JPH063145Y2 - Two-cycle engine with exhaust timing control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention is directed to opening and closing the upper part of the exhaust port on the inner wall of the exhaust passage that is continuous with the exhaust port opening on the inner surface of the cylinder. The present invention relates to a two-cycle engine equipped with an exhaust timing control device in which a control valve for swinging a control valve that changes the upper edge in the sliding direction of a piston fitted in the cylinder is provided, and particularly when casting a cylinder. The present invention relates to a two-cycle engine in which a cylindrical sleeve is integrally fitted to form a sliding surface of the piston.

"Prior Art" Generally, engines installed in vehicles are roughly divided into a low rotation type that emphasizes power characteristics in a low rotation range and a high rotation type that emphasizes power characteristics in a high rotation range. It is divided into two parts, the former allows the peak of the engine output to be obtained in the low revolution range, and the latter allows the peak of the engine output to be obtained in the high revolution range.

However, the former has a characteristic that the output in the high speed range reaches a peak, and the latter has the characteristic that the output in the low speed range becomes lower than that of the former. Therefore, it is considered to improve the output characteristics in the entire rotation range from the low rotation range to the high rotation range by increasing the output in the low rotation range while maintaining the high output in the high rotation range.

As one specific means for solving the problem, it is mentioned that the engine exhaust timing is changed between the low speed region and the high speed region. However, when this means is not applied to the 2-cycle engine, the exhaust gas in the 2-cycle engine However, in order to change the exhaust timing, it is necessary to change the upper edge of this exhaust port (that is, the edge at the top dead center of the piston) in the sliding direction of the piston in order to change the exhaust timing. There is.

Therefore, the applicant of the present application has proposed the structure shown in FIGS. 1 and 2 as one means for changing the upper edge of the exhaust port in the above-described two-cycle engine.

As shown in FIG. 1, this proposal proposes an upper part of an exhaust passage 2 formed in a cylinder 1 (hereinafter, the upper side means a top dead center side of a piston, and the lower side means a bottom dead center side of a piston). The exhaust passage 2 is provided in the vicinity of the exhaust port 2a which is an opening of the exhaust passage 2 to the inner surface of the cylinder 1.
A shaft 3 is rotatably provided so as to be orthogonal to the length direction of the control valve, and one end of a control valve 4 for opening and closing the upper portion of the exhaust port 2a is fixed to the shaft 3, 4 is swingably supported, and a recess 5 as a housing portion for housing the shaft 3 and the control valve 4 is formed in the upper wall of the exhaust passage 2 facing the control valve 4, and the second As shown in the figure, one end of the shaft 3 is projected to the outside of the cylinder 1, and the end of the protruding side is rotated, so that the control valve 4 attached to the shaft 3 is rotated. The drive mechanism 6 for swinging the is mounted.

And when the engine is running at low speed,
By swinging the control valve 4 in the direction in which it projects from the recess 5 and closing the upper portion of the exhaust port 2a by the swing-side end of the control valve 4 as shown by the solid line in FIG.
By apparently moving the upper edge 2b of the exhaust port 2a to the lower edge 4a of the swinging end of the control valve 4, the lower edge 4a of the control valve 4 and the upper edge 2b of the exhaust port 2a are separated. The opening timing of the exhaust port 2a, that is, the exhaust timing due to the lowering of the piston 7 is delayed by the distance L, and when the engine speed reaches the high speed range, the control valve 4 is reversed from the direction described above. While swinging in the direction, the upper portion of the exhaust port 2a is opened by advancing the exhaust timing by accommodating the recess 5 as shown by the chain line in FIG. The exhaust characteristics are optimized and the output characteristics are improved.

This is due to the pulsation of pressure generated in the exhaust passage 2 during exhaust,
By controlling the opening / closing timing of the exhaust port 2a, the pressure in the vicinity of the exhaust port 2a is increased immediately before the exhaust port 2a is closed, and thereby the amount of air-fuel mixture blown from the exhaust port 2a into the exhaust passage 2 is reduced. This is because the charging efficiency of the air-fuel mixture can be improved.

[Problems to be Solved by the Invention] In the exhaust timing control device having the above-described configuration, the control valve 4 is swung in the direction in which it projects into the exhaust passage 2 from the recess 5, and Although the exhaust point is set to be delayed by setting the exhaust start point by the edge 4a, the control valve 4 is projected so that the hollow between the recessed portion 5 in the hollow state and the inside of the cylinder 1 is not blocked. If it is sufficient, the combustion gas in the cylinder 1 is discharged to the exhaust passage 2 through the recess 5 before reaching the above-mentioned regular exhaust start point, and the exhaust timing control accuracy may be increased depending on the amount of this exhaust amount. There is a possibility that it will decrease, and in order to suppress this, it is necessary to narrow the gap between the control valve 4 and the inner wall surface of the recess 5 as much as possible and to set the size of the gap with high precision.

However, when the smoothness of the inner wall surface of the recess 5 is increased by post-processing, the recess 5 is located at the deepest position in the exhaust passage 2 and the exhaust passage 2 is gradually narrowed as it goes upstream. Due to the rough shape of the inner wall surface of the recess 5, the inner wall surface of the recess 5 and the control valve 4 are difficult to insert because it is difficult to insert a tool for processing and cannot perform sufficient processing. There is still a point to be improved such that the range in which the gap between the rocking end portion and the end surface can be narrowed is limited, or the dimensional control accuracy is limited.

"Means for Solving Problems" The present invention aims to effectively eliminate the points to be improved left in the above-mentioned proposal and further improve the power characteristics, and to achieve this object. The two-cycle engine equipped with the exhaust timing control device according to the present invention is
In particular, an exhaust port is formed in a cylindrical sleeve that is integrally cast in a cylinder, and an exhaust passage that is continuous with the exhaust port is formed in the cylinder. The accommodating portion for accommodating the control valve for making the edge variable is formed such that the joint surface between the cylinder and the sleeve at the upper end of the exhaust passage is a part of the inner wall surface of the accommodating portion. In the above, a step is provided by extending the sleeve below the cylinder by a certain size, and a seal surface is formed continuously with the lower end of the step so as to face the swing-side end surface of the control valve. Characterize.

[Operation] In a two-cycle engine equipped with the exhaust timing control device according to the present invention, the control valve housing is such that the joint surface between the cylinder and the sleeve at the upper end of the exhaust passage is part of the inner wall surface of the housing. By forming the inner wall surface of the accommodating portion where the end surfaces of the swinging end portions of the control valve are opposed to each other, the outer surface of the sleeve can be processed prior to the casting of the cylinder to ensure its smoothness. Further, at the joint surface, by the step provided by extending the sleeve by a certain size below the cylinder, the exudation position of the hot water (that is, molten metal such as aluminum) when the cylinder is cast, The control valve is set at a position separated from the inner wall surface of the accommodating portion opposed to the control valve to prevent the inner wall surface from being roughened at the time of casting and to easily ensure the smoothness thereof.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 3 and 4.

In the following description, parts common to those in FIGS. 1 and 2 are designated by the same reference numerals to simplify the description.

In FIG. 3, reference numeral 10 indicates a two-cycle engine (hereinafter, abbreviated as engine) according to the present embodiment. Recess from the vicinity of 2a toward the downstream side
11 is formed, and the concave portion 11 is used as a housing portion, and
Exhaust provided with a swingable control valve 12 for changing the upper edge 2b of the exhaust port 2a in the sliding direction of the piston 7 fitted in the cylinder 1 by opening and closing the upper part of the exhaust port 2a. A cylindrical sleeve 14 including a timing control device 13, in which the piston 7 is slidably fitted, and a through hole 14a forming the exhaust port 2a is formed.
Is integrally mounted in the cylinder 1 when the cylinder 1 is cast, and constitutes a part of the inner wall surface of the recess 11 on the outer side of the sleeve 14, and the control valve 12 swings. By forming a sealing surface 14b that is opposed to the moving-side end surface 12a, the recess 11 is formed in the cylinder 1
And a sleeve 14 between the joint surfaces X and Y, which is continuous between the joint surfaces X and Y and which is continuous with the upper end of the sealing surface 14b and constitutes a part of the inner wall surface of the recess 11. It has a schematic configuration in which the portion 14c is formed.

Next, these will be described in detail.
In the present embodiment, is the inner peripheral surface of the cylinder 1 (sleeve 14
Inner peripheral surface) and a deep bottom portion 11a formed near
1a and a shallow bottom portion 11b that is formed toward the downstream side of the exhaust passage 2, and the shaft 3 for supporting the control valve 12 penetrates the downstream end portion of the shallow bottom portion 11b. Has been. The control valve 12 is
An upwardly projecting portion 12b is formed at the end on the swing side, and the projecting portion 12b is inserted into the deep bottom portion 11a of the recessed portion 11 in a state where the control valve 12 is accommodated in the recessed portion 11. The end face 12a of the protrusion 12b located on the inner side of the cylinder 1 (that is, the end face on the oscillating side) has an arc shape with the shaft 3 as the center, and is formed on the inner peripheral surface of the cylinder 1. It is formed in a curved shape to follow.

As shown in FIG. 3, the sleeve 14 is formed in a thin-walled cylindrical shape, and a thick-walled portion 15 is formed over the entire circumference in the middle portion in the longitudinal direction thereof. Meat 15
Further, a through hole 14a corresponding to the exhaust passage 2 and forming the exhaust port 2a which is an opening of the exhaust passage 2 into the cylinder 1 is formed along the radial direction of the sleeve 14, and An exhaust port 16a, which is an opening of the scavenging passage 16 into the cylinder 1, is communicated with a scavenging passage 16 formed in the cylinder 1 at a plurality of locations spaced from the through hole 14a in the circumferential direction. The through hole 17 is formed.

As shown in FIGS. 3 and 4, the sealing surface 14b is formed upward from the upper end portion of the through hole 14a, and is similar to the swing-side end surface 12a of the control valve 12. In addition, the control valve 12 has an arcuate surface centering on the shaft 3 and a curved shape along the inner surface of the cylinder 1, that is, the inner surface of the sleeve 14, regardless of the swing position of the control valve 12. The curvatures of the two are set so that a predetermined distance is formed in the weight portion of the rocking side end surface 12a.

On the other hand, the stepped portion 14c is the sleeve 14 in the example of the present invention.
Is formed by the outer surface of the thick wall portion 15, that is, the joint surface Y, and when the cylinder 1 is cast, the joint surface Y is moved from the upper end of the seal surface 14b by a core (not shown) mounted in the mold. It is formed by covering a predetermined distance.

Therefore, after the cylinder 1 is cast, the stepped portion 14c forms a cavity above the protruding portion 12b of the control valve 11 accommodated in the recess 11.

However, the engine 10 of the present embodiment having such a structure
In the peripheral wall of the sleeve 14, through holes 14a and 17 are bored to form an exhaust port 2a and a scavenging port 16a, and then the sealing surface 14b is formed on the upper part of the former through hole 14a and After finishing the surface 14b, the sleeve 14 is installed in the mold, and the exhaust passage 2 and the recess 11 are formed in the mold, and the sleeve 14 located above the sealing surface 14b is formed. Thick part 1
A core that covers a predetermined amount of 5 and a core that forms the scavenging passage 16 and the like are attached, and a molten metal (aluminum or an alloy thereof) is cast around these to solidify the sleeve 14 in the cylinder 1. Fitted in one piece, further, after removing the mold and the core, washed and the like, then,
It is formed by mounting the control valve 12 in the recess 11 and mounting other constituent members to the cylinder 1.

By such casting, the cylinder 1 is integrally formed around the sleeve 14 to form a cylinder block as a whole, and as shown in FIG. 4, a deep bottom portion 11a and a deep bottom portion 11a are formed on the upper wall of the exhaust passage 2. The recess 11 is formed by the shallow bottom 11b continuing from the deep bottom 11a.
A part of the inner wall surface of the cylinder 1 on the inner side of the cylinder 1a is constituted by the sealing surface 14b and the step portion 14c.

Then, at the time of casting described above, since the sealing surface 14b and the stepped portion 14c are covered with the core, these surfaces 14b and 14c are protected from the molten metal to be cast, and the smoothness thereof in the previous step. It is kept in the processed state.

On the other hand, when casting, in order to improve the quality of the product,
Since pressure is applied to the molten metal (molten metal) cast by the molten metal, it is assumed that the molten metal forms a soot just between the contact surfaces of the sleeve 14 and the core. It

However, in this embodiment, as described above,
Since the continuous step portion 14c is formed between the joining surfaces X and Y at the upper end of the seal surface 14b, even if the molten metal soaks, the step portion is formed before the penetration of the molten metal reaches the seal surface 14b. Suppressed by 14c.

Therefore, even if the soaking phenomenon occurs, the sealing surface 14b is protected and its smoothness is maintained.

Here, the stepped portion 14c is located above the protruding portion 12b of the control valve 12, has nothing to do with the sealing characteristic between the control valve 12 and the sleeve 14, and operates the control valve 12 Since it is located outside the range, even if only the molten metal soaks into the stepped portion 14c, the accuracy of the exhaust timing and the operation of the control valve 12 are not affected. Therefore, it is not necessary to perform the removal just described.

In this way, when the sleeve 14 is mounted in the cylinder 1 formed by casting, the rocking side end surface 12 of the control valve 12 is mounted.
The seal surface 14a opposed to a is maintained in a highly accurate processed state and its smoothness is sufficiently ensured, which facilitates the management of the gap between the control valve 12 and the seal surface 14a.

On the other hand, when the engine 10 is operating in the low rotation range, the shaft 3 is rotated by the drive mechanism 6 to swing the control valve 12 and, as shown in FIG.
The end face 12a of the control valve 12 closes the upper part of the exhaust port 2a while projecting the recess 11 into the exhaust passage 2.

At this time, the control valve 12 is stopped at a position where the lower edge 12c of the end face 12a is substantially parallel to the upper edge 2a of the exhaust port 2a.

Such swinging of the control valve 12 causes the exhaust port 2a to
The upper edge 2b is apparently moved to the lower dead center side of the piston 7 up to the lower edge 12c of the end face 12a, and the exhaust timing of the engine 10 is delayed by this moving distance L, so that the exhaust in the low rotation speed range is exhausted. Is done properly.

Further, when the engine 10 reaches a high rotation speed, the drive mechanism 6 causes the control valve 12 to swing in the direction opposite to the above-described direction, and the control valve 12 is housed in the recess 11.

In this way, by housing the control valve 12 in the recess 11, the closed upper part of the exhaust port 2a is opened and the upper edge of the exhaust port 2a is moved to the top dead center side of the piston 7. As a result, the exhaust timing of the engine 10 is advanced by this amount, whereby the exhaust in the high rotation speed range is appropriately performed.

Therefore, appropriate exhaust is performed in the rotation range from the low rotation range to the high rotation range, and the output characteristic is improved in the entire rotation range.

Then, at the time of controlling the exhaust timing as described above, as described above, the sealing surface 14a formed on the sleeve 14 is maintained in a state of being processed with high precision, and the end surface 12a of the control valve 12 is Since the clearance between them is also controlled with high accuracy, the leakage of the combustion gas from the clearance between the two is maintained within the set range, and the reliability and reliability of control are improved.

It should be noted that the shapes, dimensions, and the like of the constituent members shown in the above-described embodiments are merely examples, and can be variously changed based on the type of engine to be applied, design requirements, and the like.

For example, the number of the control valves 12 installed can be arbitrarily set to one or more.

Further, as a driving means for rotating the driving shaft 3, one having a mechanical connection structure such as a wire or a link, or one having a structure directly driven by a fluid pressure actuator or an electric actuator is appropriately used. be able to.

[Advantage of the Invention] As described above, the two-cycle engine including the exhaust timing control device according to the present invention forms the exhaust port in the cylindrical sleeve integrally cast in the cylinder, and An exhaust passage which is continuous with the exhaust port, and an inner wall of the exhaust passage has a housing portion for housing a control valve for varying the upper edge of the exhaust port,
The joint surface between the cylinder and the sleeve at the upper end of the exhaust passage is formed so as to be a part of the inner wall surface of the accommodating portion, and at this joint surface, the sleeve extends below the cylinder by a certain amount. The present invention is characterized in that a step is provided and a seal surface is formed continuously with the lower end of the step so as to face the swing-side end surface of the control valve, and the following excellent effects are achieved.

The inner wall surface of the accommodating portion, to which the end surface of the swinging end portion of the control valve faces, can be finished with high accuracy by processing the outer surface of the sleeve prior to the casting of the cylinder.

When the cylinder is cast around the sleeve, the progress of the penetration of the molten metal is suppressed by the step portion, and the molten metal is prevented from soaking into the inner wall surface of the accommodation portion, whereby the inner wall surface is formed. In addition to preventing the roughening of the internal combustion engine and the effect described above, the gap between the control valve facing the inner wall surface is narrowed as much as possible, and the leakage of combustion gas from the gap between the two is within the allowable range. It can be easily suppressed.

Therefore, the accuracy of control of the exhaust timing can be improved.

Even if the molten metal soak phenomenon occurs at the step, the step is located so as to avoid the protruding portion of the control valve, and the sealing characteristics between the control valve and the inner wall surface of the housing are Since it is positioned outside the operating range of the control valve without any involvement, it does not affect the control accuracy of the exhaust timing or the operation of the control valve.

This eliminates the need to remove the flash described above,
It can be expected to improve productivity.

[Brief description of drawings]

FIGS. 1 and 2 show a two-cycle engine equipped with an exhaust timing control device according to the applicant's previous proposal. FIG. 1 is a longitudinal sectional view with a part omitted, and FIG. 2 is a transverse sectional view. FIGS. 3, 3 and 4 show an embodiment of the present invention. FIG. 3 is a vertical sectional view and FIG. 4 is an enlarged vertical sectional view of a main part. 1 ... Cylinder, 2 ... Exhaust passage, 2a ... Exhaust port, 2b ... Upper edge, 3 ... Shaft, 7 ... Piston, 10 ... (2-cycle) engine, 11 ... Recessed portion (accommodation section) , 11a ... deep bottom, 11b ... shallow bottom, 12 ...... control valve, 12a ... end face, 12b ... projection, 12c ... bottom edge, 13 ... exhaust timing control device, 14 ......... sleeve, 14a … Through hole, 14b… Sealing surface, 14c… Step, 15 …… Thick part, 16… Scavenging passage, 16a… Scavenging port, 17… Through hole, XY… Joining surface.

Claims (1)

[Scope of utility model registration request] 1. An exhaust port is formed in a cylindrical sleeve integrally cast in a cylinder, and an exhaust passage is formed in the cylinder, the exhaust passage being continuous with the exhaust port. The exhaust passage is formed on an inner wall of the exhaust passage. A housing portion in which a control valve for varying the upper edge of the port is housed is formed such that the joint surface between the cylinder and the sleeve at the upper end of the exhaust passage is a part of the inner wall surface of the housing portion. At this joint surface, the sleeve is extended downward by a certain amount from the cylinder to provide a step, and the step is continuously formed at the lower end of the step.
A two-cycle engine equipped with an exhaust timing control device, characterized in that a sealing surface is formed to face an end surface of the control valve on the rocking side.