JPH0364610A - Exhaust gas purifying device for internal combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to burn particulates, and thereby efficiently regenerate trapping by controlling energization of an electric heater based on the temperature at the inlet port of a trap arresting particulates in exhaust gas. CONSTITUTION:A trap 2 is interposed in the exhaust passage 1 of an internal combustion engine in order to arrest particulates contained in exhaust gas. Meanwhile, an electric heater 8 is interposed just in front of the upstream side of the trap 2 at the downstream side of a trap inlet port valve 4. The electric heater 8 is controlled by a controller 10 based on the detected signal from a trap inlet port temperature sensor 9 and the like. That is, a bypass valve 5 is opened when required, on the other hand, after the whole of exhaust gas has been repelled out to a bypass passage 3 with the trap inlet valve 4 closed, the trap 2 is heated up by the electric heater 8. By this constitution, the burn-out of the particulates, and the regeneration of the trap 2 can be efficiently effected.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an exhaust gas purification device for an internal combustion engine, and particularly to a device for incinerating particulates (exhaust particles) collected in a trap in an exhaust passage using an electric heater. The present invention relates to an exhaust gas purification device for an internal combustion engine, in which trap regeneration is stabilized by reliably performing incineration processing.

[Prior Art] Exhaust gas emitted from internal combustion engines contains unburned carbon particles to which unburned hydrocarbons, sulfur oxides, nitrogen oxides, etc. are attached, and their particulates When emitted into the atmosphere as so-called smoke, it pollutes the atmosphere and causes adverse effects on the human body.

For this reason, in order to eliminate exhaust pollution, modern vehicles have exhaust purification devices that are equipped with a trap in the exhaust passage that collects particulates in the exhaust gas and incinerates the collected particulates. There is. As this type of exhaust purification device, "Exhaust purification device for internal combustion engine" (Japanese Utility Model Publication No. 49610/1983) proposed by the present applicant is known.

As shown in Fig. 5, this proposal involves installing a trap C in the exhaust passage of an internal combustion engine a to collect particulates by depositing them, and installing an electric heater d immediately before the upstream side of the trap C. The particulates collected in the trap C are periodically re-burned to regenerate the trap C.

In addition, the proposal is that as the collection of particulates progresses in the trap C, the controller h triggers the trap based on input signals from the trap inlet temperature sensor e and the engine speed sensor g installed in the fuel injection pump f of the internal combustion engine a. When it is determined that the reburning time of C has been reached, all the exhaust gas is bypassed through trap C, and electric heater d is activated to heat trap C until the trap inlet temperature reaches the set temperature. Once the temperature is reached, trap C
The particulates are re-combusted by blowing air into them.

[Problems to be Solved by the Invention] However, even if the temperature on the inlet side of the trap C is the set temperature, the temperature between the outlets of the trap C is not necessarily equal to that on the inlet side.

That is, even if the trap inlet temperature is at the set temperature, if the ripening transfer is not sufficiently carried out, the trap outlet temperature will be low, and the combustion propagation of the particulates in the trap C will be poor. As a result, the problem arises that the regeneration of trap C becomes uncertain.

Therefore, the present invention has been made in view of the above circumstances,
The purpose of this is to maintain a stable trap by controlling the temperature of the entire trap to be the same as the set temperature at the trap inlet to ensure good propagation of particulate re-burning. An object of the present invention is to provide an exhaust purification device for an internal combustion engine that can perform regeneration.

[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 and incinerating the particulates,
The controller includes a controller that calculates the energization time and number of times of energization of the electric heater corresponding to the trap regeneration temperature from the trap inlet temperature, and controls the electric heater.

[Function] Particulates in the exhaust gas are collected by the trap. The controller detects the inlet temperature of the trap during the trap regeneration period, and operates the electric heater in accordance with the level of the inlet temperature.

That is, the energization time and number of times of energization of the electric heater are calculated according to the level of the inlet temperature, and the temperature of the entire trap is raised to the optimal temperature for combustion propagation of the trap, that is, the trap regeneration temperature. As a result, the trap can be regenerated well.

[Example code] 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 that collects and collects particulates contained in exhaust gas. A bypass passage 3 is formed by connecting the exhaust passage 1 with 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 on the downstream side of the branch point of the bypass passage 3. This bypass passage 3 is located near the branch point of the passage 3.
A bypass valve 5 for opening and closing is provided.

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. An air pump 7 is connected as an air supply means.

Immediately before the upstream side of the trap 7''2 on the downstream side of the trap inlet valve 4, the inlet of this trap 2 is heated to a set temperature (approximately 600~600℃).
The trap 2 is equipped with an electric heater 8 whose operation is controlled so as to heat the trap 2 to a temperature of 700° C. and keep the entire trap 2 at approximately the set temperature after heating. A trap inlet temperature sensor 9 is provided to detect the inlet side temperature.

In addition, the trap inlet valve 4 and the bypass valve 5 described above are also included.
, the air pump 7 and the electric heater 8 are connected to a controller (such as a microcomputer) 10, and their operations are electronically controlled by the controller 10. This controller 10 receives signals from a trap inlet temperature sensor 9, and rotation speed and load signals 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, etc. The controller 10 determines the regeneration timing (reburning timing) of the trap 2 by integrating the rotation speed and load signals from the engine rotation speed sensor and the engine load sensor, and also calculates the regeneration timing (reburning timing) from the trap inlet temperature sensor 9. Trap inlet valve 4. Bypass valve 5. air pump 7,
It is designed to control the operation of the electric heater 8 and the like.

That is, when the controller 10 determines that it is time to regenerate the trap 2, it opens the bypass valve 5 and closes the trap inlet valve 4 to allow all the exhaust gas flow from the internal combustion engine to flow to the bypass passage 3 side. The trap inlet temperature T1 (before heating) is measured and the electric heater 8 is energized to heat the trap 2. and,
When the trap inlet temperature reaches the set temperature (trap regeneration temperature) T2 at which re-combustion is possible, the electric heater 8 is turned on and off a number of times according to the initial trap inlet temperature T.
This is done by repeated operations of the FF.

Next, the operation of the present invention will be explained using the diagrams in FIGS. 2 and 3 and the flowchart in FIG. 4.

First, during normal driving, 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. Particulates contained in the exhaust gas adhere to and accumulate on the trap 2, where they are collected.

On the other hand, the controller 10 determines whether it is time to re-burn and incinerate the particulates collected in the trap 2 (regeneration time of the trap 2) based on the engine speed and engine load.

When it is determined that the regeneration time has come, the bypass valve 5 is opened and the trap inlet valve 4 is closed, allowing all of the exhaust gas to flow into the bypass passage 3, and the initial trap inlet temperature T1 at this time is measured by the trap inlet temperature sensor. At the same time, the electric heater 8 is turned on to heat the trap 2. When the trap inlet temperature reaches the set temperature T2, the electric heater 8 is turned on from the initial trap inlet temperature T. The number of times the electric heater 8 is turned off is determined based on the map stored in the controller 10 based on FIG. 2, and the electric heater 8 is turned on for the determined number of times as shown in FIG.
N, turn off.

In this case, the map of the controller 10 indicates that the lower the initial trap inlet temperature T1, the more the electric heater 8 is turned on and off.
The greater the number of times and the higher the initial drag inlet temperature T1, the more
Since the electric heater 8 is set to be turned on and off less frequently, the trap inlet temperature can be maintained at the set temperature T2 in correspondence with the trap inlet temperature T. That is, by turning the electric heater 8 ON and OFF, heat is transferred to the outlet side of the trap 2, and the temperature of the entire trap 2 rises, so that the entire trap 2 is always maintained at approximately the set temperature T2.

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, when a predetermined time 1+ has elapsed since the start of air introduction, the electricity to the electric heater 8 is completely stopped (OFF), and then when a predetermined time t2 has elapsed since the start of air introduction, the air pump 7 is stopped (OFF>, and then the trap inlet is turned OFF). Valve 4 is opened and bypass valve 5 is closed.

As described above, in this embodiment, even if the initial (before heating) trap inlet temperature T is high or low, the trap inlet set temperature T2 is adjusted according to the high or low temperature T1. Since the heating pattern of the electric heater 8 after rising is a pattern that changes the energization time and number of energizations of the electric heater 8 (a pattern that decreases or increases the number of ON and OFF times), the inlet of the trap 2 The temperature is effectively transmitted from the side to the outlet side of the trap 2, and the entire trap 2 is always maintained at approximately the set temperature T2. As a result, combustion of particulates is propagated well during reburning, and trap regeneration can be performed stably and reliably.

In this embodiment, the air pump 7 supplies reburning air to the trap 2 during reburning, but the trap inlet valve 4 may be slightly opened to introduce exhaust gas. If a very small amount of air is supplied to the trap 2 by the air pump 7 when the heater 8 is turned on,
Heat transfer from the inlet side to the outlet side of the trap 2 can be made faster.

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

Combustion of particulates during trap regeneration is propagated well, and trap regeneration can be performed stably and reliably.

[Brief explanation of drawings]

FIG. 1 is a general Q configuration diagram showing one embodiment of the present invention, and FIG.
The figure is a line diagram showing the relationship between the initial trap inlet temperature and the number of ON/OFF operations of the electric heater according to the present invention, and Figure 3 is a line diagram showing the relationship between the elapsed time and the trap inlet temperature in the electric heater according to the present invention. 4 is a flowchart of an embodiment of the present invention, and FIG. 5 is a schematic top view of 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)

[Claims] 1. A trap that collects particulates in exhaust gas, an electric heater that heats the trap and incinerates the particulates, and an energization time of the electric heater that corresponds from the trap inlet temperature to the trap regeneration temperature. An exhaust purification device for an internal combustion engine, comprising: a controller that calculates the number of times of energization and controls the electric heater.