JPH05332127A - Reproducing unit for exhaust gas filter - Google Patents

Abstract

PURPOSE:To lessen the change in temperature of a filter and reproduce a filter smoothly by effectively utilizing the heat a heater during the reproduction of the filter. CONSTITUTION:A heater 17 is arranged in front of a filter 13, and a radiation heat absorbing member 18 made of foam metal and so on is arranged further upstream from there. A by-pass passage 14 is provided so as to bypass exhaust gas during the reproduction, and also a filter side valve 15 and a by-pass side valve 16 are provided for a flow control. The first, the second, and the third temperature sensors 19, 20, and 21 each of which detects exhaust temperature T1, the temperature T2 of a radiation heat absorbing member 18, and the filter outlet side temperature T3 respectively, are provided, and the exhaust flow quantity during the reproduction is controlled by means of valves 15 and 16 so that the difference in the temperature between T3 and T2 is set to be wide (with the proviso T3>T2).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a regenerator for forcibly regenerating an exhaust filter for collecting exhaust particulates of an internal combustion engine by heating a heater.

[0002]

2. Description of the Related Art In order to collect exhaust particles such as carbon discharged from an internal combustion engine such as a diesel engine, an exhaust filter composed of a three-dimensional porous body of ceramics, so-called ceramic foam, or a plugged honeycomb filter made of ceramics is used. It has been conventionally considered to interpose it in the exhaust system, but with this exhaust filter, clogging over time becomes a problem, and some kind of regeneration means is indispensable. As one of the regeneration means, there is a regeneration device in which an electric heater is provided at an exhaust inlet of a filter made of ceramic foam or the like, and the heater is used to heat the filter to promote combustion of collected carbon and the like. Are known.

During regeneration using such a heater or the like, a bypass passage bypassing the filter is provided in order to avoid cooling of the filter due to exhaust gas flow, and the exhaust flow is guided to the bypass passage side. Some have been done.

Further, Japanese Utility Model Publication No. 64-15714 discloses that
A heat transfer conversion element made of ceramic fiber is provided on the upstream side of the heater provided on the front surface of the filter so as to absorb the heat trying to escape from the heater to the upstream side and heat the air flow supplied during regeneration. The configuration is shown.

[0005]

When forced regeneration is performed using the heater as described above, heat transfer to the outlet side of the filter will be smooth if no air flow or exhaust flow is supplied to the filter side. Therefore, uniform reproduction is difficult. Conversely, if the air flow or exhaust flow supplied during regeneration is too large,
Much of the heat of the heater is carried away by the air flow or exhaust flow, and the filter cannot be heated effectively.

Further, by detecting the exhaust temperature at the filter outlet,
As a representative of the filter temperature, it is conceivable that the air flow or exhaust flow supplied to the filter side is feedback-controlled, but even in this case, since the heat capacity of the filter is large, the control response delay is large and the efficiency is high. It is difficult to progress the playback well. In particular, the above-mentioned actual development
Even if heat is absorbed by the transfer conversion element as in Japanese Patent No. 15714, the temperature condition is not taken into consideration.
The absorbed heat cannot be used sufficiently effectively.

[0007]

As shown in FIG. 1, an exhaust gas filter regenerating apparatus according to the present invention includes a filter 1 for collecting exhaust particulates which is interposed in an exhaust passage of an internal combustion engine, and this filter 1. A bypass passage 2 formed so as to bypass the exhaust gas, an exhaust flow control mechanism 3 for controlling the exhaust flow rate bypassing to the bypass passage 2 side and the exhaust flow rate passing through the filter 1, and in the vicinity of the front surface of the filter 1. The heater 4 provided, the radiant heat absorbing member 5 provided further upstream of the heater 4 and capable of passing exhaust gas, and the first temperature detecting means 6 for detecting the temperature of the radiant heat absorbing member 5.
At the time of regeneration using the second temperature detecting means 7 for detecting the exhaust temperature on the outlet side of the filter 1 and the heater 4, the temperature on the outlet side of the filter 1 is higher than the temperature of the radiant heat absorbing member 5, and the temperatures of both of them are high. The temperature control means 8 for controlling the exhaust flow control mechanism 3 is provided in a direction in which the difference becomes large.

[0008]

[Operation] Normally, the entire amount of exhaust gas is guided to the filter 1 side,
Exhaust particles such as carbon in the exhaust are collected. When it becomes time to regenerate the exhaust particulates, the heater 4 is energized, and the filter 1 is forcibly regenerated. During this regeneration, most of the exhaust gas is guided to the bypass passage 2 side, and the cooling of the filter 1 by the excessive exhaust flow is prevented. However, a small amount of exhaust gas is introduced in order to diffuse the heat of the heater 4 throughout the filter 1. Further, the heat that tries to escape from the heater 4 to the upstream side is absorbed by the radiant heat absorbing member 5, and this heat heats a small amount of the exhaust flow toward the filter 1.

If the heat of the radiant heat absorbing member 5 is sufficiently utilized by the above exhaust flow, the temperature of the radiant heat absorbing member 5 is kept low. In other words, when the temperature of the radiant heat absorbing member 5 is high, the exhaust gas flow is too small and the heat of the heater 4 is not effectively used for regeneration. Further, the exhaust temperature on the outlet side of the filter 1 is representative of the temperature of the filter 1 itself. However, if the exhaust flow is too small, the heat transfer to the downstream will decrease, and the temperature will decrease. If there is too much, heat will be taken away by the exhaust gas and the temperature will drop.

Therefore, if the exhaust gas flow rate on the filter 1 side is adjusted so that the temperature of the radiant heat absorbing member 5 is as low as possible and the exhaust temperature on the outlet side of the filter 1 is as high as possible, regeneration can be performed most efficiently. From such a viewpoint, the temperature control means 8 controls the exhaust flow control mechanism 3 so that the filter outlet side temperature is higher than the temperature of the radiant heat absorbing member 5 and the temperature difference between the two becomes large, and the filter 1 is controlled. Optimally adjust the flow rate of exhaust gas passing through.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a structural explanatory view showing the mechanical structure of an embodiment of the present invention, in which an exhaust filter 13 for collecting exhaust particulates is interposed in the exhaust passage 12 of a diesel engine 11. ing. A bypass passage 14 is formed so as to bypass the filter 13.
Then, the exhaust passage 1 is provided on the upstream side of the filter 13 and, more specifically, on the downstream side of the branch portion of the bypass passage 14.
Butterfly valve type filter valve 1 that opens and closes 2
5, and a butterfly valve type bypass side valve 16 for opening and closing the bypass passage 14 is provided in the middle of the bypass passage 14. The filter side valve 15 and the bypass side valve 16 constitute an exhaust flow control mechanism.

The filter 13 has a so-called plugging structure in which a large number of fine flow paths are formed in a three-dimensional porous body of ceramics, so-called ceramic foam, or a ceramic block, and the flow path ends are alternately closed. The honeycomb filter is used as a filter element. An appropriate catalyst may be supported to accelerate the regeneration. This filter 1
The heater 17 is located close to the front surface of the heater 3, that is, the end surface on the exhaust inlet side.
Further, a radiant heat absorbing member 18 that absorbs and stores heat of the heater 17 is disposed slightly upstream of the heater 17 so as to cross the inside of the casing 13a. The radiant heat absorbing member 18 is formed in a coarse filter shape using, for example, foam metal having an excellent heat transfer coefficient.

The opening of each of the filter side valve 15 and the bypass side valve 16 is variably controlled by an actuator (not shown) such as a pulse motor. In this embodiment, both valves 15 and 16 are controlled. They are interlocked with each other, and when one opening degree increases, the other opening degree decreases. Both valves 1
Alternatively, the actuators 5 and 16 may be mechanically linked to each other, and the actuators may be simultaneously opened and closed by one actuator.

The openings of the filter side valve 15 and the bypass side valve 16 are controlled based on the detection signals of three temperature sensors such as thermocouples. First temperature sensor 19
Is located upstream of the branch portion of the bypass passage 14 of the exhaust passage 12, and is the exhaust temperature T discharged from the diesel engine 11.
1 is detected. The second temperature sensor 20 is attached to the radiant heat absorbing member 18, and the radiant heat absorbing member 18 is attached.
The temperature T2 of is detected. The third temperature sensor 21 is located at the outlet of the filter 13 of the exhaust passage 12,
Exhaust temperature T3 on the outlet side of the filter 13 representing the temperature of No. 3
Is being detected.

Reference numeral 22 denotes a control unit that controls the regeneration process using the heater 17. The control unit 22 uses a so-called microcomputer system, to which the detection signals of the temperature sensors 19 to 21 and the detection signals of various sensors (not shown) indicating the engine operating state are input, as will be described later. The heater 17, the filter side valve 15, and the bypass side valve 16 are controlled according to a predetermined program.

Next, the operation of the above embodiment will be described with reference to the flow charts of FIGS.

During normal operation of the diesel engine 11,
Filter side valve 15 is fully open and bypass side valve 1
6 is fully closed. Therefore, the entire amount of exhaust gas flows through the filter 13 and the fine particles such as carbon contained in the exhaust gas are collected. The flowchart of FIG. 3 is a main flowchart that is repeatedly executed during engine operation. In step 1, the engine speed Ne and the accelerator opening C / L are set.
In step 2, the particulate emission amount ΔPCT per unit time corresponding to the engine speed Ne and the accelerator opening C / L is searched based on the map shown in FIG. Then, in step 3, the particulate discharge amount ΔPCT per unit time is multiplied by the collection efficiency and sequentially integrated to obtain the total collection amount PCT, and in step 4, the total collection amount PCT is set to a predetermined value. Compare with PCT '. If the value is equal to or greater than the predetermined value PCT ', it is considered that the reproduction time has come, and the reproduction process of step 5 is executed.

The flowcharts of FIGS. 4 and 5 show the routine of this reproduction processing. In step 6, it is determined whether the exhaust temperature T1 is 500 ° C. or higher, and 50
When the temperature is 0 ° C. or higher, the process proceeds to step 7 and thereafter to perform self-regeneration by the exhaust heat, and when it is lower than 500 ° C., the process proceeds to step 13 and subsequent to perform forced regeneration using the heater 17.

When performing self-regeneration, the heater 17 is turned off.
The valve F is set to F (step 7), and the valve 15 on the filter side is fully opened and the valve 16 on the bypass side is fully closed (step 8). The filter valve 15 and the bypass valve 1
Since 6 and 6 move in conjunction with each other as described above, only the filter side valve 15 is described in the flowchart, and the bypass side valve 16 is omitted.

In this state, the entire amount of exhaust gas flows through the filter 13 side. Then, in step 9, the reproduction timer is sequentially incremented, and in step 10, it is judged whether or not the value of the timer reaches a predetermined value, and when the predetermined value is reached, the reproduction is ended. That is, the regeneration timer is cleared (step 11), and the value of the total collected amount PCT is cleared (step 12). It should be noted that if the exhaust temperature becomes lower than 500 ° C. during regeneration, the heater 17 moves to forced regeneration, but at this time, the value of the regeneration timer is held, so regeneration is performed without excess or deficiency.

In the case of forced regeneration, first turn on the heater 17.
(Step 13), and the valve 15 on the filter side is once fully closed (steps 14 and 15). In this state,
The entire amount of exhaust gas flows through the bypass passage 14 side. Further, in step 16, the exhaust gas temperature T1, the temperature T of the radiant heat absorbing member 18
2. Read the exhaust gas temperature T3 on the filter outlet side. And
In step 17, the filter-side valve 15 is opened step by step (for example, 2 °), and the temperature change accompanying this is changed to step 1
Judge at 8. Specifically, the detected temperatures of this time are set to T1, T
2, T3, when the valve opening was changed last time (Step 2
9) temperature If either is A or higher, the process proceeds to step 19 onward in FIG. If both are less than A, it is determined that no temperature change has occurred, and one routine is ended. still,
In this case, since the opening degree of the filter side valve 15 is increased step by step in step 17, the opening degree of the filter side valve 15 is increased until a change of a predetermined value A or more occurs.

In steps 19 to 28, the temperature change tendency is discriminated in eight ways, and the opening degrees of the filter side valve 15 and the bypass side valve 16 are controlled accordingly.

First, at step 19, it is judged whether or not the conditions of T2> T2 'and T3≥T3' are met, and here, YE
In the case of S, it is further determined in step 22 whether the condition of T1 <T1 'is satisfied. If T1 <T1 ', each valve 1
The opening degrees of 5 and 16 are maintained as they are (step 28), and T
If 1 ≧ T1 ′, the opening degree of the filter valve 15 is increased by one step (step 27).

If the condition in step 19 does not apply,
Proceed to step 20, and T2 <T2 'and T3 <T3'
It is determined whether the condition of is satisfied. If YES here, it is further determined in step 23 whether or not the condition of T1 <T1 'is satisfied. If T1 <T1 ', the opening degree of each valve 15, 16 is maintained as it is (step 28), and if T1≥T1', the opening degree of the filter side valve 15 is reduced by one step (step 26).

If the condition of step 20 is not satisfied, the process proceeds to step 21, where T2 ≧ T2 ′ and T3 ≧ T.
It is determined whether or not the condition of 3'is met. If YES here, it is further determined in step 24 whether the condition of T1 ≧ T1 ′ is satisfied. If T1 ≧ T1 ′, each valve 15, 16
The opening degree of is maintained as it is (step 28), and T1 <T1
If it is', the opening degree of the filter valve 15 is reduced by one step (step 26).

If the condition of step 21 is not satisfied, the process proceeds to step 25 and it is determined whether T1 ≧ T1 '. If T1 ≧ T1 ′, each valve 1
The opening degrees of 5 and 16 are maintained as they are (step 28), and T
If 1 <T1 ', the opening degree of the filter valve 15 is increased by one step (step 27).

That is, as a temperature change, the following 8 from a to h
Although the following cases are conceivable, the exhaust gas temperature T1 is between the exhaust gas flow rate passing through the filter 13 and the temperatures T2 and T3.
Assuming that is constant, there is a correlation as shown in FIG.
In consideration of this, the flow rate of exhaust gas passing through the filter 13 is adjusted.

A. When the temperature T2 of the radiant heat absorbing member 18 is lowered, the outlet side temperature T3 of the filter 13 is raised, and the exhaust side exhaust temperature T1 is lowered (steps 19 → 22 →
28).

It is conceivable that the temperature of the filter 13 rises after the exhaust flow rate increases, but the exhaust temperature T
There is a possibility that the temperature T2 has decreased due to the decrease of 1.
Since the preferred control direction is not clear, each valve 15,1
Hold 6 as is.

B. When the temperature T2 of the radiant heat absorbing member 18 decreases, the outlet temperature T3 of the filter 13 increases, and the exhaust temperature T1 of the inlet increases (steps 19 → 22 →
27).

This may be because the temperature of the filter 13 rises after the exhaust flow rate increases, and the exhaust temperature T
Since 1 also rises, the flow rate on the filter 13 side is increased in order to further raise the temperature of the filter 13.

C. When the temperature T2 of the radiant heat absorbing member 18 decreases, the outlet side temperature T3 of the filter 13 decreases, and the exhaust side exhaust temperature T1 decreases (steps 19 → 20 →
23 → 28).

It is considered that this is because the exhaust gas flow rate on the filter 13 side was too large, but as the exhaust gas temperature T1 decreased, T2 increased.
Since there is a possibility that T3 and T3 have decreased, each valve 1
Hold 5, 16 as they are.

D. When the temperature T2 of the radiant heat absorbing member 18 decreases, the outlet temperature T3 of the filter 13 decreases, and the exhaust temperature T1 of the inlet increases (steps 19 → 20 →
23 → 26).

It is considered that this is because the exhaust flow rate on the filter 13 side was too large, and therefore the flow rate on the filter 13 side is decreased.

E. When the temperature T2 of the radiant heat absorbing member 18 rises, the outlet side temperature T3 of the filter 13 rises, and the exhaust side exhaust temperature T1 rises (steps 19 → 20 →
21 → 24 → 28).

It is considered that this is because the flow rate of exhaust gas on the filter 13 side was too large, but as the exhaust gas temperature T1 rises, T2 increases.
Since there is a possibility that T3 and T3 have risen, each valve 1
Hold 5, 16 as they are.

F. When the temperature T2 of the radiant heat absorbing member 18 rises, the outlet side temperature T3 of the filter 13 rises, and the exhaust side exhaust temperature T1 falls (steps 19 → 20 →
21 → 24 → 26).

It is considered that this is because the exhaust flow rate on the filter 13 side was too large, and therefore the flow rate on the filter 13 side is decreased.

G. When the temperature T2 of the radiant heat absorbing member 18 rises, the outlet side temperature T3 of the filter 13 falls, and the exhaust side exhaust temperature T1 rises (steps 19 → 20 →
21 → 25 → 28).

It is considered that this is because the exhaust flow rate on the filter 13 side was excessively reduced, but T2 may have risen as the exhaust temperature T1 rises.
Hold 6 as is.

H. When the temperature T2 of the radiant heat absorbing member 18 rises, the outlet side temperature T3 of the filter 13 falls, and the exhaust temperature T1 of the inlet side falls (steps 19 → 20 →
21 → 25 → 26).

It is considered that this is because the exhaust flow rate on the filter 13 side is excessively reduced, so the flow rate on the filter 13 side is increased.

As a result of controlling the openings of the valves 15 and 16 in this way, the temperature difference between the outlet side temperature T3 of the filter 13 and the temperature T2 of the radiant heat absorbing member 18 (where T3> T2).
The exhaust gas flow rate on the filter 13 side is controlled so that the value of (1) is large, and the heat is regenerated in the form that the heat of the heater 17 is most effectively used.

On the other hand, when the valve opening is changed in steps 26 and 27, the values of T1, T2 and T3 at that time are respectively changed to T in step 29.
It is stored as 1 ', T2', T3 '. If the valve opening is not changed, the previous values of T1 ', T2', and T3 'are retained as they are without going through step 29.

Then, in step 30, it is judged whether the temperature T3 on the outlet side of the filter 13 is 500 ° C. or higher, and 500 ° C.
Only in the above cases, the reproduction timer is incremented (step 31). Similar to the case of self-regeneration described above, when the value of this reproduction timer reaches a predetermined value (step 32),
The values of the regeneration timer and the total collected amount PCT are cleared (steps 33 and 34). Also, turn off the heater 17,
Further, the filter side valve 15 is fully opened and the bypass side valve 16 is fully closed (steps 35 and 36).

Thus, in the above embodiment, the heater 17
Temperature T of the radiant heat absorbing member 18 that absorbs radiant heat to the front of the
Since the exhaust flow rate on the filter 13 side is appropriately controlled so that 2 is kept low and at the same time, the outlet side temperature T3 that is representative of the temperature of the filter 13 is increased, regeneration that effectively utilizes the heat of the heater 17 is performed. As a result, excessive power consumption, which is a problem when mounted on a vehicle, can be prevented, and reproduction can be reliably performed in a short time.

If the opening of each valve 15, 16 is feedback controlled only by the temperature T3 at the outlet side of the filter 13, a large heat capacity of the filter 13 causes a large delay in control, and the actual temperature of the filter 13 rises and falls considerably. However, in the above embodiment, each valve 1
Since the influence of the change in the opening degree of 5, 16 is immediately reflected in the temperature change of the radiant heat absorbing member 18, the control response is improved, and the temperature change of the filter 13 can be made small so that the regeneration can proceed more smoothly. It will be possible.

[0050]

As is apparent from the above description, according to the exhaust filter regenerating apparatus of the present invention, the heat of the heater is effectively used for regenerating the exhaust filter by flowing an appropriate amount of exhaust gas during regeneration. As a result, it is possible to surely perform the reproduction in a short time and suppress unnecessary power consumption. Also, the response of the exhaust flow rate control becomes good,
It is possible to reduce the actual fluctuation of the filter temperature to allow the regeneration to proceed more smoothly.

[Brief description of drawings]

FIG. 1 is a claim correspondence diagram showing a configuration of the present invention.

FIG. 2 is a structural explanatory view showing a mechanical structure of an embodiment of the present invention.

FIG. 3 is a main flowchart of reproduction control in this embodiment.

FIG. 4 is a flowchart showing a main part of reproduction control.

FIG. 5 is a flowchart following FIG. 4;

FIG. 6 is a map showing a particulate emission amount per unit time corresponding to an engine speed and an accelerator opening.

FIG. 7 is a characteristic diagram showing a relationship between an exhaust flow rate and each temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Filter 2 ... Bypass passage 3 ... Exhaust flow control mechanism 4 ... Heater 5 ... Radiant heat absorption member 6 ... First temperature detection means 7 ... Second temperature detection means 8 ... Temperature control means

Claims (1)

[Claims] 1. A filter for collecting exhaust particulate matter, which is interposed in an exhaust passage of an internal combustion engine, a bypass passage formed so as to bypass the filter, an exhaust flow amount bypassed to the bypass passage side, and the filter. An exhaust flow control mechanism for controlling the flow rate of exhaust gas passing through the heater, a heater provided in the vicinity of the front surface of the filter, and a radiant heat absorbing member provided further upstream of the heater and capable of passing exhaust gas;
The first temperature detecting means for detecting the temperature of the radiant heat absorbing member, the second temperature detecting means for detecting the exhaust gas temperature on the filter outlet side, and the temperature at the filter outlet side are radiant heat during regeneration using the heater. An exhaust filter regenerating apparatus comprising: temperature control means for controlling the exhaust flow control mechanism in a direction in which the temperature is higher than the temperature of the absorbing member and the temperature difference between the two becomes large.