JPH02163411A - Exhaust controller for two-cycle engine - Google Patents

Abstract

PURPOSE:To improve the suction efficiency and scavenging efficiency by arranging the conical guide cylinder and reflection cylinder in an expansion guide at the downstream edge of an exhaust pipe so that the opened port parts having each expanded diameter are opposed and attaching and separating the both cylinders according to the engine operation state. CONSTITUTION:In an expansion chamber 16 formed at the downstream edge of an exhaust pipe 5, a conical guide cylinder 14 in which a movable cylinder part 17 slidingly contacts a fixed cylinder part 16 and a conical reflection cylinder 25 in which a collar 26 slidingly contacts the second exhaust pipe 8 are installed so as to be shiftable in the exhaust flowing direction 15, and negative pressure waves are generated by the guide cylinder 14, and the positive waves are generated by the reflection cylinder 25. A controller 37 drives servomotors 23 and 34 according to the operation state of an engine 1, and shifts the 34 according to the operation state of the engine 1, and shifts the guide cylinder 14 and the reflection cylinder 25 through the driving members 19 and 30, and changes the generation positions of the negative and positive pressure waves. Thus, the driving parts of the guide cylinder and the reflection cylinder can be made small-sized and lightweight, improving the suction efficiency and scavenging efficiency of the engine body.

Description

Detailed Description of the Invention A0 Object of the Invention (1) Industrial Field of Application The present invention is directed to an engine in which an upstream end of an exhaust pipe is connected to an exhaust port of an engine body, and an expansion chamber is connected to a downstream end of the exhaust pipe. The present invention relates to an exhaust control device for a two-stroke engine.

(2) Prior Art Conventionally, such a device is known from, for example, Japanese Utility Model Application Publication No. 1623/1983.

(3) Problems to be Solved by the Invention In the above conventional system, the muffler body forming the expansion chamber is movable in the axial direction and connected to the exhaust pipe, and the muffler body is driven in accordance with the operating state of the engine. This improves the air supply efficiency and scavenging efficiency of the engine body.

However, since the muffler main body is relatively large and heavy, a large driving force is required.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an exhaust control device for a two-stroke engine that solves the above-mentioned conventional problems by making the driven portion smaller and lighter.

B1 Structure of the Invention (11 Means for Solving the Problems) In the present invention, the upstream end of a guide tube disposed at the upstream end in the expansion chamber is connected to the downstream end of the exhaust pipe, and the guide tube is connected to the downstream end of the exhaust pipe. It is basically formed into a conical shape whose diameter increases toward the side, and its downstream end is movable along the exhaust flow direction. A reflector tube is provided which has a basically conical diameter and whose upstream end is movable along the exhaust flow direction. A driving means is connected to move the downstream end of the reflector tube and the upstream end of the reflector tube, respectively.

(2) Effect According to the above configuration, the exhaust gas is guided to the expansion chamber through the conical guide tube, so that negative pressure waves can be generated at the guide tube, and positive pressure waves can be generated by reflecting them at the reflection tube. It is possible to generate pressure waves, and by moving the downstream end of the guide tube and the upstream end of the reflector tube, the generation positions of negative pressure waves and positive pressure waves can be changed according to the engine operating condition, and the engine can be changed from high load to low load. It is possible to obtain stable output characteristics up to the load state.

(3) Embodiment Below, an embodiment of the present invention will be explained with reference to the drawings. First, in FIG. Exhaust port 3 opened and closed by piston 2 slidably fitted into cylinder block l
is open, and an exhaust timing control valve 4 is disposed above the exhaust port 3 to control the opening/closing timing of the exhaust port 3. Further, the upstream end of a first exhaust pipe 5 is connected to the tJ air port 3, and the first exhaust pipe 5 is connected via a pipe member 7 and a second exhaust pipe 8 that form an expansion chamber 6 therein. It is connected to a muffler (not shown).

The exhaust timing control valve 4 provided at the exhaust port 3 is fixed to a drive shaft 10 rotatably disposed on the cylinder lock 1. The servo motor 12 is connected to the servo motor 12 via the servo motor 12 . Further, the servo motor 12 is provided with a potentiometer 13 for detecting the operating amount of the servo motor 12, that is, the opening degree of the exhaust timing control valve 4.

Referring also to FIG. 2, the pipe member 7 is formed with a cross-sectional area larger than the cross-sectional area of the first exhaust pipe 5, and the upstream end of the pipe member 7 has a shape that contracts toward the upstream side. A tapered pipe portion 7a having a larger diameter is provided. The upstream end of the expansion chamber 6 formed by the pipe member 7 is basically formed into a conical shape whose diameter increases toward the downstream side of the expansion chamber 6, and the downstream end is connected in the exhaust flow direction. A guide tube 14 configured to be movable along the guide tube 15 is disposed, and the guide tube 14
The upstream end of is connected to the downstream end of the first exhaust pipe 5.

The guide tube 14 has a fixed tube section 16 connected to the first exhaust pipe 5.
and a movable cylinder part 17 movable along the exhaust flow direction 15.
It consists of The fixed cylinder part 16 is formed in a conical shape whose diameter becomes smaller toward the upstream side, and is fixed to the upstream end of the tube member 7 with the upstream end protruding. is connected to the downstream end of the first exhaust pipe 5.

Moreover, the movable cylinder part 17 is arranged so as to be movable along the exhaust flow direction 15 within the expansion chamber 6, and an upstream straight pipe part 17a and a downstream Taber pipe part 17b are integrally connected. It consists of being done. The inner diameter of the straight pipe portion 17a is set to be slightly larger than the outer diameter of the large diameter end, that is, the downstream end, of the fixed cylinder portion 16, and the straight pipe portion 17a slides on the outer surface of the large diameter end of the fixed cylinder portion 16. The fixed cylinder portion 16 is disposed so as to surround the portion of the fixed cylinder portion 16 facing into the expansion chamber 6 so as to move in the exhaust flow direction 15 . Further, the Taber pipe portion 17b is formed in a conical shape whose diameter increases toward the downstream side along the exhaust flow direction 15, and its small diameter end, that is, the upstream end thereof, is coaxially connected to the straight pipe portion 17a.

A drive shaft 18 having an axis perpendicular to the exhaust flow direction 15 is rotatably supported on the pipe member 7.
A driving member 19 fixedly attached to the guide cylinder 14 is connected to the movable cylinder part F of the guide cylinder 14 . That is, the drive member 19 is formed to straddle the Taber tube portion 17b of the movable cylinder portion 17, and the Taber tube portion 17b is connected to the drive member 19 via a pair of connecting pins 20 parallel to the drive shaft 18. be done.

Then, the movable cylinder portion 17 moves in the exhaust flow direction 15 in response to the swinging motion of the drive member 19 due to the rotation of the drive shaft,
As a result, the downstream end of the movable cylinder portion 17, that is, the downstream end of the guide cylinder 14, moves along the exhaust flow direction 15.

A pulley 2 is attached to the protruding end of the drive shaft 18 protruding from the pipe member 7.
1 is fixed to the pulley 21, and the pulley 21 is connected to a servo motor 23 as a driving means via a transmission cable 22 such as a transmission wire.
connected to. Furthermore, a potentiometer 24 is attached to the servo motor 23 in order to detect the operating amount of the servo motor 23, that is, the position of the downstream end of the guide cylinder 14 within the expansion chamber 6.

Referring also to FIG. 3, the downstream end of the pipe member 7 is integrally provided with a Taber pipe part 7b whose diameter becomes smaller toward the downstream side along the exhaust flow direction 15, and the second exhaust pipe 8 is , the intermediate portion is fixed to the small diameter end of the Taber pipe portion 7b and thrust into the expansion chamber 6.

Furthermore, at the downstream end of the expansion chamber 6, there is a reflector tube 2 which is basically formed into a conical shape and whose diameter increases toward the upstream side along the exhaust flow direction 15, and which is connected to the second exhaust pipe 8.
5 is disposed with its upstream end movable along the exhaust flow direction 15. That is, a cylindrical collar 26 is fitted to the downstream end of the reflecting tube 25, and this collar 26 is connected to the second
It is slidably fitted to the outer periphery of the exhaust pipe 8.

A drive shaft 28 parallel to the drive shaft 18 is rotatably supported on the Taber pipe portion 7b of the pipe member 7.
This drive shaft 28 and a driven shaft 29 installed at the large diameter end, that is, the upstream end of the reflection tube 25 are connected by a connecting rod 30. Moreover, in order to allow the connecting rod 30 to swing, a notch 31 extending in the exhaust flow direction 15 is provided at the large diameter end of the reflector tube 25 . Therefore, as the drive shaft 2 rotates, the connecting rod 30 swings and moves, thereby causing the reflector tube 25 to move along the exhaust flow direction 15.

A pulley 32 is attached to the end of the drive shaft 28 protruding from the pipe member 7.
This pulley 32 is connected to a servo motor 34 as a driving means via a transmission cable 33 such as a transmission wire. Moreover, the servo motor 34 has an operating amount of the servo motor 34, that is, a reflection tube 2 in the expansion chamber 6.
5. A potentiometer 35 is attached to detect the position of the upstream end.

The operation of each servo motor 12.23.34 is controlled by control means 37.
controlled by The control means 37 also includes an exhaust gas that detects the engine speed Nt detected by the engine speed detector 38, the throttle opening θa8 detected by the throttle opening detector 39, and the exhaust temperature in the expansion chamber 6. Temperature detector 40
Exhaust temperature TE detected by the engine cooling water temperature Te detected by the cooling water temperature detector 41, atmospheric temperature detector 4
The atmospheric temperature TA detected by the sensor 2 and the atmospheric pressure P detected by the atmospheric pressure detector 43 are respectively input, and the servo motor 1 is controlled by the potentiometers 13 and 24.35.
The operating amount detection values of 2, 23, and 34 are input. Furthermore, the control means 37 controls the operation of a solenoid valve 44 for controlling the amount of bleed air in a carburetor (not shown) and the operation of an oil pump 45.

In this control means 37, the opening degree of the exhaust timing control valve 4, that is, the operating amount of the servo motor 12, is controlled according to the engine operating state, and the downstream end position of the guide tube 14 is moved according to the engine load (servo motor 12). The operation of the motor 23 is controlled, and the operation of the servo motor 34 is also controlled to move the upstream end position of the reflector tube 25 in accordance with the engine load.

Here, the procedure for controlling the operation of the servo motor 23 will be explained with reference to FIG.
1, the data is read, and in the second step S2, 0 is searched for in the atmospheric pressure correction coefficient necessary for the correction calculation in the fourth step S4. That is, as shown in FIG. 5, a map is prepared in advance in which the atmospheric pressure correction coefficient KPA is determined according to the atmospheric pressure PA, and the atmospheric pressure correction coefficient KPA is determined according to this map.
is searched. In the next third step S3, an atmospheric temperature correction coefficient KTA necessary for the correction calculation in the fourth step S4 is retrieved. That is, as shown in FIG. 6, a map in which the atmospheric temperature correction coefficient is set to 0 according to the atmospheric temperature T^ is prepared in advance, and 0 is searched for the atmospheric temperature correction coefficient according to this map.

In the fourth step S4, the above-mentioned second and third steps S2. The read throttle opening degrees θ and H are corrected by Equation (11) using A as the correction coefficient obtained in S3.

θA,' -θtNX KPAX KrA--(1) Furthermore, in the next fifth step S5, the operating amount of the servo motor 23 is searched based on the engine rotation speed NE and the corrected throttle opening 0-inch'. be done.

That is, as shown in FIG. 7, the amount of rotation θ of the drive member 19 is the amount of operation of the servo motor 23. is predetermined as a three-dimensional map based on the throttle opening θAl and the engine speed N, and the rotation amount θ is determined in accordance with this map. is obtained. Here θ. As the value increases, the downstream end of the guide tube 14 moves toward the exhaust flow direction 15.
This indicates movement upstream along the .

In the sixth step S6, an exhaust temperature correction coefficient Lx necessary for the correction calculation to be performed in the next eighth step S7 is searched. That is, as shown in FIG. 8, a map is prepared in advance in which the exhaust temperature correction coefficient KTt is determined according to the exhaust temperature T, and the exhaust temperature correction coefficient 7. is searched.

Furthermore, in the seventh step S7, the correction coefficient KT! The operating amount θ is calculated according to the following equation (2) using . is corrected.

θ1=θ. x to □...(2) In the final eighth step S8, the operating amount θ obtained from the above equation (2). ' is output, and its operating amount θ.

The servo motor 23 will be operated accordingly.

Furthermore, the operation of the servo motor 34 is basically controlled according to the control procedure shown in FIG. 4 above.

Next, the operation of this embodiment will be explained. By controlling the opening degree of the exhaust timing control valve 4 according to the engine operating condition, the output of the two-cycle engine E is adjusted to the portion indicated by the diagonal line downward to the left in FIG. It increases like A. Also, guide tube 1
By controlling the downstream end position of 4 in accordance with the engine load, the output of the 2-cycle engine E increases as shown in a portion B indicated by diagonal lines downward to the right in FIG. That is, 2
In the low-load operating range of the cycle engine E, since the downstream end of the guide tube 14 is located on the downstream side along the exhaust flow direction 15, the negative pressure generated as the exhaust gas is introduced into the expansion chamber 6 by the guide tube 14. The generation site is located relatively downstream in the upstream end of the expansion chamber 6, and the negative pressure generation portion is located relatively far from the exhaust port 3 in response to the relatively long time interval between the exhaust and scavenging strokes. position and can also be 2
In the high-load operating range of the cycle engine E, since the downstream end of the guide tube 14 is located on the upstream side along the exhaust flow direction 15, the negative pressure generated as the exhaust gas is introduced into the expansion chamber 6 by the guide tube 14. The generation site is located relatively upstream at the upstream end of the expansion chamber 6, and the negative pressure generation portion is located relatively close to the exhaust port 3 in response to the relatively short time interval between the exhaust and scavenging strokes. By controlling the position of the negative pressure generator in this manner, fresh air is introduced and combustion gas is discharged in accordance with the engine operating state, and the output of the two-stroke engine E can be improved.

Furthermore, by controlling the upstream end position of the reflector tube 25 in accordance with the engine load, the output of the two-cycle engine E increases as shown in a portion C indicated by diagonal lines downward to the right in FIG.

In other words, in the low load operating range of the two-stroke engine E,
Since the upstream end of the reflector tube 25 is located on the downstream side along the exhaust flow direction 15, the positive pressure wave generated by the wandering gas reflected by the reflector tube 25 is generated at a relatively downstream side at the downstream end in the expansion chamber 6. This position allows the positive pressure generating part to be located relatively far from the exhaust port 3 in response to the relatively long time interval between the exhaust and scavenging strokes, and also allows the positive pressure generating part to be located relatively far from the exhaust port 3. Since the upstream end of the reflector tube 25 is located on the upstream side along the exhaust flow direction 15, the positive pressure generated when the exhaust gas is reflected by the reflector tube 25 is generated in the expansion chamber 6.
The positive pressure generating section can be located relatively close to the exhaust port 3, corresponding to the relatively short time interval between the exhaust and scavenging strokes. Is it on the side where the negative pressure generator is located above? In combination with ffl, it is possible to efficiently introduce fresh air and exhaust combustion gas in accordance with the engine operating state, thereby improving the output of the two-stroke engine E.

Moreover, the guide tube 14 is driven to improve the output.
and the reflecting tube 25, and the driving force for driving them can be relatively small.

C0 Effects of the Invention As described above, according to the present invention, the upstream end of the guide tube disposed at the upstream end in the expansion chamber is connected to the downstream end of the exhaust pipe, and the guide tube is directed toward the downstream side. It is basically formed into a conical shape with its diameter increasing as it goes toward the upstream side, and its downstream end is movable along the exhaust flow direction. A reflector tube is basically formed in a conical shape and its upstream end is movable along the exhaust flow direction. Since the driving means are connected to each other to move the upstream end of the reflector tube, the positions of the negative pressure generating section and the positive pressure generating section within the expansion chamber can be changed according to the engine operating state.
It is possible to obtain stable output characteristics from engine high load conditions to low load conditions, and by driving the guide tube and reflector tube individually, more precise control is possible, and the guide tube and reflector tube are relatively small. It is light and therefore requires less driving force.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is an overall schematic diagram, FIG. 2 is a sectional view taken along the line ■-■ of FIG. 1, and FIG.
Figure 4 is a flowchart showing the control procedure of the control means, Figure 5 is a map for searching the atmospheric pressure correction coefficient, and Figure 6 is a search for the atmospheric temperature correction coefficient. Figure 7 is a map for searching the operating amount of the drive means, Figure 8 is a map for searching the exhaust temperature correction coefficient, and Figure 9 is a map for searching the output. . It is a characteristic diagram. ■... Cylinder block as the engine body, 3.
... Exhaust port, 5... First exhaust pipe, 6... Expansion chamber, 14... Guide tube, 15... Exhaust flow direction, 23.
34... Servo motor as driving means, 25...
Reflector tube, E...2 cycle engine

Claims (1)

[Claims] In an exhaust control device for a two-stroke engine, in which an upstream end of an exhaust pipe is connected to an exhaust port of an engine body, and an expansion chamber is connected to a downstream end of the exhaust pipe, the downstream end of the exhaust pipe is connected to an upstream end of the expansion chamber. The upstream end of a guide tube disposed at the end is connected, and the guide tube is basically formed into a conical shape with its diameter increasing toward the downstream side, and the downstream end is connected along the exhaust flow direction. A reflector is configured to be movable, and at the downstream end of the expansion chamber is basically formed into a conical shape whose diameter increases toward the upstream side, and whose upstream end is movable along the exhaust flow direction. A two-stroke engine characterized in that a cylinder is disposed, and driving means are connected to the guide cylinder and the reflection cylinder, respectively, to move the downstream end of the guide cylinder and the upstream end of the reflection cylinder according to the engine operating state. exhaust control device.