JP2847976B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purification device provided in an internal combustion engine, and more particularly to an exhaust gas purification device provided with a particulate filter for collecting diesel particulates discharged from a diesel engine.

[0002]

2. Description of the Related Art For example, since the exhaust gas of a diesel engine contains exhaust particulates, that is, particulates, a particulate filter (hereinafter also referred to as a filter) for trapping the particulates is provided in an exhaust system of the engine. )
Is installed.

[0003] The particulate filter is generally formed of, for example, a ceramic material having good air permeability, and has a structure in which the particulates are collected in the filter partition wall when the exhaust gas passes through the filter.
Therefore, the filter must be regenerated periodically, as the amount of particulates collected increases as the filter is used, resulting in a gradual loss of air permeability and an increase in back pressure.

When the filter is regenerated, for example, an electric heater is arranged at the end of the filter, and an electric pump for supplying a regeneration gas (secondary air) to the filter is provided outside the filter. When the power is supplied, the particulates are ignited, and the flame is propagated to the downstream side of the filter by the regeneration gas (secondary air) supplied from the electric pump, thereby burning the particulates over the entire area of the filter. An exhaust emission control device is already known (see Japanese Utility Model Laid-Open No. 63-138417).

[0005]

The electric power supplied to the electric heater and the electric pump described above is usually supplied by a battery mounted on the vehicle, and the battery voltage generally depends on the operating conditions of the vehicle (for example, Engine speed). In the conventional apparatus as described above, since the battery voltage is directly applied to the electric heater and the electric pump, the supply power fluctuates, and the heat generation amount of the heater and the discharge amount of the regeneration gas are reduced. It fluctuates every time the filter is regenerated. For example, when the supply power is excessive, the heater wire may be blown or the flame may blow out. In addition, when the supplied power is too small, there is a possibility that particulate ignition becomes difficult or the flame does not sufficiently propagate, resulting in filter regeneration failure, and the filter regeneration conditions are not constant.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an exhaust gas purifying apparatus capable of always obtaining a constant filter regeneration state.

[0007]

According to the present invention, there is provided, in accordance with the present invention, a filter provided in an exhaust system of an internal combustion engine for collecting particulates, and an electric heater disposed at an end of the filter. An exhaust gas purifying apparatus that incinerates particulates trapped in a filter by energizing the filter to regenerate the filter includes a battery voltage detecting unit that detects a voltage of a battery that supplies power to the electric heater when the filter is regenerated. Duty ratio calculating means for calculating a duty ratio of electric power supplied to the electric heater based on the battery voltage and a predetermined heater voltage, and duty control of a battery energizing time supplied to the electric heater based on the obtained duty ratio. And a constant power supply means for supplying a constant power to the electric heater.

Further, in the present invention, an exhaust gas purifying apparatus provided with an electric pump for supplying a regeneration gas to a filter at the time of filter regeneration is provided with a battery voltage detection for detecting a voltage of a battery for supplying electric power to the electric pump at the time of filter regeneration. Means,
A duty ratio calculating means for calculating a duty ratio of electric power supplied to the electric pump based on the detected battery voltage and a predetermined electric pump voltage; and a battery energizing time supplied to the electric pump based on the obtained duty ratio. An exhaust gas purifying apparatus having constant power supply means for supplying constant electric power to the electric pump by duty control of the electric pump is provided.

[0009]

When the filter is regenerated, the energization time between the battery and the electric heater or the electric pump is duty-controlled by the duty ratio obtained from the battery voltage, so that the supplied electric power is constant regardless of the battery voltage fluctuation. The amount of heat generated by the heater and the discharge amount of the regeneration gas can be kept constant, and fluctuations in the filter regeneration state can be reduced.

[0010]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows, as a first embodiment of the present invention, an exhaust gas purifying apparatus that steadily supplies power to an electric heater provided in a filter. In the figure, reference numerals 1a and 1b denote two filters which are arranged in parallel and each of which is formed so as to collect particulates, and 2 filters exhaust gas from an engine body (not shown) through a filter 1 during particulate collection. The exhaust pipe finally leads to the muffler 3.

As shown in the figure, the exhaust pipe 2 has a filter 1a,
In accordance with 1b, the filter is branched upstream of the filter and merges again. Further, a bypass pipe 4 for guiding exhaust gas from the engine body directly to the muffler 3 without passing through the filters 1a and 1b at the time of filter regeneration is connected to a portion of the exhaust pipe 2 on the exhaust upstream side of the filters 1a and 1b. On the way, a first control valve 5 for achieving the above-mentioned exhaust gas flow is provided.

Further, on the filter side relative to the connection (upstream side of the filter) between the exhaust pipe 2 and the bypass pipe 4, during regeneration of the filter, the regeneration gas after passing through the filter (secondary air in this example). Is connected to a gas discharge pipe 6 for discharging the gas to the outside, and a second control valve 7 is also provided at this connection portion.

Electric heaters 8a and 8b for igniting the particulates collected at the time of filter regeneration are provided at the downstream ends of the filters 1a and 1b. Further, an electric pump 9 for supplying a regeneration gas for particulate combustion, that is, secondary air to each of the filters 1a and 1b at the time of filter regeneration, is provided downstream of the exhaust gas merging portion. Therefore, in the present embodiment, the regeneration gas flows back through the filters 1a and 1b during filter regeneration, unlike during particulate collection.
A third control valve 10 for preventing the flow of the regeneration gas is provided downstream of the discharge port of the regeneration gas to the exhaust pipe 2.

According to the present embodiment, the two filters 1a and 1b shown in the drawings are regenerated by first energizing one electric heater and then regenerating the other filter by energizing the remaining electric heaters. Thus, the reproduction processing is performed in order. Accordingly, a fourth control valve 11 and a fifth control valve 12 for controlling the introduction of the regeneration gas filter upstream of (or downstream of) the regeneration gas from the electric heaters 8a, 8b of the filters 1a, 1b. Is provided.

The above-described control valves 5, 7, 10, 11 and 12 are driven by pressure-responsive actuators, and the pressure (negative pressure) applied to each actuator is controlled.
The introduction is controlled by negative pressure switching valves (VSV) 14, 15, 16 and 17 which are turned on and off by a control circuit (ECU) 13.
In each of the control valves shown in FIG. 1, the position of each solid line indicates the valve position during particulate collection, and the position of the dotted line indicates the valve position during regeneration of the filter 1a (filter 1b).
During the regeneration, the positions of the fourth and fifth control valves are reversed.)

According to this embodiment, each electric heater 8a, 8b
Is connected to the battery 20 via the relay 18 and the semiconductor relay 19, and the relay 18 is driven by the control circuit 13 at the time of filter regeneration to determine power supply to one of the electric heaters 8a or 8b. I do. Similarly, the semiconductor relay 19 is driven by the control circuit 13 to perform a duty control of the energizing time of the battery 20 to the electric heater 8a or 8b based on a duty ratio D described later.
a and 8b are supplied with a predetermined steady-state power.

In addition, the control circuit 13 is connected to various sensors (for example, an engine speed sensor or the like) 21 for detecting the operation state of the vehicle and an exhaust pressure sensor (not shown) for detecting the filter regeneration time. When the predetermined filter regeneration condition is satisfied, the control circuit 13 controls the VSVs 14, 16 (or 15) so that the valve positions of the control valves 5, 7, 10, 11 and 12 occupy the positions indicated by the dotted lines in FIG. ) And 17, and at the same time, outputs a drive signal to the electric pump 9, the relay 18, and the semiconductor relay 19.

The control circuit 13 has a CPU, a memory (RAM, RO
M), a microcomputer comprising an input / output port and a bus, and is operated by the battery 20.
Further, a supply voltage detecting unit for detecting the battery voltage Vb is provided therein, and controls the operation of an exhaust gas purifying device described later.

FIG. 2 is a flowchart for explaining an operation example of the control circuit 13 relating to filter regeneration. This flowchart describes the regeneration of the filter 1a. Although not shown, after the regeneration of the filter 1a is completed, the filter 1b is also subjected to a regeneration process by a similar program. This flowchart is a time interruption routine executed at predetermined time intervals.

Referring to FIG. 2, in step 31, it is determined whether or not the filter regeneration processing flag Fa is currently reset to 0. If regeneration is not being performed (Yes), the routine proceeds to step 32 as it is. The flag Fa is initialized to 0 at the time of starting the engine.

In step 32, the signals of the various sensors 21 and the exhaust pressure sensor for detecting the operation state are read, and it is determined whether or not it is the current filter regeneration time. And filter regeneration time
If determined to be (Yes), the routine proceeds to step 33, where the filter regeneration processing flag Fa is set to 1 and the electric pump 9, the electric heater 8a, the VSVs 14, 15, 16 and
And a timer counter Ca for operation for a predetermined time to 17
Start. Note that the flag Fa in this step 33
In the processing routine after the setting, No is determined in step 31 until the regeneration processing of the filter 1a is completed. In this case, the process skips steps 32 and 33 described above and proceeds to step 34. On the other hand, if No in step 32, that is, if it is determined that the current time is not the filter regeneration time, the following steps are skipped, and this routine is terminated.

In step 34, in order to operate the control valves (the first control valve 5, the second control valve 7, the third control valve 10, and the fifth control valve 12) related to the regeneration of the filter 1a, a corresponding VS is operated.
Outputs signals to activate V14, 16 and 17 and relay 1
8 and the electric power from the battery 20 is supplied to the electric heater 8a.
And outputs a signal for starting the operation of the electric pump 9 for supplying the regeneration gas.

Next, at step 35, the battery voltage Vb is detected by the supply voltage detector in the control circuit 13 as described above. In the subsequent step 36, as shown in FIG. 3, the ratio of the predetermined heater voltage Vh to the current battery voltage Vb, that is, the electric heater energization, is determined based on the detected battery voltage Vb and the predetermined heater voltage Vh (constant value). A duty ratio D for duty control of time is determined (D = 100 × Vh / Vb).

Next, at step 37, a drive signal is output so that the semiconductor relay 19 is turned on and off with the duty ratio D determined as described above. As a result, even if the battery voltage Vb actually fluctuates, the duty ratio D changes every moment according to the fluctuation, and the energization time ratio per cycle changes for the electric heater 8a (see FIG. As shown in FIG. 3, when the battery voltage is high, the duty ratio D becomes small and the energization time during one cycle becomes short.) Therefore, constant electric power is always supplied to the electric heater 8a. In the following step 38, the value of the timer counter Ca is incremented, and the process proceeds to step 39.

In step 39, looking at the counter Ca updated as described above, it is determined whether a predetermined filter regeneration processing time has elapsed, that is, whether a predetermined count T corresponding to this processing time has exceeded a predetermined count T. Is determined. If the determination in step 39 is affirmative, the routine proceeds to step 40, in which signal output to the VSVs 14, 16, and 17, the electric pump 9 and the semiconductor relay 19 is stopped, and the electric heater 8
is stopped, and at the same time, the filter regeneration processing flag F
a and the counter Ca are reset to 0, and this routine ends. On the other hand, in the case of No in step 39, the filter regeneration processing is continued as it is,
Is skipped and this routine ends.

An example of the operation of the control circuit 13 relating to the regeneration processing of the filter 1a has been described above with reference to the flowchart of FIG. 2. Naturally, however, the same program is applied to the electric heater 8b of the filter 1b in accordance with the variation of the battery voltage. Irrespective of this, constant power is supplied. In the above-described flowchart, for the sake of explanation, the filter regeneration time is set to a predetermined fixed time in accordance with the power supply time to the electric heater, but the electric heater power supply stop time is set to the filter regeneration end time (that is, the filter regeneration end time). Alternatively, the end of regeneration may be determined by other detection means (for example, a temperature sensor for detecting the end of particulate flame propagation) before the operation stop timing of the control valve or the electric pump.

As described above, according to the first embodiment of the present invention, a constant power is supplied to the electric heaters 8a and 8b during the regeneration of the filter. The amount of heat generated can be kept constant, and fluctuations in the regeneration state of the filters 1a and 1b can be reduced as compared with those of the conventional exhaust gas purification device. still,
The illustrated first embodiment is an example of an exhaust purification device in which an electric heater is disposed downstream of the exhaust of a filter and secondary air for regeneration flows backward from an exhaust downstream of an electric pump. However, the present invention is not limited to this embodiment, and a forward-flow regeneration type exhaust gas purification apparatus that regenerates a filter with a part of exhaust gas or sends a regeneration gas from an exhaust gas upstream side of the filter also includes an electric heater. All are applicable. Also, the number of filters is not limited to the first embodiment.

FIG. 4 shows a second embodiment of the present invention. Regarding the illustrated components, the same components as those in the first embodiment (FIG. 1) are denoted by the same reference numerals, and the description of the operation thereof will be omitted.

While the previous embodiment is provided for the purpose of keeping the power supplied to the electric heater constant, the present embodiment is provided for keeping the power supplied to the electric pump 9 constant. That is, according to the present embodiment, the semiconductor relay 19 is provided in the energizing circuit to the electric pump 9, and the control circuit 13
The duty ratio D ′ (D ′ = 100 ×) is obtained based on the detected battery voltage Vb and a predetermined constant pump voltage Vp.
Vp / Vb), and the semiconductor relay 19 is turned on and off so that the power supplied to the electric pump 9 is constant (see FIG. 5).

As a result, a constant amount of regeneration gas is supplied to the electric pump 9 at the time of filter regeneration regardless of fluctuations in the battery voltage Vb.
The problem of cooling of the heater and flame blow-out phenomenon (in case of excessive discharge amount) or flame propagation failure (in case of insufficient discharge amount) due to variation in supply of regeneration gas is solved. Will be.

In connection with this embodiment, the electric pump 9
The operation flowchart of the control circuit 13 during the filter regeneration including the duty control of the power supplied to the filter is substantially the same as that of the flowchart of FIG. Vp).

The embodiments of the present invention have been described with respect to the case where duty control is performed on the energizing time to the electric heater and the case where duty control is performed on the energizing time to the electric pump in order to obtain a stable filter regeneration state. Of course, in one exhaust gas purification apparatus, duty control may be performed by calculating the duty ratios D and D 'for energizing both the electric heater and the electric pump. In this case, the filter regeneration state of the exhaust gas purification device described above can be further stabilized, and the durability and reliability of the filter itself can be further improved.

[0033]

As described above, according to the present invention, the electric power supplied from the battery to the electric heater and / or the electric pump is made constant by the duty control, so that the electric power of the heater is independent of the actual fluctuation of the battery voltage. The amount of heat generated and the amount of discharged gas for regeneration can be kept constant, fluctuations in the filter regeneration state can be reduced, and filter regeneration efficiency can be maximized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an exhaust gas purification device according to a first embodiment of the present invention.

FIG. 2 is a flowchart illustrating the operation of a control circuit that executes regeneration on a filter 1a shown in FIG. 1;

FIG. 3 is a diagram showing an example of a change with time of a battery voltage Vb and a heater voltage Vh with respect to the embodiment of FIG. 1, and showing a relationship between a duty ratio D calculated in the flowchart of FIG. 2;

FIG. 4 is a schematic configuration diagram of an exhaust gas purification device as a second embodiment of the present invention.

FIG. 5 is a diagram showing an example of a change with time of a battery voltage Vb and a pump voltage Vp with respect to a second embodiment, and showing a relationship between the duty ratio D ′.

[Explanation of symbols]

 1a, 1b: Particulate filter 8a, 8b: Electric heater 9: Electric pump 13: Control circuit 19: Semiconductor relay 20: Battery

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F01N 3/02 341 F01N 9/00

Claims (2)

(57) [Claims] 1. A filter provided in an exhaust system of an internal combustion engine for collecting particulates, an electric heater disposed at an end of the filter, and energization of the heater, the particulates collected by the filter are provided. In an exhaust gas purifying apparatus for an internal combustion engine that regenerates a filter by burning incinerators, a battery voltage detecting unit that detects a voltage of a battery that supplies power to the electric heater during filter regeneration, and the detected battery voltage and a predetermined value A duty ratio calculating means for calculating a duty ratio of electric power supplied to the electric heater according to a predetermined heater voltage, and a constant electric power supplied to the electric heater by performing duty control of a battery energizing time supplied to the electric heater based on the obtained duty ratio. An exhaust gas purifying apparatus having a constant power supply means. 2. An exhaust gas purification system for an internal combustion engine, comprising: a filter provided in an exhaust system of the internal combustion engine for trapping particulates; and an electric pump for supplying a regeneration gas to the filter when the filter for burning the particulates is regenerated. In the apparatus, at the time of filter regeneration, a battery voltage detecting means for detecting a voltage of a battery for supplying electric power to the electric pump, and the electric power is supplied to the electric pump by the detected battery voltage and a predetermined electric pump voltage. An exhaust gas purifying apparatus comprising: a duty ratio calculating unit that calculates a duty ratio of electric power; and a constant power supply unit that supplies a constant power to the electric pump by duty-controlling a battery energizing time supplied to the electric pump based on the obtained duty ratio.