JPH0748054B2 - Heating resistance type air flow meter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat generation resistance type air flow meter for measuring an intake air flow rate of an internal combustion engine such as a gasoline engine, and particularly to an automobile whose main body is made of synthetic resin. TECHNICAL FIELD The present invention relates to a heating resistance type air flow meter suitable for measuring the intake air flow rate of a gasoline engine for automobiles.

[Conventional technology]

In recent years, a heat resistance type air flow meter has been widely adopted for measuring an intake air flow rate of a gasoline engine for an automobile. As this heat resistance type air flow meter, for example, Japanese Patent Application No. 1-30846 can be used. As described in the specification, there is an axial flow path type heating resistance air flow meter.

In the heating resistance type air flow meter described in this specification, the bypass passage portion is configured as a bypass bridge portion having a bypass passage inlet, and the bypass bridge portion is formed integrally with the main body of the air flow meter. The passage cover is attached by screwing it from the downstream side of the air flow.

Examples of related devices of this type include those disclosed in JP-A-63-55419, JP-A-1-91018, and JP-A-1-126513.

[Problems to be Solved by the Invention]

The above-mentioned prior art does not consider that the member forming the bypass passage is separated from the main body body due to vibration, thermal expansion, or the like during use while being installed in the engine, and the member is separated from the main body body. In this case, there is a problem that the engine may be damaged.

Further, in the above-mentioned prior art, the consideration of using synthetic resin for the body material of the main body is not sufficient, and there is a problem of deterioration of radio wave interference resistance due to the use of synthetic resin.

An object of the present invention is to provide a hot-wire air flow meter that does not separate the member forming the bypass passage from the main body body even when vibrating or thermally expanding, and does not cause the risk of engine damage. is there.

Another object of the present invention is to provide a heating resistance type air flow meter capable of always measuring an accurate air flow rate without fear of deterioration of the radio wave interference resistance even if the main body body is made of synthetic resin.

[Means for Solving the Problems]

In order to achieve the above object, the present invention is one in which a member forming an axial flow bypass passage is mounted from an upstream side of an air passage, and a heat ray element is provided even when a main body body is made of synthetic resin. The bypass passage cover to be held is made of a conductive material.

[Action]

Since the bypass passage cover that constitutes the axial flow bypass passage is attached from the upstream side of the air passage, the force in the direction of being pressed against the attachment surface acts on the bypass passage cover due to the air flow in the air passage, There is no risk that the bypass passage cover will fall off the main body.

Even if the main body is made of synthetic resin, since the material of the bypass passage cover that holds the heat ray element is conductive, grounding this will provide a radio wave shielding function and prevent deterioration of radio wave interference resistance. .

〔Example〕

Hereinafter, a heating resistance type air flow meter according to the present invention will be described in detail with reference to the illustrated embodiments.

1 to 3 show one embodiment of the present invention, FIG. 1 is an exploded perspective view, FIG. 2 is a vertical sectional view, and FIG. 3 is a plan view. As shown in these drawings, The heating resistance type air flow meter according to this embodiment is roughly classified into a body 5 having a main passage 1 and a control module 8 for generating a flow rate detection signal.
It consists of and.

The main passage 1 constitutes a part of the intake passage of the engine, and the air taken in by the engine flows through the main passage 1 in the direction of the arrow in FIG. Therefore, in FIGS. 1 and 2, the upper side of the drawing is the upstream side of the air passage, and FIG. 3 is the view seen from the upstream side.

Reference numeral 2 denotes a bypass passage, which is formed by a bypass passage cover 6, an inlet 2a of which is open in the upstream side at substantially the center of the main passage 1, and air which has flowed in from there is bypassed by a bypass bridge 14 integrated with the body 5. It is configured such that it is divided into both sides at the center on the downstream side by the formed passage, and rejoins into the main passage 1 from the outlets 14a and 14b opening in the vicinity of the peripheral portion of the main passage 1.

Reference numeral 3 is a heat ray element, and 4 is a temperature sensitive resistance element. These are extended from the control module 8 so as to be positioned in the bypass passage 2 as apparent from FIGS. 2 and 3. It is attached to the tip of the holder 10.

In the bypass passage 2, an air amount of 1 to 3% of the air amount flowing in the main passage 1 flows, and by detecting this air flow rate, the total air flow rate passing through the main passage 1, that is, the intake air flow rate of the engine is determined. It is designed to measure.

Reference numeral 16 is a tubular portion formed in the bypass passage cover 6, and as is particularly clear from FIG. 1, the holder 10 of the control module 8 is inserted through the insertion hole 5a formed in the body 5. ing.

Therefore, in this embodiment, as shown in FIG.
The bypass passage cover 6 is inserted into the main passage 1 from the upstream side of the body 5, and the holder 10 of the control module 8 is inserted into the tubular portion 16 of the bypass passage cover 6 through the insertion hole 5a of the body 5. However, by tightening the bypass passage cover 6 to the bypass bridge 14 from the upstream side by the two screws 7, the bypass passage 2 is assembled, and as a result, the bypass passage cover 6 and the screws are assembled. 7 is subjected to the force of being pressed against the bypass bridge 14 by the air flowing from the upstream side to the downstream side in the main passage 1, and should be dropped into the main passage 1 by any chance. Furthermore, since the holder 10 is inserted into the tubular portion 16 through the insertion hole 5a, the holding of the bypass passage cover 6 is also provided by this. After all, according to this embodiment, the double mounting is performed, and the drop can be reliably prevented.

Here, the control module 8 is mounted with screws after the metal base 11 is positioned by the mounting seat 5b of the body 5, and at this time, the insertion hole 5a is shown in FIG. As described above, an O-ring 9 is provided so that a predetermined air sealing property is provided.

Next, FIG. 4 shows another embodiment of the present invention.
6A is a bypass passage cover made of a conductive material, for example, a metal material such as aluminum, 12 is a holder sleeve made of a conductive material, and the others are the first
Same as the embodiment of FIGS. 3 to 3, except that the body 5 is made of a suitable synthetic resin material, for example a plastic material such as PBT (polybutylene terephthalanol), PET (polyethylene terephthalanol). .

The use of synthetic resin for such a heating resistance type air flow meter is an extremely effective means for reducing weight and cost,
On the other hand, there is a problem that the radio wave interference resistance of the flowmeter is greatly deteriorated. In other words, if the body 5 and the like are made of synthetic resin, the function of shielding against radio waves is lost, and the heat ray element and the heat-sensitive resistance element existing in the bypass passage function as an antenna, which causes radio waves to be picked up and malfunction. is there.

Characteristic 7a in Fig. 7 shows the result of measuring the electromagnetic interference resistance characteristics of a synthetic resin heat resistance type air flow meter by the TEM CELL method. It decreased to 20 V / m or less at a specific frequency. You can see that

In general, it is known that an electronic device related to engine control mounted on a car malfunctions under the influence of radio waves at a voltage of about 20 V / m or less, causing problems such as engine stop and runaway.

According to the embodiment of FIG. 4, however, the bypass passage cover 6A is made of an electrically conductive material, which is connected to the control module 8 via a holder sleeve 12 which is also made of an electrically conductive material. Since it is electrically connected to the metal base 11 and, as a result, it is kept at the ground potential, the heat ray element 3 and the heat sensitive resistance element 4 are sufficiently shielded by the bypass passage cover 6A, so that the body 5 Even if all other parts are made of synthetic resin, as shown in the characteristic 7b in Fig. 7, an electric field strength of about 9V / m or more is obtained over the entire measurement frequency range, and sufficient electromagnetic interference resistance is ensured. Can be given to.

Next, FIG. 5 shows still another embodiment of the present invention, which is a portion (first part) of the tubular portion 16 of the bypass passage cover 6.
The part indicated by 16a in the figure) is removed, and the control module 8
The holder 10 is directly exposed to the air flow in the main passage 1. At this time, the O-ring 13 is provided at the tip of the holder 10 and the tubular portion 16 is partially removed. It is intended to reliably prevent the leakage of the air that has come to be obtained.

According to the embodiment shown in FIG. 5, since the holder 10 is sufficiently cooled by the air flow, the heat-sensitive resistance element 4 is not affected by the heat transferred from the holder 10, and the air is reliably transferred. The temperature can be compensated by the temperature, and accurate flow rate measurement can be easily obtained.

This will be described below. First, FIG. 8 shows the temperature characteristic of the inner wall of the main passage of the heating resistance type air flow meter. It is assumed here that a part of the tubular portion 16 is not removed. , The temperature of the inner wall of the main passage is conducted to the thermosensitive resistance element 4 through the holder 10, and as a result,
At this time, as shown by the characteristic 8a in FIG. 8, when the air flow rate is Q, in the measurement region near Q = 10 to 20 Kg / h, the measurement error ΔQ / Q = + 8%, which is a considerably large value. However, this causes a great decrease in driving stability when the vehicle is mounted, especially at the time of starting the engine.

Therefore, according to the embodiment of FIG. 5, the temperature of the holder 10 is maintained at the temperature of the air in the main passage 1,
The thermal effect on the thermal resistance element 4 due to this is completely eliminated, and the measurement error ΔQ / Q = +, as shown by the characteristic 8b in FIG.
It can be suppressed to about 2%, and as described above, accurate flow rate measurement can be easily obtained, and the engine can always be controlled accurately and stably.

Further, FIG. 6 is also an embodiment of the present invention. In this embodiment, an O-ring 15 is interposed at a joint portion of the bypass passage cover 6 with respect to the bypass bridge 14, so that a sealing property between these members can be easily obtained. The other structure is the same as that of the embodiment described in FIGS. 1 to 5.

According to this embodiment, even if the finishing accuracy of the joint portion between the bypass passage cover 6 and the bypass bridge 14 is lowered, the reliable sealing property can be easily obtained, which is advantageous for synthetic resin. .

Further, instead of the O-ring 15 in the embodiment of FIG. 6, a proper adhesive may be used to obtain a seal between the bypass passage cover 6 and the bypass bridge 14.
Then, at this time, if a predetermined reliability can be expected in the adhesion by the adhesive to be used, as shown in FIG. 1 and FIG.
The screws 7 for mounting may be omitted, and the assembly may be performed only by joining with an adhesive, which further reduces the cost.

Further, at this time, in the examples made into synthetic resin,
It goes without saying that a thermocompression bonding method or an ultrasonic bonding method may be used for assembling the bypass passage cover 6 and the bypass bridge 14 described above.

〔The invention's effect〕

According to the present invention, the member forming the axial flow bypass passage,
Since it is installed from the upstream side of the air passage, the members will not fall off due to vibration or thermal stress, engine damage can be reliably eliminated, and the deterioration of the electromagnetic interference resistance due to the use of synthetic resin is easy. Because it can be suppressed to
It is possible to provide a highly accurate heating resistance type air flow meter at low cost.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a heat resistance type air flow meter according to the present invention, FIG. 2 is a longitudinal sectional view, FIG. 3 is a plan view, FIG. 4, FIG. 5, and FIG. FIG. 7 is a partial cross-sectional view showing another embodiment of the present invention, FIG. 7 is a characteristic view showing resistance to radio wave interference, and FIG. 1 ... Main passage, 2 ... Bypass passage, 3 ... Heat wire element, 4 ... Heat resistance element, 5 ... Body, 6 ... Bypass passage cover, 7 ... Mounting screw, 8 ... Control module , 9, 13, 15 ... O-ring, 10 ... Holder, 11 ...
… Metal base, 12 …… Holder sleeve, 14 …… Bypass bridge, 16 …… Tubular part.

Claims (11)

[Claims] 1. An axial flow bypass type heat resistance type air flow meter of a type in which a detection element is arranged in a bypass passage arranged in a main air passage, wherein the main flow passage has an upstream side in an air flow direction. A bypass bridge member having a facing mounting surface is provided, and a bypass passage cover member forming the bypass passage is inserted and mounted on the mounting surface of the bypass bridge member from the upstream side in the air circulation direction of the main air passage. A heat resistance type air flow meter characterized by being installed. 2. A main body for inserting a bypass passage inlet opening opening at an upstream side in the air flow direction and a holder member of a control module into the bypass passage cover member. An exothermic resistance type air flow meter, characterized in that a tubular portion opened toward the inner wall surface of the air passage is formed. 3. The bypass passage cover member according to claim 1, wherein the bypass passage cover member is attached to the bypass bridge member by a mounting screw adapted to be screwed from an upstream side in the air circulation direction. A heating resistance type air flow meter. 4. The holder member according to claim 2, wherein the holder member is inserted into the tubular portion of the bypass passage cover member from the outside of the wall portion of the air passage through a hole formed in the wall portion. A heat resistance type air flow meter, which is characterized in that 5. The heating resistance type air flow rate according to claim 1, wherein at least the bypass passage cover member is made of a conductive material, and the cover member is kept at a ground potential. Total. 6. The heating resistance type air flow meter according to claim 5, wherein the bypass passage cover member is electrically connected to the conductive base of the control module. 7. The invention according to claim 6, wherein the electrical connection between the bypass passage cover member and the conductive base of the control module is fitted into a hole formed in the wall portion of the air passage. A heating resistance type air flow meter, characterized in that it is configured to be provided by a metallic holder sleeve. 8. The invention according to claim 4, wherein at least a part of the tubular portion of the bypass passage cover member is removed, and at least a part of the holder member is directly exposed to the air flow in the main air passage. A heat resistance type air flow meter characterized by being configured. 9. The heating resistance type air flow rate according to claim 1, wherein an O-ring is provided with a sealing function at a mounting portion of the bypass passage cover member to the bypass bridge member. Total. 10. The heating resistance type device according to claim 1, wherein a sealing function at a mounting portion of the bypass passage cover member to the bypass bridge member is provided by applying an adhesive material. Air flow meter. 11. The invention according to claim 1, wherein the bypass passage cover member and the bypass bridge member are formed of a predetermined synthetic resin material, and the bypass passage cover member is attached to the bypass bridge member by thermocompression bonding or super-pressure welding. An exothermic resistance type air flow meter characterized in that it is provided by at least one of sonic bonding.