JPH07270296A - Particulate weight determining device - Google Patents

Abstract

PURPOSE:To provide an improved particulate weight determining device for accurately determining the particulate weight of a filter for capturing the particulate in an exhaust gas of diesel engine. CONSTITUTION:Based on the detection result from an alternator 22 (exhaust gas flow detection means) and a microwave detection means 18 (electromagnetic wave information detection means), a control means 21 judges and processes the particulate weight captured by a filter 4, thus accurately determining the particulate weight independently of the operational conditions of an internal engine 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an apparatus for treating exhaust gas of a diesel engine (internal combustion engine), and more specifically, it is collected in a filter for collecting and processing particulates contained in the exhaust gas. The present invention relates to a device for determining the collected particulate weight.

[0002]

2. Description of the Related Art Particulates contained in exhaust gas emitted from a diesel engine are mainly SOF (Solu).
ble Organic Fraction), soot, and sulfur compounds.

As a method of treating the particulates in an exhaust system, an oxidation catalyst system for reducing SOF and a system for collecting the particulates using a filter are being advanced. In the oxidation catalyst method, soot cannot be reduced, so that the filter method is preferable in practice.

However, in the filter method, if the particulates are continuously collected, the filter is clogged, the flow of exhaust gas is deteriorated, and the engine output is lowered or the engine is stopped. On the other hand, although technological development for regenerating the trapping ability of the filter is in progress, securing durability is a major practical issue. As a method of regenerating the trapping performance of the filter, we propose a method of burning and removing particulates inside the filter or a method of supplying high pressure air to the filter and blowing the particulates out of the filter to burn out particulates outside the filter. And is being developed. The method of processing outside the filter has a problem in completely removing particulates from the filter, and the mainstream of the regeneration method is a method of burning and removing inside the filter.

Since the particulates burn from about 600 ° C., the temperature inside the filter becomes a considerably high temperature when the particulates are burned and removed. A filter made of a ceramic material has an upper limit of heat resistance, so that melting loss occurs at a combustion temperature equal to or higher than the heat resistance temperature, and cracks occur due to thermal stress due to a temperature difference generated inside. In order to prevent mechanical damage to the filter that accompanies these combustions and to maintain the filter's collection performance, set the particulate weight that allows optimum regeneration for the filter, and collect it inside the filter. Precisely grasp the specified particulate amount (range) against the specified particulate weight (range), consider the surrounding environment including the filter at the time of regeneration, and use the optimal regeneration method based on the grasped particulate weight. It is necessary to perform filter regeneration.

In the above, an indispensable element is to detect the particulate weight trapped in the filter with high accuracy.

As a method for detecting the particulate weight, a method for detecting the pressure before and after the filter to obtain the particulate weight by the filter differential pressure and a microwave characteristic that changes depending on the particulate amount are used to obtain the particulate weight. Methods are being considered.

In the method utilizing the differential pressure, it is necessary to correct the pressure signal detected by the flow rate of exhaust gas and the temperature of the exhaust gas. However, the effect of frequent fluctuations in the engine speed and the accompanying changes in the exhaust gas temperature is considered. It is difficult to accurately detect the weight of the received particulates.

On the other hand, the method using microwaves has an advantage that it can be detected independently of the exhaust gas flow rate. Prior to the present invention, the present applicants proposed a particulate weight detection method using microwaves (Japanese Patent Application No. 5-7291).
issue). The microwave system proposed in advance has a structure in which the detection means for detecting the particulate weight is not exposed to the exhaust gas and guarantees the durability of the detection performance.

[0010]

However, it has been found that the proposed detection method is difficult to perform accurate detection in all practical environments of the internal combustion engine.

The problem arises from the fact that the particulate weight trapped by the filter is judged based on only the detected microwave signal. The actual situation will be described below.

It is known that the properties of particulates discharged from an internal combustion engine change depending on the load condition of the engine. Generally, as the load demanded by the engine increases, the weight percentage of soot in the discharged particulates increases. As a practical environment of the engine, consider a vehicle such as a city bus or a garbage truck that runs in the city. In such a vehicle, since a large load is not continuously used, the particulate matter trapped in the filter has appropriate amounts of SOF, soot and sulfur compounds. The ratio of this appropriate amount varies in various ways, but in any case, within the range assumed in the actual use environment, the method proposed in advance can be used. On the other hand, when a heavy load is used continuously, for example, when working on construction machinery or when traveling uphill in a car requiring a long time, soot occupies most of the weight ratio of the particulate matter discharged from the internal combustion engine. become. Since such so-called dry soot has a light weight and a large particle size, compared to the above-mentioned environment of use, the distribution of particulate intrusion into the filter and the subsequent distribution of collection of particulates relative to the exhaust gas flow. It is possible that changes have also occurred. Furthermore, dry soot itself has a much higher degree of microwave absorption than SOF and sulfur compounds.
As a result of comprehensively combining the characteristics of dry soot and the characteristics of microwaves, there is a problem that a large error is generated when the weight of particulates collected by the filter is determined based only on the detected microwave signal. ing.

The problem is that when the filter is regenerated,
Despite the fact that the actual particulate weight is small, it will be judged that the particulate weight is large based on the detection signal, and in the regeneration process, insufficient heating will occur, resulting in unburned residue without good combustion. Have challenges.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a microwave type particulate weight determination apparatus capable of accurately detecting the weight of particulates collected by a filter in consideration of operating conditions. And

[0015]

In order to solve the above problems, the present invention provides exhaust gas flow detection means for detecting that exhaust gas is flowing through a filter, and electromagnetic wave information of a space containing the filter. Electromagnetic wave information detection means for detecting,
The weight of particulates collected by the filter is determined based on the detection results from these detecting means.

Further, the exhaust gas flow detection means is composed of a means for detecting an electric signal that changes depending on whether the internal combustion engine is operating or a means for detecting the exhaust gas temperature near the filter.

The electromagnetic wave information detecting means is composed of means for detecting the amount of microwaves at a predetermined position in the space containing the filter.

Further, the determination of the particulate weight is performed based on a function having the electromagnetic wave detection value from the electromagnetic wave information detecting means and the exhaust gas flowing time integrated value at the time of the detection as variables.

Further, the determination of the particulate weight has a predetermined particulate weight determination map, and the electromagnetic wave detection value from the electromagnetic wave information detecting means and the exhaust gas flowing time integrated value at the time of the detection are used as the particulate weight. It is performed by collating with the judgment map.

Further, the particulate weight judgment map is constructed by unequally dividing the integrated value of the exhaust gas flowing time. In addition, the weight determination map has an unequal configuration of signal division of the electromagnetic wave detection value.

[0021]

In the above structure, as the weight of particulates increases, the dielectric constant of the filter increases and the length of the wavelength of microwaves in the filter decreases, so that the phase changes at a predetermined position. The position where the microwave detection means is provided is set to a position where the microwave detection value monotonously decreases as the weight of the particulate increases in the desired weight range of the particulate for good filter regeneration.

However, since soot itself has a much higher degree of microwave absorption than SOF and sulfur compounds, the microwave detection value becomes small in the case of particulates having a large soot weight ratio even with the same particulate weight.
Although the actual particulate weight is small, it is determined that the particulate weight is large based on the detection signal.

When a large amount of soot weight in the particulates is discharged, that is, when the load is large during the operation of the internal combustion engine, the particulate discharge amount per unit time also increases. For a given particulate weight, the greater the load on the internal combustion engine (the higher the soot weight ratio),
The particulate weight becomes shorter, the microwave detection value becomes smaller, and the error from the actual particulate weight becomes larger.

Corresponding to this phenomenon, the information on the time during which the exhaust gas is flowing through the filter is also added to the detection value of the microwave detecting means, so that the weight of the particulates is collected even when the particulates having a large soot weight ratio are collected. It has made possible the accurate determination of. Further, since the time required to detect the amount of microwaves is extremely short, for example, about 1/50 second, it is possible to accurately determine the particulate weight independently of fluctuations in the operating conditions of the internal combustion engine.

[0025]

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

In FIG. 1, 1 is an internal combustion engine (diesel engine), 2 is an exhaust pipe for discharging exhaust gas, 3 is a heating space provided in the middle of the exhaust pipe 2, 4 is exhaust gas which is housed in the heating space. A filter having a honeycomb structure for collecting particulates contained in the exhaust gas while passing through the exhaust gas, and 5 are microwave generation means for generating microwaves (electromagnetic waves) for supplying electric power to the heating space for dielectrically heating the particulates. , 6 and 7 are coaxial transmission lines and annular rectangular waveguides for transmitting the microwaves generated by the microwave generating means 5 to the heating space 3, and 8 and 9 are power feeding holes for feeding microwaves to the heating space. Is an antenna for coaxial waveguide conversion. Although only one filter 4 is shown in the figure, the exhaust pipe 2 may be divided into a plurality of parts and a filter may be provided for each.

Reference numeral 11 is a valve for switching the exhaust gas, which normally causes the exhaust gas discharged from the internal combustion engine 1 to flow through the filter 4. When the filter 4 is regenerated, the valve position is switched to exhaust the exhaust gas. Flow through tube 12. 13 is a muffler. 14 is a gas supply means for generating a gas containing oxygen to be supplied into the heating space 3, 15,
Reference numeral 16 is a valve for controlling the flow of a gas containing oxygen to the filter 4, the valve 15 is arranged in a branch pipe 17 which is an exhaust path of the gas passed through the filter 4 during regeneration, and the valve 16 is heated. It is arranged between the space 3 and the exhaust pipe 2 communicating with the atmosphere, and these two valves are controlled so that a gas that promotes the combustion of the particulates heated in the filter 4 when the filter 4 is regenerated is passed.

Reference numeral 18 denotes a microwave detecting means (electromagnetic wave information detecting means) which is provided in the exhaust gas non-circulation space of the filter 4 and detects the amount of microwave existing near the installation space by the operation of the microwave generating means 5. The central conductor 19 of the coaxial line structure is projected into the heating space 3 by a predetermined length. The signal detected by the detecting means 18 is transmitted via the coaxial line 20 to the electronic control unit (EC
It is input to the control means 21 which is U). Reference numeral 22 denotes an alternator (exhaust gas flow detection means), which is an internal combustion engine 1
The output electric signal of the alternator, which changes depending on whether the operation is performed or not, is input to the control means 21. In addition,
Although only one microwave detecting means 18 is shown, a plurality of microwave detecting means 18 may be provided.

Reference numeral 23 is a temperature detecting means (exhaust gas flow detecting means), which is the exhaust pipe 2 between the heating space 3 and the branch pipe 17.
It is provided near the filter 4. When the exhaust pipe 2 is branched into a plurality, a filter is provided in each of the branched exhaust pipes and the temperature detecting means 23 is provided in the vicinity of each filter so that the exhaust gas flows through the target filter. To detect. The temperature detecting means 23 detects the temperature of the gas flowing through the target filter 4 during the filter regeneration process. This detection signal is input to the control means 21.

The heating space 3 has microwave shielding means 24, 25 having a punching hole structure or a honeycomb structure.
Therefore, the space that can substantially contain the microwave is limited. Reference numeral 26 is a heat insulating material provided between the outer periphery of the filter 4 and the tube wall 27 forming the heating space 3, and also serves as a support for the filter 4. Exhaust gas is blocked from flowing through the space in which the heat insulating material 26 is disposed. The microwave detecting means 18 detects the microwave amount at a predetermined position in the space provided with the heat insulating material 26.

28 is a drive power source for the microwave generating means 5,
Reference numeral 29 is a pipe for carrying the gas generated by the gas supply means 14.

The annular rectangular waveguide 7 is an exhaust gas exhaust pipe 30.
The power feeding holes 8 and 9 provided so as to substantially face the pipe wall surface are arranged at the ends. These two feed holes 8, 9 to 18
The coaxial waveguide converting antenna 10 is arranged at a desired position of the annular rectangular waveguide 7 so that the microwave is radiated into the heating space 3 with a phase difference of 0 °.

Further, the microwave detecting means 18 is provided at a position where the detected microwave amount monotonously decreases as the weight of the particulate increases at the desired weight of the particulate. Here, as the weight of the particulates increases, the permittivity of the filter increases and the length of the wavelength of the microwave in the filter decreases, so that the phase at the detection position changes. The basic principle of the particulate weight determination utilizes this phase shift.

In the above construction, the particulate weight determination is executed during the operation of the internal combustion engine 1. The contents of the execution will be described below.

The control means 21 operates the microwave generation means 5 at a predetermined cycle during the operation of the internal combustion engine. And
At a time point after a predetermined time (for example, 10 seconds) has passed since the operation of the microwave generation means 5 was started, the microwave detection means 1
The microwave amount detected by 8 is taken in. The time required to capture this signal is about 1/50 second.

The control means 21 stops the operation of the microwave generation means 5 after taking in the microwave amount. Further, at the timing when the amount of microwaves is taken in, the control means 21 determines whether the integrated value of the time when the alternator 22 is transmitting the output or the time when the temperature level detected by the temperature detecting means 23 is equal to or higher than a predetermined temperature. The integrated value is stored as an integrated value of the time when the exhaust gas flows through the filter 4.

After that, the control means 21 executes a predetermined arithmetic processing or a collation processing with a map which will be described later, based on the received detection signal of the microwave detecting means 18 and the integrated value of the exhaust gas flowing time.

When the particulate weight value obtained by this treatment exceeds a predetermined weight value, the filter 4
The playback process of is executed.

By the way, when the weight of the particulates is too small during the filter regeneration, the combustion propagation of the particulates heated and converted into the combustion state becomes insufficient and a large amount of unburned residue occurs. On the other hand, if the amount is too large, the particulates will be in an abnormally high temperature combustion state, and the filter 4 will overheat and the filter 4 will be melted and cracked. The particulate weight range for avoiding mechanical damage of the filter 4 during such regeneration depends on the time required for regeneration. For a certain regenerating condition on the premise that the regenerating treatment is performed in a short time, the particulate weight range is 4 to 6 g / l (l
Is the volume of the filter. The same applies hereinafter) is the particulate weight that can guarantee the durability of the filter 4, and it is necessary to accurately determine the particulate weight collected by the filter 4, and the present invention enables this determination.

Next, the determination of the particulate weight will be described. FIG. 2 is a diagram showing an example of a change characteristic of the detection value of the microwave detection means 18 with respect to the integrated value of the exhaust gas flowing time when the load is changed under the constant rotation speed of the internal combustion engine 1 (FIG. 2 The solid line inside). (A) is under high load, (B)
Is a characteristic when the load is medium and (C) is a characteristic when the load is low. Further, the group of one-dot broken lines in the same figure is the same weight line of particulates, and the coordinates of the particulate weight from 0 to 12 g / l are shown every 2 g / l. Furthermore, the exhaust gas temperature is 100 for each of several points in the figure.
The detection values (broken line in FIG. 2) of the microwave detection means 18 at temperatures of 400 ° C. and 400 ° C. are shown.

According to the characteristics of FIG. 2, the applicants find that the higher the load of the internal combustion engine 1, the larger the particulate weight with respect to the increment in which the integrated value of the exhaust gas flow time is small.
The higher the exhaust gas temperature is, the smaller the detection value of the microwave detection means is, and even if the particulate weight is the same, the operation of the internal combustion engine at the time of the high load of (A) with a large soot weight ratio is the microwave detection. It was noted that the detection value of the means was low. Then, the same weight line of particulates having the same weight of particulates indicated by the one-dot chain line in FIG. 2 was drawn.
By using a function or a map based on this particulate weight line, the particulate weight is determined from the two variables of the integrated value of the exhaust gas flow time and the detection value of the microwave detection means. It is possible to exclude the error in the determination of the particulate weight due to the difference in the property. Further, even if the exhaust gas temperature changes, the particulate weight judgment error can be suppressed to a small value, so that temperature correction is unnecessary. Further, since the time required to take the detection value of the microwave detection means 18 into the control means 21 is set to about 1/50 seconds, highly accurate particulate weight determination is performed independently of the fluctuation of the operating condition of the internal combustion engine 1. be able to.

The particulate weight determination and the process for shifting to the regeneration execution based on the determination result will be described below.

For the weight determination, a function having two variables, that is, the integrated value of the exhaust gas flow time and the detected value of the microwave detection means, is defined. Based on this preset function, it is determined whether or not the preset particulate weight is exceeded. For example, assuming that the integrated value of the exhaust gas flow time is X and the detected value of the microwave detection means is Y, the line (a) of 4 g / l in FIG.

(Equation 1) Y = aX ^b + c (a, b, and c are constants) In this equation, when the integrated value of exhaust gas flow time is X ₁ and the detected value of the microwave detection means is Y ₁ , Formula 2) If Y ₁ ≧ aX1 ^b + c, it is determined that the particulate weight is 4 g / l or less. (Formula 3) If Y ₁ <aX1 ^b + c, it is determined that the particle weight exceeds 4 g / l. Upon receiving it, playback starts immediately.

The weight determination process can be executed by using a map process. An example of map processing is shown in (Table 1).

[0046]

[Table 1]

This (Table 1) shows a map in which the integrated value of the exhaust gas flow time shown in FIG. 2 and the detected value of the microwave detecting means are mapped as variables. The numerical values in the table are the particulate weight values. With such a map, the absolute value of the particulate weight can be finely determined, and efficient regeneration according to the particulate weight becomes possible.
As a result, the reproducible particulate weight range can be expanded. Here, in the region where the detection value of the microwave detection means is large, the division interval is made coarse. Similarly, even in the region where the integrated value of exhaust gas flow time is large, the division interval is made coarse. As a result, the non-volatile storage capacity of map contents can be reduced (the required capacity in one column is about 2 bytes).

The operation of the above apparatus will be described below with reference to FIG. 1 (Table 1). At the time of collecting particulates, the valve 11, the valve 15 and the valve 16 are controlled to allow the exhaust gas discharged from the internal combustion engine 1 to pass through the filter 4, thereby collecting the particulates contained in the exhaust gas and purifying the exhaust gas. To do. The alternator 22 or the temperature detecting means 23 detects that the internal combustion engine 1 is operating and exhaust gas is flowing through the filter 4, and the exhaust gas flowing time is integrated. In order to determine the particulate weight of the filter 4, the microwave generation means 5 is periodically operated and the detection value of the microwave detection means 18 obtained at that time and the integrated value of the exhaust gas flow time until that time are obtained. The exhaust gas flowing time integrated value and the microwave detection means 18 as shown in (Table 1)
The particulate weight of the filter 4 is determined by collating the detected value of 1 with the particulate weight determination map defined as a variable.

When the amount of the particulates trapped in the filter 4 increases, the pressure loss in the filter 4 increases, the load of the internal combustion engine 1 increases, and in the worst case, it stops. Therefore, it is necessary to remove (filter regeneration) the particulates collected by the filter 4 under an appropriate particulate weight. When the control means 21 determines that the particulate weight has been reached, the filter regeneration is started. When the filter is regenerated, the valve 11, valve 15,
The valve 16 is controlled to bypass the exhaust gas through the exhaust branch pipe 12 while the internal combustion engine 1 is operating. Then, the microwave generation means 5 is operated to dielectrically heat the particulates collected in the filter 4 by the microwaves generated thereby. The gas supply means 14 is operated at a predetermined timing when the particulates are heated to supply gas (natural air may be used) to the heating space 3 including the filter 4, and the particulates are burned to burn the particulates from the filter 4. Remove.

With the above, the regeneration of the filter 4 is completed, the integrated value of the exhaust gas passage time is reset and returned to zero, the valves 15 and 16 are controlled again, and the exhaust gas is passed through the filter 4 just regenerated. Ready to run. After that, the valve 11 is controlled at an appropriate timing to allow the exhaust gas of the internal combustion engine 1 to flow through the filter 4.

The particulate weight determination device according to the present invention can accurately determine the particulate weight independently of the fluctuation of the operating conditions of the internal combustion engine 1, and it is possible to always reproduce under the appropriate particulate weight. This makes it possible to guarantee the durability of the filter 4.

[0052]

As described above, according to the particulate weight determining apparatus of the present invention, the following effects can be obtained.

(1) Exhaust gas flow detecting means for detecting that exhaust gas is flowing through the filter, electromagnetic wave information detecting means for detecting electromagnetic wave information in the space containing the filter, and detection from these detecting means By determining the particulate weight collected by the filter based on the result, it is possible to determine the particulate weight with high accuracy independently of fluctuations in the operating conditions of the internal combustion engine. By using this determination result, the filter performance can be guaranteed for a long time.

(2) The exhaust gas flow detection means is composed of means for detecting electric signals that change depending on whether the internal combustion engine is operating or not, so that the signal directly connected to the operation of the internal combustion engine is used. The flow of gas can be detected accurately.

(3) Since the exhaust gas flow detecting means is constituted by means for detecting the exhaust gas temperature in the vicinity of the filter, even if there is a branch of the exhaust pipe, the exhaust gas flow of the target filter is detected separately. can do.

(4) The electromagnetic wave information detecting means can be treated as a system independent of the exhaust gas of the internal combustion engine by constituting the means for detecting the amount of microwaves, and the signal processing can be efficiently performed.

(5) The particulate weight is determined by a function having the electromagnetic wave detection value from the electromagnetic wave information detecting means and the exhaust gas flowing time integrated value at the time of detection as a variable. It can be easily determined that the curate weight has been exceeded.

(6) The particulate weight judgment has a predetermined particulate weight judgment map, and the electromagnetic wave detection value from the electromagnetic wave information detecting means and the exhaust gas flowing time integrated value at the time of the detection are used as the particulate weight. By performing the comparison with the determination map, the value of the particulate weight trapped in the filter can be known in detail. In addition, efficient regeneration according to the particulate weight becomes possible. As a result, the reproducible particulate weight range can be expanded.

(7) In the particulate weight judgment map, the required capacity of the map storage device can be reduced by making the time division of the exhaust gas flow time integrated value unequal.

(8) The particulate weight determination map can reduce the required capacity of the map storage device by making the signal value division of the electromagnetic wave detection value unequal.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an exhaust gas treatment device including a particulate weight determination device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of the same particulate line of particulates drawn on the characteristic using the integrated value of exhaust gas flow time and the detected value of the microwave detection means as an index showing one embodiment of the present invention.

[Explanation of symbols]

 4 Filter (Target Filter) 18 Microwave Detection Means (Electromagnetic Wave Information Detection Means) 22 Alternator (Exhaust Gas Flow Detection Means) 23 Temperature Detection Means (Exhaust Gas Flow Detection Means)

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshiro Ogino 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Akihiko Nakajima 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (8)

[Claims] 1. Exhaust gas flow detecting means for detecting that exhaust gas is flowing through the filter, electromagnetic wave information detecting means for detecting electromagnetic wave information in the space containing the filter, and detection from these detecting means. A particulate weight determination device for determining the particulate weight collected by the filter based on the result. 2. The particulate weight determination device according to claim 1, wherein the exhaust gas flow detection means is means for detecting an electric signal that changes depending on whether the internal combustion engine is operating or not. 3. The particulate weight determination device according to claim 1, wherein the exhaust gas flow detection means is a means for detecting the exhaust gas temperature in the vicinity of the filter. 4. The particulate weight determination device according to claim 1, wherein the electromagnetic wave information detection means is means for detecting the amount of microwaves at a predetermined position in the space containing the filter. 5. The determination of the particulate weight is performed on the basis of a function having an electromagnetic wave detection value from the electromagnetic wave information detecting means and an exhaust gas flowing time integrated value at the detection time as variables. Particulate weight determination device. 6. The determination of the particulate weight has a predetermined particulate weight determination map, and the electromagnetic wave detection value from the electromagnetic wave information detecting means and the exhaust gas flowing time integrated value at the time of the detection are used as the particulate matter. The particulate weight determination device according to claim 1, which is performed by collating with a weight determination map. 7. The particulate weight determination device according to claim 6, wherein the particulate weight determination map has unequal divisions of the integrated values of the exhaust gas flow time. 8. The particulate weight determination device according to claim 6, wherein the particulate weight determination map has unequal divisions of electromagnetic wave detection values.