JPH03271515A - Exhaust minute particle purifier for diesel engine - Google Patents

Abstract

PURPOSE:To improve the renewability of a filter by providing an exhaust air throttle valve, which throttles when the filter is being renewed, more to the downstream of a exhaust system than the filter to seize the exhaust minute particles and by restraining the increase of the internal EGR amount while the throttle valve is throttling. CONSTITUTION:A ceramic filter 14 is provided intermediately in an exhaust passage 13 of a diesel engine E to seize the minute particles in the exhaust gas and an exhaust throttle valve 15 is provided intermediately more to the downstream than the filter 14. A exhaust fine particle purifier is composed of the exhaust throttle valve 15, an inlet throttle valve 10 and a shutter valve 12 forming an exhaust minute particle purifier. Upon regeneration treatment of the intake throttling filter 14 the exhaust gas temperature is raised by heating the inlet air with an electric heater 11 while the exhaust throttle valve 15 is throttled tightly. In addition, increase of EGR amount is restrained, suction of the inlet air is promoted and the oxygen contained in the exhaust gas is secured by keeping the shutter valve 12 half opened and switched to a smaller overlapping inlet/exhaust air amount of the valve timing thus raising the combustibility of the exhaust minute particles.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an exhaust particulate purification device for a diesel engine, and in particular to an improved regeneration means for regenerating an exhaust particulate collection filter installed in an exhaust system. Regarding.

[Prior art]

Generally, the exhaust gas from a diesel engine contains a large amount of exhaust particulates such as carbon particles and other unburned particles, but in diesel engines installed in vehicles, exhaust particulates are generally supplemented in the exhaust system. A ceramic filter (DPF) is installed to collect the collected exhaust particles, and in order to burn the collected exhaust particles and regenerate the filter, this filter is equipped with heating means such as an electric heater or burner, and is periodically Alternatively, the filter is heated by heating the exhaust gas by a heating means or by heating the filter itself at every idling time after the end of driving, every predetermined mileage, or every predetermined integrated value of engine speed, thereby burning exhaust particulates. (For example, see Japanese Unexamined Patent Publication No. 165524/1983).

[Problem to be solved by the invention]

Conventional filters for collecting exhaust particulates are equipped with heating means such as electric heaters and burners, but unless a very large heating means is provided, the filter cannot be completely regenerated and the pressure loss of the filter can be sufficiently reduced. It is difficult to reduce the energy consumption, and there is still room for improvement in terms of energy and performance.

Therefore, the inventor omitted the heating means, provided an exhaust throttle valve downstream of the filter in the exhaust system, throttled the exhaust passage with the exhaust throttle valve, raised the exhaust gas pressure and temperature, and regenerated the filter. invented the technology.

However, when the exhaust passage is throttled by the exhaust throttle valve and the exhaust gas pressure is increased, burnt gas may not be discharged to the exhaust system during the exhaust process and may remain in the combustion chamber, or may flow back from the exhaust system to the combustion chamber. (This is called internal EGR)
The amount of burned gas (this is called the internal EGR amount) increases,
There is a problem in that the oxygen concentration in the exhaust gas decreases and the filter regeneration ability decreases.

An object of the present invention is to provide a diesel engine exhaust particulate purification device that sufficiently regenerates a filter by increasing exhaust gas pressure and temperature through an exhaust throttle valve without using heating means such as an electric heater. It is to be.

[Means to solve the problem]

The exhaust particulate purification device for a diesel engine according to the present invention is provided with a filter for collecting exhaust particulates in the exhaust system of the diesel engine, and an exhaust throttle valve that is operated to throttle during filter regeneration on the downstream side of the filter,
A suppressing means is provided for suppressing an increase in the amount of internal EGR during the throttle operation of the exhaust throttle valve.

[Function] In the diesel engine exhaust particulate purification device according to the present invention, when the exhaust throttle valve downstream of the filter in the exhaust system is operated to throttle when regenerating the filter that collects exhaust particulates, the exhaust throttle valve is activated. The exhaust gas pressure on the upstream side of the valve increases and the resulting adiabatic compression causes the exhaust gas temperature to rise, so the exhaust particulates collected in the filter are combusted and the filter is regenerated.

On the other hand, when the exhaust gas pressure increases due to the throttle operation of the exhaust throttle valve, the internal EGR amount (the amount of burnt gas remaining in the combustion chamber at the completion of the exhaust stroke) tends to increase, but the increase in the internal EGR amount is suppressed by the suppressing means. Therefore, a significant decrease in the amount of fresh air taken into the combustion chamber does not occur, and a decrease in the oxygen concentration in the exhaust gas can be suppressed. Therefore, it is possible to promote the combustion of the exhaust particulates collected in the filter and to promote the regeneration of the filter.

[Effects of the Invention] According to the diesel engine exhaust particulate purification device according to the present invention, as explained in the [Operation] section above, by providing the exhaust throttle valve and the suppressing means, heating means such as an electric heater can be removed. It is possible to reliably regenerate the filter without using the filter, prevent a decrease in the oxygen concentration in the exhaust gas, promote the combustion of the collected exhaust particulates, and increase the filter regeneration ability.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

This embodiment is an example in which the diesel engine exhaust particulate purification device of the present invention is applied to a diesel engine mounted on a small truck.

First, the overall structure of this diesel engine E and exhaust particulate purification device will be explained with reference to FIG.

The above-mentioned engine E is a DOHC type in-line four-cylinder vertical engine, in which an intake port 2 and an exhaust port 3 are connected to the combustion chamber of each cylinder 1, and four sets of intake ports each open and close the downstream end of the intake port 2. The valve 4 is driven by an intake camshaft 5, four sets of exhaust valves 6 that open and close the upstream end of the exhaust port 3 are driven by an exhaust camshaft 7, and an air cleaner 9, an intake throttle valve 10, and an intake passage are provided in the intake passage 8. An electric heater 11 is provided for heating the air, and a shirtter valve 12 is provided at each intake port 2.

The exhaust passage 13 is equipped with a ceramic filter 14 (
This is generally referred to as a DPF), and an exhaust throttle valve 15 is provided downstream of the filter 14 to throttle the exhaust passage 13 when the filter 14 is regenerated.

A Bosch type fuel injection pump 17 is provided on the side of the cylinder block of the engine E, and pressurized fuel is supplied from this pump 17 to fuel injection nozzles (not shown) of each cylinder 1.

One actuator 18 that rotationally drives the four sets of shutter valves 12 synchronously, and the control rack 17a of the fuel injection pump 17 (this is connected to the accelerator pedal by a mechanical transmission system not shown). An actuator 19 to be operated, an actuator 20 to rotationally drive the intake throttle valve 10, and an actuator 21 to rotationally drive the exhaust throttle valve 15 are provided. These four actuators 18 to 21 are of a negative pressure operating type with a built-in diaphragm, and each actuator 18 to 21 is connected to an electromagnetic three-way valve 22 to 25, respectively. It is connected to a vacuum pump 27 via.

The electromagnetic three-way valves 22 to 25 and the electric heater 11 are electrically connected to and controlled by the control unit 50.

The intake camshaft 5 is provided with a valve timing changing mechanism 30 for changing the valve timing of the intake valve 4 to change the intake/exhaust overlap amount as shown in FIGS. 3 and 4.

As shown in FIG. 2, this valve timing changing mechanism 3
0 has a general structure, which will be briefly explained.

A spacer 31 is fixed to the end of the intake camshaft 5, and the pulley 28 on the outside of the spacer 31 is in sliding contact with the outer periphery of the front end of the spacer 31 at the end of the boss 32, and the proximal end of the boss 32 is connected to the intake camshaft. 5 and is fixed to a rotatable connecting member 33. The connecting member 33 is rotatably supported by a bearing portion 29 of the cylinder head, and a first gear 41 is spline-coupled to the other end of the connecting member 33.
A second gear 42 at the tip of the exhaust camshaft 7 is meshed and connected to the second gear 42 .

An annular piston 34 is installed inside the boss portion 32 of the pulley 28 between it and the spacer 31, and the piston 34 is divided into two parts in the axial direction, and both divided parts are fixed to each other by a plurality of pins. Helical splines in opposite directions are formed on both the inner and outer surfaces of the piston 34, and these helical splines mesh with the helical splines on the outer periphery of the spacer 31 and the helical splines on the inner periphery of the boss portion 32 of the pulley 28, respectively. The piston 34 is urged toward the tip side by a spring 35.

An oil passage 36 is formed in the intake camshaft 5 , the spacer 31 is fixed to the intake camshaft 5 by a fixing bolt 38 via a stopper 37 , and a through hole 39 communicating with the oil passage 36 is provided in the fixing bolt 38 . A pressure chamber 40 for introducing hydraulic pressure from the oil passage 36 is provided at the tip of the boss portion 32 of the boot IJ28.

A switching valve 43 for opening and closing the oil passage 36 is interposed at the other end of the intake camshaft 5, and a switching solenoid 44 for opening and closing the switching valve 43 is provided. A hydraulic supply path 45 is provided to supply pressurized oil to the switching valve 43 when the switching solenoid 44 is held OFF.
is opened, the pressurized oil supplied to the oil passage 36 is discharged to the outside, and the valve timing becomes as shown in FIG.

When the switching solenoid 44 is turned on and the switching valve 43 is switched to the closed position, hydraulic pressure is supplied from the oil passage 36 to the pressure chamber 40, compressing the spring 35 and moving the piston 34 in the axial direction. Since the spacer 32 and the pulley 28 rotate relative to each other via the spline on the outer periphery, the relative phase between the intake camshaft 5, which is integrated with the spacer 32, and the pulley 28 changes, and the valve timing becomes as shown in FIG. , so that the intake/exhaust overlap amount is small.

Next, the control system will be explained based on FIG.

The exhaust passage 13 is provided with an exhaust temperature sensor 16 upstream of the filter 14 for detecting the exhaust gas temperature T, and its detection signal is supplied to the control unit 50.

An idle switch 46 that is turned ON when the engine E is in an idle state is provided near the accelerator pedal, and an ON/OFF signal from the idle switch 46 is supplied to a control unit 50 to control the rotational speed of the crankshaft of the engine E. A crank angle sensor 47 is provided in conjunction with the crankshaft, and the crank angle signal is supplied to the control unit 50, and a DPF regeneration command switch 48 consisting of a normally open switch that instructs regeneration processing of the filter 14 is connected to the instrument. A signal of 0N10FF from the switch 48 provided on the panel is supplied to the control unit 1-50, and an indicator lamp 4 is provided on the instrument panel to indicate that the regeneration process of the filter 14 is completed.
9 is provided, and an indicator lamp 49 is controlled by a control unit 50.

The control unit 50 is mainly composed of a microcomputer, and also includes a necessary A/D converter, a waveform shaping circuit, four drive circuits for the four electromagnetic three-way valves 22 to 25, and a drive for the switching solenoid 44. It includes a circuit, a drive circuit for the indicator lamp 49, and the like.

A control program for the filter regeneration process shown in FIG. 5 is input and stored in advance in the ROM (read only memory) of the microcomputer of the control unit 50, and the control program is stored in the RAM (random access memory) of the microcomputer. Various memories necessary to carry out the control are provided.

By the way, the diesel engine exhaust particulate purification device of the present invention is provided with an intake throttle valve 10, a shatter valve 12, an electric heater 11, and an exhaust throttle valve 15, and controls these during the regeneration process of the filter 14 to reduce exhaust gas salts. 60
The temperature is raised to 0°C to burn exhaust particulates adhering to the filter 14 (filter regeneration process).
This will be explained based on the flowchart shown in the figure. Incidentally, the symbol St (i=1.2.3, . . . ) in FIG. 5 indicates each step.

When the DPF regeneration command switch 48 is turned on when the truck is stored in the garage and the engine E is kept in an idle state, such as after the completion of driving, control is started, and the electric power is sent to increase the intake air temperature and the exhaust gas temperature. Heater 11 is ON
At the same time, a drive current is output to the three-way valve 25, and the exhaust throttle valve 15 is throttled in a half-closed state (Sl). In this way, by throttling the exhaust throttle valve 15, the exhaust gas pressure can be increased and the exhaust gas temperature can be increased by adiabatic compression.

Next, the three-way valve 24 is driven to switch the intake throttle valve 10 to a half-closed state, and the three-way valve 22 is driven to switch the four shutter valves 12 to a half-closed state (S2). In this way, the intake air can be efficiently heated by the electric heater 11 by keeping the intake throttle valve 10 and the shatter valve 12 in the half-closed state and allowing only the necessary and sufficient amount of intake air to be drawn in.

Next, in S3, it is determined whether a predetermined time required for the electric heater 11 to enter the heating state has elapsed by measuring the clock signal with a soft timer,
When the predetermined time has passed, the process moves to S4, and the three-way valve 25
to close the exhaust throttle valve 15 to the maximum (70 to 80%).
fully closed) (S4). In this manner, by narrowing the exhaust passage 13, the exhaust gas pressure can be increased and the exhaust gas temperature can be rapidly raised through adiabatic compression. In addition,
As the exhaust gas pressure increases, the load on the engine E increases and the fuel injection amount also increases, so the exhaust gas temperature increases.

Next, in S5, the switching solenoid 44 of the valve timing changing mechanism 30 is turned on.

As a result, the amount of intake/exhaust overlap is reduced as shown in FIG. As mentioned above, when internal defect GR is promoted as the exhaust gas pressure increases, the amount of oxygen in the exhaust gas decreases due to the decrease in the amount of intake air, and the filter regeneration ability decreases, so the amount of internal EGR decreases. In order to suppress the increase, the amount of intake/exhaust overlap is reduced.

Furthermore, in addition to the intake throttle valve 10, the Shatta valve 12 is provided on the intake boat, and the Shatta valve 12 is controlled to be in a half-closed state as described above, so that the increase in the amount of internal EGR is suppressed by the blocking action of the Shatta valve 2. be done.

Next, the exhaust gas temperature T is read from the exhaust gas temperature sensor 16 (S6), and then the exhaust gas temperature T is set to the set value T (for example,
600°C) or higher (S7)
, when No, S7 is repeated and when T≧T0, S7 is repeated.
8, the three-way valve 23 is driven and the actuator 19 is activated.
By operating the control rack of the pump 17 via the engine, idle up is performed to increase the engine speed to 200 rpm (S8).

Due to this idle up, the fuel injection amount further increases and the exhaust gas flow rate increases significantly, so a large amount of high temperature exhaust gas can be supplied to the exhaust passage 13, so that the exhaust particulates attached to the filter can be reliably burned in a short period of time.

Next, in S9, the set time TMo is set in the soft timer TM.
(for example, 8 to 10 minutes), and then it is determined whether or not the set time TM has elapsed (S10), and if the set time TM has not elapsed, SIO is repeated and the set time TM is
, and the filter has been sufficiently regenerated, Sl
1, and in S11, the engine speed is controlled to return to the normal idle speed (750 rpm) via the three-way valve 23 and the actuator 19, and the electric heater 11 is switched to O.
The switch is switched to FF, the exhaust throttle valve 15, the intake throttle valve 10, and the shutter valve 12 are switched to full open, and the switching solenoid 4 is switched to FF.
4 is turned off, and then at 812, the indicator lamp 49 indicating the completion of the filter regeneration process is turned on for only a few seconds, and then the control ends. Note that the display lamp 49 may be turned on at the start of the regeneration process and turned off at the end of the regeneration process. After the above control is completed, the ignition key is removed to stop the engine E, if necessary.

Although the control of the filter regeneration process is started via the DPF regeneration command switch 48, the filter 14
Exhaust gas pressure detection sensors may be installed on the upstream and downstream sides of the engine E and may be configured to start when the pressure drop in the filter 14 reaches a predetermined value or more. It may be configured to start each time the filter 14 is operated, or it may be configured to start based on various parameters that directly or indirectly reflect the clogging state of the filter 14.

In the above exhaust particulate purification device, exhaust particulates such as carbon particles in the exhaust gas of the engine E are removed by the filter 14.
It is collected by the filter 14 and remains on the filter 14.

When regenerating the filter 14, the electric heater 11 heats the intake air, the exhaust throttle valve 15 is greatly throttled to raise the exhaust gas temperature T, and the exhaust gas is increased while increasing the amount of exhaust gas by increasing the idle. Since the temperature T is raised to about 600''C or more, the exhaust particulates adhering to the filter 14 can be burned in a relatively short time.

Moreover, at this time, the intake valve 12 is held in a half-closed state to suppress an increase in internal EGRI, and the intake/exhaust overlap amount of the valve timing is changed to a small value to suppress an increase in the internal EGR amount. is promoted, it is possible to prevent a reduction in the amount of oxygen in the exhaust gas and ensure the combustibility of exhaust particulates.

As another embodiment of the above embodiment, as shown in FIG.
1A may be provided. The control of the filter regeneration process is basically the same as the control described above, so a description thereof will be omitted.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention; Fig. 1 is an overall configuration diagram of a diesel engine and its exhaust particulate purification device, Fig. 2 is a sectional view of a pulp timing changing mechanism, and Figs. 3 and 4 are respectively An explanatory diagram of valve timing during normal operation and valve timing during filter regeneration processing, FIG. 5 is a flowchart of a filter regeneration processing control routine, and FIG. 6 is a diagram corresponding to FIG. 1 according to another embodiment. E...Diesel engine, 12...Shatta valve,
13...Exhaust passage, 14...Filter, 15...
・Exhaust throttle valve, 30... Valve timing change mechanism, 50 ・

Claims (1)

[Claims] (1) In the exhaust system of a diesel engine, a filter is provided to collect exhaust particulates, and an exhaust throttle valve is installed downstream of the filter that throttles during filter regeneration, and when the exhaust throttle valve throttles, the amount of internal EGR is increased. An exhaust particulate purification device for a diesel engine, characterized in that it is provided with a suppressing means for suppressing an increase in