JPH0422023Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an exhaust gas purification device for removing harmful substances emitted from internal combustion engines and the like.

[Conventional technology]

Catalytic converters are installed in the exhaust system of automobile engines in order to remove harmful components such as HC, CO, and _NOx from the exhaust gas emitted from the engine. At this time, a branch part is formed in the exhaust gas pipe, and a low-temperature catalytic converter is connected to one branch pipe, and a high-temperature catalytic converter is connected to the other branch pipe to prevent changes in exhaust gas temperature, such as continuous operation from startup. Techniques for selectively using the catalytic converter by switching the flow of exhaust gas depending on the temperature rise between conditions are known.

[Problem that the invention attempts to solve]

However, conventionally used exhaust gas purification devices control the exhaust gas flow path by focusing only on the heat resistance temperature set in advance for the low-temperature catalyst, so regardless of the presence or absence of deterioration of the low-temperature catalyst, Exhaust gas continues to flow toward the low-temperature catalyst until the temperature of the low-temperature catalyst exceeds the set temperature. For this reason,
There is no problem if the low-temperature catalytic converter has sufficient purification performance, but if the catalyst deteriorates and its purification performance is almost lost, harmful components in the exhaust gas may enter the atmosphere without being purified. It will be released.

The present invention is intended to solve the above-mentioned problems in the conventional technology, and its purpose is to detect the degree of deterioration of the exhaust gas purification performance of the low-temperature catalytic converter and to appropriately operate the switching valve. An object of the present invention is to provide an exhaust gas purification device that prevents the release of harmful components into the atmosphere.

[Means for solving the problem] That is, the exhaust gas purification device of the present invention connects a low-temperature catalytic converter to a branch pipe, connects a high-temperature catalytic converter to the other branch pipe, and connects the low-temperature catalytic converter to the other branch pipe. Temperature sensors are attached to the inlet and outlet sections, and the degree of deterioration in the exhaust gas purification performance of the low-temperature catalytic converter is detected based on signals from the temperature sensors attached to the inlet and outlet sections, and the degree of deterioration of the exhaust gas purification performance of the low temperature catalytic converter is detected. The present invention is characterized in that a flow path switching valve is provided at a branch portion of the piping, which is operated to flow exhaust gas to the low-temperature or high-temperature catalytic converter based on a signal from a control means that makes a judgment regarding the state.

Properties such as the size and shape of the branch portion and the catalytic converter and the number thereof are not particularly limited. It is preferable to select according to the vehicle type.

As the catalyst component, commonly used catalyst components such as platinum, rhodium, palladium, etc. can be used. For example, a computer can be used as the control means that detects the degree of deterioration of the exhaust gas purification performance of the low-temperature catalytic converter based on the signal from the temperature sensor and also makes a judgment regarding the driving state of the vehicle. Then, based on the signal from this computer, the flow path switching valve is operated by, for example, an actuator. Furthermore, components that increase the catalytic activity, such as lanthanum and cerium, may be added.

The type of temperature sensor is not particularly limited, but it is convenient to use a sensor that can convert temperature into an electrical signal, such as a platinum resistor or thermocouple. The installation location is preferably a location where the inlet and outlet gas temperatures at the inlet and outlet of the low-temperature catalytic converter can be accurately determined. The number of units installed may be one each for the inlet and outlet, or a plurality of units may be attached for each to calculate the average temperature for each.

In addition to the temperature sensor, various sensors normally used in vehicles such as automobiles, such as an engine rotation speed sensor and a vehicle speed sensor, can also be used together with the temperature sensor.

The type of flow path switching valve is not particularly limited. Further, one valve may be provided at a suitable position in the branch portion to distribute the exhaust gas to the low-temperature and high-temperature catalytic converters, or it may be provided in each of the branch pipes.

[Effect]

A computer processes signals from temperature sensors installed at the inlet and outlet of the low-temperature catalytic converter, determines the degree of deterioration of the low-temperature catalyst based on the temperature difference between the inflow gas temperature and the outflow gas temperature, and adjusts the temperature as desired. Furthermore, signals from other sensors such as the engine speed sensor and the vehicle speed sensor are input into the computer to determine the driving state of the vehicle, for example, whether it is idling or not, and the actuator operates the switching valve according to a preset program. Activate the converter and switch the exhaust gas to the low-temperature or high-temperature catalytic converter.

〔Example〕

In the following examples, the present invention will be explained in more detail on the basis of the drawings. Note that the present invention is not limited to the following examples.

Embodiment 1: FIG. 1 is a schematic diagram of an embodiment of the exhaust gas purification device of the present invention. In the figure, 1 is the exhaust manifold,
2 is a flow path switching valve, 3 is a low-temperature catalytic converter, 4
is a high temperature catalytic converter, 5 and 6 are temperature sensors, 7 is a computer, 8 is an actuator, 9
10 is the branch piping on the high temperature side, 11 is the branch piping on the low temperature side.
12 indicates an engine speed sensor, and 12 indicates a vehicle speed sensor. The basic operation will be explained below. The temperature sensor 5 detects the inflow gas temperature T1 to the low-temperature catalytic converter 3, the temperature sensor 6 detects the outflow gas temperature T2, and when the condition T1≧T2 is satisfied, the catalyst The computer 7 determines that the outflow gas temperature T2 will not rise because the harmful components have not been purified by
The exhaust gas flows into the high temperature side branch pipe 10. However, it is desirable to make the above judgment on the condition that the low-temperature catalytic converter 3 has been sufficiently warmed up. This determination may be made based on whether the catalyst output gas temperature detected by the temperature sensor 6 has reached a set temperature, for example, 400°C. That is, unless the temperature reaches 400°C, the above operation will not be performed even if the condition T1≧T2 is satisfied. or,
Other conditions may also be set as desired. This condition is, for example, whether the engine is idling or not. By adding this condition, for example, even if the purification performance of the low-temperature catalyst is sufficient, gas intrusion that occurs temporarily during the initial acceleration of the vehicle, etc. Misjudgment due to the reversal phenomenon of the output gas temperature (T1≧T2) can be prevented. That is, the above judgment is made only when the vehicle is idling. Such conditions are not limited to idling, and may be set to prevent erroneous judgments, taking into account, for example, sudden acceleration from steady running. In this embodiment, engine rotation speed and vehicle speed are used to determine whether or not the vehicle is idling. For example, when the engine speed is below 1000 rpm, the vehicle speed is almost 0.
If it is Km/hr, it is determined that the vehicle is idling.

FIG. 2 shows an example of a control program used in the apparatus shown in FIG.

[Effect of idea]

As mentioned above, the exhaust gas purification device of the present invention detects the difference in exhaust gas temperature between the inlet and outlet of the low-temperature catalytic converter, and further takes into consideration the state of the vehicle, such as whether the vehicle is running or stopped, as required. The system determines the degree of deterioration of the catalyst and switches the exhaust gas flow using the flow path switching valve, so even if the catalytic activity of the low-temperature catalytic converter is lost, the flow path can be switched to the high-temperature catalytic converter side. Under temperature conditions where the high-temperature catalyst is sufficiently activated, harmful components in exhaust gas can be prevented from being released into the atmosphere without reducing purification performance.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the exhaust gas purification device of the present invention, and FIG. 2 is a flowchart showing an example of a control program for the exhaust gas purification device of the present invention. In the figure, 1... Exhaust manifold, 2... Flow path switching valve, 3... Low temperature catalytic converter, 4... High temperature catalytic converter, 5, 6... Temperature sensor, 7...
...Computer, 8...Actuator, 9...
Low temperature side branch piping, 10...High temperature side branch piping, 11
...Engine speed sensor, 12...Vehicle speed sensor.

Claims (1)

[Scope of utility model registration request] A low-temperature catalytic converter is connected to the branch pipe, a high-temperature catalytic converter is connected to the other branch pipe, and a temperature sensor is attached to the inlet and outlet of the low-temperature catalytic converter, and a temperature sensor is attached to the inlet and outlet. The degree of deterioration in the exhaust gas purification performance of the low temperature catalytic converter is detected based on a signal from the temperature sensor, and the low temperature or high temperature catalyst An exhaust gas purification device characterized in that a flow path switching valve operated to flow exhaust gas to a converter is provided at a branch part of the piping.