JPH0551044B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust gas purification device that purifies engine exhaust gas, and in particular, the present invention relates to an exhaust gas purification device that purifies engine exhaust gas. It is related to a device that collects and burns and removes particulate matter (particulate matter).

(Prior Art) Various exhaust gas purification devices of this type have been proposed in the past. For example, as disclosed in Japanese Patent Application Laid-Open No. 56-98519, a catalytic filter is installed in the engine exhaust system to collect combustible particles in the exhaust gas and cause an oxidation reaction. An injection device that injects liquid fuel as a liquid that promotes the combustion of combustible particles is provided upstream of the catalytic filter, and the exhaust gas temperature is controlled by the oxidation reaction effect of the catalyst in the catalytic filter and the combustion promoting effect of the liquid fuel. It is known that combustible particles collected on a catalyst filter are burned and removed by heating the combustible particles to a temperature higher than the ignition temperature of the combustible particles, thereby regenerating the filter.

(Problem to be Solved by the Invention) In this case, if the above-mentioned liquid is injected and supplied when the engine is in a high-speed operating range and the amount of exhaust gas is large, the liquid jet flows at a high speed. It is disturbed by the influence of the exhaust gas flow, and the liquid tends to adhere to a portion of the filter surface. This phenomenon needs to be eliminated in order for the liquid to evenly burn the combustible particles collected by the filter.

In addition, the present applicant previously proposed in Japanese Patent Application No. 59-64627 that the ignition temperature of combustible particles is significantly lowered, and combustible particles are reliably burned and removed even during steady operation of the engine with relatively low exhaust gas temperature. In order to prevent this, a normal particulate filter, which only has the function of collecting combustible particles, is installed in the engine exhaust system instead of a catalytic filter, and the exhaust passage upstream of the particulate filter is As a liquid that promotes the combustion of particles, for example, a mixed emulsion of a catalyst component and a hydrocarbon component is injected and supplied, and each component of the catalyst and hydrocarbon is applied to the surface of the combustible particles collected by a particulate filter. We are proposing a technique for uniformly depositing.

In that case, when the liquid is injected and supplied under conditions where the exhaust gas temperature of the engine is high, some of the solvent other than the catalyst components is absorbed into the exhaust gas as the liquid injected from the nozzle of the injector reaches the surface of the filter. The catalyst component is vaporized by the heat of the gas, and the crystals of the catalyst component adhere to the filter surface without being highly dispersed.This is an improvement in that the catalyst component is uniformly attached to the filter surface, making effective use of the catalyst activity. There is room for

In addition, at high exhaust gas temperatures, the solvent continues to vaporize even after the liquid adheres to the filter surface, which reduces the ability of the catalyst components to penetrate downstream of the filter, resulting in insufficient stable combustion of combustible particles. becomes.

The present invention was made in view of the above points, and
The purpose of this is to prevent the liquid from adhering to the filter surface by appropriately setting the timing for injecting and supplying a liquid that promotes combustion of combustible particles into the exhaust passage upstream of the filter based on the engine operating conditions. The objective is to stabilize the combustion of combustible particles in the filter by making the liquid uniform and suppressing the vaporization of the catalyst component of the liquid.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention provides an exhaust gas purification device for an engine equipped with a particulate filter that collects combustible particles in the exhaust system. , an injector is disposed upstream of the particulate filter for injecting and supplying a liquid containing a catalyst component and a solvent and promoting combustion of the combustible particles by heating the exhaust gas.

Further, a starting detection means for detecting when the engine is started is provided, and a control means is provided for receiving the output of the starting detection means and controlling the injector to operate when the engine is started.

(Function) With the above configuration, in the present invention, when the engine is started after the particulate filter has become clogged due to the accumulation of combustible particles such as carbon, the start detection means detects the state; The injector is operated under the control of the control means that receives the output of the startup detection means, and a liquid containing a catalyst component and a solvent that promotes the combustion of combustible particles is injected upstream of the particulate filter. . At that time, when the engine is started, the flow rate of the exhaust gas is small and its temperature is low, so the liquid jet flow is less likely to be disturbed by the influence of the exhaust gas flow, and the liquid containing the catalyst component is less likely to be disturbed. teeth,
Evaporation of the solvent of the liquid injected from the injector is effectively suppressed. Therefore, the liquid adheres uniformly to the surface of the filter, and in the case of the liquid containing a catalyst component, the permeation effect of the catalyst component to the downstream part of the filter is ensured. Therefore, when the combustible particles deposited on the filter are heated by the exhaust gas and ignited and combusted after the engine is started, the combustion is performed stably and reliably.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 1 shows the overall configuration of an embodiment of the present invention, 1
4 is a swirl chamber type diesel engine equipped with a combustion chamber 2 and a swirl chamber 3 communicating with the combustion chamber 2; 4 is a fuel injection pump that injects fuel into the swirl chamber 3 of the engine 1 through a fuel injection nozzle 5; , the fuel injection pump 4 is driven by the engine 1 in synchronization with it.

Further, 6 is an exhaust passage for discharging the exhaust gas in the combustion chamber 2 of the engine 1, and in the middle of the exhaust passage 6, combustible particles mainly composed of carbon in the exhaust gas are removed. A particulate filter 7 is provided to collect the particulate matter. The particulate filter 7 separates the openings at both ends of a large number of honeycomb holes in a honeycomb body made of a porous material into one.
The honeycomb holes are alternately closed, and when exhaust gas passes through the partition walls between adjacent honeycomb holes, it is filtered and combustible particles are collected.

Further, 8 is the particulate filter 7.
This injector supplies a liquid for promoting combustion of the combustible particles by heating the exhaust gas to the upstream exhaust passage 6, and the injector 8 includes a tank 9 storing the liquid for promoting combustion; The electromagnetic on-off valve 1 is disposed in the exhaust passage 6 upstream of the particulate filter 7 with the jet nozzle 10a facing the surface of the filter 7.
0b, a communication pipe 11 connecting the injector 10 to the tank 9,
and an electric liquid supply pump 12 disposed in the middle of the communication pipe 11.
2 operation and the electromagnetic on-off valve 10 of the injector 10
By the opening operation of b, a predetermined amount (for example, 10 to 100 c.c.) of the liquid in the tank 9 is injected from the spout 10a of the injector 10 toward the filter 7, and is deposited on the surface of the filter. The liquid that promotes the combustion of the combustible particles is, for example,
0.05-0.5% by weight of one or more water-soluble compounds of white metals (Pt, Pd, Rh, Ir);
10% by weight of one or more base metals (V, Cu,
A catalyst component consisting of a water-soluble salt of Cr, Fe, Ni, Mo, Ca, Ba), 10 to 50% by weight of a hydrocarbon such as kerosene, light oil, heavy oil, alcohol, ketone (oxygenated hydrocarbon), etc. 1 to dissolve hydrocarbons in water
It consists of 10% by weight surfactant and the rest water, and these ingredients are mixed to form an emulsion.

Furthermore, 13 is a control circuit for controlling the operation of the electromagnetic on-off valve 10b of the injector 10 and the fluid supply pump 12 in the injector 8, and the control circuit 13 is connected to the fuel injection pump 4 corresponding to the engine speed. The pump shaft rotation speed signal and the control sleeve position signal corresponding to the engine load are input. Also, 14
15 is a cranking switch which is turned ON by the operation of the starter to start the engine and detects when the engine 1 is started; A back pressure sensor 16 detects the back pressure of the engine 1 and detects the combustion state of the combustible particles collected in the particulate filter 7 based on the exhaust gas temperature T in the exhaust passage 6 immediately downstream of the particulate filter 7. This is an exhaust gas temperature sensor that detects the temperature indirectly, and the outputs of the switch 14 and the sensors 15 and 16 are input to the control circuit 13. The control circuit 13 detects the operating range of the engine 1 based on the output signal of the fuel injection pump 4, and determines the preset and stored appropriate back pressure when the filter 7 is not clogged in the operating range. The actual back pressure detected by the back pressure sensor 15 is compared with the appropriate back pressure to determine whether or not the filter 7 is clogged, and the actual back pressure is higher than the appropriate back pressure. When the filter 7 is clogged, the injector 8 is controlled to operate based on the output signal of the cranking switch 14 when the engine is started thereafter, and the liquid supply pump 12 and the electromagnetic on-off valve 10b of the injector 10 are controlled to operate. A control means is configured to output an actuation signal to the injector 10 to cause the injector 10 to inject the liquid.

Next, the control operation in the above embodiment will be explained with reference to the flowchart shown in FIG.

First, initialization is performed in step _S1 after the start, and then, in steps _S2 and _S3 , the engine rotational speed and engine load are detected based on the shaft rotational speed of the fuel injection pump 4 and the control sleeve position, respectively. In the next step _S4 , the back pressure of the engine 1 is detected based on the output signal of the back pressure sensor 15, and then in step _S5 , the back pressure is applied to each of the engines 1 detected in the steps _S2 and _S3 . It is determined whether the back pressure has decreased once to a predetermined back pressure that is properly set in advance for each operating region, that is, whether the combustible particles collected in the particulate filter 7 have been burned and removed. , if this determination is NO, the process returns to step _S4 . Step S ₅ above
The judgment is based on the reduction of back pressure to the specified back pressure.
If the answer is YES, the process moves to step S ₆ and checks whether the back pressure detected in step S ₄ is higher than the predetermined back pressure, that is, whether or not the particulate filter 7 has increased the amount of combustible particles collected. It is determined whether or not there is a blockage, and if the determination is NO, the process returns to step _S2 and subsequent steps _S3 , _S4 , etc. are repeated.

On the other hand, if the judgment in step _S6 is YES, the process moves to step _S7 to count the current number of injections N of liquid by the injector 8, and in the next step _S8 , the current injection number N is calculated. The current injection amount Q of the liquid is determined by comparing it with a map of the injection amount characteristics with respect to the number of liquid injections that has been set and stored in advance as shown in FIG.

At this time, in the injection amount characteristic shown in FIG. 3 above, the injection amount Q is set to decrease as the number of liquid injections N increases, so the number of liquid injections N
Taking advantage of the fact that the amount of catalyst components deposited in the liquid on the particulate filter 7 increases with the increase in
While the deposited catalyst component ensures a certain degree of combustion promoting effect of combustible particles, it is possible to reduce the amount of liquid (catalyst component) used and reduce costs.

After determining the liquid injection amount Q as described above, step
In _S9 , it is determined whether or not the cranking switch 14 is ON, that is, whether the engine 1 is at startup. If this determination is NO, it is assumed that no liquid injection is performed, and step _S9 is executed. Continue and wait for the engine to start.

Then, when the engine 1 is in the starting state and the judgment in step _S9 becomes YES, steps _S10 to
Execute the liquid injection control routine in _S21 . In the first step _S10 of this liquid injection routine, the liquid supply pump 12 of the injector 8 is driven, and in the next step _S11 , the electromagnetic on-off valve 10 of the injector 10 is driven.
b is opened and the liquid is injected from the injector 10 onto the surface of the filter 7. Step S ₁₂
After setting flag F to "1" and memorizing it, proceed to step _S13 , set a timer, and proceed to the next step.
In _S14 , the timer determines the elapsed time from when the combustible particles of the filter 7 start injecting liquid until they are sufficiently combusted. When the timer times out, the timer is reset in step _S15 , and then, in step _S16 , the exhaust gas temperature T downstream of the filter 7, that is, the exhaust gas temperature T downstream of the filter 7 is determined based on the output signal of the second exhaust gas temperature sensor 16. The exhaust gas temperature rising due to the combustion of the combustible particles collected in the filter is detected, and in the next step _S17 , it is determined whether the exhaust gas temperature T is higher than the permissible limit value T _B that causes the filter 7 to crack. to judge. If this judgment is NO for T≦T _B , the step
Proceeding to _S18 , it is determined whether or not the drive time of the liquid supply pump 12 has elapsed for a predetermined time period corresponding to the liquid injection amount Q determined in step _S8 , and this judgment indicates that the determined injection amount Q has not yet been injected. If the answer is NO, the process returns to step _S16 to continue liquid injection. On the other hand, if the determination in step _S18 is YES, the process moves to step _S19 , where the electromagnetic on-off valve 10b of the injector 10 is closed, and at the same time, the operation of the liquid supply pump 12 is stopped in step _S20 , and the injector 8 is turned off. The process then proceeds to step _S21 , where the flag F set in step S _B is set to "0", and then returns to the first step _S1 . Further, if the judgment in step _S17 is YES, T>T _B , it is assumed that the combustion temperature of the combustible particles has increased abnormally, and the process immediately moves to steps _S19 to _S21 to end the liquid injection. .

Therefore, in this embodiment, by the above-described control operation, when the engine 1 is started after the filter 7 has become clogged due to an increase in the amount of combustible particles deposited in the injector 8, the injector is 8 is activated, liquid is injected and supplied from the injector 10 toward the surface of the filter 7, and the liquid adheres to the surface of the filter 7. Thereafter, when the exhaust gas temperature rises mainly due to the operation of the engine 1, the accumulated combustible particles ignite and burn due to the effect of lowering the ignition temperature of the liquid adhering to the surface of the filter 7, etc.
The filter 7 is regenerated.

In the case of the above-mentioned liquid injection, since the exhaust gas temperature is low at the time of starting the engine that performs the liquid injection, the injector 8
The solvent injected from the injector 10 can be prevented from vaporizing before reaching the surface of the filter 7, and the catalyst components of the liquid can be kept in a highly dispersed state and adhere uniformly to the surface of the filter 7, and the catalyst can be The activity can be effectively utilized. Moreover, since the amount of exhaust gas is small when the engine is started, the liquid jet flow injected from the injector 10 is less likely to be disturbed by the influence of the exhaust gas flow, and the liquid is distributed more uniformly over the entire surface of the filter 7. can be attached to. Furthermore, as mentioned above, since the exhaust gas temperature is low at the time of engine startup, even after the liquid from the injector 8 adheres to the surface of the filter 7, the vaporization of the solvent is suppressed, and the catalyst components flow downstream of the filter 7. It will penetrate smoothly. As a result, when the engine is subsequently operated, the combustible particles can be heated by the exhaust gas in the filter 7 and combusted evenly and stably, so that the filter 7 can be regenerated well.

In this example, a liquid mixture containing a catalyst component and a hydrocarbon component was used as the liquid that promotes the combustion of combustible particles, but the liquid may be a liquid containing only the catalyst component. may also be used.

(Effects of the Invention) As described above, according to the present invention, combustion of combustible particles collected by the filter is promoted by exhaust gas heating upstream of the particulate filter disposed in the exhaust system of the engine. When a liquid containing a catalyst component is injected and supplied by an injector, the injection timing is set at the time of engine startup when the flow rate of exhaust gas is low and its temperature is low, thereby reducing turbulence of the liquid injection flow by the exhaust gas flow. It is possible to uniformly adhere the liquid to the filter surface by suppressing the unevenness and unevenness, and furthermore, it is possible to suppress the vaporization of the liquid solvent and to burn the combustible particles evenly and stably on the filter, thus reducing combustion. This can contribute to the realization of reliable combustion removal of combustible particles in the filter using the promoting liquid.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is an overall schematic diagram, FIG. 2 is an explanatory diagram showing the control procedure of the main routine in the control circuit, and FIG. 3 is for determining the injection amount with respect to the number of liquid injections. FIG. 1... Engine, 6... Exhaust passage, 7... Particular filter, 8... Injector, 13...
Control circuit, 14...Cranking switch, 15
...Back pressure sensor, 16...Exhaust gas temperature sensor.

Claims (1)

[Scope of Claims] 1. An exhaust gas purification device for an engine equipped with a particulate filter that collects combustible particles in the exhaust system, comprising a catalyst component and a solvent upstream of the particulate filter. and an injector for injecting a liquid that promotes combustion of the combustible particles by heating the exhaust gas, a starting detection means for detecting when the engine is started, and an output of the starting detection means. An exhaust gas purifying device for an engine, comprising: a control means for controlling the injector to operate when the engine is started.