JPH0726940A - Exhaust emission control device - Google Patents

Abstract

PURPOSE:To prevent the regeneration rate of a filter from varying due to variation in applied voltage, by controlling the duty rate of current for energizing electrically heating means for regenerating the filter in accordance with a detected voltage and a detected current so as to set the power for carrying current to the electrically heating means to a predetermined desired power value. CONSTITUTION:Particulate in exhaust gas discharged from a Diesel-engine 20 are trapped by a filter 2. Pressures of the exhaust gas upstream and downstream from the filter 2 are detected by pressure sensors 7, 17, and the volume of trapped particulate is calculated from the result of the detection and outputs from an engine speed sensor 8 and an exhaust gas temperature sensor 6. If the calculated value exceeds a threshold value, the filter is regenerated. That is, a blower 13 is driven so as to feed air into the filter 2 while a heater 11 is energized so s to burn the particulate. Further, at this time, the duty rate of current for energizing the heater 11 is controlled in accordance with outputs from voltage detecting means 58 and current detecting means 59 so as to set the power energizing the heater 11 to a predetermined desired power value, thereby it is possible to restrain the heating value from varying.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for collecting and regenerating particulate matter (particulates) contained in the exhaust gas of a diesel engine.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 4-66717 energizes a heater (electric heating means) disposed in the vicinity of a filter in order to burn the particulates collected in the filter to regenerate the filter. Then, the filter and the particulates are heated to burn the particulates.

It is necessary to supply a considerable amount of electric power to the above-mentioned heater, and the air supply means for supplying the combustion air must be driven accordingly, and a considerable amount of electric power for regeneration is supplied to the commercial ground. It must be supplied from a power source or a vehicle battery.

[0004]

However, when reproducing power is supplied from the above-mentioned commercial ground power source or battery,
It was found that the fluctuation of those voltages had a great influence on the regeneration result of the filter. That is, in the combustion of the particulates distributed in the filter, the ignition surface is first ignited at a predetermined portion (in the vicinity of the heater), and then the temperature of the filter is further increased by the ignition, and the combustion surface is spread from the ignition portion (spreading). Will do). Then, the ignition timing, the spread rate of fire after ignition, and the shape of the combustion surface have a great influence on the final regeneration rate (= the amount of particulate combustion / the amount of particulate collection).

Of course, it is possible to use a constant voltage power supply device, but the scale of power consumption is as large as 1 kW or more, the scale of the device becomes large, and it is disadvantageous in terms of weight, vehicle-mounted space, and economy. Further, there is a problem that the power consumption increases by the power loss of the constant voltage power supply device. Further, as a second problem, the resistance value of the heater used as the electric heating means changes with time due to a surface oxidation reaction at the time of heating, which causes a change in the supplied power and a change in the calorific value. Similarly, the reproduction rate fluctuates.

It is also conceivable that conductive particles such as particulates may enter between the windings of the heater to lower the insulation resistance between the adjacent windings of the heater. It fluctuates. To solve this problem, the winding cross-sectional area of the heater should be formed to have a large diameter, and sufficient electrical insulation between adjacent windings should be achieved, but this increases weight and impairs economic efficiency. In addition, the air resistance of the heater portion increases, which hinders the oxygen supply to the filter.

The present invention has been made in view of the above problems, and it is possible to prevent a change in the amount of heat generated due to a change in the resistance value of the electric heating means without increasing the cross-sectional area of the winding, and to change the amount of heat generated by a change in the applied voltage. It is a problem to be solved to provide an exhaust gas purifying device capable of preventing changes.

[0008]

An exhaust gas purifying apparatus according to the present invention burns a filter arranged in an exhaust passage of a diesel engine and a particulate matter collected by the filter by heating the filter. An electric heating means for regenerating the filter, an air supplying means for supplying air to the filter when the filter is regenerated, a voltage detecting means for detecting a voltage applied to the electric heating means, and a current supplied to the electric heating means. And a control means for controlling the duty ratio of the energizing current to the electric heating means based on the detected voltage and the detected current so that the electric power supplied to the electric heating means becomes a predetermined target electric power value. It is characterized by having.

In a preferred mode, the control means controls the duty ratio based on a signal corresponding to the voltage when the electric heating means is energized.

[0010]

In the exhaust gas purifying apparatus of the present invention, the voltage applied to the electric heating means and the electric current to be applied are detected, and the electric power actually applied to the electric heating means is detected based on the detected voltage and the detected current. The value is actually detected. Usually,
Since it is not necessary to consider the power factor, the energized power value is the detected voltage ×
It becomes the detection current. Then, the target energizing power value and the detected energizing power value are compared, and the duty ratio of the energizing current is controlled according to the ratio so that the energizing power to the electric heating means becomes a predetermined target power value. Control.

In this way, the exhaust gas purification can prevent the change in the amount of heat generated due to the change in the resistance value of the electric heating means without increasing the cross-sectional area of the winding, and can also prevent the change in the amount of heat generated due to the change in the applied voltage. The device can be realized, and the fluctuation of the reproduction rate due to these causes can be prevented. Further, since the constant voltage power supply device is not required, it is possible to realize an exhaust gas purifying device that saves power consumption by preventing an increase in device weight and required space.

[0012]

FIG. 1 shows an embodiment of an exhaust gas purifying apparatus according to the present invention.
Shown in. This exhaust gas purifying apparatus has a filter housing case 1 whose both ends are hermetically sealed, and an upstream side pressure sensor 7, a temperature sensor 6, a heater (main body) for detecting exhaust pressure are arranged in the filter housing case 1 from the upstream side to the downstream side. Electric heating means in the invention) 1
1, the filter 2, and the downstream pressure sensor 17 for detecting the downstream pressure of the filter are sequentially arranged. The exhaust pipe 3 of the diesel engine 20 is arranged on the upstream end wall of the filter housing case 1.
Is branched. The air supply pipe 10 is connected to an outlet of a blower 13 for supplying air through a solenoid valve 14.

On the other hand, the motor M of the heater 11 and the blower 13 described above is drive-controlled by a controller (control means) 8, and the output signal of the rotation speed sensor 18 mounted on the diesel engine 20 is output to the controller 8. . The controller 8 has a microcomputer (not shown) with a built-in A / D converter, processes various data,
The switches 55 and 56 are controlled to be opened and closed to control the heater 11 and the blower 13, and when an abnormality occurs, the abnormality warning lamp 9
Lights up (an abnormal signal is output).

Reference numeral 5 denotes a power feeding device, which includes a plug 51 connected to a commercial ground power source (not shown), a step-down transformer 52,
The full-wave rectifier 53 is provided, and the DC voltage output from the full-wave rectifier 53 is applied to the high end of each of the heater 11 and the blower drive motor M, and the low end of the heater 11 is grounded through the switch 56 so that the blower drive motor M has a low voltage. The lower end is grounded through the switch 55.

The filter 2 is a honeycomb ceramic filter (manufactured by Nippon Insulator kk, diameter 5.66 inches × length 6 inches), which is fired into a cylindrical shape using cordierite as a raw material. The filter 2 has a large number of vent holes penetrating both end faces thereof, one of the adjacent vent holes is plugged at the upstream end, and the other is plugged at the downstream end. The exhaust gas passes through the porous partition wall between the adjacent vent holes, and only the particulates are trapped in the vent holes. Both end faces of the filter 2 face the both end faces of the case 1 with a predetermined distance.

The heater 11 is composed of an electrothermal resistor made of a nichrome wire and is arranged close to the end face of the filter 2 which is located on the upstream side during regeneration. The operation of this device will be described below. (Particulate collection operation) Diesel engine 20
The exhaust gas discharged from the exhaust gas is introduced into the case 1 through the exhaust pipe 3, particulates in the exhaust gas are collected by the filter 2, and the purified exhaust gas is discharged from the tail pipe 4 to the outside.

(Filter Regeneration Operation) Next, the regeneration operation of the filter 2 will be described with reference to the flowcharts of FIGS. It should be noted that in this device, the filter regeneration operation is started by receiving power from an external power source while the engine is stopped and starting it by a manual operation. Solenoid valve 14 just before starting playback
Is opened.

First, FIG. 2 shows a filter regeneration routine consisting of a filter regeneration determination routine (steps 100 to 111) executed during engine operation and a filter regeneration execution routine (steps 112 to 116) executed during engine stop. . First, the filter regeneration determination routine is started when the engine 20 is started, and step 1
00, the exhaust pressure P detected by the pressure sensors 7 and 17
1, P2, the engine speed n detected by the speed sensor 18, and the exhaust gas temperature T detected by the temperature sensor 6, the particulate trapping amount is calculated based on a memory map.

Next, in step 108, it is checked whether or not the searched particulate collection amount G exceeds a predetermined threshold value Gt. If it does not exceed, the process returns to step 100, and if it does, to step 111. move on. In step 111, the lamp 91 for instructing filter regeneration is turned on, and the routine ends.

After that, when the driver visually confirms that the lamp 91 for instructing filter regeneration is turned on and turns on a regeneration switch (not shown) while the engine is stopped, the filter regeneration execution routine is started. In this routine, first, the blower 13 is activated in step 112, then the built-in timer is activated (114), the timer control subroutine is executed to perform the reproduction operation (116), and the reproduction is ended.

In this timer control subroutine, energization power control and air blow control are performed based on a timer, and necessary power is supplied to the heater 11 in accordance with each regeneration stage, and is collected by the filter 2 by this. The particulates burn and the filter 2 is regenerated. The reproduction power supply system of this embodiment will be described in more detail below with reference to FIG.

When the outlet 51 is connected to a commercial ground power source (AC200V) (not shown), the commercial AC voltage is stepped down by the step-down transformer 52 and rectified by the full-wave rectifier 53 to obtain a DC 24V DC full-wave rectifier. It is applied to the high level power supply line 54 from the high level output terminal of 53. The controller 8 is powered by an onboard battery (not shown).

The power supply system during this regeneration will be described below. Along with the regeneration command, the switches 55 and 56 are controlled to open / close at a predetermined timing and duty ratio to supply a predetermined power to the blower motor M and the heater 11 at a predetermined timing. To do. On the other hand, a voltage dividing circuit 58 formed by connecting resistors R1 and R2 in series is connected between the high-potential power line 54 and the ground line, and the divided voltage is input to the controller 8 as a voltage signal of the high-potential power line 54, and the controller 8 A / within 8
It is converted into a digital value by a D converter (not shown). Further, a current sensor 59 is arranged in the middle of the power supply line connecting the heater 11 and the switch 56, and the current sensor 59
Detects the energization current of the heater 11. The current sensor 59 may be of a magnetic field detection type or a method of detecting a low resistance voltage drop.

The duty ratio control subroutine which characterizes the present embodiment will be described below with reference to the flowchart of FIG. This subroutine is an interrupt routine and is executed every predetermined time (here, for example, 500 msec). First, the controller 8 to the switch 56
An ON signal is output to check whether the heater 11 is energized (200). If not energized, the process returns to the main routine. If energized, the voltage V of the high-level power supply line 54 is output from the voltage dividing circuit 58. Read (201), current sensor 59
The current I supplied to the heater 11 is read from (202).

Next, the duty ratio correction coefficient Dk = Po /
(V × I) is calculated (203). Note that Po is a reference power value to be supplied at a duty ratio of 100%, and V × I is a heating power value. Next, the current duty ratio (that is, heater energization power) Dm stored in advance in the memory is searched and read (204).

Next, the memory duty ratio Dm is multiplied by the duty ratio correction coefficient Dk to obtain the output duty ratio D (2
05), the switch 56 is switched by the fixed-cycle pulse signal having the obtained output duty ratio D (206). As a result, it is possible to prevent fluctuations in the power supply voltage, fluctuations in the voltage of the high-level power supply line 54 due to fluctuations in the energization current, and fluctuations in the amount of heat generated by the heater 11 due to fluctuations in the resistance value of the heater 11. Playback is realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an exhaust gas purification device of the present invention,

FIG. 2 is a flowchart showing the reproducing operation,

FIG. 3 is a flowchart showing the reproducing operation,

[Explanation of symbols]

2 is a filter, 6 is a temperature sensor, 7 and 17 are pressure sensors, 8 is a controller (control means), 11 is a heater (electric heating means), 18 is a rotation speed sensor, 58 is a voltage dividing circuit (voltage detecting means), 59. Is a current sensor (current detection means).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Yoshida 1-1, Showa-cho, Kariya city, Aichi Prefecture Nihon Denso Co., Ltd. (72) Inventor Keiichi Kato 1-1-1-1, Showa town, Kariya city, Aichi prefecture Incorporated (72) Inventor Naoji Morita 1-1, Showa-cho, Kariya, Aichi Nihon Denso Co., Ltd. (72) Inventor Takayuki Toya 1-1-chome, Showa-cho, Kariya, Aichi Nihon Denso Co., Ltd.

Claims (2)

[Claims] 1. A filter arranged in an exhaust path of a diesel engine, an electric heating means for regenerating the filter by burning particulates collected by the filter by heating the filter, and the filter. A supply means for supplying air to the filter at the time of regeneration, a voltage detection means for detecting a voltage applied to the electric heating means, a current detection means for detecting a current flowing to the electric heating means, and a heating means for the electric heating means. An exhaust gas purifying apparatus comprising: a control unit that controls a duty ratio of a current supplied to the electric heating unit based on the detected voltage and a detected current so that the supplied power reaches a predetermined target power value. 2. The exhaust gas purifying apparatus according to claim 1, wherein the control means performs the duty ratio control based on a signal corresponding to the voltage when the electric heating means is energized.