JPH01106917A - Method for smoke reduction of engine - Google Patents

Abstract

PURPOSE:To prevent the blinding of a trap by controlling the butterfly valve of a intake system to open and close in comparing the exhaust pressure within a trap device with the upper and lower limit values of a specified range. CONSTITUTION:A pressure sensor 17 is provided at the entrance of a trap device 13. The exhaust pressure specifying range is found cut from the signal of a rotational speed sensor 21. When the exhaust pressure from the pressure sensor 17 exceeds the upper limit value of a specified range, the butterfly valve of an intake system is throttled, and when it is below the lower limit value, the butterfly valve 5 is opened completely. By this manner, the black particles within the trap device are burnt and the blinding of the trap can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for reducing smoke in a diesel engine.

[Conventional technology and its problems] Conventionally, construction machines equipped with diesel engines that operate in closed spaces such as tunnels are equipped with so-called catalytic mufflers to oxidize and remove harmful components in exhaust gas such as HC and CO. ing. However, the reality is that conventional catalyst mufflers cannot remove black smoke particles from exhaust gas and emit them into the atmosphere.

Attempts have been made to prevent this from occurring (capturing it with filters, etc.), but in order to remove the clogging, it is necessary to burn the black smoke particles. However, it is not always possible to obtain a sufficient combustion temperature from the exhaust gas temperature. Therefore, it is necessary to install a special heating device, which makes the device large-scale and complicated to control.Also, there is a conventional technology that removes black smoke by passing the exhaust gas through water, but there are problems with the capacity of the water tank and steam There are problems such as occurrence.

[Means for Solving the Problems] The present invention has been made to eliminate the above-mentioned drawbacks of the conventional technology.For this reason, the smoke reduction method according to the present invention provides a method for reducing black smoke on the internal passage wall in the exhaust system of the engine. A trap device for collecting black smoke particles is installed, which includes a ceramic trap assembly with a honeycomb structure supporting a catalyst that lowers the combustion temperature of the engine; a pressure sensor is provided at the inlet of the trap device; The specified exhaust pressure range of the trap device is determined from the speed signal of the trap device, the specified exhaust pressure range is compared with the exhaust pressure from the pressure sensor, and the exhaust pressure within the trap device is determined to be within the specified upper limit of the specified exhaust pressure range. The burning speed of black smoke particles in the trap device is controlled by throttling the butterfly valve when the exhaust pressure exceeds the specified lower limit and fully opening the butterfly valve when the exhaust pressure falls below the specified lower limit.

[Function] The controller calculates the exhaust pressure regulation range in the trap device from the engine rotation speed each time. During actual operation, if the exhaust pressure from the pressure sensor is within the above specified range, the black smoke particles collected by the trap device are burned by the exhaust gas. During actual operation of construction machinery, there are many occasions when the exhaust temperature just before the trap device exceeds 500℃, and the black smoke collected in the trap device can be sufficiently combusted during actual operation because the combustion temperature is lowered by the action of the catalyst. It is. However, if black smoke particles accumulate in the trap device due to continued low-speed operation and the exhaust pressure exceeds the specified upper limit, the actuator throttles the butterfly valve, thereby increasing the temperature inside the trap device and burning the black smoke. Promote speed. When the exhaust pressure from the pressure sensor falls below a specified lower limit, the actuator fully opens the butterfly valve to return to normal operating conditions.

This allows controllable combustion of black smoke particles by exhaust gas without the need for special heating equipment. Furthermore, since the trap device can be regenerated while the ceramic trap assembly is still installed in the construction machine, serviceability and durability of the device can be improved.

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

FIG. 1 is a schematic diagram showing an example of a device for implementing the method of the present invention, in which 1 is a vehicle engine, 3 is a turbocharger connected to the intake system and exhaust system of the vehicle engine, and 5 is a turbocharger connected to the vehicle engine. A butterfly valve incorporated in the intake system of the engine, 7 an actuator or solenoid valve that controls opening and closing of the butterfly valve, 9 a pre-cleaner, 11 an air filter, 13 a trap device installed in the engine exhaust system, 15 17 is a pressure sensor that detects the exhaust pressure at the inlet of the trap device; 19 is a pressure sensor that detects the temperature at the inlet of the trap device; A temperature sensor 21 detects the exhaust pressure in the trap device based on a signal from the rotation sensor 21, and compares this with a signal from the pressure sensor 17. A controller that compares the signal with a preset upper limit temperature and an allowable temperature and operates the actuator 7 to open and close the butterfly valve 5 accordingly, and 25 is a mode that switches the controller between automatic regeneration mode and manual regeneration mode. A selector switch 27 is a manual regeneration switch that controls opening and closing of the butterfly valve when the controller is in manual regeneration mode, and 29 is an indicator that informs the operator of the exhaust pressure state and temperature state of the trap device.

As shown in FIGS. 2 and 3, the ceramic trap assembly 15 incorporated in the trap device 13 includes a ceramic trap 31 having a honeycomb structure made of a ceramic material that has a generally cylindrical shape and includes a large number of passages inside. including. As the ceramic material used for the ceramic trap 31, it is desirable to use cordierite ceramic, which has good heat resistance and has a proven track record in converters for purifying automobile exhaust gas. The internal passage 33 has its inlet and outlet alternately closed with plugging material 35, so that the exhaust gas passes through the porous thin wall 37 of the passage as shown by the arrow in the figure.
Black smoke particles in the exhaust gas are collected by this porous thin wall. The collected black smoke particles clog the ceramic trap, so it is necessary to burn the black smoke particles to regenerate the ceramic trap.To do this, the inside of the ceramic trap is raised to the combustion reaction temperature of the black smoke particles. Must be. However, increasing the exhaust gas temperature within the ceramic trap in this manner requires the use of other equipment such as burners and heaters, making the device complex and difficult to handle. Therefore, in the present invention, the porous thin wall 37 of the ceramic trap 31 supports a catalyst that lowers the combustion reaction temperature of the black smoke particles, so that the black smoke particles are combusted by the exhaust gas. The above catalyst lowers the combustion temperature of black smoke particles while suppressing the production of sulfur components.
It is also desirable to use a platinum-based catalyst that also contains components that oxidize harmful components such as HC and CO. The catalyst is supported, for example, by alumina coating on the porous sidewalls of the ceramic trap. According to experiments, it was confirmed that black smoke particles burn at around 430°C when a catalyst is used, but this temperature is a temperature that occurs quite frequently in actual operation of actual equipment, and self-regeneration is fully possible. .

As shown in FIG. 4, such a ceramic trap 31 is wrapped around it with a buffer material 39 such as a thermal expansion seal or wire mesh, and then covered with a metal outer cylinder 41 to form a trap assembly 15. As shown in FIG. 5, one or more (two in the illustrated example) No. 15 are attached to the flanges 43a, 45 of the inlet-side manifold portion 43 and the outlet-side manifold portion 45 of the exhaust system.
a and fix it with a plurality of bolts and nuts 47 via a spacer if necessary. The ceramic trap 31 is easily broken and needs to be held in a vibration-proof manner with a buffer material 39 such as a thermal expansion seal or wire mesh, but since the buffer material expands thermally after use, the ceramic trap 31 itself cannot be broken from the outer cylinder 41. It is difficult to take it out without losing it. Therefore, serviceability and maintainability can be improved by making the trap assembly 15 as a unit and making the outer cylinder 41 replaceable. Furthermore, by taking out the entire outer cylinder, it can be easily regenerated outside the machine. Furthermore, by appropriately changing the number of trap assemblies 15 installed, it is possible to adapt the system to systems with different capacities, from small vehicles to large vehicles. In addition, in FIG. 5, 49 is an inlet vibrator 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 exit vibrators are shown respectively.

FIGS. 6 and 7 show the contents of the controls in the present invention using flowcharts. Hereinafter, the operation of the present invention will be explained along with the contents of this control.

Controls in the present invention include both the playback control shown in FIG. 6 and the timer interrupt temperature control shown in FIG.

In regeneration control, first, when the system is started in the actual operation mode of the construction machine, the butterfly valve is fully opened and the indicator lamp lights up in green (step 1).
,2). In this case, the exhaust pressure P at the inlet of the trap device is a specified lower limit value P calculated based on the engine rotation speed at each time,
If the exhaust pressure P is less than the specified lower limit value PL, the valve 5 is fully opened and the indicator lamp continues to be lit in green (step 14). The exhaust pressure P is the specified lower limit value PL
If the exhaust pressure P at the trap device inlet is exceeded, the controller 23 is set to automatic regeneration mode by the mode changeover switch 25, and the exhaust pressure P at the trap device inlet is compared with the specified upper limit value PH of the specified range calculated from the engine rotational speed at each time. If the exhaust pressure P is below the specified upper limit value, normal operation is performed with the indicator lamp green lit (step 3,
4). The specified upper limit value PH, together with the specified lower limit value P, is calculated by the controller 23 according to a predetermined formula based on the rotation speed read from the engine rotation sensor 21 at regular intervals (see FIG. 8).

In this normal operating state, the black smoke particles collected by the trap device 13 are combusted by the exhaust gas introduced into the trap device under the action of the catalyst described above.

In the actual operation mode of construction machinery, the exhaust gas temperature immediately before the trap device often exceeds 500° C., the black smoke particles are sufficiently combusted by the exhaust gas, and the exhaust pressure P rarely exceeds the specified upper limit value P1□.

However, if the trap device is clogged with black smoke particles captured by the trap device due to prolonged low-load operation, the exhaust pressure P increases and engine performance deteriorates. Therefore, in the present invention, the graphite particles in the trap device are forcibly burned to regenerate the trap device when it burns.

That is, when the exhaust pressure P exceeds the specified upper limit PH (corresponding to the exhaust pressure that causes a drop in engine output of about 5%, for example), an orange indicator lamp lights up and the butterfly valve 5 installed in the intake system lights up. The actuator 7 is actuated so that the intake air is slightly throttled (steps 5, 6 and 7). Since this automatic regeneration is performed during actual operation of the construction machine, the butterfly valve 5 cannot be throttled down excessively. As a result, the temperature of the exhaust gas within the trap device is raised, and the black smoke particles are forced to burn.

In this way, the exhaust pressure P gradually decreases with forced combustion, and when it falls below the specified lower limit value PL determined from the engine speed each time, the butterfly valve is fully opened and normal operation is returned to (Step 8, l). The lower limit value P can be, for example, the exhaust pressure resistance value when the trap device is hardly clogged. Even if the exhaust pressure P does not fall below the specified lower limit value Pt during forced combustion, if you want to return to normal operation, you can turn off the automatic regeneration mode (steps 9 and 10.1).

The forced combustion described above can also be performed with the construction machine stopped in a fixed position. In this case, the exhaust pressure P is the specified lower limit value P
This can be done by switching the controller to manual regeneration mode in a state where L is exceeded, and the operator turns on the regeneration start switch 27 (steps 6 and 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 excessively throttle the intake air (step 12.
15).

This raises the exhaust gas temperature to a higher temperature (for example, 550° C.) and regenerates the trap device in a short time. This forced combustion continues until the exhaust pressure P reaches the specified lower limit P, and when the exhaust pressure P falls below the specified lower limit PL, the butterfly valve is fully opened and normal operation is resumed (step 8.
1). Also, if you want to return to normal operation during forced combustion, just turn off the regeneration switch (steps 9 and 10.1).
).

In addition, even if the exhaust pressure P does not exceed the specified upper limit P, the exhaust pressure P may be changed from time to time (for example, during periodic inspection) to the specified lower limit P.
, so that it can be forced to burn as much as possible. In other words, in this case, the controller is set to manual regeneration mode, and when the operator turns on the regeneration switch, the orange indicator lamp lights up (step 3).
, 13°5), the actuator 7 is actuated so that the butterfly valve performs excessive intake throttling (step 6°1).
1, 12). In this case, if the regeneration switch is turned off, the normal speed rotation state is returned (step 13.4 or step 11).
．． 4).

FIG. 7 shows a flowchart of exhaust gas temperature control performed by timer interrupt during regeneration of the trap device to prevent engine overheating. That is, the controller 23 reads the engine rotation speed N from the rotation sensor 21 at regular intervals, calculates the specified upper limit value PH and the specified lower limit value PL from this rotation speed, and calculates the exhaust gas temperature T at each time from the temperature sensor 19. Load,
The exhaust gas temperature T and the preset upper limit temperature TM
AX (steps 1.2, 3.4).

If the exhaust gas temperature T is below the upper limit temperature TMAX, the control ends (step 5). However, if the exhaust gas temperature T exceeds the upper limit temperature TMAX (step 6), the control differs depending on whether the butterfly valve is fully opened or not. That is, if the butterfly valve 5 is fully open, the control ends (in this case, additional control such as stopping the vehicle is performed). If the butterfly valve is not fully open, the butterfly valve is fully opened and the red indicator lamp lights up at the same time, the exhaust gas temperature T is read again, and the exhaust gas temperature T is set as the preset allowable temperature T (T < ALW ALW TMAX ) (steps 7, 8. 9.10)
.

When the exhaust gas temperature T becomes lower than the allowable ALW, the control ends (step 5).

In the above embodiment, it is possible to switch between the automatic regeneration mode and the manual regeneration mode so that regeneration can be performed both when the construction machine is in actual operation and when it is stopped, but in the present invention, only the automatic regeneration mode is used. Good too. Furthermore, in the above embodiment, the opening and closing of the butterfly valve is controlled by signals from both the pressure sensor and the temperature sensor of the trap device, but in the present invention, the butterfly valve may be controlled by only the signal from the pressure sensor. .

[Effects] As described above, according to the present invention, black smoke particles can be controllably combusted by exhaust gas without the need for a special heating device, and the ceramic trap assembly can be used as a trap while being installed in construction machinery. A method for reducing smoke in a diesel engine is provided that has excellent serviceability and durability because the device can be regenerated.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an example of a device used in the method of the present invention, Fig. 2 is a longitudinal sectional view of a ceramic trap used in the device, Fig. 3 is an end view of the ceramic trap, and Fig. 4 5 is a longitudinal sectional view of the ceramic trap assembly, FIG. 5 is an enlarged partial cross-sectional view of the trap device used in the device, FIG. 6 is a flowchart showing the content of regeneration control in the above embodiment device, and FIG. The figure is a flowchart showing the details of temperature control of the device of the same embodiment, and FIG. 8 is a graph showing the relationship between engine speed and operating pressure range. 1... Engine 5... Butterfly valve 7... Actuator 13... Trap device 1
5... Ceramic trap assembly = 17- 17... Pressure sensor 19... Temperature sensor 2
1... Rotation sensor 23... Controller 2
5...Mode changeover switch 29...Indicator 31...Ceramic trap 33...Internal passage 37...Porous thin wall 3
9...Buffer material 41...Outer tube 43...Inlet side manifold part 45...Outlet side manifold part 57...Flange 59...Casing 61, 63...Flange 65...・Plate patent applicant: New Caterpillar - Mitsubishi Corporation = 18
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Claims (5)

[Claims] (1) A trap device for collecting black smoke particles is installed in the exhaust system of the engine, including a ceramic trap assembly with a honeycomb structure in which a catalyst for lowering the combustion temperature of black smoke is supported on the internal passage wall; A pressure sensor is provided at the inlet of the device; the specified exhaust pressure range of the trap device is determined from the speed signal from the engine rotation sensor, the specified exhaust pressure range is compared with the exhaust pressure from the pressure sensor, and the specified exhaust pressure range of the trap device is determined. When the exhaust pressure inside the trap device exceeds the specified upper limit of the specified exhaust pressure range, the butterfly valve is throttled, and when the exhaust pressure falls below the specified lower limit, the butterfly valve is fully opened to remove black smoke particles inside the trap device. A method for reducing smoke in a diesel engine, characterized by controlling the combustion speed of the engine. (2) The opening/closing control of the butterfly valve can be switched between an automatic regeneration mode and a manual regeneration mode, and in the automatic regeneration mode, the throttle of the butterfly valve is set to a light throttle;
2. The smoke reduction method according to claim 1, wherein in the manual regeneration mode, the throttle of the butterfly valve is set to excessive throttle. (3) providing a temperature sensor at the inlet of the trap device;
A patent claim characterized in that the temperature from the temperature sensor and a preset upper limit temperature are compared at predetermined time intervals, and when the temperature inside the trap device exceeds the upper limit temperature, the butterfly valve is fully opened. The smoke reduction method according to item 1 or 2. (4) The temperature signal from the temperature sensor is compared with a preset allowable temperature, and the butterfly valve is kept fully open until the temperature inside the trap device falls below the allowable temperature. Smoke reduction method described in section. (5) The smoke reduction method according to claim 1, wherein a palladium-based or base metal-based catalyst is used as the catalyst.