JPH0625535B2 - Exhaust gas purification device for engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to an exhaust gas purifying apparatus for purifying engine exhaust gas, and in particular, combustible particles such as carbon contained in exhaust gas of a diesel engine ( Particulate) is collected and burned and removed.

(Prior Art) Conventionally, various types of exhaust gas purifying devices of this type have been proposed. As an example, for example, JP-A-56-985.
As disclosed in Japanese Laid-Open Patent Publication No. 19, a catalyst filter for collecting combustible particles and the like in exhaust gas to cause an oxidation reaction is provided in an exhaust system of an engine, and liquid, gas and the like are provided upstream of the catalyst filter. An injection device for injecting auxiliary fuel is provided, and the exhaust gas temperature is heated to the ignition temperature of the combustible particles or higher by the oxidation reaction action of the catalyst in the catalyst filter and the combustion promotion action of the auxiliary fuel, and is collected in the catalyst filter. It is known that the combustible particles thus generated are burned and removed to regenerate the filter.

(Problems to be solved by the invention) However, in this conventional engine, the exhaust gas temperature is relatively low when the engine is in the steady operation range (200 to 300 ° C. for a diesel engine). The exhaust gas is not sufficiently heated to the ignition temperature of the combustible particles despite the action of promoting combustion of the fuel. As a result, the catalyst filter may not be reliably regenerated due to poor combustion of the combustible particles, and the back pressure of the engine may increase due to clogging of the catalyst filter, which may interfere with normal operation of the engine.

Therefore, the applicant of the present application has previously provided, in Japanese Patent Application No. 59-64627, an ordinary particulate filter having only a function of collecting combustible particles in place of the catalyst filter in the exhaust system of the engine. As a catalyst solution that promotes the combustion of combustible particles in the exhaust passage upstream of the filter, for example, by injecting and supplying a liquid obtained by mixing and emulsifying a catalyst component and a hydrocarbon component,
The catalyst and hydrocarbon components are evenly deposited on the surface of the flammable particles collected by the particulate filter to significantly reduce the ignition temperature of the flammable particles, and the engine exhaust gas temperature is low. We have proposed a technology that ensures that combustible particles are burned and removed even during operation.

By the way, in that case, if the liquid is injected and supplied when the engine is in a high load operation state and the ambient temperature in the exhaust passage upstream of the particulate filter is high,
Due to the heat of the exhaust gas, only the solvent is vaporized on the way, and the crystal of the catalyst component grows to adhere to the filter surface. In addition, when the engine is in a high-speed operation range and the injection supply is performed when the exhaust gas amount is large, the injection flow is disturbed by the influence of the exhaust gas flow flowing at a high speed, and a part of the filter surface is disturbed. It becomes attached unevenly. These phenomena need to be eliminated in order to uniformly disperse the liquid in the combustible particles collected in the filter to stably burn and remove the combustible particles, and to efficiently perform the regeneration of the filter. is there.

(Object of the Invention) The present invention has been made in view of the above points, and an object thereof is to perform injection supply of a catalyst solution for promoting combustion of combustible particles to a filter upstream, and flow of exhaust gas to the filter. By eliminating the solvent and when the ambient temperature upstream of the filter is low, the vaporization of the solvent is suppressed under a low ambient temperature and the jet flow of the catalyst solution is affected by the exhaust gas flow. Therefore, the catalyst component is uniformly applied to the combustible particles deposited on the filter, the combustible particles are stably burned and removed, and the filter is efficiently regenerated.

(Means for Solving Problems) In order to achieve the above-mentioned object, a solution means of the present invention is an exhaust gas purifying apparatus for an engine, which is provided with a particulate filter that collects combustible particles and the like in an exhaust system. An injector for injecting and supplying a catalyst solution for promoting combustion of the combustible particles is provided upstream of the particulate filter. Also, an exhaust bypass passage that bypasses the injector and the particulate filter to allow the exhaust gas to flow down, a switching valve that selectively circulates the exhaust gas to the particulate filter or the exhaust bypass passage, and the switching valve. Drive means for driving the valve. Furthermore, a temperature detector for detecting an ambient temperature upstream of the particulate filter or a signal related thereto is provided,
While controlling the drive means so as to block the flow of exhaust gas to the particulate filter by the switching valve when the catalyst solution is injected by the injector, the output signal from the temperature detector is received and the particulate filter upstream The control means for controlling the injector to operate when the ambient temperature becomes lower than the set value is provided.

(Operation) With the above configuration, in the present invention, when the particulate filter is clogged and the catalyst solution is injected, the control unit controls the drive unit to switch the switching valve and the exhaust gas passing through the filter. Is blocked, and the exhaust gas flows down through the exhaust bypass passage. Further, with the exhaust gas flow to the filter blocked, the temperature detector detects the ambient temperature upstream of the filter or a signal related thereto, and the ambient temperature upstream of the filter is below a set value (for example, solvent vaporization temperature). In the case of, the catalyst solution is immediately injected, while when it is higher than the set value, injection is performed at a stage where it waits for the set value or less to fall below the set value. Therefore, the injected catalyst solution is prevented from vaporizing the solvent under an atmosphere of reduced temperature, and the injection flow is not disturbed by the influence of the exhaust gas flow, and is evenly and uniformly distributed on the surface of the particulate filter. Therefore, the combustible particles that have adhered and are deposited on the filter can be stably burned and removed, and the filter can be efficiently regenerated.

First Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the overall construction of a first embodiment of the present invention, wherein 1 is a vehicle swirl chamber type diesel engine having a combustion chamber 2 and a swirl chamber 3 communicating with the combustion chamber 2, and 4 is the engine. 1 is a fuel injection pump for injecting fuel into the swirl chamber 3 through a fuel injection nozzle 5, and the fuel injection pump 4 is driven by the engine 1 in synchronization.

Reference numeral 6 denotes an exhaust passage for discharging the exhaust gas in the combustion chamber 2 of the engine 1. In the middle of the exhaust passage 6, combustible particles containing carbon as a main component in the exhaust gas are trapped. A particulate filter 7 for collecting is provided. 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 when exhaust gas passes through partition walls between adjacent honeycomb holes. This is filtered to collect combustible particles and the like in it.

8 is an injector for injecting and supplying a catalyst solution for promoting combustion of the combustible particles into the exhaust passage 6 upstream of the particulate filter 7, and the injector 8 is a catalyst solution for promoting combustion. A tank 9 for storing the gas, an injection nozzle 10 provided in the exhaust passage 6 upstream of the particulate filter 7 with an ejection port 10a facing the surface of the filter 7, and an electromagnetic opening / closing valve 10b; A communication pipe 11 to be connected and an electric catalyst solution supply pump 12 arranged in the middle of the communication pipe 11 are provided. The operation of the catalyst solution supply pump 12 and the injection nozzle 1 are provided.
When the solenoid opening / closing valve 10b of 0 is opened, a predetermined amount (for example, 10 to 100 cc) of the catalyst solution in the tank 9 is injected into the nozzle 10.
Is ejected from the ejection port 10a toward the filter 7 and attached to the surface thereof. The catalyst solution for promoting the combustion of the combustible particles is, for example, 0.05 to
0.5% by weight of one or more white metals (Pt, P
d, Rh, Ir) water-soluble compound, or 1 to 10% by weight of one or more base metals (V, Cu, Cr, F)
e, Ni, Mo, Ca, Ba) a catalyst component consisting of a water-soluble salt, 10 to 50% by weight of a hydrocarbon such as kerosene, light oil, heavy oil, alcohol, ketone (oxygenated hydrocarbon), and the hydrocarbon. 1 to 10% by weight of a surfactant for dissolving in water and the rest is water, and these components are mixed to form an emulsion.

Further, the exhaust passage 6 on the upstream side of the injection nozzle 10 of the injector 8 and the exhaust passage 6 on the downstream side of the particulate filter 7 are connected by an exhaust bypass passage 13.
The exhaust bypass passage 13 allows the exhaust gas from the engine 1 to flow down by bypassing the injection nozzle 10 of the injector 8 and the particulate filter 7.

Further, at the upstream end portion of the exhaust bypass passage 13, that is, the connection end portion with the exhaust passage 6 on the upstream side of the injection nozzle 10, exhaust gas is selectively supplied to the particulate filter 7 and the exhaust bypass passage 13. A switching valve 14 for switching and circulating is provided. The switching valve 14 is a rod 1
5, the negative pressure chamber 16a of the diaphragm device 16 is connected to the vacuum pump 18 via the negative pressure introducing passage 17, and
A three-way solenoid valve 20 for selectively switching communication with the vacuum pump 18 or the atmosphere opening portion 19 of the negative pressure chamber 16a of the diaphragm device 16 is disposed in the middle of the negative pressure introducing passage 17, and The three-way solenoid valve 20 controls the switching of the introduction of negative pressure into the negative pressure chamber 16a of the diaphragm device 16 or the opening of the negative pressure chamber 16a to the atmosphere to operate the diaphragm device 16, thereby driving the switching valve 14. The driving means 21 is configured as described above.

Further, 22 is a control circuit as a control means 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 three-way solenoid valve 20, and the control circuit 22 includes A signal of the pump shaft speed of the fuel injection pump 4 corresponding to the engine speed and a signal of the control sleeve position corresponding to the engine load are input. Also,
Reference numeral 23 denotes a first exhaust gas temperature sensor as a temperature detector for detecting an ambient temperature in the exhaust passage 6 upstream of the particulate filter 7, that is, an exhaust gas temperature T _1.
4 is a back pressure sensor for detecting the exhaust gas pressure in the exhaust passage 6 immediately upstream of the particulate filter 7, that is, the back pressure of the engine 1, 25 is the exhaust gas temperature T ₂ in the exhaust passage 6 immediately downstream of the particulate filter 7. It is a second exhaust gas temperature sensor that indirectly detects the combustion state of the collected combustible particles in the particulate filter 7, based on which the outputs of these sensors 23 to 25 are input to the control circuit 22. . Thus, the control circuit 22 detects the operating region of the engine 1 on the basis of the output signal of the fuel injection pump 4, and the preset and stored proper back pressure when the filter 7 is not in the clogged state in the operating region. Is searched, and the actual back pressure detected by the back pressure sensor 24 is compared and 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 catalyst solution is injected by the injector 8, and the switching valve 14 is switched by the control of the three-way solenoid valve 20 when the catalyst solution is injected to exhaust the exhaust gas to the particulate filter 7. Shut off the flow of
The exhaust gas is allowed to bypass the exhaust gas through the exhaust bypass passage 13, and the exhaust gas temperature T ₁ upstream of the filter 7 is compared with the solvent vaporization temperature T _A as a set value based on the output signal of the first exhaust gas temperature sensor 23. , Exhaust gas temperature T
_{When 1} is the solvent vaporization temperature T _A or lower, the catalyst solution is injected.

Next, the control procedure in the control circuit 22 will be specifically described with reference to the flowchart shown in FIG.

First, in step S ₁ after the start, initialization is performed by operating the switching valve 14 to close the exhaust bypass passage 13 and the like, and then in steps S ₂ and S ₃ , the shaft speed of the fuel injection pump 4 and the control sleeve position, respectively. The engine speed and the engine load are detected based on the. After detecting the back pressure of the engine 1 based on the output signal of the back pressure sensor 24 in the next step S ₄ , the back pressure of the engine 1 detected in the above steps S ₂ and S ₃ in step S ₅ for each operation of the engine 1. It is judged whether or not the predetermined back pressure properly set for each region has decreased once, that is, whether the combustible particles trapped in the particulate filter 7 have been once removed by combustion. when determination is NO the process returns to step S _4. Proceeds to step S ₆ when the determination in Step S ₅ is YES by drop to a predetermined back pressure of the back pressure, whether back pressure detected in the step S ₄ is higher than a predetermined back pressure, i.e. It is determined whether or not the particulate filter 7 is in a clogging state due to an increase in the amount of the combustible particles collected, and this determination is NO.
When it is the step S ₂ to go back subsequent step S _3, S _4, repeated _....

On the other hand, when the determination in step S ₆ is YES, the process proceeds to step S ₇ and the three-way solenoid valve 20
The exhaust bypass passage 13 by switching the switching valve 14
And the flow of exhaust gas to the injector 8 and the particulate filter 7 is shut off. Then, in the next step S _8, counts the time injection number N of the catalyst solution by the injector 8, then the time number of injections N in step S _9, is set and stored as shown in advance Figure 3 The present injection amount Q of the catalyst solution is determined by collating the map of the injection amount characteristics with respect to the number of injections of the catalyst solution.

At that time, in the injection amount characteristic shown in FIG. 3, the injection amount Q is set to decrease as the injection number N of the catalyst solution increases. Utilizing the fact that the deposition amount of the catalyst component in the catalyst solution on the particulate filter 7 increases, the use amount of the catalyst solution can be reduced while securing the combustion promoting effect of the combustible particles to some extent by the deposited catalyst component. Can be down.

After determining the catalyst solution injection amount Q as described above, step S ₁₀
Based on the output signal of the first exhaust gas temperature sensor 23 detects the exhaust gas temperature T ₁ of the engine 1 at, its exhaust gas temperature T ₁ of the next step S _11, the solvent is vaporized along with the catalyst solution injection It is determined whether the temperature is lower than the solvent vaporization temperature T _A. If the determination is NO, that is, T ₁ > T _A , the process returns to step S ₁₀ and waits for the exhaust gas temperature T ₁ to decrease.

On the other hand, when the determination in step S ₁₁ is YES of T ₁ ≦ T _A in step S _12, to drive the catalyst solution feed pump 12 of the injector 8, the electromagnetic opening and closing of the injection nozzle 10 at the next step S ₁₃ The valve 10b is opened, and the catalyst solution is injected from the injection nozzle 10 onto the surface of the filter 7. After storing upright "1" in the flag F to the state in step S _14,
Sets the timer proceeds to step S _15, to determine the passage of time by the timer in the next step S ₁₆ until the combustible particles of the filter 7 is sufficiently burned from the start of injection of the catalyst solution. When the timer times out, the timer is reset in step S ₁₇ , and then the exhaust gas temperature T ₂ downstream of the filter 7, that is, the filter 7 based on the output signal of the second exhaust gas temperature sensor 25 in step S ₁₈ . The exhaust gas temperature that rises due to the combustion of the combustible particles captured by the exhaust gas is detected, and in the next step S ₁₉ , the exhaust gas temperature T ₂ causes a limit value T that causes cracks in the filter 7.
_It is determined whether it is higher than _B. This judgment is T ₂ ≦ T _B
When it is NO, the driving time of the catalyst solution feed pump 12, it is determined whether a predetermined time has elapsed that corresponds to the injection quantity Q of the catalyst solution which has been determined in step S ₉ proceeds to step S _20, the When the determination is NO, which indicates that the determined injection amount Q has not been injected, the process returns to step S ₁₈ and the catalyst solution injection is continued. On the other hand, when the determination in Step S ₂₀ is YES and proceeds to step S _21, closes the electromagnetic on-off valve 10b of the injection nozzle 10, by stopping the operation of the catalyst solution feed pump 12 in step S ₂₂ injection Exit catalyst solution injection by vessels 8, then the flag F erected in step S ₁₄ proceeds to step S ₂₃ as well as to "0", after stopping the driving of the three-way solenoid valve 20 at step S ₂₄ , The first step S
Return to ₁ . Further, the judgment in step S ₁₉ is T ₂ > T
When it is YES in _B immediately above steps S ₂₁ to S is regarded as a state in which the combustion temperature of the combustible particles is increased abnormally
₂₄ is executed to end the catalyst solution injection.

Therefore, in this embodiment, when the catalyst solution is injected from the injector 8 by the control operation as described above, first, the three-way solenoid valve 14 is driven and controlled, and the exhaust gas to the injector 8 and the particulate filter 7 is controlled. Since the flow is cut off, the injection flow of the catalyst solution is not disturbed by the influence of the exhaust gas flow even if the operating state of the engine changes, and the catalyst solution is dispersed and adheres to the surface of the filter 7, The combustible particles collected by the filter 7 can be stably burned and removed, and thus the filter 7 can be efficiently regenerated.

Further, the injector 8 is controlled so as to inject the catalyst solution only when the exhaust gas temperature T ₁ upstream of the particulate filter 7 is kept at a low temperature equal to or lower than the solvent vaporization temperature T _A. In the catalyst solution thus obtained, vaporization of the solvent is suppressed, the crystal of the catalyst component becomes large, and the filter 7
Since the catalyst solution does not adhere to the surface, the catalyst solution can be uniformly adhered to the entire surface of the filter 7, and combustible particles on the filter 7 can be reliably and uniformly burned and removed. Regeneration can be performed more efficiently.

In the above examples, as the catalyst solution for promoting the combustion of the combustible particles, a catalyst solution containing a hydrocarbon component was injected and supplied, but the catalyst solution contains the hydrocarbon component. It may not be.

Further, in the above-described embodiment, the timing when the filter 7 is clogged, that is, the timing when the solution is injected to the filter 7 is indirectly detected by the back pressure of the engine 1. A method can be considered. Hereinafter, each of them will be described as an example. The same parts as those in FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

Second Embodiment FIGS. 4 and 5 show a second embodiment of the present invention, in which the solution injection timing is detected based on the traveling distance of the vehicle.

That is, in the present embodiment, as shown in FIG. 4, instead of the back pressure sensor 24 in the configuration of the first embodiment,
A travel distance integrator 26 that integrates the travel distance of the vehicle is used. In the figure, 1a is a crankshaft of the engine 1.

When the control circuit 22 performs signal processing, as shown in FIG. 5, after the engine load is detected in step S ₃ , the vehicle travels based on the output of the mileage integrating meter 26 in step S _4. distance detects the integrated value, running the solution injection to determine the magnitude relationship between the integrated value and a predetermined value of the travel distance in the next step S _6, the filter 7 when the YES mileage> predetermined value I decided to. The other structure is the same as that of the first embodiment.

Therefore, in this embodiment, the traveling distance of the vehicle is integrated, and when the integrated value reaches a predetermined value, it is determined that the filter 7 is clogged and the injection supply of the catalyst solution is started. The signal to be determined can be easily obtained, and the configuration can be simplified.

In this case, the integrating circuit 26 for integrating the traveling distance of the vehicle is used, and the control circuit 22 determines the magnitude relationship between the vehicle traveling distance integrated by the integrating meter 26 and the predetermined value. A travel distance sensor that outputs a signal each time the integrated value of the vehicle travel distance reaches a predetermined value is used, and when the output signal of the sensor is input to the control circuit 22, solution injection to the filter 7 is started. You may do it.

(Third Embodiment) FIG. 6 shows a third embodiment, in which the solution injection timing is detected based on the fuel consumption of the engine 1.

In this embodiment, instead of the mileage integrating meter 26 in the configuration of the second embodiment, a signal of the fuel supply amount supplied from the fuel tank to the engine 1 and a float in the fuel tank linked to the fuel meter. A fuel consumption integrating meter that integrates the fuel consumption of the engine 1 based on the position signal of is used.

Further, in the control circuit 22, as shown in FIG. 6, after detecting the engine load in step S ₃ , the integrated value of the fuel consumption is detected based on the output of the fuel consumption integrating meter in step S _4. In the next step S ₆ , the magnitude relationship between the integrated value of the fuel consumption amount and the predetermined value is the fuel consumption amount> the predetermined value YES.
When it is determined that the solution is injected, the solution is injected to the filter 7.

Therefore, in this embodiment, in order to detect the consumption amount of the fuel that is the source of the combustible particles, the correlation between the detected fuel consumption amount and the collected amount of the combustible particles collected by the filter 7 Is extremely high, and there is an advantage that the clogging state of the filter 7 can be detected with high accuracy.

(Fourth Embodiment) FIGS. 7 and 8 show the fourth embodiment, in which the solution injection timing for the particulate filter 7 is detected based on the operating time of the engine 1.

That is, as shown in FIG. 7, the control circuit 22 is supplied with an output signal of an operating time accumulator 27 for accumulating time in the ON operation state of the ignition key switch 28, and the ignition key switch 28 is turned ON. The operating time of the engine 1 is indirectly integrated depending on the state.
It should be noted that instead of the ON operation state of the ignition key switch 28, as shown by a broken line in FIG.
The operating time may be integrated in the operating state (power generation state) of No. 9.

Further, in the signal processing of the control circuit 22, as shown in FIG. 8, the integrated value of the operating time of the engine 1 is detected by the output signal of the operating time integrating meter 27 in step S ₄ , and the next step S ₆ Then, it is determined whether or not the integrated time has reached a predetermined value, and when it reaches the predetermined value, it is considered that the filter 7 is clogged, and the solution is jetted to the filter 7.

Therefore, in the case of this embodiment, since the operating time including the idle operating state of the engine 1 can be detected, there is an advantage that the solution injection timing can be determined with high accuracy.

(Fifth Embodiment) FIGS. 9 and 10 show a fifth embodiment, in which the solution injection timing to the filter 7 is determined based on the engine speed.

In the present embodiment, as shown in FIG. 9, a rotation speed sensor 30 of an electromagnetic type or an electromagnetic induction type, which is arranged close to the crankshaft 1a of the engine 1 to detect the engine rotation speed, and an output of the rotation speed sensor 30. There is provided a rotational speed integrator 31 for calculating an integrated value of the engine rotational speed based on the above.

Further, in the main routine of the control circuit 22, as shown in FIG. 10, after the initializing in step S ₁ ,
Detects the engine load in step S _3, it detects the integrated value of the engine speed based on the following steps S ₄ to the output of said rotational speed integrated meter 31, after which the integrated value in the step S ₆ is predetermined It is determined whether it is larger than the value. Then, when the determination is that the integrated value> the predetermined value is YES,
The solution is jetted to the filter 7.

Therefore, in this embodiment, the amount of the combustible particles trapped in the filter 7 is detected based on the integrated value of the engine speed, which has a high correlation therewith, so that the solution injection timing for the filter 7 can be determined with high accuracy. .

(Sixth Embodiment) FIGS. 11 to 13 show a sixth embodiment, focusing on the fact that the main component of the combustible particles captured by the particulate filter 7 is carbon having conductivity. Then, the collected amount is detected as an electric resistance value.

That is, in the case of the present embodiment, as shown in FIG. 11, a pair of electrodes 32, 32 is embedded facing each end of the particulate filter 7, and the electrodes 32,
A resistance value measuring device 33 for measuring an electric resistance value between the devices 32 is provided, and an output of the measuring device 33 is input to the control circuit 22.

Then, in the control circuit 22, as shown in FIG.
Detecting the electric resistance value between the electrodes 32 and 32 on the basis at step S ₄ on an output of the resistance measuring device 33 in the main routine, whether the resistance value in the next step S ₆ is smaller than the predetermined value judge. As the amount of conductive flammable particles collected by the filter 7 increases, the electrode 3
Since the electric resistance value between 2 and 32 decreases, when the electric resistance value becomes smaller than a predetermined value, it is determined that the filter 7 is in the clogging state, and the solution is jetted to the filter 7.

Therefore, in this embodiment, since the amount of collected particles in the filter 7 is directly detected, there is an advantage that the solution injection timing to the filter 7 can be determined more accurately.

In this case, as shown in FIG. 13, the filter 7 of the conductive catalyst component is increased by increasing the number of injections of the catalyst solution.
As the amount of deposition on the electrodes increases, the electrodes 32, 32
Since the resistance value between the electrodes 32 decreases, the initial resistance value between the electrodes 32 and 32 is measured and stored immediately after the particulate filter 7 in a state where the combustible particles are swept away, and the regeneration time of the filter 7 is stored. It is necessary to cancel the initial resistance value as a criterion for the above.

(Seventh Embodiment) FIGS. 14 and 15 show a seventh embodiment of the present invention, in which a filter 7 is supplied to a filter 7 on the basis of a predetermined functional expression which is set in advance using engine speed and engine load as variables. The solution injection timing is determined.

That is, in the present embodiment, as shown in FIG. 14, no special sensor for detecting the clogging state of the filter 7 is provided, and the engine speed and the engine speed based on the operating state of the fuel injection pump 4 are set. Reference each signal of engine load.

Then, in the main routine of the control circuit 22,
As shown in FIG. 5, after detecting the engine speed x ₁ and the engine load x ₂ in steps S ₂ and S ₃ , respectively,
In step S ₄ , a predetermined functional expression C = ∫f (x ₁ , where the engine speed x ₁ and the engine load x ₂ are variables
x ₂ ) dx, the C value is calculated, the magnitude relationship between the C value and the predetermined value is determined in the next step S ₆ , and when the C value is larger than the predetermined value, the solution injection to the filter 7 is performed. To do.

Therefore, in the case of this embodiment, since the amount of particles collected by the filter 7 is detected by both the engine speed x ₁ and the engine load x ₂ , the amount of particles collected can be detected accurately and easily. The solution injection timing to the filter 7 can be accurately detected.

Then, as a modified example of this embodiment, in addition to the engine speed and the engine load, the engine back pressure used in each of the first to sixth embodiments, the traveling distance of the vehicle, the fuel consumption amount, the engine operating time and the electric power are used. It is also possible to calculate the function by a predetermined function formula including two or more variables of the resistance value and determine the magnitude of the function and the predetermined value to detect the amount of collected particles.

(Effects of the Invention) As described above, according to the present invention, in order to promote the combustion of the combustible particles captured by the filter, the exhaust passage upstream of the particulate filter arranged in the exhaust system of the engine is provided. When the catalyst liquid is injected and supplied by the injector, the flow of exhaust gas to the injector and the particulate filter is blocked, and the catalyst solution is injected only when the ambient temperature upstream of the filter is below the set value. Therefore, the vaporization of the solvent of the catalyst solution is suppressed under the condition where the atmospheric temperature is lowered, the injection flow is not affected by the exhaust gas flow, and the catalyst component is spread over the entire filter surface. Can be applied evenly,
Therefore, the combustible particles deposited on the filter can be stably burned and removed to efficiently regenerate the filter.

[Brief description of drawings]

1 to 3 show a first embodiment of the present invention, FIG. 1 is an overall schematic configuration diagram, FIG. 2 is an explanatory diagram showing a control procedure of a control circuit, and FIG. 3 is an injection of a catalyst solution. It is a characteristic view for determining the injection amount with respect to the number of times. 4 and 5 show a second embodiment, FIG. 4 is a view corresponding to FIG. 1, and FIG. 5 is a view corresponding to FIG. FIG. 6 is a view corresponding to FIG. 2 showing the third embodiment. 7 and 8 show a fourth embodiment, FIG. 7 is a view corresponding to FIG. 1, and FIG. 8 is a view corresponding to FIG. 9 and 10 show a fifth embodiment,
9 is a view corresponding to FIG. 1, and FIG. 10 is a view corresponding to FIG. FIGS. 11 to 13 show a sixth embodiment, FIG. 11 is a view corresponding to FIG. 1, FIG. 12 is a view corresponding to FIG.
FIG. 3 is a characteristic diagram for determining the catalyst component deposition amount on the filter based on the change in electric resistance between the two electrodes. 14 and 15 show the seventh embodiment, and FIG. 14 shows the first embodiment.
FIG. 15 is a view corresponding to FIG. 2, and FIG. 15 is a view corresponding to FIG. 1 ... Engine, 6 ... Exhaust passage, 7 ... Particulate filter, 8 ... Injector, 13 ... Exhaust bypass passage, 14 ... Switching valve, 21 ... Driving means, 22 ... Control circuit, 23 ...... First exhaust gas temperature sensor, 24 ...... Back pressure sensor, 26 ...... Mileage meter, 27 …… Running time meter, 28 …… Ignition key switch, 29 ……
Alternator, 30 ... Revolution sensor, 31 ... Revolution counter, 32 ... Electrode, 33 ... Resistance measuring instrument.

Front page continuation (72) Kenji Okubo, 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (72) Hideaki Kurita, 3-1-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture (72) ) Inventor Kunihiro Yagi 3-1, Shinchi Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) References JP-A-56-54914 (JP, A) JP-A-59-155527 (JP, A)

Claims (1)

[Claims] 1. An exhaust gas purifying apparatus for an engine having a particulate filter for trapping combustible particles and the like in an exhaust system, wherein a catalyst solution for promoting combustion of the combustible particles is injected upstream of the particulate filter. An injector to be supplied, an exhaust bypass passage for bypassing the injector and the particulate filter to allow the exhaust gas to flow down, and a switching valve for selectively switching the exhaust gas to the particulate filter or the exhaust bypass passage for circulation. Drive means for driving the switching valve, a temperature detector for detecting an ambient temperature upstream of the particulate filter or a signal related thereto, and a particulate filter by the switching valve when the catalyst solution is injected by the injector. When the drive means is controlled so as to cut off the flow of exhaust gas of And a control means for receiving the output signal from the temperature detector and controlling the injector to operate when the ambient temperature upstream of the particulate filter becomes equal to or lower than a set value. Exhaust gas purification device for engines.