JPS6030408Y2 - Diesel engine exhaust purification device - Google Patents

Description

[Detailed description of the invention] This invention is designed to easily and reliably detect clogging of a filter member installed in the exhaust passage for collecting particulate components such as carbon particles in the exhaust of a diesel engine. This invention relates to an exhaust purification device for a diesel engine.

Conventionally, an exhaust purification device for a diesel engine detects exhaust pressure upstream of a filter member in an exhaust passage using an exhaust pressure detection means, and detects clogging of the filter member based on an increase in the exhaust pressure. It is known that a burner provided upstream of a filter member is operated to eliminate clogging (JP-A-54-120).
29).

However, in the exhaust purification device that uses exhaust pressure to detect clogging as described above, the exhaust pressure changes not only due to clogging of the filter member but also due to operating conditions such as engine speed and load. However, for example, exhaust pressure is high during high-load operation and low when rear idling.
It is necessary to detect clogging of the filter member by comparing the exhaust pressure map set in advance according to the operating state with the exhaust pressure detected by the detection means, which makes the circuit configuration complicated. There are drawbacks.

In addition, as an exhaust purification device for a diesel engine, carbon particles in the exhaust gas are deposited in a collection container using a cyclone, and two electrodes are placed at a certain level within the container. There is also known a device in which the amount of carbon deposition is detected by connecting the electrodes with carbon when the carbon deposition level exceeds a certain level (Japanese Utility Model Publication No. 49-72813).

However, the cyclone method described above has a complicated structure, cannot sufficiently collect extremely small particulate components, and requires periodic removal of accumulated carbon in the container.

The purpose of this invention is to eliminate the above-mentioned drawbacks of conventional devices that collect particulate components in exhaust gas using a filter member installed in the exhaust passage. To provide a new exhaust purification device for a diesel engine that can directly and reliably detect clogging.

Therefore, in the diesel engine exhaust purification device of this invention, two electrodes are disposed on the filter member in the exhaust passage of the engine, and a predetermined voltage is applied between the electrodes so that the filter member is placed on the filter member in the exhaust passage of the engine. It is characterized by comprising a detection circuit that detects a change in resistance between the electrodes that changes depending on the amount of carbon particles attached to the filter, and clogging of the filter member is directly detected by the output signal of the detection circuit. There is.

Hereinafter, this invention will be explained in detail with reference to illustrated embodiments.

In Fig. 1, 1 is an exhaust passage in an exhaust pipe 2 of a diesel engine, 3 is a honeycomb-shaped non-conductive filter member disposed in the exhaust passage 1, and every other pore is arranged at one end of the exhaust passage. The two holes are closed with blind plugs 3a, and the exhaust gas flowing in from one of the pores flows out to the other through the porous partition wall 3b.

4 and 5 are fixed to the peripheral wall of the exhaust pipe 2 via insulating members 6 and 7, respectively, and are inserted into the filter member 3.
A pair of electrodes having a constant interval from each other are closely inserted into the partition wall 3b in a direction perpendicular to the axis of the filter member 3, and 8 is a burner provided in the exhaust pipe 2 upstream of the filter member 3; The burner 8 blows out combustion gas and filters the filter member 3.
It is designed to burn off carbon particles etc. that adhere to the top.

When carbon particles 15 adhere to the partition wall 3b of the filter member 3 as shown in FIG. It has a decreasing characteristic as shown in the figure.

A resistor 13 is connected between the one electrode 5 and the anode of the battery B whose negative electrode is connected to the ground 11.
A ground 11 is connected to the other electrode 4.

Therefore, the value of the current flowing from battery B to resistor 13 and electrodes 5, 4 is equal to
It is determined by the electrical resistance between the electrodes 5 and 4, which decreases as the amount of .

Therefore, the difference in voltage across the resistor 13 increases as shown by curve A in FIG. 4 as the amount of attached carbon particles 15 increases.

On the other hand, the voltage across the resistor 13 is input to the voltage detection device 17, and the difference between the voltages across the resistor 13 is detected.

The voltage detection device 17 outputs a signal representing the voltage difference to the comparator 18.

Further, the reference value setting device 19 is set with a reference value representing the reference amount of carbon adhesion at which the burner 8 should be operated, and the reference value signal is outputted to the comparator 18 .

The comparator 18 compares the signal representing the voltage difference with the reference value signal, and if the signal representing the voltage difference is larger than the reference value signal, that is, the amount of carbon adhesion is greater than the reference amount. For example, a bi-level signal is output to the determination circuit 21 shown in FIG.

The judgment circuit 21 is composed of an AND gate and is for operating the burner 8 only under certain conditions.

The determination circuit 21 inputs output signals from an accelerator switch 23 and a vehicle speed sensor 24 to determine whether or not it is idling, and an exhaust temperature sensor provided downstream of the filter member 3. The output signal from the exhaust gas temperature sensor 25 is inputted to determine whether the temperature detected by the exhaust temperature sensor 25 is, for example, 700°C or less, and connected to the battery B via the ignition switch 26, so that the , only when the output signal from the comparator 18 is bi-level and the temperature detected by the exhaust temperature sensor 25 is 700° C. or lower, the judgment circuit 21 issues an operation command to the burner control device 22 to operate the burner 8. A bi-level signal is output as a signal.

In this way, the burner 8 is operated only during idling, when the exhaust volume is low and in a stable state, making it easy to control the fuel and air of the burner 8.

Also, the temperature detected by the exhaust temperature sensor 25 is 700°C.
The burner 8 is activated only in the following cases, that is, the burner 8 is deactivated when the detected temperature is 700° C. or higher to protect the filter member 3 from overheating.

Further, when the ignition switch 26 is turned off, the stoppage of the engine is detected by turning off the ignition switch 26, and the burner control device 22 from the judgment circuit 21
Stop outputting the signal for operating battery B.
protect

When the operation command signal is input from the judgment circuit 21, the burner control device 22 first outputs a signal to heat the ignition heater 31 of the burner 8, and then, when the temperature of the ignition heater 31 reaches 900° C. or higher, When this is detected by the output signal from the heater temperature sensor 32, a signal is output to drive the fuel pump 33 and the air pump 34, so that good combustion gas is ejected from the burner 8 into the exhaust passage 1. .

In this way, when the ignition heater 31 reaches a certain temperature or higher,
For the first time, fuel and air are supplied to the burner 8 to ensure complete combustion and to prevent secondary pollution due to unburned gas released from the burner 8.

Moreover, when stopping the operation of the burner 8, conversely, after stopping the driving of the combustion pump 33 and the air pump 34,
Heating to the ignition heater is stopped to allow complete combustion and to prevent secondary contamination as in the case of operation.

The diesel engine exhaust gas purification device configured as described above detects the amount of carbon deposited on the filter member 3 and operates the burner 8 as described below.

It is now assumed that this diesel engine is idling, the temperature detected by the exhaust temperature sensor 25 is 700° C. or lower, and carbon particles 15 of a standard amount or more have adhered to the filter member 3.

Then, the electrical resistance between the electrodes 4 and 5 becomes smaller depending on the amount of carbon particles 15 attached.

Therefore, the value of the current flowing through the resistor 13 and the electrodes 5 and 4 becomes large, and the difference in voltage across the resistor 13 detected by the voltage detection device 17 is the standard that represents the standard adhesion amount shown by the curved line in FIG. greater than the voltage.

Therefore, the comparator 18 detects the high level signal from the judgment circuit 21.
Output to.

The judgment circuit 21 determines whether the engine is in an idling operating state based on two signals for idling detection applied from the accelerator switch 23 and the vehicle speed sensor 24, a signal input from the exhaust temperature sensor, and a high level signal input from the comparator 18. A state in which the exhaust temperature downstream of the filter member 3 is 700° C. or lower, and the amount of carbon particles attached to the filter member 3 is equal to or higher than the reference amount, and the burner 8 should be operated. , and outputs an operation command signal to the burner control device 8.

Based on the operation command signal, the burner control device 22 first
A signal for heating the ignition heater 31 is output, and when it is detected by a signal input from the ignition heater temperature sensor 32 that the ignition heater 31 has been heated to 900° C. or higher, the fuel pump 33 and the air pump are activated. 34 is output, fuel and air are supplied to the burner 8, and combustion gas is ejected from the burner 8.

Since the burner 8 is provided upstream of the filter member 3, the combustion gas is blown onto the filter member 3 together with the exhaust gas, burns carbon particles adhering to the filter member 3, and filters the To recover from clogging of one member 3.

On the other hand, when the amount of carbon particles attached to the filter member 3 is less than the reference amount and the comparator 18 outputs a low level signal, or when the idling is detected by the signals from the accelerator switch 23 and the vehicle speed sensor 24. If not, or the exhaust temperature detected by the output signal from the exhaust temperature sensor 25 is 700'C! In the above case, the judgment circuit 21 does not output the operation command signal and the burner 8
to prevent energy loss and overheating of the filter member 3.

In the above embodiment, the burner 8 is operated during idling operation, but the burner 8 may be operated during high load operation.

Further, in the above embodiment, the detection circuit for detecting clogging of the filter member 3 is constituted by the resistor 13, the battery B1 voltage detecting device 17, the comparator 18, and the reference value setting device 19. Although the clogging is detected based on the voltage difference, the circuit for detecting the clogging used in this invention is not limited to this, and for example, the value of the current flowing through the electrodes may be directly detected.

Further, the electrodes disposed on the filter member 3 are not limited to those of the above embodiments; for example, as shown in FIG. On the other hand, a conductive substance 43 such as stainless steel, gold, or platinum may be fixed to the other blind plug 42 by vapor deposition, baking, etc. so as to be in contact with the carbon particles 15, and the conductive substance 43 may be used as an electrode. .

As is clear from the above description, according to this invention, two electrodes are disposed on the filter member in the exhaust passage of the engine, and a predetermined voltage is applied between the electrodes so that the filter member is placed on the filter member. A detection circuit that detects the change in resistance between the electrodes that changes depending on the amount of attached carbon particles is installed to detect clogging of the filter member.
With a simple and inexpensive configuration, clogging of a filter member can be directly and reliably detected without being affected by engine operating conditions.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the main parts of a diesel engine exhaust purification device according to an embodiment of this invention, and Fig. 2 is a -
■ Line cross-sectional view, Figure 3 is a graph showing the relationship between the amount of carbon and the resistance between the electrodes, Figure 4 is a graph showing the relationship between the amount of carbon and the voltage difference between both ends of the resistance, and Figure 5 is the graph showing the relationship between the amount of carbon and the voltage difference between the two ends of the resistance. FIG. 6 is a schematic diagram showing the overall configuration of the exhaust purification device for a diesel engine shown in the figure, and FIG. 6 is a sectional view showing a modification of the electrode. 1...Exhaust passage, 3...Filter member, 4゜5...Electrode.

Claims (1)

[Claims for Utility Model Registration] In a diesel engine in which a filter member for collecting carbon particles, etc. in the exhaust gas is disposed in the exhaust passage of the engine, two electrodes are arranged at a certain distance from each other on the filter member. and a detection circuit that detects a change in resistance between the electrodes that changes depending on the amount of carbon particles adhering to the filter member, and the detection circuit detects clogging of the filter member. An exhaust purification device for a diesel engine characterized by the following configuration.