JPH051616Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an exhaust purification device for an internal combustion engine using a catalyst.

[Conventional technology]

In an exhaust gas purification system for an internal combustion engine that uses a catalyst, in order to improve the catalyst purification performance when the engine is cold, the exhaust manifold and the exhaust pipe upstream of the catalyst are kept warm to prevent the temperature of the exhaust gas introduced into the catalyst from decreasing.
Techniques for accelerating catalyst activation are well known.

On the other hand, in order to ensure the durability of the catalyst, the exhaust manifold and the exhaust pipe upstream of the catalyst are cooled with water or air to lower the temperature of the exhaust gas introduced into the catalyst.
A technique for preventing the catalyst from becoming excessively high temperature is also well known (see Japanese Utility Model Application Publication No. 87114/1983).

However, these conventional exhaust purification devices are designed to maintain only the exhaust temperature or reduce the exhaust temperature, so they are not suitable for both when the engine is cold and when the engine is warmed up. In order to solve these problems, the applicant has
Provided an exhaust purification device that could meet the requirements of both cold and warm-up engines (Utility Application 1986-
(See No. 147674).

The exhaust purification device of the above-mentioned Utility Application No. 147674/1986 is the second
As shown in the figure, there is a catalyst 3 in the exhaust passage of the engine.
In an exhaust purification device that purifies exhaust gas by providing a front pipe 2 on the upstream side of the catalyst 3,
has a sealed double pipe structure consisting of an outer pipe 11 and an inner pipe 12, and this outer pipe 11 is connected to the pump 5 via two three-way switching valves 61 and 62. Switching is performed depending on whether the engine is cold or warmed up. When the engine is cold, the air in the space 13 between the outer pipe 11 and the inner pipe 12 is discharged into the atmosphere by the pump 5, and when the engine is warmed up, the air is pumped into the space 13. 5 to supply atmospheric air to cool the exhaust gas passing through the inner pipe 12.

[Problem that the invention attempts to solve]

In the exhaust purification device of Utility Model Application No. 147674/1980, due to its configuration, when the exhaust gas is kept warm when the engine is cold, the hot air around the inner pipe 12 passes through the pump 5. Components inside the pump 5 may receive heat, causing distortion, etc., and there is a possibility that the function of the pump 5 may deteriorate or the durability of the pump 5 may deteriorate.

Furthermore, in the above device, switching valves 61 and 62 are provided on both the outlet 14 side and the inlet 15 side of the outer tube 11, and these two switching valves 61 and 62 are linked, but the operation of these switching valves 61 and 62 varies. There is also the problem that the effect is reduced if it becomes impossible to switch at the same time.

[Means for solving problems]

In order to solve the above problems, the present invention provides an exhaust purification device in which a catalyst is provided in the exhaust passage of an engine to purify the exhaust gas. The outer tube has an outlet and an inlet, and the outlet and inlet are connected by an exhaust circulation circuit equipped with a cooler, a pump, and a three-way switching valve. The directional control valve is switched depending on whether the engine is cold or warmed up, and when the engine is cold, the air in the space between the outer pipe and the inner pipe is discharged by the pump, and when the engine is warmed up, the air in the space between the outer pipe and the inner pipe is discharged by the pump, and when the engine is warmed up, the air in the space between the outer pipe and the inner pipe is discharged by the pump. It is configured to circulate and supply cooling air.

[Effect]

In the present invention having the above configuration, when the engine is cold, the three-way switching valve communicates between the pump and the atmosphere side, blocks the inlet side of the space between the double pipes, and allows the pump to communicate between the inner pipe and the outer pipe. The air in the space between the pipes is exhausted to the atmosphere. At this time, the discharged air first passes through a cooler, where it is cooled and then sucked into the pump, so that the pump is not exposed to hot air and damage to it is prevented. By exhausting the air in the space between the inner tube and the outer tube, the thermal conductivity of this space decreases, thereby preventing a drop in the temperature of the exhaust gas introduced into the catalyst.

After warming up the engine, the three-way switching valve is switched to shut off the atmosphere side, communicate the pump side with the inlet side of the space, and circulate the air in this space by the pump via the cooler. For this reason, since cooled air flows around the outer circumference of the inner tube, the exhaust gas passing through the inner tube is cooled and introduced into the catalyst. In this way, excessively heated exhaust gas is prevented from entering the catalyst during warm-up, thereby avoiding a decrease in the durability of the catalyst.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an exhaust manifold, which is connected to a catalyst 3 via a front pipe 2 on the downstream side thereof, and a center pipe 4 on the downstream side of the catalyst 3. Front pipe 2 has flange 21
The catalyst 3 is connected to the front pipe 2 by flanges 23 and 24, and the center pipe 4 is connected to the catalyst 3 by flanges 25 and 26.

The front pipe 2 is a double pipe with a sealed structure consisting of an outer pipe 11 and an inner pipe 12, and the inner pipe 12 is connected to the exhaust manifold 1 on the upstream side, and the catalyst 3 on the downstream side.
They are connected to each other. A space 13 between the outer tube 11 and the inner tube 12 is connected to an air exhaust pipe 31 and an air introduction pipe 32 via an outlet port 14 and an inlet port 15 provided in the outer tube 11. Further, the air discharge pipe 31 is connected to the cooler 6, and the air introduction pipe 32 is connected to the first port 71 of the three-way switching valve 7, respectively. The cooler 6 is connected to the suction port of the pump 5 via a connecting pipe 61, and the discharge port of the pump 5 is connected to the second port 72 of the three-way switching valve 7.
It is connected to via a connecting pipe 62. 3
A third port 73 of the directional control valve 7 is adapted to communicate with the atmosphere.

Note that the operating mechanism of the cooler 6 may be water cooling or air cooling, or may be a heat exchanger using another medium.

The switching mechanism of the three-way switching valve 7 is configured to be switched by an input signal S. This input signal may be a bimetal switch based on the detection of the engine cooling water temperature, or a controller may be switched based on the exhaust temperature. Alternatively, the switching may be performed using a solenoid valve via a solenoid valve.

The operation of this embodiment configured as described above will be explained.

When the engine is cold, such as when the engine is started, the three-way switching valve 7 allows the pump connection pipe 62 and the atmosphere release passage 73 to communicate with each other, and closes the air introduction pipe 32 side. Therefore, in front pipe 2,
The air existing in the space 13 between the outer tube 11 and the inner tube 12 passes through the cooler 6, is sucked out by the pump 5, and is discharged into the atmosphere from the atmosphere opening passage 73. Therefore, the air in the space 13 becomes thinner and its thermal conductivity decreases, and the exhaust gas flowing inside the inner tube 12 is introduced into the catalyst 3 in a heat-retained state, with the temperature of the exhaust gas flowing inside the inner tube 12 being prevented from decreasing due to heat conduction from the tube wall. Therefore, activation of the catalyst 3 is accelerated and its purification performance is improved.

At this time, since the air in the space 13 is sucked into the pump 5 after being cooled by the cooler 6, the pump 5
The parts of the pump are not strained by hot air, and the durability of the pump is prevented from deteriorating.

When the engine is under high load after warming up, the three-way switching valve 7 is switched in response to the engine cooling water temperature or exhaust temperature detection signal S, and the pump connecting pipe 62 is switched.
and the air introduction pipe 32, and the atmosphere opening passage 73 is closed. Therefore, the air in the space 13 between the outer tube 11 and the inner tube 12 is cooled by the cooler 6 and sucked into the pump 5, and the cooled air is returned to the space by the pump 5 via the air introduction pipe 32. 1
Return within 3. Since the air thus cooled circulates within the space 13, the exhaust gas within the inner pipe 12 is cooled and introduced into the catalyst 3. Therefore, excessive temperature rise of the catalyst 3 is avoided, and its durability is ensured.

In this way, when the engine is cold, the catalyst 3
The warm-up performance of the catalyst is improved, and the emission performance is improved. On the other hand, when the catalyst is under high load after warm-up, excessive hot exhaust gas is not introduced to the catalyst, and the durability of the catalyst is ensured.

Furthermore, since the air sucked into the pump 5 is always at a low temperature, the durability of the pump 5 is not impaired.

The above-mentioned device does not require an interlocking three-way switching valve or a relief valve as in the conventional example, so it has a simple structure and high accuracy.

[Effect of idea]

Since the present invention has the above-described structure and operation, the purification performance of the catalyst is improved by keeping the exhaust gas warm when the engine is cold, and the emission is improved.

Furthermore, when the engine is warmed up and under high load, the exhaust gas is cooled, thereby avoiding an excessive temperature rise in the catalyst, preventing its melting and damage, and improving the durability of the catalyst.

Since cooled air is always sucked into the pump used in the device of the present invention, damage to the pump and reduction in durability due to heat can be prevented.

Furthermore, compared to conventional devices, the number of parts is small, the cost is low, and a reliable exhaust gas purification device can be obtained.

Furthermore, during high load during warm-up, the exhaust capacity is reduced by the drop in exhaust temperature, making it possible to reduce exhaust noise and exhaust backpressure. can do.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the present invention, and FIG. 2 is a schematic diagram of a conventional exhaust gas purification device. 1... Exhaust manifold, 2... Front pipe, 3... Catalyst, 5... Pump, 6... Cooler,
7... Three-way switching valve, 11... Outer pipe, 12... Inner pipe, 13... Space, 14... Outlet port, 15...
...Inlet port, 31...Air exhaust pipe, 32...
... Air introduction pipe, 61, 62 ... Connection pipe, 71, 72, 73 ... 3-way switching valve port.

Claims (1)

[Scope of utility model registration request] In an exhaust purification device in which a catalyst is provided in an exhaust passage of an engine to purify exhaust gas, the range passage on the upstream side of the catalyst has a sealed double-pipe structure consisting of an inner pipe and an outer pipe, and the outer pipe An outlet and an inlet are respectively provided in the engine, and the outlet and inlet are connected by an exhaust circulation circuit equipped with a cooler, a pump, and a three-way switching valve, and the three-way switching valve is connected to the engine when the engine is cold and when the engine is warmed up. the air in the space between the outer tube and the inner tube is discharged by the pump when it is cold, and the pump circulates and supplies cooling air to the space when it is warmed up. Characteristic exhaust purification device.