JPH0232807Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to a trap device for collecting and removing particulate matter (particulate matter) in the exhaust gas of a diesel engine, and more particularly to prevention of erosion of such a trap device.

Prior Art A trap device is installed in the exhaust pipe of a diesel engine to collect and remove particulates in the exhaust gas. A trap material is provided in the trap device,
Collects particulates in exhaust gas. After traveling for a predetermined time or distance, a heater provided close to the trap material is driven to incinerate the particulates collected by the trap material.

A diesel engine equipped with such a particulate trap device has a problem in that the trap device is exposed to excessive temperature when the engine is operated at a light load such as deceleration after operating at high speed and high load. In other words, when operating at high speed and high load, the temperature of the trap material of the trap device increases.
The temperature is over 550℃, but due to the operating characteristics of diesel engines, at this high speed and high load, the oxygen concentration in the exhaust gas is insufficient at less than 5%, and unburned soot may remain on the trap material. Due to light load operation, the oxygen concentration in the exhaust gas increases to around 18%, and the trap material maintains a temperature of over 550℃ due to residual heat. As a result, the soot ignites and burns, and the internal temperature reaches over 1000℃. Such excessive temperatures can cause melting of the trap device.

Purpose of the invention The present invention was made in view of the problems of the prior art, and it is an object of the present invention to provide a technology for preventing an abnormal increase in the internal temperature of a trap device when light load operation starts after high speed/high load operation. With the goal.

Structure of the invention FIG. 1 shows the structure of the invention, in which the exhaust pipe 18 of the diesel engine 10 is provided with a particulate trap device 26, there is a bypass conduit 32 that bypasses it, and an on-off valve 34 is provided therein. . A sensor 58 detects the temperature inside the trap 26
Based on the signal from the sensor 60 that detects the engine load, the determining means 2 determines whether or not the engine is operating under a light load immediately after high speed and high rotation. The driving means 3 opens the on-off valve 34 during light load operation immediately after high speed, high load operation.

Embodiment FIG. 2 shows an embodiment of the present invention, in which 10 is the main body of a diesel engine, 12 is an intake manifold,
14 is an air cleaner, 16 is an exhaust manifold, 1
8 is an exhaust pipe. 20 is a fuel injection pump, 22
are vacuum pumps, each connected to the crankshaft 24 by a pulley and a belt, and driven to rotate.

Reference numeral 26 denotes a trap device that collects and removes particulate matter (particulate matter) in the exhaust gas, and is provided with a trap material 28 inside. Trap material 2
A heater 30 is provided in front of and close to the heater 8 . As is well known in the art, the heater 30 is driven every predetermined travel distance, during which it incinerates the particulates collected on the trapping material 28.

According to the invention, a bypass pipe 32 is connected to the exhaust pipe 18 so as to bypass the trap device 26. An on-off valve 34 is provided within the bypass pipe 32. The on-off valve 34 is normally kept fully closed, but as will be described later, it is opened during light load operation immediately after high load/high rotation operation. In order to control the on-off valve 34 in this manner, the on-off valve 34 is connected to an on-off valve drive actuator 40 via a link 38. The actuator 40 is of the diaphragm type in this embodiment and is connected to the link 38.
It consists of a diaphragm 401, a spring 402 that biases the diaphragm 401, and a negative pressure chamber 403. This negative pressure chamber 403 is selectively communicated between the air cleaner 14 and the vacuum pump 22 by an electromagnetic three-way valve 44 . That is, when the solenoid valve 44 is in a non-energized state, the negative pressure chamber 403 is connected to the pipe 46,
48 to the vacuum pump 22, and the negative pressure chamber 403 becomes negative pressure. As a result, the diaphragm 401 is pulled upward in the figure against the spring 402, and the on-off valve 3
4 is rotated counterclockwise to take a fully closed position. On the other hand, when the solenoid valve 44 is energized, the negative pressure chamber 403 is communicated with the air cleaner 14 via the pipes 46 and 50, as shown in black, the chamber 403 becomes atmospheric pressure, and the force of the spring 402 causes the diaphragm to 401 is pushed downward, and the on-off valve 34 is rotated clockwise until it assumes a fully open position.

Reference numeral 54 denotes a control circuit for driving the on-off valve 34 according to the present invention, and in this embodiment is configured as a microcomputer system. That is, the microcomputer receives signals from a group of sensors that detect a light load immediately after a high speed/high load, performs calculations based on the signals, and forms a drive signal to the solenoid valve 44. A temperature sensor 58 and an accelerator pedal position detection sensor 60 are provided as such a sensor group. Temperature sensor 58
is constructed as a thermistor embedded in the trap material 28 of the trap device, and an electrical signal corresponding to the temperature of the trap material 28 is obtained. On the other hand, the accelerator pedal position sensor 60 is configured as a potentiometer connected to the accelerator lever of the combustion injection pump 20, and obtains an electric signal according to the accelerator pedal position.

Microcomputer system is input port 7
0 and an output port 72. Input port 70
is connected to the temperature sensor 5 via the multiplexer 74.
8, connected to the accelerator pedal position sensor 60;
Necessary temperature information and load information are input. On the other hand, the output port 72 is connected to the heater 30 via a latch 76 and an amplifier 80.
2. Connected to the solenoid valve 44 via an amplifier 84. Input port 70 and output port 72 are bus 8
6 through microprocessing unit (MPU) 88, read-only memory (ROM) 9
0, and random access memory (RAM) 92
The on-off valve 34 is driven by performing necessary calculations based on the signals from each sensor.

In addition to the hardware configuration described above, the present invention has a software configuration that realizes the control of the present invention. Such software is naturally written as a program in the ROM 90, which will be explained below with reference to the flowchart shown in FIG.

In FIG. 3, 100 indicates the start of the program, and then, at 101, it is determined whether the trap device 28 is ready for regeneration, that is, the time to incinerate the particulates collected in the trap material 28. Yes
In this case, the process proceeds to step 102, where the normal processing for regenerating the trap material is performed. Since this process is well known to those skilled in the art, detailed explanation will be omitted.
However, at the same time as the heater 30 is energized, the on-off valve 34
It will only be stated that the opening degree of the trap material 28 is adjusted to maintain the temperature and air amount necessary for igniting the particulates collected in the trap material 28.

If it is determined in step 101 that it is not time for regeneration, the process branches to No and enters a routine for preventing an abnormal rise in temperature of the trap device according to the present invention. First, in step 103, the MPU 88 inputs data on the trap internal temperature T _F from the temperature sensor 58 stored in a predetermined area of the RAM 92. The program then proceeds to step 104, where it is determined whether the trap internal temperature T _F actually measured in this manner is greater than 450°C. The meaning of this determination will be described later. 104
If Yes, that is, if T _F > 450℃, then 10
6, it is determined whether the bypass valve 34 is closed at that time. If it is determined that the bypass valve 34 is closed, the process branches to Yes, and the process moves to 108, where it is determined whether the trap internal temperature T _F is 550° C. or higher.

In operations other than high rotation and high load, the temperature inside the trap
T _F did not exceed 550℃, the judgment was No, and 110
Proceed to. 110, MPU88 is output port 72
The terminal 721 of is set to High. Therefore, Latch 7
6 outputs a High signal, the solenoid valve 44 is energized and assumes the black port position, negative pressure is introduced into the negative pressure chamber 403, the diaphragm 401 is pulled upward, and the on-off valve 34 is closed.

If the engine is experiencing high rotation and high load operation when this next routine begins execution, the trap internal temperature T _F will exceed 550°C and
The determination in 08 is Yes, and the process proceeds to 116. 116
Then, the MPU inputs the contents of the RAM area that stores the data from the accelerator pedal opening sensor 60,
It is determined whether the load at that time is small, for example, whether it is equivalent to the load during deceleration. If No, the process goes to step 110 described above, but if Yes (that is, during light load operation), the process goes to 118, where the output port 722 becomes High, the latch 82 outputs Low, and as a result, the solenoid valve 44 is demagnetized and takes the white port position, and the negative pressure chamber 403 becomes atmospheric pressure, so the on-off valve 34 takes the open position by the action of the spring 402. As mentioned above, during light load operation immediately after high rotation and high load, the conditions are such that the soot in the trap ignites due to the high temperature inside the trap (over 550℃) and excess oxygen of up to 18%. By opening the valve 34, most of the exhaust gas is directed to the bypass pipe where the flow resistance is small, thereby avoiding an excess oxygen condition in the trap. In this case, the design is such that approximately 90% of the total exhaust gas passes through the bypass 32.

In this way, by opening the bypass valve 34, the trap internal temperature T _F decreases. However, T _F is 450
As long as the temperature exceeds .degree. C., it is determined as Yes at step 104, and the on-off valve is open at step 106, branching to No, so that the temperature inside the trap is gradually lowered. By adding hysteresis in this way, stable control can be performed.

When the temperature inside the trap drops to 450° C. or less, the determination at 104 is No, and the bypass valve is closed at 110.

Effects of the invention A bypass pipe is provided to bypass the trap device, and the on-off valve in the pipe is opened during light load operation immediately after high rotation and high load to prevent the trap from overheating. Furthermore, during light load operation, the amount of particulate emissions itself is small, so any increase in the amount of particulate emissions caused by opening the bypass can be ignored.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the essential configuration of the present invention, FIG. 2 is a diagram showing the configuration of an embodiment of the present invention, and FIG. 3 is a flowchart diagram showing the software configuration of the apparatus shown in FIG. 2. 10... Body, 18... Exhaust pipe, 26... Trap device, 32... Bypass pipe, 34... Open/close valve, 40... Actuator, 44... Solenoid valve,
54... Control circuit, 58... Temperature sensor, 60...
...Rotation speed sensor.

Claims (1)

[Scope of claim for utility model registration] In a diesel engine, a trap device for collecting particulates installed in the exhaust pipe of the engine, a bypass conduit connected to the exhaust pipe so as to bypass the trap device, and a bypass conduit installed in the bypass conduit. An on-off valve, a temperature sensor means for detecting the temperature inside the trap device, a load sensor means for detecting the load condition of the engine, and a signal from the temperature sensor and load sensor to determine whether or not it is a light load operation immediately after a high speed high load operation. A diesel exhaust purification device comprising a driving means for opening the on-off valve during light load operation immediately after high speed and high load operation.