JP4163080B2 - Engine intake system - Google Patents

Description

  The present invention relates to an intake device for an engine provided with a carburetor that circulates air cleaned by an air cleaner and generates an air-fuel mixture.

  Conventionally, in general-purpose engines and the like, an engine having a diaphragm type carburetor has been widely used. This type of diaphragm carburetor pressurizes the fuel in the fuel tank with the diaphragm pump of the diaphragm device that operates by the pulsation negative pressure of the engine, guides the fuel into the carburetor, and generates the air-fuel mixture in the intake passage in the carburetor. . In this case, the fuel flow rate characteristic (carburetor characteristic) supplied to the intake passage usually changes substantially linearly with a substantially constant slope according to the engine speed, as shown in FIG. 8, for example.

  By the way, in order to improve the exhaust gas characteristics in the high engine speed range and the drivability in the low engine speed range, the air-fuel ratio of the air-fuel mixture supplied to the engine is set to be relatively lean in the high engine speed range. It is desirable to set a relatively rich rotation range. In this case, the required fuel flow rate characteristic (engine required characteristic) is to suppress the fuel flow rate in the high rotation range while securing the fuel flow rate in the low rotation range as shown in FIG. 8, for example. In many cases, it is difficult to satisfy such a characteristic with a fuel flow rate characteristic only by a carburetor.

To cope with this, for example, as disclosed in Patent Document 1, a blow-back preventing plate facing the intake passage is provided on the upstream side of the carburetor, and the fuel in the high engine speed region is utilized by utilizing the suction resistance by the blow-back preventing plate. It is also possible to suppress the flow rate.
JP 2000-234571 A

  However, it is difficult to change the slope of the carburetor characteristics by simply providing a resistance upstream of the intake passage, and the fuel flow characteristics in the high and low engine speed ranges are the engine required characteristics at the same time. It was difficult to get close to.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an engine intake device capable of appropriately setting fuel flow characteristics in a wide range of engine revolutions as required.

The present invention provides an air cleaner that cleans the outside air upstream of a carburetor that generates an air-fuel mixture, and in an engine intake device in which the intake passage of the carburetor and the air cleaner communicate with each other, one end is opened and the other end is A guide member having a U-shaped groove closed in a bag shape is provided in the casing of the air cleaner so as to cover the inlet edge of the air intake passage, and is cleaned by the air cleaner and is then removed from the one end to the other end. A guide passage is formed in which the air flowing toward the air flow is changed by the other end portion to flow into the intake passage.

In this case, the guide passage preferably changes the flow direction of the air flowing from the one end portion toward the other end portion in a substantially right angle direction by the other end portion, and the middle portion of the U-shaped groove It is desirable to bend.

  According to the engine intake device of the present invention, it is possible to appropriately set the fuel flow rate characteristic in a wide range of engine revolutions as required.

  Embodiments of the present invention will be described below with reference to the drawings. The drawings relate to a first embodiment of the present invention, FIG. 1 is a top view showing the main part of the intake system of the engine, FIG. 2 is a view as viewed from the direction I in FIG. 1, and FIG. FIG. 4 is a characteristic view of the fuel flow rate by the carburetor when the guide passage is used.

  1 to 3, reference numeral 1 denotes a carburetor mounted on an intake system of a general-purpose engine. In this embodiment, the carburetor 1 is a diaphragm type carburetor. The carburetor 1 has an intake passage 3 (see FIG. 2) penetrating the carburetor body 2, and an upstream side of the intake passage 3 is communicated with an air cleaner 5 and a downstream side is communicated with an intake port of an engine (not shown).

  Inside the intake passage 3, a throttle valve and a choke valve (both not shown) for opening and closing the intake passage 3 are pivotally attached. Further, one ends of shaft portions 7a and 8a that respectively support the throttle valve and the choke valve pass through the carburetor body 2 and are exposed to the outside, and the throttle lever 7 and the choke lever 8 are connected to these ends, respectively. Yes.

  The carburetor body 2 contains a diaphragm that is operated by the pulsating negative pressure of the engine and a diaphragm pump that is linked to the diaphragm (none of which is shown), thereby allowing fuel from a fuel tank (not shown) to flow into the carburetor. A well-known diaphragm device that pumps into the interior of 1 is constructed.

  The air cleaner 5 includes a ring-shaped element 11 inside a housing 10 to constitute a main part. Note that the air cleaner 5 shown in FIGS. 1 to 3 shows a state in which a lid (not shown) is not crowned on the housing 10. In the casing 10, an intake port 12 communicating with the outside is opened on the outer peripheral side of the element 11, and a connection port 13 communicating with the intake path 3 of the carburetor 1 is opened on the inner peripheral side of the element 11. ing. In this embodiment, the housing 10 of the air cleaner 5 is directly attached directly upstream of the carburetor 1 via a pair of bolts 15, and the connection port 13 is in direct communication with the intake passage 3.

  In the housing 10, a guide member 20 is fixed at a position overlapping the connection port 13 on the inner peripheral side of the element 11. In other words, a guide member 20 is provided directly upstream of the intake passage 3 of the carburetor 1 via the housing 10 of the air cleaner 5. In this embodiment, the guide member 20 is formed of a cast member, and the guide member 20 is formed with a U-shaped groove 21 having one end 21a opened and the other end 21b closed in a bag shape. The guide member 20 is fastened together with the carburetor 1 together with the housing 10 via the bolt 15. Specifically, the U-shaped groove 21 side faces the connection port 13 and the other end 21 b is connected. It is fixed to the housing 10 while being positioned along the edge of the mouth 13. Then, the guide member 20 is fixed to the housing 10 in this manner, so that a guide passage 22 communicating with the intake passage 3 of the carburetor 1 immediately upstream is formed between the guide member 20 and the housing 10. Has been.

  The guide passage 22 is for guiding the air cleaned by the element 11 of the air cleaner 5 to the intake passage 3 while changing the flow direction thereof. Specifically, as shown by a two-dot chain line in FIG. 1, the guide passage 22 introduces air purified by the element 11 from an opening opened on the one end 21 a side of the U-shaped groove 21, The introduced air is circulated along a direction substantially orthogonal to the intake passage 3. The guide passage 22 changes the air flow direction to a substantially right angle immediately upstream of the intake passage 3 and then guides it to the intake passage 3. That is, the air flowing in the guide passage 22 is flowed into the intake passage 3 after the flow direction is changed to a substantially right angle by the other end 21b of the U-shaped groove 21 closed in a bag shape.

  By providing such a guide passage 22 immediately upstream of the intake passage 3, for example, as shown in FIG. 4, it is possible to change the fuel flow rate characteristic of the carburetor 1 with respect to the engine speed. That is, as shown by a solid line in FIG. 4, the fuel flow rate characteristic of the carburetor 1 when the guide passage 22 is provided immediately upstream of the intake passage 3 is the fuel flow rate characteristic of the carburetor 1 that does not have the guide passage immediately upstream (see FIG. 4), the inclination can be controlled small. This is because by changing the air flow direction immediately upstream of the intake passage 3, the flow velocity of air flowing into the intake passage 3 is accelerated by the intake inertia effect in the low engine speed range, while the high engine speed is increased. In the region, it is considered that the flow rate of the air flowing into the intake passage 3 is suppressed.

  As a result of further scrutiny of the fuel flow rate characteristics, the applicants of the present application greatly depended on the curve diameter immediately upstream of the intake passage 3 formed in the guide passage 22. It has been found that the slope of the fuel flow rate characteristic becomes smaller as the flow direction of the air flowing into the air changes abruptly immediately upstream of the intake passage 3. In view of such points, in the present embodiment, for example, by tuning the depth of the U-shaped groove 21 of the guide member 20 together with tuning of the carburetor 1 itself, the inclination of the fuel flow characteristic is changed, The fuel flow characteristic of the carburetor 1 is set to an appropriate value corresponding to the fuel flow characteristic required for the engine.

  According to such a configuration, the guide passage 22 that changes the flow direction of the air before flowing into the intake passage 3 of the carburetor 1 immediately upstream of the intake passage 3 by the guide member 20 connected to the upstream side of the carburetor 1. By changing the slope of the fuel flow rate characteristic of the carburetor 1 through tuning of the guide passage 22, the fuel flow rate characteristic in a wide range of rotation can be set appropriately according to engine requirements. By appropriately setting the fuel flow rate characteristic in this way, an air-fuel mixture having an appropriate air-fuel ratio can be supplied from the carburetor 1 to the engine, improving the drivability in the low engine speed range and increasing the engine speed. It is possible to achieve both improvement of exhaust gas characteristics in the region.

  At that time, the air cleaner 5 is connected directly upstream of the carburetor 1, and the guide member 20 is accommodated in the housing 10 of the air cleaner 5, so that the fuel flow characteristic of the carburetor 1 is not increased without increasing the intake system of the engine. Can be improved.

  Further, in the configuration in which the air cleaner 5 is connected directly upstream of the carburetor 1, a U-shaped groove 21 is formed in the guide member 20 by forming a guide passage 22 between the guide member 20 and the housing 10 of the air cleaner 5. The guide passage 22 can be formed with a simple configuration as described above, and further, tuning of the fuel flow rate characteristic can be simplified.

  Next, FIGS. 5 to 7 relate to a second embodiment of the present invention, FIG. 5 is a plan view of the main part of the intake system of the engine as viewed from the air cleaner side, and FIG. 6 is taken along the line III-III in FIG. Sectional drawing and FIG. 7 are explanatory drawings which show the modification of a guide member. In the present embodiment, the configuration of the guide member is mainly different from the first embodiment described above. In addition, about the structure similar to the above-mentioned 1st form, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIGS. 5 and 6, in this embodiment, the guide member 30 is formed of a sheet metal member. The guide member 30 has one end 31a opened and the other end 31c closed in a bag shape. A U-shaped groove 31 in which the midway part 31b is partially bent is formed. The guide member 30 is fastened to the carburetor 1 together with the housing 10 via the bolt 15. Specifically, the U-shaped groove 31 side faces the connection port 13, and the other end 31 c is connected. It is fixed to the housing 10 while being positioned along the edge of the mouth 13. Then, the guide member 30 is fixed to the housing 10 in this manner, so that a guide passage 32 communicating with the intake passage 3 of the carburetor 1 immediately upstream is formed between the guide member 30 and the housing 10. Has been.

  According to such a form, in addition to the effect obtained in the first form described above, the flow direction of the air before flowing into the intake passage 3 can be changed by partially bending the middle part 31b of the U-shaped groove 31. It can be continuously changed immediately upstream of the intake passage 3, and the tuning range using the guide member 30 can be expanded.

  At this time, by configuring the guide member 30 with a sheet metal member, the guide member can be configured at a low cost, and tuning in the bending direction with respect to the middle portion 31b of the U-shaped groove 31 can be easily performed.

  Here, in this embodiment, for example, as shown in FIG. 7, a sheet metal member, like the first embodiment described above, has one end 41 a opened and the other end 41 b closed in a bag shape. It is also possible to constitute the guide member 40 provided with the groove 41.

  In each of the above-described embodiments, the guide passage is formed between the U-shaped groove of the guide member and the housing of the air cleaner. However, the present invention is not limited to this, for example, the guide The member may be formed of a cast member, and a guide passage may be formed by opening different two-direction holes in the cast member and communicating with the inside of the cast member. Further, the guide member may be formed of a pipe material, Of course, the guide passage may be formed by bending.

  In each of the above-described embodiments, the guide passage is communicated with the carburetor intake passage immediately upstream of the air cleaner. However, the present invention is not limited to this, for example, outside the air cleaner. Of course, the guide passage formed by bending the pipe material or the like may be communicated directly upstream of the intake passage of the carburetor, and the upstream side of the guide passage may be communicated with the air cleaner via the intake conduit or the like.

The top view which shows the principal part of the intake system of an engine concerning a 1st form Same as above, as seen from the direction I in FIG. Same as above, cross-sectional view along the line II-II in FIG. Same as above, characteristic diagram of fuel flow rate by carburetor when using guide passage The top view which looked at the principal part of the engine intake system from the air cleaner side in connection with the second embodiment Same as above, sectional view taken along line III-III in FIG. As above, an explanatory view showing a modification of the guide member Characteristic diagram showing the fuel flow rate of the carburetor alone and the fuel flow rate required for the engine

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Carburetor 3 ... Intake path 5 ... Air cleaner 10 ... Housing 20 ... Guide member 22 ... Guide path 30 ... Guide member 32 ... Guide path 40 ... Guide member
Agent Patent Attorney Susumu Ito

Claims (3)

An air cleaner that cleans the outside air upstream of a carburetor that generates an air-fuel mixture, and an intake device for an engine in which the intake passage of the carburetor and the air cleaner communicate with each other,
  By providing a guide member having a U-shaped groove whose one end is opened and the other end is closed like a bag in the casing of the air cleaner so as to cover the inlet edge of the intake passage,
  An engine characterized in that a guide passage is formed in which air that has been cleaned by the air cleaner and flows from the one end portion toward the other end portion is changed by the other end portion to flow into the intake passage. Inhalation device. 2. The engine intake device according to claim 1, wherein the guide passage changes a flow direction of air flowing from the one end portion toward the other end portion in a substantially perpendicular direction by the other end portion. The engine intake device according to claim 1 or 2, wherein a middle portion of the U-shaped groove is bent.

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