JPH0623530B2 - Exhaust purification device - Google Patents

Description

The present invention relates to a device for purifying exhaust gas discharged from an engine.

[Prior Art] Exhaust gas from an engine contains a malodorous component (for example, aldehydes), and an adsorbent such as activated carbon is placed in the exhaust system to deodorize the malodorous component.

However, such an adsorbent exclusively adsorbs and removes malodorous components (mainly aldehydes) in exhaust gas, and cannot remove exhaust particulates coexisting with malodorous components.

[Problems to be solved by the invention]

As described above, in the conventional exhaust gas purifying apparatus using the adsorbent, there is a problem that the adsorbent is likely to be clogged with exhaust particulates (particulates), resulting in deterioration of the adsorbent.

Therefore, the problem to be solved by the present invention is to prevent clogging of the odor removing adsorbent.

[Means for Solving Problems] In order to solve the above problems, the present invention provides a particulate trap for removing exhaust particulates exclusively on the upstream side of an adsorbent that adsorbs a malodorous component, and exhausts the adsorbent. It is based on the concept of sending the exhaust gas after removing the particulates, and its structural feature is that the first bypass passage bypassing the exhaust passage of the engine and the second bypass passage downstream thereof are provided. And a particulate trap for collecting exhaust particulates in the first bypass passage, and an adsorbent for adsorbing a malodorous component of exhaust gas in the second bypass passage, respectively. The first and second opening / closing valves, which are opened / closed according to predetermined engine conditions, are provided at the inlets of the bypass passages, and the first opening / closing valve is opened when the second opening / closing valve is opened. It is in the air purifier.

[Work]

In the present invention having the above structure, when the exhaust gas is sent to the adsorbent, it is always sent to the particulate trap upstream of the exhaust gas. Therefore, since the exhaust gas sent to the adsorbent is after the exhaust particulates have been removed, the adsorbent will no longer cause clogging by the exhaust particulates and will perform a sufficient malodorous component adsorption and removal function for a long time. be able to.

〔Example〕

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

The drawings show an embodiment of the invention.

In the figure, reference numeral 1 denotes an engine, and exhaust gas is discharged from an exhaust manifold 5 through an exhaust passage 7 and an exhaust port 8. A temperature detector 3 for detecting the exhaust gas temperature is provided in the exhaust passage 7. The exhaust passage 7 is the temperature detector 3
The first bypass passage 9 is branched off from the downstream side, and the second bypass passage 10 is formed further downstream thereof. Further, opening / closing control valves 15 and 16 whose opening / closing is controlled by the temperature detection signal of the temperature detector 3 are provided at the inlet portions 25 and 26 of the bypass passages 9 and 10, respectively. The on-off control valves 15 and 16 respectively include negative pressure actuators (for example, diaphragm actuators) 19 and 20 and negative pressure switching valves (V
SV) 21 and 22 are connected to the control circuit (CPU) 23, while the temperature detector 3 is also connected to the control circuit 23. In this way, the detected temperature signal S of the temperature detector 3
Based on this signal, t is input to the control circuit 23, and based on this signal, the control circuit 23 sends an operation output signal S ₀ to the negative pressure switching valves 21 and 22 to operate the negative pressure actuators 19 and 20 to open and close the opening / closing control valves 15 and 16. Control.

The VSVs 21 and 22 receive the output signal S ₀ from the CPU 23 and connect the negative pressure working chambers of the negative pressure actuators 19 and 20 to a vacuum pump or an intake negative pressure region (both not shown), and the negative pressure. A second position for opening the working chamber to the atmosphere can be selectively taken. Control valve 15,
Reference numeral 16 designates, for example, the rotary shafts 17 and 18 as the centers of rotation, and a closed position indicated by a solid line and an open position 1 indicated by an imaginary line.
5 ', 16' can be taken. In the second bypass passage 10, an adsorbent 13 that adsorbs malodorous components (aldehydes) in the exhaust gas is arranged. The adsorbent 13 is a monolithic ceramic carrier (usually using cordierite) coated with γ-alumina having a large specific surface area. The shape of the adsorbent 13 is not limited to the monolith shape, and may be, for example, foam, pellet, mesh, or the like, and the adsorbent itself is not limited to the γ-alumina, and porous glass, activated carbon, silica gel, etc.
Any substance may be used as long as it has an adsorption capability.

As described above, the adsorbent 13 adsorbs the malodorous components of the exhaust gas, and cannot remove the exhaust particulates coexisting with the malodorous components. Therefore, the adsorbent 13 is likely to be clogged with exhaust particulates. This is particularly remarkable when the adsorbent is of the type having fine pores.

Therefore, according to the present invention, in the first bypass passage 9 located upstream of the adsorbent 13, a particulate trap 11 known per se for removing exhaust particulates is arranged. The trap 11 is composed of, for example, a honeycomb filter. When the exhaust gas is passed through the adsorbent 13, it is always passed through the particulate trap 11. That is, when the second control valve 16 is opened to open the second bypass passage 10, the first control valve 11 is always opened to open the first bypass passage 9. As a result, since the exhaust gas after the exhaust particulates are removed by the particulate trap 11 is always sent to the adsorbent 13, there is no possibility that the adsorbent 13 is clogged with the exhaust particulates.

Table 1 below shows adsorbent 13 and particulate trap 1.
An example of the operating conditions with No. 1 will be shown.

In Table 1 above, the exhaust temperatures T ₁ , T ₂ , T ₃ , T ₄ , T ₅ each represent a predetermined value, for example, T ₁ <T ₂ <T ₃ <T ₄ <T ₅
Have a relationship. Similarly, the water temperatures t ₁ and t ₂ also represent predetermined values, and t ₁ <T ₂ .

Generally, the adsorbent can no longer exert an adsorbing action at a temperature higher than a predetermined temperature (for example, about 150 ° C. = T ₃ ),
Conversely, the adsorbed components start to desorb. Therefore, the adsorbent starts self-regeneration when the exhaust temperature becomes T ₃ or higher. Further, in order to prevent the adsorbent from being deteriorated by the high temperature exhaust gas, when the exhaust temperature reaches a high temperature of, for example, about 400 ° C. (= T ₄ ), the second control valve 16 is closed to allow the high temperature exhaust gas to pass through the second bypass passage. Don't run into 10.

The particulate trap 11 is generally a heater.
Since the reproducing means such as 11A is provided, the reproducing timing can be controlled by controlling the energizing timing of the heater. That is, regeneration is performed by igniting and burning the exhaust particulates adhering to the honeycomb filter by the heater 11A, but the regeneration timing is not limited to the exhaust temperature as shown in Table 1, but also the engine load speed, engine cooling water temperature or Other parameter signals can also be used. Furthermore, the required operating range of the adsorbent itself is generally a limited range such as idling, but in this range, the generation of fine particles is generally very small, so that the accumulation of fine particles in the honeycomb filter also takes a long time. It will increase gradually.
Therefore, in the present invention, self-regeneration can be performed each time a high-temperature exhaust gas passes without providing a regeneration means such as the heater (or burner) as described above.

In short, according to the present invention, it is sufficient that the particulate trap 11 is always activated when the adsorbent 13 is activated. That is, when the second opening / closing valve 16 is opened, the first opening / closing valve 15
Must be open. The first opening / closing valve 15 does not necessarily have to be closed when the second opening / closing valve 16 is closed.

It is possible to open and close the first opening / closing valve 15 and the second opening / closing valve 16 at exactly the same time, but in that case, one actuator 19 and 20 and one VSV 21 and 22 are provided for both opening / closing valves. It is also possible to make it common.

The VSVs 21 and 22 receive the output signal S ₀ from the CPU 23 and connect the negative pressure working chambers of the negative pressure actuators 19 and 20 to a vacuum pump or an intake negative pressure region (both not shown), and the negative pressure. A second position for opening the working chamber to the atmosphere can be selectively taken. The control valve 15 can be rotated, for example, about a rotary shaft 17 to take a closed position shown by a solid line and an open position shown by an imaginary line.

Instead of directly detecting the temperature of exhaust gas as described above, the temperature of the exhaust gas is detected by the water temperature sensor 50.
_w (exhaust gas temperature is low when the cooling water temperature is low) or whether or not idling (exhaust temperature is low during idling) may be detected, and detection signals thereof may be used in combination. . The idling can be detected by the throttle valve opening sensor 51 (signal S _d ) and the engine speed sensor 52 (signal S _N ). The warm-up state is detected by the water temperature sensor 50.

〔The invention's effect〕

As described above, the present invention is provided with a particulate trap that removes exhaust particulates exclusively upstream of the adsorbent that adsorbs malodorous components of exhaust gas, and the adsorbent is always acted when the adsorbent acts. Since the exhaust gas from which the exhaust particulates have been removed by the particulate trap can be sent to, the conventional problem of clogging of the adsorbent due to the exhaust particulates is solved. As a result, the adsorbent can exhibit its original adsorption function for a long time.

[Brief description of drawings]

 Drawing is a schematic block diagram of one Example of this invention. 1 ... Engine, 3 ... Exhaust gas temperature detector, 7 ... Exhaust passage, 9 ... First bypass passage, 10 ... Second bypass passage, 11 ... Particulate trap, 13 ... Adsorbent, 15 ...... First opening / closing control valve, 16 …… Second opening / closing control valve.

Claims (1)

[Claims] 1. A first bypass for bypassing an exhaust passage of an engine
A bypass passage and a second bypass passage downstream thereof are provided, a particulate trap for collecting exhaust particulates is provided in the first bypass passage, and an adsorbent for adsorbing a malodorous component of exhaust gas is provided in the second bypass passage. First and second opening / closing valves that are respectively arranged and that are opened / closed according to predetermined conditions of the engine are provided at the inlets of the first and second bypass passages, respectively.
An exhaust emission control device characterized in that when the second on-off valve is opened, the first on-off valve is also opened.