JPH0472976B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust gas purification device for a multi-cylinder engine.

(Conventional technology) Nowadays, automobile exhaust gas regulations are becoming stricter.
Various measures have been taken to reduce exhaust gas, one of which is to install a catalytic converter in the middle of the exhaust passage to reduce air pollutants such as HC, CO, and NOx contained in the exhaust gas emitted from the engine. Harmless H ₂ O, CO ₂ , N ₂ , etc. cause chemical changes,
There are ways to purify exhaust gas.

In an engine in which the first and second cylinder groups are arranged on both sides of the crankshaft axis (engine center line), such as a V-type or horizontally opposed piston-type multi-cylinder engine, these cylinder groups First and second exhaust passages connected to the first and second cylinder groups, respectively, are collectively connected to one collective exhaust passage, and the above-mentioned catalytic converter is provided in this collective exhaust passage.

However, in such a structure, due to the configuration of the engine, the meeting position of the first and second exhaust passages is offset toward the second exhaust passage side with respect to the crankshaft axis, avoiding the transmission and the like. (For example, in 1977-
118509), therefore, the length of the first exhaust passage is inevitably longer than the length of the second exhaust passage, and the exhaust gas flowing through the first exhaust passage is transferred to the second exhaust passage. The temperature drop due to outside air cooling is considerably greater than that of the exhaust gas flowing through the passage, and as a result, it is not possible to secure the exhaust gas temperature necessary for activating the catalyst of the catalytic tanverter, making it impossible to effectively purify the exhaust gas. There was a problem that I couldn't do it.

Therefore, it is conceivable to provide a catalytic converter only in the first and second exhaust passages, and to effectively purify the high-temperature exhaust gas using both catalytic converters.

However, with the above configuration, for example, in the case of an engine in which the above engine is mounted in a vehicle, if the length of the exhaust passage is to be shortened, both the above catalytic converters must be disposed in the engine room. Therefore, there is a problem in that the temperature in the engine room becomes high due to the reaction heat of the catalysts of both catalytic converters, and the reliability of various auxiliary devices deteriorates.

(Object of the Invention) The present invention has been made in view of such conventional problems, and is provided in the collective exhaust passage in order to keep the exhaust gas flowing only through the first exhaust passage, which has a long passage length, warm. Exhaust gas from a multi-cylinder engine that ensures the exhaust gas temperature necessary to increase the activation of the catalyst in the catalytic converter and effectively purifies the exhaust gas without deteriorating the reliability of the various auxiliary devices mentioned above. The present invention provides a purification device.

(Structure of the Invention) In the exhaust gas purification device of the present invention, a first cylinder group and a second cylinder group are arranged on both sides of the crankshaft axis, and the first cylinder group and the second cylinder group A first exhaust passage and a second exhaust passage are connected to each other, and the first exhaust passage and the second exhaust passage are offset toward the second exhaust passage with respect to the crankshaft axis. In a multi-cylinder engine such as a V-type or horizontally opposed piston type engine, which is connected to a collective exhaust passage at a position where the collective exhaust passage is equipped with a first catalytic converter, the passage length is longer than that of the second exhaust passage. A catalytic converter, in which a three-way catalyst or the like is enclosed as a second catalyst, is interposed only in the middle of the long first exhaust passage.

(Example) Hereinafter, an example according to the present invention will be described based on the drawings.

The engine 1 is a V-type 6-cylinder engine, and has a first cylinder group 2 and a second cylinder group 3, which have three cylinders (not shown) arranged on both sides of the engine center axis, that is, the crankshaft axis A. are placed respectively. A first intake manifold 5 and a second intake manifold 6 connected to the carburetor 4 are communicated with the air intake ports (not shown) of the first and second cylinder groups 2 and 3, respectively. A first exhaust manifold 7 and a second exhaust manifold 8 are communicated with the exhaust port (not shown), respectively. First exhaust manifold 7
The exhaust passage 9 of the second exhaust manifold 8, the exhaust passage 10 of the second exhaust manifold 8, and the exhaust passages 9' and 10' connected to the respective downstream ends of the exhaust passages 9 and 10 are The first exhaust passage 9A and the exhaust passages 10 and 10' constitute the second exhaust passage 10A, and the first and second exhaust passages 9A and 10A form one collective exhaust passage. A first catalytic converter 12 is provided at a position outside the engine room of the collective exhaust passage 11, which includes an oxidation catalyst for purifying two components, HC and CO, as a catalyst.
In order to avoid the transmission 13, the collective exhaust passage 11 is offset with respect to the crankshaft axis A and is arranged on the same axis as the second exhaust passage 10A. Gathering part 1 where exhaust passages 9A and 10A gather
It is located downstream of 1A.

In addition, a catalyst such as HC, CO,
A second catalytic converter 14 containing a three-way catalyst that purifies the three components of NOx is interposed, and in response to this, the engine 1 adjusts the air-fuel ratio on the first cylinder group 2 side to near the stoichiometric air-fuel ratio. The air-fuel ratio control circuit 15 is provided for controlling the air-fuel ratio. Air-fuel ratio control circuit 15
receives a signal from the O ₂ sensor 16 installed in the first exhaust passage 9A upstream of the catalytic converter 14, sends a control signal based on this signal to the control solenoid valve (not shown) of the carburetor 4, and It is configured to control the amount of bleeding, etc.

On the other hand, a reed valve 17 for supplying secondary air to the catalytic converter 12 of the collective exhaust passage 11 is provided on the upstream side of the second exhaust passage 10A. In addition, the second cylinder group 3 is equipped with an EGR (exhaust gas recirculation) system 18 to suppress the generation of NOx.
is provided, and the EGR passage 1 of the EGR system 18 is
9 communicates with the first exhaust manifold 7 and the second intake manifold 6. 20 is an EGR valve for controlling the EGR amount.

Thus, the exhaust gas exhausted from the engine 1 is exhausted through the first and second exhaust manifolds 7, 8, respectively, but the exhaust gas from the first cylinder group 2 is exhausted through the first exhaust passage 9A. The second catalytic converter 14 and the first catalytic converter 12 in the collective exhaust passage 11 sequentially purify and exhaust the exhaust gas, while the exhaust gas from the second cylinder group 3 is purified by the first catalytic converter 12. be discharged.

The exhaust gas purification device of the present invention can be applied not only to the above-mentioned V-type engine 1 but also to other multi-cylinder engines that have the same exhaust passage connection structure, such as horizontally opposed piston engines, and can also be applied to It can be applied to fuel injection type as well as equipped type. Further, the catalyst sealed in the first catalytic converter 14 may be an oxidation catalyst or a reduction catalyst in addition to a three-way catalyst, and similarly, the catalyst sealed in the second catalytic converter 12 may be a three-way catalyst or a three-way catalyst, in addition to an oxidation catalyst. A reduction catalyst may also be used.

(Effects of the Invention) As described in detail above, the present invention provides a second catalytic converter only in the first exhaust passage, which has a longer passage length, out of the first and second exhaust passages that are combined into a common exhaust passage. is provided, the second catalytic converter purifies the exhaust gas flowing through the first exhaust passage and also keeps the exhaust gas warm, thereby reducing the exhaust gas flowing into the collective exhaust passage. The temperature does not drop, and the purification rate of exhaust gas by the first catalytic converter provided in the collective exhaust passage is significantly improved without deteriorating the reliability of various auxiliary devices of the engine.

[Brief explanation of the drawing]

The drawing is a partially cutaway plan view showing an embodiment of a multi-cylinder engine equipped with an exhaust gas purification device according to the present invention. 1...Engine, 2...Cylinder group (first), 3...
...Cylinder group (second), 9A...Exhaust passage (first), 1
0A...exhaust passage (second), 11...collective exhaust passage,
12...first catalytic converter, 14...second catalytic converter, A...crankshaft axis.

Claims (1)

[Claims] 1 A first cylinder group and a second cylinder group are respectively arranged on both sides of the crankshaft axis,
a collective exhaust passage at a position where a first exhaust passage and a second exhaust passage connected to the first cylinder group and the second cylinder group, respectively, are offset toward the second exhaust passage with respect to the crankshaft axis; A multi-cylinder engine in which the collective exhaust passage is provided with a first catalytic converter, wherein a second catalytic converter is interposed only in the first exhaust passage. Engine exhaust gas purification device.