JPH0610409B2 - Engine smoke reduction device - Google Patents

Description

The present invention relates to a smoke reduction device for a diesel engine for construction machinery.

[Conventional technology and its problems]

Conventionally, a construction machine equipped with a diesel engine that operates in a closed place such as a tunnel is equipped with a so-called catalytic muffler for oxidizing and removing harmful components in exhaust gas such as HC and CO. However, in the conventional catalyst muffler, the black smoke particles in the exhaust gas cannot be removed and are actually released into the atmosphere. In order to prevent this, it has been attempted to urge it with a filter or the like, but it is necessary to burn black smoke particles in order to remove the clogging. However, since it is not always possible to obtain a sufficient combustion temperature from the exhaust gas, it is necessary to provide a special superheater, which makes the device large and the control complicated. Also, there is a conventional technique of removing black smoke by passing exhaust gas into water, but there is a problem of water tank capacity and steam generation.

[Means for solving problems]

The present invention has been made to eliminate the above-mentioned conventional drawbacks. Therefore, the smoke reducing device for a diesel engine for construction machinery according to the present invention is for collecting black smoke particles interposed in the exhaust system of the engine. A trap device including a ceramic trap assembly having a honeycomb structure in which a catalyst for lowering a combustion temperature of black smoke is supported on an inner passage wall; a pressure sensor provided at an inlet portion of the trap device; an engine A rotation sensor of; a butterfly valve provided in the intake system of the engine; and a signal from the rotation sensor to determine the exhaust pressure regulation range of the trap device, and compare the exhaust pressure regulation range with the exhaust pressure from the pressure sensor. Under any operating condition, the butterfly valve opening / closing control is performed so that the exhaust pressure in the trap device is maintained within the exhaust pressure regulation range. A controller and an actuator;
It is characterized by comprising an indicator for displaying the exhaust pressure state of the trap device.

[Work]

The controller calculates the exhaust pressure regulation range in the trap device from the engine speed at each time. The exhaust pressure regulation range is
The upper and lower limits are determined so as to correspond to the rate of engine output reduction (for example, about 0 to 5%) that does not substantially affect the actual operation of the construction machine. During the actual operation, when the exhaust pressure from the pressure sensor is within the specified range, the black smoke particles collected by the trap device are burned by the exhaust gas. In actual operation of construction machinery, the exhaust temperature just before the trap device is 50
There are many occasions where the temperature exceeds 0 ° C, and the black smoke trapped in the trap device can be sufficiently combusted during actual operation by the action of the catalyst. However, when black smoke particles accumulate in the trap device due to continued low speed operation and the exhaust pressure exceeds the specified upper limit value, the indicator displays this and the actuator throttles the butterfly valve, which causes the temperature inside the trap device to rise. To accelerate the burning rate of black smoke. When the exhaust pressure from the pressure sensor falls below the specified lower limit value, the actuator fully opens the butterfly valve and restores the normal operating state. This allows the black smoke particles to be controllably combusted by the exhaust gas without substantially affecting the actual operation and without requiring a special heating device.
Further, since the trap device can be regenerated while the ceramic trap assembly is incorporated in the construction machine, serviceability and durability of the device can be improved.

〔Example〕

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

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, in which 1 is a vehicle engine, 3 is a turbocharger connected to an intake system and an exhaust system of the vehicle engine, and 5 is an intake system of the engine. Butterfly valve built into the system, 7
Is an actuator for controlling the opening and closing of the butterfly valve, that is, a solenoid valve, 9 is a precleaner, 11 is an air filter, 13 is a trap device interposed in the exhaust system of the engine, and 15 is a single or a plurality of devices incorporated in the trap device. Ceramic trap assemblies (two in the illustrated example), 17 is a pressure sensor that detects the exhaust pressure at the entrance of the trap device, 19 is a temperature sensor that detects the temperature at the entrance of the trap device, 21 is a rotation sensor of the engine,
The reference numeral 23 determines the exhaust pressure regulation range in the trap device based on the signal from the rotation sensor 21, compares it with the signal from the pressure sensor 17, and compares the signal from the temperature sensor 19 with a preset allowable temperature upper limit value. The actuator 7 so as to open and close the butterfly valve 5 accordingly.
A controller for operating the controller, 25 a mode switch for switching the controller between an automatic regeneration mode and a manual regeneration mode, 27 a manual regeneration switch for opening and closing the butterfly valve when the controller is in the manual regeneration mode, and 29 a trap device. The respective indicators for notifying the operator of the exhaust pressure state and the temperature state of are shown.

As shown in FIGS. 2 and 3, the ceramic trap assembly 15 incorporated in the trap device 13 is a ceramic trap having a honeycomb structure, which is made of a ceramic material having a substantially cylindrical shape as a whole and including a large number of internal passages therein. Including 31. As the ceramic material used for the ceramic trap 31, it is desirable to use a cordierite-based ceramic, which has a good heat resistance and has a proven track record in automobile exhaust gas purifying converters and the like. The inner passage 33 has its inlet and outlet alternately closed by a plugging material 35, whereby the exhaust gas passes through a porous thin wall 37 of the passage as shown by an arrow in the figure, and black smoke particles in the exhaust gas pass through this porous portion. It is collected by a thin wall. Since the collected black smoke particles clog the ceramic trap, it is necessary to burn the black smoke particles to regenerate the ceramic trap.For this reason, the temperature inside the ceramic trap is raised to the combustion reaction temperature of the black smoke particles. I have to. However, in order to raise the temperature of the exhaust gas in the ceramic trap in this way, other equipment such as a burner and a heater must be used, which complicates the apparatus and makes the handling troublesome. Therefore, in the present invention, a catalyst for lowering the combustion reaction temperature of black smoke particles is carried on the porous thin wall 37 of the ceramic trap 31, and the black smoke particles are burned by the exhaust gas. As the above-mentioned catalyst, it is desirable to use a platinum-based catalyst that includes a component that reduces the combustion temperature of black smoke particles while suppressing the production of sulfur components and that also oxidizes harmful components such as HC and CO. The catalyst is supported by, for example, alumina coated on the porous sidewalls of a ceramic trap. According to the experiment, it was confirmed that the black smoke particles burned at around 430 ° C. by using the catalyst, but this temperature appears at a considerable frequency in actual operation of the actual machine, and self-regeneration is sufficiently possible. .

As shown in FIG. 4, the ceramic trap 31 as described above is wrapped around a buffer material 39 such as a thermal expansion seal or a wire mesh and further covered with a metal outer cylinder 41 to form a trap assembly 15. As shown in FIG. 5, one or a plurality (two in the illustrated example) of the assembly 15 is sandwiched between the flanges 43a and 45a of the inlet side manifold portion 43 and the outlet side manifold portion 45 of the exhaust device, and spacers are provided as necessary. This is fixed with a plurality of bolts and nuts 47 through. The ceramic trap 31 is fragile and needs to be held in a vibration-proof manner by a shock-absorbing material 39 such as a thermal expansion seal or a wire mesh, but since the shock-absorbing material expands thermally after use, the ceramic trap 31
It is difficult to take it out from the outer cylinder 41 without breaking it. Therefore, as shown in the figure, the trap assembly 1
By making the outer cylinder 41 replaceable as the unit 5 as a unit, serviceability and maintainability can be improved.
Further, by taking out the outer cylinder together, it is possible to easily perform regeneration outside the machine. Furthermore, by appropriately changing the number of trap assemblies 15 incorporated, it is possible to adapt to systems having different capacities from small vehicles to large vehicles. In FIG. 5, reference numeral 49 is an inlet pipe fixed to the inlet side manifold, 51 is an exhaust gas dispersion plate fixed to the pipe, 53 is an opening provided in the flanges 43a and 45a, and 55 is provided in the outlet side manifold. The respective outlet pipes are shown.

6 and 7 show the contents of control in the present invention by a flow chart. The operation of the device of the present invention will be described below together with the contents of this control.

The control of the device of the present invention includes both the reproduction control shown in FIG. 6 and the temperature control by the timer interruption shown in FIG.

In the regeneration control, first, the butterfly valve 5 is activated when the device is started in the actual operation mode of the construction machine.
Is fully opened, and the indicator lamp green lights up (steps 1 and 2). In this case, the exhaust pressure P at the trap device inlet is the specified lower limit value P calculated by the engine rotation speed at each time.
_If the exhaust pressure P is compared with _L, and the exhaust pressure P is equal to or lower than the specified lower limit value P _L , the valve 5 is kept fully opened and the indicator lamp is continuously lit in green (step 14). The exhaust pressure P is the specified lower limit value P _L
If you leave the automatic reproduction mode by the controller the mode switch 25 if it exceeds the, is compared with predetermined upper limit value P _H prescribed range trap device inlet exhaust pressure P is calculated from the engine rotational speed in each case, exhaust pressure P indicator light green if it is less than predetermined upper limit value P _H is carried out normal operation remains lit (step 3,
4). The specified upper limit value P _H is calculated according to a predetermined formula based on the specified lower limit value P _L and the rotation speed read from the rotation sensor 21 of the engine by the controller 23 at regular intervals (see FIG. 8). In this normal operation state, the black smoke particles collected by the trap device 13 are burned by the exhaust gas introduced into the trap device under the action of the catalyst described above. In a production mode of the construction machine, often exhaust gas temperature of the trap device immediately before exceeds 500 ° C., the black smoke particles are sufficiently combusted by gas, it is hardly to be exhaust pressure P exceeds a predetermined upper limit value P _H.

However, if the black smoke particles trapped in the trap device clog the trap device, such as when the low load operation continues for a long time, the exhaust pressure P rises and the performance of the engine deteriorates. Therefore, in the present invention, in such a case, the black smoke particles in the trap device are forcibly burned to regenerate the trap device.

That is, when the exhaust pressure P exceeds a predetermined upper limit value P _{H (e.g.} corresponding to the discharge pressure to cause the engine output reduction of about 5%), butterfly valve orange indicator light while being illuminated, interposed to the intake system The actuator 7 is actuated so that the valve 5 performs a slight intake throttle (steps 5, 6, 7). Since this automatic regeneration is performed during the actual operation of the construction machine, the butterfly valve 5 cannot be excessively throttled. As a result, the temperature of the exhaust gas in the trap device is raised and the black smoke particles are combusted. In this way, the exhaust pressure P gradually decreases with the forced combustion, and when the exhaust pressure P becomes equal to or lower than the specified lower limit value P _L obtained from the engine rotation speed at each time, the butterfly valve is fully opened to return to normal operation (steps 8 and 1). The specified lower limit value P _L can be set to the exhaust pressure resistance value when the trap device is not substantially clogged. If it is desired to return to normal operation even if the exhaust pressure P does not fall below the specified lower limit value P _L during forced combustion, the automatic regeneration mode may be turned off (steps 9, 10, 1).

In the apparatus of this embodiment, the above-mentioned forced combustion can be performed with the construction machine stopped at a fixed position. In this case, when the exhaust pressure P exceeds the specified lower limit value P _L , the controller is switched to the manual regeneration mode, and the operator turns on the regeneration start switch 27 (steps 6, 11, 9,). 10). That is, when the regeneration start switch 27 is turned on, the butterfly valve 5 is operated by the actuator 7 to perform excessive intake throttling (steps 12 and 15). As a result, the exhaust gas temperature is raised to a higher temperature (for example, 550 ° C.) and the trap device is regenerated in a short time. This forced combustion is continued until the exhaust pressure P reaches the specified lower limit value P _L, and when the exhaust pressure P falls below the specified lower limit value P _L , the butterfly valve is fully opened and returned to normal operation (steps 8 and 1). If it is desired to return to normal operation during the forced combustion, the regeneration switch may be turned off (steps 9, 10, 1).

Even when the exhaust pressure P does not exceed the specified upper limit value P _H , the exhaust pressure P is set to the specified lower limit value P at any time (for example, during regular inspection).
_L can be combusted as much as possible. That is, in this case, the controller is set to the manual regeneration mode, and the operator turns on the regeneration switch to light the orange indicator lamp (steps 3, 13, and 5), and the actuator 7 is operated so that the butterfly valve performs excessive intake throttling. (Step 6,
11, 12). In this case, if the regeneration switch is turned off, the normal operation state is restored (steps 13, 4 or step 1).
1, 4).

FIG. 7 shows a flow chart of exhaust gas temperature control performed by a timer interrupt during regeneration of the trap device in order to prevent overheating of the engine. That is, the controller 23 reads the rotational speed N of the engine from rotational sensor 21 every predetermined time, to calculate the from the rotational speed and the predetermined upper limit value P _H and defining the lower limit value P _L, each time the exhaust gas of the temperature sensor 19 Read the temperature T,
The exhaust gas temperature T and the preset upper limit temperature T
Compare with _MAX (steps 1, 2, 3, 4). If the exhaust gas temperature T is lower than or equal to the upper limit temperature T _MAX , the control ends (step 5). However, when the exhaust gas temperature T exceeds the upper limit temperature T _MAX (step 6), the control differs depending on whether or not the butterfly valve is fully opened. That is, when the butterfly valve 5 is fully opened, the control ends (in this case, additional control such as stopping the vehicle is performed). When the butterfly valve is not fully opened, the butterfly valve is fully opened and the indicator lamp red is turned on at the same time, the exhaust gas temperature T is read again, and the exhaust gas temperature T is set to the preset allowable temperature T _ALW (T _ALW <T _MAX ) (steps 7, 8, 9, 10). And the exhaust gas temperature T is the allowable temperature T
_The control ends when it becomes less than _ALW (step 5).

In the above embodiment, the automatic regeneration mode and the manual regeneration mode can be switched to enable regeneration in the actual operating state and the stopped state of the construction machine. However, in the present invention, only the automatic regeneration mode is used. Good. Further, in the above embodiment, the butterfly valve is controlled to be opened and closed by the signals from both the pressure sensor and the temperature sensor of the trap device, but in the present invention, the control may be performed only by the signal from the pressure sensor. .

[Effect]

As described above, according to the present invention, it is possible to controllably burn the black smoke particles by the exhaust gas without substantially affecting the actual operation, and without requiring a special heating device. Since the trap device can be regenerated while the trap assembly is installed in the construction machine, it is possible to provide a smoke reduction device for a diesel engine that is excellent in serviceability and durability.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the device of the present invention, and FIG.
The figure is a vertical sectional view of a ceramic trap used in the same apparatus, FIG. 3 is an end view of the same ceramic trap, FIG. 4 is a vertical sectional view of a ceramic trap assembly, and FIG. 5 is a trap apparatus used in the same apparatus. FIG. 6 is an enlarged view showing a partial cross section of FIG. 6, FIG. 6 is a flow chart showing the contents of reproduction control in the above-mentioned apparatus, FIG. 7 is a flow chart showing the contents of temperature control in the same apparatus, and FIG.
The figure is a graph showing the relationship between the engine speed and the operating pressure range. 1 ... Engine, 5 ... Butterfly valve, 7 ... Actuator, 13 ... Trap device, 15 ... Ceramic trap assembly, 17 ... Pressure sensor, 19 ...
... Temperature sensor, 21 ... Rotation sensor, 23 ... Controller, 25 ... Mode change switch, 29 ... Indicator, 31 ... Ceramic trap, 33 ... Internal passage, 37 ... Porous thin wall, 39 ... Buffer material, 41 ……
Outer cylinder, 43, 45 ... Manifold part, 57 ... Flange, 59 ... Casing, 61, 63 ... Flange,
65 ... Plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoji Tozawa 1-3-2 Kita-Aoyama, Minato-ku, Tokyo New Caterpillar Mitsubishi Corp. (72) Inventor Masanori Sato 1-3-2 Kita-Aoyama, Minato-ku, Tokyo New Caterpillar Mitsubishi Corporation (72) Inventor Kisaburo Otabe 1-3-2 Kita-Aoyama, Minato-ku, Tokyo New Caterpillar Mitsubishi Corporation (72) Inventor Mamoru Onda 1-3-2 Kita-Aoyama, Minato-ku, Tokyo New Caterpillar Mitsubishi Corp. (56) Reference JP-A-58-187512 (JP, A) JP-A-55-57637 (JP, A) JP-A-60-32918 (JP, A)

Claims (7)

[Claims] 1. A trap device for trapping black smoke particles, which is interposed in an exhaust system of an engine, and has a honeycomb structure in which a catalyst for lowering a combustion temperature of black smoke is carried on an inner passage wall. A trap device including;
A pressure sensor provided at the inlet of the trap device; an engine rotation sensor; a butterfly valve provided in the intake system of the engine; a discharge pressure regulation range of the trap device obtained from a signal from the rotation sensor; A controller for comparing the exhaust pressure from the pressure sensor and the exhaust pressure from the pressure sensor to control the opening and closing of the butterfly valve so that the exhaust pressure in the trap device is maintained within the exhaust pressure regulation range in any operating state. And a smoke reducing device for a diesel engine for construction machinery, which comprises an actuator and an indicator for displaying the exhaust pressure state of the trap device. 2. The smoke reducing device according to claim 1, wherein the opening / closing control of the butterfly valve by the controller and the actuator can be switched so as to be performed in an automatic regeneration mode and a manual regeneration mode. 3. A temperature sensor is provided at the entrance of the trap device, and the controller and the actuator compare the temperature from the temperature sensor with a preset allowable temperature at predetermined time intervals, and the temperature inside the trap device is increased. The smoke reducing apparatus according to claim 1 or 2, wherein the butterfly valve is controlled to be opened and closed so that the temperature is maintained below an allowable temperature. 4. The smoke reduction device according to claim 3, wherein the indicator is adapted to indicate a temperature condition of the trap device. 5. The smoke reducing apparatus according to claim 1, wherein the catalyst comprises a palladium-based catalyst and a base metal-based catalyst. 6. The smoke reducing apparatus according to claim 1, wherein the ceramic trap assembly covers the periphery of the ceramic trap with a cushioning material and further covers the same with a metal cylindrical body. 7. The trap device according to claim 6, wherein the ceramic trap assembly is removably attached between an inlet-side manifold portion and an outlet-side manifold portion of the exhaust device. Smoke reduction device.