JPH0531206Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an exhaust gas purification device for an internal combustion engine, and particularly to one in which exhaust particulates collected in a trap in an exhaust passage are incinerated using an electric heater. The present invention relates to an exhaust gas purification device for an internal combustion engine which aims to shorten the regeneration time and reduce power consumption as much as possible by re-burning the trap.

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

For this reason, recent vehicles are equipped with exhaust gas purification devices to eliminate exhaust pollution. This purification device is equipped with a trap that deposits and collects exhaust particulates in the exhaust passage of an internal combustion engine, and a heating means is installed upstream of this trap to periodically collect the collected exhaust particulates. It is known that traps are regenerated by being incinerated. Furthermore, the heating means includes a method of reducing the intake air amount of the internal combustion engine using a throttle device installed in the intake passage, thereby bringing the air-fuel ratio closer to the stoichiometric air-fuel ratio and increasing the temperature of the exhaust gas itself to be discharged. This is commonly used to incinerate the collected exhaust particles using the high-temperature exhaust gas.

[Problems that the invention aims to solve] However, in the normal driving range of a vehicle, taking into consideration the drivability of the vehicle, it is not possible to restrict the amount of intake air unnecessarily, and the exhaust particulates collected in the trap cannot be sufficiently re-burned. It was difficult to raise the temperature of the exhaust gas to a temperature sufficient to remove it. For this reason, attempts have been made to lower the re-combustion temperature of exhaust particulates by using catalysts or fuel additives, but there is still a problem that the re-combustion cannot be achieved sufficiently.

Therefore, there is a method of attaching an electric heater to the trap as an auxiliary heating means during reburning.
If all the exhaust gas from the internal combustion engine were to be introduced into the trap and re-combusted, a large amount of electricity would be required, and the capacity of the batteries and generators installed in the vehicle would be insufficient, making it difficult to put it into practical use. It was hot.

Another method is to bypass the trap entirely during reburning, introduce secondary air for combustion into the trap, and use only an electric heater as the heating means for reburning. There is a risk that the combustion temperature will become too high and cause the trap to melt. For this reason, in this type of device, the amount of secondary air introduced is adjusted according to the temperature of the trap, and the reburning temperature is controlled to be below the melting temperature of the trap. 59−101518
It is proposed in the Publication No. However, in this proposal, the temperature of the electric heater is not controlled, and secondary air is introduced at the same time as the electric heater is energized, so it is difficult to raise the temperature of the trap to a temperature that allows reburning. It took a long time to complete the process, and it consumed a lot of power.

In addition, when all exhaust gas is bypassed during reburning, the reburning time must be shortened as much as possible in order to minimize the amount of exhaust particulates released into the atmosphere during the reburning. There is.

[Purpose of the invention] The present invention was devised in consideration of the above circumstances, and its purpose is to shorten the re-burning time of exhaust particulates collected in the trap as much as possible, and to reduce the power consumption. An object of the present invention is to provide an exhaust gas purification device for an internal combustion engine that can reduce the amount of gas and prevent trap melting and damage.

[Structure and operation of the invention] The invention includes a trap disposed in the exhaust passage of an internal combustion engine, an electric heater that heats the trap,
means for supplying air to the trap; a passage that bypasses the trap; a passage switching valve that switches the passage between the bypass passage and the exhaust passage; and a passage switching valve that opens the bypass passage at predetermined intervals. side, the trap is rapidly heated by supplying a large current to the heater, and when the temperature at the inlet side of the trap reaches a temperature at which exhaust particulates can be re-combusted, the energization value to the heater is reduced to perform normal heating. ,
The apparatus further includes a control device that controls the operation of the air supply means when the inlet side temperature reaches a predetermined temperature higher than the recombustion temperature during the transition to normal heating.

According to the above configuration, in the early stage of regeneration, the trap is rapidly heated by applying a large current to the electric heater while the exhaust gas is bypassed, so that the trap temperature rises above the temperature at which exhaust particulates can be re-combusted. As a result, the trap playback time can be shortened and power consumption can be reduced.

In addition, after the temperature on the inlet side of the trap reaches or exceeds the re-combustion temperature, the energization value to the heater is reduced and normal heating is performed, but during this transition to normal heating, the inlet side temperature further increases and reaches a predetermined level. When the temperature is reached, air is introduced into the trap and re-combustion begins, so after air is introduced, the heater temperature is approximately at a temperature that allows the combustion of exhaust particulates to continue stably, preventing rapid re-combustion of exhaust particulates. Partial erosion of the trap can be prevented.

[Embodiment] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in FIG. 1, an exhaust passage 2 of an internal combustion engine 1
A trap 3 is provided to deposit and collect exhaust particulates contained in the exhaust gas, and a bypass passage 4 is provided in parallel with the trap 3 to connect the upstream and downstream exhaust passages 2. It is formed. A flow path switching valve 7 is provided at the branching portion 5 and the confluence portion 6 of the bypass passage 4 and the exhaust passage 2 to open and close the bypass passage 4 and the exhaust passage 2 to switch the flow path of the exhaust gas flow.
a and 7b are provided.

An atmospheric air introduction pipe 8 for introducing atmospheric air into the trap 3 is connected to the exhaust passage 2 between the trap 3 and the flow path switching valve 7a on the upstream side of the trap 3, and the atmospheric air introduction pipe 8 can be used to open or close the pipe. An electromagnetic valve 9 for supplying air and a pump 10 for supplying atmospheric air are provided.
Further, a muffler 11 is connected to the exhaust passage 2 on the downstream side of the trap 3, and the confluence section 6 of the bypass passage 4 is connected to the upstream side of the muffler 11. A bypass passage 12 for the silencer 11 section is formed in the exhaust passage 2 by connecting the upstream side of the flow path switching valve 7b of the merging section 6 and the downstream side of the silencer 11. A solenoid valve 13 is provided upstream of the flow path 12 to open and close the flow path.

An electric heater 14 is attached to the upstream end surface 3a of the trap 3 to heat it, and the trap 3 is further equipped with a temperature sensor 15a for detecting the internal inlet temperature and outlet temperature.
15b is provided.

Further, the passage switching valves 7a, 7b, the electromagnetic valves 9, 13, the pump 10, and the electric heater 14 are connected to an electronic control device 16 so that their operations are controlled. Signals from the temperature sensors 15a and 15b described above and a signal from an engine speed sensor 18 provided in the fuel injection pump 17 of the internal combustion engine 1 are input to the electronic control device 16. is the engine speed sensor 1
The regeneration timing (reburning timing) of the trap is determined by integrating the signals from the temperature sensors 15a,
In response to the signal from 15b, the passage switching valve 7
a, 7b, solenoid valves 9, 13, pump 10, electric heater 14, etc.
That is, when the electronic control unit 16 determines that it is time to regenerate the trap 3, it operates the flow path switching valves 7a and 7b to allow all of the exhaust gas flow from the internal combustion engine 1 to flow to the bypass passage 4 side, and also to the electric heater 14. A large current is passed through the trap 3 to accelerate the temperature rise rate at the initial stage of heating, and when the inlet temperature of the trap 3 reaches a re-burning temperature T1 _or higher, the electric heater 14
Normal heating is performed by reducing the energization value. During this transition to normal heating, when the inlet temperature of the trap 3 reaches a predetermined temperature _T2 which is higher than the temperature _T1 ,
The solenoid valve 9 of the atmosphere introduction pipe 8 is opened to supply air (atmosphere) for re-combustion to the trap 3.

Next, the operation of the present invention will be explained based on the flowchart shown in FIG.

First, during normal driving, the bypass passage 4 of the trap 3 portion of the exhaust passage 2 is closed to the flow path switching valves 7a, 7.
b, and is closed by the solenoid valve 9 of the atmosphere introduction pipe 8 and the bypass passage 12 of the silencer 11 part.
The solenoid valve 13 of the internal combustion engine 1 is also closed, and all of the exhaust gas from the internal combustion engine 1 passes through the trap 3 and is discharged to the outside, and the particulates contained in the exhaust gas adhere to and accumulate on the trap 3. collected (see Figure 1).

On the other hand, at this time, the electronic control unit 16 is integrating the input signal from the rotation speed sensor 18, and depending on whether the integrated value exceeds a certain value, the trap 3 is activated.
It is determined whether the time has come to incinerate the collected exhaust particles (time to regenerate trap 3).

When it is determined that the regeneration time has come, the flow path switching valves 7a and 7b are operated to open the bypass passage 4 and close the exhaust passage 2 of the trap 3, allowing all of the exhaust gas to flow to the bypass passage 4 side. At the same time, a large current is passed through the electric heater 14 to rapidly heat the trap 3 (see FIG. 2). Next, trap 3
The temperature on the inlet side _of
The trap 3 is rapidly heated by continuing to supply a large current to the electric heater 14 until reaching _T1 . When the temperature on the inlet side exceeds _T1 , the current applied to the electric heater 14 is reduced to perform normal heating.

After that, the inlet side temperature rises further and reaches the set temperature.
When T ₂ is reached, the solenoid valve 9 of the atmosphere introduction pipe 8 is opened (ON), and the pump 10 is activated (ON) to send combustion air (atmosphere) into the trap 3.
Initiates re-burning of exhaust particulates.

After that, the temperature at the exit side of the trap 3 is detected by the temperature sensor 15b, and while confirming that the temperature is below the melting danger temperature _T3 of the trap 3, the electric heater 14 is continued to be energized. When the time exceeds the set time, the electric heater 14 is turned off (OFF) and atmospheric air continues to be introduced into the trap 3.
When the air introduction time exceeds the set time, the pump 10 is stopped, the electromagnetic valve 9 of the air introduction pipe 8 is closed, and the bypass passage 4 of the trap 3 and the bypass passage 12 of the silencer 11 are closed. Then, the regeneration of the trap 3 is completed and the normal driving state is restored. In addition, if the outlet temperature of the trap 3 exceeds the melting danger temperature _T3 while the electric heater 14 is being energized (during normal heating), the electric heater 14 is immediately turned off and the trap is closed. The regeneration of the trap 3 is completed to prevent the trap 3 from being melted and damaged.

The graph in FIG. 4 shows the control during regeneration of the trap 3 as a function of time and temperature. That is, when it is time to regenerate the trap 3, no exhaust gas flows into the trap 3, and in order to shorten the re-burning time of the trap 3, the temperature at the inlet side of the trap 3 changes to the collected exhaust gas. A large current is applied to rapidly heat the trap 3 until the temperature reaches _T1 , which allows the re-combustion of particulates, and the temperature rise is accelerated.

And if the inlet side temperature reaches T ₁ ,
The energization value to the electric heater 14 is decreased, and the energization setting current value at the time of the decrease is set to a value that allows the temperature of the electric heater 14 to stably continue the re-burning of exhaust particulates, and the trap 3 is normally set. Heat. While the temperature of the electric heater 14 falls to the normal heating temperature, the temperature on the inlet side of the trap 3 reaches the set temperature.
At _T2 , the electromagnetic valve 9 and pump 10 of the atmosphere introduction pipe 8 are operated to introduce combustion air into the trap 3, thereby starting re-combustion of the exhaust particulates. The reason for waiting to introduce air until the set temperature _T2 is reached is that even if the temperature of trap 3 drops immediately after introducing air, that temperature remains the temperature at which exhaust particulates can be re-burned (T1 ₎ .
This is to prevent the temperature from becoming below T1, and to ensure the combustion by starting re-combustion after the average temperature of the entire trap 3 reaches T1 _or higher. Furthermore, the reason why the rapid heating by the electric heater 14 is stopped before introducing the atmosphere is to prevent the trap 3 from being partially melted and damaged due to sudden re-combustion occurring at the same time as the introduction of the atmosphere.

Further, the normal heating time of the electric heater 14 is set to the shortest time in which the re-combustion of the exhaust particulates is stabilized, thereby reducing the power consumption, and the time of introduction into the atmosphere is set to ensure that the collected exhaust particulates are sufficiently absorbed. This is set to the shortest time for complete combustion, and the amount of atmospheric air introduced at that time is set to a small amount that does not cause the temperature at the time of re-burning to rise to the melting danger temperature T3 of the trap ₃ .

Therefore, as is clear from the above explanation, the exhaust gas purification device for an internal combustion engine of the present invention uses the electric heater 14 to recycle exhaust particulates that cannot be sufficiently reburned and removed even if a catalyst or fuel additive is used. Make it combustible. In the early stages of heating with the electric heater 14, a large current is supplied to accelerate the rate of temperature rise of the trap 3 and the exhaust gas in the trap, and at this time, the trap 3 is closed to prevent the introduction of combustion atmosphere. Heat loss is suppressed, and after reaching the re-combustion temperature, the energization value to the electric heater 14 is reduced to heat the small amount of air introduced, thereby preventing power wastage. Therefore, the electric heater 14 can incinerate and remove the exhaust particulates collected in the trap 3 by reducing power consumption as much as possible, and the re-burning time is also shortened, during which time the exhaust particles are released into the atmosphere by the exhaust bypass. This makes it possible to reduce the amount of exhaust particulates that are emitted as much as possible.

[Effects of the invention] In summary, the present invention provides the following excellent effects.

(1) When regenerating the trap by reburning the trap, a large current is supplied to the trap at the initial stage of heating by the electric heater to rapidly heat the trap, so that the temperature of the trap can be quickly raised to the temperature at which exhaust particulates can be reburned. This can shorten the reburning time.

(2) Exhaust gas is bypassed during trap regeneration, and atmospheric air is not introduced during rapid heating, so heat loss can be suppressed and unnecessary power consumption can be prevented.

(3) When the temperature on the inlet side of the trap reaches the temperature at which exhaust particulates can be re-combusted due to rapid heating of the trap, normal heating is performed by reducing the energization value to the heater, and during this transition to normal heating, the temperature on the inlet side of the trap increases. When the temperature reaches a predetermined temperature that is higher than the re-combustion temperature, combustion air is introduced into the trap to start re-combustion, thereby preventing rapid re-combustion of exhaust particulates and partially dissolving the trap. losses can be prevented.

(4) By starting re-combustion when the temperature on the inlet side of the trap reaches a predetermined temperature above the re-combustion temperature, even if the trap temperature drops immediately after air is introduced, the temperature remains below the re-combustion temperature. can be prevented from becoming

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a preferred embodiment of the exhaust purification device for an internal combustion engine according to the present invention, and FIG.
FIG. 3 is a flowchart of the exhaust gas purification device of the present invention, and FIG. 4 is a graph for explaining the operation of the present invention. In the figure, 1 is an internal combustion engine, 2 is an exhaust passage, 3 is a trap, 4 is a bypass passage of the trap, 7a is a flow path switching valve, 8 is an atmosphere introduction pipe, 9 is a solenoid valve, 14
is an electric heater, 15a and 15b are temperature sensors, 1
6 is an electronic control device.

Claims (1)

[Scope of utility model registration request] A trap installed in the exhaust passage of an internal combustion engine,
an electric heater for heating the trap, a means for supplying combustion air to the trap, a passage for bypassing the trap, a passage switching valve for switching the passage to either the bypass passage or the exhaust passage; At each time, the flow path switching valve is switched to the bypass passage open side, and a large current is supplied to the heater to rapidly heat the trap. When the temperature on the inlet side of the trap reaches a temperature at which exhaust particulates can be re-burned, the heater is turned off. a control device that performs normal heating by reducing the energization value to the air supply means, and controls the operation of the air supply means when the inlet side temperature reaches a predetermined temperature higher than the re-combustion temperature during the transition to normal heating. Engine exhaust purification device.