JPH08121150A - Control device for diesel particulate filter - Google Patents

Abstract

PURPOSE: To detect whether or not a particulate filter for the exhaust gas of a diesel engine is clogged with the specified amount of particulates collected, enable particulates to be burnt up as required, concurrently detect whether or not the filter itself is damaged, and thereby prevent particulates and the like from being exhausted without being filtered. CONSTITUTION: It is judged that a filter is clogged with particulates collected when the magnitude of a sound signal from a sound sensor 200 provided at the downstream side in the filter case 10 of a particulate filter 200, becomes smaller than a first threshold valve, and it is judged that the filter is damaged when the magnitude of the sound signal becomes larger than a second threshold value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a controller for a diesel particulate filter which collects and incinerates particulates in exhaust gas of a diesel engine.

[0002]

2. Description of the Related Art Since a diesel engine is a heterogeneous combustion in which fuel is injected into the air heated by adiabatic compression to perform combustion, exhaust gas contains a small amount of carbon monoxide and hydrocarbons. However, there is a problem that a large amount of nitrogen oxides (NOx) and particulates (mainly carbon) are discharged.

In order to prevent such particulate matter from being released into the atmosphere, a filter is attached to the exhaust gas passage to collect the particulate matter in the exhaust gas,
Particulate filters have been developed that are incinerated for cleaning. In order to prevent the exhaust pressure from increasing and the output of the diesel engine to drop, the incineration of this particulate must be done at a proper time before the filter collects a certain amount of the particulate and causes clogging. There is. Therefore, in order to judge the time when the particulates should be incinerated, it must be detected by some method whether or not the filter collects a certain amount of the particulates and becomes clogged.

[0004]

[Patent Document 1] Japanese Unexamined Patent Publication No. 4-35321
Japanese Patent Laid-Open Publication No. 0- 009 discloses a method of incinerating particulates by detecting the clogging of the filter with a pressure sensor provided in the exhaust gas passage. However,
In this case, since the pressure sensor is installed on the upstream side of the filter in order to ensure the predetermined pressure range, the particulate matter before collection adheres to the pressure sensor due to long-term operation, and the sensitivity of the sensor is reduced. There is a problem of decrease.

When the filter itself is damaged,
The pressure drops sharply, but with the method using this pressure sensor, whether the filter is clogged and the pressure drops,
Alternatively, it is not possible to separately detect whether the pressure has dropped due to breakage of the filter itself. Therefore, if the filter itself is damaged, it cannot be repaired or replaced, and there is a problem that the particulates and the like are exhausted without being filtered.

As another detection method, by measuring the resistance value of a heater wire or a thermocouple provided for heating the filter to incinerate the collected particulates,
There is a method to detect the clogging of the filter. However, even in this case, it is difficult to detect the state of the filter itself when it is damaged.

The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention that a filter reliably collects a predetermined amount of particulates even during a long-term operation and clogging. It is possible to incinerate the particulates in a timely manner by detecting whether or not it is occurring, and at the same time detecting whether or not only the filter itself is damaged, the particulates are exhausted without being filtered. It is an object of the present invention to provide a controller for a diesel particulate filter which can prevent such a situation.

[0008]

To achieve the above object, according to the present invention, the state of a filter is detected based on a sound signal from a sound sensor provided in a filter case. A controller for a diesel particulate filter is provided.

[0009]

In the controller for the diesel particulate filter of the present invention, the magnitude of the sound signal from the sound sensor provided in the filter case, which is limited to the predetermined frequency bandwidth, is the first. When the threshold value is exceeded, it is determined that the filter is clogged with the particulates collected by the filter, and when the magnitude of the sound signal exceeds the second threshold value, it is determined that the filter is damaged. Therefore, it is possible to incinerate the particulates before the filter is clogged, and it is possible to prevent the particulates from being exhausted without being collected when the filter is damaged. Further, in the controller for the diesel particulate filter of the present invention, since the sound sensor is provided on the downstream side in the filter case, the particulates and the like before collection are used as the sensor due to long-term operation. It does not adhere and the sensitivity of the sensor does not drop extremely.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows a first diesel particulate filter 200 according to the present invention and a control device 10 for the same.
It is sectional drawing of 0. First, the diesel particulate filter 200 in FIG. 1 will be described. As shown in the figure, in the diesel particulate filter 200 of the present embodiment, a cylindrical bypass pipe 11 is arranged in the center of a heat-resistant and steel filter case 10, and a cylindrical bypass pipe 11 is provided outside thereof. Type two-layer laminated main filter 1
2 is arranged, and an exhaust passage 13 is provided further downstream thereof.

A sub-filter 11a is provided downstream of the bypass pipe 11 where a bypass valve 15 to be described later is disposed. The sub filter 11a is composed of a heat-resistant metal tube or a conductive ceramic tube having a large number of bent small holes. Ni, Cr when made of metal
A Fe material containing Fe is coated with a ceramic coat, and when the Fe material is formed of SiC, SiC can be used as the ceramic material. In the bypass pipe 11, the inlet portion and the sub-filter portion may be made of different materials, but they may be made of the same material as a whole.

The laminated main filter 12 has a heat-resistant metal net having a large number of ventilation holes, and a ceramic fiber laminate formed by stacking long ceramic fibers on top of each other, which acts as a filter. And a net-shaped resistor made of a heat-resistant metal material containing Ni-Cr as a main raw material, which is laminated and locked. A ceramic network structure can be used in place of the heat-resistant metal net, and a fiber composite made of a heat-resistant metal net can be used in place of the ceramic fiber laminate.

Bypass pipe 11 and inner laminated main filter 1
2, the upstream side between the outer main laminated filter 12 and the exhaust passage 13, and the two main laminated filters 12
A ring-shaped closing plate 14 is arranged on the downstream side of the space in order to regulate the flow path of the exhaust gas.

A bypass valve 15 for controlling passage / cutoff of exhaust gas is provided near the entrance of the bypass pipe 11. The bypass valve 15 is opened and closed by an actuator 18 via a spring 17 and a valve actuating arm 16.
The operation of the actuator 18 is controlled by the controller 100. The controller 100 is provided with a sound sensor 20 that detects sound on the exhaust gas outlet side.

Since the bypass valve 15 is closed during normal operation and the particulates are collected by the main filter, exhaust gas does not pass through the bypass pipe during normal operation. During normal operation, the exhaust gas is
Flows in from the left side, is fed between the two laminated main filters 12, passes through the main filter 12 as shown by the arrow, and is discharged to the outside of the main filter 12.

When the output signal of the sound sensor 20 is input,
As will be described in more detail below, the controller 100 needs to incinerate the particulates by clogging the filter from each of these signals, or repairing the filter itself because it has been damaged. Judge that it needs to be replaced. If the former judgment is made,
The la 100 has a bypass valve 1 via an actuator 18.
5 is opened, and the heater of the laminated main filter 12 is supplied for a certain period of time to incinerate the particulates collected by the main filter. After that, a small amount of air is allowed to flow with the bypass valve 15 closed or slightly opened, power is supplied to the sub filter 11a, and the particulates collected by the sub filter 11a are incinerated. Also, if the latter decision is made, the controller 100 issues an alarm signal to inform the driver that the filter needs to be repaired or replaced.

Next, the method of detecting the state of the filter by the controller 100 will be described in detail. FIG. 2 is a diagram showing the relationship between the output signal (sound signal) S of the sound sensor 20 provided on the downstream side of the filter case 10 and the frequency f. In the same figure, line A is the characteristic in the initial state just after starting the use of the filter or in the regenerated state in which the filter is free of clogging, and line B is the characteristic in the state in which the filter is clogged by its use. Line C is the characteristic when the filter is damaged. It can be seen that, in any of the states represented by these three lines, the change of the sound signal is large especially in the high frequency region. That is, when the filter is clogged, the amount of sound in the high frequency region leaking to the downstream side of the filter case 10 is reduced, and conversely, when the filter is cracked due to damage, The amount of sound in the high frequency region leaking from the cracked portion to the downstream side of the filter case 10 rapidly increases. The present invention focuses on the fact that the change of the sound signal is large in this high frequency region and detects the state of the filter.

FIG. 3 is a block diagram of a circuit for detecting the state of the particulate filter provided in the controller of the first embodiment of the present invention. In the figure, a high-pass filter 21a for detecting clogging of a particulate filter, a comparison circuit 22a, and a reference voltage generation circuit 2
3a, a high-pass filter 21b for detecting the breakage of the particulate filter, a comparison circuit 22b, and a reference voltage generation circuit 23b.

The output signal of the sound sensor 20 enters the high pass filters 21a and 21b, and the respective high pass filters 2a and 21b.
1a and 21b output only a signal in a predetermined high frequency region in which the low frequency region is cut. At this time, as the high-pass filters 21a and 21b, not only those that output the same high frequency region but also those that output different high frequency regions can be used. That is, a filter that outputs the frequency domain f1 is used for detecting clogging of the particulate filter, and f is used for detecting damage of the particulate filter.
By using the filter that outputs the frequency region f2 different from 1, the difference between the outputs of both can be made clearer and the detection sensitivity can be improved. The outputs of the high-pass filters 21a and 21b are then output to the comparison circuit 22a,
22b, and the comparison circuits 22a and 22b similarly.
Are compared with the reference voltages Va and Vb generated by the reference voltage generation circuits 23a and 23b, respectively. Then, when the voltage is lower or higher than the reference voltages Va and Vb, output signals of a predetermined magnitude are respectively output from the comparison circuits 22a and 22b as discrimination signals.

The reference voltages Va and Vb are determined, for example, as shown in FIG. That is, in FIG. 4, the reference voltage Va is for detecting that the filter is clogged, and the reference voltage Vb is for detecting that the filter is damaged. High pass filter 21
When the magnitude of the output signal of a becomes smaller than the reference voltage Va, the comparison circuit 22a outputs, for example, a "high" signal. In response to this "high" signal, power is supplied to the heater of the laminated main filter 12 to incinerate the particulates collected by the filter. Further, when the magnitude of the output signal of the high pass filter 21b becomes larger than the reference voltage Vb, the comparison circuit 2
2b outputs, for example, a "high" signal. In response to this "high" signal, an alarm is emitted and the driver is given a particulate warning.
Notify that the filter is abnormal. It should be noted that the detection of the filter state by the sound sensor is preferably performed when the engine speed falls within a certain range in order to reduce the influence of the change of the engine sound due to the fluctuation of the engine speed. .

FIG. 5 is a block diagram of a circuit for detecting the state of the particulate filter provided in the control device of the second embodiment of the present invention. The circuit shown in the same figure is for detecting both clogging and damage of the particulate filter by a circuit consisting of a set of high-pass filter 24, comparison circuit 25, and reference voltage generation circuit 26. A timing circuit 27 and an output switching circuit 28 are newly provided.

In order to perform both detections with one set of circuits, the reference voltage generation circuit 26, under the control of the timing circuit 27, has two particulate filter filters for filter clogging detection and filter breakage detection. The reference voltages Va and Vb corresponding to the above state are switched and generated at predetermined time intervals. In response to the timing of the generation of the reference voltage, the output of the comparison circuit 25 is output to the heater power feeding circuit and the alarm generation circuit by the output switching circuit 28 under the control of the timing circuit 27. Output of

The output signal of the sound sensor 20 enters the high-pass filter 24, and the high-pass filter 25 outputs only the signal in a predetermined high frequency region in which the low frequency region is cut. The output of the high-pass filter 24 is then input to the comparison circuit 25 and compared with the reference voltage Va or Vb generated by the reference voltage generation circuit 26 at predetermined time intervals. Then, when the voltage is lower or higher than the reference voltage Va or Vb, the comparison circuit 26 outputs an output signal of a predetermined magnitude as a determination signal at predetermined time intervals. This discrimination signal is sent to the heater power supply circuit or the alarm generation circuit by the output switching circuit 28. The reference voltages Va and Vb are determined similarly to the case shown in FIG. As a result, the state of the filter can be detected by a set of circuits.

FIG. 6 shows a third embodiment of the present invention, in which a new control circuit for detecting the state of the particulate filter 200 provided in the control device of the second embodiment is added. It is a block diagram. The circuit shown in FIG. 10 is such that a sound source 29 and its sound generating circuit 30 are newly provided on the upstream side of the filter case 10 of the particulate filter 200, and the configuration of the other detection circuit is the same as the second detection circuit shown in FIG. The configuration is the same as that of the embodiment. The configuration of FIG. 3 may be used as the configuration of the detection circuit. The high-pass filter 24 is preferably set to output a frequency range corresponding to the frequency range of the sound emitted from the sound source 29 in order to cut off unnecessary noise and improve detection sensitivity.

The sound generating circuit 30 is a detection circuit under the control of the timing circuit 27, and has a particulate filter 20.
When the state of 0 is detected, the signal is sent to the sound source 29, and the sound source 2
A sound in a predetermined frequency range is emitted from 9. The predetermined frequency region is preferably a high frequency region based on the characteristics shown in FIG. 4, but is not limited to this.
The sound emitted from the sound source 29 passes through the particulate filter 200 and enters the sound sensor 20. Sound sensor 2
The subsequent processing of the output signal of 0 is shown in FIG.
Is the same as By thus providing the sound source 29 on the upstream side of the filter case 10, even when the engine speed is not constant and the sound from the engine is greatly changed, the sound emitted from the sound source is generated. By detecting with a sensor, the state of the filter can be reliably detected.

The preferred embodiment has been described above.
The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in the circuit for detecting the state of the particulate filter 200 according to the embodiment of the present invention shown in FIG. 3, one circuit is provided for each instead of using two comparison circuits and a reference voltage generation circuit. The outputs of the two high pass filters may be input to one comparison circuit while being switched by a newly provided switching circuit.
Further, instead of directly comparing the output signal of the high-pass filter and the reference voltage signal, the ratio of two output signals having different frequency regions may be compared with one reference value.

[0027]

As described above, in the controller for the diesel particulate filter of the present invention, the sound signal from the sound sensor provided in the filter case and limited to the predetermined frequency bandwidth. However, when the sound signal exceeds the second threshold, it is judged that the filter is clogged due to the particulates collected by the filter when the first threshold is exceeded. . Therefore, it is possible to incinerate the particulates before the filter is clogged, and it is possible to prevent the particulates from being exhausted without being collected when the filter is damaged. Further, in the controller for the diesel particulate filter of the present invention, since the sound sensor is provided on the downstream side in the filter case, the particulates and the like before collection are used as the sensor due to long-term operation. It does not adhere and the sensitivity of the sensor does not drop extremely. Further, in the controller for the diesel particulate filter of the present invention, since the sound source is provided on the upstream side in the filter case, the engine speed is not constant and the sound from the engine changes greatly. Even in such an operating state, the state of the filter can be reliably detected by detecting the sound emitted from the sound source in the predetermined frequency range with the sound sensor.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a first diesel particulate filter and a control device therefor according to the present invention.

FIG. 2 is a characteristic diagram showing a relationship between an output signal (sound signal) S of a sound sensor provided on the downstream side of the filter case and a frequency f.

FIG. 3 is a block diagram of a circuit for detecting a state of a particulate filter provided in the control device according to the first embodiment of the present invention.

FIG. 4 is a characteristic diagram showing how to determine the reference voltages Va and Vb in the relationship diagram between the output signal (sound signal) S of the sound sensor and the frequency f.

FIG. 5 is a block diagram of a circuit for detecting a state of a particulate filter provided in a control device according to a second embodiment of the present invention.

FIG. 6 is a block diagram of a circuit for detecting a state of a particulate filter provided in a control device according to a third embodiment of the present invention.

[Explanation of symbols]

 10 Filter Case 11 Bypass Pipe 11a Sub Filter 12 Laminated Main Filter 13 Exhaust Path 15 Bypass Valve 20 Sound Sensor 21a, 21b, 24 High Pass Filter 22a, 22b, 25 Comparison Circuit 23a, 23b, 26 Reference Voltage Generation Circuit 27 Timing Circuit 28 Output switching circuit 29 Sound source 30 Sound generation circuit 100 Controller 200 Particulate filter

Claims (7)

[Claims] 1. A controller for a diesel particulate filter, comprising a filter for collecting particulates of exhaust gas of a diesel engine and incinerating the particulates in the filter case. A controller for a diesel particulate filter, which detects the state of the filter based on a sound signal from a sound sensor provided on the downstream side of the filter. 2. A collecting state of the particulates of the filter or a broken state of the filter is detected depending on whether or not the magnitude of the sound signal exceeds a predetermined threshold value. Item 1. A controller for a diesel particulate filter according to Item 1. 3. When the magnitude of the sound signal exceeds a first threshold value, it is judged that the filter is clogged by the particulates collected by the filter, and the filter is heated to be collected. 3. A controller for a diesel particulate filter according to claim 2, wherein an electric current is supplied to a heater provided to incinerate the particulates. 4. The audible signal according to claim 2, wherein when the magnitude of the sound signal exceeds a second threshold value, it is judged that the filter is damaged and an alarm signal is issued. -Zeer particulate filter control device. 5. A filter for outputting only a signal having a predetermined frequency bandwidth from the input sound signal, a threshold value generator for generating the threshold value, and an output of the filter in the control device. A comparator for comparing a value with the threshold value is provided, and a trapped state of the particulate matter of the filter or a broken state of the filter is detected based on an output value of the comparator. A controller for a diesel particulate filter according to claim 2. 6. A first filter for outputting only a signal having a first frequency bandwidth from the inputted sound signal, and a first filter for outputting only a signal having a second frequency bandwidth from the sound signal. 6. The controller for the diesel particulate filter according to claim 5, further comprising two filters. 7. A sound source is provided on the upstream side in the filter case, and a sound is emitted from the sound source while the state of the filter is detected based on a sound signal from the sound sensor. A controller for a diesel particulate filter according to claim 1.