JPH068256Y2 - Exhaust particulate purification device for diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to an exhaust particulate purifying apparatus for a diesel engine in which particulates in exhaust gas are ignited and burned by an electric heater.

<Prior Art> Exhaust gas emitted from a diesel engine is passed through a trap provided in the exhaust passage, and soot and other fine particles (particulates) contained in the exhaust gas form a porous ceramic material that constitutes the trap. It is collected by a collection material composed of a body. Since particulates accumulate in the trap over time, pressure loss increases and engine power loss increases. For this reason, it is necessary to burn off the particulates and regenerate the trap when the particulates have accumulated to some extent. Regeneration of the trap is performed by providing an electric heater on the upstream end surface of the trapping material and igniting and burning the particulates by the electric heater.

<Problems to be solved by the invention> In the conventional exhaust particulate purifying apparatus, when the trap regeneration is completed, the electric heater is turned off regardless of the engine operating state, and the trap is bypassed. The throttle valve in the bypass passage was controlled from open to closed. If the engine is not injecting at the end of the trap regeneration, the temperature of the trap is low (about 100 to 2).
Exhaust gas flows in a large amount. At this time, since the temperature of the trap rises to about 80 ° C. due to the combustion of particulates, if it is rapidly cooled by the exhaust gas having a low temperature, a large thermal stress may occur and the trap may be damaged.

The present invention has been made for the purpose of solving the above-mentioned problems, and an object of the present invention is to provide an exhaust gas purification apparatus for a diesel engine, which can prevent the trap from being damaged due to the inflow of low temperature exhaust gas at the end of the trap regeneration.

<Means for Solving Problems> In order to solve the above problems, the present invention provides a trap provided with an electric heater in an exhaust passage of a diesel engine, and a bypass passage having a throttle valve so as to bypass the trap. Then, in the exhaust particulate purifying device of a diesel engine that opens the throttle valve and ignites and burns particulates in exhaust gas with the electric heater, a temperature sensor that measures the temperature of the exhaust gas flowing into the trap, and the temperature When the temperature information of the exhaust gas is input from the sensor and the temperature of the exhaust gas flowing into the trap is detected to be below a preset temperature at the end of trap regeneration, the bypass valve is held open until a predetermined time elapses. And a computer for controlling the operation.

<Operation> When the temperature of the exhaust gas flowing into the trap at the end of the trap regeneration is equal to or lower than the preset temperature, the trap is prevented from being damaged by holding the bypass valve in the open state until a predetermined time elapses. .

<Embodiment> The present invention will be described in detail below with reference to an embodiment shown in the drawings.

FIG. 1 is a schematic view showing an exhaust particulate purifying apparatus according to the present invention. As shown in this figure, the exhaust passage 1 of a diesel engine (not shown) is provided with a trap 2 for collecting particulates in exhaust gas and a bypass passage 3 so as to bypass the trap 2. A throttle valve 4 is arranged in the bypass passage 3 and is opened / closed by a solenoid valve 5 and an air cylinder 6. A trapping material 7 is loaded into the trap 2, and an electric heater 8 for igniting particulates is disposed upstream of the trapping material 7. A dedicated alternator 9 for supplying electric power to the electric heater 8 is connected to the electric heater 8, and this alternator 9 uses a thing which can supply a voltage of 24V or 24V or more to the electric heater 8 and uses a particulate. Ignite and burn efficiently. Further, a temperature sensor 10 for measuring the temperature of the exhaust gas flowing into the trap 2 is installed on the upstream side of the trap 2, and further on the upstream side and the downstream side of the trapping material 7, the trap 2 due to the accumulation of particulates is trapped. Pressure sensors 11a and 11b for detecting pressure loss are installed, and temperature information and pressure loss information from the temperature sensor 10 and the pressure sensors 11a and 11b are input to a computer (ECU) 12. The computer 12 supplies a field current a for power generation to the alternator 9 from a vehicle-side battery 13 which is a power supply (12V system) of electric equipment of the vehicle such as a headlight and a tail lamp to energize the electric heater 8 and also an electromagnetic valve. It has a control function of outputting an open signal b to 5 to control the opening / closing of the throttle valve 4 via the air cylinder 6 and adjusting the flow rate of the exhaust gas flowing through the trap 2 to regenerate the trap 2. Then, at the end of the reproduction of the trap 2,
When the temperature of the exhaust gas flowing into the trap 2 is low, it has a control function of holding the throttle valve 4 in an open state until a predetermined time elapses. Reference numeral 14 is an alternator on the vehicle side (12V system).

Next, the operation of the apparatus of the present invention constructed as described above will be explained based on the flow chart shown in FIG. Normally, the throttle valve 4 in the bypass passage 3 is closed, so that the exhaust gas flows through the trap 2, and the particulates therein are collected by the trapping material 7 and purified, and then discharged into the atmosphere. . When particulates are deposited on the trap 2 as time passes, the pressure sensors 11a, 11
detected in b. Based on the deposition information from the pressure sensors 11a and 11b, the computer 12 issues a command to supply a field current a for power generation from the battery 13 to the alternator 9 for the electric heater 8, and energizes the electric heater 8. An open signal b is output to the solenoid valve 5, the throttle valve 4 is opened via the air cylinder 6, and the particulate is ignited and burned to regenerate the trap 2. Then, when the regeneration time t of the trap 2 has passed a predetermined time t ₀ , the power supply to the electric heater 8 is stopped based on a command from the computer 12. Then, the computer 12 uses the temperature sensor 1
The temperature T of the exhaust gas flowing into the trap 2 is set to a preset temperature T ₀ (for example, 400
When it is detected that the temperature is higher than about (° C.), a closing signal is output to the solenoid valve 5, control is performed to close the throttle valve 4 via the air cylinder 6, and the regeneration of the trap 2 is completed. At this time, the temperature T of the exhaust gas flowing into the trap 2 is a preset temperature.
When it is detected that T ₀ (for example, about 400 ° C.) has not been reached, the time t ₁ during which the exhaust gas does not reach the temperature T ₀
After a predetermined time t ₂ (the time when the trap 2 is gradually cooled from the high temperature state and the thermal stress does not increase even if the low temperature exhaust gas flows in), the throttle valve 4 is controlled to be closed and the trap 2 End playback.

<Effects of the Invention> As described above in detail with the embodiments, according to the present invention, when the temperature of the exhaust gas flowing into the trap at the end of the trap regeneration is equal to or lower than the preset temperature, the bypass valve is set to a predetermined value. By maintaining the open state as time passes, even if low-temperature exhaust gas flows into the trap, large thermal stress does not occur, and therefore damage to the trap can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an exhaust particulate purifying apparatus according to the present invention, and FIG. 2 is a flow chart showing the operation of the apparatus. In the drawings, 1 is an exhaust passage, 2 is a trap, 4 is a throttle valve, 7 is a trapping material, 8 is an electric heater, 9 is an alternator, 10 is a temperature sensor, 11a and 11b are pressure sensors, and 12 is a computer (ECU). , 13 are batteries.

Claims (1)

[Scope of utility model registration request] 1. A trap provided with an electric heater in an exhaust passage of a diesel engine, and a bypass passage having a throttle valve so as to bypass the trap are provided, and the throttle valve is opened to remove the exhaust gas in the exhaust gas by the electric heater. In a diesel engine exhaust particulate purification device that ignites and burns particulates, a temperature sensor that measures the temperature of the exhaust gas flowing into the trap, and input temperature information of the exhaust gas from the temperature sensor, and at the end of trap regeneration, Diesel, comprising: a computer that controls to hold the bypass valve open until a predetermined time elapses when it is detected that the temperature of the exhaust gas flowing into the trap is below a preset temperature. Exhaust particulate purification system for engines.