JP6747124B2 - Flow sensor - Google Patents

Description

The present invention relates to a flow rate sensor that detects a flow rate of a fluid.

2. Description of the Related Art A flow rate sensor that detects a flow rate of a fluid has been conventionally known as disclosed in Patent Document 1, for example. This type of flow rate sensor is provided with a flow rate detecting section having a heat generating section and two temperature sensing sections arranged so as to sandwich the heat generating section. The heat generating part and the two temperature sensing parts are arranged along the flow direction of the fluid, and the flow rate is calculated using the difference between the temperature detection values of the temperature sensing parts arranged on the upstream side and the downstream side of the heat generating part. ing.

However, when the fluid (for example, air) contains moisture, the specific heat value and the like change depending on the amount of moisture (that is, humidity), so that an error occurs in the detected flow rate. Such an error is not preferable particularly in applications requiring highly accurate flow rate measurement (air amount), such as fuel injection control of a vehicle internal combustion engine.

Therefore, in Patent Document 2, for example, a humidity detection unit is provided near the flow rate detection unit, and the flow rate detected by the flow rate detection unit is corrected based on the amount of water detected by the humidity detection unit, thereby improving the flow rate detection accuracy. It is disclosed to do. In this flow rate sensor, as shown in FIG. 8, the humidity detecting section J130 is arranged in series so as to be located on the upstream side of the flow rate detecting section J120 along the fluid flow direction, or as shown in FIG. The humidity detectors J130 are arranged in parallel so that they are located at least upstream of the heat generating portion of the flow rate detector J120 along the flow direction.

Japanese Patent No. 3468731 JP, 2008-157742, A

Incidentally, in the intake passage of the internal combustion engine, in addition to the fluid flow direction α in the intake stroke, a pulsating fluid flow direction β depending on the opening/closing timing of the intake valve and the exhaust valve in the compression stroke may occur.

In the configuration shown in FIG. 8, the humidity detecting unit J130 is not affected by the temperature distribution of the heat generating unit of the flow rate detecting unit J120 in the fluid flow direction α, but the humidity detecting unit J130 detects the flow rate in the fluid flow direction β. It will be affected by the temperature distribution due to the heat generating portion of the portion J120. In the configuration shown in FIG. 9, the humidity detecting unit J130 is affected by the temperature distribution of the heat generating unit of the flow rate detecting unit J120 in both the fluid flow directions α and β. Therefore, with the configurations shown in FIGS. 8 and 9, the humidity cannot be accurately measured when the fluid flow direction changes, and the flow rate detection accuracy cannot be ensured.

In view of the above points, the present invention has an object to provide a flow rate sensor capable of improving the detection accuracy of the flow rate of a fluid.

In order to achieve the above object, in the invention according to claim 1, there is at least a heat generating part (121), and a flow rate detecting part (120) for detecting the flow rate of the fluid, and the flow rate along the flow direction of the fluid. Two humidity detection units (130, 140) are provided so as to sandwich the detection unit and detect the humidity of the fluid.

As a result, even when the flow direction of the fluid changes, the humidity detection unit located upstream of the flow rate detection unit in the fluid flow direction of the two humidity detection units is affected by the heat of the heat generation unit of the flow rate detection unit. The humidity can be detected accurately. Therefore, the accuracy of flow rate detection by the flow rate sensor is improved by correcting the flow rate detected by the flow rate detection section using the detection value of the humidity detection section located upstream of the flow rate detection section in each of the different fluid flow directions. Can be made.

Note that the reference numerals in parentheses of the above-mentioned means indicate the correspondence with the specific means described in the embodiments described later.

It is a schematic diagram of an engine provided with a semiconductor device of a 1st embodiment. It is a figure which shows the fluid flow direction in an intake passage. It is a top view which shows schematic structure of a semiconductor device. It is a figure which shows the schematic structure of a flow volume detection part, and the detection value of a temperature sensing part when a fluid flow direction changes. It is a figure which shows the temperature distribution of the semiconductor device periphery when the main part of a semiconductor device and the flow direction of a fluid change. 7 is a flowchart showing the output of the humidity detection value of the semiconductor device based on the fluid flow direction. It is a figure which shows the temperature distribution of the semiconductor device periphery when the principal part of the semiconductor device of 2nd Embodiment and the fluid flow direction change. It is a figure which shows the temperature distribution of the semiconductor device periphery when the principal part of a semiconductor device of a prior art and the fluid flow direction change. It is a figure which shows the temperature distribution of the semiconductor device periphery when the principal part of a semiconductor device of a prior art and the fluid flow direction change.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following respective embodiments, the same or equivalent portions are designated by the same reference numerals in the drawings.

(First embodiment)
Hereinafter, an embodiment in which the flow rate sensor of the present invention is used for detecting the intake flow rate of an internal combustion engine will be described based on FIGS.

As shown in FIG. 1, the internal combustion engine 10 includes a piston 11, a combustion chamber 12, an intake valve 13, an exhaust valve 14, a spark plug 15, and the like. An intake passage 16 and an exhaust passage 17 are connected to the combustion chamber 12. The intake air to the combustion chamber 12 is supplied from the intake passage 16, and the exhaust air from the combustion chamber 12 is discharged to the exhaust passage 13.

The intake passage 16 is provided with a fuel injection valve 18 for injecting fuel into the air flowing through the intake passage 16, a throttle valve 19 for adjusting the air flow rate of the intake passage 16, and a flow rate sensor 100 for detecting the air flow rate of the intake passage 16. ing.

As shown in FIG. 2, in the intake passage 16, the fluid flow direction changes depending on the stroke of the internal combustion engine 10. Specifically, there is a fluid flow direction α toward the combustion chamber 12 of the internal combustion engine 10 and a fluid flow direction β toward the opposite side of the combustion chamber 12 of the internal combustion engine 10. The fluid flow direction α and the fluid flow direction β are opposite to each other.

In the intake stroke of the internal combustion engine 10, the fluid flows in the fluid flow direction α. On the other hand, in the compression stroke of the internal combustion engine 10, when the exhaust valve 14 is closed and there is a slight gap in the intake valve 13, pulsation occurs and the fluid flows in the fluid flow direction β.

As shown in FIG. 3, the flow rate sensor 100 is configured as a semiconductor device including a semiconductor substrate 110. As the semiconductor substrate 110, for example, a silicon substrate can be used. The semiconductor substrate 110 is provided with a flow rate detecting section 120 and humidity detecting sections 130 and 140, which are main parts of the flow rate sensor 100. The humidity detectors 130 and 140 are provided near the flow rate detector 120. The flow rate detector 120 and the humidity detectors 130 and 140 are provided on the same surface of the semiconductor substrate 110.

In FIG. 3, the direction from the left side to the right side is the fluid flow direction α, and the direction from the right side to the left side is the fluid flow direction β. Two humidity detecting sections 130 and 140 are arranged so as to sandwich the flow rate detecting section 120 along the fluid flow directions α and β. The two humidity detectors 130 and 140 are arranged adjacent to the flow rate detector 120. In the fluid flow direction α, the first humidity detector 130 is located upstream of the flow rate detector 120, and the second humidity detector 140 is located downstream of the flow rate detector 120. Further, in the fluid flow direction β, the first humidity detecting unit 130 is located downstream of the flow rate detecting unit 120 and the second humidity detecting unit 140 is located upstream of the flow rate detecting unit 120.

As shown in FIG. 4, the flow rate detecting unit 120 includes a heat generating unit 121 and temperature sensing units 122 and 123. The heat generating part 121 is configured as a heat generating resistor, and the temperature sensing parts 122 and 123 are configured as temperature measuring resistors.

In FIG. 4, the direction from the left side to the right side is the fluid flow direction α, and the direction from the right side to the left side is the fluid flow direction β. Two temperature sensitive parts 122 and 123 are arranged so as to sandwich the heat generating part 121 along the fluid flow directions α and β. In the fluid flow direction α, the first temperature sensitive part 122 is located upstream of the heat generating part 121, and the second temperature sensitive part 123 is located downstream of the heat generating part 121. In the fluid flow direction β, the first temperature sensitive section 122 is located downstream of the heat generating section 121, and the second temperature sensitive section 123 is located upstream of the heat generating section 121.

The flow rate detection unit 120 detects the flow rate of the fluid by detecting the temperature rise value due to the heating of the fluid by the heat generation unit 121. That is, in the fluid flow directions α and β, the flow rate of the fluid is calculated by using the difference between the temperature detection values T ₁₂₂ and T ₁₂₃ of the fluid detected by the temperature sensing portions 122 and 123 located on the upstream side and the downstream side of the heat generating section 121. doing.

When the fluid flows in the fluid flow direction α, the detection value T ₁₂₂ of the first temperature-sensitive portion 122 on the upstream side becomes lower than the detection value T ₁₂₃ of the second temperature-sensitive portion 123 on the downstream side. Further, when the fluid flows in the fluid flow direction β, the detection value T ₁₂₃ of the second temperature-sensitive section 123 on the upstream side becomes smaller than the detection value T ₁₂₂ of the first temperature-sensitive section 122 on the downstream side. Therefore, by comparing the detection values T ₁₂₂ and T ₁₂₃ of the first temperature sensing unit 122 and the second temperature sensing unit 123, it is possible to determine which of the fluid flow directions α and β the fluid is flowing. .. Specifically, when the detection value T _{122 of} the first temperature sensing unit 122 <the detection value T ₁₂₃ of the second temperature sensing unit 123, the fluid is flowing in the fluid flow direction α, and When the detected value T ₁₂₂ >the detected value T ₁₂₃ of the second temperature sensing portion 123, the fluid is flowing in the fluid flow direction β.

Returning to FIG. 3, the humidity detectors 130 and 140 are configured as so-called capacitive humidity sensors. The humidity detection units 130 and 140 are provided with a detection electrode and a reference electrode (not shown), respectively. Then, a protective film such as a silicon nitride film (not shown) is formed on the semiconductor substrate 110 so as to cover the detection electrode and the reference electrode, and a moisture-sensitive material such as polyimide (not shown) is formed so as to cover the detection electrode on the protective film. The moisture-sensitive film is formed. The humidity detectors 130 and 140 can detect humidity from the capacitance difference between the capacitance between the detection electrodes and the capacitance between the reference electrodes.

A circuit portion 150 is provided on the semiconductor substrate 110. The circuit unit 150 is composed of elements such as MOS transistors and diodes and wiring, and is electrically connected to the flow rate detection unit 120 and the humidity detection units 130 and 140. A signal processing circuit that processes signals output from the flow rate detection unit 120 and the humidity detection units 130 and 140, a circuit that generates signals applied to the flow rate detection unit 120, the humidity detection units 130 and 140 at the time of detection, and the like. Contains.

A pad 160 as an electrode is formed at an end of the circuit section 150 formed on the semiconductor substrate 110, and the pad 160 is connected to a lead 170 as an external output terminal via a wire 180. Therefore, the circuit unit 140 and the outside (for example, the external ECU) can electrically exchange signals via the leads 170.

The semiconductor substrate 110 is fixed to the support member 190 by, for example, adhesion, with the back surface of the formation surface of the flow rate detection unit 120 and the humidity detection unit 130 as the mounting surface. In the present embodiment, the support member 190 is configured as a part of the lead frame together with the lead 170.

Then, a part of the semiconductor substrate 110 including the pad 160 and excluding the formation region of the flow rate detecting unit 120 and the humidity detecting unit 130, a part of the supporting member 190 corresponding to the part of the semiconductor substrate 110, the wire 180 and the lead 170. Is partially covered (molded) with a sealing resin 200 such as an epoxy resin.

Next, detection of the fluid flow rate by the flow rate detection unit 120 will be described. When the air passing through the intake passage 16 contains water, the specific heat value or the like changes depending on the amount of water, which causes an error in the flow rate detected by the flow rate detection unit 120. Therefore, the flow rate sensor 100 of the present embodiment is configured to correct the flow rate detected by the flow rate detection unit 120 based on the humidity detected by the humidity detection units 130 and 140.

The fluid passing through the flow rate detecting unit 120 is heated by the heat generating unit 121 included in the flow rate detecting unit 120, so that the temperature of the fluid rises. Therefore, the fluid passing through the flow rate detection unit 120 has a temperature distribution in which the temperature rises on the downstream side in the fluid flow directions α and β.

As shown in FIG. 5, the temperature distribution of the fluid passing through the flow rate detection unit 120 is different in the two fluid flow directions α and β. Therefore, the influence of the temperature distribution on the two humidity detection units 130 and 140 arranged with the flow rate detection unit 120 interposed therebetween differs depending on the fluid flow directions α and β.

In the fluid flow direction α, the second humidity detecting unit 140 located on the downstream side of the flow rate detecting unit 120 is affected by the temperature distribution, and the first humidity detecting unit 130 located on the upstream side of the flow rate detecting unit 120 is affected by the temperature distribution. Not affected. Further, in the fluid flow direction β, the first humidity detecting unit 130 located on the downstream side of the flow rate detecting unit 120 is affected by the temperature distribution, and the second humidity detecting unit 140 located on the upstream side of the flow rate detecting unit 120 has a temperature. Unaffected by distribution.

Next, detection of the flow rate by the flow rate sensor 100 of the present embodiment will be described with reference to FIG. The flowchart shown in FIG. 6 shows the processing performed by the circuit unit 140.

First, in the process of S10, the flow rate detector 120 detects the flow rate of the fluid passing through the intake passage 16. In the process of S10, the temperature of the fluid is detected by each of the first temperature sensing unit 122 and the temperature sensing unit 123 that configure the flow rate detection unit 120, and the flow rate of the fluid is acquired based on the difference between the detected values. ..

Next, in the process of S11, the humidity of the fluid is detected by the first humidity detector 130 and the second humidity detector 140.

Next, in the process of S12, it is determined whether the detection value of the first temperature sensing unit 122 exceeds the detection value of the second temperature sensing unit 123.

As a result of the determination processing of S12, when it is determined that the detection value of the first temperature sensing unit 122 does not exceed the detection value of the second temperature sensing unit 123, it is determined that the fluid is flowing in the fluid flow direction α. it can. Therefore, in the process of S13, the flow rate detected by the flow rate detection unit 120 is corrected using the detection value of the first humidity detection unit 130 located upstream of the flow rate detection unit 120 in the fluid flow direction α.

On the other hand, as a result of the determination processing in S12, when it is determined that the detection value of the first temperature sensing unit 122 exceeds the detection value of the second temperature sensing unit 123, the fluid is flowing in the fluid flow direction β. Can be judged. Therefore, in the process of S14, the flow rate detected by the flow rate detection unit 120 is corrected using the detection value of the second humidity detection unit 140 located upstream of the flow rate detection unit 120 in the fluid flow direction β.

According to the present embodiment described above, the two humidity detection units 130 and 140 are provided along the fluid flow directions α and β so as to sandwich the flow rate detection detection unit 120. As a result, even when the flow direction of the fluid changes, the humidity detecting units 130 and 140 located upstream of the flow rate detecting unit 120 in the fluid flow directions α and β of the two humidity detecting units 130 and 140 detect the flow rate. Humidity can be accurately detected without being affected by heat generated by the heat generating portion 121 of the portion 120. Therefore, by correcting the flow rate detected by the flow rate detection unit 120 using the detection values of the humidity detection units 130 and 140 located upstream of the flow rate detection unit 120 in the fluid flow direction α or the fluid flow direction β, the flow rate sensor It is possible to improve the accuracy of flow rate detection by 100.

In addition, in the present embodiment, the detection values of the two temperature sensing units 122 and 123 included in the flow rate detection unit 120 are used to determine whether the fluid is flowing in the fluid flow direction α or the fluid flow direction β. Deciding. Accordingly, it is possible to determine which of the two humidity detection units 130 and 140 is located upstream of the flow rate detection unit 120 in the fluid flow direction, and the humidity is not always affected by the heat generation unit 121 configuring the flow rate detection unit 120. The flow rate can be corrected using the detection values of the detection units 130 and 140.

(Second embodiment)
Next, a second embodiment of the present invention will be described based on FIG. The second embodiment is different from the first embodiment in the arrangement of the humidity detectors 130 and 140. Hereinafter, description of the same parts as those in the first embodiment will be omitted, and only different parts will be described.

It is considered that the flow rate of the fluid in the intake stroke of the internal combustion engine 10 is higher than the flow rate of the fluid in the pulsation. In this case, in the fluid flow direction α where the flow rate of the fluid is high and the fluid flow direction β where the flow rate of the fluid is low, the temperature distribution due to the heat generating section 121 of the flow rate detecting section 120 is not symmetric with respect to the flow rate detecting section 120.

As shown in FIG. 7, when the flow rate of the fluid in the intake stroke is sufficiently higher than the flow rate of the fluid in the pulsation, the temperature distribution shifted to the right side in the figure in the fluid flow direction α is the left side in the figure in the fluid flow direction β. Even if it is shifted to, it is assumed that the center of the temperature distribution is on the right side of the center of the flow rate detection unit 120.

The first humidity adjusting unit 130, which is located on the upstream side of the flow rate detection unit 120 in the flow rate flow direction α and on the downstream side of the flow rate detection unit 120 in the flow rate flow direction β, generates heat generated by the heat generation unit 121 of the flow rate detection unit 120. Not easily affected. On the other hand, the second humidity adjusting unit 140 located downstream of the flow rate detecting unit 120 in the flow rate flow direction α and upstream of the flow rate detecting unit 120 in the flow rate flow direction β is the heat generating unit of the flow rate detecting unit 120. It becomes easy to be affected by heat from 121.

Therefore, in the second embodiment, the distance L1 between the first humidity detecting unit 130 and the flow rate detecting unit 120 and the second humidity according to the temperature distribution assumed in the two flow rate flow directions α and β having different flow rates. The distance L2 between the detection unit 140 and the flow rate detection unit 120 is different. Specifically, the distance L2 between the second humidity detector 140 and the flow rate detector 120 is set longer than the distance L1 between the first humidity detector 130 and the flow rate detector 120.

That is, the distance L2 between the flow rate detector 120 and the second humidity detector 140 located on the downstream side in the fluid flow direction α where the flow rate is high is equal to the distance L2 in the fluid flow direction β where the flow rate is low. It is made longer than the distance L1 from the first humidity detector 130 located on the side. As a result, it is possible to avoid the influence of heat from the heat generating unit 121 of the flow rate detection unit 120 in each of the two humidity adjustment units 130 and 140 arranged with the flow rate detection unit 120 interposed therebetween.

According to the second embodiment described above, the distances L1 and L2 between the humidity detection units 130 and 140 and the flow rate detection unit 120 are set according to the temperature distributions assumed in the fluid flow directions α and β with different fluid flow rates. It is set. As a result, it is possible to prevent the two humidity detection units 130 and 140 arranged so as to sandwich the flow rate detection unit 120 from being affected by the heat of the heat generation unit 121 of the flow rate detection unit 120, and to detect humidity with high accuracy. You can enable it. As a result, the flow rate detection accuracy of the flow rate sensor 100 can be ensured.

(Other embodiments)
The present invention is not limited to the above-described embodiments, but can be variously modified as follows without departing from the spirit of the present invention. Further, the means disclosed in each of the above-described embodiments may be appropriately combined within a practicable range.

For example, in each of the above-described embodiments, the fluid flow directions α and β are detected based on the detection values of the two temperature sensing units 122 and 123 included in the fluid detection unit 120, but the present invention is not limited to this and is different. The fluid flow directions α and β may be detected by means. For example, when there is a correlation between the opening/closing timings of the valves 13 and 14 of the internal combustion engine 10 and the fluid flow directions α and β, the fluid flow directions α and β are determined based on the opening and closing timings of the valves 13 and 14. You may.

Further, in each of the above embodiments, the circuit unit 140 provided in the flow rate sensor 100 is configured to correct the flow rate detected by the flow rate detection unit 120 based on the humidity detected by the humidity detection units 130 and 140. The present invention is not limited to this, and the flow rate detected by the flow rate detection unit 120 may be corrected outside the flow rate sensor 100 (for example, a control device such as an ECU).

100 flow rate sensor 110 semiconductor substrate 120 flow rate detection unit 121 heat generation unit 122 first temperature sensing unit 123 second temperature sensing unit 130 first humidity sensing unit 140 second humidity sensing unit

Claims (4)

A flow rate detecting section (120) having at least a heat generating section (121) for detecting the flow rate of the fluid;
Two humidity detectors (130, 140) that are provided so as to sandwich the flow rate detector along the flow direction of the fluid and that detect the humidity of the fluid;
A flow sensor having a. The detection value of the humidity detection unit located upstream of the flow rate detection unit in the flow direction of the fluid of the two humidity detection units is used for correction of the detection value of the flow rate detection unit. Flow sensor. The flow rate detection unit is provided so as to sandwich the heat generating unit along the flow direction of the fluid, has two temperature sensing units (122, 123) that detect the temperature of the fluid, and has the two temperature sensing units. The flow rate sensor according to claim 1, wherein the flow direction of the fluid can be detected based on the detection value of the part. 4. The distance between each of the two humidity detection units and the flow rate detection unit is set according to the flow rate of each of the fluids when the flow direction of the fluid is different. The flow sensor according to any one of the above.

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