JPH04101010A - Exhaust fine particle eliminating device for diesel engine - Google Patents

Abstract

PURPOSE:To avoid a half flameout condition of burning, while operating regeneration process without casing closing trouble of an exhaust valve, by adjusting a throttle rate of a throttle valve provided on an exhaust passage side so as to hold exhaust pressure at a constant rate on the upside stream side from the throttle valve provided on the exhaust passage side, at the time of regeneration of a filter. CONSTITUTION:On the basis of a regeneration command of a filter 7, electrification is carried out in a heater 8 by a controller 31 to heat air supplied from an intake passage 3 to an engine 1 through branch intake passage, so as to promote temperature increase of exhaust gas. A fuel injection pump 2 is controlled by the controller 31, so that the number of revolution of the engine 1 is set to a high idling number of revolution to increase an amount of exhaust gas supplied to an exhaust passage 6. A vacuum control valve 19 is driven by the controller 31 to make air suction force of a vacuum pump 22 act on respective air flow passages 20, 21. Namely, regenerating process is carried out by increasing exhaust pressure in the exhaust passage 6 by respective throttle valves 9, 10. When exhaust pressure is increased, for example, up to a level which exceeds the force of spring 28, the air flow passage 21 is shut out by an exhaust pressure control valve 26 so as to decrease the throttle amount of the throttle valve 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an apparatus for removing combustible exhaust particulates such as carbon contained in the exhaust gas of a diesel engine.

(Prior art) Engine exhaust gas, especially diesel engine exhaust gas, contains combustible exhaust particulates (particulates) such as carbon. A filter is provided to collect the above-mentioned exhaust particulates and prevent them from being discharged to the outside. It is necessary to clean or regenerate the filter by removing the trapped exhaust particulates at a point where there is a risk of clogging or clogging.

Therefore, for example, Japanese Utility Model Application Publication No. 61-173712 discloses an exhaust system in which combustible substances are injected into a filter provided in the exhaust passage, and the combustible substances are collected in the filter using the temperature of the exhaust gas. By burning all the fine particles,
A regeneration treatment technique is disclosed that prevents filter clogging.

According to this regeneration processing technology, exhaust particulates collected in the filter can be removed by injection of combustible material and combustion using the temperature of the exhaust gas, making it possible to regenerate the filter without using large-scale measures. Become.

(Problems to be Solved by the Invention) By the way, when exhaust particulates are removed by combustion using the above exhaust gas, the removal efficiency naturally improves as the temperature of the exhaust gas increases. For this reason, throttle valves are provided downstream of the filter in the exhaust passage and in the intake passage, and these throttle valves are used to throttle each passage during the above-mentioned filter regeneration process, thereby reducing the pressure of the exhaust gas (hereinafter referred to as exhaust pressure). )
It is conceivable that this could increase the temperature and encourage a rise in temperature. Furthermore, if the temperature of the exhaust gas can be effectively raised by this method, the injection of combustibles described in the above-mentioned publication can be eliminated, and exhaust particulates can be combusted only by the heat of the exhaust gas.

However, in a structure in which throttle valves are provided on the exhaust passage side and intake passage side as described above, the operation timing of each throttle valve during filter regeneration processing is different from the case where the exhaust passage side throttle valve is throttled first. As a result, even if the exhaust pressure in the exhaust passage increases once, the intake air amount of the engine decreases due to the subsequent operation of the throttle valve on the intake passage side, and the exhaust pressure decreases again by that amount. The amount of throttling by the side throttle valve must be determined by adding the exhaust pressure drop due to the subsequent operation of the intake passage side throttle valve to the exhaust pressure value required for the regeneration process. If the amount of throttling is too large, the exhaust pressure immediately after the exhaust passage side throttle valve is activated becomes extremely high, which causes a problem in the closing operation of the exhaust valve of the cylinder in the engine. Therefore, it is conceivable to operate the throttle valve on the intake passage side first, but in this case, there is a risk that the intake air amount of the engine will be insufficient and the combustion will be in a half-misfire state.

SUMMARY OF THE INVENTION Accordingly, the present invention aims to provide a diesel engine in which regeneration processing can be performed without causing any trouble in closing the exhaust valve while avoiding a half-misfire state of combustion by throttling the exhaust passage throttle valve before the intake passage throttle valve. The objective is to provide an exhaust particulate removal device.

(Means for Solving the Problems) That is, the present invention provides an exhaust particulate removal device for a diesel engine that is equipped with a filter for collecting combustible exhaust particulates in the exhaust passage. Throttle valve driving means is provided for operating the throttle valve on the exhaust passage side in the throttle direction, and then operates the throttle valve on the intake passage side in the throttle direction, during filter regeneration. Exhaust pressure control means detects the magnitude of exhaust pressure upstream of the throttle valve and adjusts the degree of throttling of the throttle valve so that the exhaust pressure reaches a predetermined pressure set during filter regeneration. It is characterized by being

(Function) According to the above configuration, when the filter is regenerated, the magnitude of the exhaust pressure upstream of the exhaust passage side throttle valve is detected, and the exhaust passage side throttle valve is adjusted so that this exhaust pressure is constant. Since exhaust pressure control means for adjusting the amount of throttling is provided, the exhaust pressure that has once risen to a predetermined value by operating the exhaust passage throttle valve in the throttle direction is then adjusted in the throttle direction of the intake passage throttle valve. Even if the exhaust pressure attempts to decrease again due to the operation of
To prevent the exhaust pressure in the exhaust passage from decreasing from a predetermined value. Further, when the exhaust pressure is about to rise further from a predetermined value, the exhaust pressure control means reduces the throttle amount of the exhaust passage side throttle valve to prevent the exhaust pressure from rising. As a result, the exhaust pressure during filter regeneration processing is kept constant, and problems with the closing operation of the engine's exhaust valve due to an abnormal increase in exhaust pressure can be avoided, and the exhaust pressure in the exhaust passage can be increased to an appropriate value. The temperature of the exhaust gas is effectively increased, ensuring combustion of the exhaust particulates trapped in the filter.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an exhaust particulate removal device for a four-cylinder diesel engine 1, and the engine 1 is equipped with a fuel injection pump 2 for feeding fuel into the combustion chambers of each cylinder A to A. Further, branch intake passages 4 to 4 branched from one intake passage 3 are communicated with the intake boats of the respective cylinders A to A.
The branch exhaust passages 5 to 5 communicating with the exhaust boat A are collected into one exhaust passage 6, and a particulate filter (hereinafter referred to as
(abbreviated as filter) 7 is equipped.

The above-mentioned filter 7 is constructed by alternately closing both ends of a large number of holes formed in a honeycomb shape with a porous material, and exhaust gas flowing in through holes 7a whose upstream ends are open is passed through partition walls 7b between adjacent holes. Hole 7C whose downstream end is open for transmission
When the exhaust gas passes through the partition wall 7b, relatively small combustible exhaust particles in the gas are collected by the filter 7.

On the other hand, a heater 8 is provided in the intake passage 3, and a throttle valve 9 is provided upstream 1 of the heater 8. Further, in the exhaust passage 6, a throttle valve 10 is provided at a position downstream of the filter 7 described above. Each of these throttle valves 9.10 rotates around a support shaft 11.12 to vary the opening degree of the passage 3.6, and a lever 13.14 integrated with the support shaft 11.12 is connected to the throttle valve 9.10. The throttle valve 9.10 is actuated by pushing and pulling the rods 17, 18 and rotating them using air pressure acting on the diaphragm 15.16.

That is, the rod 17 on the intake passage side is connected to the diaphragm 15.
The diaphragm 15 and the vacuum control valve 19 are connected to each other through an air passage 20, and
An exhaust passage side female rod 18 is connected to the diaphragm 16, and the diaphragm 16 and the vacuum control valve 19 are connected to each other.
are communicated with each other by an air flow path 21. This vacuum control valve 19 is switched and driven by a control signal from a controller, which will be described later, when the vacuum pump 22 is activated, and this switching causes the vacuum pump 22 to communicate with the air passage 20, 21, and The air channels 20 and 21 are communicated with the atmosphere by cutting off the air flow. And the vacuum pump 22 is connected to the air flow path 20.
．． 21, the air suction force is applied to each diaphragm 15, 16 via the respective air flow path 20.21, and the diaphragm 15, 16 causes the rod 17.
18 is pulled and driven, and the throttle valves 9 and 10 are connected to the intake passage 3.
and is rotated in a direction to narrow the exhaust passage 6. Furthermore, since the air suction force is acting on the air passages 20.21 as described above, by communicating these air passages 20.21 with the atmosphere, the negative pressure acting on the diaphragms 15 and 16 is eliminated, and each rod 17.18 moves forward, throttle valves 9 and 10
is rotated in a direction to open the intake passage 3 and the exhaust passage 6.

Further, a delay valve 2 is provided in the air passage 20 that connects the diaphragm 15 on the intake passage side and the vacuum control valve 19.
3 is interposed. This valve 23 is provided with an orifice 24 in the internal partition wall, and when the air suction force from the vacuum pump 22 mentioned above acts on the air passage 20, the air is drawn from the diaphragm 15 side to the pump 22 through the air passage 20. The flowing air is throttled by the orifice 24 to keep the air flow rate slow and the operation of the diaphragm 15 and throttle valve 9 delayed. In addition, the delay valve 23 includes a one-way valve 25 that closes the valve hole 25a against the force in the air suction direction and opens the valve hole 25a when atmospheric pressure is applied.

Furthermore, an exhaust pressure control valve 26 is interposed in the air passage 21 that connects the diaphragm 16 and the vacuum control valve 19 on the exhaust passage 6 side. And the exhaust pressure control valve 26
A gas flow path 27 for taking out the exhaust pressure in the exhaust passage 6 on the upstream side of the exhaust passage side throttle valve 10 is connected to the gas flow path 27 for taking out the exhaust pressure in the exhaust passage 6 in the exhaust pressure control valve 26 . The exhaust pressure is compared with the spring force, and when the exhaust pressure exceeds the spring force, the valve body 29 shuts off the air passage 21, and when the exhaust pressure falls below the spring force, the air passage 21 is opened. Therefore, the spring 28 sets the reference exhaust pressure value of the exhaust passage 6 during filter regeneration processing.

Further, an orifice 30 is provided in the air flow path 21a between the exhaust pressure control valve 26 and the diaphragm 16.

On the other hand, a controller 3 performs various controls during filter regeneration.
1 is provided. When the filter regeneration is commanded, the controller 31 energizes the heater 8 described above, switches and controls the vacuum control valve 19, and controls the fuel injection pump 2 to keep the engine 1 in a high idle rotation state. At the same time, the fuel injection timing is controlled so as not to advance.

Next, the operation of the above configuration will be explained. During normal operation of the engine 1, the throttle valves 9 and 10 of the intake passage 3 and the exhaust passage 6 are both fully opened, and the heater 8 is not energized. do not have. In this state, the exhaust gas discharged from the engine 1 flows from the branch exhaust passages 5 to 5 to the exhaust passage 6, passes through the filter 7, and is discharged. It is collected by the filter.

As the amount of exhaust particulates collected in the filter gradually increases and approaches a state where the filter becomes clogged, a command is issued to regenerate the filter 7. In this embodiment, the transition to regeneration is performed by manual operation of the regeneration switch shown in FIG. 2, but the transition can also be made automatically by, for example, detecting an increase in the exhaust pressure upstream of the filter with a sensor (not shown). can also be considered.

In response to the regeneration command, the controller 31 immediately energizes the heater 8 to heat the air supplied to the engine 1 from the intake passage 3 through the branch intake passages 4 to 4, thereby promoting a rise in the temperature of the exhaust gas. Moreover, the controller 31 has a slight time lag Δ1. Then, the fuel injection pump 2 is controlled so that the rotational speed of the engine 1 becomes a high idle rotational speed, and the amount of exhaust gas to the exhaust passage 6 is increased.

Next, after a slight time lag Δt2, the controller 31 drives the vacuum control valve 19 to apply the air suction force of the vacuum pump 22 to each air flow path 20.
21. At this time, on the exhaust passage side, the exhaust pressure of the exhaust gas guided from the passage 6 to the gas flow passage 27 to the exhaust pressure control valve 26 has not increased enough to overcome the force of the spring 28, so the valve 26 is open, and as described above. The air suction force immediately passes through the air flow path 21 to the diaphragm 16.
The throttle valve 10 operates to throttle the exhaust passage 6.

However, the delay valve 2 is located in the air passage 20 on the side of the intake passage 3.
3 is interposed, and as a result of the air suction force acting through the orifice 24, the speed of the air drawn from the diaphragm 15 to the air passage 20 is lower than that on the exhaust passage side, so that the throttle valve 9 on the intake passage side The rotational speed of the intake passage 3 becomes slower, and the intake passage 3 is narrowed later than the exhaust passage 6.

By the way, when the rotation speed of the engine 1 is increased to high idle as described above, the timing of fuel injection into the combustion chamber of the engine 1 is accelerated (advanced) to control the fuel so that it is easy to completely burn the fuel in the combustion chamber. This is Sugadori, but here there is a slight time lag Δt from the operation of the throttle valve 9.10.
, the fuel injection timing is controlled so that it does not advance. If the fuel injection timing is delayed compared to the normal high idle rotation state in this way, the fuel will not be completely combusted in the combustion chamber, and the branch exhaust passages 5 to 5 from which the fuel will flow out when the exhaust valve opens will be prevented. So-called afterburning, in which combustion also occurs within the exhaust gas, occurs, and the temperature of the exhaust gas flowing from the branch exhaust passages 5 to 5 to the exhaust passage 6 increases.

As a result of the above control, the air warmed by the heater 8 is supplied to the engine 1, the engine 1 is operated in a high idling state, and the fuel injection timing is delayed, so that the exhaust passage 6 is filled with more air. A large amount of high temperature exhaust gas is sent out. Further, by narrowing the intake passage 3 and the exhaust passage 6, the exhaust pressure in the exhaust passage 6 increases, and this increase in exhaust pressure further increases the temperature of the exhaust gas in the exhaust passage 6. Therefore, as this exhaust gas passes through the filter 7, the exhaust particulates collected by the filter are effectively combusted by heat and pressure, and when this state is continued for a certain period of time by a timer etc., the exhaust gas is Particulates are completely removed from the filter 32 and the filter 32 is purified or regenerated.

By the way, since the above regeneration process is performed by increasing the exhaust pressure in the exhaust passage 6 using the throttle valve 9.10, if the exhaust pressure in the exhaust passage 6 increases too much, it will adversely affect the operation of the exhaust valve of the engine 1. . However, the exhaust pressure is
When it rises to a value that overcomes the spring 28 at
The air flow path 21 is blocked by the exhaust pressure control valve 26, so that no air suction force acts on the diaphragm 16, and the throttle amount of the throttle valve 10 becomes small, promoting exhaust gas discharge. The exhaust pressure on the upstream side of the engine is reduced, and the occurrence of the above-mentioned adverse effects is suppressed. On the other hand, when the exhaust pressure starts to decrease, the exhaust pressure control valve 26 opens the air passage 21 again by the action of the spring 28 and increases the throttle amount of the throttle valve 10. Therefore, the exhaust pressure is kept substantially constant at a value corresponding to the force of the spring 28, and the above regeneration process is effectively performed. Note that the air flow path 21 includes a flow path 2 between the exhaust pressure control valve 26 and the diaphragm 16.
An orifice 30 is provided in the part 1a, and the exhaust pressure control valve 2
Since the response of the diaphragm 16 and the throttle valve 10 to the ON-OFF of the throttle valve 6 is delayed, hunting of the throttle valve 10 can be prevented. Therefore, this orifice 30 can also be replaced by a chamber.

Then, when the above-described predetermined regeneration processing time t has elapsed, the vacuum control valve 19 opens each air passage 20.21 to the atmosphere. As a result, in the delay valve 23, the one-way valve 25 opens the valve hole 25a due to the inflowing atmospheric pressure,
The diaphragm 15 is immediately communicated with the atmosphere. The diaphragm 16 is also immediately communicated with the atmosphere through the exhaust pressure control valve 26. Therefore, the throttle valves 9 and 10 on the intake passage side and the exhaust passage side move back almost simultaneously.

In this way, the exhaust pressure on the upstream side of the throttle valve 10 in the exhaust passage 6 is detected, this exhaust pressure value is compared with the exhaust pressure value set by the spring 28, and the exhaust pressure is determined at the set exhaust pressure value. Since the filter 7 is regenerated by controlling the exhaust pressure to be maintained at a predetermined value, the exhaust pressure in the exhaust passage 6 is maintained at a predetermined value, and an adverse effect on the engine 1 is avoided. Also,
Since the exhaust pressure is raised to an appropriate value, the temperature of the exhaust gas is effectively raised, and the removal of exhaust particulates trapped in the filter is ensured.

In addition, in order to ascertain whether or not the above-mentioned filter filter regeneration process is being carried out effectively, temperature sensors 32, 32 such as thermocouples are installed at the upstream and downstream sides of the filter 7 in the exhaust passage 6.
may be provided, and the combustion state of the collected particulates may be determined based on the temperature detected by these sensors 32 and 32.

(Effects of the Invention) As is clear from the above explanation, according to the present invention,
When the filter is regenerated, the exhaust pressure, once raised to a predetermined value, is
Even if the exhaust pressure in the exhaust passage is attempted to decrease again due to the subsequent operation of the throttle valve on the intake passage side in the throttle direction, the exhaust pressure control means further throttles the throttle valve on the exhaust passage side to prevent the exhaust pressure in the exhaust passage from decreasing from a predetermined value. In addition, when the exhaust pressure is about to rise further from a predetermined value, the exhaust pressure control means reduces the throttle amount of the exhaust passage side throttle valve to prevent the exhaust pressure from rising. The exhaust pressure is kept constant, and engine failure due to an abnormal increase in the exhaust pressure can be avoided. In addition, by increasing the exhaust pressure in the exhaust passage to an appropriate value, the temperature of the exhaust gas is effectively raised, ensuring that the particulates trapped in the filter are combusted, and the purification or regeneration ability of the filter is improved. improves.

[Brief explanation of the drawing]

The drawings show an embodiment of the exhaust particulate removal device for a diesel engine according to the present invention, and FIG. 1 is a schematic diagram of the overall configuration, and FIG. 2 is a timing chart during filter regeneration processing. l...Diesel engine, 3...Intake passage, 6.
... Exhaust passage, 7... Filter, 9.10... Throttle valve, 19, 22. 23... Throttle valve driving means (19 is a vacuum control valve, 22 is a vacuum pump), 26
...Exhaust pressure control means (exhaust pressure control valve).

Claims (1)

[Claims] (1) An exhaust particulate removal device for a diesel engine equipped with a filter for collecting combustible exhaust particulates in the exhaust passage, wherein throttle valves are provided in the exhaust passage and the intake passage downstream of the filter, respectively. In addition, during filter regeneration, a throttle valve driving means operates a throttle valve on the exhaust passage side in a throttle direction and then operates a throttle valve on the intake passage side in a throttle direction, and a large exhaust pressure upstream of the exhaust passage side throttle valve. and exhaust pressure control means that detects the exhaust pressure and adjusts the degree of throttling of the throttle valve so that the exhaust pressure reaches a predetermined pressure set during filter regeneration. Engine exhaust particulate removal device.