JPH02249920A - Inhaled air quantity detector - Google Patents

Abstract

PURPOSE:To secure the stable detection accuracy by fixing a base end part of a beam material of a detecting element, and inserting and holding the tip part by an elastic member. CONSTITUTION:As for a detecting element 10, its base end part is fixed to a holder 1, and its tip part is inserted and held between elastic members 4a, 4b. Accordingly, even if vibration of an internal combustion engine is transferred to the holder 1 through an inhaling cylinder, there is no possibility that the element 10 is resonated. Also, even if a relative movement is generated between the holder 1 and the element 10 due to a difference of thermal expansion coefficients between both of them, since the tip part of the element 10 is supported by the holder 1 with a prescribed gap, it is absorbed by this part, and no detection error is caused by a thermal expansion.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an intake air amount detection device that detects the flow rate of intake air flowing through an intake passage, particularly an intake passage of an internal combustion engine.

[Prior Art] Regarding a flow rate detection device for detecting the intake air amount of an internal combustion engine, there is a flow rate detection device in which an intake air temperature detection element and a flow velocity detection element are arranged in an intake air passage parallel to the flow direction of the intake air. is known, for example, JP-A-60-230019
It is disclosed in the publication No.

In the above-mentioned flow rate detection device, each detection element has a heat-sensitive resistor, and these heat-sensitive resistors and a fixed resistor constitute a bridge circuit. A heating resistor is arranged in parallel with the flow velocity detection element, and the heating resistor controls the temperature of the heat sensitive resistor of the flow velocity detection element to be higher than that of the intake air temperature detection element by a predetermined temperature. That is, the predetermined temperature difference is maintained by controlling the current supplied to the heating resistor according to the temperature of the heat-sensitive resistor of the flow rate detection element, which changes according to the amount of heat absorbed by the intake air. The flow velocity is detected from the plane potential difference, and the flow rate is detected from this flow velocity.

Then, the technology of forming all the resistors including the heating resistor with thin film resistors and configuring them into one element was developed in 1983-183.
It is described in Publication No. 825.

In this publication, a groove or slit is provided in the base material between the heat generating resistor, that is, the heating resistor, which heats the flow velocity detection element and the heat sensitive resistor which detects the temperature of the gas to be measured.
It is intended to prevent measurement errors due to heat transfer from the heating resistor.

The flow rate detection device described in the above publication is an indirect heating type in which the flow rate detection element is heated by a heating resistor. There is also a self-heating type that generates heat. In the flow rate detection element described in this publication, a thin film resistor is formed on one base material, and the base material is fixed to the intake cylinder with cantilever support.

Incidentally, the amount of heat generated by the flow rate detection element in the flow rate detection device is transmitted to the surrounding air and the attachment portion to the intake air passage. Regarding this, when the flow velocity of the intake air is high, most of the calorific value is immediately transferred to the surrounding air, but when the flow velocity of the intake air is small, the amount of heat transferred to the surrounding air is small. The amount of heat conducted to the attachment portion is relatively increased. Since the amount of heat conduction to the mounting portion changes depending on the intake air temperature and the temperature of the intake passage, the current supplied to the bridge circuit described above changes, thereby reducing the accuracy of detecting the flow velocity.

To address this problem, Japanese Patent Laid-Open No. 59-151020 discloses a technique in which the ratio of the length and diameter of the lead wire of the heat-sensitive resistor is set to a predetermined value or more in order to reduce the amount of heat conducted to the mounting part. has been done.

Further, Japanese Patent Application Laid-open No. 60-230020 also discloses a structure in which a detection element in which a resistance element is attached in a thin film form on a base material is electrically and mechanically supported by a band-shaped lead member. A technique has also been disclosed in which a detection element is supported at both ends by a holder using this lead member, and the holder is attached to an intake cylinder of an internal combustion engine.

[Problems to be Solved by the Invention] However, with regard to the technique described in JP-A-59-151020, increasing the diameter ratio has its own limitations in terms of strength. Also, JP-A-60-2300
The support structure of the detection element in the intake air amount detection device described in Publication No. 20 is supported at both ends by band-shaped lead members,
Although it is firmly supported, since the flow rate detection resistor needs to be heated, whether it is a self-heating type or an indirect heating type, there is a risk that the base material and the band-shaped lead member may be deformed due to thermal expansion.

In the above-mentioned Japanese Unexamined Patent Publication No. 57-201858, the base material having the thin film resistor at its tip is cantilevered by the mounting portion, so deformation due to thermal expansion is avoided. In addition, if the base material is thin and made of a material with low thermal conductivity, even when the part where the thin film resistor is provided is set to a predetermined temperature higher than the intake air temperature, the amount of heat generated will be smaller at the base of the base material. conduction to the parts and their mounting parts.

However, in such a detection element, there is a limit even if the thickness of the base material can be made thinner, since there is a risk of causing not only strength problems but also problems such as generation of vibration of the base material. In particular, since such vibrations of the base material cause errors in the detection output of the flow velocity detection resistor, at least the base material on which the flow velocity detection resistor is provided must be made thick.

That is, if the thickness of the base material is made thinner with a cantilever support structure, a problem arises in that the detection element undergoes resonance due to the vibration of the mounting portion or self-supporting vibration due to the intake air flow.

Therefore, the present invention provides an intake air amount detection device that includes a detection element made of a base material to which a flow rate detection resistor is attached, and that allows the detection element to be mounted on a mounting portion with a stable support structure without increasing the thickness of the base material. The purpose is to provide

[Means for Solving the Problem] In order to achieve the above object, the present invention includes a flat base material,
A detection element comprising a flow rate detection resistor, which is a thin film resistor attached to the plate surface of the base material and whose resistance value changes at least in accordance with temperature changes caused by the flow rate of the intake air to be measured, is attached to the intake air. An intake air amount detection device disposed in an intake cylinder so that the plate surface of the base material is parallel to the air flow direction, the apparatus having an opening in at least the intake air flow direction and installed in the intake cylinder. A holder is provided, the detection element is housed in the opening of the holder, the proximal end of the base is fixed, the distal end of the base is clamped via an elastic member, and the distal end of the base is The holder is supported by the holder to allow axial movement of the holder.

[Function] In the intake air amount detection device configured as described above, the base end of the base material of the detection element is fixed to the holder, and the detection element is housed in the opening of the holder.

The tip of the base material of this detection element is held by a holder via an elastic member and is supported so as to be movable in the axial direction. Thereby, even if the thickness of the base material is set to be thin, the occurrence of vibration of the detection element can be suppressed. Then, the holder is attached to the intake pipe so that the surface of the base plate of the detection element is parallel to the flow of intake air, and a bridge circuit is configured, for example, by including a flow velocity detection resistor attached to the base of the detection element. Ru.

Therefore, the balance condition of the bridge circuit is established in a state where the flow rate detection resistor is normally heated to a predetermined temperature higher than the intake air temperature, and as intake air is introduced, the flow rate detection resistor is heated to a predetermined temperature higher than the intake air temperature. When the body's heat is taken away by the inhaled air and the temperature decreases, its resistance value decreases. As a result, the bridge circuit becomes unbalanced, and the output potential difference is detected to measure the amount of intake air, and in accordance with this output, the flow rate detection resistor is controlled to self-heat so as to maintain the balanced condition of the bridge circuit. At this time, since the thickness of the base material can be set thin as described above, the amount of heat transferred from the flow velocity detection resistor to the holder by thermal conduction is small, and therefore the error in the detected intake air amount can be kept small. can.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show a holder 1 and a detection element 10 supported by the holder 1 used in an embodiment of the intake air amount detection device of the present invention. II-
3 shows a cross section taken along line III--III in FIG. 1.

As is clear from FIGS. 1 and 2, the holder 1 is a stepped cylindrical body made of synthetic resin.
The lid body 3 is divided into two parts, and a through-hole opening 1a including this dividing surface is formed. Therefore, the main body 2 has a shape in which a part of the stepped cylindrical body is cut out into a semi-cylindrical shape and a recess is formed in the radial direction from the cut surface, and the lid body 3 is a semi-cylindrical body and has a shape in which a recess is formed in the radial direction from the cut surface. It has a shape with a recess formed in the radial direction.

An engaging protrusion 2a is provided protruding from the radial end of the flat portion of the main body 2, and engaging protrusions 2b and 2c are provided protruding from both axial end portions, as shown in FIG. 2(a). has been done. Note that these engaging protrusions 2a and 2b.

A hook portion extending inward is formed in 2C.

An engaging protrusion 3a and engaging protrusions 3b and 3C are provided protrudingly from the radial end and both axial ends of the flat surface of the lid 3, respectively. These engaging protrusions 3a, 3b, and 3c are formed with hook portions that extend outward. When the lid 3 is fitted into the cutout of the main body 2 and pressed in the axial direction, the engaging protrusions 2a, 2b, 2c engage with the engaging protrusions 3a, 3b, 3c, respectively, and snap into place. As a result of the action, the respective hooks are overcome, and a stepped cylindrical body having an opening 1a is formed as shown in FIG. 341 and FIG. 2(b). In this way, the main body 2 and the lid 3 can be firmly fixed by the engaging protrusions 2a, 2b, 2c and the engaging protrusions 3a, 3b, 3c.

As shown in FIG. 2(a), a rectangular recess 2d that communicates with the opening 1a is formed along the axial direction on the base end side plane part of the main body 2, and the base end of the detection element 10 is connected to this rectangular recess 2d. is fitted. A recess 3d that includes the recess 2d is formed at a position facing the recess 2d in the axial direction of the flat surface of the lid 3, and the recess 3d includes the recess 2d.
The structure is such that a gap is formed between the body 2 and the body 2 when the body 2 is fitted into the body 2. Further, a rectangular recess 2e that communicates with the opening 1a is also formed along the axial direction on the flat surface of the distal end of the main body 2. The width of the recess 2e is larger than the width of the tip of the sensing element 10, and the axial length of the recess 2e is a predetermined distance between the sensing element 10 and the tip when the sensing element 10 is disposed at a predetermined temperature, as shown in FIG. The dimensions are set such that a gap can be formed. Note that this gap is determined depending on the coefficient of thermal expansion of the detection element 10 and the holder 1, etc. The depth of the concave portion 2e, that is, the radial length thereof is determined at least by the detection element 1 as shown in FIG.
0, and defines a space in which an elastic member 4a, which will be described later, is accommodated. A concave portion 3 having the same shape as the concave portion 2e is also provided on the flat surface of the distal end of the lid body 3 at a position opposite to the concave portion 2e.
e is formed. Therefore, when the lid 3 is fitted to the main body 2 as shown in FIG.
A recess with a rectangular bottom opening is formed, and the tip of the detection element 10 is loosely fitted into this recess.

As shown in FIG. 3, the detection element 10 includes a thin film-like intake air temperature detection resistor 1 approximately in the center of the plate surface of a rectangular flat base material 11.
2 and a flow velocity detection resistor 13 are attached. Base material 11
is, for example, a zirconia substrate, and vapor deposition is performed on this base material 11.
A thin film of a resistor such as nickel or platinum is attached by firing or the like to form the intake air temperature detecting resistor 12 and the flow rate detecting resistor 13. Both the intake air temperature detection resistor 12 and the flow velocity detection resistor 13 have a large change in resistance value with respect to temperature, that is, a temperature coefficient, and exhibit linearity, but the value of the resistance R of the flow velocity detection resistor 13 and the intake air The value of the resistance Ra of the temperature detection resistor 12 is set to be R8 (Rd).

The flow velocity detection resistor 13 is provided at the tip of the base material 11, and is bent in a U-shape when viewed from above, and is formed so that the entire resistor generates heat uniformly. A pair of bonding pads 15 are electrically connected to the open ends of the flow rate detection resistor 13, and these bonding pads 15 are connected to the base material 1.
1 extends in the longitudinal direction and reaches the base end of the base material 11.

The intake air temperature detection resistor 12 is formed by attaching to a plate surface a resistor that is bent in a continuous substantially S-shape and has a pair of open ends juxtaposed. Then, the intake air temperature detection resistor 12
A pair of bonding pads 14 are electrically connected to the pair of open ends, respectively, and the bonding pads 14 are connected to the base material 1.
1 extends in the longitudinal direction and reaches the base end of the base material 11.

This bonding pad 14 and the above-mentioned bonding pad 15 are both made of gold, aluminum, etc., and are attached to the base material 11 by vapor deposition, firing, or the like. A glass protective film (not shown) is formed on the surfaces of the intake air temperature detection resistor 12 and the flow rate detection resistor 13.

As shown in Figure 1, elastic members 4a and 4b are housed in the recess 2el of the main body 2 and the recess 3e of the lid 3, respectively.
When the lid body 3 is combined with the main body 2, the base material 11 of the detection element 10
The tip is slidably sandwiched therebetween.

The detection element 10 configured as described above is shown in FIG. 2(a).
'EL and its proximal end is connected to the holder 1 as shown in Figure 3.
The bonding pads 14 and 15 are fitted into the recess 2d of the main body 2 and connected to the lead wire 18 buried in the axial direction of the main body 2.
are electrically connected. Then, the lid body 3 is pressed against the main body 2, and the engagement protrusions 2a, 2b, 2c and the engagement protrusion 3a
, 3b, and 3c connect the two. Incidentally, the assembly may be performed after applying an adhesive to the mutually opposing flat parts of the main body 2 and the lid 3. Alternatively, the two may be welded together.

Thus, the base end portion of the detection element 10 is fitted into the recess 2d of the main body 2, and is fixed in a sandwiched manner between the flat portion of the lid body 3 and the flat surface portion of the lid body 3. As shown in FIG. 1, the tip of the detection element 10 is held between the elastic members 4a and 4b, and the recesses 2e and 3
Since a predetermined gap is formed between the bottom surface of the recess formed by the holder 1 and the bottom surface of the recess formed by It never touches the bottom surface.

As shown in FIGS. 4 and 5, the holder 1 is fixed to a case 19 containing a detection circuit (not shown), and this case 19 is fixed to an intake cylinder 20 of an internal combustion engine. In this case, the holder 1 is arranged so that the plate surface of the detection element 10 is parallel to the flow of intake air, and therefore the intake air temperature detection resistor 12 and the flow rate detection resistor 13 are both on a plane parallel to the flow of intake air. will be placed in The detection element 10 is connected to a detection circuit inside the case 19 via a lead wire 18. The detection circuit is equipped with a bridge circuit including an intake air temperature detection resistor 12 and a flow rate detection resistor 13, and is similar to the circuit described in Japanese Utility Model Application Publication No. 1988-195229 filed by the present applicant. Since the configuration is as follows, the explanation will be omitted.

To explain the operation of the embodiment of the present invention having the above configuration, when intake air is not introduced into the intake cylinder 20 in FIGS. 4 and 5, the flow velocity detection resistor 13 is detected by the intake air temperature detection resistor 12. A predetermined temperature difference ΔT compared to the intake air temperature
The temperature is high, and the equilibrium condition for the bridge circuit is established in this state. When the intake air is introduced into the intake cylinder 20, the amount of heat is taken away by the intake air, so that the predetermined temperature difference ΔT of the flow rate detection resistor 13 cannot be maintained. Therefore, in order to maintain the predetermined temperature difference ΔT, the flow velocity detection resistor 13
An additional current must be supplied to the intake air, and this required supply current has a predetermined relationship with the flow rate of the intake air; the higher the flow rate, the greater the required supply current. In other words, as the required supply current to maintain the predetermined temperature difference ΔT increases, the flow velocity increases;
Therefore, the flow rate is large. Thus, the output taken out as a voltage signal corresponding to the current supplied to the flow rate detection resistor 13 indicates the flow rate of the intake air, and hence the amount of intake air.

In the above detection operation, the detection element 10 has its base end fixed to the holder 1 as shown in FIG. 1, and its tip end sandwiched between the elastic members 4a and 4b. Even if vibrations of the internal combustion engine are transmitted through the sensor, there is no risk that the detection element 10 will resonate. Further, self-supporting vibrations are not generated in the detection element 10 due to the intake air flow. Therefore, the thickness of the base material 11 of the detection element 10 is set to be thin, which not only reduces the resistance to the intake air, but also
The amount of heat conducted to the attachment portion of the detection element 10 to the holder 1 can also be kept small. Furthermore, holder 1 and detection element 1
Even if a relative movement occurs between the two due to the difference in the coefficient of thermal expansion between is,
Detection errors due to thermal expansion do not occur.

6 and 7 show other embodiments of the detection element in the intake air amount detection device of the present invention, and FIGS.
Parts that are substantially the same as those in the embodiment shown in the figures are given the same reference numerals. In these embodiments, a slit is formed in the base material and the shape of the tip is different from that in the embodiments shown in FIGS. 1 to 3. That is, as shown in FIGS. 6 and 7, slits 31a and 41a extending in the elongated direction are formed at the center of the plate surfaces of the base materials 31 and 41, and thereby the flow velocity detection resistor 13 Heat conduction between the intake air temperature detection resistor 12 and the intake air temperature detection resistor 12 is cut off.

The slits 31a and 41a are connected to the intake air temperature detection resistor 12, respectively.
The base material 31, 41 heated by each flow velocity detection resistor 13 is formed between the base material 31, 41 and the bonding pads 14 and 15, and is It is preferable to form it so that it extends to a position where the temperature is approximately equal to the temperature of the surrounding intake air. At this time,
As in the detection element 30 in FIG.
1, a narrow support portion 31b is formed on the base material 31 to extend from the tip portion of the base member 31 as an extension of the attachment portion of the intake air temperature detection resistor 12.

The tip of the support portion 31b is disposed within the recess 2e of the main body 2 and supported in the same manner as in the embodiment shown in FIGS. 1 to 3. With this configuration, the generation of vibrations in the flow rate detection resistor 13 is suppressed, and it is separated from the joint with the main body 2, resulting in a preferable support structure.

In addition, when the slit 47a is opened at the tip of the base material 31 as in the detection element 40 in FIG. The support portion 41b is formed to extend, and the tip of the support portion 41b is connected to the main body 2.
It is disposed within the recess 2e and supported in the same manner as the embodiment shown in FIGS. 1 to 3. As a result, the occurrence of vibration in the flow rate detection resistor 13 is suppressed, and the path from the flow rate detection resistor 13 to the joint with the main body 2 is shorter than in the embodiment shown in FIG. 6, but the intake air temperature detection resistance The ability to block heat conduction from the body 12 is improved.

The detection operation of the embodiment shown in FIGS. 6 and 7 is basically the same as that of the embodiment shown in FIGS. 1 to 3, so a description thereof will be omitted.

[Effects of the Invention] Since the present invention is configured as described above, it produces the effects described below.

That is, in the intake air amount detection device of the present invention, the base end of the base material of the detection element is fixed, and the distal end portion is held between the elastic members.
Alternatively, vibrations of the detection element that may occur due to the intake air flow can be suppressed, and stable detection accuracy can be ensured.

Moreover, since the relative slI between the holder and the detection element due to the difference in coefficient of thermal expansion between the two is absorbed by the support structure at the tip of the detection element, detection errors due to thermal expansion will not occur.

In addition, as mentioned above, the occurrence of vibration of the detection element is suppressed,
Since the thickness of the base material can be reduced, a stable flow of intake air can be ensured, and the heat insulation effect between the flow velocity detection resistor and the holder can be increased.

[Brief explanation of drawings]

FIG. 1 is a partially sectional plan view of a holder and a detection element in an embodiment of the present invention, and FIG. 2(a) is the same, and II in FIG.
-If line sectional view, FIG. 2(b) is the same, side view of the holder,
Figure 3 is the same, sectional view taken along line III-111 in Figure 1, and Figure 4.
The figure is a plan view of an intake air amount detection device according to an embodiment of the present invention, FIG. 5 is a longitudinal cross-sectional view of the device, and FIG. , FIG. 7 is a front view of a holder equipped with still another embodiment of the detection element according to the present invention. 1... Holder, 2... Main body, 3... Lid body. 4a, 4b...Elastic member, 10...Detection element. 11...Base material, 12...Intake air temperature detection resistor. 13...Flow velocity detection resistor, 14.15...Ponding pad, 19...Case, 20.
...Intake cylinder patent applicant Aisan Industry Co., Ltd.

Claims (1)

[Claims] (1) A flow velocity detection resistor consisting of a flat base material and a thin film resistor attached to the plate surface of the base material, the resistance of which changes at least in response to temperature changes due to the flow velocity of the intake air to be measured. In the intake air amount detection device in which a detection element having a body is arranged in an intake cylinder so that a plate surface of the base material is parallel to the flow direction of the intake air, the detection element is opened in at least the flow direction of the intake air. The detection element is housed in the opening of the holder, the base end of the base is fixed, and the distal end of the base is fixed through an elastic member. An intake air amount detecting device, characterized in that the intake air amount detecting device is supported by the holder so as to be held by the base material and to allow movement of the tip end of the base material in the axial direction.