JPS63210717A - Air flowmeter - Google Patents

Abstract

PURPOSE:To accurately measure intake air capacity and to manufacture a flowmeter efficiently at low cost by forming at least the tip part side of a sensing passage by using members different from a flowmeter main body. CONSTITUTION:A collar 3 and a terminal collar 4 which constitute the sensing passage 21 are formed of the members different from the upstream-side body 1 of the flowmeter 100 and then only the collar 3 and terminal collar 4 are only formed corresponding to respective factors; and common components are usable as other components such as a body except the collar 3 and terminal collar 4. For example, the collar 3 is replaced with a collar 3A which is formed in the best shape to the best length corresponding to factors of the discharge, number of cylinders, intake pipe shape, intake pipe length, etc., of an internal combustion engine and then even when other components except the collar 3A are made common, the sensing passage 21 is settable to the best shape and length corresponding to the respective factors. Consequently, intake air capacity is accurately measured and the flowmeter is manufacture efficiently at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an air flow meter, and in particular to an air flow meter that is placed in the intake pipe of an internal combustion engine and uses a hot wire sensor such as platinum as the sensor. It is related to the meter.

(Prior Art) There are various types of air flow meters placed in the intake pipe of an internal combustion engine. Among them, the so-called hot wire type air flow meter that uses a hot wire such as a platinum wire as a sensor is one of the most popular types. It is widely used because of its good response and ability to measure the mass of air flowing per unit time.

In such an air flow meter, the sensor is disclosed in, for example, Japanese Unexamined Patent Publication No. 56-108911, Japanese Utility Model Application No. 59-1580.
As described in Japanese Patent Publication No. 30, etc., it is provided in a cylindrical body disposed in the intake pipe, or
As described in Japanese Patent No. 190623, etc., the bypass passage is provided in a straight portion of a bypass passage arranged to branch from an intake passage in an intake pipe.

(Problems to be Solved by the Invention) The above-described conventional techniques had the following problems.

(1) As is well known, to accurately measure air flow rate,
It is necessary to make the air flow as stable as possible so that it hits the sensor.

Therefore, the size and length of the cylindrical body or the bypass passage, the shape of its inner wall, etc. are determined by the displacement, the number of cylinders, or the length and shape of the intake pipe of the internal combustion engine in which the air flow meter is installed. It needs to be set accordingly.

However, as a result of this, if the form of the internal combustion engine or the vehicle in which the internal combustion engine is mounted changes, an air flow meter with a size and shape appropriate for the internal combustion engine or vehicle must be manufactured each time. It is not possible to mass-produce the device, and the manufacturing cost increases.

(2) When the sensor is installed in a cylindrical body disposed in the intake pipe, there is a lot of turbulence in the airflow within the cylindrical body;
It is difficult to achieve laminar air flow.

Another drawback is that when a backfire occurs, the sensor is easily damaged by the blast, which shortens the life of the air flow meter.

Furthermore, even when a backfire occurs, the blast wave is detected as intake air, making it impossible to accurately measure the amount of intake air.

(3) When the sensor is disposed in the bypass passage, the end of the bypass passage on the downstream side of the air flow is open to the inner side surface of the intake pipe, so the air in the bypass passage is is drawn in, and as a result, the air flow within the bypass passage tends to be relatively laminar.

However, since the straight portion of the bypass passage in which the sensor is disposed is bent and connected to the rear end portion of the bypass passage that opens to the inner side surface of the intake pipe, airflow is likely to be disturbed at the bent portion. Therefore, the sensor needs to be placed away from the downstream side of the air flow in the straight portion of the bypass passage.

As a result, the bypass passage must be formed relatively long, making the air flow meter complicated and large.

Furthermore, since the bypass passage is formed directly inside the side wall of the intake pipe or on the outer surface of the side wall, heat generated by the internal combustion engine is conducted to the wall surface constituting the bypass passage, and passes through the sensor or the bypass passage. There is a risk of the air being heated. This results in inaccurate airflow measurements.

The present invention has been made to solve the above-mentioned problems.

(Means and effects for solving the problems) In order to solve the above-mentioned problems, the present invention provides a sensing passage provided with a hot wire sensor inside the sensing passage, and an intake passage around the sensing passage. In addition, a communication passage is provided so as to communicate the sensing passage with a side surface of the intake passage, and a portion of the sensing passage constituting at least the upstream end of the air flow (hereinafter referred to as the tip) is The feature is that it is formed separately from the body of the air flow meter.

This allows at least the tip of the sensing passage to
The air flow meter can now be replaced depending on the type of internal combustion engine or vehicle, and the air flow meter has the effect of being able to share the parts other than the tip regardless of the type of internal combustion engine or vehicle. can be done.

Further, the air flowing into the sensing passage is sucked through the communication passage so as to spread radially by the airflow passing through the intake passage, so that the airflow within the sensing passage is reliably maintained. In addition to creating a laminar flow state, it is also possible to produce an effect that the blast wave caused by the backfire does not flow into the sensing passage where the sensor is arranged.

(Example) The present invention will be described in detail below with reference to the drawings.

Figure 1 is a cross-sectional view of Figure 3 taken along line B-B, Figure 2 is a side view of the first embodiment of the present invention, and Figure 3 is a book view of Figure 2 from the upstream side of the air flow. Front view of the first embodiment of the invention, fourth
The figure is a rear view of the first embodiment of the present invention when FIG. 2 is viewed from the downstream side of the air flow, and FIG. 5 is a cross-sectional view taken along the line CC in FIG. 1.

In FIG. 5, the cover 13 shown in FIGS. 1 to 4,
and the circuit board 11 (first
Figure) etc. are omitted.

First, in FIG. 2, an air flow meter 100 is placed in an intake pipe of an internal combustion engine mounted on a vehicle.

The air flow meter 100 has joints 101 at both ends.
and 102 are connected, the joint 101 is connected to the air cleaner (not shown) side of the intake pipe, and the joint 102 is connected to the fuel injection valve and throttle valve (both not shown) sides of the intake pipe. be done.

Therefore, air taken in from the air cleaner passes in the direction of arrow A.

Next, the first. 3. In Figure 5, upstream body 1
A large diameter portion IB having an inner diameter that is almost the same as the inner diameter of the joint 101 is formed on the connecting portion side with the joint 101, and an annular groove for arranging an O-ring is formed around the large diameter portion IB. A plurality of bolt holes IY for connection with IZ and the joint 101 are formed.

Further, on the side of the upstream body 1 facing the downstream body 2, an annular groove IW for arranging the O-ring 15 and a plurality of internal threads 18B (FIG. 5) are formed.

In this example, as shown in FIG. 1, a cylindrical hole IH is bored in the center of the upstream body 1, and a cylindrical collar 3 and a terminal collar are provided in the cylindrical hole IH. 4 is press-fitted. The inner walls of the collar 3 and the terminal collar 4 constitute a sensing passage 21 for detecting the amount of intake air.

The collar 3 and the terminal collar 4 are made of a material such as resin, ceramic, or metal.

The airflow upstream end of the collar 3 (hereinafter referred to as the tip), that is, the tip of the sensing passage 21, in this example, protrudes further upstream of the airflow than the tip of the intake passage 29, which will be described later. .

A plurality of intake passages IA are bored outside the collar 3 and the terminal collar 4 of the upstream body 1.

Inside the terminal collar 4, a hot wire type air flow sensor 7 and a temperature compensation sensor 8 are arranged. The lead wire of the sensor 7.8 is led out of the upstream body 1 through a terminal holder 5 attached to the upstream body 1 by a male thread 19D.

The terminal holder 5 is made of a material such as resin, ceramic, or metal.

An intake air amount detection circuit for detecting the amount of intake air using the air flow rate sensor 7 and temperature compensation sensor 8 is formed on a circuit board 11 fixed to the outer wall of the upstream body 1. The lead wire is connected to this circuit board 11.

In addition to the intake air amount detection circuit, the circuit board 11 is provided with a signal output from the detection circuit in order to inject fuel from the fuel injection valve according to the intake air amount detected by the detection circuit. A control circuit is formed which amplifies the signal and sets the valve opening time (duty ratio) of the fuel injection valve based on the amplified signal. Since the intake air amount detection circuit and the control circuit are well known, a description thereof will be omitted.

The circuit board 11 has a characteristic of blocking electrical disturbances.
It is covered with a resin cover 13. The cover 13 is attached to the upstream body 1 with a male screw 19C, with a gasket 14 disposed between the cover 13 and the upstream body 1.

Reference numeral 12 is a resistance element for power control.

At the end of the sensing passage 21 on the downstream side of the air flow (hereinafter referred to as the rear end), there is a downstream body 2 which will be described later.
A rectifier 6 attached to the central part of the rectifier 6 is disposed.

The rectifier 6 may be formed integrally with the downstream body 2.

Next, in FIG. 1.4.5, the downstream body 2
On the side of the connecting part with the joint 102, there is a large diameter part 2B having an inner diameter that is almost the same as the inner diameter of the joint 102.
An annular groove 2Z for arranging an O-ring is formed around the large diameter portion 2B.

A plurality of bolt holes 2Y are formed for connection to the joint 102.

As described above, the downstream body 2 has a male thread 19A corresponding to the rear end of the sensing passage 21.
The rectifier 6 is fixed by.

The rectifier 6 constitutes the bottom of the sensing passage 21 .

In this example, the rectifier 6 is formed such that its central portion protrudes toward the upstream side of the airflow, but the present invention is not limited to this.
It may be formed in a flat plate shape or with a recessed portion on the downstream side of the air flow.

Further, a plurality of intake passages 2A are formed in the downstream body 2 around the rectifier 6 so as to correspond to the intake passages IA formed in the upstream body 1.

The downstream body 2 is fixed to the upstream body 1 with an O-ring 15 disposed in the annular groove IW of the upstream body 1. The fixation is performed by screwing the male thread 19B (FIG. 4) into the female thread 18B (FIG. 5) formed on the upstream body 1.

The intake passages IA and the intake passages 29 formed by the two intake passages are formed to be parallel to the sensing passage 21.

Further, in this embodiment, the intake passage 29 is formed to have a venturi shape, but the present invention is not limited to this, and for example, the intake passage 29 may be formed to have a simple cylindrical shape. may be done.

The upstream body 1 and the terminal collar 4, as well as the downstream body 2, have the sensing passage 2 when they are joined, as shown in FIG. 1.3.5.
1 communicates with the side wall of each intake passage 29, a communication passage 22 is formed. In this embodiment, the communication path 22 is formed along the bottom of the sensing path 21, that is, along the side surface of the rectifier 6.

In the first embodiment of the present invention having the above configuration, when the internal combustion engine equipped with the air flow meter 100 starts operating, air is sucked from the air cleaner disposed at the tip of the intake pipe of the internal combustion engine. , passes through the air flow meter 100 in the direction of arrow A (FIGS. 1 and 2). As mentioned above, since the sensing passage 21 is open to the side wall of each intake passage 29, the air flowing into the sensing passage 21 is
The air is sucked from the communication passage 22 into each of the intake passages 29 .

Here, as described above, each intake passage 29 has the same shape, and as shown in FIGS. 3 to 5, the distances between adjacent ones are equal, and each The sensing passages 21 are formed so that the distances from the center thereof are equal. Moreover, the shape of each of the communication passages 22 is also the same.

As a result, the air flowing into the sensing passage 21 uniformly flows out from the center of the rear end of the sensing passage 21 in a radial manner, so that the air flow passing through the sensing passage 21 is directed in the direction of passage. Laminar flow can be achieved reliably without much movement. therefore,
The amount of intake air can be accurately detected by the air flow rate sensor 7 and the temperature compensation sensor 8.

Here, the optimal shape, length, etc. of the sensing passage 21 in order to make the air flow passing through the sensing passage 21 a laminar flow state are determined by the displacement of the internal combustion engine to which the air flow meter is applied, the cylinder cylinder, etc. Although it is necessary to set the color according to various factors such as the number of intake pipes, the shape of the intake pipe, the length of the intake pipe, etc., as in this embodiment, the collar 3 and terminal collar 4 constituting the sensing passage 21 are connected to the air flow meter. 100 body (in this example, upstream body 1) and a separate member,
Only the collar 3 and the terminal collar 4 need be formed according to each of the above factors, and common parts can be used for other parts such as the body except for the collar 3 and the terminal collar 4.

That is, for example, the collar 3 shown in FIG. 1 can be optimized depending on various factors such as the displacement of the internal combustion engine, the number of cylinders, the shape of the intake pipe, and the length of the intake pipe, as shown in FIG. By replacing the collar 3A with a collar 3A formed to have a suitable shape and length, the sensing passage 21 can be shaped to the optimal shape and length according to each of the above factors, even if the other parts except the collar 3A are shared. Can be set.

Note that, together with the collar 3, the terminal collar 4 may also be replaced.

As a result, the above-mentioned parts can be mass-produced regardless of the type of internal combustion engine or vehicle (hereinafter referred to as internal combustion engine, etc.), and the labor and time required to manufacture the air flow meter can be reduced.
And its production cost can be significantly reduced.

FIG. 7 is a sectional view of a second embodiment of the present invention showing a modification of the collar, and is a view similar to FIG. 1. In FIG. 7, the same reference numerals as in FIG. 1 refer to the same or equivalent parts, so the explanation thereof will be omitted.

In FIG. 7, a cylindrical hole IH and a female thread 201H are coaxially bored in the center of the upstream body 201. A terminal collar 4 is press-fitted into the cylindrical hole IH, and a collar 203 having a thread formed on its outer periphery is screwed into the female thread 201H.

Even in the air flow meter 200 having the above configuration, the collar 203 and/or the terminal collar 4 can be replaced depending on the type of internal combustion engine.

FIG. 8 is a sectional view of the third embodiment of the present invention, and the first,
This is a diagram similar to Figure 7. In FIG. 8, the same reference numerals as in FIGS. 1 and 7 refer to the same or equivalent parts, so the explanation thereof will be omitted.

In FIG. 8, a terminal collar constituting the air flow downstream side (hereinafter referred to as the rear end) of the sensing passage 21 is formed integrally with the terminal holder 305. That is, in this example, only the collar 3 forming the tip of the sensing passage 21 is replaceable.

Generally, the sensor should be placed on the rear end side of the sensing passage 21, so in order to make the air flow passing through the sensing passage 21 into a laminar state so that it hits the sensor, It is sufficient to change only the shape, length, etc. of the tip end of the sensing passage 21.

Therefore, in the present invention, at least the tip end side of the sensing passage may be formed separately from the body of the air flow meter.

FIG. 9 is a cross-sectional view of the fourth embodiment of the present invention.
7. This is a diagram similar to Figure 8. In Figure 9, the first
．． The same reference numerals as in Figure 7.8 represent the same or equivalent parts, so their explanation will be omitted.

In the description of each of the above embodiments, the air flow meter is of the type in which the collar is attached to the upstream body by press fitting, as shown in FIG. Air flowmeters with a collar attached to the upstream body have lengths and sizes depending on the type of internal combustion engine, etc.
The collar having a shape has been described as being constructed by attaching it to the body. In these cases, in order to prevent a recess from forming between the collar and the terminal collar, the press-fit depth or screw engagement depth is set to be the same even if the length of the collar is different. Ru.

On the other hand, in the air flow meter 400 shown in FIG. 9, the shapes of the collar 3 and the terminal collar 4,
The length is set to be the same regardless of the type of internal combustion engine, etc., and the length is set between the collar 3 and the terminal collar 4, which are press-fitted into the cylindrical hole IH, depending on the type of internal combustion engine, etc. It is configured to arrange an intermediate member 430 with a set height. That is, in the air flow meter 400 shown in this fourth embodiment, the press-fitting depth of the collar 3 is set to differ depending on the type of internal combustion engine.

In this air flow meter 400, the sensing passage 21
Although only the length of the collar 3 can be changed, rather than manufacturing collars 3 of various lengths whose ends are formed in a bell mouth shape, the intermediate member 430, which is simply formed in a ring shape, can be manufactured in various lengths. It is easier to manufacture the air flow meter 400, and it becomes easier to manufacture the air flow meter 400. As a result, the air flow meter 400 can be manufactured at low cost.

In this example as well, as in the first to third embodiments, the airflow passing through the sensing passage 21 can be reliably brought into a laminar flow state depending on the type of internal combustion engine or the like.

Note that two or more intermediate members may be arranged between the collar 3 and the terminal collar 4.

Now, in the above description, the communication path 22 was described as being formed along the surface of the rectifier 6 whose central part was formed to protrude toward the upstream side of the air flow, but in the present invention is not particularly limited to this.

In other words, the communication passage 22 sucks the air passing through the sensing passage 21 with the flow of air passing through the intake passage 29, and brings the air passing through the sensing passage 21 into a laminar flow state. The optimal shape for this depends on various factors such as the shape, size, and length of the sensing passage 21 or the intake passage 29, the displacement of the internal combustion engine, the number of cylinders, the shape of the intake pipe, and the length of the intake pipe. Change. Therefore, it is desirable that the communication path 22 be formed in a shape that corresponds to each of the above factors.

Furthermore, two or more communicating passages 22 may be provided for one intake passage 29.

Further, around the sensing passage 21, an intake passage 29 having a circular shape and the same size as seen from the air flow passage direction is provided.
, so that the distances between adjacent objects are equal,
Although four are formed so that the distances from the center of the sensing passage 21 are equal, the present invention is not limited to this.

In other words, the intake passage 29 is for making the air flow in the sensing passage 21 a laminar flow by suctioning the air flow in the sensing passage 21 through the communication passage, and the optimum The shape and number vary depending on various factors such as the cross-sectional shape, size, and length of the sensing passage 21 or the communication passage 22, the displacement of the internal combustion engine, the number of cylinders, the shape of the intake pipe, and the length of the intake pipe.

Therefore, it is desirable that the shape and number of the intake passages 29 be modified depending on the various factors described above.

Furthermore, although it has been described that the intake passage is arranged in multiple stages around the sensing passage 21 and one communication passage is formed in each of the stages, the intake passage surrounds the sensing passage 21.
That is, only one C-shaped intake passage may be provided, and a plurality of communication passages may be formed in the intake passage, or one C-shaped communication passage may be formed along the intake passage.

Furthermore, when the intake passage has a venturi shape, the intake passage is formed so that the communication passage opens at the narrowest part of the venturi in FIG. The invention is not particularly limited to this, but the communication passage may be formed to open at a position shifted upstream or downstream of the air flow from the narrowest part of the venturi.

Furthermore, the air flow upstream end of the sensing passage 21 (
The tip part) is the first part. 7. 8. In FIG. 9, it is drawn to protrude beyond the airflow upstream end (tip) of the intake passage 29, and in FIG. 6, it is drawn to be flush with the tip of the intake passage 29. However, the present invention is not particularly limited to this, and may be formed so as to be retreated from the tip of the intake passage 29 toward the downstream side of the air flow.

Furthermore, it goes without saying that the shape of the inner wall of the sensing passage may be set to any shape depending on various factors such as the number of cylinders of the internal combustion engine and the length of the intake pipe.

(Effects of the Invention) As is clear from the above description, according to the present invention, the following effects are achieved.

(1) At least the part constituting the tip of the sensing passage in which the sensor is disposed is formed separately from the body of the air flow meter, so that the part can be used for an internal combustion engine or an engine equipped with an internal combustion engine. The shape and/or size of the sensor can be changed depending on the type of vehicle used, so that the sensor can be exposed to air in a laminar flow state.

Therefore, the parts of the air flow meter other than the above-mentioned parts can be shared regardless of the type of internal combustion engine or vehicle, and can be mass-produced. As a result, the air flow meter can be manufactured efficiently and at low cost.

(2) An intake passage is arranged around the sensing passage in which the sensor is disposed, and a communication passage is provided so that the side surface of the intake passage communicates with the sensing passage. Due to the passing airflow, air flowing into the sensing passage is radially drawn from the bottom side thereof. As a result, the airflow passing through the sensing passage can be reliably brought into a laminar flow state without moving much in the passage direction.

Therefore, the intake air amount can be accurately measured by the sensor, and the air flow meter can be made small and lightweight.

(3) Furthermore, since the sensing passage communicates with the side surface of the intake passage, in other words, since the sensing passage has a bottom, even if a backfire occurs, the sensor disposed in the sensing passage is less exposed to blast waves.

As a result, the sensor life is less likely to be shortened or deteriorated due to backfire.

Furthermore, since the blast wave caused by the backfire is less likely to be measured as the amount of intake air, the amount of intake air can always be accurately measured aIj.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of FIG. 3 taken along line B-B. FIG. 2 is a side view of the first embodiment of the invention. FIG. 3 is a front view of the first embodiment of the present invention when FIG. 2 is viewed from the upstream side of the air flow. FIG. 4 is a rear view of the first embodiment of the present invention when FIG. 2 is viewed from the downstream side of the air flow. FIG. 5 is a sectional view of FIG. 1 taken along line CC. FIG. 6 is a diagram showing a modification of the collar shown in FIG. 1. FIG. 7 is a sectional view of a second embodiment of the invention. FIG. 8 is a sectional view of a third embodiment of the present invention. FIG. 9 is a sectional view of a fourth embodiment of the present invention. 1.201... Upstream body, IA, 2A, 29...
・Intake passage, IH...cylindrical hole, 2...downstream body, 3.3A, 203...collar, 4...terminal collar, 5,305...terminal holder, 6...
Rectifier, 7... Air flow rate sensor, 8... Temperature compensation sensor, 11... Circuit board, 21... Sensing passage, 22... Communication passage, 100, 200, 300° 400
...Air flow meter, 201H...Female thread, 430...
・Intermediate parts agent Patent attorney Michito Hiraki and 1 other person Figure 3 IB IT Figure 6 Figure 7

Claims (6)

[Claims] (1) An air flow meter installed in an intake pipe of an internal combustion engine to measure intake air flow rate, comprising a sensing passage arranged approximately on the central axis of the intake pipe, and surrounding the sensing passage. a flowmeter body having at least one intake passage arranged in parallel with the sensing passage, and a hot wire sensor arranged in the sensing passage; at least the tip side of the sensing passage; An air flow meter characterized in that it is formed of a separate member from the flow meter main body. (2) The air flow meter according to claim 1, further comprising a communication passage communicating the sensing passage and the side surface of the intake passage. (3) The air flow meter according to claim 1 or 2, wherein the sensing passage has a bottom on the downstream side of the air flow. (4) At least the tip end side of the sensing passage,
The air flow meter according to any one of claims 1 to 3, characterized in that the air flow meter is divided into a plurality of parts. (5) At least the tip end side of the sensing passage,
The air flow meter according to any one of claims 1 to 4, wherein the air flow meter is attached to the flow meter main body by press-fitting. (6) At least the tip end side of the sensing passage,
The air flow meter according to any one of claims 1 to 4, wherein the air flow meter is attached to the flow meter main body by screwing.