JP2511992B2 - Intake structure of internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rectifying body structure of an air flow meter provided in a flow path, and particularly to an air flow suitable for highly accurately measuring an intake air flow rate of an internal combustion engine. The present invention relates to a rectifier structure of a meter.

[Conventional technology]

As an air flow meter for measuring the intake air flow rate of an internal combustion engine of an automobile, a small heating resistor is installed in a part of the passage section of the fluid, and the amount of heat transfer from this heating resistor to the surrounding air flow. A method of measuring the flow rate in order to obtain is often used. That is, the flow velocity v of a part of the passage cross section
Is a method for indirectly measuring the total flow rate Q by measuring Therefore, it is necessary to provide a rectifier on the upstream side of the air flow meter in the passage to rectify the flow deviation. Conventionally, a mesh or a lamina core has been used as the rectifier.
As a rectifying body structure of this kind, as described in JP-A-54-74779, a rectifying body having ventilation holes of equal distribution is known. Further, as described in Japanese Utility Model Application Laid-Open No. 54-143917, a viscous filter element is closely attached to the inner wall of the case of an automobile air cleaner to improve the dust retention performance.

[Problems to be solved by the invention]

In the air flow meter rectifying body structure having the above-described structure, as shown in FIGS. 11 and 12, the duct 3 having a large angle of bend is connected to the upstream side of the passage 2 in which the air flow meter 1 is attached. When the passage 2 and the duct 3 are eccentrically connected as shown in FIG. 13,
The flow velocity distribution in the passage cross section changes greatly. Especially when there is an air cleaner upstream of the air flow meter 1,
The air cleaner element gradually becomes dirty and the flow velocity distribution changes. For this reason, the measured flow rate of the air flow meter changes, the error with respect to the true flow rate value becomes large, and there is a problem that the engine control is significantly adversely affected when it is attached to an internal combustion engine of an automobile. That is, in the case where the rectifying body is like a wire mesh in which the ventilation holes are evenly distributed as in the conventional case, since the rectifying body has no thickness, the vector of the eccentric flow velocity on the upstream side is almost entirely in the rectifying body. It moves to the downstream side without change. When the flow velocity distribution is biased in this way, the main flow changes from p to q as shown in FIG. 12, and as the air cleaner element becomes more dirty, the flow velocity distribution becomes two points as shown in FIG. 6 (b). It changes from the chain line to the solid line. Therefore, the output of the air flow meter has changed over time.

In order to solve such a problem and make the flow velocity distribution uniform in the passage cross section, it is necessary to make the length of the rectifying body 3 to 10 times the diameter of the passage, and therefore the ventilation resistance is also 3 to 10 times. There was a drawback that the engine horsepower was reduced by 10 times. In this case, from the viewpoint of the structural design of the air flow meter and the layout of the engine room,
There is also a problem that it is difficult to secure a space for arranging such a large rectifying body. The problems disclosed in the above two publications do not solve this problem.

An object of the present invention is to provide a rectifying body structure of an air flow meter in which the velocity distribution of the flow in the passage hardly changes even if the state of the fluid flow on the upstream side changes.

[Means for solving problems]

The above object is to arrange an air passage and the air passage,
In an intake structure of an internal combustion engine comprising an air flow meter for measuring a flow rate of air, and a rectifying body structure provided on the upstream side of the air flow meter in the air passage, the rectifying body structure has a slow air flow. A rectifying body having a ventilation resistance of a portion smaller than a ventilation resistance of a portion where the air flow is fast, and two filtration layers excluding dust mixed with the flowing air are integrally formed, and the filtration layer existing downstream. Is more dense than that of the filtration layer present upstream.

[Action]

According to the above structure, the flow velocity distribution in the cross section of the passage is uniform, the dirt in the filtration layer progresses almost uniformly over the entire cross section of the passage, and the deviation in velocity is almost unchanged because the deviation is small.
Flow rate measurement accuracy can be maintained.

〔Example〕

Embodiments of a rectifying body structure of an air flow meter according to the present invention will be described below with reference to the drawings.

1 to 3 show a first embodiment of the present invention. In FIG. 1, an air flow meter 1 has a heating resistor (hereinafter referred to as HF) 4 and a temperature compensation resistor (hereinafter referred to as CF) 5 heated to 160 ° C. to 300 ° C.
It is arranged in the small bench lily 8 via a, 6b and 7a, 7b. The base of the small bench lily 8 is fixed to the inner wall of the duct 9, and the small bench lily 8 and the duct 9 are arranged concentrically, and the support pins 6a, 6b, 7a, 7b of the resistors 4, One end on the side opposite to the one end to which 5 is fixed is connected to an electronic circuit 10 made of a substrate on which a thick film integrated circuit is formed. A rectifying body 11 is fixed to the upstream side of the duct 9 by a spring 12, a duct 13 led from an air cleaner (not shown) is further provided upstream of the duct 9, and a duct 14 is provided downstream thereof. They are connected as shown by a two-dot chain line. The structure of the rectifying body 11 corresponds to the flow velocity distribution upstream of the air flow meter 1 and is determined by experimentally examining the ventilation resistance of each aperture, as shown in FIGS. 2 (A) to (E). The holes are formed. (A) is an example in which holes 11a ₁ of the same shape are formed in the flat plate 11a so as to be closer to the left side in the figure, and the upstream duct has a bend and can cope with the flow of fluid introduced from the left side. (B), (C), (D)
Is a case where a straight pipe duct with no bend in the upstream side is connected respectively, (B) is that the outer periphery to the densely formed pores 11b ₁ of the same shape the central portion to the crude in a plate 11b, (c) is A small diameter circular hole 11c ₁ is formed in the center of the flat plate 11c, and a larger diameter circular hole is formed at the outer circumference.
11C ₂ is formed with equal pitches, and (D) is an example in which a hole 11d ₁ is formed on the flat plate 11d in the thickness direction so that the central portion is longer and the outer circumference is shorter. In the rectifying body 11 shown in these (B) to (E), since the flow velocity in the central portion is higher than that in the peripheral portion, this is an example in which it can be smoothed.

Next, the operation and effect of the present embodiment will be described. According to the above structure, the average velocity range of the air passing through the air flow meter 1 at the urban traveling speed of 15 to 60 km / h,
For example, at 5 to 20 m / s, a uniform air flow velocity can be obtained in the cross section of the air passage as shown in FIG. 6 (d).

On the other hand, the air flow resistance of the rectifying body 11 according to the present embodiment is slightly larger as shown in FIG. 3 (2) as compared with the conventional mesh having the same distribution of the distribution density of the openings.
However, when holes of the same shape are formed in a flat plate with a constant distribution density to obtain a uniform flow, the length of the rectifying body becomes long and the ventilation resistance becomes considerably large as shown in Fig. 3 (3). growing. Therefore, the ventilation resistance (2) according to the present embodiment becomes 1/2 or less as compared with (3), and the engine horsepower is not reduced. Further, this rectifying body can be inexpensively formed by, for example, press punching of a steel plate or plastic injection molding. Further, the flow velocity distribution hardly changes within the range of approximately 1/3 of the passage cross section even if the flow velocity distribution on the upstream side of the air flow meter 1 changes in the range of average flow velocity 5 to 20 m / s in the passage of the air flow meter 1. Therefore, by arranging the heat-producing low antibody 4 in this range, the influence of the change in the flow velocity distribution due to the dirt of the air cleaner or the duct is reduced, and for the stable control of the engine, the highly accurate flow rate measurement value is obtained. Can be provided to the control system.

FIG. 4 shows a second embodiment of the present invention. In the figure, the same or equivalent parts as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. Upstream of the duct 9, a multilayer air cleaner element 15 integrated with the rectifying body is provided.
Are provided concentrically, and a suction port 16 is formed upstream thereof. A flexible pipe 17 for connecting to an intake pipe (not shown) of the engine is provided downstream of the duct 9.
Are connected and fixed by a clamp 18. The life of the multi-layered air cleaner element 15 depends on the condition that the amount of trapped coarse layer reaches a certain value and cannot be collected any more, or the amount of trapped dense layer increases rapidly, leading to clogging. As indicated, it is desirable to allow each layer to be used to reach such limits at the same time. The specific structure of the multilayer air cleaner element 15 designed in this way will be described below. When the dust is Kanto loam dust, for example, the initial ventilation resistance P ₁ is P ₁ = 20 mmAq, the ventilation resistance P ₂ determined to reach the end of life is 60 mmAq, and the dust collection amount G is G = 160 gr. If so, the structure of the multilayer element is such that the wire diameter of the long fiber such as glass or plastic of the coarse element 19 in the preceding stage is 20 μm to 40 μm, the density is ρ ₁ = 5 kg / m ³ , and the layer thickness is 20 to 50 mm. And Middle layer 20
The density ρ ₂ is ρ ₂ = 10 kg / m ³ , and the layer thickness is 20 to 50 mm, assuming that the same fibers as those in the previous stage are used. For the dense layer 21 in the final stage, the fibers used are almost the same as in the previous stage, and the density ρ ₃ is ρ ₃ = 15 kg / m ³ .

When the layers of the multilayer air cleaner element configured in this way reach the end of their lives, the former stage collects 80 gr of dust and increases the ventilation resistance by 5 mmAq. The middle stage collects 50gr and increases the ventilation resistance by 13mmAq. The dense layer collects 30gr and has a ventilation resistance of 22.
Increase mmAq.

The density ρ is the most important factor for the optimum design of these air cleaner elements in order to meet the target mileage of 50,000 km. As shown in Fig. 8, when the maximum collection efficiency of each filter is 80% or more,
The fiber diameter of the air filter is 20 to 40 μm, and the thickness of each layer
It has been confirmed that if the density ρ is 20 to 50 mm and the front, middle, and rear stages are distributed in a ratio of 1: 2: 3, the life is extended as in the improved form of the graph shown in FIG. If it is necessary to make the air cleaner smaller depending on the surrounding conditions, as shown in the example of FIG. 4, the uninformed cloths 22 and 23 with holes as shown in FIG. Can be arranged in a vertical arrangement in a staggered manner, the increase in pressure loss can be suppressed by the holes 24, and the collection effect due to inertial collision can be achieved. Of course, by changing the configuration of the air filter element and impregnating it with oil, it is possible to improve the collection efficiency and ensure the same life. Further, as a method for facilitating the replacement of the air cleaner, the shape of the air cleaner which can be replaced by one-touch by the clamp 25 as shown in FIG. 5 can be adopted. Further, the material of the fibers of the air filter may be synthetic fibers, polyurethane, vinyl, metal wool or the like.

On the other hand, the velocity distribution at the inlet of the air flow meter is obtained by combining an air cleaner and an air flow meter having such a multi-layer structure in which a rectifying layer as shown in FIG. Is even more stable. Even if dust clogs the air cleaner element with time, there is almost no change in the flow velocity distribution due to the fact that the entire volume of the element progresses substantially uniformly. Therefore, for example, when the hot-wire or hot-film type flow sensor 1 of the air flow meter is arranged in the central portion of the passage, near the side wall of the passage, or in the bypass passage. However, since the flow velocity distribution hardly changes, it does not affect the flow rate detection accuracy. In addition, even if the air cleaner element is replaced with a new one, the flow velocity distribution hardly changes. Therefore, the flow rate measurement accuracy can be kept high. The housing of the air flow meter and the housing of the air cleaner can be integrally molded with resin, and the cost can be reduced.

According to the second embodiment described above, the ventilation resistance is slightly increased, but it is possible to promote rectification and further homogenize the flow by buffering the flow by the filter medium. Therefore, the change over time can be reduced. In particular, as in the case of a car equipped with a multipoint fuel injection device, when the intake duct is as long as 0.5 m to 1.0 m in order to balance intake vibration between the cylinders of the engine, the air flow meter uses a rectifier. The highest design can be achieved by making it coaxial with the built-in air cleaner. In addition, by making the air flow meter and the inlet and outlet channels of the air cleaner coaxial, the flow velocity distribution becomes symmetrical with respect to the channels as shown in FIG. 6 (d) even if the air cleaner upstream has a non-uniform flow. It will be like. Therefore, the dirt on the air cleaner element progresses almost uniformly over the entire passage cross section, and there is little deviation, so the velocity distribution hardly changes, and the flow rate measurement accuracy is improved. Was improved.

Further, according to the present embodiment, as shown in FIG. 4 or FIG. 5, the air is purified by a filter medium provided at right angles along the axis of the flow, from the upstream layer to the particles with large dust and the intermediate particles. Since it is possible to separate and collect particles and fine particles having a size, it is possible to improve purification efficiency with a small volume.
For example, since the particle size distribution of dust in the Kanto loam is as shown in FIG. 7, the upstream layer 19 collects dust in the range of 15 μm to 100 μm, and the intermediate layer 20 captures dust in the range of 2 μm to 15 μm. Collected, the downstream layer 21 is fine 0.1 μm to 2 μm
It is possible to collect dust in the range of. Each layer of the filter medium that constitutes these air cleaner elements can be changed according to the particle size and shape of the dust, constituent materials, etc., which differ depending on the climate and climate of the region in which the vehicle runs, and the life of each layer can be made almost equal. It makes it possible to extend the overall life and support maintenance-free operation. In addition to making the density of the layered filter medium coarse, medium, and dense from the upstream side, the cross-sectional area of each layer is made large, medium, and small so that dust with different particle diameters between layers can be easily collected. Become. In addition, it is also possible to capture the dust by inserting the unsightly cloths 22 and 23 having holes in the upstream layer 19 so that the dust of relatively large particles is stuck to the unsightly cloth due to its inertia at a high flow velocity. Furthermore, by appropriately determining the thickness of the layered filter media 19, 20, 21 of each layer, the air flow is rectified, and the downstream flow can be made less susceptible to the upstream dusting. Here, assuming that the ventilation resistance of a single element of a conventional chrysanthemum-shaped air cleaner is expressed as shown in, for example, the line a in FIG. With the addition of 16 ventilation resistances, it becomes as shown by line b. On the other hand, in the axial flow type multi-layered air cleaner according to the present embodiment, the ventilation resistance between the single element and the air cleaner is almost the same because the difference between the suction port and the air cleaner diameter is relatively small.
It becomes as shown by the c line. The clogging caused by the dust collection of the conventional air cleaner has a high adhesion density in the vicinity of the suction port in the initial stage, and when the clogging reaches a stage, the clogging gradually progresses toward the outer periphery away from the suction port. Eventually the clogging spreads throughout the area. At this point, the ventilation resistance also becomes abnormally large, and as shown by the line d in FIG. 9, the engine performance is impaired. Therefore, the change in ventilation resistance over time is rapid as shown by the solid line in Fig. 10, and the life of the air cleaner becomes short. On the other hand, according to the air cleaner of the present embodiment, the captured dust is distributed almost evenly over the entire volume of the element, and the ventilation resistance gradually increases with time as shown by the alternate long and short dash line in FIG. Show a trend. Therefore, the life of the element is extended.

〔The invention's effect〕

As described above, according to the present invention, the rectifier provided upstream of the air flow meter in the fluid passage is approximately proportional to the flow velocity of the fluid in each part of the passage cross section on the upstream side near the rectifier. Since the ventilation resistances are provided at positions that match each other, it is possible to rectify the upstream non-uniform flow and make the flow velocity distribution in the flow sensor arrangement portion of the air flow meter uniform.
It is possible to prevent the influence of the change in the flow velocity distribution due to dirt on the upstream side, for example, the air cleaner element, from affecting the flow rate sensor portion, and to improve the flow rate measurement accuracy of the air flow meter.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an air flow meter in which a rectifying body according to the present invention is incorporated, FIG. 2 is a plan view showing the rectifying body of FIG. 1, and FIG. 3 is a comparison of ventilation resistance of the rectifying body. The graphs shown in FIGS. 4 and 5 are longitudinal sectional views showing another embodiment of the present invention, FIG. 6 is an explanatory view showing the flow velocity distribution at the inlet portion of the air flow meter, and FIG. 7 is a graph showing dust of Kanto loam. Graph showing the combination of particle size distribution and each layer of the axial flow type air cleaner, No. 8
FIG. 9 is a graph showing the collection efficiency of the multilayer filter medium, FIG. 9 is a graph showing the relationship between the air flow rate and the pressure loss of the air cleaner, and FIG.
FIG. 10 is a graph showing the relationship between the distance traveled by the automobile and the pressure loss of the air cleaner, FIGS. 11 and 13 are assembly structure diagrams each combining a conventional air cleaner and an air flow meter, and FIG. 12 is a diagram of FIG. FIG. 6 is a cross-sectional view showing the progress of clogging by dust in the air cleaner. 1 ... Air flow meter, 9 ... Duct (passage), 11 ...
… Rectifier, 19,20,21 …… Filter material, 22,23 …… Insane cloth.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sadane Ueno 2520 Takaba, Katsuta City, Ibaraki Pref., Sawa Plant, Hitachi, Ltd. (72) Nobuyoshi Otake 415 Sakuya, Yuuki, Ibaraki Inside the Yuki Factory (72) Inventor Masaaki Watanabe 415 Sakunotani, Yuki City, Ibaraki Japan Inorganic Yuki Factory

Claims (3)

(57) [Claims] 1. An internal combustion engine comprising an air passage, an air flow meter disposed in the air passage for measuring a flow rate of air, and a rectifying body structure provided upstream of the air flow meter in the air passage. In the intake structure, the rectifying body structure includes a rectifying body having a ventilation resistance at a portion where the air flow is slower than a ventilation resistance at a portion where the air flow is fast, and two filtration layers excluding dust mixed in the flowing air. The intake structure of an internal-combustion engine, characterized in that the mesh size of the filter layer located downstream is higher than the mesh size of the filter layer located upstream. " 2. The intake structure for an internal combustion engine according to claim 1, wherein the plurality of filtration layers integrated with the rectifying body are formed of nonwoven fabrics having different opening densities. 3. The internal combustion engine according to claim 1, wherein the plurality of filtration layers integrated with the rectifying body are formed of a combination of a glass mat and an unknowing cloth mat. Intake structure.