JPS61164018A - Exhaust gas purifying device of engine - Google Patents

Abstract

PURPOSE:To realize stable combustion, by providing in the upstream of a particulates filter provided in an exhaust system an injection means performing intermittent injection in plural times in every injection timing of combustion promoting fluid of a combustible particle collected by said filter. CONSTITUTION:In a device providing a particulates filter 3 for collecting a combustible particle in exhaust gas in the half way part of an exhaust passage 2, said filter 3 provides in its upstream side in the exhaust passage 2 an injection equipment 6 injecting combustion promoting fluid of catalytic water solution hydrocarbon emulsion or the like. This injection equipment 6, being constituted by an injector 7, pump 9 and a tank 10 or the like, is controlled by a control unit 14. And the injection equipment 6, whose injector 7 performs intermittent injection in plural times, for instance, three times for a predetermined time after the injection is started, sets an injection interrupted time between the intermittent injections such that the higher increases an exhaust gas temperature the shorter the injection interrupted time decreases.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an engine exhaust gas purification device, and in particular to a particulate filter that captures combustible particles such as carbon particles contained in exhaust gas. The present invention relates to an exhaust gas purification device that burns and removes gas.

(Prior Art) Conventionally, as this type of exhaust gas purification device, for example, as disclosed in Japanese Patent Application Laid-Open No. 56-98519, there has been a system that collects combustible particles in the exhaust gas in the exhaust system of an engine. A catalytic filter that causes an oxidation reaction to occur is disposed, and an injector that injects an auxiliary fuel such as liquid fuel as a liquid that promotes the combustion of the combustible particles is provided upstream of the catalytic filter. It is known to burn off the collected combustible particles by heating the exhaust gas to a temperature above the ignition temperature of the combustible particles by catalytic reaction and promotion of the fuel by auxiliary fuel.

In addition, by supplying a catalyst solution, for example, as a liquid that promotes the combustion of the combustible particles upstream of the filter and depositing the catalyst on the surface of the combustible particles, the flammable particles are ignited by the reaction of the catalyst. Others have been proposed to lower the temperature.

By the way, in the device for injecting and supplying auxiliary fuel or catalyst solution as described above, a predetermined amount of the liquid is continuously injected and supplied at once every few hours, so Only a portion of the liquid adheres to the upstream surface of the filter, but most of the remaining liquid permeates into the midstream to downstream portions of the filter, relatively close to the center.

The liquid adhering to the surface of the upstream side of the filter is extremely effective in promoting the combustion of combustible particles because it easily comes into contact with oxygen in the exhaust gas. This promotes combustion.

On the other hand, the liquid that has permeated into the midstream or downstream side of the filter does not easily come into contact with oxygen in the exhaust gas, so it does not work very effectively in promoting the combustion of combustible particles.
Furthermore, when compared with combustion on the upstream side, combustion on the midstream or downstream side of the filter promotes combustion on the downstream side.

In other words, when the above liquid is continuously injected all at once,
Not only is it difficult to use this liquid effectively and its consumption increases, but also combustible particles attached to the outer periphery of the downstream side of the filter tend to be insufficiently burned (it is difficult to regenerate the entire filter uniformly). becomes difficult.

(Object of the Invention) The present invention provides an engine in which the entire filter can be regenerated by effectively utilizing the liquid by depositing most of the liquid that promotes combustion of combustible particles on the upstream side of the filter. The purpose of the present invention is to provide an exhaust gas purification device.

(Structure of the Invention) An engine exhaust gas purification device according to the present invention is an engine exhaust gas purification device including a particulate filter for collecting combustible particles in an exhaust system. It is provided with an injection means for injecting a liquid that promotes combustion of combustible particles in a plurality of intermittent injections at each injection timing.

(Effects of the Invention) As explained above, in the engine exhaust gas purification device of the present invention, the liquid that promotes combustion of combustible particles is injected intermittently multiple times at each injection timing upstream of the particulate filter. As a result, a small amount of liquid is injected each time, and this liquid adheres to the upstream surface of the high-temperature filter and the combustible particles on that surface. In this way, by intermittently spraying small amounts of the liquid, it is possible to prevent the liquid from penetrating into the middle or downstream side of the filter and to make it adhere to the surface of the upstream side of the filter in a uniform distribution. I can do it.

The liquid adhering to the upstream surface of the filter actively promotes the combustion of combustible particles, and combustion on the upstream side extensively promotes combustion on the downstream side, so the above method makes effective use of the liquid. Consumption can be reduced and the entire filter can be regenerated efficiently.

(Example) Hereinafter, an example in which the engine exhaust gas purification device according to the present invention is applied to a diesel engine will be described with reference to the drawings.

The overall configuration of the above exhaust gas purification device will be explained with reference to FIG. 1. A particulate filter 3 (hereinafter referred to as a filter) is interposed in the middle of an exhaust passage 2 of a diesel engine 1, and particulates flow into this filter 3. Exhaust passage 2 upstream of filter 3 to adjust exhaust gas flow rate
A bypass passage 4 is provided which branches off from the filter 3 and joins the exhaust passage 2 on the downstream side of the filter 3, and a throttle valve 5 is provided at the starting end of the bypass passage 4.

The filter 3 is a porous ceramic particulate filter having micropores, and has a large number of passages partitioned by a large number of partition walls, and the particulate matter contained in the exhaust gas is filtered by the partition walls. It is designed to capture combustible particles such as carbon particles.

In order to regenerate the filter 3 by burning the combustible particles trapped in the filter 3, an injection device 6 is provided for injecting a catalytic aqueous hydrocarbon emulsion into the exhaust passage 2 upstream of the filter 3.

The injection device 6 includes an injector 7 mounted in the exhaust passage 2 on the upstream side of the filter 3 toward the filter 3.
, a tank 10 for storing the catalyst aqueous hydrocarbon emulsion, a communication pipe 8 connecting the injector 7 to the tank 10, and a pump 9 interposed in the middle of the communication pipe 8.

An air nozzle 31 is provided that injects pressurized air toward the center of the downstream end face of the filter 3, and air is supplied to the air nozzle 31 from an air pump 32.

In addition, the reference numeral 33 in the figure is a swirling guide vane for generating swirling flow that is provided in the exhaust passage 2 at a position upstream of the upstream end face of the filter 3, and is an inner circumferential wall surface of the exhaust passage 2 that expands in a tapered shape. (See Figure 5).

The composition of the catalyst aqueous hydrocarbon emulsion is 0.0
5-0.5% by weight of platinum group metal (Pt) on one or two sides
, Pd, Rh, Ir), or 1-
Base metals (■, (:, u,
A catalyst component consisting of a water-soluble salt of Cr, Fe, Ni, MO% Ca, Ba) and 10 to 50% by weight of kerosene, light oil,
A hydrocarbon such as heavy oil, alcohol, or ketone (oxygen-containing hydrocarbon), and 1 to 10 for dissolving the hydrocarbon in water.
It consists of % by weight of a surfactant and the remainder by water, which are mixed together. Hereinafter, the catalyst aqueous hydrocarbon emulsion will be simply referred to as a catalyst solution or the like.

However, the catalyst solution and the hydrocarbon may be stored in separate tanks and both may be mixed and supplied to the injector 7, or only one may be supplied to the injector 7 as necessary. Of course.

The adjustment mechanism for adjusting the throttle valve 5 of the bypass passage 4 includes:
It is composed of a vacuum pump 11, a duty solenoid valve 12 connected to the vacuum pump 11, and a diaphragm actuator 13 connected to the duty solenoid valve I2 and connected to the throttle valve 5.

A control that controls the injection device 6, adjusts and controls the opening degree of the throttle valve 5, and controls the air pump 32 according to the combustion state of combustible particles captured in the filter 3. A unit 14 is provided,
Detection signals are input to this control unit 14 from various sensors described below.

The above sensor includes the exhaust passage 2 on the upstream side of the filter 3.
Back pressure sensor 1 that detects the internal back pressure and exhaust gas temperature, respectively.
5 and a first exhaust gas temperature sensor 16, a second exhaust gas temperature sensor 17 that detects the exhaust gas temperature in the exhaust passage 2 on the downstream side of the filter 3, and a fuel injection pump 1 of the engine 1.
a rotation speed sensor 19 that detects the rotation speed of the pump shaft of No. 8;
A load sensor 20 is provided to detect the position of the control sleeve of the fuel injection pump 18, and each detection signal is output to the control unit 14.

The control unit 14 is connected to the injector 7 by a solenoid valve (a second
A control signal is output from the control unit 14 to the pump 9 to turn the pump 9 ON/OFF.
A control signal for operation is output, and the control unit 1
4 outputs a control signal to the duty solenoid valve 12 for adjusting the throttle valve 5 by changing its duty ratio.

Next, the injector 7 is configured as shown in FIG. 2, for example.

That is, in the center of the injector body 21, an injection port 22, a guide hole 23, a spring mounting hole 24, a solenoid mounting hole 25, and a supply hole 26 are formed in a continuous manner in order from the tip side. Integral rods 27 are inserted and mounted between the receptacles 22 to 25, and the needle valve body portion 27a at the tip of the rod 27 abuts the valve seat at the rear end of the injection port 22 from the inside to form a valve, Guide part 27blJ of rod 27<
The rod 27 is installed in the X inner hole 23 so as to be slidable in the axial direction.
A flange-shaped spring receiving part 27c is disposed in the spring mounting hole 24, and the rod 27 is prevented from becoming clogged in the distal direction by a compression spring 28 that is externally attached to the loft 27 between the spring receiving part 27c and the base end wall of the spring mounting hole 24. A solenoid 29 is mounted on the outside of the rod 27 within the solenoid mounting hole 25, and an auxiliary solenoid 29 is mounted between the flange 27d at the proximal end of the rod 27 and the proximal wall of the solenoid mounting hole 25. A compression spring 30 is interposed.

Although not shown in FIG. 2, the communication pipe 8 is connected to the base end of the main body 21, and the catalyst aqueous solution, etc., which is pressure-fed from the communication pipe 8 into the supply hole 26, is passed through the hole on the outer periphery of the rod 27. It reaches the valve, and when the valve is opened, it is sprayed in the form of mist from the injection port 22 as shown in the figure. However, the above valve is designed to open against the spring force when the solenoid 29 is energized.

The control unit 14 includes, for example, each sensor 15.
・A to AD convert signals from 16, 17, 19, 20
D converter, input/output interface, read-only
Memory (ROM), Random Access Memory (R
AM), a central processing unit (CPU), and a drive circuit that converts and amplifies output signals to the pump 9 and solenoids 12 and 29, etc., and the read-only memory (
A program and various constants for a control routine to be described later are manually written and stored in the ROM (ROM).

Next, the control routine performed by the control unit 14 will be explained based on the flowchart of the main routine in FIG. 3(a) and the flowchart of the interrupt processing routine in FIG. 3(b). 324
and S30 to S35 indicate each step.

In Sl, necessary data is initialized, in S2 the detection signal from the rotation speed sensor 19 is read and the engine rotation speed is calculated, in S3 the detection signal from the load sensor 20 is read and the engine load is calculated, and in S4 Back pressure sensor 15
The back pressure inside the exhaust passage 2 is determined by reading the detection signal from the exhaust passage 2.

In S5, it is determined whether the back pressure has decreased to a predetermined value at least once after injecting the catalyst solution or the like. That is, if the carbon particles accumulated in the filter 3 after the previous injection are combusted due to the combustion promoting action of the catalyst solution, etc., the back pressure will drop below the predetermined value. This is to proceed to the next step on the condition that the lever, that is, the previously injected catalyst solution, etc. has contributed to combustion.

If the result of the determination in S5 is YES, the process moves to S6 and N
When the result is O, the process moves to S4.

In S6, it is determined whether the current back pressure is higher than a predetermined back pressure for each operating region.

The more carbon particles etc. accumulate in the filter 3, the more
Since the ventilation resistance increases and the back pressure on the upstream side of the filter 3 increases, the degree of accumulation of carbon particles is determined based on the value of the back pressure. However, since the amount of back pressure varies depending on the engine operating condition,
Predetermined allowable back pressure values corresponding to each operating range determined by engine speed and engine load can be read in advance as a map.
It is input and memorized in the only memory (ROM), and in S6, the allowable back pressure value of the operating area corresponding to the current operating state is compared with the current back pressure value, and the current back pressure is determined as the allowable back pressure value. When the pressure is higher than the pressure value, it is necessary to inject catalyst solution, etc., so the process moves to 37, and when it is not higher, the process moves to S2.

In S7, the number of current injections since the start of use of the engine is counted, and in S8, the amount of injection of catalyst solution, etc. is determined based on the number of injections.

The catalytic component contained in the catalytic solution promotes combustion through a catalytic reaction during the combustion of carbon particles, etc. During repeated injections, a portion of the catalytic component is emitted into the atmosphere along with the exhaust gas. Considering that the remaining portion is gradually accumulated in the filter 3, the injection amount of the catalyst solution etc. is determined according to the number of injections as shown in the graph of FIG.

In other words, since it is thought that the accumulated amount of catalyst components increases approximately in proportion to the number of injections as shown by curve a, the amount of catalyst solution etc. injected per time also increases in proportion to the number of injections as shown by the broken line. is set to decrease.

However, until the number of injections reaches a predetermined number, the accumulated amount of catalyst components is not so large, so a fixed amount is injected.

By the way, the newly injected catalyst component is injected in a highly active state in which it is ionized into an aqueous solution under conditions of high exhaust gas temperature due to an increase in back pressure, and carbon particles etc. accumulated in the upstream portion of the filter 3 are injected. Because it is supplied to the surface layer of the exhaust gas and easily comes into contact with oxygen in the exhaust gas, it acts extremely actively as a catalyst for promoting combustion, and combustion on the upstream side significantly promotes combustion on the downstream side.

On the other hand, the catalyst components accumulated in the filter 3 come into contact with carbon particles, etc. in a dry state under relatively low exhaust gas temperature conditions, and are buried in the accumulation layer of carbon particles, etc., and are buried in the exhaust gas. Because it also comes into contact with oxygen, it does not act as actively as a catalyst for promoting combustion.

Therefore, when setting the amount of catalyst components to be newly injected and supplied according to the amount of catalyst components accumulated in the filter 3, it is necessary to set the amount of catalyst components that have been accumulated and the effectiveness thereof. be.

In S9, the detection signal from the first exhaust gas temperature sensor 16 is read to determine the exhaust gas temperature T on the upstream side of the filter 3, and in S10, the exhaust gas temperature T is set higher than a predetermined temperature TA. It is determined whether the temperature is low or not, and if it is low, the process moves to Sll, and if it is not low, the process returns to S9.

If a catalyst solution or the like is injected when the exhaust gas temperature is high, such as during acceleration or under high load, the carbon particles accumulated in the filter 3 will rapidly burn, resulting in an abnormally high temperature, and the thermal stress will cause the ceramic filter 3 to This is because the exhaust gas temperature is injected on the condition that the exhaust gas temperature is lower than the predetermined temperature TA in order to prevent this from occurring, since cracks will occur in the filter 3 and the filter 3 will be damaged.

At Sll, the pump 9 of the injection device 6 is driven for a predetermined time period corresponding to the injection amount determined at S8, so that the pump 9 starts to be driven, and at the same time, at 312, the solenoid 29 of the injector 7 is energized. The valve of the injector 7 is opened to start injection, and in S13, the air pump 32 is driven and pressurized air is injected from the air nozzle 31 toward the center of the downstream end face of the filter 3.

When the above-mentioned pressurized air is not injected, when the catalyst solution, etc. is injected, the catalyst solution, etc. tends to concentrate near the center of the filter 3 where the exhaust gas flows quickly, and as a result, the carbon near the center of the filter 3 The combustion of particles, etc. is significantly promoted, the ventilation resistance is reduced, and the flow of exhaust gas is increasingly concentrated near the center, and the subsequent catalyst solution, etc., is also concentrated near the center, and the catalyst solution flows toward the outer periphery of the filter 3. is not supplied, making it difficult to regenerate the filter 3 in that part.

By supplying pressurized air and adding resistance to the flow near the center of the filter 3 as described above, the flow of exhaust gas inside the filter 3 is made uniform, so that the catalyst solution, etc. is uniformly distributed throughout the filter 3. The entire filter 3 is uniformly regenerated.

Next, in S14, the injection flag F is set to F=1.

In S15, the timer is set, and in S16, it is determined whether a relatively short predetermined time set in the timer has elapsed, and after the predetermined time has elapsed, the process moves to 317.
In S17, the timer is reset.

At step 318, the detection signal from the second exhaust gas temperature sensor 17 is read to determine the exhaust gas temperature T2 on the downstream side of the filter 3, and at step S19, the exhaust gas temperature T2 is set to a predetermined temperature T! It is determined whether or not the temperature is higher than l, and if it is high, the combustion of carbon particles, etc. is progressing sufficiently actively, so there is no need to continue injecting the catalyst solution, etc., and the process moves to 322, where the pump 8 is stopped, and the temperature is not high. In some cases, it is determined that it is necessary to continue the injection, and the process moves to 520.

In S20, it is determined whether or not a predetermined pump driving time corresponding to the injection amount determined in S8 has elapsed, and when it has elapsed, the process moves to S21, the injector valve is closed and injection is stopped, and the predetermined time has elapsed. 31 when not doing it
Return to B.

When the injector 7 is closed in S21, the drive of the pump 9 is stopped in S22, the air pump 32 is stopped in S23, and the injection flag F is set to F==0 in S24.

The above flowchart shows a general routine, and the injection of the catalyst solution etc. performed between steps 512 to S21 is actually performed in three intermittent injections as shown in FIG.

That is, when the injection quantity Q1 is injected for a predetermined period of time after the start of injection, the valve of the injector is closed, and only seconds have passed, which is a very short period of time necessary for the evaporative components contained in Q1 to evaporate. After that, the valve of the injector 7 is opened again and the injection amount Q2 is injected, and after the above injection is interrupted again for a second, the injection amount Q is finally injected and the valve of the injector 7 is closed. And the above Q1, Q2, Q3
is set so that the sum total becomes the injection amount Q determined in step 88.

The injection interruption time t is set to be shorter as the exhaust gas temperature becomes higher, as shown in FIG. 7, for example.

As mentioned above, when injecting small amounts intermittently, the injected catalyst solution, etc., does not penetrate into the interior of the midstream or downstream side of the filter 3, but adheres to the surface of the upstream side of the filter 3, and the catalyst components are removed from the exhaust gas. Since it is easy to come into contact with oxygen in the gas, combustion of combustible particles is actively promoted, and combustion on the upstream side widely promotes combustion on the midstream and downstream sides.

Moreover, since a swirling flow is added to the exhaust gas by the swirling guide vanes 33, mixing of the exhaust gas and the catalyst solution spray is promoted, and the exhaust gas flow uniformly flows in from the entire surface of the upstream end face of the filter 3. I will do it.

Next, the flowchart of FIG. 3(b) shows the bypass passage 4.
This shows an interrupt processing routine for controlling the throttle valve 5. The interrupt processing starts when the determination in the SIO of the main routine is YES, and returns after S24 is completed.

After starting the interrupt process, in S30, the detection signal from the back pressure sensor 15 of the exhaust passage 2 is read and the back pressure is determined, and in S31
Then, it is determined whether the back pressure is lower than a predetermined value, and if it is low, a signal for driving the throttle valve 5 in the closing direction is outputted to the duty solenoid valve 12 at 332, and if it is not low, a signal is output to the duty solenoid valve 12 at 332 In S33, a signal for driving the throttle valve 5 in the opening direction is output to the duty solenoid valve 12.

From S32 and S33, the process moves to 334, and in S34, it is determined whether the injection flag F is F=1, that is, whether or not injection is in progress. When F=1, the process returns to S30 and repeats steps 330 to S33, and F= When the value is 0, the process moves to S35 and the throttle valve 5 is operated to close the bypass passage 4. In this way, the throttle valve 5 of the bypass passage 4 is controlled as described above only during the injection of the catalyst solution or the like.

The current control is performed through the steps S1 to S24 and S30 to S35, and the next control is performed from S24 to 81.

As explained above, by injecting the catalyst solution etc. only when the exhaust gas temperature T1 on the upstream side of the filter 3 is lower than the predetermined temperature TA, the filter 3 is prevented from reaching an abnormally high temperature state, and the catalyst solution During injection, when the exhaust gas temperature T2 on the downstream side of the filter 3 becomes higher than the predetermined temperature T, injection is stopped to prevent the filter 3 from becoming abnormally high temperature. 3 is protected.

In addition, by controlling the throttle valve 5 of the bypass passage 4 during the injection of the catalyst solution, etc., an abnormally large amount of exhaust gas flows into the filter 3, and the catalyst solution, etc. flows into the center of the filter 3. This prevents abnormal combustion from occurring in the central part of the exhaust gas and allows a stable combustion state to be obtained under a stable exhaust gas flow rate.

In the above embodiment, a swirling flow is added to the flow of exhaust gas by the swirling guide vanes 33, but as shown in FIGS. The exhaust passage 2 may be eccentrically orthogonally arranged and connected to the portion 3a, and a swirling flow may be added by causing the exhaust gas to flow into the Taber portion a from a tangential direction.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall configuration diagram of an exhaust gas purification device for a diesel engine, FIG. 2 is a vertical sectional view of an injector, and FIGS. 3(a) and (b) are respectively A flowchart of the main routine and an interrupt processing routine of the control performed by the control unit, Fig. 4 is a diagram showing the injection amount of catalyst solution etc. and the accumulated amount of catalyst components, Fig. 5 is the v-v line cut in Fig. 1 Enlarged view, No. 6
The figure shows an operation time chart showing intermittent injection of catalyst solution, etc.
FIG. 7 is a diagram showing the relationship between exhaust gas temperature and injection interruption time, FIG. 8 is a longitudinal sectional view of a filter according to a modified example, and FIG. 9 is a view taken in the direction of the arrow (■) in FIG. 1. Diesel engine, 2. Exhaust passage, 3.
Particulate filter, 7. Injector,
8...Communication pipe, 9...Pump, 10...Tank, 14
··control unit. Patent applicant: Mazda Motor Corporation (Figure 2, Figure 4, Figure 3, Cb) Figure 5, Figure 6, Figure 7 Re-exhaust gas temperature - high

Claims (1)

[Claims] (1) In an exhaust gas purification device for an engine equipped with a particulate filter that collects combustible particles in the exhaust system, a liquid that promotes the combustion of the combustible particles is injected upstream of the particulate filter at every injection timing. An exhaust gas purification device for an engine, characterized in that it is provided with an injection means for injecting intermittently a plurality of times.