JPH0134648Y2 - - 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 a technique for preventing 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 subsequent light load operation, the oxygen concentration in the exhaust gas increased to around 18%, and the trap material was heated to 550℃ due to residual heat.
Keep above. 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 present invention, in which a particulate trap device 26 is provided in the exhaust pipe 18 of the diesel engine 10, and an intake throttle valve 34 is provided in the intake pipe 13. Based on the signals from the sensor 58 that detects the temperature inside the trap device 26 and the sensor 60 that detects the engine load, the determining means 2 determines whether or not the engine is operating at a light load immediately after high speed and high load. The driving means 3 drives the intake throttle valve 34 to open and close depending on whether the answer is Yes or No.

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,
13 is an intake pipe, 14 is an air cleaner, 16 is an exhaust manifold, and 18 is an exhaust pipe. 20 is a fuel injection pump, and 22 is a vacuum pump, each of which is connected to a crankshaft 24 by a pulley and a belt, and is driven to rotate.

26 is a trap device that collects and removes particulates 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. 32
is a bypass pipe that controls the exhaust gas to the trap device 26 during incineration, and 33 is an on-off valve that controls the amount of bypass.

According to the invention, an intake throttle valve 34 is provided in the intake pipe 13. The intake throttle valve 34 is normally kept fully open, but as will be described later, it is closed during light load operation immediately after high load and high rotation. In order to control the throttle valve 34 in this manner, the throttle valve 34 is connected to the on-off valve drive actuator 4 via a link 38.
Concatenated to 0. This actuator 40 is of a diaphragm type in this embodiment, and includes a diaphragm 401 connected to the link 38, and a diaphragm 401 connected to the link 38.
01 and a negative pressure chamber 403. This negative pressure chamber 403 has an electromagnetic three-way valve 44
The air cleaner 14 and the vacuum pump 22 are selectively communicated by the air cleaner 14 and the vacuum pump 22. That is, when the solenoid valve 44 is in a non-energized state, the negative pressure chamber 403 is
It is connected to the vacuum pump 22 via pipes 46 and 48, and the negative pressure chamber 403 becomes negative pressure. As a result, the diaphragm 401 is pulled to the left in the figure against the spring 402, and the throttle valve 34 is rotated counterclockwise. It is moved and reaches the fully open position. On the other hand, when the solenoid valve 44 is energized, the negative pressure chamber 403 is connected to the piping 46,
The chamber 403 is at atmospheric pressure, and the force of the spring 402 pushes the diaphragm 401 to the right to close the throttle valve 34.
is rotated clockwise until it assumes the closed position as shown by the dashed line.

Reference numeral 54 denotes a control circuit for driving the throttle 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 light-load operation immediately after high-speed/high-load operation, 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. The temperature sensor 58 is configured 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
It is configured as a potentiometer connected to the accelerator lever, and an electrical signal is obtained according to the position of the accelerator pedal.

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 through a latch 76 and an amplifier 80, and to the solenoid valve 44 through a latch 82 and 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 throttle 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, it is time to incinerate the particulates collected in the trap material 28. Yes
In this case, the process proceeds to step 102 and the processing normally performed 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 33
It will only be stated that the opening degree of the trapping material 28 is adjusted to maintain the temperature and air amount necessary for igniting the particulates collected in the trapping 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 program 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. Yes with 104
If so, that is, if T _F >450°C, the process proceeds to 106, where it is determined whether or not the intake throttle valve 34 is open at that time. If it is determined that the throttle valve 34 is open, the process branches to Yes, and the process moves to step 108, where the temperature inside the trap is determined.
It is determined whether T _F is 550°C or higher.

In operations other than high rotation and high load, the temperature inside the trap
T _F does not exceed 550℃, the judgment is No, and 110
Proceed to. 110, MPU88 is output port 72
The terminal 721 of is set to High. Therefore, the clutch 82 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, and the diaphragm 401 is pulled.
The throttle valve 34 becomes fully open.

Next, when this routine begins execution, if the engine is experiencing high rotation and high load operation, the trap internal temperature T _F will exceed 550°C and 10
The determination in step 8 is Yes, and the process proceeds to step 116. At 116, the MPU inputs the contents of the RAM area storing 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 (i.e., during light load operation), the process goes to 118, 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 throttle valve 34 takes the closed position by the action of the spring 402. As mentioned above, when the load is light immediately after high rotation and high load, the high temperature inside the trap (over 550℃) and excess oxygen of up to 18% are conditions that cause the soot inside the trap to ignite. By closing the valve 34, the amount of air introduced into the engine 10 is suppressed, and an excess oxygen condition in the trap is avoided.

In this way, by opening the throttle valve 34, the trap internal temperature T _F decreases. However, as long as T _F exceeds 450°C, the determination at 104 is Yes, and the throttle valve is closed at 106, which branches 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 below 450° C., the determination at 104 is No, and the throttle valve 34 is opened at 110.

Effects of the invention By closing the intake throttle valve provided in the intake pipe during light load operation immediately after high speed/high load operation, it is possible to avoid heating of the trap due to excessive air flowing into the trap device 26. .

[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, 13... Intake pipe, 18... Exhaust pipe, 26... Trap device, 32... Bypass pipe, 34... Throttle 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 installed in the exhaust pipe of the engine to collect particulates, an intake throttle valve installed in the intake pipe of the engine, and a temperature sensor that detects the temperature inside the trap device. means, load sensor means for detecting the load state of the engine; means for determining whether or not it is during light load operation immediately after high speed/high load operation based on the signals from the temperature sensor and the load sensor; and an intake throttle valve in response to the signal from the determination means. A diesel exhaust purification device consisting of a drive means for opening and closing.