JPH02153237A - Hot-wire type air flowmeter and internal combustion engine using same - Google Patents

Abstract

PURPOSE:To improve the measurement accuracy by forming a sub flow passage with two flow passages formed in the axial direction and the radial direction of the main flow passage in a device for measuring the intake quantity by providing the hot-wire element in the sub flow passage provided in the main flow passage forming an intake passage. CONSTITUTION:A projecting part 2 is integrally formed with a body 1 in the cylindrical main flow passage 3 in the body 1 forming an intake passage of an internal combustion engine. A sub flow passage 4 in parallel with the main flow passage 3 and having the entrance opening at the central part of the main flow passage 3 is provided at the tip of the projecting part 2. A hole passing through from the outside of the body 1 is formed in the projecting part 2, and the mold part 13 of a supporting member 11 of the hot-wire element 10 and the temperature compensation element 12 connected to a circuit unit 14 is housed in the hole. A bent sub flow passage 5 having the short length in the axial direction is formed in the downstream of the sub flow passage 4 with walls 2a-2c of the projecting part 2 and a cover 6, and the downstream side of the bent sub flow passage 5 is combined with the main stream through the exits 5a, 5b provided in right and left.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hot wire air flow meter, and is particularly suitable for configuring the intake system of an automobile engine and detecting and controlling the amount of intake air therein. The present invention relates to a hot wire air flow meter suitable for internal combustion engines.

[Conventional technology]

The passage configuration of a conventional hot-wire air flow meter for internal combustion engines is disclosed in Japanese Utility Model Application No. 58-135127. As disclosed in Japanese Patent Application Laid-Open No. 60-185118, a sub-flow path is formed in the suction pipe, and a hot-wire element is placed in this sub-flow path, and the heat-wire element is protected against engine blowback and backfire.9 Engine pulsations In order to prevent abnormal output of the hot wire element due to this, there are some devices that provide an obstacle downstream of the hot wire element or a complicated curved flow path that is long in the axial direction. In these devices, since the sub-flow path portion including the hot wire element is exposed to the mainstream, output errors due to temperature rise in the flow meter body are also small. However, these require a long axial dimension due to their construction, have a large number of parts, and are difficult to install, so they have drawbacks in terms of miniaturization and cost reduction.

Also, JP-A-57-23818, 57-11392
Some models, such as No. 6, have a hot wire air flow meter and a throttle valve device placed close together in an integrated body. In JP-A No. 57-23818, the sub-channel in which the hot-wire element is arranged is made of a straight pipe and is placed in the center of the main channel, which is the same as the two prior art techniques mentioned above, but it is difficult to prevent engine blowback and backfire. No consideration has been given to protecting the hot wire element against The downstream throttle valve is considered to have the function of a protective member when it is close to fully open, but there is a problem in that it hardly has that protective function when it is fully open or close to fully open.

Another disadvantage is that the flow in the sub-channel is affected by the movement of the throttle valve and is unstable. Japanese Unexamined Patent Publication No. 57-11
In No. 3926, the sub-channel in which the hot wire element is placed is arranged in an L-shape, with a channel parallel to the main flow and a channel perpendicular to it, inside the body wall that has a large heat capacity and does not have a relatively large heat transfer area. is formed. According to this configuration, it is possible to protect the hot wire element from engine blowback and backfire. However, due to the configuration of the sub-channel, the mainstream air cannot flow around the sub-channel wall, so the temperature of the sub-channel wall increases due to heat transfer from the engine and heat generated by the hot wire element itself, and There was a problem in that the internal air was heated and the difference between the temperature and the main flow air temperature became large, making it impossible to accurately measure the amount of intake air.

[Problem to be solved by the invention]

The above conventional technology does not take into account the shortening of the pipe length between the hot-wire air flow meter and the throttle valve device, resulting in an increase in pressure drop in the intake pipe and an increase in the weight and cost of the equipment. There was a problem. Furthermore, if we look at each individually, the temperature rise of the sub-channel wall around the element due to heat generation of the hot-wire element and heat intrusion from the outside, that is, the temperature of the air flowing through the sub-channel that hits the hot-wire element and temperature compensation element, and the actual temperature. Countermeasures against errors due to differences in intake air temperature, and even if the flow rate is equal to 1, the flow rate distribution between the main flow path and the sub flow path changes due to swirling or fluctuations in the incoming air or fluctuations in the flow downstream of the flowmeter. There were problems such as insufficient countermeasures, such as reducing flow turbulence in the sub-flow path, i.e. reducing output noise, protecting elements against backflow and pulsation caused by engine blowback or backfire, and countermeasures against output abnormalities. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a hot wire air flowmeter that is small and has high measurement accuracy.

Another object of the present invention is to provide an internal combustion engine that can optimally control the air-fuel ratio using the hot-wire air flow meter.

[Means to solve the problem]

The hot wire air flow meter according to the present invention includes a main flow path that constitutes an intake air passage of an internal combustion engine, a hot wire element that measures the intake air, and a subflow that has the hot wire element inside and is provided in the main flow path. The auxiliary flow path includes a flow path formed in the axial direction of the main flow path and a flow path formed in the radial direction of the main flow path.

The internal combustion engine according to the present invention includes the hot-wire air flow meter, a speed sensor that detects the rotational speed of the engine, a fuel injection device that injects fuel into intake air, and the intake air detected by the hot-wire air flow meter. and a control device that determines a corresponding fuel injection amount based on the rotational speed detected by the speed sensor and outputs a command to the fuel injection device to inject the determined fuel injection amount.

[Function] By arranging the hot wire element in a sub-channel independent from the main channel, the influence of turbulence in the main channel is reduced.In addition, in the sub-channel, which has a smaller diameter than the main channel, the element can be removed from the sub-channel entrance. By setting the distance to, for example, twice or more the diameter of the sub-channel, considerable rectification can be achieved, resulting in noise reduction. Furthermore, by providing a bent sub-flow path downstream of the element, the flow and pressure attenuate at the bent portion, thereby preventing damage to the hot wire element due to backflow and reducing the effects of pulsation.

In the present invention, the distance from the inlet of the sub-channel to the element is at least twice the diameter of the sub-channel, and the inlet of the sub-channel is constant from the inner wall of the body or the part connecting the inner wall of the body and the sub-channel. The throttle valve device is configured to protrude into the main flow channel with a distance of It can be directly connected, and problems caused by noise, pulsation, and backflow are also solved.

〔Example〕

An embodiment of the present invention is shown in FIGS. 1 and 2 below.

This will be explained with reference to FIG. The body 1 constitutes an intake pipe of an internal combustion engine. Intake air flows in from the left side of FIG. An internal combustion engine is connected downstream of the flow.

The body 1 forms a main channel 3 which is basically cylindrical.

A protrusion 2 integrally formed with the body 1 is provided in the main flow path 3. At the tip of this protrusion 2, there is a main flow path 3.
A sub-flow path 4 is provided parallel to the main flow path 3 and has an inlet opening in the center of the main flow path 3 . Further, this protruding portion 2 is provided with a hole that penetrates from the outside of the body 1, and the molded portion 13 of the support member 11 of the hot wire element 1o coupled to the circuit unit 14 is housed in this hole. A hot wire element 10 and a humidity compensating cord 12 are arranged in the sub-channel 4.

Further, the walls 2a, 2 of the protrusion 2 are provided downstream of the sub-flow path 4.
b, 2c and the cover 6 form a short bent sub-channel 5 in the axial direction.
is formed. A throttle valve 20 for controlling the total air flow rate is arranged downstream of the curved flow path. The throttle valve 20 is opened and closed by rotation of the valve drive shaft 21. Although not shown, there is a link outside the body that connects to the shaft. The link is normally activated by a cable that connects to the car's gas pedal. The cover 6 is screwed to the rear end of the protrusion 2 by bolts 7 and 8, and the throttle valve 20 and valve drive shaft 21 are attached to the front.

The opening 4a of the sub-channel 4 is provided at a distance of at least twice the inner diameter of the sub-channel 4 from the inner wall 1a of the body 1 and the wall 2d of the connecting portion of the protrusion 2 with the body 1, and , has a bell mouth shape.

The inner wall 1a of the body 1 and the outer wall 20 of the portion of the protrusion 2 forming the sub-channel 4 are formed in such a shape that the channel expands toward the upstream side. On the other hand, the inner wall 1b of the body 1 near where the throttle valve 20 is arranged is finished by machining to have the same diameter, but before being machined, it was formed into a conical shape with the flow path narrowing to the left side in Fig. 1. be done. As a result, casting is carried out using a middle mold which can be extracted from the left and right sides, with the surface near the protrusion wall 2a being the split position.

Open arrows indicate air flow. Most of the air flowing in from the left end in FIG. 1 flows through the main flow path 3, but a portion flows into the sub flow path 4. The sub-channel population 4a is the wall 1a, 2d
Since the flow is sufficiently ahead of the flow path, a flow with relatively little turbulence flows into the sub-channel 4.

Further, the bell mouth at the sub-channel inlet 4a takes in more air and increases the flow velocity near the inner wall 2f of the sub-channel 4, but due to the frictional action of the inner wall 2f of the sub-channel 4 up to the hot wire element, The flow in the sub-channel is sufficiently rectified, and immediately before the hot wire element 10, the flow has a uniform velocity distribution.

The ratio between the inlet diameter of the bell mouth and the diameter of the sub-channel 4 is 1.6 to 1.
2. Accordingly, the ratio between the length from the inlet to the hot wire element 10 and the diameter of the sub-channel is set to about 4 to 2.

However, it varies depending on the actual diameter of the sub-channel 4, and there is no one-to-one correspondence.

In the wake of the wire heating element 10, the flow is first bent upwards;
It flows through the bent sub-channel 5, then hits the inner wall of the body 1, curves left and right from the outlets 5a and 5b of the bent sub-channel, flows out, and merges with the main stream. Such a flow path configuration has the effect of attenuating backflow from the engine and preventing pulsation from propagating to the vicinity of the hot wire element 10.

According to this embodiment, a hot-wire air flowmeter for an internal combustion engine that is free from problems such as noise caused by flow turbulence, output instability due to the influence of pulsation, and damage to the hot-wire element due to engine blowback can be used with a short shaft. Consists of directional dimensions. That is, it has the advantage of being small, lightweight, and low cost. Furthermore, the flow meter body and throttle valve device body, which could only be manufactured separately in the past, can be constructed as an integrated body, reducing unnecessary pressure loss by shortening the engine suction pipe.

This has the effect of making it possible to reduce weight and cost.

A second embodiment of the present invention is shown in FIGS. 4 to 6.

The difference from the first embodiment shown in FIGS. 1 to 3 will be explained. The protrusion 42 is connected to the upper and lower walls of the body 41 (depending on the overall configuration, the left and right walls of the body 41, that is, the walls in the axial direction of the throttle valve drive shaft 21). Therefore, the bent sub-channel 45 downstream of the sub-channel 44 can be formed in both the up and down directions. Further, the outlet surface of the sub-flow path 44, that is, the rear end surface 42a of the protrusion 42 is made flat. This facilitates machining to reduce the surface roughness of this surface. Further, the sub-channel cover 46 is
The difference is that the second embodiment is not a simple plate like the first embodiment, but has a concave shape. The cover 46 is also attached to the rear end of the projection 42 with bolts 7,8. Since the sub-channel cover 46 is separate from the body, it is possible to finish the inner surface and the joint surface, so it is easy to finish the rear end surface 42 of the protruding part 42, so the inner surface of the bent sub-channel 45 can be finished. The overall surface roughness can be reduced, and the sealing of the joints can also be improved.

This is effective in preventing instability of the flow in the bent sub-channel and poor pressure sealing with the main channel, which may cause instability of the characteristics of the hot wire element 10.

Also in the first embodiment, as in the present embodiment, the protrusion 2
A similar effect can be obtained by making the rear end surface flat and the plate-like cover 6 having a concave shape.

The effect of this embodiment in which the bent sub-channels 45 are provided both in the vertical direction is that when pulsations are transmitted, there is an interference effect in front of the sub-channels 44, which is better against pulsations. However, since the passage resistance becomes smaller, it is desirable to make changes depending on the engine, such as reducing the area of the outlets 45a to 45d of the bent sub-flow path 45.

The effects of the configuration are similar to those of the first embodiment.

A third embodiment of the present invention is shown in FIGS. 7 and 8. A sub-flow path 74 parallel to the main flow path 73 is a protrusion 7 from the body 71.
2, but in a portion close to the inner wall of the body 71. A bent sub-flow path 75 downstream of the sub-flow path 74 is constituted by a rear end wall 72a of the protrusion 72 and a sub-flow path cover 76 attached to this wall 72a with bolts 7.

The rear end of the protruding portion 72 is formed up to the vicinity of the center of the main channel 73, and therefore, the flow in the bent sub-channel 75 first flows from the inner peripheral wall side of the body 71 to the main flow along the wall 72a. Flows toward the center of the passage 73, and then flows toward the lower curved passage outlet 5a.
Flows to the left or right or downstream.

On the downstream side of the curved flow path 75, the throttle valve 20 and the drive shirt 1-21 are arranged in an integrated body as in the first and second embodiments.

A feature of the third embodiment is that the length of the molded portion 83 integrated with the circuit unit 84 can be shortened, which is advantageous in terms of cost.

In addition, since the protrusion 72 can be made relatively small, the main flow path 7
Since the flow resistance of No. 3 can be reduced and the overhang mass is also small, this embodiment is advantageous in terms of vibration resistance compared to the first embodiment. However, the turbulence of the flow flowing into the sub-channel 74 becomes a little large, so in addition to increasing the bell mouth diameter accordingly, it is desirable to increase the distance from the sub-channel 74 to the hot wire element 10.

The basic effects of this embodiment are the same as those of the first embodiment.

A fourth embodiment of the present invention is shown in FIGS. 9-10.

The body 91 is composed of a single hot wire flowmeter, unlike the first to third embodiments.

The protrusion 92 is formed in substantially the same manner as in the first embodiment, with a sub-channel 94 at the tip and a part of the bent sub-channel 95 at the rear end, with the rear end surface 92a of the protrusion 92 being formed as a wall surface. has been done. The remaining part of the bent sub-flow path 95 is formed to protrude outside the main flow path 93 and to be embedded in the body 91 within a range of approximately 90 degrees both left and right from the upper side of the 10th EI. Therefore, the exits of the bent sub-channel 95 are located on both sides of FIG. The flow path surface on the downstream side of the bent sub-flow path 95 is formed by a gas furnace nut 96 . That is, a body of a throttle valve device independent of the flowmeter body 91 is connected to the flowmeter body 91 through bolt holes 98a to 98d, with the gasket interposed therebetween.

In this embodiment, since the length of the bent sub-flow path 95 can be made long, there is an advantage that it can be applied even to an engine with large pulsation.

A fifth embodiment of the present invention is shown in FIGS. 11 and 12. In this embodiment, reinforcing ribs 8 are added to the structure of the first embodiment. That is, a rib 8 is provided that is connected to the portion of the tip of the protruding portion 2 of the first embodiment that constitutes the sub-flow path 4 and the inner wall on the opposite side of the body 1 . This increases vibration resistance and reduces deformation of the protrusion 2 during casting.

Other effects are similar to those of the first embodiment.

A sixth embodiment of the present invention is shown in FIGS. 13, 14, and 15. A protrusion 132 from the body 131 includes ribs 137 and 138 and a sub-channel 134 formed perpendicularly to the mold part 13 connected to the circuit unit 14.
It consists of a cylindrical portion 132 that forms a cylindrical portion 132. Therefore, the molded part 13 of the circuit unit 14 passes through the hole in the wall of the body 131, crosses the main channel 133 by - degree, and then the protruding part 1
The hot wire element 10 is inserted into the sub-channel 134 by passing through the hole 32.
Place it inside. An O-ring 139 is provided at a portion of the mold portion 13 that fits into the hole of the protrusion 132. This 0
The ring 139 provides a sealing effect between the main flow path 133 and the sub flow path 134 . The bent sub-channel 135 is formed by the rear end surface of the protrusion 132 and the cover 136. cover 13
6 is provided with outlets 135a and 135b in two directions, up and down. The outlets 135a,b are configured such that the flow therein is rather directed back upstream. The reason for this is to compensate for the short length of the bent sub-channel.

The advantage of this embodiment is that the protrusions 137, 138, 132 are located in the direction of the throttle valve drive shaft 21, which originally becomes an obstacle to the main flow path 133.
It is possible to reduce the substantial flow resistance within. Also,
In this embodiment, the inlet portion 133a of the main flow path 133 is shaped like a bell mouth (19) to provide a rectifying effect in this portion.

Other effects are similar to those of the first embodiment.

Several embodiments have been described above, but in all embodiments, the cover member of the bent sub-channel is not necessarily bolted, but may be joined by adhesive, or may be connected to the rear of the protrusion. A configuration in which the contact surface of the end face is sealed with a sheet member is also considered.

A seventh embodiment of the present invention is shown in FIGS. 16-17. The basic configuration is the same as that of the sixth embodiment, but the difference is that flow paths 140a, 140b, etc. perpendicular to the main flow are formed in the cover 139.

According to this embodiment, since the cross-sectional area of each channel 140a, 140b, etc. can be made small, the axial dimension can be further reduced.

A fourth embodiment of the present invention is shown in FIGS. 18 to 19. The basic configuration is also the same as the sixth embodiment. In this embodiment, the flow path 142 perpendicular to the main stream is shaped like a disk.
That is, if the shape including the bypass flow path 134 is expressed, the difference is that it is formed into a mushroom shape. According to this embodiment, the axial dimension can be further reduced compared to the seventh embodiment.

A ninth embodiment of the present invention is shown in FIGS. 20 and 21. In this embodiment, a protrusion 210d that is integral with the body 210 that protrudes into the main flow channel 211 in which the sub flow channel 212 is provided is attached along the inner wall of the body. It is provided in a range of approximately 90'. Therefore, the sub-channel 212b is parallel to the main channel 211, and the sub-channel 21 is perpendicular to the main channel 211.
2c is formed in an arc shape, facing in the radial direction and also in the circumferential direction. The fluid resistance of this sub-flow passage 212C is substantially composed of the pipe shape resistance and frictional resistance of the right-angled bend and the angular cross-section elbow with a small curvature of about 90°.

Depending on how the cross-sectional area of the auxiliary flow path 212c is selected, the fluid resistance in this portion can be made equal to or greater than in the previous embodiments. The downstream wall of the sub flow path 212c with respect to the mainstream is formed of a plate-like cover 213, and the cover 213 is fixed to the protruding wall 210d with bolts 214a and 214b. In this embodiment, for some reason, for example, when an injector is arranged in front of the throttle valve 3 as in a single point injection system, it is necessary to form it in this way. In such a case,
For example, it is also conceivable to set the throttle valve axis at 45 degrees with respect to the direction in which the molded portion 2c holding the hot wire element faces.

This is considered effective in reducing the overall pressure loss at high flow rates. Other effects of this embodiment are almost the same as those of the first to third embodiments.

FIGS. 22 and 23 show examples of the disciple of the present invention.

This example is an example in which a sub-flow path having a relatively large fluid resistance is formed in a protruding portion having a relatively small volume. That is, a flow path 222c is formed in a donut shape parallel to the main flow and perpendicular to the sub flow path 222b in which the hot wire element is disposed. As a result, the protruding portion 220d of the body 220 that protrudes into the main flow path 221 becomes smaller than the sub flow path 222c. The downstream wall of the sub flow path 222c with respect to the mainstream is formed by a plate-shaped cover 223 fixed to the protrusion 220d with bolts 224 or the like.

The fluid resistance of the sub flow path 222c is a substantially right angle bend;
It consists of the pipe shape resistance of the elbow with a relatively large curvature of about 270°, and the friction resistance of the slightly long passage length, and unless the cross-sectional area of the sub-flow passage 222c is extremely increased, The fluid resistance, that is, the equivalent length of the conduit can be made larger than the sub-flow path. Therefore, the blowback is large,
It is also advantageous for internal combustion engines that are prone to backfires or have large intake pulsations. Other effects are basically the same as those of the first to third embodiments.

FIG. 24 shows an embodiment of the present invention.

In this embodiment, a sub-flow path having a relatively large fluid resistance is realized with a structure that does not increase the axial dimension. A main channel 24 is provided in a probe holder block 230 that is separate from the body 240 and is coupled to the circuit unit 2.
1, a sub-flow path 242c with an angular cross section facing in the radial direction at right angles to the sub-flow path 242b, a sub-flow path 242d facing upstream with respect to the main flow at right angles to the sub-flow path 242c, A sub-channel 24 oriented radially at right angles to the channel 242d.
All sub-channels 242 are formed at 2f.

The downstream wall of the sub flow path 242c with respect to the main stream is formed of a plate-like cover 243, and the cover 243 is connected to the bolt 244.
and is fixed to the holder block 230. In this embodiment, the length of the sub-channel 242b upstream of the hot wire element 2a is
Due to its short structure, the body is 240mm long to reduce noise.
A wire mesh body 245 is provided at the inlet opening. Further, a portion 2 of the wall of the holder block 230 on the upstream side with respect to the mainstream is extended further into the mainstream with respect to the outlet of the sub flow path 242e.
30a is provided so that the main flow does not shine directly at the outlet of the sub-channel 242e, the static pressure in this portion is stabilized, the flow within the sub-channel is stabilized, and noise is reduced.

In this example, the fluid resistance of the sub flow path 242 is composed of a pipe shape resistance element consisting of three right angle bends and a frictional resistance proportional to the long passage length, and is equivalent to the flow path in the example of the disciple. The length is increasing.

That is, the effect of this embodiment is strong against blowback, packfire, and suction pulsation, as in the example of the disciple. Further, by increasing the fluid resistance, particularly the shape resistance, of the sub-channel, it is possible to reduce the flow rate distribution ratio of the sub-channel to the main channel at high flow rates (high flow velocity range). This means that the flow velocity near the hot wire element can be lowered, which is advantageous in the long run against contamination due to dust adhesion.

In this embodiment, the body 24 is
Although it is formed separately from 0 and is detachable, the sub flow path 242c
, 242e are formed by drilling holes from outside the body, the holder block 230 can be formed integrally with the body.

FIG. 25 shows a second embodiment of the present invention.

In this embodiment, a sub-channel 252b parallel to the main channel 251 and a sub-channel 252c perpendicular to the sub-channel are provided in the protrusion 250d of the body 250, and an outlet opening 252d of the sub-channel is provided.
is formed to face the downstream direction of the mainstream, and is provided with a check valve 254. Since the outlet opening 252d is perpendicular to the streamline, if there is a backflow due to blowback or packfire if it is left as is, the exit surface of the sub flow path will be formed in a direction parallel to the streamline as in the previous embodiments. The backflow in the sub-channel becomes stronger than when it is closed. The check valve 254 prevents this. The thin plate member check valve 254 has a bolt 2
56 and backed up by a retainer 255 formed shorter than the check valve 254,
In order not to significantly impede the flow from 2d, it is normally placed on the retainer 255 side, ie, the normal oven, as shown in the figure. When there is a backflow, dynamic pressure is applied to the check valve 255, blocking the sub-flow path outlet 252d and preventing the backflow from entering the sub-flow path 252.

The fluid resistance of the sub flow path 252 in this embodiment is composed of the pipe shape resistance of the two right angle bends and the pipe friction resistance.
This is slightly smaller than the fluid resistance of the example. However, due to the function of the check valve, it has a structure that is more resistant to blowback and backfires. Further, as described in the example of the disciple, it is advantageous against long-term staining. Note that the sub flow path 252c of this embodiment
teeth.

The body 250 is formed into a circular cross section from the outside, and blind plugs 253 and 257 are added to form respective flow paths.

FIG. 26 shows a thirteenth embodiment of the present invention.

This embodiment is suitable for increasing the fluid resistance of the auxiliary flow path, which has been achieved in the embodiments of the apprentices, etc. Furthermore, a structure that is advantageous against long-term dust adhesion is achieved with a simpler structure.

That is, the hot wire element 2 of the sub-channel 262b parallel to the main flow of the sub-channel 262 formed in the protrusion 260d of the body 260
A throttle 262e is provided in the downstream part of the main flow, and the cross-sectional area (diameter) of the sub flow path 262c perpendicular to the main flow is changed to the sub flow path 26 parallel to the main flow.
It is smaller than 2b. Further, an enlarged portion 262f is provided in front of the outlet 262d of the sub-flow path 262c, and the outlet 262c is provided with an enlarged portion 262f.
The area of 2d is made equal to the area of the inlet 262a of the sub-flow path 262b.

By providing the throttle 262e and reducing the diameter of the flow path 262c, the fluid resistance of the sub flow path downstream of the hot wire element 2a, especially the fluid resistance against reverse flow, is reduced by adding resistance to the shape of the conduit due to contraction and expansion. can be increased. Therefore, the effect as originally stated is achieved.

In addition, by increasing the area of the outlet 262d and setting the cross-sectional area of the flow path 260d relatively large, the static pressure loss due to the dynamic pressure change from the inlet to the outlet can be reduced, and the flow path 260d can be
Since the pipe frictional resistance in the d portion can be reduced, there is also the effect that the flow distribution ratio in the low flow rate region can be relatively increased.

27-28 and 29 show another embodiment of the invention which substantially achieves the objects of the invention.

A sub-flow passage 272 opened at the center of the main flow passage 271 of the protrusion 270d of the body 270 is a sub-flow passage 272b parallel to the main flow.
It consists only of The surface of the protrusion 270d on the downstream side with respect to the mainstream is formed into a flat surface, and there is a check valve 2 therein which blocks the sub-flow passage outlet 272d when dynamic pressure of reverse flow is generated.
73 are provided. The check valve 273 is backed up by a retainer 274 having a shorter length than the check valve.

The retainer 274 is fixed to the protrusion 270d with bolts 275 and 276. The circuit unit 282 has a long molded part 282c, and a hot wire element 282a and a temperature compensation element 282 are arranged in a sub-flow path 272b.

Due to the action of the check valve already described, with this configuration, a hot wire flow meter for an internal combustion engine with good temperature characteristics and strong resistance to engine blowback and backfire can be realized with a short axial dimension. However, in this configuration, since the sub flow path 272 has a short passage length,
Problems include a small pulsation reduction effect and no flow velocity reduction effect in a high flow rate region.

FIG. 29 is a partially modified view of the embodiment shown in FIG.
A diaphragm 292e is provided.

This makes it possible to have a slight pulsation damping effect and to reduce the flow velocity in the sub flow path 292b in a high flow rate region.

Next, the internal combustion engine of the present invention will be explained using FIG. 30. FIG. 30 is a system embodiment of an internal combustion engine equipped with an electronically controlled fuel injection device to which the hot wire air flow meter for internal combustion engines of the present invention is applied.

Air is drawn into the cylinder 500 through an air filter 503, and a connecting pipe 504. A flow meter 1° is fed through the intake manifold 501. The flow meter 1 has a main flow path 21
A sub-channel 22 is formed that protrudes from the sub-channel 22.
Inside is a calorific element 2a formed integrally with the circuit unit 2.
and a temperature compensation element 2b are provided to detect the air flow velocity in this portion and obtain an output for the total intake air amount. A passageway of the flow meter 1 is provided with a throttle valve 3 for controlling the amount of intake air that is linked to the accelerator pedal of the vehicle. Furthermore, the flow meter 1 is equipped with an idle flow control (
NSC) valve 8 is provided.

On the other hand, fuel is injected into the intake manifold 501 from the fuel tank 505 by the pump 506 through the injector 507, and is supplied to the engine 500 together with air.

In the control unit 510, the output signal of the hot wire element circuit unit 2, the rotation angle signal of the throttle valve 3,
The output signal of the oxygen concentration sensor 508 installed in the exhaust manifold 507, the output signal of the engine rotational speed sensor 509, etc. are input, and the fuel injection amount, ISO valve opening degree, etc. are calculated.

Depending on this result, the injector 507. Controls ISC valve 8 etc. Further, the control unit 510 stores a table of fuel injection amount corresponding to the intake air amount and rotational speed, and the fuel injection amount can be immediately determined from the intake air amount from the hot wire element and the rotational speed from the speed sensor.
It controls the amount of fuel injected from the fuel injection device.

〔Effect of the invention〕

According to the present invention, the suction flow rate can be accurately measured without being affected by the flow in the main flow path.

[Brief Description of the Drawings] Fig. 1 is a sectional view showing one embodiment of the present invention, and Fig. 2 is a sectional view showing one embodiment of the present invention.
3 is a sectional view taken along the line nn in FIG. 1, FIG. 4 is a sectional view showing another embodiment of the present invention, and FIG. 5 is a sectional view taken along the ■ Line cross-sectional view, Figure 6 is IV-IV in Figure 4
A line sectional view, FIG. 7 is a sectional view showing another embodiment of the present invention,
8 is a view taken along the line ■-V in FIG. 7, FIG. 9 is a cross-sectional view showing another embodiment of the present invention, and FIG. 10 is a VI-VI diagram in FIG.
11 is a cross-sectional view showing another embodiment of the present invention, FIG. 12 is a cross-sectional view taken along the line ■-■ in FIG. 11, and FIG. 13 is a cross-sectional view showing another embodiment of the present invention. 14 is a sectional view taken along the line ■-■ in FIG. 13, FIG. 15 is a sectional view taken along the line IX--■ in FIG. 17 is a sectional view taken along the line X-X in FIG. 16, FIG. 18 is a sectional view showing a part of the sub-flow path in an embodiment of the present invention, and FIG.
The figure is a cross-sectional view taken along the line XI-X in FIG. 18, FIG. 20 is a cross-sectional view showing another embodiment of the present invention, and FIG.
FIG. 22 is a cross-sectional view showing another embodiment of the present invention, FIG. 2:3 is a cross-sectional view taken along I-1 in FIG. 24, FIGS. 26 and 27 are cross-sectional views showing other embodiments of the present invention, and FIG. 28 is a cross-sectional view showing another embodiment of the present invention.
29 is a diagram showing a partially modified embodiment of FIG. 27, and FIG. 30 shows the system of the electronically controlled fuel injection device of the present invention, with 1...body, 3...mainstream Road, 4.
... Sub-channel, 1o... Hot wire element.

Claims (1)

[Claims] 1. A main flow path that constitutes an intake air passage of an internal combustion engine, a hot wire element that measures the intake air, and a sub flow path that has the hot wire element inside and is provided in the main flow path. A hot-wire air flowmeter comprising: a hot-wire air flowmeter in which the sub-flow path includes a flow path formed in the axial direction of the main flow path and a flow path formed in the radial direction of the main flow path. 2. The hot wire air flowmeter according to claim 1, wherein the hot wire element is provided in a flow path formed in the axial direction of the main flow path. 3. The hot-wire air flow meter according to claim 1, wherein the sub-flow path formed in the axial direction of the main flow path is eccentrically provided with respect to the main flow path. 4. A hot-wire air system comprising a main flow path constituting an intake air passage of an internal combustion engine, a hot-wire element for measuring intake air, and a sub-flow path having the hot-wire element inside and provided in the main flow path. In the flowmeter, the sub-flow path is characterized by comprising a flow path with streamlines in the same direction as the streamlines of air flowing through the main flow path, and a flow path with streamlines in a direction perpendicular to the streamlines. Hot wire air flow meter. 5. The hot wire air flow meter according to claim 4, wherein the hot wire element is provided in a flow path having a streamline in the same direction as the streamline of the air flowing through the main flow path. 6. The hot wire air flowmeter according to claim 4, wherein the flow path having a streamline in the same direction as the streamline of the air flowing through the main flow path is provided eccentrically to the main flow path. 7. The hot-wire air flowmeter for an internal combustion engine according to claim 1 or 4, characterized in that a throttle is provided at the inlet of the auxiliary flow path to constrict the flow. 8. The hot wire air flow meter according to claim 1 or 4, wherein the member forming the main flow path and the member forming the sub flow path are integrated. 9. In claim 1 or 4, when the throttle valve provided on the downstream side of the secondary flow path with respect to the axial center of the main flow path opens, the throttle valve moves upstream. A hot wire air flowmeter characterized in that an inlet section is provided in a region located on the downstream side, and an outlet section is provided in a region located downstream. 10. An internal combustion engine comprising a main flow path constituting an intake air passage of the engine, a hot wire element for measuring intake air, and a sub flow path having the hot wire element inside and provided in the main flow path. In the hot-wire air flow meter, the sub-flow path includes a flow path formed in the axial direction of the main flow path and a flow path formed at an acute angle with respect to the flow path. Flowmeter. 11. The hot wire air flow meter according to claim 1, wherein the sub-flow passage formed in the axial direction of the main flow passage coincides with the axis of the main flow passage. 12. A hot-wire air flow meter for an internal combustion engine according to claim 9, wherein a plurality of sub-flow passages formed in the radial direction of the main flow passage are provided radially. 13. An internal combustion engine comprising a main flow path constituting an intake air passage of the engine, a hot wire element for measuring intake air, and a sub flow path having the hot wire element inside and provided in the main flow path. In the hot-wire air flowmeter, the main channel has a cylindrical structure, and the sub-channel includes a channel formed in the axial direction of the main channel and a channel formed in the circumferential direction of the main channel. A hot wire air flow meter for internal combustion engines featuring: 14. An internal combustion engine comprising a main flow path constituting an intake air passage of the engine, a hot wire element for measuring intake air, and a sub flow path having the hot wire element inside and provided within the three flow paths. In the hot-wire air flow meter, the sub-flow path forms a flow path formed in the axial direction of the main flow path, and a check valve is provided at the outlet portion to prevent backflow into the sub-flow path. Features of hot wire air flow meter. 15. A hot wire air flow meter according to any one of claims 1 to 14, a speed sensor that detects the rotational speed of an engine, a fuel injection device that injects fuel into intake air, and the hot wire air flow meter. determines a corresponding fuel injection amount based on the intake air amount detected by the sensor and the rotational speed detected by the speed sensor, and outputs a command to inject the determined fuel injection amount to the fuel injection device. An internal combustion engine characterized by comprising a control device.