JPS5912846B2 - Secondary air heating method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a thermal reactor type or afterburner type engine that supplies secondary air to exhaust gas and purifies the exhaust gas by re-combustion, and is particularly suitable for motorcycles. The purpose of the present invention is to provide a method and apparatus for heating secondary air.

In the above systems, secondary air is generally supplied into the exhaust gas by an air pump or suction valve.

In this case, it is known that the higher the temperature of the secondary air is, the higher the thermal reactivity is, and the lower the temperature of the reactable exhaust gas is.
In other words, supplying preheated secondary air into the exhaust gas improves the exhaust gas purification performance, and also shortens the temperature rise time of the thermal reactor itself during a cold start, shortening the period during which harmful unburned components are discharged. Therefore, it is advantageous in terms of exhaust gas countermeasures. Methods for residual heat of secondary air include methods that use direct exhaust heat and methods that use the temperature of cooling water, but the former requires a lot of space and is unsightly, while the latter increases the water temperature. Since it takes time for this to occur, the period during which harmful unburned components are discharged after a cold start becomes long, and there are also disadvantages in that it cannot be used in air-cooled engines. Therefore, it is difficult to apply it particularly to motorcycles. The present invention provides a simple, reliable, and effective method and device that can solve the above conventional problems by using exhaust gas heat as a heat source and heating secondary air with a heat pipe. Particularly when applied to motorcycles, it is very advantageous because there is a high degree of freedom in designing the relative positions of the heat source part and the heating part, and it can also be used in air-cooled engines.

Next, it will be explained with reference to the drawings. The illustrated engine employs a suction valve system that utilizes exhaust pulsation to supply secondary air.

The check valve 1 is a reed valve that allows air to pass only in the forward direction indicated by the arrow, and is connected to the clean side of the air cleaner 11 through an air introduction pipe 10'. Reed valve 1
The case 20 that contains the
1 is a distribution groove 2 which passes through an introduction path 5 provided within the thickness of a cylinder block between cylinders 4 arranged perpendicularly to the plane of the paper.
2, and the distribution groove 22 communicates with the discharge port 23 in the exhaust port 8 through the air supply hole 9 in the cylinder head 6. The distribution groove 22 extends in the direction in which the cylinders 4 are arranged at the mating surface of the cylinder block 3 and the cylinder head 6, and reaches the lower side of the exhaust port 8 of each cylinder. The discharge port 23 is provided on the inner bottom surface of the exhaust port 8 near the exhaust valve 13. The exhaust port 8 communicates with a muffler 16 through an exhaust pipe 14 having a thermal reactor 15 in the middle. The lower end 7a of the heat pipe 7 is inserted into the exhaust pipe 14 immediately downstream of the thermal reactor 15, and the space between the lower end 7a and the hole made in the exhaust pipe 14 for passing the heat pipe 7 is sealed with a welded portion 24. The upper end 7b of the heat pipe 7 covers almost the entire length of the air introduction pipe 10, forming a heat exchanger H. The heat pipe 7 has a well-known structure in which an evaporative liquid is sealed in the bottom of a sealed heat-resistant metal tube and a layer of metal mesh is provided on the inner surface, and the heat pipe 7 has a known structure in which an evaporative liquid is sealed in the bottom of the heat-resistant metal tube. It is inclined downward in the front with a slight gap between the two sides, and has a cover 25 fixed to the mission case 12 on the outside. In the figure, 2 is a carburetor, 26 is an intake port, 27 is an intake valve, 2
8 is a piston, and 29 is a combustion chamber. The air-fuel mixture formed in the carburetor 2 passes through an intake port 26 and an intake valve 27 and is introduced into a combustion chamber 29. After being combusted there, the exhaust gas passes through an exhaust valve 13, an exhaust port 8, and an exhaust pipe 14 to become thermal. to reactor 15. ', where it undergoes purification treatment and is subsequently discharged into the atmosphere through an exhaust pipe 14 and a muffler 16.

On the other hand, the air on the clean side of the air cleaner 11 is sucked by the negative pressure of exhaust pulsation acting on the discharge port 23, and the air is drawn into the air inlet pipe 10'', the check valve 1, the heat exchanger H, the air inlet 4, the inlet 5,
The air passes through the distribution groove 22 and the air supply hole 9 and is discharged from the discharge port 23 into the exhaust port 8 . While the secondary air passes through the air introduction pipe 10 in the heat exchanger H, it receives heat from the exhaust gas and is heated by the action of the heat pipe 7. That is, the liquid in the lower end part 7a of the heat pipe absorbs the heat of vaporization from the heated exhaust gas that has reacted in the thermal reactor 15, evaporates, moves up the heat pipe 7, and passes through the air introduction pipe 10 in the heat exchanger H.
The low-temperature secondary air passing through the heat pipe 7 is given latent heat, condensed and liquefied, flows down the inner surface of the heat pipe 7, reaches the lower end 7a again, and by repeating the above cycle, the exhaust pipe 1
The heat of the exhaust gas in the air inlet 4 can be supplied to the secondary air in the air introduction pipe 10. The secondary air heated by heat exchanger H is
Subsequently, while passing through the introduction passage 5 within the wall thickness of the cylinder block 3, part of the heat generated in the combustion chamber 29 is received and the temperature further rises, and the gas flows from the discharge port 23 into the exhaust port 8 in a high temperature state. Added to exhaust gas by inhalation. In the first invention, secondary air is supplied into the exhaust gas of a cross-flow type engine having an exhaust port on one side of the cylinder head and an intake port on the opposite side, and exhaust gas purification is performed by re-combustion. In this method, the heat of the exhaust gas is transferred to the secondary air in the secondary air supply passage through the heat pipe 7, and the heated secondary air is transferred to the exhaust port 8 near the exhaust valve 13.
Since the heat source is supplied internally, the arrangement from the heat source to the heat receiving part is relatively free, and when applied to a motorcycle or the like, it is possible to integrate the heat source without damaging the basic form of the motorcycle.

Furthermore, since the required amount of secondary air is very small compared to the amount of intake air, it can be sufficiently heated with a heat pipe. Moreover, the secondary air is forcibly sucked in by the negative pressure of the exhaust pulsation acting in the exhaust port 8, and each time high-temperature exhaust gas flows out from the combustion chamber 29 into the exhaust port 8, the necessary amount of secondary air is added. This not only eliminates the need for a complicated secondary air control mechanism, but also eliminates the need for a pump to supply secondary air, greatly simplifying the device. Further, the secondary air is sucked into the exhaust gas immediately after flowing out from the combustion chamber 29 and is well mixed into the exhaust gas, improving thermal reactivity. Furthermore, since the heat pipe 7 is used, there is no need to attach a bulky heat exchanger to the exhaust pipe 14 or to send the exhaust gas to the secondary air supply system, and the exhaust gas can be removed by X while maintaining the optimum shape of the exhaust system. Heat can be easily used. Since installation of the heat pipe 7 requires almost no space, there is no fear that the appearance will deteriorate, and there is an advantage that the heat exchanger H can be installed regardless of the location of the secondary air intake port 21. Of course, the effect of heating the secondary air is similarly exhibited. In other words, the temperature of the secondary air is heated by the high-temperature exhaust gas, so it becomes sufficiently high, the thermal reactivity improves, and the temperature of the exhaust gas at which the reaction is possible becomes lower.
The thermal reaction continues over a wide operating range, especially during a cold start.
The temperature rise time of the thermal reactor itself is shortened, and the period during which harmful unburned components are discharged is shortened. The second invention is a cross-flow type engine having an exhaust port 8 on one side of the cylinder head 6 and an intake port 26 on the opposite side. The clean air of the air cleaner 11 is connected to the discharge port 23 in the adjacent exhaust port 8, and the air cleaner 11 is connected to the inlet port 21 at the other end through the check valve 1 which allows flow only to the heat receiving path of the heat exchanger H and the inlet port 21 side. Since the inside of the exhaust pipe 14 downstream of the thermal reactor connected to the side and connected to the exhaust port 8 at a lower position than the heat exchanger H is connected to the heating path of the heat exchanger H by the heat pipe 7, In addition to the above-mentioned effects of the first invention, the following effects can be obtained. That is, when positive pressure is applied to the exhaust port 8, the check valve 1 closes, eliminating the possibility that the exhaust gas will flow back to the clean side of the air cleaner 11. The secondary air flows in one direction due to the pump action of the check valve 1. Therefore, it is possible to reliably supply the amount of secondary air depending on the operating state of the engine without providing a special pump. The air introduction pipe 10 in the heat exchanger H becomes a heat receiving path, and the upper end 7b of the heat pipe around it becomes a heating path. Since this heat exchanger H occupies the upper end of the heat pipe 7, the heat from the heat pipe 7 is The exchange of information will be carried out smoothly. Since the main air silencer 11 serves both as an air cleaner for secondary air and as a silencer, the number of parts is reduced and the structure is simplified. The secondary air heated in the heat exchanger H is doubly heated in the introduction passage 5 in the cylinder block 3, and the heating effect is further improved. In addition, in a four-stroke engine as shown in the figure, the carburetor 2 and the transmission case 12
It is easy to obtain a relatively large space for installing the check valve 1 and the heat exchanger H between them, and even if the heat exchanger H is installed there, the width of the engine does not increase, which is convenient. In particular, the use of the heat pipe 7 is particularly effective in motorcycles where there is little space and the appearance influences the marketability.

[Brief explanation of drawings]

The figure is a vertical sectional side view of a four-stroke motorcycle engine to which the present invention is applied. 1... Check valve, 2... Carburizer, 3...
...Cylinder block, 4...Cylinder, 5
...Introduction path, 6...Cylinder head, 7...Heat pipe, 8...Exhaust port, 9...Air supply hole, 10,10″...
...Air introduction pipe, H...Heat exchanger.

Claims (1)

[Claims] 1. A system in which secondary air is supplied into the exhaust gas of a cross-flow engine having an exhaust port on one side of the cylinder head and an intake port on the opposite side, and the exhaust gas is purified by re-combustion. In this system, part of the heat of the exhaust gas is transferred to the secondary air in the secondary air supply passage through a heat pipe, and the heated secondary air is supplied to the exhaust port near the exhaust valve. Next air heating method. 2 Connecting one end of the inlet passage provided within the thickness of the cylinder block of a cross-flow engine that has an exhaust port on one side of the cylinder head and an intake port on the opposite side to the discharge port in the exhaust port close to the exhaust valve. Then, connect the intake port at the other end to the clean side of the air cleaner through a check valve that only allows flow to the heat receiving path of the heat exchanger and the intake port side.
A secondary air heating device that connects the inside of the exhaust pipe downstream of the thermal reactor connected to the exhaust port, at a lower position than the heat exchanger, with the heating path of the heat exchanger using a heat pipe.