JPH0518236A - Exhaust gas purification device for automobile - Google Patents

Abstract

PURPOSE:To provide an exhaust gas purification device for an automobile which can efficiently purify combustible hydrocarbon included in exhaust gas. CONSTITUTION:An exhaust gas purification device for an automobile has an underfloor catalyst unit 3 inserted into an exhaust gas pipe passage 2 extending from an engine 1, an auxiliary catalyst unit 7 having a heater which oxidizes and purifies at least combustible hydrocarbon included in the exhaust gas, and is inserted into the exhaust gas pipe passage 2 downstream from the underfloor catalyst unit 3, and an adsorbing agent unit 9 which is inserted in the exhaust gas pipe passage 2 on an immediately upstream side of the auxiliary catalyst unit 7, and adsorbs combustible hydrocarbon included in the exhaust gas mainly in an adsorption temperature range not higher than a specified temperature, while removes adsorbed combustible hydrocarbon mainly in a removal temperature range exceeding the specified temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a purifying device for purifying exhaust gas of an automobile, and more particularly to an exhaust gas purifying device for automobile for purifying a large amount of unburned hydrocarbons discharged immediately after the engine is started. Regarding

[0002]

2. Description of the Related Art In an automobile having an engine mounted on the front of the vehicle body, an exhaust gas pipe from the engine extends under the floor of the vehicle body to a rear portion of the vehicle body. This exhaust gas pipe is equipped with an exhaust gas purifying device for purifying harmful gas in the exhaust gas, and this exhaust gas purifying device usually comprises an underfloor catalyst unit inserted in the middle of the exhaust gas pipe. The underfloor catalyst of this underfloor catalyst unit is what is called a three-way catalyst, and this underfloor catalyst contains carbon monoxide (CO), unburned hydrocarbons (HC) and nitrogen oxides (NOx) contained in the exhaust gas. ) Has the function of purifying at the same time.

[0003]

By the way, the above-mentioned underfloor catalyst unit cannot exhibit its original purifying function unless the underfloor catalyst temperature has reached a predetermined activation temperature. Therefore, in order to quickly raise the temperature of the underfloor catalytic unit to the activation temperature by utilizing the heat of the exhaust gas, it is preferable to insert the underfloor catalytic unit at a position close to the engine side in the exhaust gas pipeline. However, if the underfloor catalyst unit is too close to the engine, the underfloor catalyst of the underfloor catalyst unit is overheated by the exhaust gas and is likely to deteriorate. From this, the underfloor catalyst unit is inserted in the exhaust gas pipeline at a predetermined distance from the engine in consideration of the time required to reach the activation temperature and its deterioration, and therefore, It takes some time for the underfloor catalyst to be heated to the activation temperature from the start.

Therefore, the purifying action of the underfloor catalyst does not function effectively during the period from the start of the engine to the activation temperature of the underfloor catalyst unit. Will not be purified by and will pass through this underfloor catalyst unit as it is. Here, a large amount of HC in the exhaust gas is generated immediately after the engine is started, and moreover, when the engine is in a cold state, the amount of HC in the exhaust gas is further increased. It is released, which is not preferable.

The present invention has been made based on the above-mentioned circumstances, and an object thereof is to exhaust gas of an automobile capable of effectively purifying a large amount of HC generated in the exhaust gas immediately after the engine is started. To provide a purification device.

[0006]

The exhaust gas purifying apparatus for an automobile according to the present invention is provided with an underfloor catalyst unit inserted in an exhaust gas pipeline, and an underfloor catalyst unit positioned downstream of the underfloor catalyst unit to be inserted into the exhaust gas. Of the auxiliary catalyst unit with a heater that can oxidize and purify at least unburned hydrocarbons, and is inserted in the exhaust gas pipe located immediately upstream of this auxiliary catalyst unit, and mainly in the adsorption temperature range below a predetermined temperature An adsorbent unit with a heater for adsorbing unburned hydrocarbons therein and mainly desorbing adsorbed unburned hydrocarbons is provided in a desorption temperature region region above a predetermined temperature.

Further, the exhaust gas purifying apparatus is preferably equipped with a control means for controlling the energization of the heaters of the auxiliary catalyst unit and the adsorbent unit, and the adsorbent unit and the underfloor catalyst unit are provided in the exhaust gas pipeline. It is preferable to provide an air supply port that is located between the two and allows the air to be introduced into the exhaust gas pipeline.

[0008]

According to the above exhaust gas purifying apparatus, even if the underfloor catalyst unit does not reach the activation temperature at the time of starting the engine, the HC in the exhaust gas that has passed through the underfloor catalyst unit
Are adsorbed by the adsorbent of the adsorbent unit. If the heater of the auxiliary catalyst unit is energized and the auxiliary catalyst is activated at the time of starting the engine or before starting,
After that, even if the adsorbent temperature of the adsorbent unit rises to the desorption temperature region and the HC adsorbed by the adsorbent is released, this HC is purified by the auxiliary catalyst of the already activated catalyst unit. Will be.

The control means described above controls the energization of each heater of the auxiliary catalyst unit and the adsorbent unit as follows. That is, before the exhaust control system of the engine reaches the normal operating state, for example, before the air-fuel ratio control of the engine is started, or before the catalyst of the underfloor catalyst unit is heated by the exhaust gas and reaches the activation temperature. The control means starts energizing the heater in the auxiliary catalyst unit to raise the auxiliary catalyst of the auxiliary catalyst unit to its activation temperature. Until the auxiliary catalyst unit reaches the activation temperature, the adsorbent temperature of the adsorbent unit is in the adsorption temperature region, and HC in the exhaust gas is adsorbed by the adsorbent unit.

In such a situation, when the catalyst temperature of the auxiliary catalyst unit reaches the activation temperature, at this time point, the control means energizes the heater of the adsorbent unit to heat the adsorbent. When the adsorbent temperature of the adsorbent unit reaches the desorption temperature region, the HC adsorbed by the adsorbent begins to desorb. At this time, however, the catalyst of the auxiliary catalyst unit has already been activated, so it is removed from the adsorbent. The separated HC will be purified by the auxiliary catalyst unit.

After that, when the exhaust control system of the engine reaches the normal operating state, the control means stops the energization control of each heater in the auxiliary catalyst unit and the adsorbent unit after a predetermined time has elapsed. After the adsorbent of the adsorbent unit reaches the desorption temperature region, the control means may further control the energization of the heater to heat the adsorbent to the regeneration temperature.

Further, in the exhaust gas pipeline, if an air supply port is provided between the underfloor catalyst unit and the adsorbent unit, the air introduced into the exhaust gas pipeline through this air supply port is the auxiliary catalyst. It is effectively used for the oxidation of HC in the unit, and this air also serves to lower the temperature of the exhaust gas passing through the adsorbent unit.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, there is schematically shown a vehicle equipped with an engine 1 at the front of the vehicle body. The vehicle has an exhaust gas pipe 2 extending from the engine 1 to the rear of the vehicle body under the floor of the vehicle body. ing. An exhaust gas purifying apparatus according to one embodiment is incorporated in the exhaust gas pipeline 2, and the exhaust gas apparatus includes an underfloor catalyst unit 3. The underfloor catalyst unit 3 is inserted in the exhaust gas pipe 2 on the engine 1 side and supported on the vehicle body side. For example, a three-way catalyst is built in the underfloor catalyst unit 3, and when the three-way catalyst is activated, CO, H in the exhaust gas
It is possible to purify C and NOx at the same time.

In the exhaust gas line 2, an exhaust bellows 4 is inserted immediately upstream of the underfloor catalyst unit 3, and a primafla 5 is inserted immediately downstream of the underfloor catalyst unit 3. Has been done. Exhaust bellows 4 is engine 1
This is for absorbing the relative displacement between the portion of the exhaust gas pipeline 2 on the side and the portion of the exhaust gas pipeline 2 on the vehicle body side.

Further, a main muffler 6 is connected to the downstream end of the exhaust gas pipe 2, and the main muffler 6 is arranged below the trunk room 13 of the vehicle body. Then, in the exhaust gas pipeline 2, the auxiliary catalyst unit 7 is located near the trunk room 13, that is, immediately upstream of the main muffler 6.
Has been inserted. In the auxiliary catalyst unit 7, an auxiliary catalyst that oxidizes and purifies mainly unburned hydrocarbons (HC) of a metal type and a catalyst heater 8 for heating the auxiliary catalyst are incorporated. The purification efficiency of HC with respect to the temperature of the auxiliary catalyst is shown in FIG. 2, and in this example, the activation temperature of the auxiliary catalyst is shown as Ts0.

Further, an adsorbent unit 9 is inserted in the exhaust gas pipe 2 in the vicinity of the trunk room 13, that is, immediately upstream of the auxiliary catalyst unit 7. The adsorbent unit 9 includes, for example, a zeolite adsorbent and an adsorbent heater 10 for heating the adsorbent. As shown in FIG. 3, the adsorbent mainly adsorbs HC when it is in the adsorption temperature range of Tk0 or lower, whereas when it reaches the desorption temperature range that exceeds Tk0, the adsorbed HC is desorbed. It has the property of separating.

The catalysts of the auxiliary catalyst unit 7 and the adsorbent unit 9 and the adsorbent heaters 8 and 10 are electrically connected to a controller 11 which constitutes a control means. The energization is controlled. That is, the controller 12 is connected to the battery 12 that supplies power to the catalyst and adsorbent heaters 8 and 10, while the heaters 8 and 1
Various sensors used for controlling energization to 0 are respectively connected. The battery 12 is the trunk room 13 of the vehicle body.
It is a large one placed in the controller 1
1 is also arranged in the trunk room 13 or in the vicinity of the trunk room 13. Therefore, the battery 12
To the catalyst heater 8 and the adsorbent heater 10 have a short power supply path, and thus the reduction of the power supply voltage to the catalyst and the adsorbent heaters 8 and 10 supplied from the battery 12 can be suppressed to a minimum.

On the other hand, the sensor connected to the controller 11 is a sensor for detecting the bed temperature of the auxiliary catalyst in the auxiliary catalyst unit 7, that is, the catalyst temperature sensor 14, and the bed temperature of the adsorbent in the adsorbent unit 9. Sensor for detecting the temperature, that is, adsorbent temperature sensor 15, and catalyst temperature sensor 1 for detecting the bed temperature of the catalyst in the underfloor catalyst unit 3.
6 and the door open switch 17 for detecting that the door on the driver's side of the automobile is opened.

Further, the exhaust gas pipeline 2 is provided with an air supply port 18 located immediately upstream of the adsorbent unit 9, and the air supply port 18 has one end of a secondary air supply pipeline 19. Are connected. This secondary air supply line 1
The other end of 9 is connected to the intake passage 20 of the engine 1, and a control valve 21 for opening and closing the secondary air supply pipe 19 is inserted in the middle of the secondary air supply pipe 19. ing. The control valve 21 is electrically connected to the controller 11 described above, and its operation is controlled based on a command signal from the controller 11.

The intake passage 20 is provided with a fuel injection valve 22 for injecting fuel into the combustion chamber of the engine 1, while
An oxygen sensor 2 is provided at a portion of the exhaust gas pipe 2 on the engine 1 side.
3 is provided. These fuel injectors 2
2 and oxygen sensor 23 are electronic control units (ECU)
24, so that the operation of the fuel injector 22 is controlled by a command signal from the ECU 24, and the oxygen concentration in the exhaust gas detected by the oxygen sensor 23 is supplied to the ECU 24. It has become. In the case of this embodiment, the ECU 24
It is electrically connected to the controller 11.

Next, the operation of the above-described exhaust gas purifying apparatus, that is, the exhaust gas purifying control routine by the controller 11, will be described with reference to the flowcharts of FIGS. 4 and 5. Exhaust Gas Purification Control Routine First, in step S1 of FIG. 4, it is determined whether or not the door open switch 17 has been turned on, and the determination here is negative (N
If it is O), step S1 is repeated. That is, the controller 11 is in a standby state until the determination result of step S1 becomes positive (YES).

When the result of the determination in step S1 is positive, it can be determined that the driver gets into the automobile and starts the engine 1. At this point, the process proceeds to the next step S2, and each of the steps described later will be performed. The flags are reset to 0 respectively. It should be noted that the determination in step S1 is made by the engine 1
It can also be carried out by whether or not an ignition key (not shown) is turned on.

From step S2 to step S3,
Based on the sensor signals from the catalyst temperature sensor 14 and the adsorbent temperature sensor 15, the auxiliary catalyst temperature Ts and the adsorbent temperature Tk are read into the controller 11, respectively. In the next step S4, it is determined whether or not the flag F1 is set to 1. However, since the determination result is negative at this point, the process proceeds to step S5, and the auxiliary catalyst unit 7
The catalyst heater 8 is turned on. That is, the energization of the catalyst heater 8 is started at this point.

When the catalyst heater 8 is energized as described above, in the next step S6, it is judged whether or not the secondary air can be supplied to the exhaust gas pipe 2, and this judgment is positive. In this case, the control valve 21 is opened in step S7,
As a result, the secondary air is supplied to the exhaust gas pipeline 2. On the other hand, if the determination result in step S6 is negative, the control valve 21 is closed and the supply of secondary air to the exhaust gas pipeline 2 is stopped by performing step S8. Here, the determination in step S6 is made based on, for example, the auxiliary catalyst temperature Ts, and specifically, when the auxiliary catalyst temperature Ts reaches or exceeds a predetermined temperature, the determination result is negative.

From step S7 or S8, step S
At 9, it is determined whether or not the flag F1 is set to 1. However, even at this time, the determination result is negative, so the determination at the next step S10 is performed. In this step, it is determined whether or not the auxiliary catalyst temperature Ts has exceeded the activation temperature Ts0 shown in FIG. 2. If the determination result here is negative, the process returns to step S3, and the steps following this step are performed. Is repeated. Therefore, in such a situation, the catalyst heater 8 is kept turned on, and the auxiliary catalyst of the auxiliary catalyst unit 7 is
The catalyst heater 8 continues to be heated.

After that, when the engine 1 is already driven, in addition to the heating by the exhaust gas, the auxiliary catalyst is heated by the catalyst heater 8 described above,
If the temperature Ts exceeds the activation temperature Ts0 and, as a result, the determination result of step S10 becomes positive, the next step S1 is performed.
At 1, the flag F1 is set to 1. Step S1
From step 1, the process proceeds to step S12 in FIG. 5, in which the adsorption heater 10 of the adsorbent unit 9 is turned on. That is, at this point, the energization of the adsorption heater 10 is started, so that the adsorbent is heated by the adsorption heater 10.

At the next step S14, whether or not the exhaust system of the engine 1 has reached a normal operating state, specifically, the air-fuel ratio (A / F) control of the engine 1 is started, or It is determined whether or not the catalyst of the underfloor catalyst unit 3 has reached its activation temperature. Here, whether or not the A / F control is started can be determined based on the signal supplied to the controller 11 from the above-described ECU 24, while whether or not the underfloor catalyst unit 3 has been activated. Can be determined based on the sensor signal from the catalyst temperature sensor 16 described above.

If the determination result in step S14 is negative, the process returns to step S3, and the steps from step S14 to step S14 are repeated, but in this case, the flag F1 is already set to 1. Since it has been set, step S5 is used instead of step S5 described above.
15 is performed, and step S10 is bypassed and implemented. In step S15, the temperature Ts of the auxiliary catalyst of the auxiliary catalyst unit 7 is the activation temperature Ts0.
Thus, the energization of the catalyst heater 8 is feedback-controlled so as to be maintained at.

Therefore, the auxiliary catalyst temperature Ts of the auxiliary catalyst unit 7 once reaches the activation temperature Ts0 and the adsorbent heater 10
When the energization of the auxiliary catalyst temperature Ts is started, the auxiliary catalyst temperature Ts is maintained at the activation temperature Ts0 because step S15 is repeatedly performed until the determination result of step S14 becomes positive. On the other hand, the adsorbent of the adsorbent unit 9 is heated by the exhaust gas,
Will continue to be heated. Therefore, thereafter, the adsorbent temperature Tk rises above the temperature Tk0 from the above-mentioned adsorption temperature region and reaches the desorption temperature region.

As is apparent from the above description, step S
After the determination result of 1 becomes positive and before the determination result of step S14 becomes positive, even if the underfloor catalytic unit 3 is not activated, the underfloor catalytic unit 3 is passed through as it is. The HC to be adsorbed is adsorbed by the adsorbent of the adsorbent unit 9 which is still in the adsorption temperature region. Then, when the determination result of step S1 becomes positive, the energization of the catalyst heater 8 is immediately started. Therefore, before the temperature Tk of the adsorbent reaches its desorption temperature region, the auxiliary catalyst of the auxiliary catalyst unit 7 is The activation temperature Ts0 is quickly raised.

After that, when the auxiliary catalyst temperature Ts reaches the activation temperature Ts0, the energization of the adsorption heater 10 is started, so that the temperature Tk of the adsorbent in the adsorbent unit 9 becomes
Immediate transition from the adsorption temperature region to the desorption temperature region. Therefore, when the auxiliary catalyst unit 7 is already activated,
Even if the adsorbent temperature Tk of the adsorbent unit 9 reaches the desorption temperature region and the HC adsorbed by the adsorbent begins to desorb from the adsorbent, the HC is oxidized and purified by the auxiliary catalyst of the auxiliary catalyst unit 7. Will be done.

On the other hand, if the result of the determination in step S14 becomes positive, the steps after step S15 are first executed here. That is, in step S15, the controller 1
A timer (not shown) in 1 is activated to start time counting, and in the next step S16, in step S1
It is determined whether or not the elapsed time ta after the determination result of 4 becomes positive reaches the predetermined time t1. If the determination result here is negative, the process returns to step S3 again and the above steps are repeated. However, if the determination result is positive, steps S17 to S20 are sequentially performed, so that The control valve 21 is switched to the closed position, the adsorption and catalyst heaters 8 and 10 are turned off, that is, the energization is stopped, and the exhaust gas purification routine is ended.

Here, in the situation where the determination result of step S14 is positive, the A / F control is started or the underfloor catalyst unit 3 is already activated.
Although HC in the exhaust gas flowing through the exhaust gas pipe 2 is in a reduced state, or even if HC is present in the exhaust gas, this HC can be purified by the already activated underfloor catalyst unit 3. There is. Therefore, in such a situation, since the auxiliary catalyst unit 7 and the adsorbent unit 9 are substantially unnecessary, the energization control to the adsorption heater 10 and the catalyst heater 8 can be stopped in steps S18 and S19. .

The energization control to the adsorption heater 10 and the catalyst heater 8 can be stopped immediately when the determination result of step S14 becomes positive, however, however,
As in the above-described embodiment, it is preferable to stop the energization control to the heaters 10 and 8 after a lapse of a predetermined time t1 from when step S14 becomes positive. That is, even when the result of the determination in step S14 becomes positive, some HC may still be adsorbed by the adsorbent of the adsorbent unit 9, so that the HC is completely desorbed from the adsorbent. If the time required for the above, that is, the predetermined time t1 is secured, all of the HC adsorbed by the adsorbent can be oxidized and purified by the auxiliary catalyst unit 7.

In the above embodiment, the secondary air can be introduced into the exhaust gas pipe 2 from a portion immediately upstream of the adsorbent unit 9. Therefore, the secondary air is supplied by the secondary air. A sufficient amount of oxygen supplied to the auxiliary catalyst unit 7 is ensured, and purification of HC by oxidation can be efficiently performed. Further, from this fact, the combustion of HC becomes good in the auxiliary catalyst unit 7, and the time required to reach the activation temperature Ts0 can also be shortened by effectively utilizing the combustion heat. .

On the other hand, the secondary air introduced into the exhaust gas pipe 2 eventually lowers the temperature of the exhaust gas flowing in the adsorbent unit 9, so that the temperature rise of the adsorbent in the adsorbent unit 9 is delayed. be able to. Therefore, the adsorbent can stay in the adsorption temperature region for a long time, and the HC adsorption time can be sufficiently secured. In addition, in one embodiment, the secondary air is supplied to the exhaust gas pipeline 2 by using the intake negative pressure. However, by using the pneumatic pump and the injection nozzle, the secondary air is supplied to the exhaust gas pipeline. May be injected.

Auxiliary catalyst unit 7 and adsorbent unit 9
Is inserted in the portion of the exhaust gas pipeline 2 that is far from the engine 1 as described above, these units 7,
The auxiliary catalyst and adsorbent of No. 9 are not exposed to high temperature exhaust gas, and the heat resistance level required for these auxiliary catalyst and adsorbent can be lowered. The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, referring to FIGS. 6 and 7, a modified example of the exhaust gas purification control routine is shown.
5 is a part of the exhaust gas purification control routine of one embodiment, that is, is executed instead of the flowchart of FIG.

In the flow chart of FIG. 6, steps S21 and S are performed prior to the execution of step S12 described above.
22 is carried out. In these steps, flag F
3, it is determined whether or not 1 is set in F2,
At this point in time, the flags F3 and F2 are both reset to 0, so that the adsorption heater 10 is turned on in the next step S12. Therefore, also in the case of this modification, when the result of the determination in step S10 in FIG. 4 is positive, step S12 is immediately executed to start energizing the adsorption heater 10.

Thereafter, the process proceeds from step S12 to the next step S23, in which the adsorbent temperature Tk is reached.
Determines whether or not the desorption temperature Tk1 higher than the temperature Tk0 dividing the adsorption temperature region and the desorption temperature region described above is exceeded. If the determination result here is NO, the process returns to step S3 in FIG. 4 and the steps after this step are performed as described above.

When the determination result of step S23 becomes positive,
After the flag F2 is set to 1 in the next step S24, the timer in the controller 11 is activated to start the time counting in the step S25, and in the next step S26, the determination result of the step S23. It is determined whether or not the elapsed time tb after becoming positive reaches a predetermined time t2 (≧ 0).

If the result of the determination in step S26 is negative, the process returns to step S3 in FIG. 4 and the steps after this step are executed. Here, after this,
When the determination in step S22 is performed, the determination result is positive, so in this case, instead of step S12, the process proceeds to step S24 via step S27.

In step S27, the energization of the adsorption heater 10 is feedback-controlled so that the adsorbent temperature Tk is maintained at the desorption temperature Tk1. After this, step S
If the result of the determination at 26 is positive, the flag F3 is set to 1 in step S28, and then the process proceeds to step S29 shown in FIG. 7, in which the flag F4 is set to 1
It is determined whether or not it is set to. Again, since the determination result is negative, the process proceeds to the next step S30, the adsorption heater 10 is turned on, and in step S31, the adsorbent temperature Tk is, for example, 500 ° C. or higher. It is determined whether (> Tk1) has been reached.

If the result of the determination in step S31 is negative, the process returns to step S3 in FIG. 4, and the steps after this step are repeatedly executed. Here, again,
When the determination in step S21 is performed, the determination result is positive. Therefore, from step S21, the process jumps to step S29 in FIG. 7 and subsequent steps are performed. Therefore, since the adsorption heater 10 is maintained in the energized state until the determination result of step S31 becomes positive, the temperature of the adsorbent increases toward the regeneration temperature Tk2.

If the determination result of step S31 is positive,
Go to the next steps S32 and S33, and set the flag F4 to 1
After is set, the timer in the controller 11 is activated to start time counting. Next step S
At 34, it is determined whether the elapsed time tc after the determination result of step S31 becomes positive reaches the predetermined time t3 (several seconds). If the determination result is no, the process proceeds to step S3 of FIG. Returning to this, the steps after this step are repeated. In this case, when the determination in step S29 is performed next, the determination result is positive, so in this case,
Bypassing steps S30 and S31, step S3
5 is carried out. In this step, the adsorption heater 10 so that the adsorbent temperature Tk is maintained at the regeneration temperature Tk2.
Feedback control of energization to.

After that, when the result of the determination in step S34 becomes positive, as in the case of the above-described embodiment, step S34 is performed.
The determination of 14 is performed, and when the determination result is positive, steps S17, S18, and S20 are sequentially performed, and the exhaust gas purification control routine ends. According to the control routine of the modified example described above, the adsorbent of the adsorbent unit 9 is maintained at the desorption temperature Tk1 for a certain period of time and then heated to the regeneration temperature Tk2 thereof and maintained for a predetermined period of time. The carbon adhering to the adsorbent can be completely burned and removed, and the adsorbent does not become inactive during the next use, and the adsorption efficiency can be maintained for a long time.

Next, referring to FIG. 8, there is shown the temperature rising characteristics of the auxiliary catalyst and the adsorbent in the case where the vehicle running experiment is actually carried out in the illustrated pattern. In this running experiment, unlike the above-described exhaust gas purification routine, the energization of the catalyst heater 8 is started at the time point S1, and the energization of the adsorption heater 10 is started at the time point S2. In FIG. 8, the temperature rising characteristics of the auxiliary catalyst temperature Ts and the catalyst temperature Ts are shown by two solid lines, respectively.
Indicates whether or not the next air is supplied. When the secondary air is supplied, the auxiliary catalyst temperature Ts rapidly rises as shown by the arrow A in the figure, while the rising rate of the adsorbent temperature Tk decreases as shown by the arrow B. I understand. The temperature rise characteristic of the adsorbent temperature Tk shown by the one-dot chain line indicates that the adsorbent is heated to the regeneration temperature. The temperature rise characteristics of the auxiliary catalyst temperature Ts and the catalyst temperature Ts indicated by the broken lines show an example when the heater is not used.

[0047]

As described above, according to the exhaust gas purifying apparatus of the present invention, since the adsorbent unit and the auxiliary catalyst unit are sequentially inserted in the downstream side portion of the exhaust gas pipeline, the underfloor catalyst unit The HC in the exhaust gas can be once adsorbed by the adsorbent of the adsorbent unit even immediately after the start of the engine which has not been activated yet. Then, after this, the heater is heated to wait for the auxiliary catalyst of the auxiliary catalyst unit to be activated, and then the heater is heated to desorb the HC adsorbed by the adsorbent. The HC desorbed from the catalyst has an excellent effect in purifying the HC, such that the HC is reliably oxidized and purified by the auxiliary catalyst and the HC is not released to the atmosphere.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an exhaust gas purifying apparatus according to an embodiment.

FIG. 2 is a graph showing the purification efficiency of HC with respect to the temperature of the auxiliary catalyst.

FIG. 3 is a graph showing the adsorption / desorption characteristics of HC with respect to the temperature of the adsorbent.

FIG. 4 is a flowchart showing a part of an exhaust gas purification control routine of one embodiment.

FIG. 5 is a flowchart showing the remaining part of the exhaust gas purification control routine of one embodiment.

FIG. 6 shows an exhaust gas purification control routine of a modified example.
3 is a flowchart showing a part corresponding to the flowchart of FIG.

FIG. 7 shows an exhaust gas purification control routine of a modified example.
It is the flowchart which showed the remaining part corresponding to the flowchart of FIG.

FIG. 8 is a graph showing changes in vehicle speed and temperature rising characteristics of an auxiliary catalyst and an adsorbent in a running test.

[Explanation of symbols]

1 engine 2 exhaust gas pipeline 3 Underfloor catalyst unit 6 Main muffler 7 Auxiliary catalyst unit 8 catalytic heater 9 Adsorbent unit 10 Adsorption heater 11 Controller 18 Air supply port

Claims (4)

[Claims] 1. An underfloor catalyst unit inserted in an exhaust gas pipeline extending from the engine to the rear of the vehicle under the floor of the vehicle body, and an underfloor catalyst unit located in the exhaust gas channel downstream of the underfloor catalyst unit, An auxiliary catalyst unit with a heater that can oxidize and purify at least unburned hydrocarbons, and is inserted in the exhaust gas pipe immediately upstream of the auxiliary catalyst unit,
An adsorbent unit with a heater that mainly adsorbs unburned hydrocarbons in the exhaust gas in an adsorption temperature range below a predetermined temperature, and desorbs mainly adsorbed unburned hydrocarbons in a desorption temperature range above a predetermined temperature. An exhaust gas purifying apparatus for automobiles, which is characterized by being provided. 2. A control means for controlling the energization of each heater of the auxiliary catalyst unit and the adsorbent unit is further provided, and the control means controls one of the two before the exhaust control system of the engine reaches a normal operating state. After energizing the heater to heat the catalyst of the auxiliary catalyst unit to the activation temperature, energize the other heater to raise the adsorbent temperature of the adsorbent unit to the desorption temperature region, and then control the exhaust of the engine. The exhaust gas purification system for an automobile according to claim 1, wherein when the system reaches a normal operation state, control of energization to each heater of the adsorbent unit and the auxiliary catalyst unit is stopped after a predetermined time has elapsed. apparatus. 3. The control means, after the adsorbent temperature of the adsorbent unit reaches the desorption temperature region, further energizes the heater of the adsorbent unit to raise the adsorbent to the regeneration temperature. The exhaust gas purifying apparatus for an automobile according to claim 2. 4. The exhaust gas pipeline is provided with an air supply port that is located between the adsorbent unit and the underfloor catalyst unit and is capable of supplying air into the exhaust gas pipeline. The exhaust gas purifying apparatus for an automobile according to claim 1.