JP2021067189A - Intake device for engine - Google Patents

Abstract

To provide an intake device for an engine that can increase output in a wide engine rotation range.SOLUTION: An intake device is provided in an engine E with three or more cylinders. The intake device includes: an air cleaner 25 stored with air to be supplied to the engine E; and a funnel 36 having an upstream end 36a opened inside the air cleaner 25 and a downstream end 36b connected to an intake port 26a of the engine E. The funnel 36 is provided for each cylinder. Three or more kinds of shapes are provided for the funnel 36.SELECTED DRAWING: Figure 4

Description

The present invention relates to an intake device of a multi-cylinder engine including three or more cylinders.

In the multi-cylinder engine disclosed in Patent Document 1, an intake funnel that opens in an air cleaner is provided.

Japanese Unexamined Patent Publication No. 2017-186942

Even if the funnel is provided, it may be difficult to improve the output in a wide range of engine speed.

Therefore, an object of the present invention is to provide an engine intake device capable of improving output in a wide range of engine rotation ranges.

In order to achieve the above object, the intake device of the engine of the present invention is an intake device of an engine having three or more cylinders, and has an air tank in which air supplied to the engine is stored and an upstream end. It includes a funnel that opens in the air tank and has a downstream end connected to an intake port of the engine. The funnel is provided for each cylinder, and three or more types of funnel shapes are provided.

According to this configuration, as the output of the entire engine, it is possible to obtain a characteristic in which three or more types of engine characteristics having different output curves according to the engine speed are superimposed. As a result, it is possible to suppress a drop in output in the region before and after the engine speed at which the output peaks, as compared with the case where the funnel shape is the same. As a result, it is possible to improve the output in a wide range of engine rotation.

In the present invention, the air tank has a funnel installation wall on which the funnel is provided and a facing wall facing the funnel installation wall, and the facing wall is an intermediate portion of a central portion in the series direction in which the funnels are lined up. And two outer portions extending incline from the intermediate portion toward the outside in the series direction toward the funnel installation wall, and two outer sides of the three or more funnels on both sides in the series direction. At least a part of the funnel is provided in a portion of the funnel installation wall facing the outer portion of the facing wall, and the two outer funnels are formed so that the funnel is shorter than the inner funnel arranged inside the funnel. May be good. According to this configuration, the outer funnel is formed to be short, so that it can be prevented from interfering with the outer portion of the facing wall of the air tank. As a result, it is easy to make the engine characteristics of each cylinder different in the limited air tank space, and it is possible to easily improve the output in a wide range of engine rotation range.

When the funnels are arranged in series, the engine may have four or more cylinders and may be provided with a plurality of inner funnels having different lengths. According to this configuration, two or more types of relatively long inner funnels can be provided by changing the length of the inner funnel arranged in the area where the distance between the funnel installation wall and the facing wall is long. As a result, it is easy to adjust the characteristics of the engine in the low speed range, and it is easy to suppress a decrease in engine output in the low speed range of the engine.

When the funnels are arranged in series, the longest funnel may have a larger area of the upstream opening than the other funnels. According to this configuration, in a funnel having a large length, it is possible to suppress an increase in intake resistance due to the length of the intake passage.

When the funnels are arranged in series, the upstream opening of the longest funnel may be oriented away from the direction facing the air intake of the air tank. A funnel with a large length tends to have a louder intake sound than the remaining funnel. This configuration prevents the intake noise generated by the longest funnel from heading towards the air intake. As a result, it is possible to suppress the intake noise from leaking to the outside from the air intake, and it is possible to reduce the engine noise.

When the upstream opening of the longest funnel faces away from the air intake, the engine is mounted on the vehicle and a duct that takes in running air into the air tank connects to the air intake. Even if the duct is connected to the center line in the front-rear direction of the air tank from one side in the vehicle width direction toward the other, and the longest upstream opening of the funnel is opened in the other side in the vehicle width direction. Good. Due to the displacement of the duct in the vehicle width direction, the air pressure in the air tank tends to be biased. According to this configuration, the upstream opening of the longest funnel opens in a relatively high pressure region in the air tank, so that relatively high pressure air is taken into the longest funnel and the engine speed is low. It is possible to increase the engine torque in several ranges.

When the funnels are arranged in series, the shortest funnel in the height direction between the funnel installation wall and the facing wall is located between the shortest funnel and the longest funnel in the air tank in the series direction. An introduction port for guiding blow-by gas may be formed in the air tank at a position intermediate between the longest funnel and the air tank. According to this configuration, it is possible to prevent blow-by gas from flowing into one cylinder in a concentrated manner. As a result, the influence of blow-by gas per cylinder can be suppressed.

When the engine is mounted on a motorcycle and the funnels are arranged in the vehicle width direction, the shortest funnel may be arranged on the side opposite to the side stand in the vehicle width direction. According to this configuration, it is possible to prevent the liquid that has entered the air tank from flowing into the cylinder through the funnel.

When the funnels are arranged in series, the fuel in the cylinder corresponding to the outer funnel and the fuel in the cylinder corresponding to the inner funnel may explode alternately. According to this configuration, the short funnel and the long funnel alternately suck the intake air, so that it is easier to increase the intake amount in the long funnel compared to the case where the intake air of the two long funnels is continuous, and the engine speed is low. It is easy to improve the engine torque in the range.

According to the intake device of the engine of the present invention, it is possible to suppress a drop in output in a region before and after the engine speed at which the output peaks, as compared with the case where the funnel shape is the same. As a result, it is possible to improve the output in a wide range of engine rotation.

It is a side view which shows the front part of the motorcycle which mounted the engine which provided the intake device which concerns on 1st Embodiment of this invention. It is a top view which shows the front part of the motorcycle. It is a side view which shows the intake device. It is a vertical cross-sectional view which shows the intake device. It is a top view which shows the air cleaner of the intake device. It is a front perspective view which shows the inside of the air cleaner. It is a rear view of the air cleaner seen from the rear of the vehicle body. It is a performance curve of an engine equipped with the same intake device. It is a front perspective view which shows the inside of the air cleaner which concerns on the modification of the intake device.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side view showing the front part of a motorcycle which is a kind of saddle-type vehicle according to the first embodiment of the present invention. In the present specification, "right" and "left" mean "right" and "left" as seen by the driver in the vehicle. Further, "upstream" and "downstream" mean "upstream" and "downstream" in the flow direction of intake air.

The body frame FR of the motorcycle of the present embodiment has a main frame 1 forming the front half portion and a rear frame 2 forming the second half portion. The rear frame 2 is joined to the rear portion of the main frame 1. The main frame 1 extends from the head pipe 4 at the front end so as to be inclined downward toward the rear.

A front fork 16 is rotatably supported by a head pipe 4 at the front end of the main frame 1 via a steering shaft (not shown). The front wheel 18 is supported at the lower end of the front fork 16. The handle 20 is attached to the upper bracket 17 that supports the upper end of the front fork 16. A swing arm (not shown) is supported at the lower part of the rear end of the main frame 1, and a rear wheel (not shown) is supported by this swing arm. The engine E is supported in the lower center of the main frame 1. The rear wheels are driven by the engine E.

The engine E of the present embodiment is a water-cooled 4-cylinder 4-cycle engine in which the cylinders are arranged in the vehicle width direction W (FIG. 2). In the present embodiment, the first to fourth cylinders are arranged in order from the left in the vehicle width direction W, which is the series direction. However, the type of engine E is not limited to this. The engine E has a crankcase 22 that supports a crankshaft (not shown), a cylinder 24 that projects upward from the front portion of the crankcase 22, and a cylinder head 26 above the crankcase 22. An intake port 26a into which intake air is introduced is formed on the rear surface of the cylinder head 26. An exhaust port 26b from which exhaust gas is led out is formed on the front surface of the cylinder head 26. An exhaust pipe 28 is connected to the exhaust port 26b.

An air cleaner 25 is arranged above the cylinder head 26 of the engine E. The air cleaner 25 filters the air supplied to the engine E. Specifically, the air cleaner 25 has a cleaner case 34 shown in FIG. 4 and a cleaner element 35 arranged inside the cleaner case 34. Air is filtered as it passes through the cleaner element 35. In this way, the air cleaner 25 constitutes an air tank in which the air supplied to the engine E is stored. The fuel tank 40 is arranged above the air cleaner 25 in FIG. 1.

On the other hand, in the present embodiment, the cleaner inlet 25a is formed on the left side and the cleaner outlet 25b is formed on the rear side of the air cleaner 25 shown in FIG. 2 in the vehicle width direction. One cleaner outlet 25b is arranged for each cylinder, and a total of four cleaner outlets 25b are provided side by side in the vehicle width direction. The cleaner outlet 25b of the present embodiment is composed of a funnel 36 penetrating the bottom wall of the case of the air cleaner 25 shown in FIG. Details of the funnel 36 will be described later.

A throttle body 27 is connected between the cleaner outlet 25b and the intake port 26a of the engine E. That is, the rear portion of the air cleaner 25 is supported by the engine E via the throttle body 27. A throttle valve 27a is provided inside the throttle body 27. The throttle valve 27a adjusts the amount of intake air supplied to the engine E.

A drive mechanism 27b for the throttle valve 27a is provided at the front portion of the throttle body 27. The drive mechanism 27b includes, for example, a motor, a motor gear, and the like. The drive mechanism 27b projects obliquely upward from the front portion of the throttle body 27. A fuel injection device 27c is provided on the throttle body 27. The fuel injection device 27c injects fuel into the intake passage inside the throttle body 27. In the present embodiment, the throttle valve 27a is provided for each cylinder. The throttle valve 27a is controlled for all cylinders, for example, and the fuel injection device 27c is controlled for each cylinder, for example. However, the control method is not limited to this. For example, the fuel injection amount may be controlled in common for all cylinders.

The motorcycle of the present embodiment has a front cowl 30 shown in FIG. 1 and a pair of left and right side cowls 32. The front cowl 30 covers the front of the head pipe 4. The side cowl 32 is arranged behind the front cowl 30, and covers the front part of the vehicle body, specifically, the main frame 1 and the engine E from the outside. An air introduction port 50 opened forward is formed on the front surface of the front cowl 30. When the motorcycle travels, the traveling wind A is taken in as the intake air of the engine E from the air introduction port 50.

An intake duct 52 that communicates the air introduction port 50 and the air cleaner 25 is provided. The inlet 52a at the front end of the intake duct 52 shown in FIG. 2 is located on the vehicle width direction center line C1 and faces the air introduction port 50. The outlet 52b at the rear end of the intake duct 52 shown in FIG. 2 is connected to the cleaner inlet 25a on the front left side of the air cleaner 25. That is, the intake duct 52 takes in the traveling wind A from the air introduction port 50, passes the left side of the head pipe 4 in the vehicle width direction, and supplies the air cleaner 25. The intake duct 52 is curved so as to extend forward from one side (left side) in the vehicle width direction toward the other side (right side) with respect to the center line C2 in the front-rear direction of the air cleaner 25. A side stand 38 is provided on one side of the vehicle body in the vehicle width direction and is supported by the vehicle body frame FR.

As shown in FIG. 3, the cleaner case 34 has an upper case half body 34a and a lower case half body 34b divided into upper and lower halves, and both case halves 34a and 34b are connected by a plurality of bolts 54. There is. The mating surfaces 55 of the semifields 34a and 34b of both cases extend in the front-rear direction along the main frame 1. The cleaner inlet 25a is formed in the front portion of the lower case half body 34b.

The upper wall of the front half of the upper case semifield 34a has an inclined portion 56 that inclines upward toward the rear with respect to the mating surface 55. The upper wall of the latter half of the upper case half body 34a is composed of a curved portion 57 that smoothly bulges upward and smoothly curves downward at the rear portion.

As shown in FIG. 4, the cleaner element 35 is housed in the front portion of the cleaner case 34. In the cleaner case 34, the upstream side of the cleaner element 35 is the dirty chamber 33, and the downstream side is the clean chamber 37. The cleaner inlet 25a (FIG. 3) is provided below the cleaner element 35, and the inclined portion 56 is formed above the cleaner element 35. The cleaner outlet 25b is formed at the rear of the lower case half body 34b.

The front half of the bottom wall 58 of the cleaner case 34 extends rearwardly and upwardly along the upper surface of the cylinder head 26. The latter half of the bottom wall 58 extends downwardly with an inclination toward the rear. A recess 60 recessed upward is formed in the latter half of the bottom wall 58 of the cleaner case 34. A part of the drive mechanism 27b of the throttle body 27 is housed in the space formed by providing the recess 60.

Next, the flow of intake air of the motorcycle of the present embodiment will be described. When the motorcycle travels, the traveling wind A shown in FIG. 2 is introduced into the intake duct 52 from the air introduction port 50. At that time, the pressure of the traveling wind A rises due to the ram pressure. The air A introduced into the intake duct 52 is introduced into the air cleaner 25.

As shown in FIG. 4, the air A introduced into the air cleaner 25 is filtered by the cleaner element 35 inside the air cleaner 25 to become clean air CA. The clean air CA is guided rearward by the inclined surface 56 of the cleaner case 34 in the clean chamber 37, and flows toward the rear cleaner outlet 25b. The clean air CA is supplied to the engine E from the funnel 36 mounted on the cleaner outlet 25b via the throttle body 27.

Next, the funnel 36 of the present embodiment will be described. The funnel 36 is made of a pipe member having a circular cross-sectional shape, and one funnel 36 is provided for each cylinder. The upstream end 36a of the funnel 36 opens into the clean chamber 37 inside the air cleaner 25, and the downstream end 36b is connected to the intake port 26a of the engine E via the throttle body 27.

Three or more types of funnel 36 shapes are provided. Here, "providing three or more types of funnel 36s" means that there are three or more types of funnels 36 having different shapes. In this embodiment, four types of funnel 36 shapes are provided. That is, in the present embodiment, the shapes of the four funnels 36 are all different. In the following description, the funnel 36 corresponding to the leftmost cylinder No. 1 is referred to as the first funnel 36-1. The funnel 36 corresponding to the second cylinder to the right of the first cylinder is referred to as the second funnel 36-2. The funnel 36 corresponding to the third cylinder to the right of the second cylinder is referred to as the third funnel 36-3. The funnel 36 corresponding to the 4th cylinder on the far right is referred to as the 4th funnel 36-4.

Here, "different shapes" may mean, for example, different lengths of funnels 36, different diameters of funnels 36, or both. That is, the shape may be changed so as to cause a change in the engine characteristics of each cylinder. In this embodiment, the lengths of the four funnels 36 are all different. Here, the "length of the funnel 36" means the length of the axis of the funnel 36. That is, when the funnel 36 is a straight pipe, the "length of the funnel 36" corresponds to the length of the straight pipe. For example, the length of the funnel 36 may be the length inside the air cleaner 25. The larger the length or volume of the funnel 36, the higher the intake inertia, and the easier it is to obtain the output peak in the low rotation speed region of the engine E. Further, the shorter the length or the smaller the volume of the funnel 36, the more the intake inertia can be suppressed, and the output peak in the high rotation speed region of the engine E can be easily obtained.

As shown in FIG. 6, the first funnel 36-1 and the fourth funnel 36-4, which are two outer funnels located at both ends in the series direction, are two inner funnels arranged inside in the series direction. It is formed shorter than the 2nd funnel 36-2 and the 3rd funnel 36-3. In the present embodiment, the inner third funnel 36-3 is formed to be the longest, and the second funnel 36-2 is formed to be the second longest. Further, the first funnel 36-1 is formed to be the third longest, and the fourth funnel 36-4 is formed to be the shortest. Since the downward protrusion length from the lower case half body 34b of each funnel 36-1 to 36-4 is the same, the length of the funnel is determined by the length of the portion protruding into the cleaner case 34. .. The longest third funnel 36-3 is composed of curved pipes, and the other three funnels 36-1, 36-2, 36-4 are composed of straight pipes.

As described above, in the present embodiment, the length of the fourth funnel 36-4 at the right end opposite to the left side of the vehicle body on which the side stand 38 (FIG. 2) is arranged is the shortest. Further, in the present embodiment, the longest third funnel 36-3 is arranged next to the shortest fourth funnel 36-4. As a result, it is easy to suppress the bias of the left and right weight balance due to the different lengths of the funnel 36.

Further, in the present embodiment, the difference in length between the longest third funnel 36-3 and the second longest second funnel 36-2 is the shortest fourth funnel 36-4 and the second shortest first. It is formed larger than the difference in length from the funnel 36-1.

The clean air CA guided from the intake duct 52 to the air cleaner 25 is sent by the traveling wind pressure. In the present embodiment, the clean air CA is guided into the air cleaner 25 from one side to the other in the vehicle width direction by the intake duct 52, thereby passing through the element 35 in the vicinity of the upper wall of the upper case half body 34a and the vehicle. The pressure increases by gathering on the other side (right side) in the width direction. Since the upstream end 36a of the longest third funnel 36-3 is located near the upper wall and on the other side in the vehicle width direction, high-pressure air is easily sucked from the longest third funnel 36-3. Thereby, the engine output in the low rotation speed region of the engine E can be increased.

For example, in this embodiment, the length of the longest third funnel 36-3 is formed to be larger than the sum of the lengths of the other three funnels 36-1, 36-2, 36-4. As a result, three relatively short funnels 36-1, 36-2, 36-4 increase the output of the engine E in the high rpm region, while one relatively long third funnel 36-3 lowers the engine E. It is possible to suppress a decrease in engine output in the rotation region. Also, for the relatively short funnels 36-1, 36-2, and 36-4, by making the lengths different, it is possible to prevent the output peak from becoming steep in the high rpm region and cover the entire high rpm region. Output can be improved.

In the present embodiment, the three funnels 36-1, 36-2, 36-4 other than the longest third funnel 36-3 are located below the mating surface 55 of the air cleaner 25. That is, only the upstream end of the longest third funnel 36-3 is located above the mating surface 55 of the air cleaner 25. As a result, high-pressure air tends to remain around the longest third funnel 36-3, and it is easy to further increase the engine output in the low speed region of the engine E.

In this embodiment, as is clear from FIG. 5, the longest third funnel 36-3 has an opening 65 at the upstream end 36a as compared with the other three funnels 36-1, 36-2, 36-4. It is formed large like a bell mouth. That is, it is formed in an enlarged diameter shape in which the opening area increases toward the upstream side. As described above, the upstream side of the third funnel 36-3 has a larger pipeline cross-sectional area than the main body portion on the downstream side thereof. In the other three funnels 36-1, 36-2, 36-4, the opening 65 of the upstream end 36a is the same as or substantially the same as the cross-sectional area of the main body portion on the downstream side thereof. In each funnel 36-1 to 36-4, the cross-sectional area S of the main body portion excluding the opening 65 is the same. Therefore, each funnel 36-1 to 36-4 is formed with a different ratio (S / L) of the cross-sectional area S and the length L of the funnel 36.

The length of the funnel 36 is set in consideration of the timing of the fuel explosion for each cylinder. In this embodiment, the fuel supplied to the cylinders corresponding to the outer funnels 36-1 and 36-4 and the cylinders corresponding to the inner funnels 36-2 and 36-3 explode alternately. Specifically, the first cylinder explodes first, and then the second cylinder, the fourth cylinder, and the third cylinder explode in this order. That is, the explosion time in the 3rd cylinder corresponding to the longest 3rd funnel 36-3 is after the explosion in the 4th cylinder corresponding to the short outer 4th funnel 36-4, and the 1st funnel 36-. It is before the explosion in the 1st cylinder corresponding to 1. The explosion time in the 2nd cylinder corresponding to the 2nd longest 2nd funnel 36-2 corresponds to the 4th funnel 36-4 after the explosion in the 1st cylinder corresponding to the 1st funnel 36-1. Before the explosion in the 4th cylinder. In this way, the ignition timings of adjacent cylinders are set so that they do not come close to each other. However, the explosion order of the cylinders is not limited to this.

Regarding the arrangement of the two inner funnels 36-2 and 36-3, the arrangement is set so that air can easily enter the intake port 26a of the engine E in FIG. 4, that is, the fuel injection device 27c blows a large amount of fuel. ing. Such a setting is influenced by, for example, the form of the set of exhaust pipes 28 (FIG. 1). In the present embodiment, after the exhaust pipes 28 extending for each cylinder are assembled below the engine E, the exhaust pipes 28 after the assembly are located on the other side (right side) in the vehicle width direction with respect to the vehicle body center line extending in the front-rear direction. .. That is, the funnel 36 on the side (right side) where the exhaust pipe 28 after assembly is located is set long. The second funnel 36-2 may be longer than the third funnel 36-3 in consideration of the fuel injection amount of the fuel firing device 27c and the assembly form of the exhaust pipe 28.

Next, the relationship between the length of the funnel 36 and the structure of the air cleaner 25 will be described. As described above, the air cleaner 25 has a bottom wall 58 formed on the lower case half body 34b and upper walls 56 and 57 formed on the upper case half body 34a. The bottom wall 58 constitutes a funnel installation wall 58 on which the funnel 36 is provided. Further, the curved portion 57 in the latter half of the upper wall constitutes the facing wall 57 facing the funnel installation wall 58.

As described above, the curved portion 57 forming the latter half of the upper wall of the upper case half body 34a shown in FIG. 4 bulges upward smoothly and is smoothly curved downward at the rear portion. As a result, a sufficient space is formed around the funnel 36.

As shown in FIG. 7, the facing wall 57 has an intermediate portion 66 at the center of the vehicle width direction (series direction) W and a bottom wall (funnel installation wall) 58 from the intermediate portion 66 toward the outside of the vehicle width direction W. It has two outer portions 68, 68 that extend downwardly so as to approach. At least a part of the two outer funnels 36-1, 36-4 on both sides in the vehicle width direction W is arranged below the outer portion 68 of the facing wall 57. That is, at least one of the outer funnels 36-1 and 36-4 is provided on the funnel installation wall 58 at a portion facing the outer portion 68.

A breather hose 69 is connected to the rear end of the air cleaner 25. The breather hose 69 leads the blow-by gas G of the engine E to the clean chamber 37 of the air cleaner 25. Specifically, a hose attachment port 70 projecting diagonally downward and rearward is provided at the rear end of the air cleaner 25, and a breather hose 69 is connected to the hose attachment port 70.

As shown in FIG. 5, a vertical wall 72 extending upward from the bottom wall 58 is formed so as to surround the hose attachment port 70 from the vehicle width direction and from the front. The opening at the upper end of the vertical wall 72 constitutes an introduction port 74 for guiding the blow-by gas G to the clean chamber 37 in the air cleaner 25.

In the present embodiment, the introduction port 74 is provided at a position between the shortest fourth funnel 36-4 and the longest third funnel 36-3 in the vehicle width direction W. Further, as shown in FIG. 4, the introduction port 74 is the shortest fourth funnel 36-4 and the shortest in the height direction H between the bottom wall (funnel installation wall) 58 and the upper wall (opposing wall) 57. It is formed in the middle position of the long third funnel 36-3.

As described above, a recess 60 recessed upward is formed in the central portion in the vehicle width direction of the latter half of the bottom wall 58. Since the inner funnels 36-2 and 36-3 adjacent to the recess 60 are formed longer than the outer funnels 36-1 and 36-4, the air in the space away from the recess 60 is sucked in. Can be done. As a result, a decrease in engine output can be suppressed. In particular, the longest third funnel 36-3 is curved to avoid the recess 60.

The opening (upstream opening) 65 at the upstream end of the longest curved third funnel 36-3 faces the cleaner inlet 25a (air intake) on the left side of the front portion of the air cleaner 25, as shown in FIG. It is facing away from the direction. In the present embodiment, in a plan view, the axial direction D1 of the cleaner inlet 25a faces diagonally rearward to the right, and the axial direction D2 of the upstream opening 65 of the third funnel 36-3 faces diagonally forward to the right. .. Further, the cleaner inlet 25a is provided on one side (left side) in the vehicle width direction with the center line C2 in the front-rear direction of the air cleaner 25 interposed therebetween, and the upstream opening 65 of the longest third funnel 36-3 is on the other side (left side) in the vehicle width direction. It is provided on the right side).

According to the above configuration, as shown in FIG. 8, as the output of the entire engine, it is possible to obtain a characteristic in which four types of engine characteristics having different output curves according to the engine speed are superimposed. As a result, it is possible to suppress a drop in output in the region before and after the engine speed at which the output peaks, as compared with the conventional example in which the funnel shape is the same. As a result, it is possible to improve the output in a wide range of engine rotation. In particular, a motorcycle has a wider range of engine E rotation speeds than a four-wheeled vehicle (for example, 0 to 17,000 revolutions per minute). In the present embodiment, as described above, by using the four types of funnels 36, it is possible to improve the output even in a wide range of engine rotation.

The present embodiment is an engine structure of a vehicle in which an intake pressure is increased by a running wind pressure. In this case, when traveling at high speed, the pressure in the air cleaner 25 of FIG. 5 tends to be relatively high due to the traveling wind pressure, and when traveling at low speed, the traveling wind pressure is low and the pressure in the air cleaner 25 is relatively low. By forming one third funnel 36-3 sufficiently longer than the remaining funnels 36-1, 36-2, 36-4, the decrease in engine output is suppressed even at low speeds when the pressure in the air cleaner 25 becomes low. be able to.

As shown in FIG. 7, the two outer funnels 36-1 and 36-4 are formed shorter than the two inner funnels 36-2 and 36-3. As a result, it is possible to prevent the outer funnels 36-1, 36-4 from interfering with the outer portion 66 of the facing wall (upper wall) 57 of the air cleaner 25. As a result, the engine characteristics of each cylinder can be easily changed in the limited space of the air cleaner 25, and the output can be easily improved in a wide range of engine rotation range.

Further, by changing the length of the inner funnels 36-2, 36-3 piped in the area where the distance between the bottom wall 58 and the upper wall 57 is long, two types of relatively long inner funnels 36-2, 36- 3 can be provided. As a result, it is easy to adjust the characteristics of the engine E in the low speed range, and it is easy to suppress a decrease in the engine output in the low speed range of the engine E.

As shown in FIG. 6, the longest third funnel 36-3 has a larger area of the upstream opening 65 than the other three funnels 36-1, 36-2, 36-4. As a result, in the third funnel 36-3 having a large length, it is possible to suppress an increase in intake resistance due to the length of the intake passage.

As shown in FIG. 5, the upstream opening 65 of the longest third funnel 36-3 faces the direction D2 deviating from the direction D1 facing the cleaner inlet 25a of the air cleaner 25. The longest third funnel 36-3 tends to have a louder intake noise than the other three funnels 36-1, 36-2, 36-4. According to the above configuration, it is possible to prevent the intake noise generated at the longest third funnel 36-3 from heading toward the cleaner inlet 25a. As a result, it is possible to suppress the intake noise from leaking to the outside from the cleaner inlet 25a, and it is possible to reduce the engine noise.

The intake duct 52 is connected to the center line C2 in the front-rear direction of the air cleaner 25 from the right side to the left side in the vehicle width direction, and the upstream opening 65 of the longest third funnel 36-3 opens to the right side in the vehicle width direction. There is. Due to the fact that the direction of the intake duct 52 is displaced in the vehicle width direction, the air pressure tends to be biased inside the air cleaner 25. According to this configuration, the upstream opening 65 of the longest third funnel 36-3 opens in a relatively high pressure region near the upper wall inside the air cleaner 25 in FIG. 4, so that relatively high pressure air is used. Is incorporated into the longest funnel 36-3, and the engine torque can be increased in the low speed range of the engine E.

The blow-by gas G inlet 74 is located between the shortest fourth funnel 36-4 and the longest third funnel 36-3 in the vehicle width direction W, and is the shortest fourth funnel 36-4 and the longest shown in FIG. It is formed at an intermediate position in the height direction H of the long third funnel 36-3. This makes it possible to prevent the blow-by gas G from flowing into one cylinder in a concentrated manner. As a result, the influence of blow-by gas G per cylinder can be suppressed.

The shortest fourth funnel 36-4 shown in FIG. 5 is arranged on the right side opposite to the side stand 38 (FIG. 2) in the vehicle width direction W. As a result, it is possible to prevent the liquid (for example, oil) that has entered the air cleaner 25 inclined to the left when the side stand 38 stands up from flowing into the cylinder through the funnel 36.

The fuel in the cylinder corresponding to the outer funnels 36-1 and 36-4 and the fuel in the cylinder corresponding to the inner funnels 36-2 and 36-3 explode alternately. As a result, the short funnels 36-1, 36-4 and the long funnels 36-2, 36-3 alternately suck the intake air, so that the intake air of the two long funnels 36-2, 36-3 is continuous. Compared with the case, it is easy to increase the intake amount in the two long funnels 36-2 and 36-3, and it is easy to improve the engine torque in the low speed range of the engine E.

In the above embodiment, the lengths of the four funnels 36 are different in the four-cylinder engine, but it is sufficient that three or more types of funnels 36 having different shapes are provided. For example, as shown in FIG. 9, the outer funnels 36-1, 36-4 may have the same shape (length). That is, in the example of FIG. 9, the third funnel 36-3 is the longest, the second funnel 36-2 is the second longest, and the first funnel 36-1 and the fourth funnel 36-4 are the same length and the shortest. .. According to the example of FIG. 9, the funnel 36 can be shared between the 1st cylinder and the 4th cylinder, and the cost can be reduced.

The present invention is not limited to the above embodiments, and various additions, changes, or deletions can be made without departing from the gist of the present invention. For example, in the above embodiment, the 4-cylinder engine has been described, but any engine may have 3 or more cylinders, and may be, for example, a 3-cylinder engine or a 6-cylinder engine. Further, regardless of the number of cylinders, the funnel 36 may have three or more shapes. Further, the engine is not limited to the in-line engine, and may be a V-type engine.

The intake device of the present invention is suitably used for a small displacement engine having a relatively low torque, for example, a multi-cylinder engine having a small displacement of 400 cc or less, preferably 250 cc or less. In a multi-cylinder engine with three or more cylinders with a small displacement, the distance in the vehicle width direction between adjacent funnels is small. Therefore, if the air is taken in by the adjacent funnel immediately after being taken in by one funnel, the amount of air taken in the air cleaner tends to be small. Further, the intake amount tends to decrease when the engine is running at a low speed or when the engine speed is low. Even in such a situation, according to the present invention, it is possible to suppress a decrease in the intake air amount and effectively suppress a decrease in the engine output. However, the intake device of the present invention can also be applied to a multi-cylinder engine having a large displacement. Further, the intake device of the present invention can be applied not only to an intake system that supplies air to an engine by using ram pressure, but also to an intake system that supplies air to an engine by natural aspiration without using ram pressure.

In the above embodiment, the throttle valve is controlled by the electric throttle, but the throttle valve may be controlled by the wire operation amount according to the operation amount of the throttle grip. Further, the cross-sectional shape of the funnel is not limited to a circle, and may be a shape other than a circle such as an ellipse. Therefore, such things are also included within the scope of the present invention.

25 Air cleaner (air tank)
25a Cleaner inlet (air intake of air tank)
26a Intake port 36 Funnel 38 Side stand 36a Upstream end of funnel 36b Downstream end of funnel 36-1, 36-4 Outer funnel 36-2, 36-3 Inner funnel 36-3 Longest funnel 36-4 Longest Small funnel 52 intake duct (duct)
57 Opposing wall 58 Bottom wall (funnel installation wall)
65 Upstream end opening (upstream side opening)
66 Intermediate part of the facing wall 68 Outer part of the facing wall 74 Inlet A Air C2 Front-rear direction center line of air cleaner (air tank) E Engine G Blow-by gas H Height direction W Vehicle width direction (series direction)

Claims (9)

It is an intake device of an engine equipped with three or more cylinders.
An air tank that stores the air supplied to the engine and
The upstream end is open into the air tank and the downstream end is provided with a funnel connected to the intake port of the engine.
The funnel is an intake device for an engine provided for each cylinder and having three or more types of funnel shapes. In the intake device of the engine according to claim 1, the air tank has a funnel installation wall on which the funnel is provided and a facing wall facing the funnel installation wall.
The facing wall has an intermediate portion of a central portion in the series direction in which the funnels are lined up, and two outer portions extending from the intermediate portion toward the outside in the series direction so as to approach the funnel installation wall. ,
Of the three or more funnels, at least a part of two outer funnels on both sides in the series direction is provided on the funnel installation wall at a portion facing the outer portion of the facing wall.
The two outer funnels are engine intake devices formed to be shorter in length than the inner funnels arranged inside the two outer funnels. In the intake device of the engine according to claim 2, the engine has four or more cylinders.
An intake device for an engine provided with a plurality of inner funnels having different lengths. In the intake device of the engine according to claim 2 or 3, the longest funnel is the intake device of the engine in which the area of the upstream opening is larger than that of the other funnels. In the intake device of the engine according to any one of claims 2 to 4, the upstream opening of the longest funnel is the intake of the engine facing a direction away from the direction facing the air intake of the air tank. apparatus. In the intake device of the engine according to claim 5, the engine is mounted on a vehicle.
A duct that takes in the running wind into the air tank is connected to the air intake,
The duct is connected so as to go from one side to the other in the vehicle width direction with respect to the center line in the front-rear direction of the air tank.
The longest upstream opening of the funnel is the intake device of the engine that opens to the other side in the vehicle width direction. In the intake device of the engine according to any one of claims 2 to 6, the position between the shortest funnel and the longest funnel in the air tank in the series direction, that is, the funnel installation wall and the facing wall. An engine intake system in which an inlet for guiding blow-by gas is formed in the air tank at a position between the shortest funnel and the longest funnel in the height direction between the two. In the intake device of the engine according to any one of claims 2 to 7, the engine is mounted on a motorcycle, and the funnels are arranged in the vehicle width direction.
The shortest funnel is the intake system of the engine, which is located on the opposite side of the side stand in the vehicle width direction. In the intake device of the engine according to any one of claims 2 to 8, the intake device of the engine in which the fuel in the cylinder corresponding to the outer funnel and the fuel in the cylinder corresponding to the inner funnel explode alternately. ..

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