JPH0427886B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a particulate collection device that collects particulates contained in the exhaust gas of an engine, and in particular, to a particulate matter collection device that collects particulates contained in the exhaust gas of an engine, and in particular, a particulate matter collection device in which particulates collected in a filter are ignited and burned by a heater. This invention relates to a particulate collection device in which the filter can be reused.

[Background technology]

Diesel engines may contain particulates in their exhaust. These fine particles are generated due to incomplete combustion of fuel, are made of carbon, hydrocarbons, metals, etc., and are flammable.

When the exhaust gas containing the fine particles is directly discharged from the vehicle, the exhaust gas becomes black smoke-like and is accompanied by an unpleasant odor.

Therefore, it is inconvenient to discharge such exhaust gas directly from the engine in terms of maintaining a clean and comfortable environment.

In this type of device, particulates contained in the exhaust gas are collected by a filter to purify the exhaust gas.

Furthermore, at a predetermined time before a predetermined amount of particles are collected and accumulated in the filter and the output of the engine is reduced, the most upstream collected particles are ignited by the heater. Then, the ignited particulates become a spark, and the downstream collected particulates self-combust due to the oxygen in the exhaust gas. This combustion completes the regeneration of the filter, making it possible to collect particulates again.

In conventional devices of this type, when a predetermined amount of particles are collected and accumulated in the filter and a predetermined time elapses before the engine output decreases, the captured particles are immediately ignited by the heater and filter regeneration is started. was.

Therefore, in the prior art, combustion of particulates collected by the filter may start before the trap is warmed up, and thermal stress is generated in the trap. As a result, there were problems in that the trap was damaged or its durability was reduced.

In addition, if current is supplied to the heater when the headlamp is on and the engine is running at low speed, the battery condition will worsen and the current value supplied to the headlamp will change, resulting in a decrease in headlamp brightness and flickering. It was hot.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to provide a particulate collection method that does not cause damage to the trap or decrease its durability, and can prevent a decrease in illuminance and flickering of the headlamp. The goal is to provide equipment.

[Summary of the invention]

In order to achieve the above object, the present invention provides a trap that includes a filter that collects particulates contained in engine exhaust gas, a heater that ignites the particulates collected by the filter, and a temperature sensor that detects the temperature of the trap. means, headlamp lighting detection means, engine rotation speed detection means, and a power supply circuit that supplies ignition current to the heater when the temperature of the trap exceeds a predetermined value, and the power supply circuit detects the engine rotation when the headlamp is lit. When the number of rotations is lower than a predetermined rotation speed, the predetermined supply current value to the heater is lowered, and the supply of current to the heater gradually increases the current value, and when the supply of current to the heater is stopped, the current value is gradually decreased. It is characterized by

[Embodiments of the invention]

Embodiments of the apparatus according to the present invention will be described below based on the drawings.

FIG. 1 shows the overall configuration of the apparatus of this embodiment.

In the figure, an intake throttle valve 12 is provided on the intake side of a diesel engine 10, and the intake throttle valve 12 is driven by an actuator 14. Further, a fuel injection valve 16 for controlling the amount of fuel injected into the diesel engine 10 is provided, and an EGR valve 18 for recirculating exhaust gas to the intake side is provided between the intake and exhaust.

A trap 20 is provided in the exhaust path of the diesel engine 10.

The casing 22 of this trap 20 is formed in the shape of a column with a substantially elliptical cross section with narrowed ends. This casing 22 is filled with a filter 24 . The filter 24 can collect particulate matter (particulate matter) contained in the exhaust column of the diesel engine 10.
4. Gradually accumulates from the exhaust inlet to the outlet. Further, within the casing 22, a heater 26 is provided on the end surface of the filter 24 on the diesel engine 10 side for igniting the particulates collected by the filter 24.

Note that the filter 24 of this embodiment is made of foamed ceramic, and has a three-dimensional network structure skeleton having a large number of elliptical holes communicating with each other.

Further, the heater 26 of this embodiment has heating wires 30-1, 30-2, 30-3, 30- connected to terminals 28-1, 28-2, as shown in FIG.
4, 30-5, 30-6, 30-7, 30-8. Note that the heater 26 is grounded to the vehicle body.

An ignition current is supplied to the heater 26 from a power supply circuit, and the power supply circuit is comprised of a chopper circuit 32 and an ECU 34 in FIG. The capacitor circuit 32 constitutes a main power supply circuit and consists of switching transistors 38 and 40 that cap the output current of the battery 36, and its capping operation is controlled by an ECU 34 mainly composed of a microcomputer.

Furthermore, in FIG. 1, an exhaust passage 42 is formed bypassing the trap 20, and this exhaust passage 42 is provided with an exhaust amount regulating valve 44. This exhaust flow rate control valve 44 is driven to open and close by a diaphragm 46, and the diaphragm 46
48 and 50. and VSV
48 is connected to a vacuum pump (not shown), and VSV50 is open to the atmosphere.
Both are controlled by the ECU 34. As mentioned above, the ECU 34 is the diesel engine 1
0, the heater 26 and the exhaust flow rate control valve 44 are controlled, but in order to control them,
Various detection signals are supplied to the ECU 34.

In FIG. 1, the opening of the intake throttle valve 12 is determined by an opening sensor 52, the intake side pressure of the diesel engine 10 is determined by a pressure sensor 54, the engine water temperature is determined by a temperature sensor 56, and the engine load is determined by a load sensor 58. Detected.

Further, the rotational speed of the diesel engine 10 is detected by a rotational speed sensor 60 serving as engine rotational speed detection means, the vehicle speed is detected by a vehicle speed sensor 62, and the oxygen concentration in exhaust gas is detected by an O ₂ sensor 64.

Furthermore, diesel engine 10 to trap 20
The temperature of the exhaust gas discharged to the exhaust gas is detected by a temperature sensor 66, and the pressure thereof is detected by a pressure sensor 68. The presence or absence of operation of a light control switch 70 for turning on and off the headlight is detected by an operation sensor 72 serving as headlamp lighting detection means.

The ECU 34 includes the above opening sensor 52, pressure sensor 54, temperature sensor 56, load sensor 58, rotation speed sensor 60, vehicle speed sensor 62, O ₂ sensor 64,
Temperature sensor 66, pressure sensor 68, operation sensor 7
Diesel engine 1 based on various detection signals of 2.
It is configured to be able to perform the following controls.

The ECU 34 can control the chopper circuit 32 so that the chopper circuit 32 supplies ignition current to the heater 26 when the pressure loss of the filter 24 exceeds a predetermined value.

In this embodiment, this control is carried out by the load sensor 58,
This is performed based on detection signals from the rotation speed sensor 60 and the pressure sensor 68.

The characteristic P shown in FIG. 3 is stored in the ROM of the ECU 34, and in the figure, the horizontal axis represents the detected engine rotational speed value N, and the vertical axis represents the detected engine load value. ECU34 is load sensor 5
8. Determine the exhaust pressure reference value PO from the detection signal of the rotation speed sensor 60 using the characteristic P, and when the detection value of the pressure sensor 68 exceeds this reference value PO, the chopper circuit 32 applies ignition current to the heater 26. It is possible to control the chapper circuit 32 so as to supply

The ECU 34 can also control the chopper circuit 32 to prohibit the supply of ignition current to the heater 26 until the trap 20 is warmed by exhaust gas, and to start supplying the ignition current for the first time when the trap 20 is warmed up.

This control includes a temperature sensor 66 and a temperature sensor 5.
The ECU 34 uses the detection signal of the temperature sensor 66 to confirm that a predetermined time has elapsed after the start of the diesel engine 10 and the temperature of the exhaust gas supplied to the trap 20 has exceeded a predetermined value. Then, when it is confirmed that the engine coolant temperature has exceeded the specified value, trap 2 is activated.
It is possible to control the start of the supply of ignition current to the heater 26 by determining that the heater 26 has warmed up.

In addition, when controlling the start of the ignition current to the heater 26, the ECU 34 checks in advance that the cumulative value of the vehicle speed and the cumulative value of the engine rotation speed (for example, 200,000 revolutions) each exceed a predetermined value and the pressure sensor 68 does not malfunction. You can check it.

Then, the ECU 34 controls the flow rate of the exhaust gas flowing through the trap 20 by adjusting the opening degree of the exhaust flow rate control valve 44 so that the collected particulates ignited by the heater 26 are properly combusted.

At this time, the ECU 34 also controls the exhaust flow rate control valve 4 according to the detection signals of the O ₂ sensor 64 and the temperature sensor 66.
By adjusting the opening degree in step 4, it is possible to reduce the flow velocity of the exhaust gas flowing through the trap 20 and prevent the trap 20 from melting.

Further, the ECU 34 controls the value of the ignition current so that the value correlates with the power supply voltage when the headlamp is turned on.

In this embodiment, since the output voltage of the battery 36 depends on the engine rotation speed, the value of the ignition current supplied to the heater 26 is controlled according to the detection signal of the rotation speed sensor 60, that is, the engine rotation speed. That is, when the engine speed is low, the duty ratio D of the ignition current is decreased and its value is reduced, and when the engine speed is high, the duty ratio D is increased and its value is increased. At this time, the value of the ignition current is controlled by the duty ratio D according to the characteristic 100 in FIG. As a result, the output voltage of the battery 36 is controlled to be substantially constant.

Further, the ECU 34 can gradually increase or decrease the value of the ignition current to the heater 26 when the headlamp is turned on.

The ECU 34 of this embodiment detects the lighting state of the head lamp based on the detection signal of the operation sensor 72, and gradually controls the duty ratio D of the ignition current to increase or decrease over time as shown by the characteristic 102 in FIG. ing. Furthermore, ECU34 is heating wire 30
-1,30-2,30-3,30-4,30-
5, 30-6, 30-7, 30-8 are energized one by one in the prescribed order, and the last heating wire 3
The switching transistors 38 and 40 of the chopper circuit 32 can be duty-controlled so that the value of the ignition current is gradually reduced when the ignition current is de-energized.

The present embodiment has the above configuration, and its operation will be explained below.

FIG. 6 shows a main routine explaining the entire processing of the ECU 34, in which processing including control processing of the diesel engine 10 (step 200) and regeneration processing of the trap 20 are repeatedly performed.

In step 200, the basic injection amount and injection timing of fuel are first determined based on the amount of depression of the accelerator pedal, that is, the lever opening of the injection pump and the engine speed. The basic injection amount and injection timing are corrected based on the engine coolant temperature, intake air temperature, etc., and the output of the diesel engine 10 is controlled using these corrections.

During operation of the diesel engine 10, the exhaust flow rate control valve 44 is closed and the exhaust gas is guided to the trap 20 side, so that the particulates contained in the exhaust gas gradually move from the upstream surface of the filter 24 to the downstream direction. Collected in the filter 24, the filter 24
is accumulated in

As a result, clean gas containing no particulates is emitted from the vehicle, thereby preventing any negative impact on the surrounding environment.

In step 202, the process shown in FIG. 7 is first performed.

In the process shown in FIG. 7, it is determined whether a predetermined amount of particles have been collected by the filter 24 in the following manner.

In FIG. 7, the ECU 34 uses the characteristic P shown in FIG. 3 from the detection signals of the load sensor 58 and the rotation speed sensor 60 to determine whether the pressure loss of the filter 24 exceeds a predetermined value. ₀ is determined, and it is determined whether the detected value of the pressure sensor 68 exceeds this reference value _P0 (step 300).

At this time, the detected value of the pressure sensor 68 is the reference value P ₀
When it is determined that the pressure loss of the filter 24 has exceeded the predetermined value, a predetermined amount of particulates have been collected in the filter 24, and the diesel engine 1
0 power loss has increased to a certain extent.

Next, the ECU 34 is the diesel engine 10
It is determined whether the integrated rotational speed value and the integrated vehicle speed value each exceed a set value (steps 302 and 304).

If it is determined in step 302 that the cumulative rotational speed of the diesel engine 10 does not exceed the set value, the determination in step 300 is made, and if it is determined in step 304 that the cumulative vehicle speed does not exceed the set value, the determination is made in step 300. , 302 are each temporarily invalidated.

In step 306, the determinations in steps 300 and 302 that were invalidated in steps 302 and 304 are examined. Note that it is preferable to omit steps 302, 304, and 306 if the reference value _P0 used in step 300 is not destroyed and there is no risk that the integrated values used in steps 302 and 304 will be volatile. It is also possible to perform only one of steps 300, 302, and 304 and omit the other steps.

When it is detected that a certain amount of particulates have accumulated in the filter 24 in this way, if the collection of particulates continues, the loss on the exhaust side will increase and the output of the diesel engine 10 will decrease. The fine particles collected by the filter 24 are ignited and burned by the heater 26 in the following manner.

In this device, the supply of ignition current to the heater 26 is inhibited until the trap 20 is warmed by the exhaust air, and only then is started.

In FIG. 8, first the diesel engine 10
It is confirmed that the exhaust system has been warmed up after a predetermined period of time has elapsed since the engine was started (step 400).

Next, diesel engine 10 in trap 20
It is confirmed by the detection signal of the temperature sensor 66 that the temperature of the exhaust gas discharged from the exhaust gas is higher than a predetermined temperature (step 402).

Furthermore, the cooling water temperature of diesel engine 10 is 60
℃ or above is confirmed by the detection signal of the temperature sensor 56 (step 404).

In this way, in this embodiment, the diesel engine 1
It is determined that the trap 20 has been warmed up when a predetermined period of time has elapsed since the start of the zero operation, the temperature of the exhaust gas has exceeded a predetermined temperature, and the temperature of the cooling water has exceeded 60°C. The ignition combustion process of the collected particulates is started (step 406).

Note that a temperature sensor that directly detects the temperature of the trap 20 or the temperature of the exhaust system may be provided, and the detection signal may be used to confirm that the trap 20 has been warmed.

As described above, in this embodiment, combustion of the particulates collected by the filter 24 is started after the trap 20 is warmed up, so thermal stress is prevented from occurring in the casing 22 and the filter 24, and Corruption is avoided.

Next, the process of step 406 will be explained.

In FIG. 9, the process at step 406 is divided into a process for controlling the ignition of the particulates collected by the filter 24 (step 500) and a process for controlling the opening of the exhaust flow rate control valve 44 (step 502). ,
Both processes are started at the same time.

FIG. 10 shows the ignition process at step 500, in which it is first determined whether the headlamp is lit or not based on the detection signal of the operation sensor 72 (step 500).
600).

If it is determined that the head lamp is on, the rotation speed sensor 6 detects whether the rotation speed of the diesel engine 10 is high or low.
Determination is made based on a detection signal of 0. In this embodiment, when the rotation speed of the diesel engine 10 is 1000 rpm or more, it is determined that it is high, and when it is less than 1000 rpm, it is determined that it is low (step
602).

Further, when it is determined in step 600 that the headlight is not on, the duty ratio of the ignition current supplied to the heater 26 is set to a large value (step 604), and it is determined that the engine speed is high when the headlight is on. When the engine speed is low, the ignition current duty ratio is set to a medium value (step 606), and when it is determined that the engine speed is low when the headlights are on, the ignition current duty ratio is set to a small value (step 606).
608).

Thereafter, the supply of ignition current with the duty ratio set as described above is started (step
610, 612).

When the supply of the ignition current with the duty ratio set in steps 606 and 608 is started, the duty ratio is gradually increased as shown in FIG. 5, and each heating wire 30-1, 30-
2, 30-3, 30-4, 30-5, 30-6,
30-7, 30-8 are ignited in a predetermined order (step 614).

At this time, the ignition time of the heater 26 is monitored, and when it is determined that a predetermined time has elapsed (step 616), the ignition of the heater 26 is terminated (step 608). In addition, when the ignition of this heater 26 is completed, each heating wire 30-1, 30-2, 30-3,
30-4, 30-5, 30-6, 30-7, 30
-8, the duty ratio of the ignition current supplied to the last heating wire 30 is gradually reduced as shown in FIG.

Next, the valve control process performed in step 502 in FIG. 9 will be explained.

The fine particles collected by the filter 24 are transferred to the heater 26
When the trap 2 is ignited, the exhaust flow rate control valve 44 provided in the exhaust passage 42 is temporarily opened and most of the exhaust gas is flowed into the exhaust passage 42, and the trap 2 is ignited.
The amount of exhaust gas that flows to zero is limited.

As a result, the flow velocity of the exhaust gas flowing into the trap 20 is reduced, and the particulates collected in the filter 24 are smoothly ignited and burned.

Furthermore, under a predetermined exhaust temperature condition where the oxygen concentration in the exhaust becomes high, the exhaust flow rate control valve 44 is forcibly controlled to open. This control is performed for the following reason.

If high-load operation such as steep hill climbing or high-speed driving is performed continuously with a sufficient amount of particulates collected in the filter 24, the exhaust temperature will become considerably high, and the oxygen concentration in the exhaust will decrease. It is small because the amount of fuel injected is large.

If the accelerator pedal is opened or opened halfway during this high-load operation, the oxygen concentration in the exhaust gas will rapidly increase because a large amount of air is being supplied to the diesel engine 10.

Therefore, a large amount of oxygen is supplied to an area where the exhaust gas temperature is considerably high, so that the ignited collected particles are rapidly combusted.

As a result, there is a risk that the filter 24 will become hot and the trap 20 will melt.

For this reason, in this embodiment, when the oxygen concentration in the exhaust gas increases under exhaust temperature conditions where the exhaust gas is at a considerably high temperature, the valve 44 is forcibly opened and the amount of exhaust gas flowing through the trap 20 is reduced. Ru. Note that the temperature of the exhaust gas is detected from the detection signal of the temperature sensor 66, and the oxygen concentration is detected from the detection signal of the O ₂ sensor 64.

By carrying out the above ignition process (step 500) and valve control process (step 502), the part of the particulates collected and accumulated in the filter 24 at the most upstream side of the exhaust gas is ignited.

Since the collected particulates are flammable and sufficient oxygen is contained in the exhaust gas, the ignited collected particulates serve as a ignition source, and the combustion of the collected particulates progresses toward the downstream of the exhaust gas.

When this combustion is completed, the filter 24 is free of residual particulate matter, so that the pressure loss in the trap 20 is reduced to the initial loss. That is, the trap 20 is regenerated and can be reused.

As explained above, according to this embodiment, when a predetermined amount of particles are accumulated in the filter 24 and the pressure loss thereof exceeds a predetermined value, the collected particles are ignited, and the collected particles and the pressure loss are Since the values correspond almost exactly, it is possible to regenerate the trap 20 at an optimal time.

On the other hand, if the regeneration timing of the trap 20 is determined solely based on the cumulative engine speed, vehicle mileage, cumulative engine operating time, etc., the amount of particulates collected may vary due to differences in driving conditions, etc. At different times, a large amount of fine particles may accumulate during the regeneration period, and if the collected fine particles are ignited at this time, the temperature of the trap 20 will rise abnormally. As a result, the trap 20 may be damaged or its durability may be reduced.

As described above, according to this embodiment, the trap 20 is regenerated at an optimal time, so that damage to the trap 20 can be prevented or its durability can be improved.

In this embodiment, the pressure loss was detected by the electrical pressure sensor 68, but a conduit is formed between the upstream side and the downstream side of the trap 20, and the trap 20 is placed in this conduit. It is also possible to reduce costs by providing a mechanical switch such as a diaphragm that is activated when the pressure difference between the upstream side and the downstream side reaches a predetermined value, and using this instead of the pressure sensor 68. It is suitable from this point of view.

Further, according to this embodiment, after it is confirmed that the trap 20 has warmed up, the filter 24
Since the fine particles trapped in the trap 20 are ignited, a large temperature difference is prevented from occurring in the trap 20 portion. Therefore, it is possible to avoid the inconvenience of damage to the trap 20 and the like due to thermal stress due to this temperature difference, and it is therefore possible to improve the durability of the device.

Furthermore, according to this embodiment, when the trap 20 is regenerated when the headlamp is turned on, an ignition current with a duty ratio correlated to the output voltage of the battery 36 is supplied to the heater 26.
This prevents a decrease in the illuminance of the headlamp. For this reason, when driving at night, etc., the trap 2
Even if the zero regeneration process is started, good driving visibility is ensured, and therefore safe driving is possible. It is also preferable to configure the device so that a voltmeter is provided to detect the output voltage of the battery 36 and the duty ratio of the ignition current is controlled in accordance with the detection signal.

According to this embodiment, when the trap 20 is regenerated and the ignition current to the heater 26 is suddenly increased or decreased, such as when the heater 26 is turned on or off, the increase or decrease is done gradually, so that the headlamp is turned on. There is no sudden change in the supply voltage to the Therefore, even if the regeneration of the trap 20 starts or ends when the headlamp is turned on, the driver will not see any flickering of the headlamp light. Therefore, the driver does not feel anxious about the vehicle.

Further, according to the present embodiment, even if the oxygen concentration in the exhaust gas increases when the exhaust gas is under a predetermined exhaust temperature condition in which the exhaust gas is at a high temperature, the valve 44 is forcibly opened and the exhaust gas flows to the trap 20. Since the amount of particles trapped in the trap 20 is limited, abnormal combustion of the particulates collected in the trap 20 can be prevented. Therefore, the trap 20 can be prevented from melting and damage, and the reliability of the device can be improved.

〔Effect of the invention〕

As explained above, according to the present invention, the collected fine particles are ignited after it is confirmed that the trap has warmed up, thereby preventing a large temperature difference from occurring in the trap portion. Therefore, the trap etc. will not be damaged or its durability will not be reduced due to thermal stress caused by this temperature difference, and therefore it is possible to improve the reliability of the device. Furthermore, when the headlamp is on and the engine speed is lower than a predetermined speed, the predetermined value of the current supplied to the heater is lowered, thereby preventing a drop in the illuminance of the headlamp, and the supply of current to the heater gradually increases the current value. Stopping the supply of current to the heater gradually reduces the current value, which has the excellent effect of preventing flickering of the headlamp.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the overall configuration of the device according to the present invention;
FIG. 2 is an explanatory diagram of the configuration of the heater in FIG. 1, FIG. 3 is an explanatory diagram of the characteristics of the exhaust pressure reference value, and FIG. 4 is a characteristic diagram showing the relationship between the ignition current and its duty ratio.
Fig. 5 is an explanatory diagram of the control characteristics of the duty ratio with respect to elapsed time, and Figs. 6, 7, 8, 9, and 10 are flowcharts explaining the control operation of the ECU in Fig. 1. be. 10... Diesel engine, 20... Trap, 24... Filter, 26... Heater, 32...
...Chiyotsupa circuit, 34...ECU, 56, 66...
...Temperature sensor, 60... Rotation speed sensor (engine rotation speed detection means), 72... Operation sensor (head lamp lighting detection means).

Claims (1)

[Claims] 1 A trap including a filter that collects particulates contained in engine exhaust gas and a heater that ignites the particulates collected by the filter, temperature detection means for detecting the temperature of the trap, headlamp lighting detection means, and an engine. It is equipped with a rotation speed detection means and a power supply circuit that supplies ignition current to the heater when the temperature of the trap exceeds a predetermined value. A particulate collection device characterized in that a predetermined current value supplied to the heater is lowered, the current value is gradually increased when the current is supplied to the heater, and the current value is gradually decreased when the current supply to the heater is stopped.