JPH044441B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an exhaust gas purification device for a diesel engine, and more particularly to an exhaust gas purification device that efficiently regenerates a trap that collects particulates in exhaust gas.

[Prior art]

For example, as disclosed in Japanese Utility Model Application Publication No. 57-126515, black smoke particles contained in the exhaust gas of a diesel engine are collected by a trap using a platinum catalyst or the like to prevent air pollution. However, since the volume of the top is finite, the ventilation resistance of the trap increases as the number of particles collected increases.
Exhaust pressure increases. For example, in a certain test engine, the rotation speed v = 1000 rpm, the load torque L = 100 ft-
When operating conditions of 1 bs are given, the increase in exhaust pressure with respect to steady running time τ, that is, the pressure loss ΔP, is as shown in Fig. 1. Since this increase in exhaust pressure adversely affects driveability, consumption, and exhaust gas components, it is necessary to regenerate the trap by some method, that is, remove the trapped particulates. The conventional method for this regeneration was to apply heat to the trap using a pressure injection burner and burn the particulates.
It is difficult to change the fuel injection amount of this burner, and control is performed to determine whether or not to provide a constant amount of heat unique to the burner. However, the temperature and exhaust pressure of the trap vary significantly depending on the operating condition of the engine, and it is necessary to supply the amount of heat necessary to oxidize particulates depending on the condition of the trap. It was impossible to control. Therefore, depending on the condition of the trap, problems such as the trap being destroyed or having an adverse effect on the exhaust cannot be avoided.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an exhaust gas purification device for a diesel engine, which eliminates the drawbacks of the prior art described above and is capable of supplying heat for trap regeneration in accordance with the engine and trap conditions. .

[Summary of the invention]

The present invention uses a duty burner whose combustion can be controlled on and off as a burner for oxidizing particulates, and when the actually detected exhaust pressure of the engine exceeds a set pressure determined from the operating state of the engine, The present invention is characterized by the provision of means for controlling the combustion of the duty burner on and off so as to supply an amount of heat according to the temperature of the trap.

[Embodiments of the invention]

Hereinafter, the present invention will be explained with reference to the drawings. FIG. 2 is an overall configuration diagram showing one embodiment of the present invention, in which a ceramic filter coated with a platinum catalyst having a three-dimensional network skeleton structure is provided as a trap 2 in the exhaust pipe 1 of a diesel engine, and the exhaust pipe shaft A casing 3 is formed in a direction perpendicular thereto. The space formed by the casing 3 is partitioned by a partition member 4 having air holes, and the partition member 4 forms a combustion chamber 5 and an air chamber 12. Air sent from the fan 11 to the air chamber 12 is blown out from the air hole of the member 4 into the combustion chamber 5. A swirler 8 for swirling primary air is provided at the bottom of the combustion chamber 5, and a duty burner 6, which is a feature of the present invention, is provided below the swirler 8. A fuel pump (not shown) that supplies fuel to the duty burner 6 and the duty burner 6 are communicated through a pipe 7, so that fuel is constantly circulated. When the combustion timing and combustion time of the duty burner 6 are determined by the control unit 14 according to the control method used in the present invention to be described later, the duty signals 50 to 50 are determined in accordance with the combustion timing and combustion time of the duty burner 6.
52 is transmitted to the duty burner 6. Of these, the signal 50 controls the ignition device 10, and the signal 51 generates a periodic magnetic field in the nozzle of the duty burner 6, which opens and closes the ball valve and injects fuel. Further, the signal 52 controls the air blowing of the fan. The high-temperature gas obtained by combustion under such control passes through the trap 2 and oxidizes the collected particles, but the flame sensor 15 provides information as to whether combustion is occurring or not. In the event of a misfire, fuel is cut.

Next, a control system for burner combustion in this embodiment will be explained. The central part of this control system is the control unit 14, which can be easily realized by, for example, a microcomputer, and a flowchart of its processing is shown in FIG.
In the figure, this process consists of two processes in parallel: determination of the set pressure in steps 120 to 122 and combustion control according to the result, but this may be performed using separate hardware. Alternatively, the problem may be handled by time-synchronized division processing using one microcomputer. First, the control unit 14 takes in the engine speed v and the load L in step 120, and
In step 121, the exhaust pressure P ₀ (pressure at the trap 2 inlet) corresponding to this value is calculated. This exhaust pressure P ₀ was determined experimentally in the absence of a trap.
The characteristics are as shown in Figure 4. Therefore, if this characteristic is converted into, for example, an approximate expression and stored in the control unit, the processing in step 121 can be performed. Subsequently, in step 122, the exhaust pressure increase ΔP ₀ allowed by the trap 2 is added to the exhaust pressure P ₀ to set the set pressure P _s . On the other hand, for combustion control, first clear the necessary internal parts in step 100, and then proceed to step 101.
Turn off the duty signals 50 to 52 with
At step 102, the actual exhaust pressure P from the pressure sensor 13 is taken in, and the previously set set pressure _Ps and P are stepped.
Compare at step 104 and repeat from step 101 since P<P _s . However, when P>P _s , it means that the pressure increase due to the trap exceeds the allowable value ΔP ₀ , so the combustion control proceeds from step 105 onward. That is, in step 105, the trap temperature T is detected from the temperature sensor 16.
is taken in, and the amount of heat supplied from the burner 6 is determined in step 106. To make this determination, the characteristics of the top shown in Figures 5 and 6 are applied to control unit 1.
4 and use it. This characteristic shows that when a certain trap temperature T is determined, if that temperature T is maintained for the regeneration time TR determined by the vertical axis in FIG. 6, the exhaust pressure will rise as shown in FIG. It shows. In other words, Fig. 5 shows that when the temperature T is increased, the fine particles collected in the trap are oxidized and ΔP decreases.
FIG. 6 shows the time required for the oxidation. Therefore, from the characteristics shown in Figure 5, the trap temperature _T1 to make the pressure loss ΔP ₀ changes, so from the difference ΔT between this and the captured trap temperature T, calculate the amount of heat Q that must be supplied to the trap. At the same time, the regeneration time TR for supplying the amount of heat Q can be determined from the characteristics shown in FIG. Next, in step 107,
The pulse width h and its period H in the duty signal 51 as shown in FIG. 7 are determined. This means that if the fuel flow rate taken in per unit time when the nozzle of the duty burner 6 is opened and the calorific value of the fuel are given, the duty h/H of the duty signal 51 can be calculated from the supplied heat quantity Q determined in step 106. It can be determined by what is required. At the same time, this duty signal 51
Accordingly, a duty signal 50 for ignition and a duty signal 52 for driving the fan are also determined. Next, in steps 108 and 109, duty signals 50 to 52 are output to perform ignition, fuel supply, and air supply, and the seventh
Combustion in burner 6 is turned on and off according to signal 51 in the figure. Next, in step 110, it is checked whether the burner 6 is actually burning. This is done by checking the output F of the flame sensor 15. If there is a misfire, the process returns to step 108, and if ignition is confirmed, then in step 111, it is checked whether the previously determined regeneration time TR has elapsed. This may be done using a timer mechanism within the controller 14. If the TR time has not elapsed, the process returns to step 109 and continues combustion. If it has been completed, in step 112 the exhaust pressure P at that point is sent to the pressure sensor 1.
3 and compares it with the previously determined set pressure _Ps in step 114. In other words, it is checked whether the exhaust gas has actually become below _Ps due to burner combustion. If this fails, the combustion control from step 105 onwards is repeated, and the trap is regenerated reliably through control according to the engine and trap conditions.

〔Effect of the invention〕

As is clear from the above embodiments, according to the present invention, the combustion amount of the burner can be controlled at an appropriate timing according to the operating state of the engine and the state of the trap, thereby preventing damage to the trap and unnecessary combustion of the burner. It has the effect of preventing

[Brief explanation of drawings]

Fig. 1 is a diagram showing the relationship between running time and trap pressure loss by a test vehicle, Fig. 2 is an overall configuration diagram showing an embodiment of the present invention, and Fig. 3 is an example of burner control processing that is a feature of the present invention. A flowchart showing
Fig. 4 is a constant exhaust pressure diagram with respect to engine speed and load; Figs. 5 and 6 are diagrams showing the relationship between trap temperature and trap pressure loss and the relationship between trap temperature and trap regeneration time according to test traps;
FIG. 7 is an explanatory diagram of the duty signal. 2... Trap, 5... Combustion chamber, 6... Duty burner, 7... Fuel pipe, 10... Ignition device, 11... Fan, 13... Pressure sensor, 14
...Control unit, 15...Frame sensor, 16...Temperature sensor.

Claims (1)

[Claims] 1. A trap that collects particulates contained in the exhaust gas of a diesel engine, and the amount of heat generated by the trap for oxidizing and removing the particulates collected in the trap can be controlled from the outside. The control means includes a burner and a control means for controlling the amount of heat generated by the burner, and the control means includes an allowable exhaust pressure for setting an allowable engine exhaust pressure corresponding to the rotational speed and load of the diesel engine. Setting function and
When the detected exhaust pressure of the diesel engine exceeds the allowable exhaust pressure, the amount of heat and heating time required for the oxidation are determined from the actual measured value of the temperature of the trap, and the determined amount of heat is used for the heating determined above. 1. A diesel engine exhaust purification device, characterized in that it has a function of controlling the combustion of the burner so that the burner is supplied to the trap for only a certain amount of time. 2. The burner has a structure in which its combustion can be turned on and off by an external control signal, so that its calorific value can be controlled, and the control means is configured to control the amount of heat corresponding to the amount of heat necessary for the oxidation. 2. The diesel engine exhaust purification device according to claim 1, wherein the burner is controlled by a pulse-like control signal having an on-off ratio.