JPH0862009A - Intake air amount sensor for internal combustion engine - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the heat capacity by downsizing the thermal resistor and suppress the heat loss due to heat conduction from the thermal resistor to the support to improve the responsiveness at power-on. [Structure] The flow rate detecting element 5 is composed of a thermal resistor 6 and a support 7 that supports the thermal resistor 6 from a passage forming member 4. The support body 7 is composed of an elongated rod body or a thin strip that extends across the throat portion 2b in a direction orthogonal to the intake air flow, and the support body 7 has an opening 8 for arranging a thermal resistor penetrating in the intake air flow direction. To form. The thermal resistor 6 is formed in the shape of an elongated rod or strip and is installed in the opening 8 of the support 7 in the air.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake air amount sensor for an internal combustion engine using a thermal type flow meter.

[0002]

2. Description of the Related Art As an intake air amount sensor for an internal combustion engine,
For example, one using a principle of a hot film type thermal flow meter is known, which is disclosed in, for example, Japanese Patent Laid-Open No. 1-288.
No. 725 publication. This intake air amount sensor has a flow rate detecting element by a thermal resistor arranged in the intake passage across the passage, and the flow detecting element is driven by a blick circuit to keep the temperature of the flow detecting element constant. , The intake air flow rate is quantitatively detected by the voltage across the terminals of the rich circuit.

The applicant of the present invention has previously filed Japanese Patent Application No. 5-2229.
In the specification and drawings of No. 5, the throttle passage portion whose intake passage cross-sectional area gradually decreases toward the downstream side of the intake flow, and the throttle passage portion located downstream of the throttle passage portion and further toward the downstream side. An enlarged passage portion in which the air passage cross-sectional area gradually expands, and a throat portion having a constant intake passage cross-sectional area are formed between the throttle passage portion and the enlarged passage portions, connecting the throttle passage portion and the enlarged passage portion. It proposes an intake air amount sensor having a housing and a multiple ring-shaped hot-wire type flow rate detection element arranged in the throat portion.

[0004]

One of the several performance items required for an intake air amount sensor for an internal combustion engine, particularly an automobile engine is responsiveness at the time of starting the engine. In order to prevent deterioration of exhaust gas performance at engine start, it is necessary for the intake flow rate sensor to respond promptly at engine start and to appropriately control the gasoline injection amount based on the signal from the intake air amount sensor. It

In the intake air amount sensor of the prior art, a multi-ring type flow rate detecting element is arranged over the entire throat of the intake passage, and the average flow rate of the intake air flowing through the intake passage can be accurately measured. However, in this case, the flow rate detecting element has a predetermined surface area, in other words, a predetermined volume (mass).
And has a large heat capacity. Therefore, in the conventional intake air amount sensor, it takes time until the flow rate detecting element is heated when the engine is started, that is, when the power is turned on,
There is room for improvement in responsiveness.

An object of the present invention is to provide an intake air amount sensor for an internal combustion engine, which has improved responsiveness at the time of starting the engine.

[0007]

The present invention will be described with reference to FIGS. 1 to 3 showing an embodiment. In the present invention, the throttle passage portion in which the cross-sectional area of the intake passage gradually decreases toward the downstream side of the intake flow. 2a, an enlarged passage portion 2c located downstream of the throttle passage portion 2a, and the supply passage cross-sectional area gradually increasing toward the downstream side, between the throttle passage portion 2a and the enlarged passage portion 2c. Housing 4 in which the throttle passage portion 2a and the enlarged passage portion 2c are connected to each other and a throat portion 2b having a constant intake passage cross-sectional area is formed, and a flow rate detecting element disposed in the throat portion 2b at right angles to the intake flow direction. And an intake air amount sensor for an internal combustion engine having The flow rate detecting element 5 is formed of an elongated rod body or a strip-shaped thin plate extending across the throat portion 2b in a direction orthogonal to the intake air flow, and is supported by the housing 4 with an opening 8 penetrating in the intake air flow direction. The above-mentioned object is achieved by the support 7 and the thermal resistor 6 which is formed in the shape of an elongated rod or strip and is installed in the opening 8 of the support 7 in the air. An intake air amount sensor for an internal combustion engine according to a second aspect of the invention is characterized in that the thermal resistor 6 is arranged on a surface portion of the support 7 on the downstream side of the intake flow. In the intake air amount sensor of the internal combustion engine according to claim 3, the rectifier 13 that rectifies the intake air so that the intake flow passing through the flow rate detecting element 5 has an average flow velocity distribution in the intake passage is provided on the upstream side of the flow rate detecting element 5. It is characterized in that it is arranged in the throat section 2b. In the intake air amount sensor of the internal combustion engine according to claim 4, the thickness of the rectifier 13 in the intake flow direction is 15 to 25 mm, and the rectifier 13 is located at a distance of 5 to 10 mm from the upstream end of the throat portion 2b to the downstream side. 15 to 30 from the downstream end of the rectifier 13
The flow rate detection element 5 is arranged at a distance of mm and within a distance of 0 to 5 mm from the downstream end of the throat portion 2b to the upstream side.

[0008]

[Function] The heat resistor 6 has an elongated rod shape or a strip shape,
Its heat capacity is reduced. The thermal resistor 6 is erected in the air in the opening 8 of the support 7 to reduce heat transfer from the thermal resistor 6 to the support 7. In the intake air amount sensor of the second aspect, the heat flow from the heat resistor 6 that generates heat flows to the downstream side of the intake passage, and the heat conduction from the heat resistor 6 to the support 7 is reduced. Claim 3
In the intake air amount sensor, the rectifier 13 rectifies the intake airflow flowing through the throat portion 2b, and an average flow velocity distribution in the intake passage is provided in the vicinity of the thermal resistor 6. In the intake air amount sensor according to the fourth aspect, the proper arrangement position and shape of the rectifier 13 are selected.

Incidentally, in the section of means and action for solving the above-mentioned problems for explaining the constitution of the present invention, the drawings of the embodiments are used to make the present invention easy to understand. It is not limited to.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the overall construction of an embodiment of an intake air amount sensor according to the present invention. The intake air amount sensor 1 is
It has a cylindrical housing 4 connected in the middle of an intake duct 3 that constitutes an intake air passage 2 of an internal combustion engine.
The intake passage 2 in the housing 4 is connected to a throttle passage 2a whose passage cross-sectional area gradually decreases in the direction of the intake flow indicated by the white arrow in FIG. It is composed of a constant throat portion 2b and an enlarged passage portion 2c which is connected to the downstream side of the throat portion 2b and whose passage cross-sectional area gradually increases toward the downstream side. In other words, the throat portion 2b is between the throttle passage portion 2a and the enlarged passage portion 2c and connects the throttle passage portion 2a and the enlarged passage portion 2c. In this embodiment, the throttle passage portion 2a and the enlarged passage portion 2c are each formed in a conical shape, and the throat portion 2b is formed in a cylindrical shape.

A flow rate detecting element 5 is arranged in the throat portion 2b at right angles to the intake air flow direction. As shown in FIG. 2, the flow rate detection element 5 has a thermal resistor 6 and a support 7 that supports the thermal resistor 6 with the housing 4. The support 7 is an elongated rod-shaped or strip-shaped thin plate, for example, having a width of 5
It is composed of a strip-shaped thin plate of about mm and extends vertically across the throat portion 2b in the direction orthogonal to the intake air flow. The upper and lower ends thereof are connected to the housing 4 and the thermal resistor is arranged substantially in the center. The rectangular opening 8 of the above penetrates in the intake air flow direction. The support 7 is composed of an electrically insulating resin plate such as a glass epoxy resin plate used as a general electric circuit board, and has a copper foil electrode layer 9 for energizing the thermal resistor 6 on the surface thereof. , 10 are formed in a predetermined pattern.

FIG. 3 is an enlarged view of a portion where the thermal resistor is arranged.
The thermal resistor 6 is formed by laminating a platinum thick film resistance layer and a protective layer made of an insulating material such as SiO ₂ or Si—Nx on a ceramic substrate such as alumina, and has an elongated rod shape or a strip shape, for example, a long shape. Is about 5 mm and the width is 0.3
It is formed in a band shape having a thickness of about 0.1 mm and a thickness of about 0.15 mm, and is arranged so as to vertically cross the central portion of the opening 8 in the lateral width direction. The upper and lower ends of the thermal resistor 6 are placed on the electrode layers 9 and 10, respectively, and a conductor wire 11 made of a platinum wire, a platinum-palladium wire, a copper wire, etc., having a diameter of about 0.1 mm, is provided across each of the both ends. By fixing 12 to the electrode layers 9 and 10 by soldering, the electrodes 12 are electrically connected to the electrode layers 9 and 10, and at the same time, are supported by the support body 7 and installed in the opening 8 in the air.

As shown in FIG. 1, the throat portion 2
In b, the honeycomb rectifier 13 is provided upstream of the flow rate detecting element 5.
Are fixedly arranged. The honeycomb rectifier 13 has a cell size of about ⅛ inch and has a size of 15 to 25 in the intake flow direction.
It has a thickness (dimension b) of mm, the upstream end face is located at a distance (dimension a) of about 5 to 10 mm from the upstream end of the throat portion 2b to the downstream side, and the downstream end face and the flow rate detecting element 5 are provided. Distance of about 15 to 30 mm between the and (c dimension)
Is arranged to have. In this case, the flow rate detection element 5 moves from the downstream end of the throat portion 2b to the upstream side.
Placed within a distance (dimension d) of ~ 5 mm.

The operation of the intake air amount sensor thus configured will be described. First, the relationship between the response of the flow rate detecting element when the power is turned on and the element shape will be described.
FIG. 4 schematically shows the change over time in the output value of the intake air amount sensor when the power is turned on. As can be seen from FIG. 4, during the period when the output voltage stabilizes when the power is turned on, the thermal resistor 6 to which current is supplied heats up and the output value sharply increases, and the idling of the internal combustion engine. There is a steady-state portion B in which the output value gradually decreases due to the cooling action due to the intake air flowing at a constant intake flow rate corresponding to
A + B is the response time of the intake air amount sensor.

The initial steep portion A is the rise time of the output value when the power is turned on, which depends on the heat capacity of the thermal resistor 6. Therefore, the initial steep portion A is shortened by reducing the volume (mass) of the thermal resistor 6. In the steady-state portion B, the amount of heat generated by the heat resistor 6 is radiated into the intake air flow, and after a predetermined time, the amount of heat generated by the heat resistor 6 and the amount of heat radiated are balanced until the output value becomes a constant value. Is. This is a thermal resistor 6
Depends on the amount of heat radiated into the intake air flow and the amount of heat due to heat transfer from the thermal resistor 6 to the support 7. Therefore, the stationary portion B is shortened by reducing the amount of heat due to the heat transfer from the thermal resistor 6 to the support 7.

FIG. 5 is experimental data showing the relationship between the heat capacity of the flow rate detecting element and the response when the power is turned on. The detector used in the experiment is as follows. A: 10φ, 28φ double ring, 0.35t, 0.6
w, 4 beams B: 19φ single ring, 0.35t, 0.6w, 4 beams C: 10φ single ring, 0.35t, 0.6w, 4 beams D: 19φ single ring, 0. 35t, 0.6w, 2 beams E: 10φ single ring, 0.35t, 0.6w, 2 beams F: 15φ single ring, 0.3t, 0.4w, no beam G: 13φ single ring , 0.2t, 0.35w, without beam As can be seen from the experimental data in FIG. 5, there is a substantially proportional relationship between the heat capacity of the thermal resistor and the response when the power is turned on.

If the thermal resistor is a conventional one in which three concentric annular parts are connected by a linear connecting part, the inner diameter of the throat part is 56 mm, and the triple part is formed. Inner diameters of concentric circular rings are 10 mm and 2 respectively
If the width of the annular portion is 8 mm, 46 mm, and the annular portion is 1 mm, the total area is 273.5 mm ² . In contrast, the thermal resistor 6 in the intake air amount sensor according to this embodiment has an area of 1.5 m when the length is 5 mm and the lateral width is 0.3 mm, for example.
It becomes m ² . When this is converted into heat capacity, the heat capacity of the heat resistor of the prior art is 0.107 Cal / ° C., and the heat capacity of the heat resistor 6 of the present embodiment is 0.376 × 10.
^-3 Cal / ° C. As described above, the thermal capacity of the thermal resistor 6 of this embodiment is 3.5 × 10 ^{−3 as} compared with that of the prior art.
The ratio is significantly smaller.

As described above, in the intake air amount sensor according to the present invention, the shape of the thermal resistor 6 is reduced to reduce its heat capacity, and the thermal resistor 6 is placed in the opening 8 of the support 7 in the air. The heat loss that is transferred from the thermal resistor 6 to the support 7 is reduced by installing it, and the response when the power is turned on is sufficiently improved.

Next, the operation of the rectifier will be described. In the conventional technology, since the thermal resistor is arranged over the entire cross section of the flow path, even if the flow velocity distribution is asymmetric and unstable, the flow rate close to the average flow rate is measured by the shape effect of the thermal resistor itself. be able to. Thermal resistor 6 according to the present invention
Is extremely smaller than the conventional triple concentric ring shape, it is difficult to detect the average flow rate of the entire flow path. When an unsteady flow is to be measured symmetrically like an intake air amount sensor of an internal combustion engine, or when the space for arranging the intake air amount sensor is restricted, the pressure is reduced in a relatively short flow path length. It is necessary to stabilize the flow at the flow measurement site without significantly increasing the loss. Therefore, the honeycomb rectifier 13 is provided.

Next, the effect of the honeycomb rectifier 13 arranged on the upstream side of the thermal resistor 6, the proper arrangement position and the proper thickness will be described based on the experimental results. The flow path used in the experiment has an inner diameter of the inlet portion of the suction passage 2 of 70 mm and an inner diameter of the throat portion 2b of 56 mm. The flow rate is 4
It was set to 0 kg / h to 20 kg / h. FIG. 6 shows the experimental results, where a to d correspond to a to d in FIG. 1, and the error is a percentage display of the difference from the intake air amount measured by another reliable flow meter.

From the experimental results of Case 1 to Case 3, it is understood that the thickness b of the honeycomb rectifier 13 is 20 mm, which is the best, and the rectification effect is increased from 15 mm. The thickness b of the honeycomb rectifier 13 is 25 m.
If it is more than m, the increase of the pressure loss becomes larger than the increase of the rectifying effect, which is not suitable for an internal combustion engine. Therefore, the thickness b of the honeycomb rectifier 13 is preferably set to 15 to 25 mm, and most preferably 20 mm.

When the flow passage diameter of the throat portion 2b increases from 1.5 times to about 2 times, the thickness b of the honeycomb rectifier 13 needs to be increased to 25 mm. When the flow path diameter of the throat portion 2b is 0.7 times or less, the thickness b of the honeycomb rectifier 13 can be reduced to 15 mm.

The following can be understood from the experimental results of Case 3 to Case 5. This is a consideration regarding the distance c, and the rectification effect does not sufficiently appear at a distance of 10 mm downstream from the honeycomb rectifier 13. A rectifying effect is obtained at 15 mm or more on the downstream side of the honeycomb rectifier 13, and about 20 mm is the best. In addition, 3 from the honeycomb rectifier 13 to the downstream side
It has been confirmed by experiments that the rectifying effect decreases when the distance is 0 mm or more. Therefore, the distance c is preferably set to 15 to 30 mm, and most preferably about 20 mm.

The following can be understood from the experimental results of Case 6 to Case 8. The honeycomb rectifier 13 has a throat portion 2b
The rectifying effect is large by arranging it at a slight distance a of about 5 mm from the upstream end of the. Also, 20
The increase in pressure loss due to the arrangement of the honeycomb rectifiers 13 having a thickness of mm is smaller when the honeycomb rectifiers 13 are arranged at a slight distance a. It should be noted that, in this experiment, even if the distance is 10 mm or more, the rectifying effect and the increase in the pressure loss are not reduced.

Finally, the experimental results of case 8 to case 10 will be described. The length of the throat portion 2b was changed to change the length of the flow rate detecting element 5 on the downstream side. Thermal resistor 6
In the case of arranging immediately before the flow path expanding portion 2c, the error amount between the value measured by the thermal resistor 6 and the average flow rate value obtained from the lamina / ulometer was smaller.

In the above experiment, as shown in FIG. 1, the support body 7 of the thermal resistor 6 has a shape extending across the entire throat portion 2b in a direction orthogonal to the intake flow of the throat portion 2b. did. When the length of the support 7 was halved and the thermal resistor 6 was suspended from above the housing, the error in the flow rate detection value became about 2 to 3 times larger. Therefore, it is important to arrange the thermal resistor 6 on the support 7 so as to have a symmetrical shape with respect to the flow path. This is support 7
This is because the flow velocity distribution in the cross section in which the support body 7, that is, the thermal resistor 6 is arranged changes depending on the shape of, and does not become an average distribution in the intake passage.

FIG. 7 shows a second embodiment of the intake air amount sensor according to the present invention. In this embodiment, the electrode layer 9,
The ten patterns are different from those of the first embodiment shown in FIG. Other than that, the configuration is similar to that of the first embodiment, and the description is omitted.

FIG. 8 shows a third embodiment of the intake air amount sensor according to the present invention. In this embodiment, the electrode layers 9 and 10 are formed on the surface of the support 7 on the downstream side, and the thermal resistor 6 is arranged on the surface of the downstream side.
In this embodiment, the heat flow from the heat generating resistor 6 flows to the downstream side of the intake passage 2, and the amount of heat transferred from the heat resistor 6 to the support 7 is further reduced. As a result, the time for the above-mentioned steady-state portion B is effectively shortened, and the responsiveness when the power is turned on is further improved.

FIG. 9 shows a fourth embodiment of the intake air amount sensor according to the present invention. In this embodiment, the thermal resistor 6
Is placed in the opening 8, and the upper and lower ends are connected to the conductor 11,
It is supported by the support 7 by 12 and is completely installed in the air in the opening 8 without directly contacting the support 7.
The electrode layer 10 is electrically connected to a back side electrode layer (not shown) through a through hole 14 which is plated with a through hole.

In this embodiment, since the thermal resistor 6 is not directly fixed to the support 7 but is completely installed in the opening 8 in the air, the heat transfer from the thermal resistor 6 to the support 7 is further enhanced. In this case as well, the time for the above-mentioned steady-state portion B is effectively shortened, and the response when the power is turned on is further improved.

FIG. 10 shows a fifth embodiment of the intake air amount sensor according to the present invention. In this embodiment, the width of the opening 8 is increased as compared with the embodiment shown in FIG.
The beam width on both sides of the opening 8 is, for example, 1.1 mm to 0.5 m
It has been reduced to m. Also in this case, the amount of heat transferred from the thermal resistor 6 to the support 7 is further reduced, and the response when the power is turned on is further improved.

From the above, the embodiment obtained by combining the third embodiment and the fifth embodiment is the intake air amount sensor having the best thermal response.

FIG. 11 shows a sixth embodiment of the intake air amount sensor according to the present invention. In this embodiment, the opening 8
Has a notch shape. Also in this embodiment, the same operation as the above-mentioned embodiment can be obtained.

[0034]

As described above, according to the intake air amount sensor of the internal combustion engine according to the present invention, the volume of the thermal resistor is reduced and the thermal resistor is installed in the opening of the support body in the air. Since it has a structure that does not easily transfer heat to the support,
The responsiveness of the sensor at engine start is improved. Further, by disposing the thermal resistor on the surface of the support on the downstream side of the intake flow, heat conduction from the thermal resistor to the support is further reduced, and the responsiveness of the sensor at engine start is further improved. . The flow velocity distribution of the intake air flowing through the throat is averaged by the rectifier on the upstream side of the thermal resistor, and the intake air amount is correctly measured regardless of the miniaturization of the thermal resistor. By arranging the rectifier at the proper position and selecting the shape, it is possible to suppress the increase in pressure loss due to the installation of the rectifier and to effectively obtain the rectification effect. The error can be reduced.

[Brief description of drawings]

FIG. 1 is a side sectional view showing the overall configuration of an embodiment of an intake air amount sensor according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a portion where a flow rate detection element of the intake air amount sensor shown in FIG. 1 is arranged.

3 (a) is an enlarged front view of a portion where a thermal resistor is arranged in the intake air amount sensor shown in FIG. 2, and FIG. 3 (b) is a sectional view thereof.

FIG. 4 is a graph schematically showing the change over time in the output value of the intake air amount sensor when the power is turned on.

FIG. 5 is a graph showing the relationship between the heat capacity of the flow rate detection element and the response when the power is turned on.

FIG. 6 is a diagram for explaining experimental results.

FIG. 7 is an enlarged front view showing a second embodiment of the intake air amount sensor according to the present invention, in which a thermal resistor is arranged.

FIG. 8 is an enlarged side sectional view showing a third embodiment of the intake air amount sensor according to the present invention, in which a thermal resistor is arranged.

FIG. 9 is an enlarged front view showing a fourth embodiment of the intake air amount sensor according to the present invention, in which a thermal resistor is arranged.

FIG. 10 is an enlarged front view showing a fifth embodiment of the intake air amount sensor according to the present invention, showing a thermal resistor arrangement portion.

FIG. 11 is an enlarged front view showing a sixth embodiment of the intake air amount sensor according to the present invention, in which a thermal resistor is arranged.

[Explanation of symbols]

 1 intake air amount sensor 2 intake air passage 2a throttle passage 2b throat portion 2c enlarged passage portion 3 intake duct 4 housing 5 flow rate detection element 6 thermal resistor 7 support 13 honeycomb rectifier

Claims (4)

[Claims] 1. A throttle passage portion whose intake passage cross-sectional area gradually decreases toward the downstream side of the intake flow, and a supply passage cross-sectional area located downstream of the throttle passage portion and toward the downstream side. Is formed between the throttle passage portion and the enlarged passage portion, and the throat portion having a constant intake passage cross-sectional area is formed between the throttle passage portion and the enlarged passage portion. An intake air amount sensor for an internal combustion engine, comprising: a housing; and a flow rate detecting element that is disposed in the throat portion at right angles to an intake air flow direction and detects an intake air amount passing through the housing, wherein the flow rate detecting element comprises: (A) The housing is formed of an elongated rod body or a strip-shaped thin plate extending across the throat portion in a direction orthogonal to the intake air flow, and has an opening penetrating in the intake air flow direction. A support body supported, (b)
An intake air amount sensor for an internal combustion engine, comprising: a heat resistor formed in an elongated rod shape or a belt shape and installed in the air in the opening of the support. 2. The thermal resistor is arranged on a surface of the support on the downstream side of the intake passage.
An intake air amount sensor for an internal combustion engine according to item 1. 3. A rectifier for rectifying the intake air is arranged in the throat portion upstream of the flow rate detecting element so that the intake air flow passing through the flow rate detecting element has an average flow velocity distribution in the intake passage. An intake air amount sensor for an internal combustion engine according to claim 1 or 2. 4. The thickness of the rectifier in the intake flow direction is 15
˜25 mm, this rectifier is arranged at a distance of 5 to 10 mm from the upstream end of the throat portion to the downstream side, and at a distance of 15 to 30 mm from the downstream end of the rectifier and at the throat portion. 0 to 5m from the end on the downstream side to the upstream side
The intake air amount sensor for an internal combustion engine according to claim 3, wherein the flow rate detecting element is arranged within a distance of m.