JPS6117209Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an improvement of an exhaust purification device for a diesel engine.

(Prior art) Conventionally, in order to prevent particulate components such as carbon particles in the exhaust of a diesel engine from being released into the atmosphere, a filter member for collecting the particulate components has been disposed in the exhaust passage, and a filter member has been installed in the exhaust passage upstream of the filter member. A diesel engine exhaust purification device is known in which a heating device such as a burner device is provided in a passage to burn and remove the particulate components collected on the filter member to recover from clogging of the filter member. (For example, see JP-A-54-12029.) In the above exhaust gas purification device, it is preferable to operate the heating device in response to the state of carbon accumulation on the filter member from the viewpoint of durability and fuel efficiency of the filter member. It is something. Therefore, the applicant proposed a technique for detecting the state of carbon particle deposition in a filter member by installing a pair of electrodes at a predetermined interval on the filter member, and detecting the state of deposition from the change in electrical resistance between the electrodes due to carbon deposition. The company has previously filed an application for a diesel engine exhaust purification device. (Refer to Japanese Utility Model Application No. 56-83631 (Japanese Utility Model Publication No. 60-30408)) However, in the detection method of the above-mentioned device, the detection electrode is attached to a filter member that collects the entire amount of particulate components such as carbon particles in the exhaust gas. Due to the direct arrangement, it is difficult to install the electrode, to assemble the filter member and the electrode, and to repair and replace the electrode.

(Purpose of the invention) The present invention has been made in view of the above points, and by disposing a pair of electrodes on a particulate component collection member separate from the filter member and detecting the state of carbon accumulation, It is an object of the present invention to provide an exhaust gas purification device for a diesel engine that improves assembly workability and allows easy maintenance and inspection of electrodes.

(Structure of the invention) The present invention is arranged in the exhaust passage upstream of a filter member disposed in the exhaust passage to collect particulate components such as carbon particles in the exhaust gas, and downstream of the heating device for recovering from clogging of the filter member. a particulate component collecting member, a pair of electrodes disposed at a predetermined interval on the particulate component collecting member, and detecting the state of carbon particle deposition from a change in electrical resistance between the electrodes due to carbon deposition. and a heating device control device that controls the operation of the heating device.

Therefore, when particulate components such as carbon particles are collected by the particulate component collecting member, the electrical resistance between the electrodes changes due to carbon deposition on the member, which causes the heating device control device to The state of accumulation of carbon particles is detected and the operation of the heating device is controlled to burn off the carbon particles and the like collected on the filter member and to recover from clogging.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. 1 to 4, 1 is a diesel engine, 2 is an intake passage of the diesel engine 1, and 3 is an exhaust passage of the same. A filter member 4 for collecting particulate components such as carbon particles in the exhaust gas is disposed in the exhaust passage 3, and a filter member 4 for collecting particulate components such as carbon particles in the exhaust gas is disposed in the exhaust passage 3 upstream of the filter member 4. A burner device 5 is connected as a heating device.

Further, 6 is a particulate component collecting member disposed in the exhaust passage 3 upstream of the filter member 4 and downstream of the burner device 5, and the particulate collecting member 6 has a pair of electrodes 7, 7 ( (See Figures 2 and 4)
are arranged at a predetermined interval, and the detection signal of the electrodes 7, 7 detects the state of carbon particle deposition from the change in electrical resistance between the electrodes 7, 7, and controls the operation of the burner device 5. It is output to the burner control device 8.

The filter member 4 is formed of a porous material into a honeycomb shape, and every other pore along the flow of exhaust gas is closed at its end with a blind plug 4a, and the open pore at one end (other The exhaust gas that flows in from one end (one end is closed) passes through the air-permeable porous partition wall 4b and flows out from the open pores at the other end (one end is closed), passing through the partition wall 4b. It is sometimes configured to collect particulate components such as carbon particles in exhaust gas.

The burner device 5 includes a burner 9 including a fuel nozzle 9a and an ignition heater 9b, and a fuel tank 10.
A fuel supply passage 13 for supplying fuel from the fuel pump 11 via an on-off valve 12 and an air supply passage 16 for supplying air from an air pump 14 via an on-off valve 15 are connected to the ignition heater 9b. A power source 18 (battery) is connected through an ignition heater switch 17, and when the burner device 5 is activated, it supplies combustion gas to the exhaust passage 3 to raise the temperature of the exhaust gas.

Further, in the particulate component collecting member 6, a small-diameter introduction pipe 19 with an enlarged inlet end at the center of the exhaust passage 3 is supported by a stay 20 on the passage wall 3a.
A detection filter 21 is provided at the rear of the introduction pipe 19.
The detection filter 21 is formed of a non-conductive porous material into a honeycomb shape, and like the filter member 4, the pores at the inflow end and the discharge end are alternately closed with blind plugs 21a. , is configured to collect particulate components such as carbon particles in the exhaust gas when it passes through the partition wall 21b.

A pair of electrodes 7, 7 installed on the particulate component collecting member 6 are attached to pass through the partition wall 21b of the detection filter 21 at a predetermined interval along the flow of exhaust gas, and are attached to the partition wall 21b. The carbon particles are in close contact with each other so that the carbon particles collected on the detection filter 21 come into contact with the detection filter 21, while being supported in a non-contact (insulated) state with respect to the introduction pipe 19. A lead wire 22 is connected to the electrodes 7, 7, and the lead wire 22 is guided out of the exhaust passage 3 through the inside of the stay 20 without contacting the exhaust gas,
It is connected to the burner control device 8.

The electrical resistance between the pair of electrodes 7, 7 has a characteristic that when carbon particles adhere to the partition wall 21b of the detection filter 21, it decreases in accordance with the increase in the amount of deposited carbon particles. A voltage is applied between 7 and 7, and a change in resistance value can be detected from this voltage change.

FIG. 5 shows a modification of the installation position of the particulate collection member 6', in which it is directly fixed to the passage wall 3a of the exhaust passage 3, and the shape of the tip of the introduction pipe 19' is different. is constructed in the same way as in FIG.

On the other hand, the burner control device 8 includes electrodes 7, 7.
In addition to the signals from the burner control device 8, the detection signal of the rotation sensor 23 that detects the engine speed and the output of the temperature sensor 24 that detects the exhaust temperature are input, and the output signal (control signal) of the burner control device 8 is input to the output signal of the burner device 5. an on-off valve 12 for the fuel supply passage 13;
This is output to the on-off valve 15 of the air supply passage 16 and the ignition heater switch 17, respectively, and the burner control device 8 is configured to operate the burner device 5 when the amount of carbon deposit exceeds a set value. ing.

FIG. 6 shows an example of the burner control device 8, in which 25 is a resistance value detection circuit for detecting a change in resistance value between the electrodes 7, 7, and its output signal is inputted to a temperature correction circuit 26. This temperature correction circuit 26 corrects changes in the electric resistance value of carbon due to temperature, and receives the exhaust temperature signal from the temperature sensor 24 and converts the signal from the resistance value detection circuit 25 into only changes in the carbon deposition state. Correct it so that it becomes a corresponding detection signal. The output signal of the temperature correction circuit 26 is compared with the reference signal from the reference level setting circuit 28 in the clogging determination circuit 27 to determine whether or not the clogging is occurring. When the clogging occurs, that is, when the amount of carbon deposit is large, a control signal is generated. circuit 2
9 outputs a control signal to the burner device 5.

The reference level setting circuit 28 calculates a predetermined reference signal from a memory 32 in response to a signal from an engine operating state determination circuit 31 to which the engine rotation speed signal from the rotation sensor 23 and the time signal from the timer 30 are input. , clogging determination circuit 27
This is what is output to. This reference level setting circuit 28 basically sets a reference signal corresponding to the electrical resistance value when a predetermined carbon deposition state is reached, but the size of the filter member 4 and particulate collection member 6 is A reference signal is set that is corrected for the difference in carbon particle collection rate based on the difference in size (difference in volume).

In other words, when the engine speed is low, the collection rate tends to be higher when the engine speed is low, but when the engine speed is high, the collection rate tends to be lower when the engine speed is high. When the determined operating state has a high ratio of low-speed operation, the reference signal is corrected to a high value (large amount of carbon deposited), while when the ratio of high-speed operation is high, the reference signal is corrected to a low value (small amount of carbon deposited). The engine operating state determination circuit 31 has a function of calculating the average rotational speed.

When a control signal is output from the control signal generation circuit 29, the ignition heater switch 17 is first closed to heat the ignition heater 9b, and then both on-off valves 7, 7 are opened to supply fuel and air. burner 9
The combustion gas is supplied to the exhaust passage 3 to raise the exhaust temperature, and the carbon particles and the like collected in the filter member 4 and the particulate collecting member 6 are burned off and the clogging is recovered.

In the above embodiment, in order to improve the detection accuracy by correcting the correspondence between the carbon deposition state of the filter member 4 and the detected carbon deposition state of the particulate collection member 6, the engine rotation speed is adjusted based on the filter volume difference. Although a corresponding correction is made, corrections corresponding to the load etc. may also be made based on various experiments. However, there is no problem in practice if rotational correction is performed for the volume difference.

Further, the filter member 4 and the detection filter 21 of the particulate component collecting member 6 do not need to be formed of the same material, and for example, the coarseness of the mesh may be changed in order to change the collection rate. Furthermore, the burner device 5 may also be of a mixture supply type or the like as appropriate.

(Effect of the invention) Therefore, according to the present invention as described above, a particulate component collection member for detecting the state of carbon deposition is provided separately from a filter member, and a pair of electrodes are disposed on this particulate component collection member. This has the advantage that assembly workability is improved and maintenance and inspection of the electrodes can be easily performed.

[Brief explanation of the drawing]

The drawings illustrate an embodiment of the present invention, and FIG. 1 is an overall configuration diagram, FIG. 2 is a longitudinal cross-sectional view of a main part of an exhaust passage, FIG. 3 is a front view of a particulate component collection member, and FIG. 4 is a diagram of the same. FIG. 5 is an enlarged sectional view, FIG. 5 is a longitudinal sectional view of a main part showing a modification, and FIG. 6 is a block diagram of the burner control device. 1... Diesel engine, 3... Exhaust passage,
4... Filter member, 5... Burner device, 6,
6'... Particulate component collection member, 7... Electrode, 8...
...Burner control device, 21...Detection filter.

Claims (1)

[Scope of utility model registration request] Exhaust purification of a diesel engine, in which a filter member for collecting particulate components such as carbon particles in the exhaust gas is disposed in the exhaust passage, and a heating device for recovering from clogging of the filter member is provided in the exhaust passage upstream of the filter member. In the apparatus, a particulate component collecting member disposed in an exhaust passage upstream of the filter member and downstream of the heating device, a pair of electrodes disposed at a predetermined interval on the particulate collecting member, and a carbon 1. An exhaust gas purification device for a diesel engine, comprising: a heating device control device that detects the deposition state of carbon particles from a change in electrical resistance between the electrodes due to deposition and controls the operation of the heating device.