JP2979391B2 - Rotary valve type two-stroke engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stroke engine mounted on a motorcycle or the like, and more particularly, to a rotary valve type two-stroke engine in which an intake port from a carburetor is opened and closed by a disk-shaped rotary valve. .

[0002]

2. Description of the Related Art Conventionally, as a rotary valve type two-stroke engine of this type, for example, as shown in FIG. 6, a crankshaft 9 of a crank 1 connected to a piston 2 is supported to accommodate the crank 1. A crankcase 10 having an intake port 16 for sucking an air-fuel mixture from a carburetor (not shown) into a crank chamber 11 containing the crank 1, and an outside of the crankcase 10 where the intake port 16 is provided. A substantially semi-circular disk-shaped rotary valve 20 that is provided and rotated by the crankshaft 9 to open and close the intake port 16 at a predetermined timing; and a rotary valve 20 that is provided on the outside of the crankcase 10 where the intake port 16 is provided. And has an inlet 32 for the air-fuel mixture from the carburetor corresponding to the intake port 16 and covers the rotary valve 20. Rubukaba has 30 that a, outer surface 33 and the crankcase 10 and the valve cover 3 is formed with a plane which faces the inner surface 34 to the rotary valve surface 20a of the valve cover 30 of the crankcase 10
0 constitutes a valve storage space 35 for storing the rotary valve 20. And the rotary valve 20
The opening and closing timing of the intake port 16 is made substantially asymmetrical with respect to the top dead center of the piston 2, and the intake port 16 is closed during a predetermined period immediately before reaching the bottom dead center and past the bottom dead center to perform combustion and scavenging. Is performed smoothly.

[0003]

By the way, in this conventional rotary valve type two-cycle engine, during the period when the rotary valve 20 closes the intake port 16,
When the pressure in the crank chamber 11 becomes higher than that on the carburetor side, the rotary valve 20 is pushed toward the valve cover 30 via the intake port 16, so that the rotary valve surface 20 a and the inner surface 34 of the valve cover 30 slide. Since the resistance is increased and the torque cross of the crankshaft 9 is generated correspondingly and the output efficiency is impaired, there is a demand to reduce the torque cross as much as possible. In addition, when the sliding resistance between the rotary valve surface 20a and the inner surface 34 of the valve cover 30 increases, the valve cover 30 easily wears, and particularly easily wears around the inlet 32 around the rotary direction of the rotary valve 20. Since the rotary valve 20 itself is also easily worn, the wear progresses faster and the durability is impaired. Therefore, there is a demand to suppress the progress of wear as much as possible.

[0004] In particular, taking a motorcycle as an example, a general-purpose vehicle running in an urban area does not cause much problem, but the engine speed exceeds 1300 RPM.
In a competition engine that reaches 00 RPM, even if the progress of the torque loss or wear is slight, the influence is great, and it is sought to reduce the torque loss even if it is slight and to suppress the progress of wear. SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and reduces the sliding resistance between the rotary valve surface and the inner surface of the valve cover, increases the engine output torque, improves the output efficiency, and reduces the wear. The object of the present invention is to provide a rotary valve type two-cycle engine in which durability is improved by suppressing the progress of the engine.

[0005]

The technical means of the present invention for solving such a problem is to support a crankshaft of a crank connected to a piston to accommodate the crank and mix the crank from a carburetor. A crankcase having an intake port for sucking air into a crank chamber containing the crank; and a crankcase provided at an outside of the crankcase where the intake port is provided and rotated by a crankshaft. A disk-shaped rotary valve that opens and closes, and an inlet for air-fuel mixture from the carburetor that is provided outside the crankcase and provided with an intake port and that is opened and closed by the rotary valve and that corresponds to the intake port. A valve cover for covering the rotary valve, wherein an outer surface of the crankcase and an inner surface of the valve cover are provided. A rotary valve type two-stroke engine formed by a flat surface facing the rotary valve surface and comprising a valve housing space for housing the rotary valve by the crankcase and the valve cover, on the inner surface side of the valve cover and around the inlet. A concave portion facing the rotary valve surface is provided, and one end is opened to the crank chamber side and the other end is opened to the concave portion to form a communication passage communicating the crank chamber and the concave portion. I have.

With this configuration, during the period in which the rotary valve closes the intake port, the pressure in the crank chamber becomes higher than that of the carburetor, and even if the rotary valve is pushed toward the valve cover through the intake port. Since the gas in the crank chamber reaches the recess through the communication passage, the pressure of the gas that has reached the recess generates a force on the rotary valve toward the crankcase, causing the rotary valve to float, and It will be pushed back to the case side. Therefore, sliding resistance between the rotary valve and the inner surface of the valve cover is reduced. As a result, the torque loss of the crankshaft is reduced, and the output efficiency is greatly improved. Further, the valve cover and the rotary valve are less likely to be worn, so that the progress of the wear is slowed and the durability is greatly improved.

[0007] If necessary, the recess is provided before and after the rotary direction of the rotary valve at the inlet. Around the entrance opposed to the intake port, a force to the crankcase side can be generated in a portion where the influence of the pressure from the intake port side is large, so that the rotary valve is reliably pushed back to the crankcase side, and The sliding resistance between the rotary valve and the inner surface of the valve cover is reliably reduced. Further, if necessary, the recess is provided in the vicinity of the inlet so that gas in the recess can leak to the inlet. The leaking gas causes the rotary valve to further float, so that the sliding resistance between the rotary valve and the inner surface of the valve cover is further reduced. Further, if necessary, the recess area S _{0 of the} above-mentioned recess is provided.
And the intake port area S _K of the intake port is set to S ₀ = S _K or S ₀ ≒ S _K. Since the area on which the pressure of the gas acts is substantially the same on the left and right, the force due to the pressure of the gas flowing from the communication passage acts on the rotary valve almost in the same manner as the force from the intake port side to maintain the balance.

Further, if necessary, the valve cover is formed with a housing space for housing the crankshaft of the valve housing space, and the communication passage is formed on the crankshaft with the crank chamber and the housing space. And a cover through-hole formed in the valve cover and communicating with the enclosing space and the recess. The communication path may be formed at any position, but this configuration makes the processing simple and easy to manufacture. Further, if necessary, the valve cover is formed with a housing space portion for housing a mounting portion of the valve housing space to the crankshaft of the rotary valve, and the communication path is formed in the mounting portion of the valve cover and the crank chamber is formed. And a valve through hole communicating with the housing space, and a cover through hole formed in the valve cover and communicating with the housing space and the recess. Also in this case, the processing is simple and the manufacturing is easily performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rotary valve type two-stroke engine according to an embodiment of the present invention will be described below with reference to the accompanying drawings. Note that the same components as described above are denoted by the same reference numerals and described. As shown in FIGS. 1 to 4, in a rotary valve type two-cycle engine according to an embodiment of the present invention, reference numeral 1 denotes a crank connected to a piston 2 reciprocating a cylinder 3. The crank 1 is connected to a pair of disks 5 constituting a crank arm 4, a crank pin 6 erected between the disks 5 at a position eccentric to the axis of the disk 5, a shaft 2 supported by the crank pins 6, and connected to the piston 2. And a connecting rod 7. Each disk 5 has first and second crankshafts 8, 9 coaxial with the center axis of the disk 5.
Is provided. Each of the crankshafts 8 and 9 has a large diameter portion 8.
a, 9a and small diameter portions 8b, 9b. The first crankshaft 8 is configured as an output shaft for taking out an output, and is connected to a mechanism on the output side.

Reference numeral 10 denotes a crank chamber 1 for accommodating the crank 1.
1, which supports first and second crankshafts 8 and 9 of the crank 1 via ball bearings 12. The ball bearing 12 is fitted on the large diameter portions 8a, 9a of the first and second crankshafts 8,9. A ball bearing 12 is provided in the crankcase 10.
Are formed, and a through hole 14 into which the small diameter portions 8b and 9b are loosely inserted is formed. The crankcase 10 has a bearing hole 1 of the second crankshaft 9.
An intake port 16 is provided above the carburetor 3 and is used to suck the air-fuel mixture from the carburetor 15 into the crank chamber 11.

Reference numeral 20 denotes a rotary valve, which is provided outside the intake port 16 of the crankcase 10 and is rotated by the second crankshaft 9 to open and close the intake port 16 at a predetermined timing. The rotary valve 20 is formed in a substantially semicircular disk shape in which a predetermined angular range of a metal disk is cut out, and a center portion is attached to a small diameter portion 9b of the second crankshaft 9 via a collar 21 as an attachment portion. . The collar 21 has inner and outer protruding portions 22 and 23 protruding forward and backward in the axial direction, and is prevented from rotating with respect to the small diameter portion 9 b of the second crankshaft 9 via the key 24. The inner protruding portion 22 is the insertion hole 1 of the crankcase 10.
4 is loosely inserted. The opening / closing timing of the intake port 16 by the rotary valve 20 is set substantially asymmetrically with respect to the top dead center of the piston 2, and the intake port 16 is closed during a predetermined period immediately before reaching the bottom dead center and past the bottom dead center. It is set as follows.

Numeral 30 denotes a valve cover for covering the rotary valve 20, and a bolt 31 is provided on the outside of the crankcase 10 where the intake port 16 is provided via a packing (not shown).
It is fixed at. The valve cover 30 is provided with an inlet 32 which is opened and closed by the rotary valve 20 and is opened at a position corresponding to the intake port 16 and through which a mixture from the carburetor 15 passes. The outer surface 33 of the crankcase 10 facing the rotary valve surface 20a and the inner surface 34 of the valve cover 30 are formed by a plane parallel to the rotary valve surface 20a. A valve storage space 35 for storing the valve 20 is formed. The rotary valve surface 20a, the outer surface 33 of the crankcase 10, and the inner surface 34 of the valve cover 30 are slidable with each other. Further, the valve cover 30 is formed with an enclosing space 36 that encloses the small-diameter portion 9 b of the second crankshaft 9 protruding toward the valve cover 30 and the outer protruding portion 23 of the collar 21.

Further, a recess 40 facing the rotary valve surface 20a is provided on the inner side surface 34 of the valve cover 30 and around the inlet 32. In addition, a communication path 50 that opens one end to the crank chamber 11 and the other end to the recess 40 to communicate the crank chamber 11 and the recess 40 is formed. A pair of recesses 40 are provided in the front and rear direction of the rotary direction of the rotary valve 20 at the inlet 32. Also, the recess 40 is
As shown in FIG. 3, it is formed in a substantially oval shape, and is provided near the inlet 32 so that the gas in the recess 40 can leak to the inlet 32 side. That is, the distances D ₁ and D ₂ between the inner surface 34 of the recess 40 and the inlet 32 are appropriately determined so that the gas in the recess 40 can leak to the inlet 32 side.
Furthermore, the total recess area S ₀ of the recess 40 (S ₀ = S ₁ +
S ₂ ) and the intake port area S _K of the intake port 16 are given by S ₀ =
It is determined that S _K or S ₀定 め S _K. As a result, since the areas are the same or substantially the same,
The force caused by the gas flowing from the inlet acts on the rotary valve 20 in substantially the same manner as the force on the intake port 16 side to maintain balance.

A communication passage 50 is formed in the second crankshaft 9 and communicates with the crank chamber 11 and the housing space 36. The communication passage 50 is formed in the valve cover 30 and the housing space 36.
And a cover through-hole 52 communicating with the recess 40. The shaft through-hole 51 is formed coaxially with the axis of the second crankshaft 9. Thereby, the communication path 50 is
The shaft through hole 51, the housing space 36, and the cover through hole 52 are formed. One end of the shaft through hole 51 is open to the crank chamber 11, and the other end of the cover through hole 52 is open to the recess 40, and the crank chamber 11 is open. And the recess 40 are communicated.

Therefore, according to the rotary valve type two-cycle engine according to this embodiment, the reciprocating motion of the piston 2 is converted into the rotational motion of the first and second crankshafts 8 and 9, and The output is obtained. On the other hand, the rotation of the second crankshaft 9 causes the rotary valve 20 to rotate.
2 is opened and closed, and the air-fuel mixture from the carburetor 15 is sucked into the crank chamber 11 at a required timing. In this case, the intake port 16 is closed during a predetermined period immediately before the piston 2 reaches the bottom dead center and passes the bottom dead center, so that combustion and scavenging are performed smoothly.

As shown in FIG. 4, during a period in which the rotary valve 20 closes the intake port 16, the pressure P in the crank chamber 11 becomes higher than that of the carburetor 15, and
Although the rotary valve 20 is about to be pushed toward the valve cover 30 through the intake port 16, the gas in the crank chamber 11 reaches the recess 40 through the communication passage 50, and thus reaches the recess 40. Due to the pressure of the gas, a force is applied to the rotary valve 20 from the valve cover 30 side to the crankcase 10 side, so that the rotary valve 20 floats and is pushed back to the crankcase 10 side. Sliding resistance between the valve and the inner surface 34 of the valve cover 30 is reduced. In this case, the recess 40 is
Around the inlet 32, which is provided before and after the inlet 32 in the rotation direction of the rotary valve 20 at the inlet 32.
The crankcase 10
Side, and the rotary valve 20 can be reliably pushed back to the crankcase 10 side, so that the sliding resistance between the rotary valve 20 and the inner surface 34 of the valve cover 30 can be reduced. Is reliably reduced.

Further, in this case, the total recess area S ₀ of the recess 40 (S ₀ = S ₁ + S ₂ ) and the intake port area S _K of the intake port 16 are calculated as S ₀ = S _K or S ₀ ≒. Since the pressure is determined to be S _K , the area on which the gas pressure acts is substantially the same on the left and right, so that the force due to the pressure of the gas flowing from the communication passage 50 is substantially the same as the force from the intake port 16 side. The balance is maintained by acting on the rotary valve 20. for that reason,
The outer surface 3 of the crankcase 10 is
3 and the inner surface 34 of the valve cover 30 rotate at the neutral position, and the sliding resistance is further reduced. Further, the distance D of the inner surface 34 between the recess 40 and the entrance 32
_{Since 1} and D ₂ are defined so that the gas in the recess 40 can leak to the inlet 32 side, the leaking gas causes the rotary valve 20 to float further, and therefore,
The sliding resistance between the rotary valve 20 and the inner surface 34 of the valve cover 30 is reduced.

As described above, during the period when the rotary valve 20 closes the intake port 16, the rotary valve 20 is closed.
The sliding resistance between the first and second crankshafts 8 and 9 is reduced, and the output efficiency is greatly improved. In addition, the rotary valve surface 20a and the valve cover 30
Since the sliding resistance with respect to the inner side surface 34 is reduced, the valve cover 30 is less likely to be worn, and in particular, the wear of the inlet 32 before and after the rotary direction of the rotary valve 20 is reliably prevented. Further, the rotary valve 20 itself is hardly worn. Therefore, the progress of wear is slowed, and the durability is greatly improved.

FIG. 5 shows another example of the communication passage 50 of the rotary valve type two-cycle engine according to the embodiment. The communication passage 50 is formed in the collar 21 as a mounting portion of the valve cover 30, and communicates with the crank chamber 11 and the housing space 36. The valve through hole 53 is formed in the valve cover 30, and the housing space 36 and the recess 40 are formed. And a cover through-hole 52 similar to the above. Thereby, the communication passage 50 is formed by the valve through hole 53, the enclosing space 36, and the cover through hole 52, and one end of the valve through hole 53 opens to the crank chamber 11 through the gap of the ball bearing 12, and the cover through hole 52. The other end opens into the recess 40 to communicate the crankcase 11 with the recess 40. Therefore, the same operation and effect as described above are also provided by the communication passage 50.

In the above embodiment, the communication path 50
May have both the shaft through hole 51 and the valve through hole 53, and may be changed as appropriate. Further, the formation site of the communication passage 50 is not limited to the above-described one, and may be appropriately changed. Further, the shape, size and number of the recesses 40 and the formation sites in the valve cover 30 are not limited to those described above, and may be changed as appropriate. In particular, the relationship between the total recess area S ₀ of the recess 40 and the intake port area S _K of the intake port 16 is not limited to the above,
Preferably, S ₀ = S _K or S ₀ ≒ S _K ,
It is desirable that S ₀ ≧ S _K. This is a result obtained from repeated experiments. A higher torque on the side of the recess 40 resulted in a higher torque. In addition, the present invention
Of course, the present invention can be similarly applied to an engine of a type in which the rotary valve 20 is provided on the crankshaft 8 side as an output shaft.

[0021]

As described above, according to the rotary valve type two-stroke engine of the present invention, the concave portion facing the rotary valve surface is provided on the inner surface side of the valve cover and around the inlet to provide the crank chamber. During the period in which the rotary valve closes the intake port, the pressure in the crank chamber becomes higher than that of the carburetor, and the rotary valve is connected to the valve cover via the intake port. The gas in the crank chamber reaches the recess through the communication passage even if it is pushed to the side, and the pressure of the gas that has reached the recess causes the rotary valve to generate a force to the crankcase side to rotate. The valve can be floated and pushed back to the crankcase side, thereby reducing the sliding resistance between the rotary valve and the inner surface of the valve cover. It can be.

As a result, the torque loss of the crankshaft can be reduced, the output efficiency can be greatly improved, and the valve cover and the rotary valve can be hardly abraded. Durability can be greatly improved. In particular, in the case of a racing engine (competition engine) in which the number of revolutions of the engine exceeds 1300 RPM and reaches 21,000 RPM, even if the reduction of the torque loss and the progress of wear are slight, the performance of the engine is significantly improved. Will cause
Therefore, in the present invention, the reduction of the torque loss and the reduction of the progress of wear can be significantly improved, which is extremely useful.

In the case where the recess is provided before and after the rotary direction of the rotary valve at the inlet, the portion around the inlet facing the intake port, which is greatly affected by the pressure from the intake port side, is moved toward the crankcase side. Can produce the power of
Therefore, the rotary valve can be reliably pushed back to the crankcase side, so that the sliding resistance between the rotary valve and the inner surface of the valve cover can be reliably reduced. Further, when the recess is provided near the inlet so that the gas in the recess can leak to the inlet side, the leaking gas further floats the rotary valve, and therefore, the rotary valve is further increased. The sliding resistance between the valve and the inner surface of the valve cover can be reduced.

When the recess area S ₀ of the recess and the intake port area S _K of the intake port are set to S ₀ = S _K or S ₀ ≒ S _K , the area on which the gas acts on the left and right Therefore, the force due to the pressure of the gas flowing from the communication passage acts on the rotary valve almost in the same manner as the force from the intake port side to maintain the balance, so that the rotary valve is connected to the outer surface of the crankcase. And the inner surface of the valve cover rotates at a neutral position, so that sliding resistance can be further reduced.

Further, an enclosing space for enclosing the crankshaft of the valve accommodating space is formed in the valve cover, and the communication passage is formed in the shaft through hole formed in the crankshaft and communicating with the crank chamber and the enclosing space, and in the valve cover. In the case of being provided with the cover through-hole formed and communicated with the enclosing space and the recess, there is an effect that the processing is simple and the manufacturing can be facilitated. Still further, a valve space is formed in the valve cover to accommodate a mounting portion of the valve storage space to the crankshaft of the rotary valve, and the communication path is formed in the mounting portion of the valve cover and communicates with the crank chamber and the housing space. Also in the case of including the through-hole and the cover through-hole formed in the valve cover and communicating with the enclosing space and the recess, there is an effect that the processing is simple and the manufacturing can be facilitated.

[Brief description of the drawings]

FIG. 1 shows a rotary valve type 2 according to an embodiment of the present invention.
It is sectional drawing which shows a cycle engine.

FIG. 2 is a rotary valve type 2 according to the embodiment of the present invention.
FIG. 2 is an exploded perspective view showing a cycle engine.

FIG. 3 is a rotary valve type 2 according to the embodiment of the present invention.
It is a front view showing the valve cover of the cycle engine.

FIG. 4 is a rotary valve type 2 according to the embodiment of the present invention.
FIG. 2 is an enlarged sectional view of a main part of the cycle engine.

FIG. 5 is a rotary valve type 2 according to the embodiment of the present invention.
FIG. 9 is a cross-sectional view of a main part showing another example of the communication path of the cycle engine.

FIG. 6 is an exploded perspective view showing an example of a conventional rotary valve type two-cycle engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Crank 2 Piston 3 Cylinder 4 Crank arm 5 Disk 6 Crank pin 7 Connecting rod 8 First crankshaft 8a Large diameter portion 8b Small diameter portion 9 Second crankshaft 9a Large diameter portion 9b Small diameter portion 10 Crankcase 11 Crankcase 12 Ball bearing 13 Bearing hole 14 Insertion hole 15 Carburetor 16 Intake port 20 Rotary valve 20a Rotary valve surface 21 Collar 22 Inside protrusion 23 Outside protrusion 24 Key 30 Valve cover 32 Inlet 33 Outer surface 34 Inner surface 35 Valve storage space 40 Recess D ₁ , D ₂ interval S ₀ recess area (S ₀ = S ₁ + S ₂ ) S _K intake area 50 communication passage 51 shaft through hole 52 cover through hole 53 valve through hole

Claims (6)

(57) [Claims] 1. A crankcase having a suction port for supporting a crankshaft of a crank connected to a piston for accommodating the crank and sucking an air-fuel mixture from a carburetor into a crank chamber accommodating the crank. When,
A disk-shaped rotary valve provided on the outside of the crankcase where the intake port is provided and rotated by a crankshaft to open and close the intake port at a predetermined timing; and provided on the outside of the crankcase where the intake port is provided. A valve cover that covers the rotary valve with an inlet for air-fuel mixture from the carburetor that is opened and closed by the rotary valve and that corresponds to the intake port, and covers an outer surface of the crankcase and an inner surface of the valve cover. A rotary valve type 2 formed by a plane facing the rotary valve surface and comprising a valve housing space for housing the rotary valve by the crankcase and the valve cover.
In the cycle engine, a concave portion facing the rotary valve surface is provided around the inlet on the inner surface side of the valve cover, and one end is opened to the crank chamber side and the other end is opened to the concave portion. A rotary valve type two-stroke engine, wherein a communication passage communicating the crank chamber and the recess is formed. 2. The rotary valve type two-stroke engine according to claim 1, wherein the recess is provided before and after the rotary direction of the rotary valve at the inlet. 3. The rotary valve type two-stroke engine according to claim 2, wherein the recess is provided near the inlet so that gas in the recess can leak to the inlet. 4. The method according to claim 2, wherein the recess area S ₀ of the recess and the suction port area S _K of the suction port are set to S ₀ = S _K or S ₀ ≒ S _K. 3. The rotary valve type two-stroke engine according to 3. 5. A valve housing, wherein a housing space for housing a crankshaft of the valve housing space is formed in the valve cover, and the communication passage is formed in the crankshaft and communicates with the crank chamber and the housing space through a shaft. The rotary valve type two-cycle according to claim 1, 2, 3, or 4, further comprising a hole and a cover through-hole formed in the valve cover and communicating with the housing space and the recess. engine. 6. The valve cover has a receiving space formed therein for receiving a mounting portion of the valve storage space for the rotary valve with respect to the crankshaft, and the communication passage is formed in the mounting portion of the valve cover. 3. The valve according to claim 1, further comprising: a valve through hole communicating with the housing space, and a cover through hole formed in the valve cover and communicating with the housing space and the recess.
A rotary valve type two-stroke engine according to 3 or 4.