JP2926769B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an exhaust gas purification device for an internal combustion engine, and more particularly, to an incineration process of particulates (exhaust particulates) collected in a trap in an exhaust passage by an electric heater. The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, which stabilizes regeneration of a trap by reliably performing an incineration process.

[Related Art] Exhaust gas discharged from an internal combustion engine contains unburned carbon particles and the like to which unburned hydrocarbons, sulfur oxides, nitrogen oxides, and the like are attached, and the particulates thereof are contained in the exhaust gas. When radiated into the atmosphere as so-called smoke, it pollutes the atmosphere and may cause harm to the human body.

For this reason, in recent vehicles, in order to eliminate the exhaust pollution, an exhaust gas purifying apparatus provided with an exhaust passage provided with a trap that collects particulates in exhaust gas and incinerates the collected particulates. There is. As an exhaust purification device of this type, an "exhaust purification device for an internal combustion engine" (Japanese Utility Model Laid-Open No. 62-49610) proposed by the present applicant is known.

In this proposal, as shown in FIG. 5, a trap c for adhering and collecting particulates is provided in an exhaust passage b of an internal combustion engine a, and an electric heater d is provided immediately upstream of the trap c. The particulates collected in the trap c are periodically reburned to regenerate the trap c.

Further, in the proposal, the trapping of the particulates in the trap c progresses, and the controller h causes the trap h to be activated by the input signal from the trap inlet temperature sensor e and the engine speed sensor g provided in the fuel injection pump f of the internal combustion engine a. When it is determined that the re-combustion time has been reached, all the exhaust gas is bypassed to the trap c, and the electric heater d is operated to heat the trap c until the trap inlet temperature reaches the set temperature. Is reached, air is sent to the trap c to reburn the particulates.

[Problems to be Solved by the Invention] The propagation of particulate reburning is greatly affected by the temperature of the entire trap c. In other words, when the temperature is low, the burning of the particulates after ignition enters the inside from the trap inlet and receives the cooling action and does not reach the outlet side. As a result, there is a disadvantage that the regeneration of the trap c becomes uncertain.

Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to control the temperature of the entire trap so as to be equal to the temperature set at the trap inlet to propagate the reburn of particulates. It is an object of the present invention to provide an exhaust gas purifying apparatus for an internal combustion engine capable of performing stable regeneration of a trap by performing the satisfactorily.

Means for Solving the Problems In order to achieve the above object, the present invention provides a trap for collecting particulates in exhaust gas, an electric heater for heating the trap to incinerate the particulates, In a particulate trap having air supply means for burning the collected particulates and a temperature sensor for detecting the inlet temperature of the trap, when the trap is regenerated, the electric heater is energized to reduce the inlet temperature of the trap. After reaching the set temperature, the energization control to repeat the ON and OFF of the electric heater is performed by a smaller number of times as the detection value of the temperature sensor before regeneration is higher, so that the set temperature is maintained, and then the air supply is performed. By means, air is supplied to the trap.

[Operation] Particulates in the exhaust gas are collected by a trap. At the time of trap regeneration, the electric heater is energized to maintain the set temperature after the trap inlet temperature reaches the set temperature. The energization control for repeating the ON / OFF of the electric heater is performed to raise the temperature of the entire trap to a temperature optimum for combustion propagation of the trap, that is, a trap regeneration temperature. As a result, the trap can be satisfactorily reproduced.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, an exhaust passage 1 of an internal combustion engine (not shown)
Is provided with a trap 2 for adhering and accumulating particulates contained in exhaust gas and collecting the trapped particulates.
And a bypass passage 3 is formed by connecting the exhaust passages 1 on the upstream side and the downstream side. A trap inlet valve 4 for opening and closing the exhaust passage 1 is provided near the inlet of the trap 2 on the upstream side of the trap 2 in the exhaust passage 1 and downstream of the branch point of the bypass passage 3, and a bypass in the bypass passage 3 is provided. A bypass valve 5 for opening and closing the bypass passage 3 is provided near a branch point of the passage 3.

An air introduction pipe 6 for introducing air into the trap 2 is connected to the exhaust passage 1 between the trap 2 and the trap inlet valve 4 on the upstream side thereof, and an air pump 7 is connected to the air introduction pipe 6. The air introduction pipe 6 and the air pump are connected to form air supply means for supplying air to the trap 2 and burning the particulates collected by the trap 2.

Immediately before the trap 2 downstream of the trap inlet valve 4 and upstream of the trap 2, the inlet of the trap 2 is set to a set temperature (about 600 to 700
° C), and after heating, an electric heater 8 which is controlled so as to keep the entire trap 2 at substantially the set temperature is attached. The trap 2 has an inlet inside the trap 2. A trap inlet temperature sensor 9 for detecting the side temperature is provided.

The trap inlet valve 4, the bypass valve 5, the air pump 7 and the electric heater 8 are connected to a controller (microcomputer or the like) 10, and their operations are electronically controlled by the controller 10. . The controller 10 receives a signal from the trap inlet temperature sensor 9, a rotation speed and a load signal from an engine speed sensor and an engine load sensor (not shown) provided in a fuel injection pump (not shown) of the internal combustion engine, and the like. Has been input, and the controller 10 has an engine speed sensor,
The regeneration time (reburning time) of the trap 2 is determined by integrating the rotation speed and the load signal from the engine load sensor, and the trap inlet valve 4, the bypass valve 5, The operation of the air pump 7, the electric heater 8, and the like is controlled.

That is, when the controller 10 determines that it is time to regenerate the trap 2, the controller 10 operates to open the bypass valve 5 and close the trap inlet valve 4 so that all the exhaust gas flow from the internal combustion engine flows to the bypass passage 3 side. Initial with the temperature signal from the inlet temperature sensor 9 (before heating)
Trap inlet temperature T ₁ is the input to heat the trap 2 by performing the energization to the electric heater 8. Then, the set temperature at which the trap inlet temperature can be reburned (trap regeneration temperature) T ₂
When becomes, thereafter are energized electric heater 8 turned ON number of times corresponding to the initial trap inlet temperature T _1, as performed by repetitive operation of OFF.

Next, the operation of the present invention will be described with reference to the diagrams of FIGS. 2 and 3 and the flowchart of FIG.

First, during normal operation, the trap inlet valve 4 of the exhaust passage 1 is open and the bypass valve 5 of the bypass passage 3 is closed. Therefore, all of the exhaust gas from the internal combustion engine passes through the trap 2 and is discharged to the outside. The particulates contained in the exhaust gas adhere to and accumulate on the trap 2 and are collected there.

On the other hand, the controller 10 judges whether or not it is time to reburn and burn the particulates collected in the trap 2 according to the engine speed and the engine load (regeneration time of the trap 2).

When it is determined to have reached the regeneration timing to close the trap inlet valve 4 opens the bypass valve 5, the flow all the exhaust gas to the bypass passage 3, the trap inlet temperature the initial trap inlet temperature T ₁ of the time this Detected by the sensor 9 and at the same time, the electric heater 8 is energized (ON) to heat the trap 2. Next, when the trap inlet temperature reaches the set temperature T _2, the electric heater 8 from an initial trap inlet temperature T ₁ of
The number of times of ON and OFF is determined by the map of the controller 10 stored based on FIG. 2, and the electric heater 8 is turned ON and OFF as shown in FIG. 3 by the determined number.

In this case, the map of the controller 10, as an initial trap inlet temperature T ₁ is lower, ON of the electric heater 8, a number of times to OFF, as initial trap inlet temperature T ₁ is higher, ON of the electric heater 8, OFF from being set to reduce the number of, it can be maintained so as to correspond to the trap inlet temperature T ₁ of the set temperature T ₂ trap inlet temperature. That is, the electric heater 8
ON, the whole trap 2 the temperature of the whole heat is conducted trap 2 on the outlet side of the trap 2 is increased by OFF is always kept substantially the set temperature T _2. If ON the energization heater 8, is not particularly limited OFF method, as is apparent from Figure 3, if it exceeds the set temperature T ₂ and OFF, which falls below the lower set temperature T ₂ 'than By turning ON, the object of the present invention can be achieved.

Then, a predetermined amount of air is introduced into the trap 2 by the air pump 7 to promote combustion and propagation of the trap 2. That is, completely stopping the energization of the electric heater 8 When the predetermined time t ₁ has elapsed from when the air introduction starting (OFF), then stop the air pump 7 When the predetermined time t ₂ has elapsed from when the air introduction starting (OFF), then The trap inlet valve 4 is opened and the bypass valve 5 is closed.

As described above, in the present embodiment, even if the initial (before heating) trap inlet temperature T ₁ has a difference in height, the trap inlet set temperature by heating of the electric heater 8 is changed according to the temperature T _1. the heating pattern of T ₂ increases after the electric heater 8, a pattern of changing the time and number of times of energization current of the electric heater 8 it is so arranged that the (oN, patterns or more or less OFF times), trap 2 inlet-side heat transfer to the outlet side of the trap 2 than is effectively performed entire trap 2 is kept substantially set temperature T ₂ regardless of the initial temperature. As a result, during the reburning, the burning of the particulates is favorably propagated, and the trap can be regenerated stably and reliably.

In this embodiment, the re-combustion air is supplied to the trap 2 by the air pump 7 at the time of the re-combustion. However, the exhaust gas may be introduced by slightly opening the trap inlet valve 4 regardless of this. If a very small amount of air is supplied to the trap 2 by the air pump 7 when the electric heater 8 is turned on,
The heat transfer from the inlet side to the outlet side in the trap 2 can be made faster.

[Effects of the Invention] According to the present invention, the following excellent effects are exhibited.

Particulate combustion during trap regeneration is propagated throughout regardless of the initial temperature, and trap regeneration can be performed stably and reliably.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing the relationship between the initial trap inlet temperature and the number of times the electric heater is turned on and off according to the present invention. FIG. 3 is a diagram showing the relationship between the elapsed time and the trap inlet temperature in the electric heater according to the present invention. FIG. 4 is a flow chart of one embodiment according to the present invention, and FIG. 5 is a schematic configuration diagram showing a conventional example. In the figure, 1 is an exhaust passage, 2 is a trap, 3 is a bypass passage, 4 is a trap inlet valve, 5 is a bypass valve, 7
Is an air pump, 8 is an electric heater, and 10 is a controller.

Claims (1)

(57) [Claims] 1. A trap for collecting particulates in exhaust gas, an electric heater for heating the trap when the trap is regenerated, and an air supply means for burning the collected particulates. And, in a particulate trap having a temperature sensor for detecting the inlet temperature of the trap, during trap regeneration, the electric heater is energized to maintain the set temperature after the trap inlet temperature reaches the set temperature, The higher the detected value of the temperature sensor before the regeneration, the smaller the set number of times, the ON / OFF of the electric heater is turned on and off, and then the air supply means supplies air to the trap. An exhaust gas purification device for an internal combustion engine.