JPH0573894B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust system structure for an engine that is provided with a heat exchanger for exchanging heat between exhaust gas and water to recover exhaust heat.

(Prior art) In a device that recovers engine exhaust heat and uses it as a heat source for heating or a heat pump circuit, the engine exhaust system structure equipped with a heat exchanger for exhaust heat recovery has conventionally been used, for example, in the 1980s.
As shown in Publication No. 1911, a structure in which the exhaust manifold is surrounded by a water jacket, that is, the exhaust manifold is surrounded by a heat exchange case without interfering with the flow of gas inside the exhaust manifold to form a sealed space. However, there are known devices configured to allow a heat transfer fluid to flow into and out of this closed space.

By the way, in the exhaust manifold as a heat exchanger, the exhaust gas is cooled and moisture in the exhaust gas tends to condense.In that case, highly acidic condensed water is generated, and if this condensed water accumulates in the exhaust manifold, it will cause damage. Internal walls are susceptible to corrosion and holes are easily formed in the walls. In order to improve the heat recovery effect, it has also been proposed to install an additional heat exchanger downstream of the exhaust manifold, but in this case, a large amount of condensed water is generated as a result of heat recovery in the heat exchanger. The above problems become more obvious.

If a hole is created in the exhaust manifold or the wall of the heat exchanger, water for heat exchange may flow into the engine through the exhaust manifold, or exhaust gas may enter the water circuit.

In addition, as an exhaust passage, an exhaust manifold,
The heat exchanger and silencer will be connected in sequence, but while ensuring that the condensed water generated in the heat exchanger does not flow into the silencer and corrode it, the condensed water generated in the silencer should also be connected. Care must be taken to prevent backflow into the heat exchanger, etc. on the upstream side of the exhaust gas.

(Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems. Even if condensed water is generated inside a heat exchanger, it is discharged without accumulating it inside, and the condensed water is An engine that can prevent condensed water from flowing into the silencer and from flowing back into the heat exchanger from the silencer, avoiding corrosion of these parts and improving engine reliability. This provides an exhaust system structure.

(Structure of the Invention) The present invention provides an engine exhaust system structure including a heat exchanger for recovering exhaust heat. The exhaust passage on the downstream side of the exchanger is extended downward, then reversed and extended upward, a silencer is connected to the tip thereof, and a condensed water drain mechanism is arranged at the bottom of the exhaust passage between the heat exchanger and the silencer. It was established.

With this configuration, even if condensed water occurs in the heat exchanger, it will not accumulate inside and will be discharged to the outside through the condensed water drain mechanism, and will also prevent condensed water from flowing into the silencer. This prevents the generated condensed water from flowing back into the heat exchanger side.

(Example) Figures 1, 2, and 3 respectively show the rear, left, and right sides of an engine in which the present invention is implemented. The exhaust manifold heat exchanger has a structure in which the outer periphery of the exhaust manifold is surrounded by a water passage, and the exhaust manifold and the cooling water flow in counterflow. A heat exchanger that exchanges
This heat exchanger 3 is provided on the rear surface of the engine main body 1 at a position lower than the height position of the exhaust manifold heat exchanger 2, and in addition, the connection portion 4 between this heat exchanger 3 and the exhaust manifold heat exchanger 2 is located above the engine body 1, and the heat exchanger 3
The downstream side of the exhaust gas is sloped downward. The connecting portions 4 are flanges 4a and 4b provided on the exhaust manifold heat exchanger 2 and the heat exchanger 3, respectively.
are connected by bolts 5.

Further, an exhaust pipe 6a extending downward is connected to the exhaust outlet 3c provided at the inclined lower end of the heat exchanger 3, and an exhaust pipe line 6b is further connected to the exhaust pipe 6a branching from the middle of the exhaust pipe 6a. . 7 is a condensed water drain mechanism connected to the lowermost end of the exhaust pipe 6a, and 8 is a silencer provided above the heat exchanger 3 into which exhaust gas flows through the exhaust pipe 6b.

A fourth embodiment of the configuration of the condensed water drain mechanism 7 described above is described below.
To explain with reference to Fig. 5, the cylindrical case 7
A float receiving portion 7b is provided near the lower end of a,
A float 7c is housed inside the case 7a so as to be movable up and down, and the float 7c and the drain outlet 7d at the lowermost end constitute a float valve. Further, a level warning sensor 7e is attached near the top of the case 7a, which is activated when the float 7c rises above a predetermined level due to drainage accumulation.

Next, the structure of the heat exchanger 3 will be explained with reference to FIGS. 6 to 8.

The heat exchanger 3 includes an exhaust inlet 3a as an exhaust passage;
It has an exhaust passage 3b and an exhaust outlet 3c, and also has a water inlet 3d as a cooling water passage, a heat exchanger core 3e, a return water passage 3f, and a water outlet 3g. An exhaust passage 3b is located on the outer periphery of the heat exchanger core 3e,
Further, a return water passage 3f is located on the outer periphery of the exhaust passage 3b, so that the exhaust gas and water can exchange heat in a three-layer structure. Further, both the exhaust inlet 3a and the water outlet 3g are provided on the flange 4b and connected to the flange 4a on the exhaust manifold heat exchanger 2 side.

Then, the flow of exhaust gas passes from the exhaust manifold heat exchanger 2 through the connection part 4, through the exhaust inlet 3a, exhaust passage 3b, and exhaust outlet 3c of the heat exchanger 3, and then through the exhaust pipe 6a and exhaust pipe line 6b, The silencer 8 extends from the inlet 8a to the exhaust port 8b. In addition, the flow of cooling water is from the water inlet 3d of the heat exchanger 3 to the heat exchanger core 3e, to the return water passage 3f, to the water outlet 3.
g, flows into the exhaust manifold heat exchanger 2 via the connection part 4, and then flows from the exhaust manifold heat exchanger 2 through the water pipe 9a (FIG. 2) and the water pump 10 to the water inside the engine body 1. The water flows into the jacket, passes through the thermostat and the water pipe 9b, and then reaches the water outlet 9c.

Next, the operation of the configuration of the above embodiment will be explained.

Cooling water flows in from the water inlet 3d of the heat exchanger 3,
The heat exchanger 3 and the exhaust manifold heat exchanger 2 exchange heat with the exhaust gas and recover the exhaust heat,
The water flows into the water jacket in the engine body 1 to cool the engine, reaches a high temperature, and then flows out from the water outlet 9c. This hot water is sent to a radiator installed separately from the engine and used as a heat source for indoor heating, or, although not shown, is used in a compressor for pressurizing refrigerant in a heat pump refrigerant circuit driven by the output shaft of the engine body 1. It is used as a heat source for the outdoor heat exchanger in this heat pump refrigerant circuit. In this way, the hot water is used as a heat source, and the cooled water flows into the water inlet 3d of the heat exchanger 3 again.

Here, in the heat exchanger 3, high-temperature exhaust gas flows in from the exhaust inlet 3a, passes through the exhaust passage 3b,
Heat exchange is performed with water flowing through the heat exchanger core 3e and the return water passage 3f. At this time, a large amount of condensed water is likely to be generated as the exhaust gas is cooled by the cooling water passing through the heat exchanger core 3e, but in the present invention, the generated condensed water is sequentially and reliably passed through the condensed water drain mechanism 7. It is discharged to the outside. Therefore, highly acidic condensed water does not accumulate in the heat exchanger 3, and corrosion of the heat exchanger core 3e and the like can be avoided. For this reason, heat exchanger core 3
This prevents the leakage of cooling water into the exhaust passage 3b or the inflow of exhaust gas into the water circuit due to corrosion caused by holes in the cooling water.

In addition, in this embodiment, the connecting portion 4 between the heat exchanger 3 and the exhaust manifold heat exchanger 2 is connected to the heat exchanger 3.
In addition to being located above, the heat exchanger 3 is provided with the exhaust downstream side, that is, the exhaust outlet 3c side, inclined downward, so that cooling water flows into the exhaust manifold heat exchanger 2 side and enters the combustion chamber of the engine. It is designed to prevent backflow.

Further, in the present invention, the exhaust system is arranged so as to pass through the exhaust pipe 6a extending downward from the exhaust outlet 3c of the heat exchanger 3, and enter the silencer 8 through the exhaust pipe line 6b which inverted and extends upward. Because
The condensed water generated in the heat exchanger 3 is discharged by the condensed water drain mechanism 7 at the bottom, so that the condensed water does not flow into the silencer 8, and the condensed water generated in the silencer 8 is also discharged. The condensed water is discharged by the drain mechanism 7, and is prevented from flowing back into the heat exchanger 3 side. Therefore, corrosion caused by accumulation of condensed water in each part of the exhaust system can be prevented.

In the above embodiment, the heat exchanger 3 has a three-layer structure of exhaust gas and cooling water, but it may also have a two-layer structure in which exhaust gas and cooling water flow in opposite directions.

(Effects of the Invention) As described above, according to the present invention, a heat exchanger for exchanging heat between the exhaust gas and water is provided in the exhaust passage of the engine, and the exhaust passage on the downstream side of the heat exchanger is extended downward, and By inverting and extending upward, installing a silencer at the tip, and installing a condensed water drain mechanism at the bottom of the exhaust passage between the heat exchanger and the silencer, the condensed water generated in the heat exchanger and silencer can be reliably drained. Therefore, corrosion of these exhaust system parts due to condensed water can be effectively prevented.

[Brief explanation of drawings]

Fig. 1 is a rear view of an engine implementing the exhaust system structure of the present invention, Fig. 2 is a left side view of the same engine, Fig. 3 is a right side view, and Fig. 4 is an example configuration of a condensed water drain mechanism. 5 is a top view of the same, and FIG. 6 is a top view of the heat exchanger in the same exhaust system structure.
7 is a sectional view taken along the line in FIG. 6, and FIG. 8 is a sectional view taken along the line ``--'' in FIG. 1...Engine body, 2...Exhaust manifold heat exchanger, 3...Heat exchanger, 3c...Exhaust outlet,
6a...exhaust pipe, 6b...exhaust pipe line, 7...condensed water drain mechanism.

Claims (1)

[Claims] 1. In an engine exhaust system structure equipped with a heat exchanger for recovering exhaust heat, a heat exchanger for exchanging heat between the exhaust gas and water is provided in the exhaust passage of the engine,
The exhaust passage on the downstream side of this heat exchanger is extended downward, then reversed and extended upward, and a silencer is connected to the tip thereof, and a condensed water drain mechanism is installed at the bottom of the exhaust passage between the heat exchanger and the silencer. An engine exhaust system structure characterized by having: