JPH0128255Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention collects particulate components (particulate matter) such as unburned carbon contained in the exhaust gas of diesel engines using a catalyst-equipped collection member installed in the exhaust passage. The present invention relates to an exhaust gas purification device for a diesel engine, and particularly relates to a measure for regenerating the catalyst-equipped collection member.

(Prior art) This type of exhaust purification device for a diesel engine is well known in which a collection member (filter member) for collecting particulate components is placed in the exhaust passage. Over time, the collection member may become clogged due to the accumulation of collected particulate components, causing problems such as a reduction in engine output.To deal with this problem, the collection member is periodically cleared from clogging. and play it.

As an example of a method for regenerating such a collection member, conventionally, for example, as disclosed in Japanese Patent Laid-Open No. 56-56921, etc., a collection member disposed in an exhaust passage is regenerated during exhaust gas. an electric heating element (electric heater) that heats the exhaust gas in an exhaust passage upstream of the catalyst-equipped collection member;
A heating means is provided, and the exhaust gas heated by the heating means is guided as regeneration gas to a collection member with a catalyst, and is further raised to a high temperature by an oxidation reaction in the collection member with a catalyst, and this high temperature exhaust gas is A system has been proposed in which particulate components collected in a collection member are removed by combustion.

(Problem to be solved by the invention) By the way, in this proposal, the particulate components are heated and combusted using the heat generated by the re-combustion of the exhaust gas in the catalytic collection member, so the capacity of the heating element of the heating means is reduced. , battery capacity, etc. can be reduced to some extent. However, considering that heating to a high temperature of approximately 600°C or higher is necessary to effectively burn and remove particulate components, it is important to avoid setting the heating element capacity and battery capacity of the heating means too small. It is something that cannot be done.

Therefore, by heating the regeneration gas for heating and regenerating the above-described catalyst-equipped collection member using a combination of an electric heating element and a heat storage material that stores thermal energy from the electric heating element, It is conceivable that the capacity of the electric heating element and the battery can be set smaller than the conventional ones while effectively regenerating the catalytic collection member.

However, in this case, by using a heat storage material, the capacity of the electric heating element and battery is reduced, so it takes a longer time to sufficiently store the thermal energy from the electric heating element in the heat storage material. When the operation is repeated, a problem arises in that the regeneration gas is not heated to a high temperature due to insufficient storage of thermal energy in the heat storage material, and the collection member cannot be regenerated reliably.

(Purpose of the invention) This invention was made in view of the above points,
The purpose of this is to utilize the thermal energy to immediately regenerate the collection member when the temperature of the heat storage material rises above a predetermined temperature due to heat from the engine exhaust gas. The purpose of this invention is to set the capacities of the electric heating element and the battery to a small value while reducing the power consumption of the electric heating element, thereby making it possible to reliably regenerate the collection member.

(Structure of the invention) In order to achieve the above object, the structure of the invention is as follows:
In a diesel engine exhaust purification device comprising a catalyst-equipped collection member for collecting particulate components disposed in the exhaust passage, a catalyst-equipped collection member is provided in the exhaust system upstream of the catalyst-equipped collection member to come into contact with exhaust gas and collect it. A heat storage material that heats regenerated gas to burn and remove particulate components collected by the member; an electric heating element that heats the heat storage material and stores thermal energy; and energizes the electric heating element at predetermined intervals. and a first heating element control means for controlling the heating element. Further, a heat storage material temperature detector detects the temperature of the heat storage material, and when the heat storage material temperature rises to a predetermined value or more based on the output of the heat storage material temperature detector, the electric heat generation is performed even within the predetermined period. A second heating element control means for energizing the body is provided.

As a result, when the temperature of the heat storage material rises above a predetermined value due to heating by exhaust gas during operation of the diesel engine, the collection member is regenerated with priority over other controls.

(Effect of the invention) Therefore, according to the invention, when the temperature of the heat storage material disposed in the exhaust system reaches a predetermined value or more during operation of the diesel engine, the regeneration interval of the collection member has not been reached. The system regenerates the catalytic collection member for collecting particulate components in the exhaust passage by energizing the electric heating element, so the capacity of the electric heating element and battery can be set small by using a heat storage material. However, it is possible to reliably regenerate the collection member even during short engine operation, and it is possible to improve fuel efficiency and output by promoting a reduction in exhaust resistance. It is possible to reduce the power consumption of the catalyst, set the regeneration interval for the catalyst-equipped collection member on the safe side, etc.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows the overall configuration of a diesel engine exhaust purification device according to an embodiment of the present invention, in which 1 is a diesel engine, 2 is an intake passage for supplying intake air to the engine 1, and 3 is an exhaust gas from the engine 1. An exhaust passage for discharging gas to the outside,
A catalyst-equipped collection member 4 is disposed in the middle of the exhaust passage 3 to collect particulate components such as carbon particles in the exhaust gas. The catalyst-equipped collection member 4 is formed in a honeycomb shape from a porous material such as ceramic, the open ends of the honeycomb holes are alternately closed at both ends of the honeycomb body, and the surface in contact with the exhaust gas is coated with a noble metal. Alternatively, an oxidation catalyst made of a base metal is coated, and the exhaust gas flowing in from the opening end of the honeycomb hole at one end passes through a porous partition wall with air permeability and flows out from the opening end of the honeycomb hole at the other end. Particulate components in the exhaust gas are collected by the partition wall, and unburned gas in the exhaust gas is subjected to an oxidation reaction by the oxidation catalyst.

The upstream end of a regeneration gas supply passage 5 is opened in the exhaust passage 3 on the upstream side of the catalyst-equipped collection member 4,
The upstream end of the regeneration gas supply passage 5 is communicated with an air pump 6, and the middle part of the regeneration gas supply passage 5 is connected via the communication passage 7 to the upstream side of the connection part of the exhaust passage 3 with the downstream end of the regeneration gas supply passage 5. is communicated with. Further, an upstream end of an exhaust bypass passage 8 is opened between the connection part of the exhaust passage 3 with the downstream end of the regeneration gas supply passage 5 and the connection part with the communication passage 7, and the downstream end of the exhaust bypass passage 8 is opened to the exhaust passage 3 on the downstream side of the collecting member 4.

Further, at the connection part of the exhaust passage 3 with the communication passage 7, a normally closed electromagnetic first on-off valve 9 whose opening degree can be adjusted is provided.
is disposed, and the first on-off valve 9, in the closed state, cuts off communication between the communication passage 7 and the exhaust passage 3, and allows the exhaust passages 3, 3 on the upstream and downstream sides of the first on-off valve 9 to communicate with each other, When opened as shown by the imaginary line in the figure, the communication passage 7 is communicated with the exhaust passage 3 on the upstream side of the first on-off valve 9, and communication between the exhaust passages 3, 3 on the upstream and downstream sides of the first on-off valve 9 is cut off. Open and close as shown. Further, a normally closed electromagnetic second on-off valve 10 whose opening degree is adjustable is disposed at the connection portion of the exhaust passage 3 with the upstream end of the exhaust bypass passage 8.
In the closed state, the exhaust bypass passage 8 is cut off from communicating with the exhaust passage 3, and the second on-off valve 10 is closed.
When the upstream and downstream exhaust passages 3 and 3 are communicated with each other and opened as shown by the imaginary line in the figure, an exhaust bypass passage 8 is formed.
is opened and closed so as to communicate with the exhaust passage 3 on the upstream side of the second on-off valve 10, and to block communication between the exhaust passages 3, 3 on the upstream and downstream sides of the second on-off valve 10. Furthermore, a normally closed electromagnetic third on-off valve 11 for opening and closing the regeneration gas supply passage 5 is disposed downstream of the connection portion of the regeneration gas supply passage 5 with the communication passage 7 . By opening the full opening/closing valves 9 to 11, the exhaust gas from the engine 1 is converted into the communication passage 7 and the regeneration gas supply passage as regeneration gas for burning and removing particulate components collected by the catalyst-equipped collection member 4. 5 to the collection member 4, and also closes the first on-off valve 9 and closes the second and third on-off valves 10, 1.
By operating the air pump 6 with 1 open, air discharged from the air pump 6 is supplied to the collection member 4 through the regeneration gas supply passage 5.

Further, an electric heating element 12 (heater) that generates heat when energized is embedded between the connection part of the regeneration gas supply passage 5 with the communication passage 7 and the third on-off valve 11, and the electric heating element 12 is embedded and sealed. Formed heat storage material 1
3 are arranged. The heat storage material 13 is, for example, a molten salt such as a phosphate having a melting point of around 200 to 300°C or a mixed salt of potassium nitrate and sodium nitrite, or Teflon plastic or wood metal (low melting point alloy) having a melting point of about 200°C. etc., and is heated by the electric heating element 12 to generate the electric heating element 12.
The regenerating gas (exhaust gas of the engine 1) is provided to heat the regenerated gas (exhaust gas of the engine 1) by storing the generated thermal energy and radiating the heat.

On the other hand, 14 is a battery that supplies power to the air pump 6, the actuators of the first to third on-off valves 9 to 11, and the electric heating element 12, 15 is an electromagnetic switch for the air pump that controls ON/OFF of the air pump 6, and 16 is the same. This is a voltage transformation device that changes the voltage applied to the air pump 6 to increase or decrease the rotational speed of the air pump 6, that is, the amount of air discharged. Also, 17
18 is a second on-off valve electromagnetic switch that controls opening and closing of the first on-off valve 10; 19 is a second on-off valve electromagnetic switch that controls opening and closing of the third on-off valve 11; 3. An electromagnetic switch 20 for the opening/closing valve is a heating element electromagnetic switch for controlling the operation of the electric heating element 12, and each of the electromagnetic switches 15, 17 to 20 is normally in an OFF state.

Further, 21 is an exhaust gas temperature detector installed in the exhaust passage 3 immediately upstream of the catalyst-equipped collection member 4 to detect the exhaust gas temperature T _E , and 22 is an exhaust gas temperature detector immediately downstream of the catalyst-equipped collection member 4. an oxygen concentration detector for detecting the oxygen concentration in the exhaust gas, which is temporarily installed in the exhaust passage 3 of the
23 is a heat storage material temperature detector embedded in the heat storage material 13 for detecting the heat storage material temperature T _R ; 24 is a heat storage material temperature detector embedded in the heat storage material 13; 24 is a heat storage material temperature detector embedded in the heat storage material 13; The clogging detector 24 detects the electric resistance value between two electrodes 25, 25 embedded in the collecting member 4 at a predetermined interval in the axial direction thereof. is measured, and it is determined that the electrical resistance value has decreased to a predetermined value or less due to an increase in the electrical conductivity of carbon particles, which are the main component, as the particulate components are deposited on the collection member 4. This is used to detect clogging conditions.

Furthermore, 26 is the exhaust gas temperature detector 21,
In response to the outputs from the oxygen concentration detector 22, heat storage material temperature detector 23, and clogging detector 24, the transformer 16 and each electromagnetic switch 15, 17-2
0, the control circuit 26
has a built-in microcomputer, which processes the output signals from each of the detectors 21-24 and outputs predetermined control command signals to the transformer 16 and the electromagnetic switches 15, 17-20. This control circuit 26 controls the collection member 4 detected by the clogging detector 24.
It constitutes a first heating element control means that energizes the electric heating element 12 at predetermined intervals represented by a clogging state, and also controls the heat storage material temperature T _R detected by the heat storage material temperature detector 23. , within the above-mentioned predetermined period when the collection member 4 is heated to a temperature higher than the first set temperature T ₁ which is lower than the second set temperature T ₂ which is higher than the regeneration temperature T ₀ and which is lower than the regeneration temperature T ₀ . A second heating element control means is configured to control the electric heating element 12 to be energized even if

Next, the operation of the above embodiment will be explained with reference to the control flowchart shown in FIG.

After the control flow starts, first, in step _S1 , it is determined whether the exhaust gas temperature T _E detected by the exhaust gas temperature detector 21 is higher than the heat storage material temperature T _R detected by the heat storage material temperature detector 23. conduct. If this judgment is NO, where T _E ≦ T _R , the step is
Proceeding to _S2 , the first to third on-off valves 9 to 11 are all kept closed to allow exhaust gas from the engine 1 to flow through only the exhaust passage 3 to the catalyst-equipped collection member 4. On the other hand, the determination in step _S1 above is T _E >
When _TR is YES, the process moves to step _S3 , where the first and third on-off valves 9 and 11 are opened, and the second
By closing the on-off valve 10, the exhaust gas is passed through the communication path 7 and the regeneration gas supply path 5 to the heat storage material 13.
Flow to the side. In the above state, particulate components such as carbon in the exhaust gas are collected by the collection member 4, and unburned gas is oxidized by the catalyst of the collection member 4, thereby purifying the exhaust gas. . In addition, since the exhaust gas flows to the heat storage material 13 side only when the exhaust gas temperature T _E is higher than the heat storage material temperature T _R , the heat storage material 1
3 can be heated to raise the temperature.

After this, in step _S4 , the temperature of the heat storage material is
It is determined whether T _R is equal to or higher than the first set temperature T ₁ , and if this determination is NO (T _R < T _{1 )} , the process moves to step S ₅ and the regeneration interval of the collection member 4 reaches the set interval. In other words, the fine particle components collected by the collection member 4 cause the electrode 2 to
It is determined whether the electric resistance value between 5 and 25 has decreased to a predetermined value or less and the clogging detector 24 is outputting a clogging signal indicating that the collection member 4 is clogged. If the determination at step _S5 is NO, the process returns to step _S1 to repeat the control flow. If the determination in step _S4 is YES, the process immediately enters the next step _S6 and subsequent regeneration preparation steps. Further, when the determination in step _S5 is YES, the reproduction preparation process is also entered.

In the regeneration preparation step, first, in step _S6 , the electric heating element 12 is energized to generate heat to heat the heat storage material 13, and the thermal energy generated by the heating element 12 is stored in the heat storage material 13. After this, step S ₇
It is determined whether the exhaust gas temperature T _E is higher than the heat storage material temperature T _R , and this determination is T _E ≦ T _R.
If NO, the process moves to step _S8 , and the first to third on-off valves 9 to 11 are all kept closed to allow the exhaust gas to flow through the exhaust passage 3 to the collection member 4 side. When the determination is YES, that is, T _E > T _R , the process moves to step S ₉ , and the first and third on-off valves 9 and 11 are opened, and the second on-off valve 10 is closed, thereby transferring the exhaust gas to the communication path 7 and supplying regeneration gas. It flows through the passage 5 to the heat storage material 13 side. This prevents the heat storage material 13 from being cooled by exhaust gas having a temperature lower than the temperature T _R thereof, thereby increasing the heat storage efficiency of the heat storage material 13.

Next, in step _S10 , the temperature of the heat storage material is
It is determined whether T _R has reached the second set temperature T ₂ or higher. If this determination is NO (T _R < T _{2 )} , the process returns to step S ₇ and performs the subsequent steps S ₈ ,
Repeat S ₉ . When the above judgment becomes YES with T _R ≧T ₂ , the regeneration process begins.

In this regeneration process, first, in step _S11 , it is determined whether the exhaust gas temperature T _E of the engine 1 is higher than the regeneration temperature T ₀ at which the collection member 4 can be heated and regenerated. NO of _E ≦T ₀
If so, in step _S12 , a part of the exhaust gas is transferred to the regeneration gas supply passage 5 by closing the second on-off valve 10, opening the third on-off valve 11, and adjusting the opening degree of the first on-off valve 9. The heat storage material 13 heated to the second set temperature T ₂ or higher in the regeneration gas supply passage 5 is heated until the regeneration temperature T ₀ is reached, and then returned to the exhaust passage 3 to bring the entire exhaust gas to the regeneration temperature T Heat to ₀ . The exhaust gas heated to the regeneration temperature T ₀ becomes regeneration gas and flows into the collection member 4 to heat and burn the particulate components collected in the collection member 4 .

On the other hand, if the determination in step _S11 is YES, that is, T _E > T ₀ , all the first to third on-off valves 9 to 11 are closed in step _S13 , and the high-temperature exhaust gas is directly converted into regenerated gas. It is made to flow through the exhaust passage 3 to the collection member 4 side.
As a result, the particulate components collected by the collection member 4 are heated and burned and removed in the same way as described above.

After step _S12 or step _S13 , in step _S14 ', the two electrodes 25, 2
It is determined whether or not the electrical resistance value between the collection members 4 and 5 is greater than or equal to a predetermined value.
(when the clogging is cleared), proceed to step _S16 . Also, if the electrical resistance value is less than the specified value,
, move to step S ₁₄ ″.
In _S14 '', it is determined whether the oxygen concentration in the exhaust gas detected by the oxygen concentration detector 22 is below the set value.If this determination is NO, that is, the oxygen concentration in the exhaust gas is When the amount of oxygen remaining in the exhaust gas discharged from the engine 1 is higher than the set concentration even after the particulate components have been combusted in the regenerated state of the collection member 4, oxygen for the combustion of the particulate components is present in the exhaust gas discharged from the engine 1. Assuming that the air pump 6 is satisfied, in step _S15 ', the operation of the air pump 6 is stopped (that is, if the air pump 6 is in a stopped state, it is maintained stopped, and if the air pump 6 is in an operating state, it is stopped). Therefore, the power supply to the air pump 6 is stopped via the electromagnetic switch 15.Then, the process returns to step _S11 and the subsequent control flow is repeated.On the other hand, when the determination in step _S14 '' is YES, that is, the collection If the oxygen concentration in the exhaust gas after passing through member 4 is below the set concentration, it is assumed that there is insufficient oxygen in the exhaust gas from engine 1 to burn the particulate components sufficiently, and the next step S is performed. In order to replenish the oxygen deficiency in the exhaust gas at ₁₅ ″ and keep the concentration within the set value,
The opening degree of the second on-off valve 10 is adjusted with the first on-off valve 9 closed and the third on-off valve 11 opened, and the amount of air discharged is adjusted by energizing the air pump 6 and controlling its voltage. Thereby, the particulate components collected by the collection member 4 can be reliably burned and removed under a sufficient amount of oxygen (air). After that, the process returns to step _S11 and repeats the control flow, and when the determination in step _S14 ' becomes YES and the regeneration of the collection member 4 is completed, the process returns to the final step.
One cycle of the control flow is completed after the electric heating element 12 and the air pump 6 are deactivated in _S16 .

Therefore, in this case, the thermal energy from the electric heating element 12 is gradually stored in the heat storage material 13 during the regeneration preparation process for the catalyst-equipped collection member 4, and the thermal energy stored in the heat storage material 13 is used during regeneration. Since the exhaust gas (regeneration gas) of the engine 1 is heated to the regeneration temperature T ₀ by Since less energy is required, the heat generating capacity of the electric heating element 12 and the electric capacity of the battery 14 can be set small.

In addition, when the heat generation capacity of the electric heating element 12 and the electric capacity of the battery 14 decrease in this way, the regeneration preparation time of the collection member 4, that is, the time required until the heat storage material 13 rises to a predetermined temperature or higher, increases by the amount corresponding to the decrease. When the time becomes longer and the short-time operation pattern of stopping the operation of the engine 1 during the elapse of the regeneration preparation time is repeated, the heat storage material 13
There is a shortage of thermal energy stored in the trap, making it difficult to properly regenerate the collection member 4. However, in this embodiment, when the heat storage material 13 is heated by the exhaust gas heat of the engine 1 and its temperature T _R rises above the first set temperature T ₁ , even if the regeneration interval of the collection member 4 has not been reached. Since the electric heating element 12 is energized and moves to the regeneration preparation process and the subsequent regeneration process for the collection member 4, sufficient thermal energy can be stored in the heat storage material 13 just by making the electric heating element 12 generate heat with a small amount of heat. This means that the collection member 4 can be reliably regenerated, and fuel consumption and output can be improved by promoting reduction in exhaust resistance. Moreover, by this, the power consumption by the electric heating element 12 can be significantly reduced, and the regeneration interval of the collection member 4 can be set on the safe side.

In the above embodiment, the exhaust gas of the engine 1 is used as the regeneration gas for regenerating the collection member 4, but the air discharged from the air pump 6 may be heated by the heat storage material 13 and used as the regeneration gas. .

In the above embodiment, the first heating element control means detects clogging of the collection member 4 by a decreasing change in the electric resistance value between the electrodes 25, 25, and energizes the electric heating element 12 to collect the clogging. Although the member 14 is regenerated, the present invention looks at the pressure difference between the upstream and downstream sides of the collection member in the exhaust passage and determines that the collection member is clogged when the pressure difference increases. Of course, it is also possible to change to one in which the collection member is periodically regenerated when the cumulative value of fuel consumption, engine operating time, etc. exceeds a certain value. It is.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is an overall configuration diagram, and FIG. 2 is a flowchart of a control system. DESCRIPTION OF SYMBOLS 1... Engine, 3... Exhaust passage, 4... Collection member with catalyst, 6... Air pump, 9... First on-off valve, 10... Second on-off valve, 11... Third on-off valve,
12... Electric heating element, 13... Heat storage material, 21...
Exhaust gas temperature detector, 22...Oxygen concentration detector,
23... Heat storage material temperature detector, 24... Clogging detector, 26... Control circuit.

Claims (1)

[Scope of utility model registration request] In an exhaust purification device for a diesel engine, which includes a catalyst-equipped collection member for collecting particulate components such as carbon particles in the exhaust passage, the catalyst-equipped collection member is disposed in the exhaust system upstream of the catalyst-equipped collection member, and is arranged in the exhaust system on the upstream side of the catalyst-equipped collection member. a heat storage material that heats regeneration gas for burning and removing collected particulate components; an electric heating element that heats the heat storage material and stores thermal energy; a heat storage material temperature detector that detects the temperature of the heat storage material; and a heat storage material temperature detector that receives the output of the heat storage material temperature detector, and when the heat storage material temperature rises to a predetermined value or higher, the heat storage material temperature detector detects the temperature of the heat storage material. An exhaust gas purification device for a diesel engine, comprising: second heating element control means for energizing the electric heating element even within the period.