JPH02262011A - Apparatus for detecting amount of intake air - Google Patents

Abstract

PURPOSE:To shorten the distance in the direction of an air flow, to make the distribution of temperature adequate all the time and to secure stable detecting accuracy by using a strip shaped resistor for a flow-speed detecting resistor, and arranging a pair of lead members on both surfaces. CONSTITUTION:A base material 11 of a detecting element is divided into two parts with a slit 11a. An intake-air-temperature detecting resistor 12 is formed at the wide part. A pair of lead members 14a and 14b are electrically connected to the resistor. Lead members 15a and 15b are juxtaposed on the narrow part of the base material 11. A flow-speed detecting resistor 13 is attached to the upper surface of the members 15a and 15b. The resistor 13 is formed in a strip shape with a thin film of platinum and the like. Since the width of the strip shaped resistor, i.e. the distance in the direction of the intake-air flow is short in this constitution, the different temperature distributions are not formed at the input side and the opposite side as shown in a conventional device, and the uniform distribution is obtained. Therefore, the detecting accuracy can be maintained highly accurately all the time regardless of the flow speed of the intake air and the magnitude of the amount of the air.

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. Japanese Utility Model Application Publication No. 183825/1983 describes a technique in which all the resistors including the heating resistor are formed of thin film resistors to form one element.

The flow rate detection devices described in the above-mentioned publications are all of the indirect heating type in which the flow rate detection element is heated by a heating resistor. There is also a direct heating type, that is, a self-heating type, in which the body itself generates heat. The flow rate detection element described in this publication has a thin film resistor attached to one base material, and this base material is supported in a cantilevered manner.

Further, Japanese Patent Application Laid-Open No. 60-236029 discloses a directly heated air flow sensor, in which a base material provided with an abdominal resistor is supported at both ends by lead members. This publication focused on the temperature distribution within the membrane resistor, and by making the resistance value per unit area on the upstream side larger than that on the downstream side, the amount of heat generated on the upstream side was made larger than that on the downstream side. The aim is to make the temperature distribution uniform.

Regarding the flow rate detection element in the flow rate detection device, it is necessary to change the temperature according to the flow rate of the intake air.
If the flow rate detection element itself or other changes in the situation become factors influencing the temperature change, accurate flow rate detection becomes difficult. Therefore, as in the technique described in the above-mentioned publication, each detection element is formed into a thin flat plate shape and arranged parallel to the flow direction of the intake air.

In this case, the amount of heat generated by the flow velocity detection element is
It is transmitted to the ambient air and to the attachment to the intake air passage.

When the flow velocity of the intake air is high, most of the calorific value is transferred to the surrounding air, but when the flow velocity of the intake air is slow, the amount of heat conducted to the surrounding air is small, and the mounting portion The amount of heat conduction to increases. The amount of heat conduction to this mounting part changes depending on the intake air temperature and the temperature of the intake cylinder, so
The current supplied to the bridge circuit described above changes, thus reducing the accuracy of detecting the flow velocity.

To solve this problem, Japanese Patent Laid-Open No. 151020/1984 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. ing.

Furthermore, according to the detection element described in the above-mentioned Japanese Unexamined Patent Publication No. 57-201858, by using a thin base material and a material with low thermal conductivity, the portion where the thin film resistor is provided can be kept at a predetermined temperature below the intake air temperature. Even when it is set high, heat conduction to the mounting portion provided on the opposite side of the thin film resistor is suppressed.

[Problems to be Solved by the Invention] In summary, in the intake air amount detection device described in the above publication, the temperature distribution of the thin film resistor extending in the flow direction of the intake air, or the base material, Considering the temperature distribution based on heat conduction to the resistor mounting part such as lead wires,
Measures have been taken in the structure, arrangement, etc. of each component including the resistor. However, in devices equipped with a thin film resistor that extends in the direction of flow of the intake air, measures are taken to assume that the distance in the flow direction of the intake air in the thin film resistor is fixed, and the distance in the flow direction is No consideration is given to making it shorter, that is, narrowing the width.

Figure 5 shows the patent application No. 63-2269 filed by the applicant.
This is a detection element 100 used in the intake air amount detection device disclosed in No. Electrically connected lead members 140 and 150 are attached toward the base end of the base material 110. Note that the white arrow in the figure indicates the flow direction of the intake air to be measured. According to this, the flow velocity detection resistors 1 and 30 are formed in a U-shape in plan view, and the dimensions in the flow direction of the intake air, that is, the flow velocity detection resistor The width of 130 can be kept small and a good temperature distribution can be formed.

However, even in the detection element 100, the temperature distribution changes depending on the amount of intake air, and some kind of compensation means is required. That is, as shown in the graph on the right side of FIG. 5, when the flow velocity of the intake air is high and the amount of intake air is large, the heat transfer coefficient to the intake air becomes large, so that the flow rate detection resistor 130 The temperature distribution shows a rapid attenuation in the area close to the intake air, and a gradual attenuation on the opposite side (see "Ho" in Figure 5).
), and when the flow velocity of the intake air is small and the amount of intake air is small, the temperature distribution becomes gradually attenuated (indicated by " in Figure 5).
(indicated by "Lo"). Since the total amount of heat dissipated from the flow rate detection resistor 130 is determined by these temperature distributions, changes in the temperature distribution end up causing detection errors. Although this detection error is minute compared to conventional devices, it is desirable to further reduce this error. Incidentally, in FIG. 5, the vertical dotted line indicates the intake air temperature level, and the left side in the figure is the high temperature side.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a flow rate detection resistor in an intake air amount detection device that can always form an appropriate temperature distribution regardless of the flow rate of the intake air or the magnitude of the amount of intake air.

[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. In an intake air amount detection device disposed in an intake cylinder such that the plate surface of the base material is parallel to the air flow direction, a resistor constituting the flow velocity detection resistor is formed in a band shape, and the base material The first of the pair of lead members includes a pair of conductors extending in the longitudinal direction on the plate surface and arranged in parallel in the width direction and electrically connected to the flow velocity detection resistor. A lead member is attached to the base material from the base end to the distal end of the base member, the strip resistor is attached to the upper surface of the first lead member via an insulating member, and the strip resistor is one end in the longitudinal direction is electrically connected to the base material tip position of the first lead member;
and a second lead member of the pair of lead members is attached to the base member from the base end of the base member to the other end in the longitudinal direction of the strip resistor member, and is electrically connected to the strip resistor member. This is what I did.

[Operation] In the intake air amount detection device configured as described above, the flow rate detection resistor of the detection element is composed of a strip-shaped resistor interposed between a pair of lead members. The detection element is arranged in the intake cylinder so that the width direction of the flow velocity detection resistor is parallel to the flow of intake air, and includes the flow velocity detection resistor to form, for example, a bridge circuit.

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. In this control, the intake air introduced into the intake cylinder comes into contact with the entire length of the flow velocity detector, but since the width of the band-shaped resistor, which is the flow velocity detector, is short, that is, the distance in the flow direction of the intake air, The temperature distribution as before is no longer formed, and a uniform temperature distribution immediately reaches the intake air temperature at the boundary with the intake air. Further, there is no possibility that a large change in temperature distribution occurs due to a change in the amount of intake air.

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

1 and 2 are a front view and a bottom view of a detection element 10 used in an embodiment of the intake air amount detection device of the present invention,
The white arrow in FIG. 1 indicates the flow direction of intake air.

As shown in FIG. 1, the detection element 10 has a thin film-like intake air temperature detection resistor 12 and a flow velocity detection resistor 13 attached to the plate surface of a rectangular flat base material 11. The base material 11 is a flat zirconia substrate, and a slit lla is formed in the longitudinal direction of the plate surface of the base material 11. The base material 11 is formed so that one side is wider than the other side through a slit lla, and a thin film of a resistor such as nickel or platinum is adhered to the plate surface of the tip part by vapor deposition, baking, etc., and the above-mentioned An intake air temperature detection resistor 12 is formed.

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 lead members 14a and 14b are electrically connected to the pair of open ends of the lead members 14a and 14b, respectively, and extend in the longitudinal direction of the base material 11 to reach the base end of the base material 11. This lead member 14a, 1
4b is made of gold, for example, and is formed by vapor deposition, firing, etc.
1.

A pair of narrow conductors, for example, lead members 15 made of gold wire, extend in the longitudinal direction of the base material 11 at the tip of the plate surface of the narrow portion.
a and 15b are arranged in parallel in the width direction of the base material 11. The lead member 15a is attached to the base material 11 from the base end to the distal end by vapor deposition, firing, or the like. An insulating member 16 made of silicon dioxide or the like is attached to the upper surface of this lead member 15a, and a flow velocity detection resistor 13 is further attached to the upper surface thereof. The flow rate detection resistor 13 is formed into a strip-like shape using a thin film of a resistor such as platinum. The lead member 15a is joined and electrically connected to one longitudinal end of the flow velocity detection resistor 13 at the tip of the base member 11.

The lead member 15b is juxtaposed to the lead member 15a, and is attached from the base end of the base member 11 to the other longitudinal end of the flow velocity detection resistor 13. bonded and electrically connected. Thus, the lead member 15a corresponds to the first lead member and the lead member 15b corresponds to the second lead member according to the present invention.

In addition, the above-mentioned intake air temperature detection resistor 12 and flow rate detection resistor 1
A glass protective film (not shown) is formed on the surface of 3. In addition, both the intake air temperature detection resistor 12 and the flow rate detection resistor 13 have a large resistance value change with respect to temperature, that is, a large temperature coefficient.
In addition, the value of the resistance R3 of the flow rate detection resistor 13 and the value of the resistance RT of the intake air temperature detection resistor 12 are set to be R3 (Rt), which indicates linearity.The slit 11a is From the tip of the base material 11, the flow velocity detection resistor 13
It extends to a position where the temperature of the base material 11 heated by the heating is approximately equal to the temperature of the surrounding intake air. Incidentally, instead of the slit lla, a plurality of holes may be bored or a groove may be formed.

As a result, heat conduction between the intake air temperature detection resistor 12 and the flow velocity detection resistor 13 is cut off.

The detection element 10 configured as described above is supported by a holder 1, as shown in FIG. 3, and the holder 1 is fixed to an intake cylinder 20 of an internal combustion engine. In this case, the detection element 1
0 is arranged so that its plate surface is parallel to the flow of intake air, and therefore the intake air temperature detection resistor 12 and the flow velocity detection resistor 13 are both arranged on a plane parallel to the flow of intake air. The detection element 10 includes lead members 14a, 1
4b, 15a, and 15b, and are connected to a detection circuit in the case 19 through lead wires (not shown) that are electrically connected to each of them. 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 no intake air is introduced into the intake cylinder 20 in FIGS. 3 and 4, the flow rate detection resistor 13 is detected by the intake air temperature detection resistor 12. The predetermined temperature difference △T 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.

Since the flow velocity detection resistor 13 is controlled to a temperature that is a certain temperature ΔT higher than the intake air temperature, there is a possibility that heat may transfer from the flow velocity detection resistor 13 to the vicinity of the intake air temperature detection resistor 12 and the base material 11. , Due to the presence of the slit lla, the amount of heat transferred from the flow rate detection resistor 13 to the intake air temperature detection resistor 12 is extremely small, and the intake air temperature detection resistor 12 accurately corresponds to the actual intake air temperature.

In addition, since the flow rate detection resistor 13 is always controlled to a temperature ΔT higher than the intake air temperature even if the flow rate changes,
The amount of heat released from the flow velocity detection resistor 13 to the intake air follows the change in flow velocity without delay. At this time, the temperature distribution of the amount of heat generated in the flow velocity detection resistor 13 in the width direction of the base material 11 has a small difference depending on the flow velocity of the intake air, as shown on the right side of FIG. It can be suppressed. The vertical dot-dash line in the graph on the right side of FIG. 1 indicates the intake air temperature, H indicates the temperature distribution in the width direction of the flow velocity detection resistor 13 when the intake air flow velocity is high, and L indicates the flow velocity is small. ing.

Note that the flow rate detection resistor 13 can also be applied to an indirect heating type detection element equipped with a heating resistor, and the same effect can be ensured.

[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 flow velocity detection resistor attached to the detection element is a strip resistor, and a pair of lead members are arranged on both sides of the resistor, so that the flow direction of the intake air can be adjusted. The distance is short, the temperature distribution is always appropriate, and stable detection accuracy can be ensured.

[Brief explanation of drawings]

FIG. 1 is a front view of a detection element in an embodiment of the present invention;
2 is a bottom view of the same, FIG. 3 is a plan view of an intake air amount detection device according to an embodiment of the present invention, and FIG. 4 is a longitudinal sectional view of the same,
FIG. 5 is a front view of the detection element according to the application of the present applicant. DESCRIPTION OF SYMBOLS 1... Holder, 10... Detection element, 11.
··Base material. 12... Intake air temperature detection resistor, 13... Flow rate detection resistor, 14a, 14b river lead member (first lead member)'+ 15a, 15b... Lead member (second lead member) ), 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. A resistor constituting the flow velocity detecting resistor in the intake air amount detecting device in which a detecting element having a body is disposed in the intake cylinder so that the plate surface of the base material is parallel to the flow direction of the intake air. is formed into a band shape, and includes a pair of lead members extending in the longitudinal direction on the plate surface of the base material and consisting of a pair of conductors arranged in parallel in the width direction and electrically connected to the flow velocity detection resistor. , a first lead member of the pair of lead members is attached to the base material from the base end to the distal end of the base material, and the strip resistor is attached to the upper surface of the first lead member via an insulating member. At the same time, one longitudinal end of the strip resistor is electrically connected at the tip position of the base material of the first lead member, and the second lead member of the pair of lead members is attached to the base material. An intake air amount detection device characterized in that the device is attached to the base material from the base end of the material to the other end in the longitudinal direction of the strip resistor and is electrically connected to the strip resistor.