JPH03134221A - Intake device for 2-cycle v-engine - Google Patents

Abstract

PURPOSE:To make an opening area of an intake port spreadable by forming the same straight line by the fellow crankshaft direction center lines on a mounting seat surface of each intake port. CONSTITUTION:In an engine 10, intake ports 32a, 32b for each cylinder 12a, 13a are parallelly arranged and formed in the center part of a V-bank of a crankcase 11 so that a mounting seat surface 32c of reed valves 18, 19 is placed in parallel to a crankshaft 17. The fellow center lines C in a direction of each crankshaft 17 on the mounting seat surface 32c of each intake port 32a, 32b are placed so as to form the same straight line. Thus by decreasing restriction due to a relation between the lower and upper side cylinders 13a, 12a in lower and upper edge positions of each intake port 32a, 32b, opening height can be increased by sufficiently utilizing a bank inner part of a front case 11a of the crankcase 11. Accordingly, an opening area of each of intake ports 32a, 32b can be extended.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an intake device for a two-stroke V-type engine suitable for motorcycles, and in particular, the invention relates to an intake device for a two-stroke V-type engine suitable for motorcycles, and in particular, an intake device in which intake ports are arranged in parallel in the bank inside the crankcase. In this case, the present invention mainly relates to a structure in which the opening area of the intake port can be expanded by increasing the dimension (opening height) of the intake port in the direction perpendicular to the crankshaft.

[Conventional technology]

As an intake device for a two-stroke V-type engine, there is one in which an intake port communicating with a crank chamber is formed in the V-bank of the crankcase to directly introduce an air-fuel mixture into the crankcase. In such an intake system, in order to avoid interference between the carburetor and the cylinder head, etc., the carburetor for the upper cylinder may be deviated downward, and the carburetor for the lower cylinder may be deviated upward. In this case, for example, as shown in FIG. 11, the center line L1 of the upper cylinder intake lower 3 that extends in the crankshaft direction is located downward, and the center line L2 of the lower cylinder intake lower 4 is located upward. The two openings are formed to be offset from each other so that the openings are located at the same positions, and a difference in offset occurs between the two openings. Note that 75.76 is for each intake lower 3.
It is a reed valve attached to 74, and its flange 75
a, 76a are bolted and fixed to the mounting seats 73a, 74a. Further, 71 and 72 are connection openings for the upper and lower cylinders.

[Problem that the invention seeks to solve]

By the way, in order to improve engine performance, it is important to introduce a larger amount of air-fuel mixture into the crankcase by increasing the opening area of the intake port. However, as in the case of FIG. 11 described above, the upper cylinder intake lower 3. When the intake lower 4 for the lower cylinder is displaced downward and upward, respectively, the positions of the lower and upper edges of the intake port are constrained by the relationship with the lower and upper cylinders, and the inner part of the bank of the crankcase is It cannot be used sufficiently as an opening, and the opening height H of each intake lower 3.74 becomes low, resulting in a case where a sufficient opening area cannot be secured. In particular, when the bank angle is small, such as 90 degrees or less, the internal area of the bank in the crankcase itself is not sufficient, so there is a concern that the necessary opening area may not be secured.

The present invention has been made in view of the above-mentioned conventional problems, and in particular, it is possible to enlarge the opening area by effectively utilizing the internal part of the bank of the crankcase to ensure a sufficient opening height of the intake port. The object of the present invention is to provide an intake system for a crankcase reed type two-stroke V-type engine.

[Means for solving problems]

The present invention provides a crankcase in which an intake port communicating with the crank chamber is formed in the V-bank inner portion of the crankcase, and a reed valve is provided in the intake port to directly introduce the air-fuel mixture into the crankcase. In the intake system of a reed-type two-stroke V-type engine, the above-mentioned intake ports for each cylinder are arranged in parallel in the central part of the bank of the crankcase so that the mounting surface for the reed valve is parallel to the crankshaft. It is characterized in that the center lines in the crankshaft direction on the mounting seat surface of the mouth are in the same straight line.

Here, in the present invention, each crankshaft direction center line forms the same straight line when each mounting seat surface forms the same plane, and each mounting seat surface forms an upper cylinder cylinder with the above-mentioned crankshaft direction center line opening. This includes both the case where the cylinder is rotated by a predetermined angle in the direction of the lower cylinder.

(Function) According to the intake device according to the present invention, since the center lines in the crankshaft direction on the mounting surface of each intake port form the same straight line,
Restrictions due to the lower and upper edges of each intake port in relation to the lower and upper cylinders are reduced, and the internal part of the bank of the crankcase can be fully utilized to increase the opening height, expanding the opening area accordingly. can.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 to 9 are diagrams for explaining an intake system for a two-cycle V-type motorcycle engine according to an embodiment of the present invention, in which FIG. 1 is a front view of the intake port, FIG. Fig. 3 is a partially sectional left and right side view, Fig. 4 to Fig. 7 are views showing the reed valve, Fig. 8 is a sectional plan view of the crankshaft portion, and Fig. 9 is a partial cross-sectional view of the device. FIG. 2 is a left side view of the motorcycle.

In the figure, reference numeral 1 denotes a motorcycle in which the embodiment device is adopted, and its body frame 2 has a head pipe 2a connected to the front ends of a pair of left and right main frames 2b each having a rectangular cross section by welding. The rear arm brackets 20 are welded to the rear end of the main frame 2b and connected to each other by a cross pipe (not shown). A radiator 31 is mounted between the lower surfaces of the left and right main frames 2b, and is supported by brackets 2d fixed to both frames 2b. Further, the head pipe 2a has a lower end that pivotally supports a front fork 4 that pivotally supports the front wheel 3 so that it can be steered left and right, and the rear arm bracket 2a
C supports a rear arm 6, which supports a rear wheel 5, at its rear end so as to be able to swing up and down. Note that 7 is a fuel tank and 8 is a seat.

The lower left and right parts of the left and right main frames 2b and the front part of the head pipe 2a are surrounded by a cowling 9, within which a water-cooled two-stroke V-type two-cylinder engine 10 is suspended and supported. This engine 1
0 is a crankcase 11 divided into two parts, front and rear cases 11a and llb, with an upper cylinder 12a connected to a connection opening 11c formed at the upper part of the front case lla, and a hood 1 to the upper side.
2b are stacked diagonally upward and connected with the head bolts 14, and the lower cylinder 13a and the lower head 13b are stacked diagonally downward in the connection opening lid formed at the bottom, and the head bolts 14 It has a combined configuration.

Here, the bank angle formed by the axis AlA2 of each cylinder 12a, 13a is 90 degrees, and when viewed from the front of the vehicle (the same applies hereafter), the upper cylinder 12a is on the right side and the lower cylinder 13a is on the left side. are doing. Further, each of the head bolts 14 is installed in screw holes 11h and lli formed at the four corners of the periphery of each of the connection openings 11C and lid, on the center side of the bank and on the center mD side in the engine width direction. The bolt hole 11h' located at is located closer to the mating cylinder than the center line. Further, in llj, 11, there are bolt holes for tightening the crankcase formed in the inner and outer portions of the respective connection openings 11C, 11d of the front case lla.

Pistons 15a and 15b slidably inserted into each of the cylinders 12a and 13a are connected to the front and rear cases lla of the crankcase 11 via connecting ronds 16a and 15b, respectively.
It is connected to a crankshaft 17 disposed between the base surfaces of the llb in the vehicle width direction.

The crankshaft 17 is an upper crankshaft 41 for the upper cylinder.
and a lower crankshaft 42 for the lower cylinder are assembled by press-fitting in the center, and this upper crankshaft 41
The outer and inner shaft portions 43 and 44 are assembled by press-fitting, and the lower crankshaft 42 is assembled by press-fitting the outer and inner shaft portions 45 and 46. That is, this crankshaft 17 is a 4-piece assembly type crankshaft, and the above-mentioned upper and lower crankshafts 41.4
The outer portions of the two crank webs 41b and 42b are supported by a roller bearing 52a and a ball bearing 52b, respectively, and the portion between the two crank webs is supported by a roller bearing 52c. In addition, the upper and lower connecting rods 16a, 1
6b are crank pins 44a of the upper and lower crankshafts 41 and 42, respectively.

46a, and each of the crank webs 4
The portions 1b and 42b are housed in crank chambers 11g and 11f, which are constituted by the front and rear cases 11a and Ilb.

Further, a balancer chamber 11g is formed in a bulge above the rear case llb and in the vicinity of the dividing surface 111 so as to extend parallel to the crankshaft 17.
A balancer shaft 47 is inserted in g. The balancer shaft 47 is supported at both ends by bearings 50.
A balancer weight 51a is attached to the more outwardly projecting portion and fixed with a nand 51b. A driven gear 48 fixed to this balancer shaft 47 is connected to the crankshaft 17.
It meshes with the drive gear 49 of.

Upper and lower intake ports 32a, 32b are formed in the bank inner portion of the front case Ila, and each intake port 32a, 32b is connected to the crank chamber 11e.
, llf.

Further, each mounting seat surface 32c, 32c for mounting a later-described road valve of each intake port 32a, 32b has a rectangular shape long in the direction of the crankshaft. The opening center D' on each mounting seat surface is located on the bisector B of the bank angle, and furthermore, each center vAC in the crankshaft direction is continuous on the left and right sides and forms the same straight line, and the crankshaft It is parallel to 17.

Further, the inner side portion 32d of the mounting seat surface 32C located on the engine center line is common to the left and right sides. In this way, the intake ports 32 a and 32 b are formed in parallel in the crankshaft direction and have the same opening area, and their respective mounting seats 32 c form the same plane.

When the front case lla is viewed from the side, it has an approximately isosceles triangle shape, and the connection opening 11c and lid are formed on the ridges of the triangle, and the intake ports 32a and 32b are formed at the vertices of the triangle, respectively. The mounting seat surface 32C of the intake port and the dividing surface 111 of the front case lla are parallel to each other.

Further, the angles formed between this dividing surface 11/ and the axes AI and A2 are each 45 degrees.

An integrated reed valve 53 is provided in each of the intake ports 32a and 32b.
Upper valve body 18. The lower valve body 19 has been inserted. The frame 54 of this reed valve 53 has an upper frame portion 54a and a lower frame portion 5.
4b are integrated by a cylinder portion 54c. Also, the upper side.

When viewed from the side, the lower frame portions 54a and 54b have a triangular shape with the apexes deviated upward and downward, respectively, and a valve plate 2 is provided on the ridge surface of the triangle for opening and closing an opening 54d formed in the portion.
1 is fastened together with the guide plate 22. The upper and lower valve bodies 18 and 19 are mounted horizontally, that is, so that the crests are parallel to the crankshaft, and the apexes are directed toward the upper and lower cylinders 12a and 13a. There is.

The tips of the cabbage cylinders 23 and 24 are inserted into each of the reed valves 18 and 19, and the respective flanges 23b and 24b are attached to the reed valves 53 and 24.
It is fixed to the mounting seat surface 32c together with the flange portion 54c. When viewed from the top, each of the ``cabinets'' 23 and 24 is bent outward to the left and right, and when viewed from the side in the direction of the crankshaft, it extends forward on the bisector B. A carburetor 25.26 is attached to the tip of each carburetor joint 23.24. Each vaporizer 25.
26, the axis of the intake passage is slightly lower than the bisector B, and is located at the same height when viewed from the side. Furthermore, an air cleaner 27 arranged inside the cowling 9 is connected to the air vase 25,26.

Next, the effects of this embodiment will be explained.

In the intake system of this embodiment, when the insides of the crank chambers 11e and 11f become negative pressures as the pistons 15a and 15b rise, the valve bodies 1B and 19 open, and after the outside air is filtered by the air cleaner 27, the carburetor 25 26, where the fuel is mixed to form an air-fuel mixture, which passes through the carburetor cylinder 23, 24 and the valve body 18, 19 to the crank chamber 11e.

! is sucked into lf, and then scavenged i! It is introduced into the cylinder from 17a.

In this embodiment of the intake device that operates in this manner, the opening centers D' of the intake ports 32a and 32b are located on the bisector B of the bank angle when viewed in the direction of the crankshaft, and each intake port 3
Since each crankshaft direction center line C on the mounting seat surface 32c of 2a, 32b is formed to form the same straight line, the inner part of the bank of the front case Ila can be used as an intake opening without waste, and each intake port 32a, 32b A sufficient opening height H can be secured. In addition, the inner side portion 32d of the mounting seat surface 32c
Since it is shared between the left and right sides, the opening width W can be expanded compared to the case where separate mounting seats are provided, and as a result, the opening area can be expanded.

Then, the reed valve 53 is attached to the upper and lower frame portions 54a and 5.
4b is integrated with the flange portion 54C, so that the inner side portion 32d of the mounting seat surface 32c can be shared with a narrow one. If a separate reed valve is installed at each intake port, as shown in Fig. 11, the reed valve 75.
A width corresponding to each of the mounting flange portions 75a' and 76a-' of 6 is required, and the opening width cannot be increased that much.

In the above embodiment, a case has been described in which the mounting seats 32c of the intake ports 32a and 32b are on the same plane, but the intake ports according to the present invention are essentially aligned with the center line in the crankshaft direction on the mounting seats. It is sufficient for C to form the same straight line, but not necessarily to form the same plane. For example, the 10th
As shown in the figure, the mounting seats 32c of the upper and lower cylinder intake ports 32a and 32b may be rotated by a certain angle downward and upward, respectively, about the center line 0 in the crankshaft direction.

In this case, the effect is that a sufficient opening area can be secured as in the above embodiment, and furthermore, the carburetor can be deflected downward or upward according to the rotation angle of the mounting seat while using a carburetor joint of the same shape. This makes it possible to share parts.

[Effects of the Invention] As described above, according to the intake system for a two-stroke type engine according to the present invention, the center lines in the crankshaft direction on the mounting surfaces of the upper and lower cylinder intake ports form the same straight line. As a result, the opening height of each intake port can be increased by effectively utilizing the inner part of the V-bank of the crankcase, and a sufficient opening area can be ensured to improve engine performance.

[Brief explanation of the drawing]

1 to 9 are diagrams for explaining an intake system for a two-stroke V-type engine according to an embodiment of the present invention,
Fig. 1 is a front view of the intake port, Fig. 2 is a partially sectional left side view, Fig. 3 is a partially sectional right side view, and Figs. 4 to 6 are front views of the reed valve frame. The plan view, right side view, and FIG. 7 are cross-sectional views taken along the line ■-■ in FIG. 5, FIG. 8 is a cross-sectional view taken along the ■-■ lines in FIG. 2, and FIG. A left side view of the two-wheeled vehicle, FIG. 10 is a schematic diagram showing a modified example of the shape of the mounting seat of the intake port, and FIG. 11 is a front view of the intake port portion for explaining the conventional problems. In the figure, 10 is a two-stroke V-type engine, 11 is a crankcase, lie, llf are crank chambers, 12a,
13a is the upper and lower cylinders, 1819 is the upper and lower valve body (
32a and 32b are intake ports, 32c is a reed valve mounting seat surface, and C is a center line in the crankshaft direction.

Claims (1)

[Claims] (1) A plurality of cylinders are arranged to form a V bank, and an intake port communicating with the crank chamber is formed in the inside of the V bank of the crankcase, and the air-fuel mixture is directly introduced into the crankcase from the intake port. In the intake system of a crankcase reed type 2-stroke V-type engine,
The intake ports for each cylinder are arranged in parallel in the center of the V-bank of the crankcase so that the reed valve mounting surface is parallel to the crankshaft, and the center lines in the crankshaft direction on each mounting surface are the same. An intake system for a two-stroke V-type engine characterized by being arranged in a straight line.