JPH0422022Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field]

The present invention relates to an exhaust gas purification device, and in particular,
The present invention relates to an improvement in an exhaust gas purification device for an internal combustion engine that purifies exhaust gas using a low-temperature catalyst and a high-temperature catalyst that are arranged in parallel and is suitable for use in purifying exhaust gas from an engine or the like.

[Conventional technology]

In the catalytic converter used to purify exhaust gas, the catalytic converter is separated into two units and connected in parallel to the exhaust gas distribution system, and each converter is equipped with a low-temperature type catalyst and a high-temperature type catalyst. The technology of selectively using low-temperature type and high-temperature type catalysts depending on the exhaust gas temperature is already a well-known technology. That is,
For example, in Utility Model Application No. 56-156912, an exhaust gas purification system for an internal combustion engine uses two types of catalysts with different characteristics connected in parallel in the exhaust system and selectively flows exhaust gas to one of the catalysts using a switching valve. is proposed.

[Problem that the invention attempts to solve]

However, in the conventional exhaust gas purification system for an internal combustion engine consisting of a catalytic converter equipped with catalysts with different temperature characteristics, the allowable temperature limit will not expand dramatically even if the catalyst is for low temperature or high temperature. Furthermore, if deterioration due to repeated use is taken into consideration, it is difficult to imagine that the purification performance of each catalyst can be maintained permanently. In order to solve the above-mentioned problems, we have already developed
No. 33405 and Utility Model Application No. 51-85108 propose a blower cooling device applied to an internal combustion engine purification device to control the temperature of an exhaust gas purification catalyst. However, with these methods alone, there was a problem in that it was not possible to control the temperatures of the low-temperature catalyst and the high-temperature catalyst to a temperature that would provide optimal purification performance.

[Purpose of invention]

The present invention was devised in view of the above-mentioned conventional problems.
Another object of the present invention is to provide an exhaust gas purification device for an internal combustion engine in which the purification performance of high-temperature catalysts can be quickly demonstrated, and furthermore, the cooling performance of each catalyst is improved, so that the exhaust gas purification performance can be improved. .

[Means to solve the problem]

The present invention is an exhaust gas purification device for an internal combustion engine that purifies exhaust gas using a low-temperature catalyst and a high-temperature catalyst arranged in parallel. a first case and a first case that detects the temperature of the low-temperature catalyst;
a temperature detection means, a first ventilation control mechanism that controls ventilation to the first case according to the temperature detected by the first temperature detection means, a second case that surrounds the high temperature catalyst in a ventilable manner; By comprising a second temperature detection means for detecting the temperature of the high temperature catalyst, and a second ventilation control mechanism for controlling ventilation to the second case according to the temperature detected by the second temperature detection means. The above objective has been achieved.

[Effect]

When purifying exhaust gas using a low-temperature catalyst and a high-temperature catalyst arranged in parallel, the present invention surrounds the low-temperature catalyst and the exhaust manifold in the same space to allow ventilation according to the temperature of the low-temperature catalyst. The ventilation of the first case is controlled, and the ventilation of the second case which surrounds the high temperature catalyst in a ventilable manner is controlled according to the temperature of the high temperature catalyst. Therefore, during the warm-up process, when the exhaust gas is flowing through the low-temperature catalyst at a low temperature, heat radiation is suppressed by the first case, and the temperature atmosphere in the space between the first case and the low-temperature catalyst increases. Since the temperature increases, the warm-up performance of the low-temperature catalyst improves. Furthermore, in the present invention, the first case surrounds the low-temperature catalyst and the exhaust manifold in the same space, so that the heat of the exhaust manifold is quickly transferred to the low-temperature catalyst, thereby ensuring improved warm-up performance. It is something. Furthermore, when the temperature of the low-temperature catalyst increases, ventilation is provided in the first case to prevent the low-temperature catalyst from overheating due to the heat of the exhaust gas or the heat transmitted from the exhaust gas manifold. be able to. On the other hand, while the exhaust gas is flowing to the low-temperature catalyst, the heat of the exhaust gas is transferred from the exhaust gas manifold etc. to the high-temperature catalyst, and the high-temperature catalyst is surrounded by the second case, which suppresses heat radiation. The high temperature catalyst is preheated. Therefore, when the exhaust gas reaches a high temperature and the flow direction of the exhaust gas changes and starts flowing to the high temperature catalyst, the high temperature catalyst can quickly achieve a predetermined exhaust gas purification performance. Furthermore, when the exhaust gas flowing to the high-temperature catalyst becomes even hotter, ventilation may be provided in the second case to increase the amount of heat dissipated from the high-temperature catalyst and enhance the cooling effect. Because you can
Overheating of the high temperature catalyst can be suppressed. As described above, in the exhaust gas purification device for an internal combustion engine to which the present invention is applied, the warm-up of the low-temperature catalyst can be promoted using heat from the exhaust manifold. Furthermore, since the high temperature catalyst is preheated by heat transfer or the like from the manifold, the purification performance of the high temperature catalyst can be quickly obtained. Furthermore, the supply of cooling air can be controlled by each ventilation control valve to avoid overheating of each catalyst when the exhaust gas is hot. In this case, the air for ventilation can be relatively easily ventilated using, for example, the wind from a cooling fan or the wind from a running vehicle. Therefore, in the exhaust gas purification device to which the present invention is applied, each catalyst can be used under optimal temperature conditions, so that not only the exhaust gas purification performance is improved, but also the deterioration of each of the catalysts is reduced. The temperature of the low-temperature and high-temperature catalysts is controlled not only by the thermal energy of the exhaust gas, but also by the heat from the exhaust manifold and the heat dissipated by the cooling air, the catalyst activation starting point on the low-temperature side and the high-temperature side relative to the allowable exhaust gas temperature are controlled. By expanding the usage range of the critical temperature of the catalyst and allowing the catalyst to be used at the optimum temperature, purification performance can be improved and deterioration can be prevented.

【Example】

Hereinafter, embodiments to which the present invention is applied will be described in detail. This embodiment relates to a device for purifying exhaust gas discharged from an engine 10, as shown in FIG. The exhaust gas discharged from the engine 10 passes through the exhaust manifold 12 and flows into a low-temperature catalytic converter 14 containing a low-temperature catalyst or a high-temperature catalytic converter 16 containing a high-temperature catalyst. The low temperature catalytic converter 1
4 and the high temperature catalytic converter 16 are arranged in parallel, and the low temperature catalytic converter 1
4 or the inflow of exhaust gas into the high temperature catalytic converter 16 is controlled by a flow path control valve 18. As shown in FIG. 1, a first case 20 is disposed around the outer periphery of the low-temperature catalytic converter 14 so as to integrally surround the low-temperature catalytic converter 14 so as to allow ventilation from the exhaust manifold 12. Further, a first cooling air passage 22 is provided at one end of the first case 20. Furthermore, the cooling air A is directed toward the first cooling air passage 22 by the cooling fan 26.
is being blown, and the first ventilation control valve 2 is used to introduce and block the cooling air A into the space 30 inside the first case.
8 is provided in the first cooling air passage 22.
Note that 21 is an outlet portion of the ventilation generated by the cooling air A in the first case 20. On the other hand, a second case 32 is installed around the high temperature catalytic converter 16 to allow ventilation.
is provided. Further, a second cooling air passage 34 is provided at one end of the second case 32. Further, cooling air A is blown from the cooling fan 26 toward the second cooling air passage 34, and a second ventilation control valve 38 is operated to introduce and block the cooling air A into the space 36 in the second case. is the second cooling air passage 34
It is located inside. Note that 33 is an outlet portion of the ventilation generated by the cooling air A in the second case 32. The low-temperature converter 14 is provided with a first exhaust temperature sensor 40 that detects the temperature of exhaust gas flowing therein. The signal S1 output from the first exhaust temperature sensor 40 is sent to the computer 4.
2. The computer 42 determines the switching operation of the flow path control valve 18 based on the signal S1, and outputs an operation signal V1 for the flow path control valve 18. The operation signal V1 is input to the actuator 44A. The actuator 44A receives the operation signal V
1, the flow path control valve 18 is operated to switch the direction in which exhaust gas flows into each catalytic converter 14, 16. On the other hand, the computer 42 outputs the signal S1
Accordingly, the opening/closing operation of the first ventilation control valve 28 is determined, and the opening/closing signal V2 of the first ventilation control valve 28 is output. The opening/closing signal V2 is input to the actuator 44B. The actuator 4
4B opens and closes the first ventilation control valve 28 according to the opening/closing signal V2, controls the cooling air A sent from the cooling fan 26, and controls the first case 2.
This is to control the ventilation flowing into the space 30 within the space 30. Here, the high-temperature converter 16 is provided with a second exhaust gas temperature sensor 48 that detects the temperature of exhaust gas flowing therein. A signal S2 output from the second exhaust gas temperature sensor 48 is input to the computer 42. The computer 4
2, the second ventilation control valve 38 is activated by the signal S2.
The opening/closing operation of the second ventilation control valve 38 is determined and the opening/closing signal V3 of the second ventilation control valve 38 is output. The opening/closing signal V3 is input to the actuator 44C. The actuator 44C opens and closes the second ventilation control valve 38 according to the opening/closing signal V3, controls the cooling air A sent from the cooling fan 26, and
This controls the ventilation flowing into the space 36 inside the second case 32. In addition, each outlet part 2 which is an outlet of the cooling air A
Nos. 1 and 33 can have their open ends extended outside the engine room if heat damage or the like in the engine room becomes a problem. The operation of this embodiment will be explained below. First, during the warm-up process, the entire amount of exhaust gas that has passed through the exhaust manifold 12 flows through the low-temperature catalytic converter 14, and the temperature of the exhaust gas promotes early activation of the low-temperature catalyst. In addition, the air layer in the space 30 partitioned by the first case 20 is heated by the heat radiated from the exhaust manifold 12 and stores heat, and furthermore, the air layer in the space 30 partitioned by the first case 20 is heated by the heat radiated from the exhaust manifold 12 and stores heat. Since heat radiation can also be suppressed by the air layer in the space 30, the warm-up performance of the low-temperature catalytic converter 14 is supported. On the other hand, the high temperature catalytic converter 16 is also gradually warmed up by the heat transferred from the exhaust manifold 12. However, each of the low-temperature and high-temperature catalytic converters 14 and 16 is connected to the first case 2.
0, the warm-up of the high-temperature catalyst is slow. Therefore, in the space 36 formed by the second case 32, the high temperature catalytic converter 16
By keeping it warm, the high-temperature catalyst is preheated so that it immediately acts on the exhaust gas immediately after the flow path control valve 18 is switched and the exhaust gas begins to flow to the high-temperature converter 16. Next, when the warm-up process ends and the temperature of the low-temperature catalyst enters the superheat region, the computer 42 receives the signal S1 from the first exhaust temperature sensor 40, and the flow path control valve 1
8 operation signal V1 is output. In response to the operation signal V1, the actuator 44A moves the flow path control valve 18 to close the exhaust gas passage on the low temperature catalytic converter 14 side and open the exhaust gas passage on the high temperature catalytic converter 16 side. By the above operation, the flow of exhaust gas is switched to the high temperature catalytic converter 16 side. Meanwhile, at the same time, the signal S1 from the first exhaust temperature sensor 40 causes the computer 42 to
outputs the operation signal V2 of the first ventilation control valve 28. The actuator 44B is activated by the operation signal V2.
is a cooling air passage 2 that circulates cooling air to the space 30.
The first ventilation control valve 28 that had been blocking the space 30 is also opened, and the cooling air A from the cooling fan 26 and the running air generated when the vehicle is running are introduced into the space 30, thereby controlling the low-temperature catalytic converter 14. Can protect from overheating. It should be noted that the switching operation of the flow path control valve 18 and the opening operation of the first ventilation control valve 28 do not need to be performed at the same time, and each may be performed within a range that can exert the effect of preventing overheating of the catalyst. Further, after the exhaust gas starts to flow into the high temperature catalytic converter 16, the heat load further increases and the high temperature catalytic converter 16 also enters the overheating region.
The computer 42 receives the signal S2 from the second exhaust gas temperature sensor 48 and outputs the operation signal V3 for the second ventilation control valve 38. In response to the operation signal V3, the actuator 44C opens the second ventilation control valve 38 that was blocking the second cooling air passage 34 through which the cooling air A flows into the space 36 partitioned by the second case 32, and the By introducing the cooling air from 26 and the running air into the space 36, the high temperature catalytic converter 16 can be protected from overheating. As explained above, in this embodiment, the thermal energy radiated from the exhaust manifold 12 can be fully utilized effectively, and the ventilation has a high cooling effect, so deterioration of each catalyst can be prevented. In this embodiment, an exhaust gas temperature sensor is provided on the outlet side of each catalytic converter to detect the temperature of each catalyst, so that control is performed accurately. Note that the method for detecting the temperature of each catalyst is not limited to this, but it is also possible to use signals such as exhaust gas temperature at the inlet of the catalytic converter, engine cooling water temperature, engine speed and load, or intake air amount. The temperature of each catalyst may be determined by

[Effect of the idea]

As explained above, according to the present invention, the low-temperature catalyst is quickly warmed up, the high-temperature catalyst is kept at an appropriate temperature by suppressing heat radiation, and the cooling performance of each catalyst is improved. Therefore, the purification performance of exhaust gas can be improved. The temperature of the low-temperature and high-temperature catalysts is controlled not only by the thermal energy of the exhaust gas, but also by the heat from the exhaust manifold and the heat dissipation by the cooling air, the catalyst activation starting point on the low-temperature side and the high-temperature side relative to the allowable exhaust gas temperature are controlled. It is possible to expand the usage range of the critical temperature. Therefore, since each catalyst can be used under optimal temperature conditions, there is little deterioration of each catalyst, and
Furthermore, since the amount of heat can be fully utilized, the purification apparatus as a whole has an excellent effect of being highly economical.

[Brief explanation of the drawing]

FIG. 1 is a sectional view, partially including a block diagram, showing the configuration of an embodiment to which the present invention is applied. 10...Engine, 12...Exhaust manifold, 1
4... Low temperature catalytic converter, 16... High temperature catalytic converter, 18... Flow path control valve, 20... First case, 22... First cooling air passage, 28... First ventilation control valve, 30 , 36... Space, 32... Second case, 34... Second cooling air passage, 38... Second ventilation control valve, 40... First exhaust temperature sensor, 4
2...Computer, 44A, 44B, 44C...
...actuator, 48...second exhaust temperature sensor.

Claims (1)

[Scope of claim for utility model registration] In an exhaust gas purification device for an internal combustion engine that purifies exhaust gas using a low-temperature catalyst and a high-temperature catalyst arranged in parallel, the low-temperature catalyst and the exhaust manifold are ventilated in the same space. a first case that can surround the first case; a first temperature detection means for detecting the temperature of the low-temperature catalyst; and a first case for controlling ventilation to the first case according to the temperature detected by the first temperature detection means. a ventilation control mechanism; a second case surrounding the high-temperature catalyst in a ventilable manner; a second temperature detection means for detecting the temperature of the high-temperature catalyst; An exhaust gas purification device for an internal combustion engine, comprising: a second ventilation control mechanism that controls ventilation to the second case.