JPH0255607B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) This invention provides an auxiliary sub-exhaust passage that connects the inside of the cylinder and the main exhaust passage in addition to a main exhaust passage that communicates with the inside of the cylinder. The present invention relates to an exhaust control device that includes an on-off valve that can be opened and closed in an exhaust passage.

(Prior art) For example, in a two-stroke engine mounted on a motorcycle, as an exhaust control device, a main exhaust passage communicating with the inside of the cylinder of a cylinder block is used as an exhaust control device, as disclosed in Japanese Patent Publication No. 60-249614. In addition, the inside of the cylinder and the main exhaust passage are connected by a sub-exhaust passage, and an on-off valve is provided on the sub-exhaust passage. This opening/closing valve is controlled so as to communicate the sub-exhaust passage when the engine is running at high speeds, and to close the sub-exhaust passage when the engine is running at low speeds.

In this way, at high speeds, by using the sub-exhaust passage in addition to the main exhaust passage as an exhaust passage, the area of the exhaust passage can be obtained larger than at low speeds.
That is, on the output curve, the output peak shifts to the higher rotation side than the output peak when the sub-exhaust passage is not used, so that high output can be obtained in the high rotation range.

On the other hand, if the sub-exhaust passage is left open at low speeds as it is at high speeds, the area of the exhaust passage will be too large, resulting in the high-speed, high-output type described above, which will result in lower output and torque at low speeds. Therefore, by rotating the opening/closing valve, for example, 90 degrees from the high speed state, the sub-exhaust passage is closed and exhaust is exclusively carried out through the main exhaust passage, thereby increasing the output at low speeds. It is designed to ensure torque.

In such an exhaust control device, in order to rotationally drive the on-off valve, a pinion is generally provided at one end of the on-off valve, and a drive rack is provided in mesh with the pinion.

However, in the past, the drive rack was placed in the wall of the cylinder block above the main exhaust passage.

When the drive rack is disposed above the main exhaust passage in the cylinder block, a rack support boss for supporting the drive rack is provided at a portion corresponding to the upper part of the main exhaust passage of the cylinder. , due to the presence of such a rack support boss, the upper part of the main exhaust port of the main exhaust passage becomes hot, and this temperature increase increases the speed of the reflected wave of the exhaust pressure to the main exhaust port. This caused the output peak on the output curve to shift toward higher rotational speeds, which caused torque to drop at low rotational speeds.

Furthermore, if the drive rack is installed at a high position above the cylinder, that position will hit a location where the engine is likely to vibrate, which may cause looseness between the drive rack and the opening/closing valve, which can easily cause malfunction.

Further, the drive rack described above is driven in one direction at low speeds and in the other direction at high speeds according to the rotational state of the engine, and for this reason, the rack drive shaft, which has one end engaged with the governor sleeve in the crankcase, is driven in one direction at low speeds and in the other direction at high speeds. A swinging arm is provided at the other end and is driven by a pin of this swinging arm.

However, in the conventional case, since the drive rack is located at the top of the cylinder, it is necessary to install the rack drive shaft with its axis pointing from inside the low crankcase to the top of the high cylinder block. will be long,
In particular, when a long rack drive shaft is provided along the outer space of the cylinder, the upper part of the engine becomes quite large.

Moreover, if the rack moving shaft is long, it will cause an increase in the weight ratio and cost of the engine.

In addition, as this type of exhaust control device,
-39112 publication also discloses a technology with almost the same technical content.

(Object of the Invention) The present invention has been made in view of the above problems, and it is possible to prevent torque reduction at low engine speeds, prevent malfunction of the opening/closing valve, and reduce the size and weight of the engine. The aim is to reduce costs.

(Structure of the Invention) In order to achieve the above object, the present invention provides a main exhaust passage that communicates with the inside of the cylinder of a cylinder block, and a sub-exhaust passage that connects the inside of the cylinder and the main exhaust passage as an auxiliary exhaust passage. An on-off valve is provided in the sub-exhaust passage to allow the sub-exhaust passage to communicate with the cylinder at high engine speeds, while closing the sub-exhaust passage at low engine-speeds, and the on-off valve opens and closes the sub-exhaust passage at the top. A rotatable valve body is provided, and a pinion is provided at the bottom, and a drive rack that engages with the pinion and rotates the opening/closing valve in conjunction with the crankshaft is located below the main exhaust passage. By doing so, it is possible to prevent the upper part of the main exhaust passage in the cylinder block from increasing in temperature, suppress the increase in the reflected wave velocity due to the exhaust pressure in the main exhaust passage, and also make it possible to use a shorter rack drive shaft. ,Moreover,
It is possible to arrange the rack drive shaft without making special use of the side space of the cylinder.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a two-stroke engine mounted on a two-wheeled motor vehicle, in which 1 is a crankcase, and the crankcase 1 is provided with a crankshaft (not shown).

A cylinder block 2 is attached to the upper part of the crankcase 1, and a cylinder head 3 is attached to the upper part of the cylinder block 2. Here, F in the figure corresponds to the front when the vehicle is mounted on a two-wheeled motor vehicle.

The cylinder block 2 is formed with a cylinder 4 whose center is inclined forward, and a main exhaust passage 5 is formed on the front side of the cylinder 4 as shown in FIG.
A pair of left and right sub-exhaust passages 6, 6 are provided. The main exhaust passage 5 is as shown in FIG.
Connect the circular main exhaust port 5A to the cylinder 4 (second
(Fig.) side, and is formed as a passage that tapers in the direction corresponding to the front of the engine, and as seen from the right side of the engine, as shown in Fig. 1, the passage slopes downward in the F direction in front of the engine. It is formed with a center.

The main exhaust passage 5 has second exhaust passages on both sides thereof.
A pair of left and right sub-exhaust passages 6, 6 shown in the figure are provided, and the sub-exhaust passages 6, 6 connect the cylinder 4 and the main exhaust passage 5 as passages narrower than the main exhaust passage 5.

Opening/closing valves 7, 7 for opening and closing the sub-exhaust passages 6, 6 are provided near the end portions of each of the sub-exhaust passages 6, 6.

As shown in FIG. 3, each on-off valve 7 is
It has a valve body 8 at its upper part, a valve shaft 9 at its lower part, an upper pivot part 10 at its upper end, and a lower pivot part 1 at its lower end.
1. The on-off valve 7 is arranged substantially parallel to the center line of the cylinder 4, as shown in FIG. A vertically elongated valve passage 12 is formed in the valve body 8 of each of the on-off valves 7, and this valve passage 12 is a passage along the center line of the sub-exhaust passage 6, that is, inclined toward the axial center of the on-off valve 7. It is formed as a passage.

Here, the valve passage 12 has a pair of crescent-shaped closing walls 13, 1 in a cross section in FIG.
It is formed between 3.

As shown in FIG. 2, the opening/closing valve 7 connects the cylinder 4 and the main exhaust passage 5 by making the center of the valve passage 12 concentric with the sub-exhaust passage 6 in a high rotation range above a certain level. On the other hand, in the low rotation range, as shown in FIG. 4, both opening and closing valves 7, 7 are rotated 90 degrees in the same direction, that is, counterclockwise, to close the sub-exhaust passages 6, 6. Thus, communication between the cylinder 4 and the main exhaust passage 5 is cut off. In this case, 3
0 and 30 are the first common communication passages, which are connected to the main exhaust passage 5.
The first common communication passages 30, 30 are formed at opposing positions on the inner walls of the valve passages 12, and the first common communication passages 30, 30 are arranged corresponding to the main exhaust passage 5 side of each valve passage 12 in a low rotation state. The communication passage 30 and the valve passage 12 communicate with each resonance chamber 32 through a second common communication passage 31.

The opening/closing valve 7 has a valve pinion 14 at its lower portion, and a drive rack 15 meshes with the valve pinion 14, as shown in FIG.

The drive rack 15 in this case is arranged near the lower end of the cylinder block 2 below the main exhaust passage 5, and its longitudinal center is directed in the left-right direction of the engine. The sliding piece 16 provided at one end of the drive rack 15 is connected to a sliding hole 17 formed in the cylinder block 2 as the inner periphery of one end of the rack support boss 2A.
Furthermore, a drive shaft portion 18 provided at the other end is slidably supported by a rack bearing bush 19 screwed into the rack support boss 2A.

Here, the means for driving the drive rack 15 is constructed as follows.

That is, as shown in FIG. 5, reference numeral 20 is a governor mechanism, and a governor sleeve 21 is loosely fitted to a governor shaft 33 that rotates in conjunction with a crankshaft (not shown). A reciprocating engagement sleeve 22 is provided, and an engagement pin 24 provided at one end of a rack drive shaft 23 is engaged with this engagement sleeve 22.

As shown in FIG. 1, the rack drive shaft 23 is supported by a clutch cover 25 attached to the right side of the crankcase 1, and its axial center corresponds to the longitudinal direction of the engine.

A swing arm 26 that swings in the left-right direction of the engine is attached to one end corresponding to the front of the rack drive shaft 23, and a rack drive pin 28 is protruded from the tip of the swing arm 26. , this rack drive pin 28 is connected to the drive rack 15
It engages a rack sleeve 27 attached to one end of the holder. A drive case 29 is attached to the right side of the cylinder block 2, and the drive case 29 is a case body that covers from one end of the rack drive shaft 23 to one end of the drive rack 15.

In the above configuration, since the drive rack 15 for rotating the opening/closing valve 7 is arranged below the main exhaust passage 5, there is no need to provide a support boss for the drive rack 15 on the upper part of the cylinder block 2. Therefore, the temperature at the top of the cylinder block 2 is prevented from increasing, which also prevents the temperature inside the main exhaust passage 5 from increasing, so that the speed of the exhaust reflected wave inside the passage 5 does not increase, and therefore the temperature decreases. It becomes a high-speed, high-output type when rotating, that is, there is no risk that the output peak on the output curve will shift toward a high rotational speed and the output and torque will decrease.

Furthermore, since the drive rack 15 is provided at a lower position in the cylinder 4 than in the past, it is less susceptible to vibrations, which reduces the possibility of rattling between the drive rack 15 and the on-off valve 7, thereby preventing malfunction. Hard to wake up.

Further, as described above, since the drive rack 15 is located below the main exhaust passage 5, the rack drive shaft 23 for driving the drive rack 15 is
can also be placed on the bottom, thereby
The rack drive shaft 23 does not need to be long from the inside of the clutch cover 1 on the drive side to the top of the high cylinder block 2, and can be short.

Furthermore, a short rack drive shaft 23 suffices, contributing to reductions in engine weight and cost. Furthermore, since the rack drive shaft 23 does not need to be disposed in the side space of the cylinder block 2, the upper part of the engine can be made smaller.

In addition, when a pair of sub-exhaust passages 6 are provided as in the above embodiment, the drive rack 15 is placed so that one side is on the cylinder 4 side and the other side is on the side opposite to the cylinder, as shown by the two-dot chain line X in FIG. They can also be arranged at an angle so as to mesh with each other. Further, in the above embodiment, as shown in FIG. 2, one pair of sub-exhaust passages 6 are provided, but only one pair may be provided. Furthermore, the on-off valve 7 has 1
Although it has a pair of closing walls 13, 13, one of them may be omitted. In addition, the resonance chamber 32
If a pair of sub-exhaust passages 6 are provided, one of them may be omitted, and if only one sub-exhaust passage 6 is provided, it may not be provided.

(Effects of the Invention) As explained above, according to the present invention, the drive rack that communicates with the crankshaft and rotates the opening/closing valve is located below the main exhaust passage, so that Torque reduction is prevented, malfunction of the opening/closing valve is prevented, and the engine is made smaller and lighter and costs are reduced.

[Brief explanation of the drawing]

Fig. 1 is a right side view of a two-stroke engine showing an embodiment of the present invention, Fig. 2 is a sectional view taken along the - line in Fig. 1, Fig. 3 is a sectional view taken along the -
The figure is a sectional view taken along the - line in Figure 1 at low rotation.
FIG. 5 is a sectional view taken along the line -- in FIG. 1. 2...Cylinder block, 4...Cylinder, 5
...Main exhaust passage, 6...Sub exhaust passage, 7...
...Opening/closing valve, 8...Valve body, 14...Valve pinion, 15...Driving rack.

Claims (1)

[Claims] 1 It has a main exhaust passage that communicates with the inside of the cylinder of the cylinder block, and a sub-exhaust passage that connects the inside of the cylinder and the main exhaust passage as an auxiliary exhaust passage. The sub-exhaust passage 6 is provided with an opening/closing valve that closes the sub-exhaust passage at low rotation speeds, and the opening/closing valve has a rotatable valve body in its upper part for opening and closing the sub-exhaust passage, and a pinion in its lower part. An exhaust control device comprising: a drive rack that engages with the pinion and rotates the valve body in conjunction with a crankshaft, and is disposed below a main exhaust passage.