance value of the heating resistor, upstream side, or downstream side resistance temperature detector is likely to fluctuate due to the piezoresistance effect due to the stress generated in the membrane. As a result, the measurement accuracy may be reduced.

  Therefore, the upstream and downstream resistance thermometers are provided symmetrically with respect to the direction of air flow with the heating resistor interposed therebetween. As a result, a piezoresistance effect occurs symmetrically with respect to the direction of air flow in the heating resistor itself, and the variation in resistance value is offset. Similarly, the piezoresistive effect is generated symmetrically between the upstream and downstream resistance temperature detectors with respect to the direction of air flow, and the fluctuation of the resistance value is offset. For this reason, by providing the upstream and downstream resistance thermometers symmetrically with respect to the air flow direction across the heating resistor, the resistance value fluctuations of the heating resistor and upstream and downstream resistance resistors are offset. Thus, the possibility of a decrease in measurement accuracy can be reduced.

It is sectional drawing which shows the inside of an air flow measuring device (Example). It is a top view which shows arrangement | positioning of the heating resistor on a membrane, an upstream side, and a downstream temperature sensing resistor (Example). (A) is a plan view of the sensor, (b) is a cross-sectional view of the sensor, and (c) is a cross-sectional view showing elements, wiring portions, and electrodes on the semiconductor substrate (Example). (A) is a circuit block diagram for outputting a signal according to a temperature difference by the upstream side and downstream side resistance temperature detectors, and (b) is a circuit block diagram for controlling the heat generation of the heating resistor. (Example). It is a side view of an air flow rate measuring apparatus (Example). (A) is a front view of an air flow measuring device, (b) is a bottom view of the air flow measuring device (Example). It is explanatory drawing which shows the relationship between the pulsation average value of intake air amount, and the detected value of intake air amount (Example). It is a characteristic view which shows the change of a temperature difference-flow rate characteristic (Example). It is explanatory drawing which shows the relationship between the pulsation average value of intake air amount, and the detected value of intake air amount (Example). It is a characteristic view which shows the change of a temperature difference-flow rate characteristic (Example). It is explanatory drawing which shows the relationship between the pulsation average value of intake air amount, and the detected value of intake air amount (Example). It is a top view which shows arrangement | positioning of the heating resistor on a membrane, an upstream, and a downstream temperature sensing resistor (modification). It is a top view which shows arrangement | positioning of the heating resistor on a membrane, an upstream, and a downstream temperature sensing resistor (modification). It is a top view which shows arrangement | positioning of the heating resistor on a membrane, an upstream side, and a downstream temperature sensing resistor (conventional example). It is a characteristic view which shows a temperature difference-flow rate characteristic (conventional example). It is sectional drawing which shows the inside of an air flow measuring device (conventional example).

  The air flow rate measuring device of the embodiment measures the flow rate of air sucked into the internal combustion engine by generating a heat transfer phenomenon between the air sucked into the internal combustion engine. In addition, the air flow rate measuring device includes a heating resistor that generates heat when energized, an upstream temperature measuring resistor that is disposed upstream of the heating resistor and is thermally affected by the heating resistor, and a downstream of the heating resistor. And a downstream resistance temperature detector which is arranged on the side and receives thermal influence from the heating resistor.

  The heating resistor has three or more terminals for receiving energization, and when the heating resistor is energized through the three or more terminals, when the air is not flowing, the upstream side measurement is performed. The thermal effect that the temperature resistor receives from the heating resistor is different from the thermal effect that the downstream temperature measuring resistor receives from the heating resistor.

The air flow rate measuring device includes a semiconductor substrate having a cavity and having a surface covered with an electric insulating film. The heating resistor, the upstream temperature measuring resistor, and the downstream temperature measuring resistor are included in the electric insulating film. It is provided as a semiconductor film on a membrane that covers the cavity.
Furthermore, the upstream side resistance temperature detector and the downstream side resistance temperature detector are provided symmetrically with respect to the direction of air flow with the heating resistor interposed therebetween.

[Configuration of Example]
The structure of the air flow rate measuring apparatus 1 of an Example is demonstrated using FIGS.
For example, the air flow rate measuring device 1 is arranged so as to protrude into an intake path (not shown) to the internal combustion engine and is used for measuring the intake air amount. The air flow rate measuring device 1 takes in part of the air flowing through the intake passage, and directly measures the mass flow rate as the intake air amount by generating a heat transfer phenomenon with the taken-in air. is there.

  That is, the air flow rate measuring device 1 is obtained from a thermal sensor 2 that generates a detection value corresponding to a mass flow rate by generating a heat transfer phenomenon with intake air, a housing 3 that houses the sensor 2, and a sensor 2. A connector 4 or the like for outputting the detected value to the electronic control unit (ECU) is provided (see FIGS. 1, 5 and 6). Then, the ECU grasps the intake air amount based on the detection value obtained from the air flow rate measuring device 1, and executes various control processes such as fuel injection control based on the grasped air intake amount.

  The sensor 2 includes a heating resistor 6 that generates heat when energized, an upstream temperature measuring resistors 7 and 8 that are arranged on the upstream side of the heating resistor 6, and that are thermally affected by the heating resistor 6, and a heating resistor. 6 and the downstream resistance temperature detectors 9 and 10 which are arranged on the downstream side of the heater 6 and receive thermal influence from the heating resistor 6 (see FIG. 2 and the like).

  In addition, the sensor 2 includes a semiconductor substrate 14 having a cavity 12 and having a surface covered with an electrical insulating film 13, and includes a heating resistor 6, upstream temperature measuring resistors 7 and 8, and a downstream temperature measuring resistor 9. 10 is a part of the electrical insulating film 13 and is provided as a semiconductor film on the membrane 15 covering the cavity 12 (see FIGS. 2 and 3). The upstream temperature measuring resistors 7 and 8 and the downstream temperature measuring resistors 9 and 10 are provided in line symmetry with respect to the flow direction of the intake air with the heating resistor 6 interposed therebetween.

  Here, the upstream resistance temperature detectors 7 and 8 and the downstream resistance temperature detectors 9 and 10 form a bridge circuit 17 (see FIG. 4 and the like). The bridge circuit 17 includes, for example, the upstream side resistance thermometer 7 and the downstream side resistance thermometer 9 in series, and the downstream side resistance thermometer 9 has a higher potential than the upstream side resistance thermometer 7. The upstream side resistance thermometer 8 and the downstream side resistance thermometer 10 are arranged in series so that the upstream side resistance thermometer 8 is higher than the downstream side resistance thermometer 10. It is formed so as to be arranged on the potential side.

  The heating resistor 18 including the heating resistor 6 is provided on the semiconductor substrate 29 and has no temperature correlation with the heating resistor 6, and the heating resistor 6 on the semiconductor substrate 14. The bridge circuit 23 is formed together with the temperature sensitive resistor 21 provided at a position not affected by heat (see FIG. 4 and the like). Here, the temperature sensitive resistor 21 is provided as a silicon semiconductor film on the semiconductor substrate 14 via the electrical insulating film 13, and has a thermal influence on the flow of intake air that is not heated by the heating resistor 6. To receive.

  The bridge circuit 23 includes, for example, the heating resistor 18 and the resistor 22 in series, and the heating resistor 18 is arranged on the higher potential side than the resistor 22. The temperature sensitive resistor 21 is arranged in series, and the temperature sensitive resistor 21 is arranged on the higher potential side than the resistor 20.

  The sensor 2 also outputs a comparator 24 that outputs a signal corresponding to the potential difference in the bridge circuit 17 and a comparator that outputs a signal to the amplifier 25 that controls energization to the bridge circuit 23 according to the potential difference in the bridge circuit 23. 26. Here, the potential difference in the bridge circuit 17 refers to the potential at the connection between the upstream resistance temperature detector 7 and the downstream resistance temperature detector 9, the upstream resistance temperature detector 8, and the downstream resistance temperature detector 10. It is the difference from the potential of the connection part. The potential difference in the bridge circuit 23 is a difference between the potential at the connection portion between the heating resistor 18 and the resistor 22 and the potential at the connection portion between the resistor 20 and the temperature sensitive resistor 21.

  As described above, in the sensor 2, the bridge circuit 23, the comparator 26, and the amplifier 25 cause the temperature difference between the intake air and the heating resistor 6 that is not thermally affected by the heating resistor 6 to be a constant value. Thus, energization to the heating resistor 6 is controlled. As a result, a temperature distribution corresponding to the intake air amount is formed along the direction in which the intake air flows, and the upstream side resistance temperature detectors 7 and 8 and the downstream side resistance temperature detectors 9 and 10 correspond to the intake air amount. Temperature difference occurs.

  Then, the bridge circuit 17 and the comparator 24 process the potential difference corresponding to the temperature difference as a signal indicating the detected value of the intake air amount and output it to the ECU (in the following description, the temperature difference is measured on the downstream side). It is defined as the temperature of the temperature resistors 9 and 10 subtracted from the temperature of the upstream resistance resistors 7 and 8).

  The comparators 24 and 26, the amplifier 25, and the like are provided on a semiconductor substrate 29 that is separate from the semiconductor substrate 14 (see FIG. 3 and the like). The semiconductor substrates 14 and 29 are supported by being bonded to a resin support 32 by adhesives 30 and 31, respectively.

  Further, the element on the semiconductor substrate 14 and the element on the semiconductor substrate 29 include a wiring portion and an electrode provided on each of the semiconductor substrates 14 and 29, and an electrode on the semiconductor substrate 14 and an electrode on the semiconductor substrate 29. Are electrically connected by a bonding wire 33 or the like (see FIG. 3 and the like). Furthermore, the element and the wiring part are covered and protected by a protective film 34, and the electrode and the bonding wire 33 are covered and protected by a protective agent 35.

  The housing 3 opens, for example, toward the upstream side of the intake passage, and allows the intake port 38 to take in a part of the intake air flowing in the forward direction in the intake passage, the intake air taken in from the intake port 38, and the sensor 2. And a discharge port 40 that opens toward the downstream side of the intake passage and returns intake air that has been taken in from the intake port 38 and passed through the sensor 2 to the intake passage (FIGS. 1 and 2). 5 and FIG. 6 etc.). The sensor 2 generates a heat transfer phenomenon between the intake air taken in from the suction port 38 and generates a detection value corresponding to the mass flow rate.

  In the following description, with respect to the flow direction of the intake air in the internal flow path 39, the suction port 38 is the upstream end, the discharge port 40 is the downstream end, and the flow direction from the suction port 38 toward the discharge port 40 is the forward direction. The direction of flow from the discharge port 40 toward the suction port 38 is the reverse direction.

  The internal flow path 39 contains, for example, a suction flow path 41 continuous downstream from the suction opening 38, a discharge flow path 42 continuous upstream from the discharge opening 40, the sensor 2, and the suction flow path 41 and discharge. A circulation channel 43 that circulates so as to connect the channel 42 is provided.

  The suction channel 41 is provided so as to extend linearly from the suction port 38 to the downstream side, and the flow in the suction channel 41 is parallel to the linear flow in the intake channel. A dust discharge channel 44 is connected to the downstream end of the suction channel 41 to allow the dust contained in the intake air taken in from the suction port 38 to go straight ahead and be discharged. Further, a dust discharge port 45 is formed at the downstream end of the dust discharge channel 44, and the dust discharge channel 44 tapers toward the dust discharge port 45.

  The circulation channel 43 is provided, for example, in a substantially C shape, and is connected to the suction channel 41 and the discharge channel 42 at the upstream end and the downstream end, respectively, and sucks the intake air taken in from the suction port 38 into the suction channel 41. To the discharge channel 42. Further, the sensor 2 is accommodated in a portion of the circulation channel 43 that flows in a direction opposite to the flow direction in the suction channel 41.

  Here, the circulation channel 43 is branched from a linear channel composed of the suction channel 41 and the dust discharge channel 44 at the downstream end of the suction channel 41. That is, the suction channel 41 is branched into the circulation channel 43 and the dust discharge channel 44 at the downstream end, and the dust travels straight from the suction channel 41 to the dust discharge channel 44 due to inertial force. The intake air is discharged from the outlet 45 to the intake passage, and the intake air flows from the intake passage 41 into the circulation passage 43 while changing the flow direction.

  The discharge flow path 42 is connected to the downstream end of the circumferential flow path 43 and is bent so that the forward flow at the downstream end of the circumferential flow path 43 is swung at a substantially right angle, and the discharge port 40 is the downstream end of the bending. It is. Further, the discharge channel 42 branches into two so as to straddle the suction channel 41, and the discharge ports 40 are formed at two locations on both sides of the suction channel 41. That is, the discharge flow channel 42 is branched into two so as to be mirror-symmetric with respect to the cut surface including the flow channel axis of the suction flow channel 41 and the circulation flow channel 43.

  As described above, the internal flow path 39 is provided so as to bypass the linear flow in the intake passage, and by allowing the intake air taken in from the suction port 38 to bypass the linear flow in the intake passage, A correction function for increasing the detection value of the sensor 2 is provided.

  That is, assuming that the flow path length when the air flow is straight in the intake path without being taken into the internal flow path 39 is L1, and the flow path length of the internal flow path 39 is L2, the air flow rate measuring device 1 is an internal part that bypasses the linear flow. By forming the flow path 39 and arranging the sensor 2 in the internal flow path 39, it has a correction function of increasing the detection value according to L2 / L1. According to this correction function, the detected value can be increased as L2 / L1 is increased.

  When air flows in the reverse direction in the intake passage, a part of the intake air flows into the internal flow path 39 from the discharge port 40, and the intake air that flows in from the discharge port 40 passes through the sensor 2, For example, the suction port 38 returns to the intake path.

Next, the heating resistor portion 18 will be described in detail.
The heating resistor 18 includes an upstream heating resistor 48 close to the upstream temperature measuring resistors 7 and 8 and a downstream temperature measuring resistor 9 in the resistance wiring included in the heating resistor 6 in the direction in which the intake air flows. 10 includes a downstream heating resistor 49 and variable resistors 50 and 51, and the upstream and downstream heating resistors 48 and 49 and the variable resistors 50 and 51 form a bridge circuit 52. (Refer to FIG. 2 and FIG. 4 etc.).

  Here, the heating resistor 6 has three terminals 54 to 56 for receiving energization, and receives energization via the terminals 54 to 56. The terminals 54 to 56 form part of the wiring portion on the membrane 15. On the membrane 15, the terminal 54 is connected to the upstream heating resistor 48, and the terminal 55 is connected to the downstream heating resistor 49. Further, the terminal 56 is provided between the upstream side and the downstream side resistance temperature detectors 7 to 10 in the flow direction of the intake air, and is connected to both the upstream side and the downstream side resistance temperature detectors 7 to 10. Connected.

  The upstream and downstream heating resistors 48 and 49 are connected to the emitter of the amplifier 25 via the wiring 57 on the high potential side. Furthermore, the variable resistors 50 and 51 are provided on the semiconductor substrate 29.

  In the bridge circuit 52, for example, the upstream heating resistor 48 and the variable resistor 50 are arranged in series, and the upstream heating resistor 48 is arranged on the higher potential side than the variable resistor 50. Further, the downstream heating resistor 49 and the variable resistor 51 are formed in series, and the downstream heating resistor 49 is arranged on the higher potential side than the variable resistor 51. The variable resistors 50 and 51 are connected to the resistor 22 on the low potential side.

  With the configuration described above, when the heating resistor 18 is energized via the amplifier 25, the current flows through the branch including the upstream heating resistor 48 and the variable resistor 50 in series, the downstream heating resistor 49, and The variable resistor 51 is divided in parallel with a branch that includes the variable resistor 51 in series. Thereby, by setting the resistance values of the variable resistors 50 and 51 freely, the heat generation amounts in the upstream and downstream heating resistors 48 and 49 can be freely controlled.

  For this reason, the thermal effect that the upstream resistance thermometers 7 and 8 receive from the heating resistor 6 and the thermal influence that the downstream resistance thermometers 9 and 10 receive from the heating resistor 6 are different from each other in the windless state. Thus, it is possible to freely change the temperature difference-flow rate characteristic which is a reference for flow rate measurement. As a result, by changing the temperature difference-flow rate characteristic, the detected value of the intake air amount can be freely shifted to the plus side or the minus side, so that, for example, the shift of the detected value due to an application error can be offset. .

  For example, in the temperature difference-flow rate characteristic A before setting the resistance values of the variable resistors 50 and 51, as shown in FIG. 7, the air flow rate is positive and the air flows in the forward direction. It is convex and convex downward in the range where the air flow rate is negative and air is flowing in the opposite direction, and it is point-symmetric about the point where temperature difference = zero and air flow rate = zero .

  Here, let us consider a case in which pulsation is performed with the same amplitude QA on the large side larger than Q and the smaller side smaller than Q around Q, which is a positive numerical value. The pulsation average value Q and the pulsation area (Q-QA) to (Q + QA) are included in the flow rate range in which the correlation between the temperature difference and the flow rate is almost linear in the temperature difference-flow rate characteristic A. (Refer to “pulsation of intake air amount” shown in FIG. 7).

  In this case, assuming that there is no response delay due to the heat capacity or the like, the temperature difference pulsates with the same amplitude TA on the large side of T and the small side of T, centering on the positive value T (FIG. 7). (Refer to “Pulse of ideal temperature difference in complete response”). Note that T as the pulsation average value of the temperature difference is obtained by applying Q as a numerical value of the intake air amount to the temperature difference-flow rate characteristic A, and the amplitude TA is also obtained from the amplitude QA.

  Then, the sensor 2 discretely samples the temperature difference accompanied by a response delay or the like, and detects that a pulsation of the temperature difference is generated with an amplitude TA ′ smaller than the amplitude TA, where T is a pulsation average value. (See “Pulse of temperature difference detected by sensor” shown in FIG. 7). As a result, the detected value of the intake air amount becomes Q by applying T as the pulsation average value to the temperature difference-flow rate characteristic A.

  As described above, when the pulsation of the intake air amount occurs in the flow rate range where the correlation between the temperature difference and the flow rate characteristic can be regarded as almost linear in the temperature difference-flow rate characteristic A, the intake air amount is measured based on the temperature difference-flow rate characteristic A. According to the above, both the detected value of the intake air amount and the pulsation average value of the intake air amount are substantially equal to Q.

For such a temperature difference-flow rate characteristic A, the resistance values of the variable resistors 50 and 51 are set so that the heat generation amount of the downstream heating resistor 49 is larger than the heat generation amount of the upstream heating resistor 48. For example, consider a case where the temperature difference-flow rate characteristic A is changed to the temperature difference-flow rate characteristic B shown in FIG.
Here, the temperature difference-flow rate characteristic B has a larger air flow rate than the temperature difference-flow rate characteristic A because the amount of heat generated by the downstream side heating resistor 49 is larger than the amount of heat generated by the upstream side heating resistor 48. The upward convexity becomes remarkable in the range, and the downward convexity is relaxed in the negative air flow range.

  Accordingly, when the same pulsation as that shown in FIG. 7 is generated with respect to the intake air amount, the detected value of the intake air amount is measured according to the measurement of the intake air amount based on the temperature difference-flow rate characteristic B as shown in FIG. Becomes larger than the pulsation average value of the intake air amount.

  That is, when the same pulsation as shown in FIG. 7 is generated with respect to the intake air amount (see “pulsation of the intake air amount” shown in FIG. 9), the temperature difference assuming no response delay is a positive numerical value. Pulsing at different amplitudes T1Ab and T1As on the large side of T1 and on the small side of T1 with T1 as the center (see “Pulse of Ideal Temperature Difference at Complete Response” shown in FIG. 9). Note that T1 as the pulsation average value of the temperature difference is obtained by applying Q as the value of the intake air amount to the temperature difference-flow rate characteristic B, and the amplitudes T1Ab and T1As are respectively the values of the intake air amount as Q + QA, This is obtained by applying Q-QA to the temperature difference-flow rate characteristic B.

  Here, since the form of the temperature difference-flow rate characteristic B has the above-described characteristics with respect to the form of the temperature difference-flow rate characteristic A, a remarkable magnitude can be seen between the amplitudes T1Ab and T1As. The amplitude T1Ab is larger than the amplitude T1As.

  Then, the sensor 2 discretely samples the temperature difference accompanied by a response delay or the like, so that the pulsation of the temperature difference has an amplitude T1A ′ smaller than (T1Ab + T1As) / 2, where T1 ′ larger than T1 is a pulsation average value. It is detected that it has occurred (see “Pulsation of temperature difference detected by sensor” shown in FIG. 9). As a result, the detected value of the intake air amount is obtained as Q1 larger than Q by applying T1 ′ as the pulsation average value to the temperature difference-flow rate characteristic B.

  Thus, according to the measurement of the intake air amount based on the temperature difference-flow rate characteristic B, the detected value of the intake air amount becomes larger than the pulsation average value of the intake air amount, so that the detected value of the intake air amount is shifted to the plus side. Can do. Therefore, according to the measurement of the intake air amount based on the temperature difference-flow rate characteristic B, when the detected value is shifted to the minus side due to an application error with respect to the intake air amount, the detected value of the intake air amount is shifted to the plus side. The shift of the detected value to the negative side due to the application error can be canceled out.

Further, the resistance values of the variable resistors 50 and 51 are set so that the heat generation amount of the upstream side heat generation resistor 48 is larger than the heat generation amount of the downstream side heat generation resistor 49. Consider the case of changing to the temperature difference-flow rate characteristic C shown in FIG.
Here, the temperature difference-flow rate characteristic C is higher in air flow rate than the temperature difference-flow rate characteristic A because the heat generation amount of the upstream heating resistor 48 is larger than the heat generation amount of the downstream heating resistor 49. The upward convexity is alleviated in the range, and the downward convexity is prominent in the negative air flow range.

  As a result, when the same pulsation as shown in FIG. 7 is generated with respect to the intake air amount, the detected value of the intake air amount is measured according to the measurement of the intake air amount based on the temperature difference-flow rate characteristic C as shown in FIG. Becomes smaller than the pulsation average value of the intake air amount.

  That is, when the same pulsation as shown in FIG. 7 occurs with respect to the intake air amount (see “intake air pulsation” shown in FIG. 11), the temperature difference assumed to have no response delay is substantially equal to zero. It pulsates with different amplitudes T2Ab and T2As on the large side of T2 and the small side of T2, centering on the numerical value T2 (see “Pulse of Ideal Temperature Difference at Complete Response” shown in FIG. 11). Note that T2 as the pulsation average value of the temperature difference is obtained by applying Q as the value of the intake air amount to the temperature difference-flow rate characteristic C, and the amplitudes T2Ab and T2As are respectively the values of the intake air amount as Q + QA, This is obtained by applying Q-QA to the temperature difference-flow rate characteristic C.

  Here, since the form of the temperature difference-flow rate characteristic C has the above-described characteristics with respect to the form of the temperature difference-flow rate characteristic A, a remarkable magnitude can be seen between the amplitudes T2Ab and T2As. The amplitude T2Ab is smaller than the amplitude T2As.

  Then, the sensor 2 discretely samples the temperature difference accompanied by a response delay or the like, so that the pulsation of the temperature difference has an amplitude T2A ′ smaller than (T2Ab + T2As) / 2 with T2 ′ smaller than T2 as a pulsation average value. It is detected that it has occurred (see “Pulsation of temperature difference detected by sensor” shown in FIG. 11). As a result, the detected value of the intake air amount is obtained as Q2 smaller than Q by applying T2 ′ as the pulsation average value to the temperature difference-flow rate characteristic C.

  Thus, according to the measurement of the intake air amount based on the temperature difference-flow rate characteristic C, the detected value of the intake air amount becomes smaller than the pulsation average value of the intake air amount, so that the detected value of the intake air amount is shifted to the minus side. Can do. Therefore, according to the measurement of the intake air amount based on the temperature difference-flow rate characteristic C, when the detected value is shifted to the positive side due to an application error with respect to the intake air amount, the detected value of the intake air amount is shifted to the negative side. The shift of the detected value to the plus side due to the application error can be canceled out.

[Effects of Examples]
The air flow rate measuring device 1 of the embodiment is arranged on the heating resistor 6 that generates heat when energized, and on the upstream side and the downstream side of the heating resistor 6, respectively, on the upstream side and the downstream side that are thermally affected by the heating resistor 6. Side resistance thermometers 7 to 10 are provided. The heating resistor 6 has three terminals 54 to 56 on the membrane 15 for receiving energization, and the heating resistor 6 is energized through the terminals 54 to 56 so that in the windless state, the upstream side The thermal effect received by the side resistance thermometers 7 and 8 from the heating resistor 6 is different from the thermal effect received by the downstream temperature measuring resistors 9 and 10 from the heating resistor 6.

  The heating resistor 6 is provided with three terminals 54 to 56, and the heating resistor 6 is energized through the terminals 54 to 56, whereby the upstream and downstream temperature measuring resistors 7 to 10 of the heating resistor 6. It is possible to generate a difference in heat generation between the upstream and downstream heating resistors 48 and 49 close to each other. In other words, the variable resistors 50 and 51 are connected in series to the upstream and downstream heating resistors 48 and 49, respectively, and the resistance values of the variable resistors 50 and 51 are set freely, so that the upstream and downstream The difference in the amount of heat generated between the side heating resistors 48 and 49 can be manipulated freely.

  For this reason, the thermal effect received by the upstream resistance thermometers 7 and 8 from the heating resistor 6 and the thermal effect received by the downstream resistance thermometers 9 and 10 from the heating resistor 6 are made different from each other. It is possible to freely change the temperature difference-flow rate characteristics as a measurement reference. As a result, the detected value of the intake air amount can be freely shifted to the plus side or the minus side by changing the temperature difference-flow rate characteristic, and the shift of the detected value due to the application error can be offset.

  Thus, by providing the heating resistor 6 with the three terminals 54 to 56 and energizing the heating resistor 6 through the terminals 54 to 56, the temperature difference-flow rate characteristic is suitable for eliminating the application error. Can be easily changed to one. Therefore, the application error can be easily eliminated without preparing an enormous number of products for the air flow rate measuring device 1.

The air flow rate measuring device 1 includes a semiconductor substrate 14 having a cavity 12 and having a surface covered with an electrical insulating film 13, and includes a heating resistor 6, upstream temperature measuring resistors 7, 8 and downstream temperature measuring resistors. The bodies 9 and 10 are provided as a semiconductor film on a membrane 15 that is a part of the electrical insulating film 13 and covers the cavity 12.
The temperature difference-flow rate characteristic can be changed, for example, by providing a difference in the amount of heat generated by energization of the upstream and downstream resistance thermometers 7 to 10.

  However, since the upstream and downstream resistance thermometers 7 to 10 are provided on the membrane 15 on the peripheral side of the heating resistor 6, the semiconductor substrate 14 having a thickness is easily deprived of heat. For this reason, if it is going to give the difference in the emitted-heat amount by each energization of the upstream and downstream side resistance thermometers 7-10, the energization amount to the upstream side and downstream side resistance thermometers 7-10 will be enlarged. It is necessary and power consumption becomes large.

  On the other hand, when the amount of heat generation is made different between the upstream and downstream heating resistors 48 and 49 in the heating resistor 6, the power consumption does not change much. For this reason, by providing a difference in the amount of heat generated in the heating resistor 6, the temperature difference-flow rate characteristic can be changed without increasing the power consumption.

Further, the upstream temperature measuring resistors 7, 8 and the downstream temperature measuring resistors 9, 10 are provided in line symmetry with respect to the direction of intake air flow with the heating resistor 6 interposed therebetween.
Resistance values of the heating resistor 6 and the upstream and downstream temperature measuring resistors 7 to 10 are likely to fluctuate due to the piezoresistive effect due to the stress generated in the membrane 15, and the measurement accuracy may be reduced.

  Therefore, the upstream and downstream resistance thermometers 7 to 10 are provided symmetrically with respect to the flow direction of the intake air with the heating resistor 6 interposed therebetween. As a result, a piezoresistance effect is generated symmetrically with respect to the direction in which the intake air flows in the heating resistor 6 itself, and the variation in resistance value is offset. Similarly, the piezoresistive effect is generated symmetrically between the upstream resistance temperature detectors 7 and 8 and the downstream resistance temperature detectors 9 and 10 with respect to the direction in which the intake air flows, and the fluctuation of the resistance value is offset.

  For this reason, by providing the upstream side resistance thermometers 7 and 8 and the downstream side resistance thermometers 9 and 10 symmetrically with respect to the flow direction of the intake air with the heating resistor 6 interposed therebetween, The fluctuation of the resistance value of the side and downstream side resistance temperature detectors 7 to 10 can be offset and the possibility of a decrease in measurement accuracy can be reduced.

Although the semiconductor substrate 14 is supported by being bonded to a resin support 32 by an adhesive 30 (see FIG. 3), the linear expansion coefficient differs greatly between the semiconductor substrate 14 and the support 32. The semiconductor substrate 14 is deformed by adhesion, and stress is easily generated in the membrane 15.
Further, although the electrodes and the bonding wires 33 are covered and protected by the protective agent 35 (see FIG. 3), the linear expansion coefficient differs greatly between the semiconductor substrate 14 and the protective agent 35. Even by application, the semiconductor substrate 14 is deformed and stress is easily generated in the membrane 15.

  For this reason, the configuration in which the upstream side resistance thermometers 7 and 8 and the downstream side resistance thermometers 9 and 10 are provided in line symmetry with respect to the flow direction of the intake air with the heating resistor 6 interposed therebetween is affected by the piezoresistance effect. Is extremely effective in offsetting the above and suppressing the decrease in measurement accuracy.

[Modification]
The aspect of the air flow rate measuring device 1 is not limited to the embodiment, and various modifications can be considered.
For example, according to the air flow rate measuring apparatus 1 of the embodiment, the heating resistor 6 is provided with the three terminals 54 to 56, and the heating resistor 6 is energized through the terminals 54 to 56. Alternatively, as shown in FIG. 13, four terminals 54 to 56 and 59 are provided in the heating resistor 6 and the heating resistor 6 is energized through the terminals 54 to 56 and 59, as in the embodiment. The temperature difference-flow rate characteristic can be freely changed.

  In this case, as shown in FIG. 12, two wirings 57 are arranged between the upstream heating resistor 48 and the downstream heating resistor 49, the terminal 56 is connected to one wiring 57, and the other wiring 57 is connected. The two terminals 57 may be connected to both the upstream and downstream heating resistors 48 and 49.

Further, as shown in FIG. 13, two wirings 57 are arranged between the upstream heating resistor 48 and the downstream heating resistor 49, the terminal 56 is connected to one wiring 57 and the other wiring 57 is connected. The terminal 59 may be connected, one wiring 57 may be connected only to the upstream side heating resistor 48, and the other wiring 57 may be connected only to the downstream side heating resistor 49.
Further, even when five or more terminals are provided on the heating resistor 6, the temperature difference-flow rate characteristic can be freely changed in the same manner.

DESCRIPTION OF SYMBOLS 1 Air flow measuring device 6 Heating resistor 7 Upstream side resistance temperature detector 8 Upstream side resistance temperature detector 9 Downstream side resistance temperature detector 10 Downstream side resistance temperature detector 12 Cavity 13 Electrical insulating film 14 Semiconductor substrate 15 Membrane 54- 56, 59 terminals

Claims (3)

In an air flow rate measuring apparatus for measuring a flow rate of air sucked into the internal combustion engine by generating a heat transfer phenomenon with the air sucked into the internal combustion engine,
A heating resistor that generates heat when energized;
An upstream resistance temperature detector that is disposed upstream of the heating resistor and receives thermal influence from the heating resistor;
A downstream resistance temperature detector disposed on the downstream side of the heating resistor and receiving thermal influence from the heating resistor;
The heating resistor has three or more terminals for receiving energization,
When the heating resistor is energized via the three or more terminals, when the air is not flowing, the thermal effect that the upstream resistance temperature detector receives from the heating resistor and the downstream side An air flow rate measuring device characterized in that a temperature measuring resistor is different from a thermal effect received from the heating resistor. The air flow rate measuring device according to claim 1,
A semiconductor substrate having a cavity and a surface covered with an electrical insulating film;
The heating resistor, the upstream resistance temperature detector, and the downstream resistance temperature detector are provided as a semiconductor film on a membrane that is a part of the electrical insulating film and covers the cavity. Air flow measuring device. In the air flow measuring device according to claim 2,
The air flow rate measuring device, wherein the upstream side resistance temperature detector and the downstream side resistance temperature detector are provided in line symmetry with respect to a direction of air flow with the heating resistor interposed therebetween.

Images