JPH0428885B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an operation control device for an exhaust particulate processing device that collects and removes particulates contained in the exhaust gas of an internal combustion engine such as a diesel engine.

For example, as an example of an exhaust particulate treatment device for a diesel engine, one disclosed in Japanese Patent Application Laid-open No. 12029/1983 is known. According to this, the exhaust system of an engine includes a trap that collects particulates in the exhaust gas, a trap regeneration device that heats and incinerates the particulates collected in the trap, and an exhaust pressure sensor that detects the exhaust pressure upstream of the trap. , and the trap regeneration device is operated based on a comparison between a limit exhaust pressure indicating trap clogging determined based on engine operating conditions such as engine rotational speed and load, and exhaust pressure detected by the exhaust pressure sensor. It is equipped with an operation timing control means for controlling the operation timing of the.

FIG. 1 shows an example of the operation of such an operation timing control means. A clogging state is detected, and if clogging is detected, it is determined whether the engine speed and load are in a region suitable for igniting a trap regeneration device, for example, a burner disposed upstream of the trap. do. If the burner is in the ignition range, the fuel pump, injection valve, ignition device, etc. are activated to ignite the burner and regenerate the trap. Here, whether or not the burner has been successfully ignited is detected by the temperature difference between the upstream and downstream sides of the burner, and if the burner has misfired, the fuel supply and ignition to the burner are stopped and the burner is restarted. Re-determine whether the engine is operating in the ignition range. When successful burner ignition is detected, it is detected that the burner has operated for a certain period of time required for trap regeneration, and after that, the fuel pump, injection valve,
Turn off the ignition device and extinguish the burner.

However, in the case of such conventional exhaust particulate processing devices, the exhaust pressure signal detected from the exhaust pressure sensor is compared with a predetermined limit exhaust pressure corresponding to the engine speed and load. The system was configured so that when a clogged trap was detected and the exhaust pressure reached the critical level required for trap regeneration, the trap regeneration device started operating. In the case of differences and engine operating conditions, for example, immediately after engine startup or in an over-operating position, the exhaust gas temperature will differ even if the engine speed and load are the same, and therefore the exhaust volume will vary depending on the exhaust temperature. Since the exhaust pressure required for trap regeneration is different, the exhaust pressure required for trap regeneration at that time will also change. Therefore, control cannot be accurate if the exhaust pressure required for trap regeneration is determined solely based on the engine speed and load. Therefore, the above conventional configuration According to the authors, there was a problem in that it was not possible to accurately detect the clogged state of the trap, that is, the exhaust pressure necessary for trap regeneration.

The present invention was made in view of the inconveniences of the conventional exhaust particulate processing device, and in addition to a means for controlling the operation timing of the trap regeneration device based on the detection signal of the exhaust pressure sensor, a temperature sensor is provided in the exhaust system. The operation of the exhaust particulate treatment device is provided with a correction means for correcting the operation timing of the trap regeneration device based on the exhaust gas temperature detected by the exhaust gas temperature, so as to accurately detect the critical clogging state necessary for trap regeneration. A control device is provided.

Embodiments of the present invention will be described below based on the drawings.

In the embodiment shown in FIG. 2, a trap 2 for collecting particulates in the exhaust gas is interposed in an exhaust passage 1 of a diesel engine, and a trap regenerating device 3 is disposed upstream of the trap 2. The trap regenerator 3 consists of burner means, which pumps fuel from a fuel tank (not shown) with a fuel pump 4, meters the fuel with a fuel control valve 5, and atomizes the fuel to form a mixture with air and send it to the burner section. Supply to 6.
The fuel mixture supplied from the burner section 6 is ignited by the ignition device 7, heating the circulating exhaust gas and incinerating the particulates adhering to the trap 2. The operations of the fuel pump 4, fuel control valve 5, and ignition device 7 are controlled by an output signal from an operation timing control means 10.

The operation timing control means 10 receives engine operating state signals such as an engine rotational speed N signal and an engine load Q signal from an engine operating state detection device (not shown). Further, the exhaust pressure from the exhaust pressure sensor 11 that detects the exhaust pressure upstream of the trap is inputted, and an increase in exhaust pressure due to the trap 2 being clogged is sensed. The operation timing control means 10 stores in advance a limit exhaust pressure Pt corresponding to clogging of the trap 2 according to these engine operating conditions, and sets the tested exhaust pressure Pr to a level higher than the limit exhaust pressure Pt.
When the trap regeneration device 3 increases, the fuel pump 4, fuel control valve 5, and ignition device 7 of the trap regeneration device 3 are operated for a predetermined period of time to regenerate the trap. Here, for example, when the engine is operated at high speed and high load, the oxygen concentration in the exhaust gas decreases and the exhaust flow velocity increases, making it difficult to ignite the burner in the trap regenerator 3, causing fuel loss due to misfire. There is a risk that dripping will occur and worsen the exhaust gas. Therefore, in the operation timing control means 10,
Based on the engine rotational speed N signal and the engine load Q signal, it is determined whether the engine operating state is suitable for burner ignition.

To determine whether the burner section 6 of the trap regenerator 3 has ignited, the temperature detected by the temperature sensors 12 and 13 disposed on the upstream and downstream sides of the burner section 6 is input to the operation timing control means 10, and A temperature sensor 14 disposed downstream of the trap detects an abnormal temperature rise in the trap when the temperature difference is greater than a predetermined value, and inputs this to the activation timing control means 10 to warn of the abnormal temperature rise in the trap. Or, stop the operation of the trap regenerator 3 and restart the trap 2.
prevent burnout of the exhaust system, including

The above configuration is similar to a conventional exhaust particulate processing device. In such a configuration, even when the engine speed and engine load are equal, the exhaust volume varies depending on the exhaust temperature, and as a result, even if the clogged state of trap 2 is the same, the detected exhaust pressure upstream of trap 2 will vary. Therefore, the detected exhaust pressure Pr cannot necessarily be accurately compared with the limit exhaust pressure Pt indicating that the trap 2 is clogged. Therefore, in the present invention, the exhaust pressure is detected based on the detected temperature signal of the temperature sensor 12 upstream of the burner section.
Pr or the limit exhaust pressure Pt is corrected.

This is shown in FIG. The operation timing control means 10 includes an engine rotation speed sensor 18 and an engine load sensor 1.
A memory M is provided in which a predetermined limit exhaust pressure at the time of trap clogging is stored in accordance with the signals N and Q detected by the trap. Komo Memory M
is provided for each subdivision of exhaust temperature. A correction circuit 30 is provided which selects these memories M ₁ to _{M o} according to the detected exhaust gas temperature T and the corresponding sub-region (T _{o -1} < T < T _o ) by the selector 21 . The engine rotation speed signal is obtained by counting the digital value output from the crank sensor etc. using the counter 22, and the value is input into the memory.The load signal is obtained by counting the analog value such as the opening degree of the control lever of the fuel injection pump. The D converter 23 converts it into a digital value and inputs it into the memory, and the exhaust temperature is a detected analog value which is amplified by the amplifier 24 and then converted into a digital value by the A-D converter 23. After conversion, it is input to the selector 21.

Note that the limit exhaust pressures stored in the memories M ₁ to _{M o} may be determined in advance as a map according to the engine rotation speed signal and the load signal, or the limit exhaust pressure can be determined according to the engine rotation speed signal and the load signal. It goes without saying that it is also possible to use a function generator that stores the approximation formula to be determined and calculate it each time. At this time, the approximate formula differs depending on the heat capacity of the exhaust system and the type of trap in the burner section, so it is best to find these through experiments.

Next, the operation will be explained using the flowchart shown in FIG.

An engine operating state detection device consisting of an engine rotation speed sensor 18 and a load sensor 19 detects an engine rotation speed N and an engine load Q, and inputs them into memories M ₁ to _{M 2} as a rotation speed signal and a load signal, respectively;
Find the limit exhaust pressure Pt corresponding to the engine operating condition. On the other hand, the exhaust temperature upstream of the burner section 6 output from the temperature sensor 12 is transmitted to the amplifier 24 and the A-D converter 2.
3 to the selector 21, and it is determined in which sub-region (T _o-1 < T < T _o ) the detected temperature T is located, and the limit exhaust pressure Pt is determined according to the exhaust temperature at that time. Select the memory where is stored. Then, the exhaust pressure detected by the exhaust pressure sensor 11 and the limit exhaust pressure Pt stored in the selected memory
When the detected exhaust pressure Pr becomes equal to or higher than the limit exhaust pressure Pt, the operation timing control means 10 operates the trap regeneration device 3 in the conventional operation order to heat the particulates collected in the trap 2. Incinerate and regenerate.
The regeneration period may be a predetermined period, or may continue until the exhaust pressure detected by the exhaust pressure sensor 11 falls below a predetermined value.

In the above embodiment, the limit exhaust pressure is corrected based on the exhaust temperature, but instead of correcting the limit exhaust pressure, the detected exhaust pressure may be corrected using the exhaust temperature and compared with the limit exhaust. be.

As explained above, according to the present invention, when the exhaust pressure sensor detects the clogging of the trap, the detected exhaust pressure or the limit exhaust pressure stored in advance is corrected according to the temperature of the exhaust gas, so that the exhaust pressure is It is possible to accurately know when the limit of clogging has been reached.
This will allow the exhaust particulate treatment device to operate with high precision, improve fuel consumption, and efficiently collect and incinerate particulates in the exhaust, or prevent exhaust pressure from rising due to the regeneration timing being too late. It is possible to prevent a decrease in output due to overheating and also prevent overheating and burnout of the trap.

[Brief explanation of drawings]

FIG. 1 is a flowchart explaining a conventional exhaust particulate treatment device, FIG. 2 is a schematic system diagram showing the exhaust particulate treatment device of the present invention, and FIG. 3 is a schematic diagram of an operation timing detection means showing the main part of the present invention. Block diagram, 4th
The figure is the same flowchart as above. DESCRIPTION OF SYMBOLS 1... Exhaust passage, 2... Trap, 3... Trap regeneration device, 10... Operation timing control means, 11
... Exhaust pressure sensor, 12 ... Temperature sensor, M ₁ ~ _{M o}
...Memory, 21...Selector, 30...Correction means.

Claims (1)

[Claims] 1. The exhaust system of an internal combustion engine includes a trap that collects particulates in the exhaust, a trap regenerator that heats and cools the particulates collected in the trap, and detects exhaust pressure in response to the exhaust pressure upstream of the trap. an exhaust pressure sensor is provided, and the detected exhaust pressure is compared with a limit exhaust pressure set according to the engine rotation speed detected by the engine rotation speed sensor and the engine load detected by the engine load sensor. In the exhaust particulate treatment device, the exhaust particulate treatment device includes an operation timing control means for controlling the operation timing of the trap regeneration device based on the trap regeneration device, and a temperature sensor is provided upstream of the trap regeneration device, and the exhaust temperature detected by the temperature sensor is 1. An operation control device for an exhaust particulate treatment device, characterized in that a correction means is provided for correcting the operating timing of the trap regeneration device by correcting the limit exhaust pressure or the detected exhaust pressure based on the threshold exhaust pressure or the detected exhaust pressure.