JPS61237811A - Soot reburner - Google Patents

Abstract

PURPOSE:To efficiently perform reburning of soot contents in exhaust gas by mounting both an exhaust heat controller which increases exhaust heat when an engine runs within a low and middle load range and a heater controller which heats the soot contents in exhaust gas if exhaust heat cannot be increased sufficiently. CONSTITUTION:A throttle valve 4 and an EGR valve 5 which are incorporated in the intake system of a Diesel engine 1 are opened and closed under the control of a vacuum control valve 6. Said valve 6 are suitably controlled by a controller 9 on the basis of the signals from an air flow sensor 3, an engine load sensor 7 and an engine revolution sensor 8. A catalyst-containing tap 11 including a supplementarily reburning electric heater 10 in the upper stream side thereof, is incorporated in the exhaust system of said engine 1. Said heater 10 is most suitably controlled by the controller 9 on the basis of the signals from said sensors 7 and 8 and an exhaust temperature sensor 12.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a soot reburning device that reburns particulates (soot) contained in the exhaust of a diesel engine.
In particular, the present invention relates to a device that reduces the power consumption required by the electric heater by controlling the heating by the electric heater after raising the exhaust gas temperature to a possible range.

[Prior Art] Conventionally, a trap with a catalyst that can re-combust soot at a relatively low temperature has been employed as a soot trap for a diesel engine.

Therefore, if the engine exhaust heat is high to a certain extent, the catalyst can re-combust the soot using only that exhaust heat, and even if the exhaust heat is low, if the catalyst performance is sufficient, the soot can self-combust.

[Problems to be solved by the invention] However, as the catalyst performance is still insufficient at present, in the case of general road driving where engine exhaust heat is not obtained to a large extent, it is difficult to use catalysts alone. There was a problem in that the trap was not clogged due to insufficient combustion.

Therefore, it has been considered to heat the catalyst with an electric heater to help activate the catalyst and enable re-combustion even during general road driving, but this requires a large amount of electricity to enable re-combustion. This not only resulted in a deterioration in fuel efficiency due to an increase in engine load, but also forced the installation of large-capacity batteries and generators.

In addition, as a related technology, Japanese Patent Application Laid-Open No. 5 (1973) proposed an attempt to recirculate a large amount of EGR gas to lower the exhaust temperature and suppress the temperature rise of the trap during reburning, thereby preventing the trap from melting.
9-101519J% Publication), by reducing the amount of EGR gas and suppressing the increase in the amount of GR gas due to the increase in exhaust pressure during re-combustion, preventing an increase in HC etc. and deterioration of combustibility. (Japanese Unexamined Patent Publication No. 59-37225).

[Objective of the Invention] The object of the present invention is to solve the above-mentioned problems and suppress deterioration of combustibility and exhaust gases to within permissible limits even when operating under medium and low load ranges where exhaust heat does not increase significantly. An object of the present invention is to obtain a soot reburning device for a diesel engine which enables soot to be reburned by raising the exhaust gas temperature and heating the electric heater with minimum electric power.

[Summary of the Invention] The configuration of the present invention in accordance with the above-mentioned object is to reduce exhaust heat by throttling the throttle valve and EGR valve in the middle and low engine load range where the temperature is insufficient to re-combust soot under the catalyst. In addition to installing an exhaust heat controller that increases the exhaust heat as much as possible, when the increased exhaust heat still leaves insufficient humidity and re-combustion is insufficient, the heater is energized within the capacity of the electric heater and the heat is captured in a catalytic trap. It is characterized by being equipped with a heater controller that heats the soot in the exhaust gas.

This two-stage control allows soot to be re-combusted without consuming a large amount of electricity, thereby avoiding deterioration of fuel efficiency due to increased engine load or the need to install a large-capacity battery or generator.6 This is how it was done.

[Example] An example of the present invention will be described in detail based on FIGS. 1 to 6.

FIG. 1 is a configuration diagram showing an embodiment of the device of the present invention, in which 1 is a diesel engine, and its intake system includes an air cleaner 2, an air flow sensor 3, a throttle valve 4, and an EGR valve 5 in order toward the engine. has been done. The throttle valve 4 and the EGR valve 5 are controlled to open and close by a vacuum control valve 6 in parallel with a normal control system (not shown). This vacuum control valve 6 is operated by a TLL device 9 that receives the intake air amount, engine load (torque), and engine rotation speed detected by the air flow sensor Fj 3, engine load sensor 7, and engine rotation sensor 8, respectively. Optimal control. The part that performs this control constitutes an exhaust heat controller.

It is appropriate that the engine load sensor 7 be, for example, a potentiometer that detects the voltage of the lever opening of the fuel injection pump corresponding to the engine torque, and that the engine rotation sensor 8 be, for example, a tachometer that detects the rotational speed of the fuel injection pump.

On the other hand, in the exhaust system of the diesel engine 1, a trap 11 with a catalyst is installed, in which a relatively small-capacity electric heater 10 for assisting re-combustion is attached on the -F flow side.

The electric heater 10 receives the engine load (detected by the previously described engine load sensor 7, engine rotation sensor 8, and exhaust temperature sensor 12 installed near the electric heater).
The controller 9 receives the information such as torque), engine speed, and trap inlet temperature, and performs optimal control based on the judgment. This M
The part that performs tll constitutes a heater controller.

Here, the function of the exhaust heat controller that controls the vacuum control valve 6, that is, the throttle valve 4 and the EGR valve 5, will be explained along the flowchart shown in FIG.

Before explaining this, I will first clarify the purpose of this flowchart. That is, the curve group and three regions A to C shown in FIG. 2 represent the engine load characteristics (
The figure shows the relationship between the trap inlet temperature distribution and the electric heater operating range under load characteristics (hereinafter simply referred to as load characteristics).

Region A is a region where the catalyst can re-burn soot using only engine exhaust heat, and there is no need to turn on the electric heater 10.

Region B is a region where exhaust heat is insufficient and re-combustion by the catalyst is insufficient, and by controlling the electric heater 10 of capacity H attached to the trap 11, the trap inlet temperature is reduced to the lower limit setting value of the region, e.g. This is a region where the temperature can be raised up to 400°C. Region C is a lack of exhaust heat,
Alternatively, the amount of engine exhaust gas is so large that the electric heater cannot raise the temperature to a temperature that allows re-combustion, and this is the FF area of the electric heater.

Therefore, if the engine exhaust temperature can be raised as much as possible to bring it to the low range when the engine load is in the medium or low load range or in the 0M range, then the engine exhaust temperature can be raised again without the need for assistance from the electric heater 10. combustion becomes possible. For this reason, the standard voltage characteristic line ■=αN+β shown in FIG. 3 or 4 is
The torque curve was adjusted to indicate 0°C.

In Fig. 3, the exhaust heat controller first reads the engine speed and engine torque, that is, the potentiometer voltage from each sensor 7.8, and the coordinate points determined from these values are placed on the load characteristic diagram in Fig. 4. It is determined whether the voltage is above or below the standard voltage characteristic line IaV-αN+β. If the coordinate point is on a straight line, the exhaust gas temperature is sufficiently high, so throttle control of the throttle valve 4 and EGR valve 5 is not performed, and these controls are left to the normal control system.

If the coordinate point is below the straight line, it is determined that the exhaust gas temperature is low and the process proceeds to the next step. That is, the intake air amount is measured by the air flow sensor 3, and throttling control of the throttle valve 4 and EGR valve 5 is performed in addition to the control of the normal control system until this measured value reaches a set value. Here, the set value of the intake air amount is set to an air-fuel ratio that is higher than the air-fuel ratio that is normally set to optimize combustibility and exhaust performance within the limit of detonation occurrence and the allowable limit of exhaust deterioration. is determined to be smaller.

When the throttle valve 4 is throttled, the amount of intake air decreases and the amount of fuel injection increases relatively, causing the engine temperature to rise and the exhaust temperature to rise.

Furthermore, when the EGR valve 5 is throttled, the amount of recirculated exhaust gas is reduced, and deterioration of the exhaust gas can be prevented. Therefore, when the throttle valve 4 and the EGR valve 5 are simultaneously subjected to throttle IQ control, the exhaust gas temperature can be raised to an upper limit while avoiding deterioration of the exhaust gas.

Next, the functions of the heater controller that controls the electric heater 10 will be explained with reference to the flowchart shown in FIG. In addition,
The heater operating region characteristics shown in FIG. 2 mentioned above are stored in the storage section of the heater controller.

As shown in the figure, the heater controller, like the exhaust heat controller,
First, read the engine speed and potentiometer voltage. Then, it is determined whether the coordinate point obtained by reading is located in any of the three areas A, B, and C shown on the relationship characteristic diagram in Figure 6, which is a simplified and updated version of Figure 2. do. Proceed to the next step only when the coordinate point is in area B, that is, in an area where heater control is possible. In other words, the electric heater 1 is turned on until the trap inlet temperature in the engine speed/engine torque characteristics reaches the set value (lower limit set value in the range).
0 is energized. The energization control a'a of the heater is most easily controlled by 0N10FF control in which the current value is constant as shown in the illustrated example, but it is also possible to use current control in which the current value is changed depending on the location of the coordinate point.

Note that the controller also reads the amount of intake air and uses this as a condition for stopping heater heating, which will be described later.

Now, in the above configuration, when partial load operation is performed where the exhaust gas temperature is insufficient, the exhaust temperature control shown in FIG. When the exhaust heat controller determines that exhaust heat is insufficient, it throttles the throttle valve 4 to reduce the amount of intake air, and throttles the EGR valve 5 to reduce the amount of exhaust gas returned to the intake system. This control is performed accurately by feedback control until the amount of intake air detected by the air flow sensor 3 reaches a set value.

Since the amount of intake air decreases until it reaches the set value, the exhaust temperature will rise much more than when the engine was operating at the optimum air-fuel ratio. Also, at this time, E, G
Since the R valve 5 is also throttled, deterioration of exhaust emissions can be minimized. Therefore, even under a low load or medium load region, the exhaust gas temperature is increased as much as possible while minimizing deterioration of exhaust emissions. In this way, the exhaust temperature is optimally increased to support catalyst activity while detecting engine rotation, engine torque, and intake air amount.

After the exhaust gas temperature is sufficiently raised by throttling control of the throttle valve 4 and the EGR valve 5, the heater control shown in FIG. 5 is subsequently performed to raise the exhaust temperature to the soot reburning temperature. That is,
When the heater controller determines that the trap inlet temperature is in region B, it energizes the electric heater 10 and continues to energize it until the trap inlet temperature reaches the lower limit of region A.

Therefore, heating with the electric heater ensures the minimum temperature at which soot can be re-burned. In this way, the exhaust temperature is optimally increased by the heater for reburning assistance while detecting the trap inlet temperature.

As a result, soot that cannot be reburned in the catalyst trap 11 due to insufficient exhaust gas temperature due to general road running is not generated, and the soot can be reburned reliably. In this case, since the exhaust temperature is raised in advance and then the electric heater is used to raise the temperature, the heat capacity is smaller than when heating is performed directly with the heater, and power consumption can also be significantly reduced. .

On the other hand, even if the exhaust temperature is controlled by EGR and intake throttling in a partial load where the air temperature is insufficient,
If the wrap inlet temperature does not reach the 8th region and is still in the C region, and the intake air amount is above the predetermined value, the electric heater 1o attached to the trap 11 will not be able to heat it completely. As shown in the flowchart of the figure, no heater heating is performed. In this way, the heater is energized only when the operating conditions are achievable within the range of the heater capacity, thereby eliminating wasted power and minimizing power consumption.

[Effects of the Invention] In summary, the present invention exhibits the following excellent effects.

(1) Even if there is soot that cannot be re-burned in the catalyst trap due to insufficient exhaust heat due to operation under a medium-low load range where the exhaust heat is not significantly high, the exhaust temperature can be raised by the intake air control and the heater Since the exhaust heat is raised to a temperature at which re-combustion is possible in combination with the increase in the 1-lap inlet temperature through heating control, soot can be re-combusted with minimum electric power.

As a result, the device can be made more compact without requiring a large-capacity battery or generator.

(2) In addition to the intake air amount control that is performed to raise the exhaust temperature, the EGR valve throttle control is also performed.
It is possible to avoid a rise in exhaust temperature while suppressing deterioration in combustibility and exhaust gases to within permissible limits, and it is possible to minimize a decrease in engine output and deterioration in exhaust emissions.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the soot reburning device according to the present invention, Fig. 2 is an explanatory diagram showing the relationship between trap inlet temperature distribution and electric heater operating area under engine torque characteristics, and Fig. 3 is a diagram showing the relationship between trap inlet temperature distribution and electric heater operating range under engine torque characteristics. A flowchart explaining the function of the exhaust heat controller that constitutes the controller of the soot reburning device shown in Fig. 1, the fourth factor is a torque characteristic diagram to facilitate understanding of the flowchart shown in Fig. 3, and Fig. 5 is a flowchart explaining the function of the heater controller that constitutes the controller of the soot reburning device shown in Fig. 1, and Fig. 6 is a simplified version of Fig. 2 to facilitate understanding of the flowchart shown in Fig. 5. FIG. In the figure, 1 is a diesel engine, 4 is a throttle valve, and 5 is a diesel engine.
1 is an EGR valve, 7 is an engine load sensor, 8 is an engine rotation sensor, 9 is a controller consisting of an exhaust heat controller and a heater controller, 10 is an electric heater, and 11 is a trap with catalyst. Patent Applicant: Isuq Motor Co., Ltd. Representative Patent Attorney Nobuo Kinutani Figure 5

Claims (4)

[Claims] (1) An electric heater that heats soot in the exhaust captured by a trap with a catalyst, an exhaust heat controller that increases exhaust heat by throttling the throttle valve and EGR valve when the engine load is in the medium to low load range, and A soot reburning device comprising a heater controller that energizes a heater when heat is insufficient for reburning by a catalyst. (2) The exhaust heat controller is equipped with an engine load sensor, an engine rotation sensor, and an air flow sensor, and determines that the engine load is in a medium-low load range from the engine torque and engine rotation speed, and detects it with the air flow sensor. The throttle valve and EGR are adjusted so that the amount of intake air reaches the predetermined value.
The soot reburning device according to claim 1, characterized in that the soot reburning device is configured to throttle the valve. (3) The heater controller determines and stores a heater operating region in which re-combustion by the catalyst is insufficient but re-combustion by the catalyst is possible by energization heating of the electric heater from the exhaust temperature distribution corresponding to the load region. It is equipped with a storage unit, an engine load sensor, an engine rotation sensor, and an exhaust temperature sensor, and determines from the engine torque and engine rotation speed that the load region is in the heater operation region, and detects the exhaust heat detected by the exhaust temperature sensor. 2. A soot reburning device according to claim 1 or 2, characterized in that the electric heater is energized so that the temperature reaches a predetermined value. (4) Claims 1 to 3, characterized in that the heater controller has a function of stopping energization of the electric heater when a heating amount exceeding the heater capacity is required.
The soot reburning device according to any one of paragraphs.