JPS61192806A - Exhaust-gas purifier for engine - Google Patents

Abstract

PURPOSE:To suppress the clogging of a particulate filter by installing an injector for jetting the catalytic solution for accelerating the combustion of the collected particles onto the upstream side of said filter and installing a viscosity reducing means for reducing the viscosity of the catalytic components. CONSTITUTION:On the upstream side of a particulate filter 7 arranged midway in the exhaust passage 6 of an engine 1, an injector 8 for jetting the catalytic solution for accelerating the combustion of the combustible particles collected by said filter 7 is installed. Said injector 8 is constituted of an injection nozzle 10 consisting of an injection port 10a and an electromagnetic ON/OFF-valve 10b and a feeding pump 12 for supplying the catalytic solution in a catalytic tank 9 into the above-described nozzle 10. A conduit for viscosity reducing solution is connected midway into a communication pipe 11 for the communication between the above-described tank 9 and the injection nozzle 10, and a feeding pump 31 for feeding the viscosity reducing solution consisting of the aqueous solution of phosphoric acid or phosphate in a tank 30 is installed into said conduit.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a device for purifying engine exhaust gas, and in particular to a device for cleaning combustible particles (particulates) such as carbon contained in the exhaust gas of a diesel engine or the like. This relates to a device that collects and burns and removes it.

(Prior Art) Various devices have been proposed to remove combustible particles such as carbon from exhaust gas. For example, a particulate filter may be provided in the exhaust passage to incinerate and remove the collected carbon particles by heating with a burner, or by electrical heating. There is something. However, when using burner heating, there is a risk that abnormal combustion may occur when the burner misfires and the particulate filter may melt, requiring complex control and high equipment costs. In this case, combustion occurs only near the heating wire, resulting in large power consumption and poor durability of the heating wire.

Furthermore, as disclosed in Japanese Unexamined Patent Publication No. 56-98519, a catalyst filter is disposed in the exhaust system of the engine to collect combustible particles in the exhaust gas and undergo an oxidation reaction, and the catalyst filter An injection device for injecting auxiliary fuel is provided upstream of the catalytic filter, and the oxidation reaction effect of the catalyst in the catalytic filter and the combustion promotion effect of the auxiliary fuel heat the exhaust gas temperature to a level higher than the ignition concentration of combustible particles. burns and removes combustible particles collected by
A device that regenerates a filter is known.

However, with this conventional type, when the engine is in the steady operating range, the exhaust gas temperature is relatively low (200 to 300 degrees Celsius for diesel engines), so despite the combustion promotion effect of the auxiliary fuel, the exhaust gas The gas is not heated sufficiently to the ignition temperature of the combustible particles, resulting in poor combustion of the combustible particles, which prevents reliable regeneration of the catalytic filter, and increases engine back pressure due to catalytic filter clogging. There was a risk that the normal operation of the vehicle would be hindered.

Therefore, in Japanese Patent Application No. 59-64627, the present applicant has provided an ordinary particulate filter, which has only the function of collecting combustible particles, in place of a catalytic filter in the exhaust system of an engine. As a liquid that promotes the combustion of flammable particles in the exhaust passage upstream of the filter,
For example, by injecting and supplying a mixed emulsion solution of a catalyst component and a hydrocarbon component, or an aqueous solution of a catalyst component (CuC9J2, etc.), the catalyst can be applied to the surface of combustible particles collected in a particulate filter. The ignition temperature of combustible particles is significantly lowered by uniformly depositing each of the hydrocarbon components and the combustible particles are reliably burned and removed even during steady engine operation with low exhaust gas temperature. We are proposing technology.

However, in the case of this proposal, the injected catalyst components gradually accumulate on the particulate filter, which causes clogging of the particulate filter and back pressure in the engine exhaust passage. may rise, eventually interfering with its normal operation.

(Object of the Invention) In view of the above-mentioned circumstances, the present invention reduces the viscosity of combustible particles that are injected and deposited on the particulate filter, thereby reducing the viscosity of the combustible particles that would otherwise clog the particulate filter. The purpose is to provide a purification device.

(Structure of the Invention) The engine exhaust gas purification device of the present invention includes a particulate filter that collects combustible particles such as carbon particles in the exhaust passage of the engine, and a particulate filter that collects combustible particles such as carbon particles on the upstream side of the particulate filter. An injector is provided to inject a catalyst solution containing a catalyst component to promote the combustion of The catalyst component is characterized by being provided with a viscosity reducing means for reducing the viscosity of the catalyst component by reacting it with a viscosity reducing agent.

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

FIG. 1 shows the overall configuration of an embodiment of the present invention, in which reference numeral 1 denotes a swirl chamber type diesel engine equipped with a combustion chamber 2 and a swirl chamber 3 communicating with the combustion chamber 2; This fuel injection pump injects and supplies fuel through a fuel injection nozzle 5, and the fuel injection pump 4 is driven synchronously by the engine 1.

Further, 6 is an exhaust passage for discharging the exhaust gas in the combustion chamber 2 of the engine 1, and a part of the exhaust passage 6 traps combustible particles mainly composed of carbon in the exhaust gas. A particulate filter 7 is provided to collect the particles. The particulate filter 7 is made of a honeycomb body made of a porous material, in which a large number of honeycomb holes are arranged along the exhaust flow direction, and one of the openings at both ends of the holes are alternately closed, and partition walls between adjacent honeycomb holes are formed. When exhaust gas passes through, it is filtered to collect combustible particles.

Further, a particulate filter 7 in the exhaust passage 6
An injector 8 is provided upstream to inject and supply a catalyst solution that promotes combustion of the combustible particles. The injector 8 is disposed in the exhaust passage 6 upstream of the particulate filter 7 with an injection port 10a facing the filter surface, has an electromagnetic on-off valve 10b, and has an injection nozzle 10 for injecting 1s solution onto the filter 7. , a catalyst tank 9 for storing a catalyst solution;
A communication pipe 11 that communicates this tank 9 with the injection nozzle 1o
, an electric catalyst solution supply pump 12 interposed in the middle of the cough communication pipe 11 , and a viscosity-reducing solution tank 30 that stores a viscosity-reducing solution made of an aqueous solution of phosphoric acid or phosphate and communicates with the communication pipe 11 . A viscosity-reducing solution supply pump 31 is provided to send and discharge the solution in the tank 30 to the communication pipe 11. Then, by operating the catalyst solution supply pump 12 and the viscosity-reducing solution supply pump 31 and opening the electromagnetic on-off valve 10b of the injection nozzle 10, the catalyst solution in the catalyst tank 9 and the viscosity-reducing solution in the viscosity-reducing solution tank 30 are activated. The injection nozzle 10 separately or simultaneously sprays a predetermined amount of
It is made to inject toward the filter 7 from the injection port. As a result, the combustible particles collected on the particulate filter are burned off by the catalyst component at a relatively low temperature, while the remaining catalyst component is oxidized by phosphoric acid in the viscosity-reducing solution.

It reacts with phosphates and turns into a substance with a low melting point, and is removed as a liquid by the heat of exhaust gas, thereby preventing clogging of particulate filters. The catalyst solution in the catalyst tank 9 is 10 grams of copper chloride (CuC9J).
z) in 100 cc of water is used, but in addition to this, for example, 0.05 to 0.5% by weight of one or more water-soluble platinum metals (Pt, Pd, Rh, Ir) is used. compound, or 1 to 10% by weight of 1 or 2
Base metals (V, cu, Cr, Fe, Ni
, Mo, Ca.

Ba) water-soluble salt in 10 to 50% by weight of kerosene.

Hydrocarbons such as light oil, lubricant oil, alcohol, or ketones (oxygenated hydrocarbons), and 1 for dissolving the hydrocarbons in water.
An emulsion obtained by mixing ~10% by weight of a surfactant with water may also be used.

The exhaust passage 6 on the upstream side of the injection nozzle 10 of the injection 18 and the exhaust passage 6' on the downstream side of the particulate filter 7 are communicated with each other by an exhaust bypass passage 13. ,
It is also possible to bypass the injection nozzle 10 of the injector 8 and the particulate filter 7 to allow it to pass through. Further, at the upstream end of the bypass passage 13, that is, at the connection end with the exhaust passage 6 on the upstream side of the injection nozzle 9, a flow control valve 14 consisting of a butterfly valve for controlling the amount of exhaust gas passing through the exhaust bypass passage 13 is provided. is installed. The flow control valve 14 is connected to a diaphragm device 16 via a rod 15.
A negative pressure chamber 16a of the diaphragm device 16 is connected to a vacuum pump 18 via a negative pressure introduction passage 17.

A duty solenoid pulp 20 that linearly switches the communication ratio between the negative pressure chamber 16a of the diaphragm device 116 and the vacuum pump 18 or the atmosphere opening section 19 is disposed in the middle of the negative pressure introduction passage 17. The magnitude of the negative pressure introduced into the negative pressure chamber 16a of the device 16 is linearly controlled by the duty solenoid pulp 20 to operate the diaphragm device 216, thereby driving and controlling the flow rate 1ilJIll valve 14.

Further, 22 is a control circuit for controlling the operation of the electromagnetic on-off valve 10b of the injection nozzle 10 in the injector 8, the catalyst solution supply pump 12, and the duty solenoid pulp 20. A signal of the pump shaft rotation speed of the fuel injection pump 4 corresponding to the number and a signal of the control sleeve position corresponding to the engine load are input. Further, 23 is a first exhaust gas temperature sensor serving as an exhaust gas temperature detection means for detecting the exhaust gas temperature T1 in the exhaust passage 6 upstream of the particulate filter 7, and 24 is in the exhaust passage 6 just upstream of the particulate filter 7. A back pressure sensor 25 detects combustible particles collected by the particulate filter 7 based on the exhaust gas temperature T2 in the exhaust passage 6' immediately downstream of the particulate filter 7. A second exhaust gas temperature sensor that indirectly detects the combustion state of the
Each output of 5 is input to the control circuit 22.

Next, the control operation in the above embodiment will be explained with reference to the flowcharts shown in FIGS. 2 and 3.

First, in FIG. 2, initialization such as closing the flow rate control valve 14 and closing the exhaust bypass passage 13 is performed in step S1 after the start, and then in step S82.
．． At 83, the engine rotation speed and engine load are detected based on the shaft rotation speed of the fuel injection pump 4 and the control sleeve position, respectively. After detecting the back pressure of the engine 1 based on the output signal of the back pressure sensor 24 in the next step S4, in step S5 the back pressure is determined in advance for each operating region of the engine 1 detected in the above steps 32 and 33. A judgment is made as to whether or not the back pressure has decreased once to a predetermined properly set back pressure, that is, whether or not the combustible particles collected in the particulate filter 7 have been burned and removed once, and this judgment is No. If there is, the process returns to step S4.

If the determination in step S5 is YES, the process moves to step S6, and it is determined whether the back pressure detected in step S4 is higher than a predetermined back pressure, that is, the particulate filter 7 increases the amount of combustible particles collected. It is determined whether or not there is a clogging state by
,84. ···repeat.

On the other hand, if the determination in step S6 is YES, the process proceeds to step S7, where the current injection number N of the catalyst solution by the injector 8 is counted, and in the next step S8, the current injection number N is As shown in the figure, the current injection amount Q of the catalyst solution is determined by comparing it with a map of the injection amount characteristics with respect to the number of times of catalyst solution injection that has been set and stored.

At this time, in the injection amount characteristics shown in Fig. 4 above, the injection amount Q is set to decrease as the number N of catalyst solution injections increases. As a result, the amount of autocatalytic components of the catalyst solution deposited on the particulate filter 7 increases, and the deposited catalyst component can ensure a certain degree of combustion promotion effect for combustible particles, reducing the amount of catalyst solution used and reducing costs. is being measured. Note that the viscosity-reducing solution injection IQ' is also determined at the same time.

Next, in step S9, it is determined whether the number of injections N is a multiple of a predetermined number Na (Na≧N), and if the answer is YES, steps 810 to 814 are performed, and if the answer is no, the process immediately proceeds to step 815. .

This is because the viscosity-reducing solution does not need to be injected every time the catalyst solution is injected, so the viscosity-reducing solution is injected once every predetermined number of Na times. When step S9 is YES, the viscosity-reducing solution supply pump 31 is driven in step 810, and the electromagnetic on-off valve 10b is opened in step S11 to inject the solution in the viscosity-reducing solution tank 30 onto the particulate filter 7. This injection continues until it is determined in step 813 that the predetermined time has elapsed, that is, the predetermined amount Q
The process continues until the injection of the viscosity-reducing solution 'is completed', after which the electromagnetic on-off valve 10b is closed and the viscosity-reducing solution supply pump 31 is stopped in steps 813 and 314.

After spraying the viscosity reducing solution as described above, step 815
The exhaust gas temperature T upstream of the particulate filter is determined based on the output signal of the first exhaust gas temperature sensor 23.
1, and in the next step 816 this exhaust gas temperature T
1 is lower than the permissible limit exhaust gas temperature T^ for cracking, which is the lower limit of the abnormal temperature range at which cracks occur in the filter 7 due to combustion of combustible particles accompanying catalyst solution injection, and this judgment is made. When T1≧T^, it is assumed that cracks will occur in the filter 7 due to catalyst solution injection, and the process returns to step S15', where the exhaust gas temperature T1 decreases.

On the other hand, when the determination in step 816 is 71<T^, the catalyst solution injection control routine in steps 317 to 828 and the exhaust gas amount control subroutine in steps 851 to 856 shown in FIG. 3 are processed in parallel.

First step 817 of the catalyst solution injection control routine
Then, the catalyst solution supply pump 12 of the injector 8 is driven, and in the next step S'18, the electromagnetic on-off valve 10 of the injection nozzle 10 is activated.
b is opened, and the catalyst solution is injected from the injection nozzle 10 onto the surface of the filter 7.

After setting the flag F to "1" and storing that state in step 819, the process moves to step 820 and sets a timer, and in the next step S21, the timer causes the combustible particles in the filter 7 to start injecting the catalyst solution. Determine the elapsed time from when the fuel burns to the point where it burns sufficiently. When the timer times out, the timer is reset in step S22, and then, in step 823, the exhaust gas temperature T2 downstream of the filter 7, that is, collected by the filter 7, is determined based on the output signal of the second exhaust gas concentration sensor 25. The exhaust gas temperature rising due to the combustion of the combustible particles is detected, and in the next step 824 it is determined whether this exhaust gas temperature T2 is higher than the limit value Ta that causes cracks to occur in the filter 7. If this judgment is T2≦TB, step 8
25, it is determined whether the drive time of the catalyst solution supply pump 12 has elapsed for a predetermined time corresponding to the injection mQ of the catalyst solution determined in step S8, and this determination determines whether the determined injection amount Q has not been injected. When the answer is NO, the process returns to step 823 and the catalyst solution injection is continued. On the other hand, if the determination in step S25 is YES, the process moves to step 826, where the electromagnetic on-off valve 1 of the injection nozzle 10
0b, and in step 827 the operation of the catalyst solution supply pump 12 is stopped to finish the catalyst solution injection by the injector 8. Then, after setting the flag F set in step 819 to "0", the first step Return to S1. Further, when the determination in step 824 is T2>Ta, it is assumed that the combustion temperature of the combustible particles has increased abnormally, and steps 828 to 828 are immediately executed to end the catalyst solution injection and proceed to the first step S1. Return to

On the other hand, in the exhaust gas amount control subroutine, the back pressure upstream of the filter 7 is detected by the back pressure sensor 24 in the first step 851, and the amount of exhaust gas passing through the filter 7 is indirectly detected. Then, in the subsequent step 852, the detected back pressure is applied to the exhaust gas filter 7.
It is determined whether or not the amount is lower than a predetermined value corresponding to the appropriate amount of passing through the flow, and if this determination is YES, step 853
In order to increase the amount of exhaust gas flowing into the filter 7, the opening degree of the flow rate control valve 14 is made small and the exhaust bypass passage 1 is
3 is transmitted to the duty solenoid valve 20, and if the determination in step S52 is No, the process moves to step 854, in which the flow rate control valve 14 is activated in order to reduce the amount of exhaust gas flowing into the filter 7. A duty signal in the direction of increasing the valve opening and opening the exhaust bypass passage 13 is transmitted to the duty solenoid valve 20, and the amount of exhaust gas passing through the filter 7 is maintained at the set value through steps 851 to 854. . Thereafter, in step 855, it is determined whether the 7 lag F of the catalyst solution injection routine is F-1 or not, and steps 851 to 854 are repeated until this determination becomes No. Then, the above judgment is F-0 due to the end of liquid injection.
Then, in step 856, the opening degree of the flow rate control valve 18 is made zero, the exhaust bypass passage 17 is closed, and the exhaust gas amount control is ended.

In addition, in the above embodiment, an example was shown in which the viscosity-reducing solution is injected and supplied onto the particulate filter 7, but instead of being injected and supplied, the viscosity-reducing agent may be carried on the particulate filter 7. To confirm the effect of the example, the diameter is 118°4511
1. A particulate filter with a width of 152.4 mm and carrying 10 wt % sodium hydrogen phosphate as a viscosity reducing agent was placed in the exhaust passage of an engine dynamo, and the exhaust back pressure was measured.

The results are shown in FIG. This figure is a graph showing the change in exhaust back pressure with respect to operating time.The catalyst solution is injected at the point marked (X) in the figure, and the solid line is for a particulate filter carrying the above-mentioned viscosity reducing agent. shows,
The broken line shows the case of a particulate filter without a viscosity reducing agent. As can be seen from this figure, when there is no viscosity reducing agent, the back pressure gradually increases due to clogging of the catalyst components, but when the viscosity reducing agent is supported, this increase is negligible.

<Effects of the Invention> As explained above, in the present invention, the viscosity reducing agent is injected and supplied onto or supported on the particulate filter, and the catalyst component and the viscosity reducing agent are reacted on the particulate filter. As a result of this reaction, the catalyst component changes into a low melting point substance, becomes liquid upon receiving exhaust heat, and its viscosity decreases, so that it flows out over the particulate filter and can prevent clogging of the particulate filter. Therefore, even if the engine is operated for a long time, the exhaust back pressure is unlikely to increase, and normal operation of the engine can be maintained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of the exhaust gas purification device according to the present invention, FIG. 2 is a flowchart showing the catalyst solution and viscosity reducing solution injection control operation by the above device, and FIG. FIG. 4 is a characteristic diagram for determining the injection amount with respect to the number of catalyst solution injections; FIG. 5 is a flowchart showing the exhaust gas amount control operation using the apparatus of the present invention 3 is a graph showing changes in back pressure with respect to engine operating time when the engine is operated. 1... Engine 3... Swirl chamber 6... Exhaust passage 7... Particulate filter 8... Injector 9... Catalyst tank 10... Injection nozzle 13... Exhaust bypass passage 2
2...Control device 24...Back pressure sensor 30...
Viscosity reducing solution tank

Claims (1)

[Scope of Claims] In an exhaust gas purification device for an engine equipped with a particulate filter that collects combustible particles in the exhaust system, a catalyst that promotes combustion of the combustible particles is provided upstream of the particulate filter. An injector is provided to inject and supply a catalyst solution containing the component, and the catalyst component that is injected and supplied from the injector and accumulated on the particulate filter is placed on the particulate filter with phosphoric acid or phosphoric acid. 1. An exhaust gas purification device for an engine, comprising a viscosity reducing means for reducing the viscosity of the catalyst component by reacting with a viscosity reducing agent such as salt.