JPS628325Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an exhaust purification device for a diesel engine in which a filter member for collecting particulate components such as carbon particles in the exhaust of a diesel engine is provided in the exhaust passage. The present invention relates to an exhaust purification device that eliminates clogging of a filter member by burning the components using a heating device.

The exhaust gas of a diesel engine contains many particulate components such as carbon particles, and it has been considered essential to remove these particulate components when purifying the exhaust of a diesel engine.
Conventionally, exhaust purification devices for this purpose include, for example, as shown in Japanese Patent Application Laid-Open No. 49-71315.
A filter member for collecting the particulate components is disposed in the exhaust passage, and the collected components are appropriately burned by a burner device disposed upstream of the filter member to eliminate clogging of the filter member. It is known what has been done.

In the above-mentioned exhaust gas purification device, the burner device is operated periodically or as appropriate when clogging of the filter member is detected by the clogging detection means. Generally, when the above-mentioned captured component is heated to about 580 to 600°C, it burns out in a short period of about several tens of seconds, and the filter member is unclogged.

If the above-mentioned burner device is operated when the exhaust gas temperature is high, the amount of fuel required to heat the collected components to about 580 to 600°C and completely burn them is small. In conventional exhaust purification devices, in order to facilitate burner control, the burner control device is often configured to operate the burner device during idling when the exhaust flow rate is stable. It often happens that the burner device is activated when the exhaust gas temperature is not high enough, such as during an intermittent start-up. If the burner device is operated when the exhaust gas temperature is low as described above, a problem naturally arises that a large amount of burner fuel is used or that the collected components are not burnt out sufficiently.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an exhaust gas purification device for a diesel engine equipped with a heating device, in which the heating device for eliminating clogging does not operate even when the exhaust gas temperature is low. This is the purpose.

The exhaust purification device for a diesel engine of the present invention includes the above-mentioned exhaust purification device, that is, a filter member that collects particulate components such as carbon particles in the exhaust gas, which is disposed in the exhaust passage, and a filter member that collects particulate components such as carbon particles in the exhaust gas, and a A device for determining a clogging state of a filter member in an exhaust purification device for a diesel engine, wherein a heating device for eliminating clogging of a filter member is provided, and the heating device is activated when the filter member is clogged; An exhaust temperature sensor installed in the exhaust passage detects the warm-up state of the engine, and the output from this exhaust temperature sensor detects the above-mentioned clogging when the exhaust temperature exceeds the set value, regardless of the engine cooling water temperature. The heating device is characterized by being provided with a heating device operation limiting device that outputs a heating device activation signal in a predetermined operating range according to the output from the device, and prevents the heating device from operating when the exhaust gas temperature is below a set value. It is something.

By providing the heating device operation restriction device as described above, when the engine is cold, the heating device will not be activated even if a heating device activation signal is issued, so heating energy is wasted or the components collected by the filter are not activated. Problems such as insufficient combustion of fuel will be solved.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an exhaust purification device for a diesel engine according to an embodiment of the present invention. A honeycomb-shaped non-conductive filter member 3 is disposed in the exhaust passage 2 of the engine 1. The filter member 3 has a large number of pores 3b formed by porous partition walls 3a. The pores 3b have alternate ends and one end of each is closed with a blind plug 3c, and the exhaust gas flowing into the pores 3b whose upstream end is open passes through the porous partition wall 3a. The water passes through and flows out into the pore 3b, which has an open downstream end. When the exhaust gas passes through the partition wall 3a, fine particles such as carbon particles contained in the exhaust gas are collected by the partition wall 3a. A pair of electrodes 4 and 5 are inserted into the filter member 3 in a direction perpendicular to its axis. These electrodes 4 and 5 are fixed to the peripheral wall of the filter member 3 via insulating members 6 and 7, respectively, and are inserted into each partition wall 3a tightly, that is, without forming a gap between them and the partition wall 3a. ing. A burner 8 serving as a heating device is disposed in the exhaust passage 2 on the upstream side of the filter member 3. This burner 8 includes a primary air nozzle 8a, a secondary air nozzle 8b, a fuel nozzle 8c, and an ignition heater 8.
Consists of d. Both the primary air nozzle 8a and the secondary air nozzle 8b are connected to an air pipe 10 drawn from a discharge port of an air pump 9 that supplies combustion air. On the other hand, the fuel nozzle 8c is connected to a fuel tank 13 that stores burner fuel F by a fuel pipe 12 in which a fuel pump 11 is installed. An orifice 14 is provided in the air pipe 10, and a substantially conical needle 15b fixed to a diaphragm 15a of a diaphragm device 15 is inserted into the orifice 14. The diaphragm chamber 15a of the diaphragm device 15 is connected via a control air pipe 16 to a negative pressure source 17 such as a vacuum pump. An air valve 18 is disposed in the control air pipe 16, and a fuel valve 19 is also disposed in a portion of the fuel pipe 12 between the fuel pump 11 and the burner 8.

The aforementioned electrodes 4 and 5 are connected to a clogging detection circuit 20, and the output of this clogging detection circuit 20 is input to a control circuit 21. Furthermore, the diesel engine 1 is provided with a rotation speed detection means 22 such as a pulse generation type rotation speed sensor, and a load detection means 23 that detects the engine load by detecting, for example, a plunger stroke of a fuel injection pump. The output of the above control circuit 2
1 is input. An exhaust gas temperature sensor 24 is provided in the exhaust passage 2 on the downstream side of the filter member 3 in close proximity to the filter member 3, and the output of this exhaust gas temperature sensor 24 is also input to the control circuit 21.

The operation of the exhaust gas purification device of this embodiment having the above structure will be explained below.

The electrical resistance between the pair of electrodes 4 and 5 described above has a characteristic that when fine particles such as carbon particles adhere to the partition wall 3a of the filter member 3, the electric resistance decreases as the amount of the adhered fine particles increases. Therefore, for example, if one electrode 4, 5 is connected to the anode of a battery via a resistor, while the cathode of the battery is connected to ground, and the other electrode 5, 4 is connected to ground, the The voltage difference increases as the amount of particles attached to the partition wall 3a increases. Therefore, here, a reference voltage generation circuit is provided which generates the same reference voltage as the voltage difference when the fine particles are attached to the extent necessary to combust the burner 8 and eliminate the clogging of the filter member 3, If this reference voltage and the voltage difference are compared and an electric signal is generated when the voltage difference exceeds the reference voltage, the burner operation can be automatically started using this electric signal. The clogging detection circuit 20 is configured to obtain a voltage that fluctuates in accordance with the amount of attached particles as described above, and input this voltage signal to the control circuit 21 as the clogging detection signal _S1 . be. As shown in detail in FIG. 2, the control circuit 21 includes a reference voltage generator 25 that generates the reference voltage V _R as described above.
, this reference voltage V _R and the above clogging detection signal S ₁
Clogging determination section 2 consisting of a comparison circuit that compares the
6. In this clogging determination section 26, it is determined whether or not the amount of adhered fine particles has reached a predetermined amount.Since the electrical resistance of fine particles such as carbon particles changes depending on the temperature, the clogging detection signal _S1 is determined based on the temperature. In the correction section 27, the temperature is corrected by the temperature signal _S2 obtained from the exhaust temperature sensor 24, and the correction signal is sent to the clogging determination section 26.
S ₁ ′ is input.

In the clogging determination section 26, a correction signal S ₁ ' that also takes into account the temperature condition is compared with a reference voltage _VR .
When the correction signal S ₁ ' exceeds the reference voltage _VR , a clogging removal signal S ₃ is sent to the burner control section 28. The burner control unit 28 does not immediately output the burner operation signal S ₄ even when this clogging removal signal S ₃ is input, and the reference temperature signal S ₅ issued from the reference temperature signal generation unit 29 and the exhaust temperature sensor 24 A warm-up signal indicating that the exhaust gas temperature has reached a predetermined temperature is generated from the warm-up state determination unit 30 which is compared with the output temperature signal _S2 .
S ₆ is input, and the burner operation signal S ₄ is generated only when the idling state is detected from the rotation speed signal S ₇ from the rotation speed detection means 22 and the load signal S ₈ from the load detection means 23. Burner activation signal
As shown in FIG. 1, _S4 is an ignition signal _S4 ' that ignites the ignition heater 8d of the burner 8 and a
Fuel supply signal S ₄ ″ to open 9, and air valve 1
It consists of a combustion air supply signal S ₄ that opens 8. When the fuel valve 19 is opened, the fuel nozzle 8c of the burner 8
When the fuel F is supplied to the air valve 18 and the air valve 18 is opened, the diaphragm chamber 15c of the diaphragm device 15 communicates with the negative pressure source 17, and as a result, the diaphragm 15a moves against the return spring 15d to the right in FIG. I am drawn towards someone. As the diaphragm 15a moves in this manner, the needle 15b exits the orifice 14 and opens the air pipe 10.
Combustion air is supplied to the primary and secondary air nozzles 8a and 8b of the burner 8. By operating the burner 8 as described above, the fine particles adhering to the filter member 3 are burned, and the filter member 3
clogging is cleared. Note that FIG. 3 is a flowchart showing the flow of signals when the above-mentioned control is performed by a computer.

Here, the fuel supply signal S ₄ ″ and the combustion air supply signal S ₄ are output after a predetermined time has elapsed after the ignition signal S ₄ ′ has been issued, or after the ignition signal S ₄ ′ has been issued and the ignition heater 8d is activated. The light is emitted after it is detected that the burner has been heated to a predetermined temperature, for example, about 900° C. By doing so, it is possible to prevent secondary pollution due to the release of unburned gas from the burner 8.

As described above, the burner 8 can be easily controlled by using the rotation signal S ₇ and the load signal S ₈ to operate the burner 8 only in the idling state where the exhaust flow rate is stable. In addition, the warm-up state determination unit 3
0 prevents the burner 8 from operating when the exhaust gas temperature has not reached a predetermined value, thereby preventing the burner 8 from operating during idling in a cold state, such as during a cold start, and reducing the burner 8's requirements. It becomes possible to set the amount of heat generation small.

Note that clogging of the filter member 3 can be detected by a method other than the method of detecting from a change in interelectrode resistance in the above embodiment, for example, by a method of detecting from a change in pressure difference between the upstream side and the downstream side of the filter member. It may be done. In addition to the burner 8 described above, an electric heater or the like may be used as a heating device for burning the particulates adhering to the filter member 3. Furthermore, it is of course possible to use the clogging detection signal _S1 as a current signal, and in that case, the clogging determining section 26 is naturally configured to compare the signal with a reference current.

As explained in detail above, in the diesel engine exhaust purification device of the present invention, the heating device for eliminating clogging of the filter member does not operate when the exhaust gas temperature is low. By using this device, problems such as high energy consumption for heating and insufficient combustion of filter-collected components can be solved.

[Brief explanation of drawings]

Figure 1 is a system diagram showing one embodiment of the present invention;
1 is a block diagram showing the configuration of a control circuit in the embodiment of FIG. 1, and FIG. 3 is a flowchart showing the flow of control in the embodiment of FIG. 1... Engine, 2... Exhaust passage, 3... Filter member, 4, 5... Electrode, 8... Burner, 2
0...Clogging detection circuit, 21...Control circuit, 2
4...Exhaust temperature sensor, 29...Reference temperature signal generation section, 30...Warm-up state determination section, S1...Clogging detection signal, _{S2 ...} Temperature signal, _S3 ...Clogging removal signal, S ₄ ... Burner operation signal, S ₆ ... Warm-up signal.

Claims (1)

[Scope of Claim for Utility Model Registration] 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 eliminating clogging of the filter member is disposed in the exhaust passage upstream of the filter member. A diesel engine exhaust purification system that operates the heating device when the filter member is clogged includes a device that determines the clogging state of the filter member, and a device installed in the exhaust passage that detects the warm-up state of the engine. According to the output from this exhaust temperature sensor, when the exhaust temperature exceeds the set value, heating is performed in a predetermined operating range according to the output from the clogging determination device, regardless of the engine cooling water temperature. An exhaust gas purification device for a diesel engine, comprising a heating device operation limiting device that outputs a device activation signal and prevents the heating device from operating when the exhaust gas temperature is below the set value.