JPH059613B2 - - 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. 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 auxiliary fuel such as liquid or gas is provided upstream of the catalytic filter, and the exhaust gas temperature is adjusted to the ignition temperature of combustible particles by the oxidation reaction effect of the catalyst in the catalytic filter and the combustion promotion effect of the auxiliary fuel. By heating to a temperature above, the combustible particles collected on the catalyst filter are burned and removed.
A device that regenerates a filter is known.

(Problem to be solved by the invention) However, in this conventional type, when the engine is in the steady operating range, the exhaust gas temperature is relatively low (200% in the case of a diesel engine).
~300°C), the exhaust gas is not sufficiently heated to the ignition temperature of combustible particles despite the combustion promoting effect of the auxiliary fuel. As a result, the catalytic filter cannot be regenerated reliably due to poor combustion of combustible particles.
There was a risk that the back pressure of the engine would increase due to the clogging of the catalyst filter, thereby interfering with its normal operation.

Therefore, in Japanese Patent Application No. 59-64627, the present applicant installed a normal particulate filter, which only has the function of collecting combustible particles, in place of a catalyst filter in the exhaust system of an engine. By injecting and supplying a mixed emulsion of a catalyst component and a hydrocarbon component as a catalyst solution that promotes the combustion of combustible particles to the exhaust passage upstream of the particulate filter, the particulate filter can be The catalyst and hydrocarbon components are uniformly deposited on the surface of the combustible particles collected by the combustible particles, significantly lowering the ignition temperature of the combustible particles, even during steady engine operation with low exhaust gas temperature. We are proposing a technology that reliably burns and removes combustible particles.

By the way, in that case, if the exhaust gas temperature upstream of the particulate filter is higher than the vaporization temperature of the solvent, only the solvent of the catalyst solution injected from the injector will vaporize on the way due to the gas heat, causing the catalyst to evaporate. The crystals of the component become large and adhere to the filter, making it difficult to uniformly deposit the catalyst component on the combustible particles over the entire filter. Therefore, the ignition temperature of combustible particles cannot be significantly lowered, and the combustible particles deposited on the filter cannot be removed through stable combustion, making it difficult to regenerate the filter efficiently. The problem is that it is not possible.

(Object of the Invention) The present invention has been made in view of the above-mentioned points, and its object is to provide a solvent solution to By injecting only the catalyst solution, the temperature of the exhaust gas upstream of the filter is lowered by the heat of vaporization of this solvent, and the vaporization of the solvent is suppressed when the catalyst solution is injected and supplied.
Therefore, the purpose is to uniformly adhere the catalyst over the entire filter, to ensure stable combustion of combustible particles in the filter, and to efficiently regenerate the filter.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention is an engine exhaust gas purification device equipped with a particulate filter that collects combustible particles in the exhaust system. A catalyst solution injector that injects and supplies a catalyst solution that promotes combustion of the combustible particles upstream of the particulate filter, and a solvent injector that injects and supplies a solvent for the catalyst solution upstream of the particulate filter. and. moreover,
When the catalyst solution is injected from the catalyst solution injector, a control means is provided for controlling the operation of both injectors so that the solvent is injected from the solvent injector prior to the injection.

(Function) With the above configuration, in the present invention, when the filter is clogged and the catalyst solution is injected, the control means controls to inject only the solvent before injecting the catalyst solution, and this injection The atmospheric temperature upstream of the filter decreases due to the heat of vaporization of the solvent. Therefore, when the catalyst solution is subsequently injected by the catalyst solution injector, the solvent in the injected catalyst solution is prevented from further vaporizing in the reduced atmosphere, and the concentration of the catalyst solution is reduced to the original concentration. By keeping the catalyst component within an appropriate range, the catalyst component is evenly and evenly deposited on the filter surface, and the combustion of combustible particles in the filter is stabilized.

(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
is 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, and the fuel injection pump 4 is driven synchronously by the engine 1. Ru.

Reference numeral 6 denotes an exhaust passage for discharging the exhaust gas in the combustion chamber 2 of the engine 1, and a portion in the middle 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 formed by alternately closing the openings at both ends of a large number of honeycomb holes in a honeycomb body made of a porous material, and prevents the exhaust gas from passing through the partition walls between adjacent honeycomb holes. It is then filtered to collect combustible particles.

Further, a catalyst solution injector 8 is provided in the exhaust passage 6 upstream of the particulate filter 7 to inject and supply a catalyst solution that promotes combustion of the combustible particles.
is provided. The catalyst solution injector 8 has an injection port 9a disposed in the exhaust passage 6 upstream of the particulate filter 7 toward the surface of the filter 7, and an injection nozzle 9 having an electromagnetic on-off valve 9b. Catalyst tank 10 that stores
, a communication pipe 11 that communicates between the catalyst tank 10 and the injection nozzle 9 , and a catalyst solution supply pump 12 disposed in the middle of the communication pipe 11 , which controls the operation of the pump 12 and the injection nozzle 9 . Solenoid on-off valve 9
By the opening operation of b, a predetermined amount of the catalyst solution in the catalyst tank 10 is injected from the ejection port 9a of the injection nozzle 9 toward the filter 7, and is deposited on the surface of the filter. The catalyst solution that promotes the combustion of the combustible particles is, for example, 0.05 to 0.5% by weight of a water-soluble compound of one or more platinum metals (Pt, Pd, Rh, Ir), or 1 to 10% by weight of a water-soluble compound of one or more platinum metals (Pt, Pd, Rh, Ir). One or more base metals (V, Cu, Cr, Fe, Ni, Mo, Ca,
A catalyst component consisting of a water-soluble salt of Ba), 10 to 50% by weight of a hydrocarbon such as kerosene, light oil, heavy oil, alcohol, ketone (oxygenated hydrocarbon), and 1 to 10% by weight for dissolving the hydrocarbon. % of surfactant and the rest of water, these components are mixed to form an emulsion.

Furthermore, 13 is a solvent injector for injecting and supplying the solvent in the catalyst solution upstream of the particulate filter 7, and the solvent injector 13 includes a solvent tank 14 for storing the solvent, and a solvent tank 14 for storing the solvent.
A connecting pipe 15 that connects to the communication pipe 11 downstream of the catalyst solution supply pump 12 in the catalyst solution injector 8.
and a solvent supply pump 16 disposed in the middle of the connecting pipe 15, and by operating the pump 16 and opening the electromagnetic on-off valve 9b of the injection nozzle 9, a predetermined amount of the solvent in the solvent tank 14 is injected into the injection nozzle. The fuel is injected from the nozzle 9a into the exhaust passage 6 upstream of the filter 7.

The exhaust passage 6 on the upstream side of the injection nozzle 9 of the catalyst solution injector 8 and the exhaust passage 6 on the downstream side of the particulate filter 7 are communicated with each other by an exhaust bypass passage 17. The exhaust gas from 1 bypasses the injection nozzle 9 of the catalyst solution injector 8 and the solvent injector 13 and the particulate filter 7 and flows down. Further, at the upstream end of the exhaust bypass passage 17, that is, at the connection end with the exhaust passage 6 on the upstream side of the injection nozzle 9, a flow control valve is provided which controls the amount of exhaust gas flowing down the exhaust bypass passage 17. A valve 18 is provided. The flow control valve 18 is connected to the diaphragm device 2 via a rod 19.
0, and the negative pressure chamber 20a of the diaphragm device 20 is connected to the vacuum pump 22 via the negative pressure introduction passage 21.
A duty solenoid valve 24 that linearly switches the communication ratio between the negative pressure chamber 20a and the vacuum pump 22 or the atmosphere opening section 23 is disposed, and the negative pressure introduced into the negative pressure chamber 20a of the diaphragm device 20 is reduced. The size of the diaphragm device 2 is linearly controlled by the duty solenoid valve 24.
0, the flow rate control valve 18 is driven.

Furthermore, 25 is a control circuit as a control means for controlling the operation of the electromagnetic on-off valve 9b of the injection nozzle 9 in the injectors 8 and 13, the catalyst solution supply pump 12, the solvent supply pump 16, and the duty solenoid valve 24. The control circuit 25 receives a signal of the pump shaft rotation speed of the fuel injection pump 4, which corresponds to the engine rotation speed, and a signal of the control sleeve position, which corresponds to the engine load. Further, 26 is a first exhaust gas temperature sensor that detects the exhaust gas temperature _T1 in the exhaust passage 6 upstream of the particulate filter 7, and 27 is the exhaust gas pressure in the exhaust passage 6 immediately upstream of the particulate filter 7. In other words, the back pressure sensor 28 detects the back pressure of the engine 1, and the combustible particles collected in the particulate filter 7 are combusted 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 state, and each output of these sensors 26 to 28 is connected to the control circuit 25.
has been entered. The control circuit 25 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 27 is compared with the appropriate back pressure to determine whether the filter 7 is clogged, and the actual back pressure is higher than the appropriate back pressure. When the filter 7 is clogged, the filter 7 is clogged based on the output signal of the first exhaust gas sensor 26.
If the upstream exhaust gas temperature T ₁ is lower than the preset solvent vaporization temperature B, the catalyst solution injector 8
An operating signal is output to the catalyst solution supply pump 12 and the electromagnetic on-off valve 9b of the injection nozzle 9 to inject the catalyst solution as it is from the injection nozzle 9, while the exhaust gas temperature _T1 is higher than the solvent vaporization temperature _TB . , an activation signal is output to the electromagnetic on-off valve 9b of the injection nozzle 9 prior to the injection of the regular catalyst solution, and the solvent supply pump 1 of the solvent injector 8 is turned on for a predetermined period of time.
6 to inject only the solvent from the injection nozzle 9, the exhaust gas temperature _T1 upstream of the filter 7 is lowered to below the solvent vaporization temperature _TB , and then the solvent supply pump 16 It is configured to output an operation stop signal to the catalyst solution supply pump 12 and an operation signal to the catalyst solution supply pump 12 to control the operation of both the injectors 8 and 13 so that the catalyst solution is injected from the injection nozzle 9.

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

First, in step S ₁ after starting, flow control valve 1 is
8 to close the exhaust bypass passage 17, and then proceed to steps S ₂ and S ₃ .
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. In the next step _S4 , the back pressure of the engine 1 is detected based on the output signal of the back pressure sensor 27, and in step _S5 , the back pressure is detected in each operation of the engine 1 detected in the steps _S2 and _S3 . Whether or not the back pressure has decreased once to a predetermined back pressure that is properly set in advance for each area, that is, whether the combustible particles collected in the particulate filter 7 have decreased by 1 degree or not.
A determination is made as to whether or not the amount has been removed by combustion, and if the determination is NO, the process returns to step _S4 . If the judgment in step _S5 is YES because the back pressure has decreased to a predetermined back pressure, the process moves to step _S6 , and it is determined whether the back pressure detected in step _S4 is higher than the predetermined back pressure. In other words, it is determined whether the particulate filter 7 is clogged due to an increase in the amount of combustible particles collected, and if this determination is NO.
If so, the process returns to step _S2 and repeats subsequent steps _S3 , _S4 , and so on.

On the other hand, if the judgment in step _S6 is YES, the process moves to step _S7 , where the current injection number N of the catalyst solution by the catalyst solution injector 8 is counted, and in the next step _S8 , the current injection number N is counted. The current injection amount Q of the catalyst solution is determined by comparing this with a map of the injection amount characteristics with respect to the number of injections of the catalyst solution, which is set and stored in advance as shown in FIG.

At this time, in the injection amount characteristics shown in FIG. 4 above, the injection amount Q is set to decrease as the number of times N of catalyst solution injections increases, so By utilizing the increase in the amount of catalyst components deposited in the catalyst solution on the particulate filter 7, the amount of catalyst components used can be reduced while ensuring a certain degree of combustion promotion effect of combustible particles by the deposited catalyst components. Cost reduction can be achieved.

After determining the catalyst solution injection amount Q as described above, in step _S9 , the exhaust gas temperature T ₁ of the engine 1 is determined based on the output signal of the first exhaust gas temperature sensor 26.
Detect the exhaust gas temperature in the next step _S10
It is determined whether T ₁ is lower than the crack-proof permissible limit exhaust gas temperature T _A , 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. If the determination is NO (T ₁ ≧TA ₎ , it is assumed that a crack will occur in the filter 7 due to catalyst solution injection, and the process returns to step S ₉ to wait for the exhaust gas temperature T ₁ to decrease.

On the other hand, the judgment in step S ₁₀ above is YES if T ₁ < T _A
If so, the catalyst solution injection control routine of steps S ₁₁ to _{S 26} and steps S ₅₁ to S 26 shown in FIG.
Processes the exhaust gas amount control subroutine in _S56 in parallel.

First step of the above catalyst solution control routine
In _S11 , it is determined whether the exhaust gas temperature T ₁ detected by the first exhaust gas temperature sensor 26 is lower than the preset solvent vaporization temperature T _B , and this determination determines whether T ₁ ≧T _B. If NO, step S ₁₂
to move to. In step _S12 , an activation signal is sent to the solvent supply pump 16, and in the next step _S13 , the solvent supply pump 16 is activated based on the map of the pump operation time characteristics set and stored as shown in FIG. It is determined whether or not the operating time of the solvent supply pump 16 has elapsed for a predetermined period of time, and if NO, the operation of the solvent supply pump 16 has not elapsed for a predetermined period of time, step _S12 is made.
When the operation of the pump 16 is YES after a predetermined period of time has elapsed, it is assumed that the exhaust gas temperature _T1 upstream of the filter has fallen below the solvent vaporization temperature _TB , and the pump ₁₆ is resumed in step S14. After stopping the operation of step S16, the process moves to step _S15 . Also, if the judgment in step _S11 above is T ₁ <
When T _B is YES, the process immediately moves to step _S15 .

Then, in step _S15 , the catalyst solution supply pump 12 of the catalyst solution injector 8 is driven, and in the next step _S16 , the electromagnetic on-off valve 9b of the injection nozzle 9 is opened, and the catalyst solution is supplied from the injection nozzle 9 to the filter 7. Spray on the surface. After setting _the flag F to "1" and memorizing this state in step _S17 , the process moves to step _S18 and sets a timer. Determine the elapsed time from the start of injection until sufficient combustion occurs. When the timer times out, the timer is reset in step _S20 , and then, in step _S21 , the exhaust gas temperature _T2 downstream of the filter 7 is adjusted based on the output signal of the second exhaust gas temperature sensor 28. The exhaust gas temperature rising due to combustion of the collected combustible particles is detected, and in the next step S ₂₂ the exhaust gas temperature T ₂ is detected.
is the limit value T _C that causes a crack in filter 7.
Determine whether it is higher than. This judgment is T ₂ ≦
If T _C is NO, the process moves to step _S23 , where it is determined whether or not the driving time of the catalyst solution supply pump 12 has elapsed for a predetermined time corresponding to the injection amount Q of the catalyst solution determined in step _S8 . If this determination is NO indicating that the determined injection amount Q has not been injected, the process returns to step _S21 and the catalyst solution injection is continued. On the other hand, if the judgment in step _S23 is YES, the process moves to step _S24 , where the electromagnetic on-off valve 9b of the injection nozzle 9 is closed, and at the same time, the operation of the catalyst solution supply pump 12 is stopped in step _S25 , and the catalyst solution supply pump 12 is stopped. After the catalyst solution injection by the solution injector 8 is finished and the flag F set in step _S17 is set to "0", the process returns to the first step _S1 .
Also, the judgment in step _S22 above is YES of T ₂ > T _C
If this is the case, it is assumed that the combustion temperature of the combustible particles has increased abnormally, and steps _S24 to S24 are immediately performed.
Proceed to _S26 and end catalyst solution injection.

On the other hand, in the exhaust gas amount control routine, the back pressure upstream of the filter 7 is detected by the back pressure sensor 27 in the first step _S51 , and the amount of exhaust gas passing through the filter 7 is indirectly detected. Then, in the subsequent step _S52 , it is determined whether the detected back pressure is lower than a predetermined value corresponding to the appropriate amount of exhaust gas passing through the filter 7, and if this determination is YES, the process proceeds to step _S53 . In order to increase the amount of exhaust gas to the filter 7, the opening degree of the flow rate control valve 18 is made small and the exhaust bypass passage 1 is
A duty signal in the direction of closing the filter 7 is sent to the duty solenoid valve 24, and if the signal is NO, the process moves to step _S54 , where the valve opening of the flow rate control valve 18 is changed in order to reduce the amount of exhaust gas to the filter 7. A duty signal is sent to the duty solenoid valve 24 in the direction of increasing the exhaust gas bypass passage 17 to open the exhaust bypass passage 17, and through these steps _S51 to _S54 , the amount of exhaust gas passing through the filter 7 is maintained at the set value. . Thereafter, in step _S55 , it is determined whether the flag F of the catalyst solution control routine is F=1 or not, and the steps _S51 to _S54 are repeated until this determination becomes NO. When the above judgment becomes NO (F=0 due to the end of catalyst solution injection), the opening degree of the flow rate control valve 18 is set to zero in step _S56 to close the exhaust bypass passage 17, and then the process returns to the original step S. Return to ₁ .

Therefore, in this embodiment, when the catalyst solution is injected from the injection nozzle 9 of the catalyst solution injector 8 toward the surface of the filter 7 by the control as described above,
When the exhaust gas temperature _T1 detected by the first exhaust gas temperature sensor 26 is equal to or higher than the solvent vaporization temperature _TB , only the solvent is injected from the solvent injector 13 prior to injecting the regular catalyst solution. Due to the heat of vaporization of the injected solvent, the exhaust gas temperature T ₁ decreases to below the solvent vaporization temperature T _B and the atmosphere in the exhaust passage 6 upstream of the filter 7 becomes saturated with solvent vaporization, after which the injection occurs. This can prevent the solvent in the catalyst solution from evaporating. On the other hand, when the exhaust gas temperature T ₁ is lower than the solvent vaporization temperature T _B , the solvent does not vaporize even if the catalyst solution is directly injected. Therefore, even if the exhaust gas temperature _T1 changes, the catalyst component can be uniformly deposited over the entire surface of the filter 7. Therefore, the combustible particles in the filter 7 can be evenly burned and the regeneration can be performed satisfactorily.

Furthermore, even if the exhaust gas temperature T ₁ changes upward depending on the operating state of the engine 1, by injecting the solvent prior to the regular injection of the catalyst solution, the exhaust gas temperature can always be kept below the solvent vaporization temperature. Therefore, even if an inexpensive low-boiling point solvent such as distilled water is used as the solvent, there will be no adverse effects due to vaporization of the solvent, and costs can be reduced.

(Effects of the Invention) As described above, according to the present invention, the exhaust passage upstream of the particulate filter disposed in the exhaust system of the engine promotes the combustion of combustible particles collected by the filter. When a catalyst solution is injected and supplied by an injector, only the solvent of the catalyst solution is injected before the regular injection, and the heat of vaporization of the solvent lowers the atmospheric temperature upstream of the filter, which reduces exhaust gas. Even if the temperature changes, the solvent will not vaporize when the catalyst solution is injected, allowing the catalyst to adhere uniformly to the filter surface, stabilizing the combustion of combustible particles, and efficiently regenerating the filter. .

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall schematic diagram, FIGS. 2 and 3 are explanatory diagrams showing the catalyst solution injection and exhaust gas amount control procedures, respectively, and FIG. 4 is an illustration of the catalyst solution injection and exhaust gas amount control procedures. A characteristic diagram for determining the injection amount with respect to the number of injections, and FIG. 5 is a characteristic diagram for determining the operating time of the solvent supply pump. DESCRIPTION OF SYMBOLS 1... Engine, 7... Particulate filter, 8... Catalyst solution injector, 9... Injection nozzle, 10... Catalyst tank, 11... Communication pipe, 13
...solvent injector, 14...solvent tank.

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 catalyst solution that promotes combustion of the combustible particles is injected and supplied upstream of the particulate filter. a catalyst solution injector; a solvent injector that injects and supplies a solvent for the catalyst solution upstream of the particulate filter; and a solvent injector that injects a solvent for the catalyst solution upstream of the particulate filter; 1. An exhaust gas purification device for an engine, comprising: a control means for controlling the operation of both injectors so as to inject a solvent.