JPH08303290A - Exhaust gas purifying device for internal combustion engine - Google Patents

Abstract

PURPOSE: To provide an exhaust gas purifying device for an internal combustion engine, having high purifying efficiency, in such a way as to effect after-injection of a small amount of fuel at the first half of an expansion stroke. CONSTITUTION: An exhaust gas purifying device for an internal combustion engine comprises an exhaust gas treating means 17 to purify exhaust gas; a temperature estimating means (ECU 18) to estimate an exhaust gas temperature; and a fuel injection control means (ECU 18) to operate a fuel injection means by deciding a fuel injection timing and an injection amount. When an exhaust gas temperature is below a given value, fuel is after-injected after injection of main fuel to generate an engine output, and an exhaust gas temperature is controlled so that temperature is adjusted to a proper value at which the coefficient of purification of the temperature estimating means is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, which purifies particulates and NOx contained in the exhaust gas of a diesel engine or the like.

[0002]

2. Description of the Related Art Diesel engine exhaust contains particulates and nitrogen oxides (NOx) consisting of gas and solid components, and these harmful components pose environmental problems. . Regarding the particulates, a method of purifying only the gas component by an oxidation catalyst provided in the exhaust passage of the diesel engine has been put into practical use. However, this method has a problem that the solid component of particulates cannot be purified at all, and the gas component cannot be purified when the exhaust temperature is lower than the activation temperature of the catalyst.

On the other hand, in Japanese Examined Patent Publication No. 6-10409, a trap filter carrying a catalyst collects particulates, and after collecting a predetermined amount of particulates, an intake throttle provided in an intake passage of an engine. A method has been proposed in which the temperature of the exhaust gas is raised by squeezing, and the particulate matter is burned to regenerate the trap filter. However, this method requires a new intake throttle means, its actuator, a control device, and the like, which complicates the configuration. Further, since the amount of exhaust gas temperature rise due to the intake throttle is not large, there is a problem that the filter cannot be regenerated in a running state where the exhaust temperature is low such as in city driving. Furthermore, when the intake air is throttled, the combustion state of the engine deteriorates, so the output decreases, and the emission deteriorates.

Further, in the above method, since another harmful component, NOx, cannot be purified, another purification means is required to purify NOx, resulting in a problem of increased cost and volume. On the other hand, for NOx, a method is known in which a catalyst is provided in the middle of an exhaust pipe, a reducing agent such as light oil is supplied upstream of the catalyst, the reducing agent and exhaust gas are mixed, and NOx is reduced and purified on the catalyst. Is. However, this method has a problem in that the reducing agent is a molecule having a high boiling point, so that the reactivity is low and the NOx reduction and purification efficiency is low. In addition, there is a problem that the device becomes large due to the complicated structure.

Therefore, Japanese Laid-Open Patent Publication No. 5-156993 proposes a method of controlling the fuel injection timing of a fuel injector for injecting fuel into a cylinder chamber by using a solenoid valve to promote purification. That is, after injecting the main fuel for generating the engine output, a very small amount of fuel corresponding to 0.3 to 3% of the main fuel injection amount is post-injected into the cylinder chamber where the temperature during the expansion stroke is lowered. The hydrocarbon is thermally decomposed without combustion to generate a highly reactive hydrocarbon. Then, this hydrocarbon is mixed with exhaust gas to reduce and purify NOx contained in the exhaust gas on a catalyst. However, this method has a problem that NOx cannot be purified when the exhaust temperature is lower than the activation temperature of the catalyst.

Further, in the method proposed in the above publication, the post-injection is always carried out at a fixed timing of the stroke, so that the degree of decomposition of the fuel is uniquely determined. That is, the higher the exhaust temperature, the higher the degree of decomposition of fuel and the smaller the carbon number of hydrocarbons supplied. However, as shown in FIG. 19 described in detail later, in order to efficiently reduce and purify NOx, the higher the exhaust temperature (T2 in FIG. 19), the larger the number of carbon atoms supplied (B in FIG. 19). There is a need.
Therefore, in this method, NO
There is a problem that a reducing agent (hydrocarbon) that maximizes the reduction purification efficiency of x cannot always be supplied to the catalyst.

Further, in order to control a very small amount of post-injection fuel, an extremely highly responsive solenoid valve is required, which causes a problem of increasing cost and volume. In addition, since this method cannot purify the particulates, which is another harmful component, in order to purify the particulates, a separate purifying device is required, which further increases the cost and volume.

[0008]

SUMMARY OF THE INVENTION Therefore, the present invention is intended to provide an exhaust gas purifying apparatus for an internal combustion engine, which is capable of efficiently purifying exhaust gas containing both particulates and NOx with a simple structure. .

[0009]

In the first invention of the present application, fuel injection means provided for each cylinder, exhaust treatment means interposed in the exhaust passage, operating state detecting means, and operating state detecting means are provided. Exhaust temperature estimation means for estimating the exhaust temperature from the output from the means, temperature comparison means for comparing the output of the exhaust temperature estimation means with a predetermined value, and fuel injection in the fuel injection means based on the output of the temperature comparison means An exhaust emission control device for an internal combustion engine, comprising: a fuel injection control means for deciding a timing and a fuel injection amount to operate the fuel injection means,
When the exhaust gas temperature is equal to or lower than the predetermined value, the fuel injection control means commands the post-injection of the fuel after the main fuel injection for generating the engine output, thereby changing the exhaust gas temperature of the engine to the operation of the exhaust processing means. Control the temperature range suitable for.

In the first aspect of the invention, what is most noticeable is that the fuel injection control means for controlling the fuel injection amount and the fuel injection timing, the temperature estimation means and the temperature comparison means are provided. When the exhaust temperature is lower than a predetermined value, the post-injection of fuel is instructed, and the fuel injection means is controlled so that the exhaust processing means has a temperature at which it operates well. In addition, it is preferable that the post-injection be performed at the timing of the first half of the expansion stroke. This is because if post-injection is performed in the first half of the expansion stroke, the temperature in the cylinder chamber will be high, the fuel will effectively burn, and the exhaust gas temperature can be raised efficiently.

In the second invention of the present application, the fuel injection means provided for each cylinder, the particulate trapping means interposed in the exhaust passage, and the pressure detecting means provided at the inlet side of the particulate trap means. An operating state detecting means, an exhaust temperature estimating means for estimating an exhaust temperature based on an output from the operating state detecting means, a temperature comparing means for comparing an output of the exhaust temperature estimating means with a predetermined value, and the operating state detecting means. Amount calculating means for calculating the amount of particulate accumulation in the particulate collecting means based on the outputs of the means and the pressure detecting means, a deposit amount comparing means for comparing the output of the particulate amount calculating means with a predetermined value, and the above temperature. Fuel injection control means for activating the fuel injection means by determining the fuel injection timing and the fuel injection amount in the fuel injection means based on the outputs of the comparison means and the accumulation amount comparison means. In the exhaust purification system of an internal combustion engine having, the fuel injection control means, particulate matter deposit amount in the particulate collecting means exceeds a predetermined value,
If the exhaust temperature is lower than the predetermined value, after the main fuel injection for generating the engine output, the execution of the post-injection of fuel in the first half of the expansion stroke of the engine is commanded.

What is most noticeable in the second invention is that
A particulate collection means as an exhaust treatment means, an exhaust temperature estimation means and a temperature comparison means, a deposition amount calculation means and a deposition amount comparison means, and a fuel injection control means are provided, and the fuel injection control means comprises: When the amount of particulate accumulation exceeds a predetermined value and the exhaust gas temperature is below a predetermined value, it is instructed to perform the post injection in the first half of the expansion stroke.

According to the third aspect of the present invention, the fuel injection means provided for each cylinder, the nitrogen oxide reducing means interposed in the exhaust passage, the operating state detecting means, and the output from the operating state detecting means. Exhaust temperature estimating means for estimating the exhaust temperature, temperature comparing means for comparing the output from the exhaust temperature estimating means with a predetermined value, and fuel injection timing and fuel injection amount in the fuel injecting means by the output of the temperature comparing means. In the exhaust gas purifying apparatus for an internal combustion engine, the fuel injection control means is a main engine for generating engine output when the exhaust temperature is equal to or higher than a predetermined value. After fuel injection, post-injection of fuel is performed in the latter half of the expansion stroke, and if the exhaust gas temperature is below a predetermined value, in addition to this, it is instructed to perform post-injection in the first half of the expansion stroke as well.

What is most noticeable in the third invention is that
A nitrogen oxide reduction means as an exhaust treatment means, an exhaust temperature estimation means and a temperature comparison means, and a fuel injection control means are provided, and the fuel injection control means is provided for the case where the exhaust temperature is equal to or higher than a predetermined value. Injection is performed in the latter half of the expansion stroke, and if the exhaust gas temperature is below a predetermined value, it is instructed to perform the post-injection in the first half of the expansion stroke as well.

In the fourth aspect of the present invention, the fuel injection means provided for each cylinder, the particulate trapping means interposed in the exhaust passage, and the nitrogen oxide reducing means interposed in the exhaust passage. , A pressure detecting means provided on the inlet side of the particulate trapping means, an operating state detecting means, an exhaust temperature estimating means for estimating an exhaust temperature from an output from the operating state detecting means, and an exhaust temperature estimating means for estimating the exhaust temperature. A temperature comparing means for comparing the output with a predetermined value, a deposit amount calculating means for calculating the particulate deposit amount in the particulate trapping means based on the outputs from the operating state detecting means and the pressure detecting means, and the deposit amount calculating means. Of the fuel injection timing and fuel injection amount in the fuel injection means based on the output from the temperature comparison means and the deposition amount comparison means In the exhaust gas purifying apparatus for an internal combustion engine, the fuel injection control means includes: a fuel injection control means for activating the fuel injection means, and the fuel injection control means, when the particulate accumulation amount in the particulate collection means is equal to or less than a predetermined value, After the main fuel injection to generate the engine output, the post-injection is performed in the latter half of the expansion stroke, and if the particulate accumulation amount on the particulate collection means exceeds the specified value and the exhaust temperature is below the specified value, In addition, a command is given to carry out post-injection even in the first half of the expansion stroke.

What is most noticeable in the fourth invention is that
It has particulate collection means and nitrogen oxide reduction means as exhaust treatment means, exhaust temperature estimation means and temperature comparison means, deposition amount estimation means and deposition amount comparison means, and fuel injection control means, If the particulate accumulation amount is less than the specified value, post-injection is performed in the latter half of the expansion stroke. If the particulate accumulation amount exceeds the specified value and the exhaust gas temperature is less than the specified value, the expansion stroke is also added. The post-injection is also performed in the first half of.

According to the fifth aspect of the present invention, the fuel injection means provided for each cylinder, the particulate trapping means interposed in the exhaust passage, and the nitrogen oxide reducing means interposed in the exhaust passage, Pressure detection means provided on the inlet side of the particulate collection means, operating state detection means, exhaust temperature estimation means for estimating exhaust temperature based on the output of this operating state detection means, and output of this exhaust temperature estimation means Fuel injection timing correction means for correcting and changing the fuel injection timing based on the above, temperature comparison means for comparing the output of the exhaust gas temperature estimation means with a predetermined value, and a pattern based on the outputs of the operating state detection means and the pressure detection means. A deposit amount calculating means for calculating the particulate deposit amount in the curate collecting means, a deposit amount comparing means for comparing the output of the deposit amount calculating means with a predetermined value, the temperature comparing means and the stack. In an exhaust emission control device for an internal combustion engine, comprising: a fuel injection control unit that determines a fuel injection timing and a fuel injection amount in the fuel injection unit based on the output of the amount comparison unit and operates the fuel injection unit. If the particulate collection amount in the particulate collection means is less than or equal to a predetermined value, after the main fuel injection for generating the engine output, a command is made to carry out post-injection of fuel in the latter half of the expansion stroke of the engine. When the particulate collection amount in the particulate collection means exceeds a predetermined value,
If the exhaust temperature is lower than the predetermined value, the fuel injection is instructed to be performed in the first half of the expansion stroke as well, and if the particulate accumulation amount is lower than the predetermined value, the latter half of the expansion stroke is performed. The injection timing of the injection is changed based on the output of the exhaust gas temperature detection means, and a command is made to delay the post injection timing from the set timing as the exhaust gas temperature becomes higher.

What is most noticeable in the fifth invention is that
In addition to the configuration of the fourth aspect of the invention, a fuel injection timing correction means for correcting and changing the fuel injection timing is provided, and the timing of the post-injection performed in the latter half of the expansion stroke when the particulate accumulation amount is equal to or less than a predetermined value, The command is to delay the exhaust temperature as the temperature rises.

On the other hand, the sixth invention of the present application is based on the above-mentioned fourth and fifth inventions.
In the invention, when the particulate accumulation amount in the particulate collection means exceeds the predetermined value and the exhaust gas temperature is equal to or lower than the predetermined value, the post injection in the latter half of the expansion stroke is not performed, and the post injection is performed only in the first half of the expansion stroke. Try to do in.

In each of the above inventions, it is preferable that the post-injection is performed in a specific cylinder or a specific cycle. This is because, as will be described in detail later, if the amount of post injection is increased by collectively performing post injection, the structure of an actuator such as a solenoid valve can be made inexpensive and control can be facilitated.

Further, the post-injection in the first half of the expansion stroke and the post-injection in the latter half of the expansion stroke are performed in different cylinders, or the cylinders in which the post-injection is carried out are sequentially switched. Preferably. This is because the operation life of the fuel injection means is prevented from concentrating on a specific cylinder and the number of operations of the fuel injection means is equalized, whereby the average life of the fuel injection means can be lengthened. Further, the exhaust gas temperature can be directly detected by the exhaust gas temperature detecting means without using the exhaust gas temperature estimating means.

[0022]

According to the first invention of the present application, a small amount of fuel (for example, 5 to 20% of the main injection amount) of fuel is injected in the first half of the expansion stroke after the injection of the main fuel for generating the engine output, and the high temperature cylinder is used. Post-inject into the room. This allows the post-injected fuel to burn and raise the exhaust temperature. On the other hand, since the exhaust temperature changes depending on the timing of post-injection as shown in FIG. 2 which will be described later in detail or the amount of fuel to be post-injected as shown in FIG. 3, control of the exhaust temperature by controlling this timing and amount. Is possible.

That is, as shown in FIG. 2, when the post-injection is performed in the first half of the expansion stroke (before ATDC 90 degrees) (post-injection a in FIG. 2), the fuel is injected to a place where the temperature in the cylinder chamber is sufficiently high. The post-injected fuel burns and the exhaust temperature rises accordingly. At that time, the temperature of the gas in the cylinder chamber expands as the piston descends until the exhaust valve opens, and the temperature drops. After the exhaust valve opens, the gas exits the cylinder chamber. The decrease is small and the exhaust temperature is high. When post-injection is performed in the first half of the expansion stroke, the exhaust temperature increases as the post-injection amount increases, as shown in FIG.

On the other hand, when the post-injection is performed in the latter half of the expansion stroke (after ATDC 90 degrees) (post-injection b in FIG. 2),
Since the fuel is injected to a place where the temperature inside the cylinder chamber is low, the post-injected fuel does not burn and the exhaust gas temperature does not rise so much. Therefore, by controlling the timing and amount of post-injection in the first half of the expansion stroke (before ATDC 90 degrees),
Exhaust temperature can be controlled. Other methods of raising the exhaust gas temperature include retarding the main fuel injection timing and fixing the post-injection amount and changing only the injection timing. It is not preferable in terms of fuel efficiency.

As described above, by controlling the exhaust gas temperature so that the exhaust gas temperature becomes a temperature suitable for the operation of the exhaust gas processing means, the purification efficiency can be greatly improved. As the exhaust treatment means, for example, an oxidation catalyst for purifying gas components in particulates, a filter with a catalyst for collecting and purifying particulates, a reduction catalyst for purifying NOx, or other harmful components in exhaust gas are purified. There are devices, etc.

According to the second aspect of the present invention, the particulates in the exhaust gas are collected by the filter with catalyst for collecting and purifying particulates. And, the particulates on the filter burn in the operating state where the exhaust gas temperature is high,
The filter is played. However, if the operating state where the exhaust gas temperature is low due to traffic congestion continues for a long time, the amount of particulate accumulation on the filter exceeds a predetermined value, the engine output decreases, and fuel consumption deteriorates.

Therefore, when the particulate accumulation amount on the filter exceeds a predetermined value and the exhaust gas temperature is below the predetermined value and regeneration of the filter cannot be expected, a small amount of fuel (for example, 5 to 20% of the main injection amount) is used. After the main fuel is injected to generate the engine output, it is post-injected into the high temperature cylinder chamber in the first half of the expansion stroke to raise the exhaust temperature. At this time, by controlling the timing and amount of post-injection, the exhaust gas temperature is adjusted to a temperature suitable for particulate combustion by the catalyst (for example, 4
The temperature can be set to 00 ° C. or higher), whereby particulates on the filter are burned and the filter is regenerated.

Further, according to the third invention of the present application, when the exhaust gas temperature is higher than a predetermined value (for example, 250 ° C.) which is the activation temperature of the reduction catalyst for NOx purification, the main fuel for generating engine output is After the injection, a very small amount (for example, 0.3 to 5% of the main injection amount) of fuel is post-injected into the cylinder chamber where the temperature has dropped in the latter half of the expansion stroke. In this case, since the temperature in the cylinder chamber is low, the fuel for the post-injection does not burn and is thermally decomposed to generate highly reactive hydrocarbons, and the hydrocarbons are mixed with the exhaust gas. Then, due to the action of this hydrocarbon, NOx contained in the exhaust gas can be effectively reduced and purified on the catalyst.

However, when the exhaust gas temperature is lower than a predetermined value, purification by a catalyst is impossible. Therefore, a smaller amount (for example, 5 to 20% of the main injection amount) of fuel is supplied to the cylinder chamber where the temperature in the first half of the expansion stroke is high. To post-inject. In this case, the post-injected fuel burns and the exhaust gas temperature rises. At this time, the NOx in the exhaust gas can be reduced and purified by controlling the timing and amount of the post-injection to set the exhaust gas temperature to a temperature (for example, 250 ° C. or higher) suitable for NOx purification by the catalyst.

In the fourth invention of the present invention, which has the particulate trapping means and the nitrogen oxide reducing means, the engine output is usually generated (when the particulate deposit amount on the filter is less than a predetermined value). After the main fuel is injected, a very small amount (for example, 0.3 to 5% of the main injection amount) of fuel is post-injected into the cylinder chamber where the temperature has dropped in the latter half of the expansion stroke. In this case, the fuel for the post-injection is thermally decomposed without burning to generate highly reactive hydrocarbons, and by mixing the hydrocarbons with the exhaust gas, NOx contained in the exhaust gas is catalytically converted. It can be satisfactorily reduced and purified. At the same time, the particulates in the exhaust gas are collected by the filter. And the particulates on the filter are
When the exhaust temperature becomes high, the combustion occurs and the filter is regenerated.

On the other hand, when the exhaust temperature is low and the operation is continued for a long time due to traffic congestion or the like, the amount of particulates accumulated on the filter exceeds a predetermined value, the output of the engine is reduced, and the fuel efficiency is deteriorated. Therefore, in the present invention, when the amount of particulates deposited on the filter exceeds a predetermined value and the exhaust gas temperature is below the predetermined value and regeneration of the filter cannot be expected,
A small amount (for example, 5 to 20% of the main injection amount) of fuel is post-injected into the cylinder chamber having a high temperature in the first half of the expansion stroke. In this case, the post-injected fuel burns and the exhaust gas temperature rises significantly. Then, by controlling the timing and amount of post-injection, the exhaust gas temperature can be set to a temperature suitable for particulate combustion by the catalyst (for example, 400 ° C. or higher), the particulates on the filter can be burned, and the filter can be regenerated. As described above, according to the fourth aspect of the present invention, both NOx and particulates can be efficiently purified with a simple structure without adding a particularly complicated member.

According to the fifth aspect of the invention, the timing of the post-injection performed in the latter half of the expansion stroke to supply the reducing agent to the NOx catalyst is changed according to the exhaust gas temperature, so that the optimum exhaust gas temperature can be obtained. It is possible to supply the catalyst with fuel of the degree of decomposition (the number of carbon atoms of the hydrocarbon used as the reducing agent),
The NOx reduction purification efficiency can be significantly improved. That is, as shown in FIG. 19 which will be described in detail later, when hydrocarbon is supplied as the reducing agent, the NOx reduction purification efficiency by the catalyst reaches a peak at a certain temperature, and the temperature at which the peak purification rate is obtained is the reducing agent (carbonization). Hydrogen) depends on the carbon number. And, the temperature increases as the carbon number increases. Therefore, for example, at temperature T1 (low temperature), using hydrocarbon A having a small number of carbons as a reducing agent has a higher NOx reduction purification efficiency than using B having a large number of carbons, but at temperature T2 (high temperature where T1 <T2). On the contrary, the efficiency is higher when B having a large carbon number is used.

On the other hand, if the post-injection timing is always constant as is done in the conventional device, when the exhaust temperature is high, the decomposition degree is large (the carbon number is small) and the NOx purification efficiency is high at a low temperature. Is only supplied to obtain
On the contrary, when the exhaust gas temperature is low, only hydrocarbons that can obtain high NOx purification efficiency at high temperature (high carbon number) are supplied. Therefore, a fuel having a decomposition degree suitable for each temperature cannot be supplied, and high NOx reduction purification efficiency cannot be obtained.

On the other hand, it is known that the number of carbon atoms of the thermally decomposed fuel (hydrocarbon) obtained by the post injection in the latter half of the expansion stroke varies depending on the post injection timing, as shown in FIG. That is, the later the injection timing, the lower the temperature in the cylinder chamber and the subsequent injection, so the degree of thermal decomposition of the fuel becomes small, and the number of carbon atoms of the obtained hydrocarbon becomes large.
Therefore, in the fifth aspect of the invention, the injection timing for post-injection is changed according to the exhaust gas temperature, and the higher the exhaust gas temperature, the later the post-injection timing is delayed to supply the reducing agent having a large carbon number. As a result, the catalyst can always be used in a state where the NOx reduction efficiency is high, regardless of the exhaust temperature. Therefore, with a simple configuration, N
Both Ox and particulates can be efficiently purified.

On the other hand, in the sixth aspect of the invention, in the fourth and fifth aspects of the invention, the post-injection is carried out only in the first half of the expansion stroke when the particulate deposit amount exceeds the predetermined value and the exhaust temperature is below the predetermined value. The reason is as follows. Depending on the operating conditions, when the post-injection in the first half of the expansion stroke raises the exhaust gas temperature and then the post-injection is carried out in the latter half of the expansion stroke, the post-injected fuel burns and is an effective reducing agent. The hydrocarbon cannot be supplied. When importance is placed on avoiding such a situation, it is preferable to stop the post-injection of the fuel in the latter half of the expansion stroke and only perform the post-injection in the first half of the expansion stroke as in the present invention.

In the above inventions, when the post-injection is performed, if only the specific cylinders of the entire cylinders (N cylinders) are made to collectively inject the post-injection amount for N cylinders, the post-injection amount Becomes N times, and it becomes unnecessary to make the injection amount extremely small. As a result, actuators such as solenoid valves do not require extremely high responsiveness, control is easy, and cost reduction and actuator volume reduction are possible compared to conventional cases. Further, it is possible to absorb the variation in the injection amount between the nozzles of each cylinder, which is noticeable in the case of a very small amount of injection. Moreover, since the number of times the injection nozzle is seated can be reduced, the durability of the nozzle seat can be greatly improved.

Further, each cylinder or a specific cylinder injects the post-injection amount for M cycles collectively at a rate of once in M cycles (M ≧ 2), and the cylinders to be post-injected are sequentially changed. As a result, it is possible to obtain the further effect of absorbing the variation in the injection amount and improving the durability of the nozzle sheet portion. Further, as will be known by the embodiments described later, each invention of the present application can be realized by a simple configuration without newly adding a complicated member.

[0038]

As described above, according to the invention of the present application, there is provided an exhaust emission control device for an internal combustion engine such as a diesel engine, which is capable of efficiently purifying particulates or nitrogen oxides with a simple structure. be able to.

[0039]

【Example】

Example 1 A first example of the present invention applied to a 4-cylinder diesel engine will be described with reference to FIG. In this example, as shown in FIG. 1, a fuel injector 13 and a solenoid valve 14 as fuel injection means provided for each cylinder, and an exhaust passage 16 are provided.
An exhaust treatment device 17 interposed therein, a rotation sensor 30,
The ECU 18 as an operating state detecting means for detecting the operating state using the load sensor 31 and the pressure sensor 32, the ECU 18 as the exhaust temperature estimating means for estimating the exhaust temperature based on the information of the operating state detecting means, and the estimated exhaust gas ECU 18 as a temperature comparison means for comparing the temperature with a predetermined value
And an exhaust gas purification device 1 for an internal combustion engine (diesel engine) 10 having an ECU 18 as a fuel injection control means for determining the fuel injection timing and the fuel injection amount based on the result of the temperature comparison means and operating the fuel injection means. . When the exhaust gas temperature is equal to or lower than a predetermined value, the fuel injection control means commands the post-injection of fuel after the main fuel injection for generating the engine output, thereby making the exhaust gas temperature suitable for the operation of the exhaust gas processing means 17. Control in range.

Each of these will be described in detail below. As shown in FIG. 1, the diesel engine 10 and the exhaust emission control device 1 are provided with four cylinder bores, in which pistons are fitted so as to be reciprocally slidable, and cylinder blocks 11 and cylinders each having a cylinder chamber are formed. A cylinder head 12 mounted on the block 11 and having its cylinder chambers closed, a crankshaft having its pistons connected by a connecting rod, a valve mechanism for opening and closing intake and exhaust valves, and a cylinder corresponding to the cylinder chambers. Four fuel injectors 13 as fuel injection means installed in the head 12, four solenoid valves 14 mounted on the fuel injector 13, and a feed pump 15 for supplying fuel from a fuel tank (not shown) to the fuel injector 13. Exhaust treatment provided in the exhaust passage 16 Location 17, and an ECU (central control unit) 18 having a fuel injection control unit to perform the main fuel injection and post-fuel injection in the fuel injector 13 by opening and closing the solenoid valve 14 or the like.

The ECU 18 is connected to its input circuit with a rotation sensor 30, a load sensor 31, and a pressure sensor 32, which form an operating condition detecting means, and has its output circuit connected to the solenoid valve 14.
To be electrically connected. Then, the engine speed, the engine load, and the fuel injection pressure detected by the sensors 30 to 32 are collated with the fuel injection pattern previously input to the memory, and the solenoid valve 14 is opened / closed based on the result. The ECU 18 also has a comparison circuit that calculates the exhaust temperature based on the output signals of the rotation sensor 30 and the load sensor 31, and compares this value with a predetermined value. The rotation sensor 30 is arranged on the crankshaft, the load sensor 31 is arranged on an accelerator pedal (not shown), and the pressure sensor 32 is arranged on the fuel header 22.

The feed pump 15 is connected to the fuel injector 13 via a fuel header 22 via fuel pipes 21 and 23. Therefore,
The insides of the pipes 21 and 23 and the fuel header 22 are always kept at a high pressure by the operation of the feed pump 15. Then, in response to a command from the ECU 18, the high-pressure fuel is injected from the fuel injector 13 into the cylinder chamber only when the normally closed solenoid valve 14 is opened. That is, the main injection for generating the engine output and the post-injection for increasing the purification efficiency are operated by a common device.

The exhaust treatment device 17 includes the following. For example, a wash coat layer such as alumina is provided on the surface of a carrier such as ceramics, and Pt, Pd, R
There is an oxidation catalyst that carries a noble metal catalyst such as h to purify the gas component in the particulates. Alternatively, a large number of channels are formed by a honeycomb lattice made of a porous material such as ceramic, and the inlets and outlets of the channels are alternately closed by a blocking material, and a washcoat layer of alumina or the like is provided on the surface thereof. , Precious metals such as Pt and Pd or C
There is a filter with a catalyst for collecting and purifying particulates that carries a base metal catalyst such as u. Alternatively, there is a NOx catalyst or the like in which a carrier such as ceramics carrying, for example, Cu-zeolite or Pt-zeolite capable of reducing and purifying NOx in the presence of a reducing agent even in an oxygen excess atmosphere such as in diesel exhaust.

Next, the function and effect of this example will be described.
In the exhaust emission control device 1 configured as described above, the ECU
When the exhaust temperature obtained from the operating conditions detected by the rotation sensor 30 and the load sensor 31 is equal to or lower than the activation temperature of the catalyst in the exhaust treatment device 17, 18 is the first half of the expansion stroke after the main fuel injection for engine output generation. (For example, ATDC40
A small amount (for example, 5 to 20% of the main injection amount)
Command to post-inject the fuel. Then, the post-injected fuel burns and the exhaust gas temperature can be raised.

Since the exhaust temperature changes depending on the timing of post-injection as shown in FIG. 2 or the amount of post-injection as shown in FIG. 3, it is possible to control the exhaust temperature by controlling this timing and amount. Is. That is, FIG.
When the post-injection is performed in the first half of the expansion stroke (before ATDC 90 degrees) as indicated by the symbol a in (a), the fuel is injected to a place where the temperature inside the cylinder chamber is sufficiently high, so the post-injected fuel burns, and The exhaust gas temperature rises as shown in FIG. At that time, the gas in the cylinder chamber expands as the piston descends until the exhaust valve opens, and the temperature drops. After the exhaust valve opens, the gas exits from the cylinder chamber. Becomes smaller and the exhaust temperature becomes higher.

When post-injection is performed in the first half of the expansion stroke, the exhaust temperature rises as the post-injection amount increases, as shown in FIG. However, when the post-injection is performed in the latter half of the expansion stroke (after ATDC 90 degrees) as indicated by the symbol b in FIG. 2 (a), the post-injected fuel is injected because the fuel is injected to a place where the temperature in the cylinder chamber is low. It does not burn, so the exhaust temperature does not rise. Therefore, in the first half of the expansion stroke (before ATDC 90 degrees), the exhaust temperature can be controlled by controlling the timing and amount of post-injection. Then, by setting the exhaust temperature to a temperature suitable for the operation of the exhaust processing means,
The purification efficiency can be greatly improved.

Next, a method of controlling the post-injection timing and amount in the exhaust purification system 1 will be described with reference to the flowchart shown in FIG. In this example, the case where the post-injection timing and amount are controlled based on the exhaust gas temperature t obtained based on the outputs of the rotation sensor 30 and the load sensor 31 has been described.
The exhaust temperature may be directly detected as shown in FIG. First, S
In (step) 101, the exhaust gas temperature t obtained by the ECU 18 is read based on the outputs of the rotation sensor 30 and the load sensor 31. Since the exhaust gas temperature t is determined by the engine speed and the engine load, as shown in FIG. 4, for example, the exhaust gas temperature can be obtained by storing it in the ECU 18 in advance.

Then, in S102, this t is compared with the set value t1 which is the activation temperature of the catalyst. If the exhaust temperature t is higher than t1, the condition is not satisfied, so S10
Return to 1. On the other hand, when the exhaust gas temperature t is lower than the above-mentioned t1, the exhaust gas purification by the catalyst cannot be expected. Therefore, the routine proceeds to S103, where the post injection timing and the post injection amount for temperature rise are determined.
The timing and amount are stored in advance in the ECU 18,
Accordingly, the fuel injection timing and the fuel injection amount are determined so that the exhaust temperature suitable for the operation of each processing device 17 is obtained.

In S104, a small amount of fuel is post-injected in the first half of the expansion stroke after the main fuel injection for engine output generation, for example, as shown in FIG. 6, and the process returns to S101. However, if post-injection is performed more than necessary, fuel efficiency will deteriorate, so the above cycle is executed once per second, for example, and S1
If the exhaust temperature becomes higher than the set value t1 in 02, the post-injection is immediately stopped in S105. As described above, according to this example, it is possible to provide an exhaust emission control device for a diesel engine that can control the exhaust temperature and efficiently purify particulates, nitrogen oxides, and the like.

Embodiment 2 As shown in FIG. 7, this embodiment is another embodiment in which the temperature sensor 33 is provided in the exhaust pipe 16 upstream of the exhaust treatment device 17 in FIG. 1 showing the structure of the embodiment 1. Here is an example. The temperature sensor 33 is electrically connected to the input circuit of the ECU 18. That is, in the first embodiment, the exhaust temperature t is obtained based on the outputs of the rotation sensor 30 and the load sensor 31, but in the present embodiment, the temperature sensor 33 directly detects the exhaust temperature. As a result, the exhaust temperature in a transient state of the engine can be grasped more accurately, so that control with higher accuracy becomes possible. Others are the same as in the first embodiment.

Embodiment 3 This embodiment is an example in which a filter with catalyst 171 is used as the exhaust treatment device 17 in FIG. 1 or 7 as shown in FIG. 8 and FIG. Furthermore, in addition to the configuration of FIG.
The pressure sensor 35 is electrically connected to the input circuit. Further, the ECU 18 calculates the amount of particulate accumulation on the catalyst-equipped filter 171 based on the engine speed, the engine load, and the pressure upstream of the filter detected by the sensors 30, 31, and 35, and compares it with a predetermined value. Then, the solenoid valve 14 is opened / closed based on the result and the detected or estimated exhaust gas temperature. The pressure sensor 35 is arranged in the exhaust pipe 16 upstream of the filter 171 with catalyst.

The catalyst-equipped filter 171 has a large number of channels formed by a honeycomb lattice made of a porous material such as ceramics, and the inlets and outlets of the channels are alternately closed by a blocking material. Then, a washcoat layer of alumina, for example, is provided on the surface of the Pt or P layer.
It carries a noble metal such as d or a base metal catalyst such as Cu. As a result, the particulate combustion temperature during filter regeneration can be lowered.

Next, the function and effect of this example will be described.
In the exhaust emission control device 1 configured as described above, when particulates are deposited on the filter 171 with catalyst, the flow path is clogged, and the pressure detected by the pressure sensor 35 increases. Based on the outputs of the pressure sensor 35 and the rotation sensor 30 and the load sensor 31, the ECU
At 18, the particulate deposition amount in the filter with catalyst 171 is calculated.

Then, the accumulated amount is compared with a predetermined value, exceeds a set value (for example, 10 g) that requires combustion removal of particulates, and the rotation sensor 30 and the load sensor 3
The exhaust gas temperature obtained by the ECU 18 from the operating condition detected in 1 is the particulate combustion temperature by the catalyst (for example, 4
If the temperature is lower than 00 ° C), in order to forcibly regenerate the filter 171 with catalyst, a small amount (for example, main injection) in the first half of the expansion stroke (for example, ATDC 40 to 90 degrees) after main fuel injection for generating engine output is performed. 5-20% of the fuel amount) is post-injected. In this case, the post-injected fuel burns in the cylinder chamber where the temperature is still high and the exhaust gas temperature rises significantly, so the particulates on the filter burn and the filter with catalyst 1
71 is reproduced.

Since the exhaust gas temperature is high when the vehicle is traveling at high speed, the catalyst-equipped filter 171 can be regenerated without post-injection in the first half of the expansion stroke. Next, a method of controlling the post injection timing and amount in the above exhaust purification device will be described with reference to the flowchart shown in FIG. In this example,
An example in which the timing and amount of post-injection are controlled based on the particulate matter accumulation amount m in the filter with catalyst 171 and the exhaust gas temperature t calculated by the ECU 18 will be described.

First, in S (step) 201, E
The particulate deposition amount m in the filter with catalyst 171 calculated in the CU 18 is read. Next, S20
In 2, the m is compared with a set value m1 (for example, 10 g) that requires the removal of particulates. If it is smaller than m1, it is not necessary to regenerate the filter with catalyst 171 and the process returns to S201. On the other hand, the amount of particulate accumulation m
Is larger than the above-mentioned m1, the routine proceeds to S203, where the exhaust temperature t obtained by the ECU 18 is read based on the outputs of the rotation sensor 30 and the load sensor 31.

Then, in S204, this t is set to the set value t2 which is the temperature at which particulate combustion by the catalyst is possible.
(For example, 400 ° C.). When the exhaust gas temperature t is higher than t2, the high temperature exhaust gas causes the filter with catalyst 17
Since the particulates above 1 burn, the process returns to S201. On the other hand, when the exhaust temperature t is lower than the above t2, S
The routine proceeds to 205, where the timing of the post injection and the post injection amount are determined. This value is stored in the ECU 18 in advance and is determined to be a value that allows the particulate combustion temperature (for example, 400 ° C.) by the catalyst to be obtained in accordance with this value.

In step S206, the exhaust temperature is raised by post-injecting a small amount of fuel in the first half of the expansion stroke after main fuel injection for generating engine output, for example, as shown in FIG. Burn the particulates on 171. Then, in S207, the particulate deposition amount m on the filter is read again, and S20
In step S8, a comparison is made with a set value m2 (for example, 0.5 g) of the particulate accumulation amount that is a reference for completion of filter regeneration, and if the filter regeneration is insufficient, the above S20 is performed.
Returning to step 6, when the regeneration is completed, the post injection is stopped in step S209, and the process returns to step S201. The above cycle is executed once per second, for example. In the present embodiment, the exhaust temperature may be directly detected and controlled by the temperature sensor 33 as in the second embodiment. In this case, as shown in FIG. 10, the temperature sensor 33 is provided upstream of the filter 171 with catalyst.
Is arranged.

Embodiment 4 As shown in FIG. 11, this embodiment is another embodiment in which a NOx catalyst 172 is used as the exhaust treatment device 17 in the configuration shown in FIG. The NOx catalyst 172 carries a catalyst such as Cu-zeolite or Pt-zeolite capable of reducing and purifying NOx in the presence of a reducing agent in an oxygen excess atmosphere such as diesel exhaust in the presence of a reducing agent. Then, by supplying the reducing agent, NOx can be purified.

Next, the function and effect of this example will be described.
Exhaust temperature is a certain value (eg 25
Higher than 0 ° C), after injection of the main fuel to generate engine output, a very small amount (for example, 0.3 to 5% of the main injection amount)
Fuel of the latter half of the expansion stroke (for example, ATDC 90-13
Post-injection into the cylinder chamber where the temperature (0 degree) has decreased. In this case, the fuel for the post-injection is pyrolyzed without combustion because the temperature in the cylinder chamber is low to generate highly reactive hydrocarbons, and the hydrocarbons are mixed with the exhaust gas. Therefore, NOx contained in the exhaust gas can be reduced and purified on the catalyst.

However, if the exhaust temperature is lower than a predetermined value, purification by a catalyst is impossible, and therefore a smaller amount (for example, 5 to 20% of the main injection amount) of fuel is used in the first half of the expansion stroke (for example, ATDC 40 to 90 degrees). ) Is post-injected into the cylinder chamber whose temperature is high. In this case, the post-injected fuel burns and the exhaust gas temperature rises. Then, by controlling the timing and amount of post-injection, it becomes possible to set the exhaust temperature to a temperature suitable for NOx purification by a catalyst (for example, 250 ° C. or higher), and it is possible to efficiently reduce and purify NOx in the exhaust. it can.

Next, a method of controlling the post injection timing in the above exhaust purification device will be described with reference to the flowchart shown in FIG. In this example, the rotation sensor 30, the load sensor 31
The case where the post injection timing and amount are controlled based on the exhaust temperature t obtained based on the output of First, in S (step) 301, after injection of the main fuel for generating the engine output, a very small amount of fuel is post-injected in the latter half of the expansion stroke as shown in FIG. 13 (post-injection c in FIG. 13).

Next, in S302, the rotation sensor 30,
The exhaust gas temperature t obtained by the ECU 18 is read based on the output of the load sensor 31. Then, in S303, this t
Is compared with a set value t3 which is the activation temperature of the catalyst. If the exhaust temperature t is higher than t3, the process returns to S302. on the other hand,
If the exhaust gas temperature t is lower than the above-mentioned t3, exhaust gas purification by the catalyst cannot be expected, so the routine proceeds to S304, where the post injection timing and amount are determined. This value is stored in advance in the ECU 18, and the activation temperature of the catalyst (for example, 2
The post-injection timing and amount are determined so as to obtain (50 ° C.).

Then, in S305, for example, as shown in FIG.
As shown in FIG. 4, a smaller amount of fuel is post-injected in the first half of the expansion stroke after the main fuel injection for generating engine output (post-injection d in FIG. 14), and the process returns to S302. It should be noted that if post-injection is performed more than necessary, fuel efficiency deteriorates. Therefore, if the exhaust gas temperature exceeds the set value t3 in S303, the post-injection in the first half of the expansion stroke is stopped in S306 and the process returns to S302. The above cycle is executed once per second, for example. In this example as well, similarly to the above, the temperature sensor 33 may directly detect the exhaust temperature and control it. The configuration in this case is shown in FIG.

Embodiment 5 The purifying apparatus 1 of this embodiment has the same construction as that of Embodiment 3 shown in FIG. 8, and is another embodiment in which the control algorithm is changed as shown in FIG. The catalyst-equipped filter 171 has a large number of channels formed by a honeycomb lattice made of a porous material such as ceramic, and the inlets and outlets of the channels are alternately closed by a blocking material.
A layer of alumina or zeolite, for example, is provided on the surface thereof, and a precious metal such as Pt or Pd or a base metal catalyst such as Cu is supported on the surface of the catalyst. NOx in
Can be reduced and purified, and the combustion temperature of particulates at the time of filter regeneration can be lowered.

Next, the function and effect of this example will be described.
In the exhaust emission control device configured as described above, when the amount of particulates accumulated on the catalyst-equipped filter 171 is small and there is no need to regenerate the filter, after injection of main fuel for engine output generation as in the fourth embodiment. A very small amount (for example, 0.3 to 5% of the main injection amount) of fuel is post-injected in the latter half of the expansion stroke (for example, ATDC 90 to 130 degrees). As a result, NOx can be reduced and purified on the catalyst.

On the other hand, the amount of accumulation exceeds the set value (for example, 10 g) that requires the combustion and removal of particulates, and the exhaust temperature obtained by the ECU 18 from the operating conditions detected by the rotation sensor 30 and the load sensor 31 is the catalyst. If the particulate combustion temperature is lower than the particulate combustion temperature (for example, 400 ° C.) due to, the catalyst-equipped filter 171 is forcibly regenerated, similarly to the third embodiment, the first half of the expansion stroke (for example, ATDC4).
0 to 90 degrees) in a small amount (for example, 5 to 20% of the main injection amount)
Post-inject the fuel. As a result, the exhaust gas temperature rises, so that the particulates on the filter burn and the catalyst-equipped filter 171 is regenerated.

Next, a method of controlling the post injection timing and the injection amount in the exhaust gas purification device 1 will be described with reference to the flow chart shown in FIG. In this example, a case is shown in which the post-injection timing and amount are controlled based on the particulate matter accumulation amount m in the filter with catalyst 171 and the exhaust gas temperature t calculated by the ECU 18. First, S (step) 40
In No. 1, a very small amount of fuel is post-injected in the latter half of the expansion stroke after the main fuel injection for generating engine output.

Then, the process proceeds to S402, and the particulate matter accumulation amount m in the filter with catalyst 171 calculated by the ECU 18 is read. Next, in S403,
This m is compared with a set value m1 (for example, 10 g) that requires combustion removal of particulates. If it is smaller than m1, it is not necessary to regenerate the filter with catalyst 171 so that S4 is performed.
Return to 01. On the other hand, the particulate deposition amount m is
If it is greater than 1, the process proceeds to S404, where the rotation sensor 30,
The exhaust gas temperature t obtained by the ECU 18 is read based on the output of the load sensor 31.

In step S405, the exhaust temperature t is set to the set value t1 which is the particulate combustion temperature by the catalyst.
(For example, 400 ° C.). When the exhaust temperature t is higher than t1, the high temperature exhaust causes the filter 17 with catalyst.
Since the particulates above 1 burn, S4 remains
Return to 01. On the other hand, when the exhaust temperature t is lower than the above-mentioned t1, in S406, a small amount of fuel is post-injected in the first half of the expansion stroke after the main fuel injection for generating the engine output. Then, the exhaust gas temperature is raised by this, and the particulates on the filter 171 with catalyst are burned.

In subsequent S407, the particulate accumulation amount m on the filter is read again, and in S408, the particulate accumulation amount set value m2 (for example, 0.5 g) for ending the regeneration of the filter is compared, and the filter regeneration is not completed yet. If it has not ended, the process returns to S406, and if the regeneration has ended, in S409, the post injection in the first half of the expansion stroke is stopped and the process returns to S401. The above cycle is executed once per second, for example. In this example as well, similarly to the above, the temperature sensor 33 may directly detect the exhaust temperature and control it. The configuration in this case is similar to that shown in FIG.

Embodiment 6 This embodiment is another embodiment in which, as shown in FIG. 17, two exhaust treatment means of the filter with catalyst 174 and the NOx catalyst 173 are provided in Embodiment 5. That is, in Example 5, both the reduction purification of NOx and the collection / incineration purification of particulates were performed in the filter 171 with catalyst. On the other hand, in this example, the reduction purification of NOx is N
The Ox catalyst 173 is used to collect and incinerate particulates by a filter with catalyst 174 provided downstream of the NOx catalyst 173.

The catalytic converter 173 is made of a carrier such as ceramic, and a catalyst such as Cu-zeolite or Pt-zeolite capable of reducing and purifying NOx even in an oxygen excess atmosphere such as diesel exhaust in the presence of a reducing agent. . On the other hand, the catalyst-equipped filter 174 has a large number of channels formed by a honeycomb lattice made of a porous material such as ceramic, and the inlets and outlets of the channels are alternately closed by a blocking material. A washcoat layer of alumina, for example, is provided on the surface thereof, and carries a noble metal such as Pt or Pd or a base metal catalyst such as Cu.

As a result, the catalyst 1 more suitable for the respective purposes of NOx reduction and particulate oxidation.
73 and 174 can be used, and more efficient purification can be achieved for both components. In this example as well, similarly to the above, the temperature sensor 33 may directly detect the exhaust temperature and control it. The configuration in this case is as shown in FIG. Others are the same as in the fifth embodiment.

Example 7 This example is the same as Example 4 shown in FIGS. 11 and 15 and FIGS.
In the same configuration as the fifth embodiment shown in FIG. 0 or the sixth embodiment shown in FIGS. 17 and 18, for supplying hydrocarbon (pyrolysis fuel) as a reducing agent for NOx purification to the catalyst, This is another embodiment in which the timing of the post-injection performed in the latter half of the expansion stroke is changed according to the exhaust gas temperature detected by the temperature estimation means or the temperature sensor 33. FIG.
As shown by the broken line or the solid curve, the NOx reduction purification efficiency by the catalyst peaks at a certain temperature when hydrocarbon is supplied as the reducing agent, and the purification efficiency decreases at higher or lower temperatures.

The temperature at which the peak purification rate is obtained depends on the carbon number of the reducing agent (hydrocarbon), and becomes higher as the carbon number increases. Therefore, the temperature T1 (for example, 35
At 0 ° C., using hydrocarbon A having a small carbon number (for example, having 5 or less carbon atoms) as a reducing agent has higher NOx reduction purification efficiency than using B having a large carbon number (for example, having 10 or more carbon atoms), but temperature On the contrary, at T2 (for example, 400 ° C.), the efficiency becomes higher when B having a large carbon number is used. On the other hand, if the post-injection timing is always constant as in the conventional device, when the exhaust temperature is high, the degree of decomposition is large (the carbon number is small), and only hydrocarbons that provide high NOx purification efficiency at low temperatures are supplied, On the contrary, when the exhaust gas temperature is low, only hydrocarbons that can obtain high NOx purification efficiency at high temperature (high carbon number) are supplied.

Therefore, a fuel having a decomposition degree suitable for each temperature cannot be supplied, and a high NOx reduction purification efficiency cannot be obtained. On the other hand, the carbon number of the thermally decomposed fuel (hydrocarbon) obtained by the post injection in the latter half of the expansion stroke varies depending on the post injection timing as shown in FIG. That is,
The later the injection timing, the lower the temperature in the cylinder chamber and the subsequent injection, so the degree of thermal decomposition of the fuel decreases and the number of carbon atoms in the obtained hydrocarbon increases. Therefore, in this example, a hydrocarbon having a carbon number (thermally decomposed fuel) that maximizes the NOx reduction purification efficiency of the catalyst according to the exhaust temperature is supplied as the reducing agent.

That is, since the optimum carbon number of the reducing agent varies depending on the exhaust temperature, the injection timing of the post-injection is changed according to the exhaust temperature, and the post-injection timing is delayed as the exhaust temperature becomes higher, and the reducing agent having a large carbon number is changed. To supply. As a result, when the exhaust temperature is low, the NOx reduction purification efficiency of the catalyst is high at low temperatures, and the carbon number is small (for example, 5 or less).
When the exhaust gas temperature is high, hydrocarbons having a high carbon number (for example, 10 or more) with high NOx reduction purification efficiency of the catalyst at high temperature are supplied.

Further, the timing of the post-injection at that time is changed in multiple steps or continuously with respect to the exhaust gas temperature.
As a result, the catalyst can always be used in a state where the NOx reduction efficiency is high regardless of the exhaust temperature, and the NOx reduction purification efficiency of the catalyst can be greatly improved. The optimum post-injection pattern for each exhaust gas temperature in this example is stored in advance in the ECU 18, and is determined in the ECU 18 based on the exhaust gas temperature. Others are the same as in Example 4, Example 5, or Example 6.

Next, an example in which the method for controlling the post-injection timing in the above exhaust purification system is applied to the fifth embodiment shown in FIG. 8 will be described with reference to the flowchart shown in FIG. In this flowchart, an example is shown in which the post injection timing and amount are controlled based on the particulate matter accumulation amount m in the filter 171 with catalyst and the exhaust gas temperature t calculated by the ECU 18.

First, at S (step) 501, the ECU 1 based on the outputs of the rotation sensor 30 and the load sensor 31.
The exhaust temperature t obtained in 8 is read, and the post injection timing is determined in the ECU 18 based on the exhaust temperature as shown in FIG. 22, for example. Based on this, in S502, an extremely small amount of fuel is post-injected in the latter half of the expansion stroke after the main fuel injection for generating the engine output. Then, the process proceeds to S503 and EC
The particulate deposit amount m in the filter with catalyst calculated in U18 is read.

Next, in S504, this m is compared with a set value m1 (for example, 10 g) that requires combustion removal of particulates. If it is smaller than m1, it is not necessary to regenerate the filter with catalyst, and the process returns to S501. On the other hand, if the particulate deposition amount m is larger than the above m1, S
505, the exhaust gas temperature t read in S501
Is a set value t which is the particulate combustion temperature by the catalyst
1 (for example, 400 ° C.). Exhaust temperature t is t1
If it is larger, the particulate matter on the filter with catalyst burns due to the high temperature exhaust gas, and therefore, as it is in S501.
Return to.

On the other hand, when the exhaust gas temperature t is lower than the above t1, in S506, a small amount (for example, the main injection amount of 5
(~ 20%) fuel is post-injected to raise the exhaust gas temperature and burn the particulates on the catalyst-equipped filter 171. Then, in step S507, the particulate accumulation amount m on the filter is read again, and in step S508, the particulate accumulation amount set value m2 (for example, 0.5 g) for ending the filter regeneration is compared, and the filter regeneration is still completed. If not, the process returns to S506, and if the regeneration is completed, the post injection in the first half of the expansion stroke is stopped in S509, and the process returns to S501. The above cycle is executed once per second, for example.

If the above control is applied to the sixth embodiment shown in FIG. 17, it becomes possible to more efficiently purify NOx and particulates. Note that the temperature sensor 33 (FIGS. 10, 15, and 18) is similarly used in this example.
The exhaust gas temperature may be directly detected and controlled by. The effect in this case is as described above.

Example 8 This example is the same as Example 5, Example 6, and Example 7.
This is another embodiment in which the post-injection is stopped in the latter half of the expansion stroke and the post-injection is carried out only in the first half of the expansion stroke when the particulate accumulation amount exceeds the predetermined value and the exhaust gas temperature is below the predetermined value. . That is, Example 5,
In Example 6 and Example 7, when the particulate deposition amount exceeds the set value and the exhaust temperature is equal to or less than the set value, in addition to the extremely small amount of post-injection in the latter half of the expansion stroke, a small amount in the first half of the expansion stroke is used. Is post-injected (see FIG. 14). On the other hand, in this example, in this case, the extremely small amount of post-injection in the latter half of the expansion stroke is stopped and a small amount of fuel is post-injected only in the first half of the expansion stroke (see FIG. 6).

This is because when the post-injection in the latter half of the expansion stroke is continuously performed in the cylinder chamber where the exhaust gas temperature has risen due to the post-injection in the first half of the expansion stroke, the post-injection portion in the latter half of the expansion stroke is also exhausted depending on the operating conditions. This is because combustion may occur due to the temperature rise and an effective reducing agent may not be supplied to the NOx catalyst. Therefore, when there is a concern about such engine operation, priority is given to suppression of deterioration of fuel consumption, and as shown in FIG. 6, only post-fuel injection in the first half of the expansion stroke is performed.

Next, FIG. 23 shows a method of controlling the post-injection timing in the above exhaust purification device. This is S405 of the flowchart of FIG. 16 in the fifth and sixth embodiments.
S601 is added between S406 and S406. When this example is applied to the seventh embodiment, S5 in FIG.
S601 is added between 05 and S5O6. And S
At 601, the post injection in the latter half of the expansion stroke is stopped. In this example as well, the temperature sensor 3
Alternatively, the exhaust temperature may be directly detected by 3.

Embodiment 9 This embodiment is another embodiment of Embodiments 1 to 8 in which the post-injection is carried out only in a specific cylinder. That is, in Examples 1 to 8, the post-injection for controlling the exhaust gas temperature or supplying the reducing agent to the catalyst is always performed in all cylinders, whereas in this example, this is performed only in a specific cylinder. To do.

The post-injection in the latter half of the expansion stroke for supplying the reducing agent to the NOx catalyst will be described below as an example. As shown in FIG. 29, the conventional device has an extremely small amount of fuel (for example, main injection) after the main injection is completed. (0.3-3% of the amount) was post-injected and was constantly injected in all cylinders. After this injection,
Since it is for supplying hydrocarbons (thermally decomposed fuel) as a reducing agent to the catalyst, N
Although it is indispensable for reducing and purifying Ox, the fuel amount used for the post-injection deteriorates the fuel efficiency, so it is very important to control the amount thereof with a very small amount with high accuracy.

Therefore, in the past, an electromagnetic valve having an extremely high response was required to control the extremely small amount of after injection. Therefore, the cost and volume of the solenoid valve have increased. On the other hand, in this example, the post-injection is performed as shown in FIG.
As shown in, the operation is performed only in the first cylinder. That is, by performing the post-injection for four cylinders only in the first cylinder, the post-injection amount can be made four times the post-injection amount in the first cylinder in the conventional method. Therefore, it is not necessary to control an extremely small amount of post-injection as compared with the conventional case, so that extremely fast responsiveness is not required for the solenoid valve 14, and the cost and size can be greatly reduced.

Further, since it is possible to absorb the variation in the injection amount between the nozzles of each cylinder, which becomes remarkable in the control of the injection of a very small amount, it is possible to obtain stable performance. Further, in the second to fourth cylinders that do not perform the post injection, the number of seats of the injection nozzle can be reduced as compared with the conventional case, so that the durability of the nozzle seat portion can be significantly improved. Above, the first
The case where the post-injection is performed only in the cylinder has been described as an example, but this may be performed in one cylinder or a plurality of cylinders other than that.

In the above description, the post-injection in the latter half of the expansion stroke in the case of supplying the reducing agent necessary for NOx purification has been described as an example. This is because the exhaust temperature is raised and the particulate matter on the filter with catalyst is increased. It goes without saying that the present invention can also be applied to the post-injection in the first half of the expansion stroke, such as in the case of burning.

In that case, for example, in the case of the fifth embodiment,
When the particulate accumulation amount exceeds the set value and the exhaust temperature is below the set value, both the very small amount of post-injection in the latter half of the expansion stroke and the small amount of post-injection in the first half of the expansion stroke are performed only by the first cylinder. In addition to the method performed in the pattern shown in FIG. 14, for example, a very small amount of post-injection in the latter half of the expansion stroke is performed in the first cylinder in FIG.
Alternatively, the small amount of post-injection in the first half of the expansion stroke may be performed in the second cylinder in the pattern shown in FIG.

As a result, the number of times the injection nozzle of the first cylinder is seated can be reduced, and the durability of the nozzle seat portion can be greatly improved. This is also the case when applied to other embodiments. In the above description, the case where the post-injection is performed only in the first cylinder or the second cylinder has been described.
It may be performed in a cylinder or a plurality of cylinders.

Embodiment 10 In this embodiment, as shown in FIG. 25, in the embodiment 9, the post-injection is performed once every M cycles (M ≧ 2, for example, 4). Is. That is, in the first cylinder, the conventional M × 4 post-injections are collectively performed once every M cycles. As a result, the requirement for responsiveness to the solenoid valve 14 described in the first embodiment can be further reduced. Although the case where the post-injection is performed only in the first cylinder has been described above as an example, this may be performed in one cylinder or a plurality of other cylinders. Also, as in Example 9,
The post-injection in the latter half of the expansion stroke and the post-injection in the first half of the expansion stroke may be performed in different cylinders or a plurality of cylinders.

Embodiment 11 In this embodiment, as shown in FIG. 26, in the above-mentioned Embodiments 9 and 10, the post-injection carried out only in the first cylinder or a specific cylinder is carried out by sequentially switching to other cylinders. This is an example of doing so. That is, for example, the first to fourth cylinders collectively carry out post-injection for four cylinders once every four cycles, and the cylinders that perform this post-injection are called the first, second, fourth, and third cylinders, for example. To be changed sequentially for each cycle.

As a result, in addition to the effect described in the tenth embodiment, the durability of the injection nozzle sheet portion of the first cylinder can be improved. As a method of sequentially changing the cylinders to be post-injected, in addition to the method shown in FIG. 26, for example, in the case of a 4-cylinder engine, as shown in FIG. 27 and FIG. After the injection of only the main injection is performed, the cylinders to be injected next may perform the main injection and the post-injection, and the cylinders to be post-injected may be sequentially changed.

In the above, the case where the post-injection is performed in only one cylinder in one cycle has been described, but the post-injection may be performed in a plurality of cylinders. Further, as in the ninth and tenth embodiments, the post-injection in the latter half of the expansion stroke and the post-injection in the first half of the expansion stroke may be performed in different cylinders or a plurality of cylinders.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an exhaust emission control device according to a first embodiment.

FIG. 2 is a diagram showing a relationship between a post-injection timing and an injection amount (a) and an exhaust temperature (b) in the exhaust emission control device of the first embodiment.

FIG. 3 is a diagram showing a relationship between a post injection amount and an exhaust temperature in the first embodiment.

FIG. 4 is a graph showing a relationship between engine speed and exhaust temperature with respect to engine torque in the first embodiment.

FIG. 5 is a control flowchart of the exhaust emission control device according to the first embodiment.

FIG. 6 is a diagram showing a relationship between a crank angle and a fuel injection amount in the first embodiment.

FIG. 7 is a system configuration diagram of an exhaust emission control device according to a second embodiment.

FIG. 8 is a system configuration diagram of an exhaust emission control device according to a third embodiment.

FIG. 9 is a control flowchart of the exhaust emission control device of the third embodiment.

FIG. 10 is another system configuration diagram of the exhaust emission control device of the third embodiment.

FIG. 11 is a system configuration diagram of an exhaust emission control device according to a fourth embodiment.

FIG. 12 is a control flowchart of the exhaust emission control device of the fourth embodiment.

FIG. 13 is a diagram showing a relationship between a crank angle and a fuel injection amount in Embodiment 4 (when the exhaust temperature is higher than a predetermined value).

FIG. 14 is a diagram showing a relationship between a crank angle and a fuel injection amount in a fourth embodiment (when the exhaust temperature is below a predetermined value).

FIG. 15 is another system configuration diagram of the exhaust emission control device of the fourth embodiment.

FIG. 16 is a control flowchart of the exhaust emission control device of the fifth embodiment.

FIG. 17 is a system configuration diagram of an exhaust emission control device according to a sixth embodiment.

FIG. 18 is another system configuration diagram of the exhaust emission control device of the sixth embodiment.

FIG. 19 is a graph showing the relationship between catalyst temperature and nitrogen oxide purification rate in Example 7.

FIG. 20 is a diagram showing the relationship between the timing of post-injection and the carbon number of hydrocarbons generated in Example 7.

FIG. 21 is a control flowchart of the exhaust emission control device of the seventh embodiment.

FIG. 22 is a diagram showing the relationship between the exhaust temperature and the timing of post injection in the seventh embodiment.

FIG. 23 is a control flowchart of the exhaust emission control device of the eighth embodiment.

FIG. 24 is a diagram showing the relationship between the fuel injection generation timing and the injection amount of each cylinder in the ninth embodiment.

FIG. 25 is a diagram showing the relationship between the fuel injection generation timing and the injection amount of each cylinder in the tenth embodiment.

FIG. 26 is a diagram showing the relationship between the generation timing of fuel injection and the injection amount of each cylinder in the eleventh embodiment.

FIG. 27 is another diagram (part 1) showing the relationship between the fuel injection generation timing and the injection amount of each cylinder in the eleventh embodiment.

FIG. 28 is another diagram (part 2) showing the relationship between the fuel injection generation timing and the injection amount of each cylinder in the eleventh embodiment.

FIG. 29 is another diagram showing the relationship between the generation timing of fuel injection and the injection amount of each cylinder in the conventional apparatus.

[Explanation of symbols]

 1. ． ． Exhaust gas purification device, 17. ． ． Exhaust treatment means (device), 18. ． ． Fuel injection control means (ECU),

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Ohata 1-1, Showa-cho, Kariya city, Aichi Nihon Denso Co., Ltd.

Claims (12)

[Claims] 1. A fuel injection means provided for each cylinder, an exhaust treatment means interposed in an exhaust passage, an operating state detecting means, and an exhaust gas for estimating an exhaust temperature from an output from the operating state detecting means. The temperature estimating means, the temperature comparing means for comparing the output of the exhaust temperature estimating means with a predetermined value, and the fuel injection timing and the fuel injection amount in the fuel injecting means are determined based on the output of the temperature comparing means. In an exhaust gas purifying apparatus for an internal combustion engine, comprising: a fuel injection control unit that operates an injection unit, the fuel injection control unit, when the exhaust gas temperature is equal to or lower than the predetermined value, supplies fuel after main fuel injection for engine output generation. An exhaust gas purifying apparatus for an internal combustion engine, characterized in that after-injection is commanded to control the exhaust gas temperature of the engine within a temperature range suitable for the operation of the exhaust gas processing means. 2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the post-injection is performed in the first half of an expansion stroke of the engine. 3. A fuel injection means provided for each cylinder, a particulate collection means interposed in the exhaust passage, a pressure detection means provided on the inlet side of the particulate collection means, and an operating state detection. Means, an exhaust temperature estimating means for estimating the exhaust temperature from the output from the operating state detecting means, a temperature comparing means for comparing the output of the exhaust temperature estimating means with a predetermined value, the operating state detecting means and the pressure detecting means. A deposition amount calculation means for calculating the amount of particulate accumulation in the particulate collection means based on the output of, and a deposition amount comparison means for comparing the output of the deposition amount calculation means with a predetermined value,
An exhaust gas purification apparatus for an internal combustion engine, comprising: a fuel injection control unit that determines a fuel injection timing and a fuel injection amount in the fuel injection unit based on the outputs of the temperature comparison unit and the deposition amount comparison unit to operate the fuel injection unit. The fuel injection control means, when the amount of particulate accumulation in the particulate collection means exceeds a predetermined value and the exhaust temperature is less than the predetermined value, after the main fuel injection for generating the engine output, An exhaust emission control device for an internal combustion engine, which commands execution of post-injection of fuel in the first half of an expansion stroke. 4. A fuel injection means provided for each cylinder, a nitrogen oxide reducing means interposed in an exhaust passage, an operating state detecting means, and an exhaust temperature estimated from an output from the operating state detecting means. Exhaust temperature estimating means, and temperature comparing means for comparing the output from the exhaust temperature estimating means with a predetermined value,
In the exhaust gas purifying apparatus for an internal combustion engine, which has a fuel injection control means for operating the fuel injection means by determining the fuel injection timing and the fuel injection amount in the fuel injection means based on the output of the temperature comparison means, the fuel injection control means When the exhaust temperature is higher than the specified value, post-injection of fuel is performed in the latter half of the expansion stroke after main fuel injection to generate engine output, and when the exhaust temperature is lower than the specified value, additional injection is performed. The exhaust emission control device for an internal combustion engine, wherein an instruction is made to perform the same even in the first half of the expansion stroke. 5. A fuel injection means provided for each cylinder, a particulate collection means provided in the exhaust passage, a nitrogen oxide reduction means provided in the exhaust passage, and a particulate collection. A pressure detecting means provided on the inlet side of the means, an operating state detecting means, an exhaust temperature estimating means for estimating an exhaust temperature from an output from the operating state detecting means, and an output from the exhaust temperature estimating means as a predetermined value. A temperature comparing means for comparing, a deposit amount calculating means for calculating the particulate deposit amount in the particulate collecting means by the outputs from the operating condition detecting means and the pressure detecting means, and an output from the deposit amount calculating means to a predetermined value. And a fuel injection timing and a fuel injection amount in the fuel injection means are determined by outputs from the temperature comparison means and the deposition quantity comparison means. In an exhaust gas purifying apparatus for an internal combustion engine having fuel injection control means for operating a stage, the fuel injection control means generates engine output when the amount of particulate accumulation in the particulate trapping means is below a predetermined value. After the main fuel injection, the post-injection is performed in the latter half of the expansion stroke, and if the particulate accumulation amount on the particulate trap exceeds the predetermined value and the exhaust temperature is below the predetermined value, the post-injection The exhaust emission control device for an internal combustion engine, wherein an instruction is made to perform the same even in the first half of the expansion stroke. 6. A fuel injection means provided for each cylinder, a particulate collection means provided in the exhaust passage, a nitrogen oxide reduction means provided in the exhaust passage, and a particulate collection. Pressure detecting means provided on the inlet side of the means, operating state detecting means, exhaust temperature estimating means for estimating the exhaust temperature based on the output of the operating state detecting means, and fuel based on the output of the exhaust temperature estimating means. Fuel injection timing correcting means for correcting and changing the injection timing, temperature comparing means for comparing the output of the exhaust temperature estimating means with a predetermined value, and particulate collecting means based on the outputs of the operating state detecting means and the pressure detecting means. Amount calculation means for calculating the amount of particulate accumulation in the above, an accumulation amount comparison means for comparing the output of the accumulation amount calculation means with a predetermined value, and outputs of the temperature comparison means and the accumulation amount comparison means. In the exhaust gas purifying apparatus for an internal combustion engine, which has a fuel injection control means for operating the fuel injection means by determining a fuel injection timing and a fuel injection amount in the fuel injection means on the basis of the fuel injection control means, When the amount of particulate accumulation in the collecting means is less than or equal to a predetermined value, after the main fuel injection for generating the engine output, a command is given to perform post-injection of fuel in the latter half of the expansion stroke of the engine, and the particulate collecting means. If the particulate matter accumulation amount in the above condition exceeds the predetermined value and the exhaust gas temperature is less than the predetermined value, in addition to this, it is instructed to carry out the post-injection of fuel also in the first half of the expansion stroke, and the particulate matter accumulation amount is the predetermined value. In the following cases, the injection timing of the post-injection in the latter half of the expansion stroke is changed based on the output of the exhaust temperature estimation means, and the exhaust temperature becomes high. Exhaust purification system of an internal combustion engine, characterized by a command to delay from timing setting the throat post-injection timing. 7. The method according to claim 5 or 6, wherein when the particulate accumulation amount in the particulate trapping means exceeds the predetermined value and the exhaust gas temperature is equal to or lower than the predetermined value, the latter half of the expansion stroke is performed. Without performing injection,
An exhaust emission control device for an internal combustion engine, which performs only post-injection in the first half of an expansion stroke. 8. The method according to any one of claims 1 to 7,
An exhaust emission control device for an internal combustion engine, wherein the post-injection of the fuel is performed only for a specific cylinder. 9. The method according to claim 1, wherein
An exhaust emission control device for an internal combustion engine, characterized in that a cylinder that performs post injection in the first half of the expansion stroke and a cylinder that performs post injection in the second half of the expansion stroke are different. 10. The exhaust emission control device for an internal combustion engine according to claim 8 or 9, wherein the injection amount of post-injection for a plurality of cycles is collectively performed at one time, and the number of post-injections is reduced. 11. An exhaust emission control system for an internal combustion engine according to claim 8, wherein cylinders to be subjected to post-injection are sequentially switched and changed. 12. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas temperature estimating means is replaced by a temperature detecting means for directly detecting the exhaust gas temperature. .