JPH0454212A - Secondary air introduction device for 2-cycle engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Skin! FIELD OF THE INVENTION The present invention relates to a device for introducing secondary air into an exhaust pipe for purifying exhaust gas in a two-stroke engine.

■An engine exhaust system equipped with such a secondary air introduction device is disclosed in Japanese Utility Model Application No. 60-95116.
A secondary air inlet leading to the atmosphere is opened at 300 degrees from the engine, and a check valve is installed in the secondary air passage connected to the inlet to allow only airflow toward the engine.
The length of the secondary air passage is at least 300 mm, and the length of the secondary air passage is at least 300 cm.
The cross-sectional area of the next air passage from the exhaust pipe to the check valve is approximately -
It is shaped like this.

However, the flow rate of the secondary air flowing into the exhaust pipe through the secondary air passage depends on the displacement of the engine, so
Unless this exhaust amount is taken into account, an optimal secondary air introduction device cannot be obtained.

The present invention has been made in view of these circumstances, and
In the present invention, two
A device for introducing secondary air, in which a secondary air supply pipe is connected to a secondary air inlet provided in an exhaust pipe, and a check valve is installed in the secondary air supply pipe to allow only airflow toward the exhaust pipe. In this device, the length f (m) from the check valve of the secondary air supply pipe to the secondary air inlet is
), the secondary air supply pipe should be selected within the range given by the following formula (%), and the cross-sectional area of the secondary air supply pipe should be 10 to 20% of the cross-sectional area of the exhaust pipe, and the secondary air inlet 2 from the engine cylinder wall
Installed approximately in the upper half of the exhaust pipe section within 00 Kaku.

By selecting the length, cross-sectional area, and position of the secondary air inlet of the secondary air supply pipe as described above, secondary air is efficiently introduced into the exhaust pipe, contributing to exhaust gas purification.

Figure 1 is a side view of the main parts of a motorcycle equipped with a two-stroke engine having a secondary air introduction device according to the present invention. 1 is a head pipe, and 2 is a pair of left and right main frames extending obliquely downward and rearward from the head pipe 1. A rear fork 3 extends rearward from the rear end of the main frame 2 so as to be tiltable up and down, and a rear wheel 4 is attached to the rear end of the rear fork 3.
is pivoted. A seat 6 is attached to a seat rail 5 extending rearward from an intermediate portion of the main frame 2,
A fuel tank 7 is mounted in front of it.

An engine 9 is installed between a steering member 8 hanging from the front of the main frame 2 and a lower rear end of the main frame 2, and the rear wheels 4 are driven by the engine 9 via a tribe chain.

The engine 9 is a two-stroke engine, and an air-fuel mixture is supplied through an intake pipe 11 and a carburetor 12 to an intake port 10 communicating with a crank chamber. The upstream side of the intake pipe 11 is connected to an air cleaner 13. 14 is an exhaust port provided in the cylinder 15 of the engine 9, and the front end of the exhaust pipe 16 is connected to the exhaust port 14.
It is connected to the.

The exhaust pipe 16 extends forward and downward from the exhaust port 14, curves backward, passes under the engine 9, exits to the right side of the rear wheel 4 at the rear, and connects to the muffler 17. An auxiliary catalytic converter 18 made of a cross catalyst body is provided in the curved portion at the front of the exhaust pipe 16. exhaust pipe 1
6 expands in diameter at the lower rear portion of the engine 9 to form an expansion chamber 23 . A tail pipe 24 enters the chamber from the diameter-reduced rear end 23a of the expansion chamber 23 and extends forward along the axis, and a main catalytic converter 25 made of a metal catalyst is provided at the front end of the tail pipe 24. The auxiliary catalytic converter 18 reacts with the exhaust gas upstream of the main catalytic converter 25 to increase the temperature of the exhaust gas at the main catalytic converter 25 .

FIG. 2(b) shows the catalyst carrier 26 of the main catalytic converter 25.
FIG. This catalyst carrier 26 is formed by spirally winding a corrugated plate 27 of ferritic stainless steel around a core 28, and the corrugated plate 27 starts from one end to the other as shown in FIG. The pitch of the waveform gradually changes toward the end, and by wrapping the corrugated plate 27 outward with the end with the smaller pitch inside, the adjacent layers can be separated as shown in Figure (b). The ridges collide with each other, forming a rigid honeycomb-like multi-channel member as a whole. Platinum, rhodium,
Support precious metal catalysts such as rare earth metals and cesium.

A secondary air introduction device according to the present invention is further connected to the front end of the exhaust pipe 16. That is, a secondary air inlet 19 is provided immediately after the engine exhaust port 14 and immediately before the auxiliary catalytic converter 18.
9 communicates with the clean side of the air cleaner 13 via a secondary air supply pipe 20.

A reed valve 21 is installed in the secondary air supply pipe 20 as a check valve.
is provided. The reed valve 21 is attached to the inner surface of the main frame 2 via a stem member. When this reed valve 21 is opened by the negative pressure in the exhaust pipe 16, secondary air is introduced from the air cleaner 13 into the exhaust gas in the exhaust pipe 16, and the catalytic converter 18.
25 enhances the exhaust purification effect. The reed valve 21 only allows the flow from the air cleaner 13 side to the exhaust pipe 16 side, and blocks the flow from the exhaust pipe 16 side to the air cleaner 13 side.

FIG. 3 is a side view showing another embodiment in which the secondary air introduction device according to the present invention is applied to a scooter type motorcycle. 3
0 is a seat, and a steering head 32 stands up in front of the seat with a low floor portion 31 in between. 33 is the front wheel, 3
4 is the rear wheel. The rear wheel 34 is suspended on a vehicle body frame 36 via a swing unit 35 so as to be able to swing up and down. A two-stroke engine 37 is integrally provided at the front of the swing unit 35. The area below the seat 30 and above the engine 37 is covered with a body cover 38, and a storage box 39 for storing a helmet and the like is fixed to the vehicle body frame 36 inside.

The intake port 40 of the engine 37 includes an intake pipe 41 and a carburetor 42.
An intake system consisting of an air cleaner 43 and an air cleaner 43 is connected to the exhaust port 44, and an exhaust pipe 45, a muffler 46, and a silencer 47.
An exhaust system consisting of a tail pipe 48 and a tail pipe 48 is connected thereto. This exhaust system is disposed on the right side of the vehicle body, that is, on the side opposite to the swing unit 35 with respect to the rear wheel 34. An auxiliary catalytic converter 49 made of a loss catalyst is provided at the front curved portion of the exhaust pipe 45, as in the previous embodiment, but in this embodiment, a muffler 46 is provided at the rear of the exhaust pipe 45.
A main catalytic converter 50 made of a metal catalyst body is attached to the rear end of the main catalytic converter 50 .

Exhaust port 44 at the front end of exhaust pipe 45 and auxiliary catalytic converter 4
A secondary air inlet 51 is provided between the main body 9 and a secondary air supply pipe 52 made of a metal tube, and the other end is connected to a reed valve 53. These two
The secondary air inlet 51, the secondary air supply pipe 52, and the reed valve 53 are the secondary air inlet 19.2 in the embodiment shown in FIG.
It is constructed in exactly the same way as the secondary air supply pipe 20 and the reed valve 21. However, in this embodiment, the reed valve 5
3 is integrally provided with a fan shroud 54 for forced cooling provided to cover the cylinder portion of the engine 37. An upstream secondary air supply pipe 55 made of a rubber hose or the like is connected to this reed valve 53, extends upward along the outside of the storage box 39, and is connected to an air cleaner 56 for secondary air. The air cleaner 56 communicates with the inside of the storage box 39 via an air intake port 57. Therefore, the air in the storage box 39 is transferred to the exhaust pipe 45 from the air cleaner 56, the secondary air supply pipe 55, the reed valve 53, the secondary air supply pipe 52, and the secondary air inlet 51.
It is supplied as secondary air through the air.

By the way, in each of the embodiments shown in FIGS. 1 and 3, 2
The length and cross-sectional area of the secondary air supply pipe 20.52 and the position of the secondary air inlet 19.51 are set as follows.

First, the length from the reed valve 21°53 of the secondary air supply pipe 20.52 to the secondary air inlet port 19.51! (4th
(see figure) (Kaku) is the engine displacement of 9.37
c), the value is selected within the range given by the following formula (%). This is due to the following reasons.

FIG. 5 shows how the length i of the secondary air supply pipe is varied for each engine with a displacement of 50 cc, 90 cc, and 150 cc and equipped with a secondary air introduction device similar to that described above. The results of measuring the secondary air flow rate Q (1/sec) to the exhaust pipe under suitable operating conditions are shown. From the same figure, it can be seen that the secondary air flow rate Q depends on the length 2 of the secondary air supply pipe and the exhaust pipe X of the engine, and that the optimal pipe length 1 that maximizes Q for each displacement is
．． exists, 1. It turns out that it is about 200 kaku for an engine with a displacement of 50 cc, and about 500 kaku for an engine with a displacement of 150 cc. However, the optimum pipe length is 10
If the relationship between
As shown in the figure, it is indicated by a straight line a of 1-3x+5. Therefore, in the present invention, the length of the secondary air supply pipe was selected as described above, including an allowance of ±7.5% to this value.

In Figure 6, the straight line is j! = (3x+50)
The upper limit value is (1+0°075), direct #IC is I! −(3
x+50) (1-0,075),
The length l of the secondary air supply pipe 20.52 in each of the above embodiments is selected to fall between the straight line Jib and C.

Next, in each of the embodiments described above, the secondary air supply pipe 20.
The cross-sectional area SA of 52 is 1 of the cross-sectional area SA of the exhaust pipe 16.45.
It is 0 to 20%. FIG. 7 shows the results of measuring the secondary air flow rate Q with various cross-sectional area ratios SA/Sl: for each of the engines. As can be seen from the figure, at any displacement, when the cross-sectional area ratio SA/St is 10 to 20%, the secondary air flow rate Q is large, and when the cross-sectional area ratio exceeds this range, the flow rate Q decreases. Therefore, by selecting the cross-sectional area SA of the secondary air supply pipe 20.52 as described above, secondary air can be efficiently introduced into the exhaust pipe 16.45.

Furthermore, in each of the above embodiments, the secondary air inlet 19
．． 51 is installed approximately in the upper half of the exhaust pipe portion within 200 mr from the cylinder wall 58 of the engine 9,370 (see FIG. 4, in which 59 is a cylinder and 60 is an exhaust boat). Figure 8 also shows the cylinder wall 5 for an engine with a displacement of 50 cc and an engine with a displacement of 150 cc.
The results of measuring the secondary air flow rate Q with various lengths from 8 to the secondary air inlet are shown.

As can be seen from the figure, when the length becomes 200 am or more, the flow rate Q decreases. Therefore, in the above embodiment, the length is set within 200 mm to ensure a sufficient flow rate of secondary air. Also, the secondary air inlet 19.51 is the exhaust pipe 16.45.
Since the secondary air supply pipe 16.45 is provided approximately in the upper half of the exhaust pipe 16.45, oil and the like will not flow back into the secondary air supply pipe 20.52 from the exhaust pipe 16.45.

Light place ■Karaki! As described above, the present invention is a device for introducing secondary air into the exhaust pipe of a two-stroke engine, in which a secondary air supply pipe is connected to a secondary air inlet provided in the exhaust pipe, and the secondary air is In a device in which the supply pipe is equipped with a check valve that only allows airflow toward the exhaust pipe, the length f (mm) from the check valve of the secondary air supply pipe to the secondary air inlet is determined by the engine exhaust When the amount is x (cc), the secondary air supply pipe is selected within the range given by the following formula (% formula %), and the cross-sectional area of the secondary air supply pipe is 10 to 20% of the cross-sectional area of the exhaust pipe, and Connect the secondary air inlet from the engine cylinder wall.
Since it is installed almost in the upper half of the exhaust pipe within 0011II1, secondary air is efficiently introduced into the exhaust pipe, and a good exhaust purification effect is obtained. No backflow into the supply pipe.

[Brief explanation of drawings]

Fig. 1 is a side view of main parts of a motorcycle equipped with a two-stroke engine having a secondary air introduction device according to the present invention;
The figure is a cross-sectional view showing a catalyst support provided in the exhaust system of the motorcycle, FIG. 3 is a side view of a scooter-type motorcycle showing another embodiment of the present invention, and FIG. A schematic diagram showing the main parts of the secondary air introduction device. Figure 5 is a diagram showing the relationship between the length of the secondary air supply pipe and the secondary air flow rate. Figure 6 is a diagram showing the relationship between the engine displacement and the secondary air flow rate. Figure 7 is a diagram showing the relationship between the secondary air flow rate and the cross-sectional area ratio of the secondary air supply pipe and exhaust pipe, and Figure 8 is a diagram showing the relationship between the secondary air inlet position and the secondary air flow rate. It is a line diagram showing a relationship. 1...Head pipe, 2...Main frame, 3.
...Rear fork, 4...Rear wheel, 5...Seat rail, 6...Seat, 7...Fuel tank, 8...Steel member, 9...Engine, 10... Intake port, 11
...Intake pipe, 12...Carburizer, 13...Air cleaner, 14...Exhaust port, 15...Cylinder, 16...
...Exhaust pipe, 17...Muffler, 18...Auxiliary catalytic converter, 19...Secondary air inlet, 20...Secondary air supply pipe, 21...Reed valve, 23... Expansion chamber, 24... Tail pipe, 25...
・Main catalytic converter, 26... Catalyst carrier, 27...
・Corrugated plate, 28...core, 30...sheet, 31...
・Floor part, 32...Steering head, 33...
・Front wheel, 34... Rear wheel, 35... Swing unit, 36... Body frame, 37... Engine, 38
...Body cover, 39...Storage box, 40.
... Intake port, 41... Intake pipe, 42... Carburetor, 4
3...Air cleaner, 44...Exhaust port, 45...
Exhaust pipe, 46...muffler, 47...silencer, 4
8... Tail pipe, 49... Auxiliary catalytic converter, 50... Main catalytic converter, 51... Secondary air inlet, 52... Secondary air supply pipe, 53... Reed valve, 54...Fan shroud, 55...Secondary air supply pipe, 56-...Air cleaner, 57...Air inlet, 58...Cylinder wall, 59...Cylinder, 6
0...Exhaust boat. Figure Figure 8 Length from cylinder wall to inlet

Claims (1)

[Claims] A device for introducing secondary air into the exhaust pipe of a two-stroke engine, in which a secondary air supply pipe is connected to a secondary air inlet provided in the exhaust pipe, and the secondary air supply pipe is connected to the secondary air supply pipe. In a device equipped with a check valve that allows airflow only toward the exhaust pipe, the length l(
mm) is selected within the range expressed by the following formula l = (3x + 50) (1 ± 0.075), where the engine displacement is x (cc), and the cross-sectional area of the secondary air supply pipe is selected. The cross-sectional area of the exhaust pipe should be 10 to 20%, and the secondary air inlet should be 20% from the engine cylinder wall.
A secondary air introduction device for a two-stroke engine, characterized in that it is provided in approximately the upper half of an exhaust pipe portion within 0.00 mm.