JPH051615Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an exhaust gas purification device for a diesel methanol engine in which a plurality of catalysts and heaters are switched and controlled according to engine conditions.

[Conventional technology]

In general, the exhaust gas components of a methanol engine contain aldehydes and the like, and therefore odor is emitted, especially during light/medium load or startup. For this reason, measures are generally taken to prevent the oxidation of aldehydes and the emission of odors by providing an oxidation catalyst.

However, in the case of a diesel methanol engine, even if an oxidation catalyst as described above is provided, the oxidation catalyst does not operate under light or medium loads because the exhaust gas temperature is low and does not reach the reaction start temperature of the oxidation catalyst. Therefore, the aldehyde is not oxidized and it is difficult to prevent odor from being emitted.

As a further improved exhaust gas purification method, a switching valve is installed on the inlet side of the conventional catalyst device, allowing exhaust gas to flow only to the center of the catalyst during the cold period immediately after startup, and switching the switching valve after it has warmed up sufficiently. Some engines are equipped with a valve operation mechanism that allows exhaust gas to flow to all of the catalysts (Japanese Patent Application Laid-open No. 183511/1983), and others are equipped with an electric heating element in front of the catalyst and operate the electric heating element at the time of startup. (Utility Model Application Publication No. 49-36324) has been proposed.

[Problem that the invention attempts to solve]

However, even if the former method is applied to a diesel methanol engine and the exhaust gas is configured to flow only to the center of the catalytic converter at startup, the reaction will not start due to the low exhaust gas temperature, and the exhaust gas purification effect will be reduced. There is a risk that the switching will not be carried out, and since the switching valve is controlled by temperature,
There is a problem in that it is not possible to appropriately respond to load fluctuations. Furthermore, when the latter method is applied, since the heater is operated only at the time of starting, there is a problem that it is not possible to appropriately respond to load fluctuations, as in the case where the former method is applied.

The present invention was devised to solve the above-mentioned problems in conventional exhaust gas purification devices, and aims to provide an exhaust gas purification device for diesel methanol engines that can appropriately respond to changes in engine speed and load. purpose.

[Means and actions for solving problems]

In order to solve the above problems, the present invention includes a plurality of catalysts arranged in parallel immediately after the exhaust manifold, an electric heater arranged at the inlet of each catalyst, and The exhaust purification system for a diesel methanol engine is comprised of a control unit that switches and controls the number of electric heaters used and controls on/off the electric heaters according to the load condition of the engine.

By configuring the exhaust purification device in this way, the number of catalysts used and the corresponding on/off of the heater are controlled according to the engine speed and engine load, and the exhaust gas is efficiently controlled in an optimal state according to the engine condition. It becomes possible to purify the

〔Example〕

Examples will be described below. FIG. 1 is a partially sectional plan view showing an embodiment of a diesel methanol engine purification device according to the present invention. In the figure, 1 is an engine body, 2 is an exhaust manifold, and 3 is a catalyst device connected and attached to the end of the manifold. The catalyst device 3 has an inlet and an outlet gas passage divided into a plurality of parts in the case body 4, and catalysts 5 _-1 and 5 _-2 are arranged in each divided gas passage 4 _-1 and 4 _-2 , respectively. has been done. Electric heaters 6 _-1 and 6 _-2 are arranged in front of each of the catalysts 5 _-1 and 5 _-2 , respectively, and the gas flow channel 4 _-2 is connected to one of the divided gas flow channels 4 _-2. A switching valve 7 for opening and closing is provided.

8 is an air cylinder for switching the switching valve 7, 9 is a servo valve for controlling the supply of compressed air from the air tank 10 to the air cylinder 8, and 11 is a switching control for controlling the servo valve 9. This is a control unit that outputs signals. In this embodiment, the switching valve 7 is closed when the air cylinder 8 is inactive. Reference numeral 12 denotes a switch section for controlling the heaters 6 _-1 and 6 _-2 , and the switch section 12 is turned on and off by a switch control signal from the control unit 11.
Configured to be controlled off. The control unit 11 receives detection signals R _N and F from the engine rotation sensor and the load sensor, outputs a servo valve switching control signal according to the engine rotation speed, and performs switch control according to the engine load. configured to output a signal.

Next, the operation of the diesel methanol engine exhaust purification device configured as described above will be explained in a second manner.
This will be explained with reference to a flowchart showing the control mode in the control unit 11 shown in the figure. When the engine starts and the detection signals R _N and F are input from the rotation sensor and load sensor, the first step is to set the engine rotation speed R _N to a predetermined set value.
A determination is made as to whether R _S has been reached. If the judgment result is negative, for example, when starting the engine, the engine rotation speed R _N is set to the predetermined set value R _S
If the switching control signal for the servo valve, that is, the switching valve opening signal is not output, the switching valve 7 remains closed, and only one catalyst 5 _-1 acts on the exhaust gas. . On the other hand, if the judgment in this step is positive, a switching control signal for opening the servo valve is output from the control unit 11, the switching valve 7 is operated to open, and as a result, the two catalysts 5 _-
1 and _5-2 , making it possible to handle the large amount of exhaust gas emitted during high-speed rotation.

When any one of these operations is completed, the process proceeds to the next step and it is determined whether the engine load F has reached a predetermined set value F _S or not. If the result of this judgment is negative, that is, at startup or at medium/low load, the control unit 11 outputs a switch control signal, which turns on the switch corresponding to one or two catalysts being used. Heater 6 _-1 or 6 _-1 and 6 _-2 operate. As a result, the low-temperature exhaust gas is heated to a temperature higher than the catalyst operating temperature and introduced into the catalyst, and the exhaust gas is appropriately treated by the action of the catalyst. On the other hand, if the judgment in this step is positive, a heater-off switch control signal is output, and both heaters _6-1 and _6-2 remain off, and the high-temperature exhaust gas during high engine load is not heated. , it is oxidized and purified by the action of a catalyst.

FIG. 3 shows the relationship between the number of catalysts used and the operation of the heater described above, and the engine speed and load. That is, as shown in the figure, in this embodiment, one or two catalysts are used at the engine speed R _S , and the heater is turned on and off at the engine load F _S. Region A is a region where one catalyst is active and the heater is on, and region B is a region where there are two catalysts and both heaters are on.

As described above, the present invention operates the switching valve according to the engine speed and load condition to operate one or two catalysts, and also controls the heater on and off. Therefore, for example, when the engine speed is low and the engine load is low, not only when starting the engine but also under light or medium load conditions, one catalyst is used together with the heater, so even if the exhaust gas temperature is low, A small amount of exhaust gas can be efficiently and sufficiently purified with one catalyst. Furthermore, when the engine speed is high and it is necessary to treat a large amount of exhaust gas, two catalysts are used, and the exhaust gas can be treated sufficiently.

In the above embodiment, two catalysts are arranged in parallel in the catalyst device main body, but the number of catalysts is not limited to two, for example, three catalysts can be arranged in parallel to
It may be configured to be used selectively depending on the engine rotation in three high-speed stages. In this case, the on/off control of the heater is also configured to be controlled in accordance with the load condition and in accordance with the number of catalysts used.

Furthermore, in the above embodiment, two catalysts are integrally arranged side by side in the catalyst device main body, but a plurality of catalysts each housed in an individual case may be arranged side by side to reduce exhaust gas. It can also be configured to be introduced selectively.

[Effects of the invention] As explained above based on the embodiments, according to the invention, a plurality of catalysts are arranged and the number of catalysts used is controlled according to the engine speed.
Using a conventional small monolith type catalyst, it is possible to efficiently process a small amount of exhaust gas to a large amount of exhaust gas, and there is no need to develop and manufacture a new large monolith type catalyst, reducing costs. It has the advantage that it can be reduced. Further, since the catalyst is switched and used depending on the engine speed, the life of the catalyst can be extended.

In addition, a heater was placed in front of each catalyst, so
The exhaust gas temperature is raised during low and medium load conditions to ensure sufficient catalytic action, and the on/off control is performed according to engine load conditions, resulting in reduced power consumption and other benefits. can get.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional plan view showing an embodiment of the exhaust purification device for a diesel methanol engine according to the present invention, and FIG. 2 shows a control mode of the control unit in the exhaust purification device shown in FIG. 1. The flowchart, FIG. 3, is a diagram showing the number of catalysts used and the on/off state of the heater with respect to the engine speed and load state. In the figure, 1 is the engine body, 2 is the exhaust manifold, 3 is the catalyst device, 4 is the catalyst device body, 5
_-1 and 5 _-2 are catalysts, 6 _-1 and 6 _-2 are electric heaters, 7 is a switching valve, 8 is an air cylinder, 9 is a servo valve, 10 is an air tank, 11 is a control unit, 1
2 indicates a heater control switch section.

Claims (1)

[Scope of utility model registration request] A plurality of catalysts are arranged in parallel immediately after the exhaust manifold, and an electric heater is arranged at the inlet of each of the catalysts. 1. An exhaust gas purification device for a diesel methanol engine, comprising: a control unit that controls on/off of the electric heater according to the conditions.