JPH06146895A - Intake device of pre-compression type two-cycle engine - Google Patents

Abstract

(57) [Summary] [Object] To improve the engine performance by preventing the reed closing operation from being delayed even in the high-speed rotation range in the intake system of the pre-compression type two-cycle engine of the reed valve. [Structure] From the outside of the crankcase 2 to the crank chamber 2a
An intake port 12 leading to the This intake port 12
In addition, the reed valve 13 which allows the inflow of the intake air 29 only toward the crank chamber 2a is provided. This reed valve 13
Is composed of a valve main body 30 having a valve hole 35 and attached to the crankcase 2 side, and an elastic lead 36 attached to the valve main body 30 and capable of opening and closing the valve hole 35. An interlocking device 38 for opening and closing the lead 36 in conjunction with the crankshaft is provided, and the interlocking device 38 causes the lead 36 to close at a predetermined crank angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system for a reed valve precompression type two-cycle engine mounted on a motorcycle or the like.

[0002]

2. Description of the Related Art In general, an intake system for a two-cycle engine is provided with an intake port that communicates with the crank chamber from the outside of the crankcase, and the intake port allows the inflow of intake air only toward the crank chamber. A valve is provided, and the reed valve is composed of a valve body having a valve hole and attached to the crankcase side, and a reed attached to the valve body and closing the valve hole by elastic force so as to open and close freely. There is. When the negative pressure in the crank chamber increases during the intake and compression strokes, the reed is elastically bent by the kinetic energy of the intake air that is about to flow into the crank chamber, and the reed is opened to open. The intake air flows into the crank chamber through the valve hole. Further, in the explosion and the scavenging stroke following the above stroke, the intake air in the crank chamber is pre-compressed, and this is sent to the combustion chamber through the scavenging port and used for combustion. In the above case, at the time of pre-compression of the intake air in the crank chamber, the reed closes the valve hole due to the elastic tendency of the reed to restore and the increase in the intake pressure in the crank chamber, and Are prevented from being blown back to the upstream side of the intake port.

[0003]

By the way, particularly in the high-speed range of the engine, when the suction, compression stroke, explosion, and scavenging stroke are changed, the negative pressure in the crank chamber fluctuates rapidly, which causes the reed closing operation. It cannot follow quickly, that is, the lead closing operation tends to be delayed. Such a delay in the reed closing operation causes the intake air to be blown back through the reed valve, resulting in a reduction in the intake efficiency and a hindrance to the improvement of the engine performance.

[0004]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the above circumstances, and in a reed valve precompression type two-cycle engine intake system, the reed closing operation is not delayed even in a high speed rotation range. And to improve engine performance.

[0005]

In order to achieve the above object, the present invention is characterized in that a reed valve is provided in an intake port of a crankcase, and the reed valve is provided with a valve hole. A valve body attached to the side,
When configured with an elastic lead attached to the valve body to open and close the valve hole, interlocking means for interlocking the lead with the crankshaft to open and close is provided. The point is that it is designed to be closed at the crank angle of.

[0006]

[Operation] The operation of the above configuration is as follows. A reed valve 13 is provided in the intake port 12 of the crankcase 2,
This reed valve 13 is provided with a valve main body 30 having a valve hole 35 and attached to the crankcase 2 side, and the valve main body 3
When it is configured with a lead 36 attached to 0 to open and close the valve hole 35, an interlocking device 38 for interlocking the lead 36 with the crankshaft 3 to open and close is provided. 36 is closed at a predetermined crank angle. Therefore, it is possible to prevent the closing operation of the lead 36 from being delayed in the high speed range.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4, reference numeral 1 is a V-type two-cylinder two-cycle engine mounted on a motorcycle. Also,
The arrow Fr in the drawing indicates the front side thereof, and the left and right described below refer to the direction toward the front side. The crankcase 2 of the engine 1 supports a crankshaft 3 whose axial center extends in the left-right direction.
It is provided in the inner crank chamber 2a. The same crankcase 2 is provided with a lower cylinder 4 protruding in a V-shape toward the front, and a cylinder head 5 is attached to the protruding end of each cylinder 4. A piston 7 is slidably fitted in each cylinder 4 in the axial direction thereof, and the piston 7 is connected by a connecting rod 8 to the crankshaft 3
Are linked to.

Inside the cylinder 4, the cylinder head 5
A space surrounded by and the piston 7 is a combustion chamber 9. An ignition plug facing the combustion chamber 9 is provided.
An intake port 12 is formed in a portion of the crankcase 2 corresponding to the base of each cylinder 4, and the intake port 12 communicates the outside of the crankcase 2 with the crank chamber 2a. The intake port 12 is provided with a reed valve 13, and the reed valve 13 is connected with an intake pipe 14 and a carburetor 15. A scavenging passage 17 is formed in the cylinder 4 to communicate the inside of the crankcase 2 toward the combustion chamber 9. Further, an exhaust passage 19 is formed in the cylinder 4 for communicating the combustion chamber 9 to the outside.

The balancer shaft 20 is parallel to the crankshaft 3.
And an idle shaft 21 are provided. The balancer shaft 20 supports the balancer and is rotatably supported by the crankcase 2 around the axis thereof. The balancer shaft 20 and the idle shaft 21 respectively correspond to the crankshaft 3
Are interlocked by a gear set 22. The balancer shaft 20 rotates at the same speed in conjunction with the crankshaft 3 and absorbs the vibration that is about to occur due to the reciprocating motion of each piston 7 and the connecting rod 8.

A transmission 24 is connected to the rear of the crankcase 2. This transmission 24 has an output shaft 25
And a gear speed change mechanism for interlockingly connecting the output shaft 25 to the crankshaft 3. In addition, the output shaft 25
A drive chain wheel 26 is attached to the drive chain wheel 26, and rear wheels are connected to the drive chain wheel 26 via a transmission chain 27. The power of the engine 1 is transmitted to the rear wheels via the transmission 24, the drive chain wheel 26, the transmission chain 27, etc., so that the motorcycle can run.

Since both of the reed valves 13 and 13 and those related thereto have the same structure, the upper cylinder 4
Only those corresponding to will be explained. Reed valve 1 above
Reference numeral 3 permits the inflow of the intake air 29 only toward the crank chamber 2a. The valve body 30 of the reed valve 13
Has a tubular body 31 that is rectangular in a front view and an outward flange 32 that is integrally formed with the rear edge of the tubular body 31. The outward flange 32 is attached to the opening edge of the intake port 12 in the crankcase 2, whereby the reed valve 13 is supported on the crankcase 2 side.

Further, the front end of the cylindrical body 31 projects into the crank chamber 2a, and this projecting end has an isosceles triangle shape in plan view (FIG. 1). The inside of the cylindrical body 31 is the intake passage 34.
The intake passage 34 has a pair of left and right rectangular valve holes 35 open toward the crank chamber 2a at the front end thereof.
35, and these valve holes 35, 35 are formed in the left and right portions of the protruding wall of the cylindrical body 31. Further, the reed valve 13 includes a pair of left and right reeds 36, 36. Each of these leads 36 can open and close the corresponding valve hole 35 corresponding thereto. Further, each of the leads 36 is formed of CFRP or the like of the same material as the conventional one end side fixed type lead,
It is elastically deformable.

Interlocking means 38 is provided for interlocking each of the leads 36 with the crankshaft 3 to open / close the crankshaft 3 at a predetermined crank angle. The interlocking means 38
Has a pair of left and right pivotal shafts 39, 39 extending along the side wall of the base of the tubular body 31. Each of these pivots 39
Is rotatably supported by a pair of upper and lower bearings 40, 40 on the outer side wall of the base of the tubular body 31.

A boss portion 41 is externally fitted and fixed to a vertically middle portion of each pivot shaft 39, and a rear edge of each lead 36 is detachably screwed to the boss portion 41 by a bolt 42. On the other hand, the front edge of each of the leads 36 is a free end, and is rotatable left and right around the axis of the pivot shaft 39 together with the pivot shaft 39. And this lead 36
When is rotated (closed) to the cylindrical body 31 side, the valve hole 35 is closed as shown by the solid line in each figure. On the other hand, when the valve body 35 is rotated (opening operation) away from the cylindrical body 31, the valve hole 35 is opened as shown by a virtual line in FIGS. 1 and 3.

A nut portion 44 is integrally formed on the lower portion of each boss portion 41 at a slight distance in the radial direction of the pivot shaft 39. The nut portion 44 has an axis parallel to the pivot shaft 39, and a bolt 45 is screwed thereto.
A cam engagement shaft 46 is coaxially attached to the lower end of the bolt 45.
The cam engaging shaft 46 projects below the nut portion 44.

An interlocking shaft 47 is provided near the lower parts of the left and right cam engaging shafts 46, 46 in parallel with the crankshaft 3, and the interlocking shaft 47 is mounted on the crankcase 2 by a pair of left and right bearings 48, 48. It is supported. The left and right midway portions of the interlocking shaft 47 are fitted into the recessed grooves 43 formed in the inner surface of the crank chamber 2a which is close to the lower surface of the cylindrical body 31.

A pair of left and right annular cam engagement grooves 49, 49 is formed on the outer peripheral surface of the interlocking shaft 47. The cam engaging grooves 49, 49 are formed symmetrically with each other, and the cam engaging shaft 46 and the cam engaging groove 49 corresponding to each other are engaged with each other by cam engagement. The interlocking shaft 47 is interlockingly connected to the balancer shaft 20 by a gear set 50. The interlocking shaft 47 rotates at the same speed in conjunction with the balancer shaft 20, that is, at the same speed as the crankshaft 3 (arrow R in the figure).

In FIG. 5, the right cam engaging groove 49 is developed on a plane for one rotation (L) about the axis of the interlocking shaft 47. The cam engagement groove 49 is displaced toward the center of the interlocking shaft 47 in the axial direction (displaced to the left) and the closed groove 52 is displaced toward the shaft end of the interlocking shaft 47 (displaced to the right). Open groove 5
3, a closing movement groove 54 when moving forward from the closing groove 52 to the opening groove 53, and an opening movement groove 55 when moving forward from the opening groove 53 to the closing groove 52. There is.

In the above case, the closed groove 52, the open groove 53,
The groove width of the closing operation groove 54 is slightly larger than the diameter dimension of the cam engagement shaft 46, but the groove width of the opening operation groove 55 is made sufficiently larger than the diameter dimension of the cam engagement shaft 46. .

In the states shown by the solid lines in FIGS. 1, 4 and 5, the cam engagement shaft 46 is engaged with the closed groove 52 of the cam engagement groove 49, and along with this, the pivot shaft 39 and The lead 36 is rotated toward the cylindrical body 31 side via the boss portion 41 and the like to move the valve hole 3
5 is closed. In the above case, the pivot shaft 39 and the cam engagement shaft 46 are brought close to each other, and the inertia moments of the nut portion 44, the bolt 45, and the cam engagement shaft 46 around the pivot shaft 39 are suppressed to be small. .

On the other hand, in the state shown by the chain double-dashed line in FIG. 1 and the chain double-dashed line in FIG. 5, the cam engaging groove 4 is formed in the cam engaging shaft 46.
9 engages with the open groove 53, and accordingly, the lead 36 is rotated through the pivot shaft 39, the boss portion 41, and the like to move the valve hole 35.
Is open. When the interlocking shaft 47 rotates in conjunction with the crankshaft 3 (arrow R), the solid line in FIG.
As indicated by the alternate long and short dash line and the alternate long and two short dashes line, the cam engaging shaft 46
On the other hand, the cam engaging groove 49 moves forward to engage with the cam. That is, the closed groove 5 of the cam engaging groove 49 is attached to the cam engaging shaft 46.
2, the opening groove 55, the opening groove 53, and the closing groove 54 are sequentially cam-engaged, and the closing and opening operations of the lead 36 are repeated.

Next, the operation of the above configuration will be described with reference to all drawings. When the piston 7 moves from the state shown in FIG. 2 toward the cylinder head 5 side in the cylinder 4, the suction and compression strokes are performed. In this process, the open groove 53 is cam-engaged with the cam engaging shaft 46 as shown by the two-dot chain line in FIGS. 5 and 6, and the lead 36 is opened as shown by the phantom line in FIG. The intake air 29 containing the fuel supplied from the carburetor 15 is sucked into the crank chamber 2a through the opened valve hole 35.

At the same time, the intake air 29 previously sucked into the combustion chamber 9 is compressed. In this case,
As shown by, the scavenging passage 17 and the exhaust passage 19 are sequentially closed by the piston 7 immediately after the lead 36 is opened in both the low and high speed regions.

Next, when the piston 7 moves to the side of the crank chamber 2a, it is an explosion and a scavenging stroke. In this stroke, the spark plug is discharged and the intake air 29 in the combustion chamber 9 is discharged.
Are combusted, and the piston 7 is pushed back to the crank chamber 2a side.

Further, in this process, as shown by the solid line in FIGS. 5 and 6, the closed groove 52 is cam-engaged with the cam engaging shaft 46, and the lead 36 is shown by the solid line in FIGS. 1 to 4. Is closed and the valve hole 35 is closed. Therefore, the intake air 29 is prevented from being trapped in the crank chamber 2a and blown back through the intake port 12, whereby the intake air 29 is sufficiently precompressed in the crank chamber 2a.

Further, in this process, as shown in FIG. 7, the exhaust passage 19 is opened by the piston 7, and the combustion gas due to the combustion is discharged through the exhaust passage 19. Next, when the piston 7 further moves to the crank chamber 2a side, the scavenging passage 17 is opened, and the intake air 29 pre-compressed in the crank chamber 2a as described above is transferred to the scavenging passage 1
It is made to flow into the combustion chamber 9 through 7.

Then, a part of the combustion gas remaining here is discharged through the exhaust passage 19 and the combustion chamber 9 is filled with the intake air 29. From here, the piston 7 moves to the cylinder head 5 side again, and the above process is repeated thereafter, so that the engine 1 outputs power.

In the alternate long and short dash line in FIG. 5 and in FIG.
In the high speed range of the engine 1, when the stroke is changed from one of the two strokes to the other, the negative pressure of the crank chamber 2a fluctuates rapidly, so that the opening and closing operations of the lead 36 cannot follow this quickly, that is, the lead 36 The opening and closing operations of are prone to delay. Therefore, only the negative pressure of the crank chamber 2a leads to the lead 36.
When the opening operation is performed, the opening operation groove 5 of the cam engagement groove 49 is formed on the cam engagement shaft 46 at a predetermined crank angle before the opening operation.
5 is cam-engaged to forcefully open the lead 36 early.

As described above, since the groove width of the opening operation groove 55 is sufficiently larger than the diameter dimension of the cam engaging shaft 46, when the opening operation groove 55 is aligned with the cam engaging shaft 46, the cam engaging shaft 46 is engaged. The shaft 46 can freely move left and right within the left and right groove width of the opening movement groove 55. That is, this range is a range in which the opening / closing operation of the lead 36 is released to some extent from the control by the interlocking means 38 (hereinafter, referred to as a release range).
Has become.

In the low-speed range in FIG. 7 and the alternate long and short dash line in FIG. 6, when the lead 36 is opened only by the negative pressure of the crank chamber 2a, it is positioned in the release range. That is, as indicated by the one-dot chain line in FIG. 6 above, before the opening operation groove 55 is cam-engaged with the cam engagement shaft 46, that is, non-forced, by the negative pressure of the crank chamber 2a, the crank angle is changed from the crank angle. As a result, the lead 36 is opened with good timing. In the above case, the lead 36 is connected to the pivot shaft 39.
Since it is freely rotated around, the opening operation is performed accurately and quickly in response to the negative pressure in the crank chamber 2a.

On the other hand, since the lead 36 is pivotally supported by the pivot shaft 39, and this closing operation does not have the elastic restoring force unlike the conventional lead, when the explosion and the scavenging stroke are performed, As shown in FIG. 7, the fact that the lead 36 closes due to the pressure increase in the crank chamber 2a tends to be delayed in both the high and low speed regions in combination with the fact that the restoring force does not work. , Especially in the high speed range.

Therefore, the closing operation groove 54 and the closing groove 52 of the cam engaging groove 49 are formed on the cam engaging shaft 46 at a predetermined crank angle before the lead 36 is closed only by the pressure increase in the crank chamber 2a. Sequentially engage the cams so that there is no play,
The lead 36 is forcibly closed earlier. Even if the lead 36 is closed earlier as described above, if the lead 36 is easily bent, the negative pressure remaining in the crank chamber 2a causes the lead 3 to move.
6 will be greatly opened. Therefore, the lead 36 is made slightly less flexible (the spring constant is made slightly larger) than the conventional lead whose one end is fixed to the valve body.
The interlocking means 38 is operated so that the reed 36 closes slightly before the conventional reed closes due to the pressure increase in the crank chamber 2a. In this way, the reed 36 is closed. The delay is surely prevented.

In the above structure, the cam engaging groove 49 is engaged with the cam engaging shaft 46 in order to set the timing of opening and closing the lead 36, and these two are relatively engaged. Slides while being pressed against each other, but in this case,
Since the opening / closing operation of the lead 36 is basically performed by the pressure in the crank chamber 2a, the cam engagement of the cam engaging shaft 46 and the cam engaging groove 49 for opening / closing the lead 36 is auxiliary. Therefore, the pressure contact force between them is small.

In the above case, when the interlocking means 38 opens the lead 36, the lead 36 is correspondingly opened.
Is less likely to throttle the valve hole 35.
The resistance of the intake air 29 passing through is reduced, the intake air 29 smoothly flows into the crank chamber 2a through the reed valve 13, and the intake efficiency is improved.

Although the above is based on the illustrated example, a pair of upper and lower interlocking shafts 47 and cam engaging shafts 46 of the interlocking device 38 may be provided.
It is prevented that the lead 36 is twisted when the 6 is opened and closed. Further, the interlocking shaft 47 may be directly connected to the crankshaft 3 without the balancer shaft 20.

[0036]

According to the present invention, a reed valve is provided in the intake port of the crankcase, and the reed valve has a valve hole and is attached to the crankcase side.
When the reed is attached to the valve body so as to open and close the valve hole, interlocking means for interlocking the reed with the crankshaft to open and close is provided. It is designed to be closed at the corner. Therefore, the reed closing operation is prevented from being delayed in the high speed range, and the reed closing operation is performed in a timely manner when shifting from the suction stroke, the compression stroke to the explosion stroke and the scavenging stroke. Is prevented from being blown back, and the suction efficiency can be improved, that is, the engine performance is improved.

[Brief description of drawings]

FIG. 1 is a plan sectional view of what is shown in FIG.

FIG. 2 is an overall side sectional view of the engine.

FIG. 3 is a partially enlarged view of FIG.

FIG. 4 is a perspective development view of the interlocking device.

FIG. 5 is a diagram showing a cam engagement groove developed on a plane.

FIG. 6 is a diagram showing a cam engagement groove developed on a plane.

FIG. 7 is a diagram showing a relationship between a crank angle and an operation of a reed valve.

[Explanation of symbols]

 1 engine 2 crankcase 2a crank chamber 3 crankshaft 12 intake port 13 reed valve 29 intake 30 valve body 35 valve hole 36 reed 38 interlocking means 46 cam engagement shaft 49 cam engagement groove

Claims (1)

[Claims] 1. An intake port communicating with the crank chamber from the outside of the crankcase is provided, and a reed valve for allowing intake air to flow only toward the crank chamber is provided in the intake port. An intake device for a precompression type two-cycle engine, which comprises a valve body that is attached to the crankcase side and an elastic lead that is attached to the valve body and that can open and close the valve hole. An intake device for a pre-compression type two-cycle engine in which interlocking means for interlocking with a crankshaft to open and close is provided, and the interlocking means causes the reed to close at a predetermined crank angle.