JP3671455B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an exhaust gas purification apparatus for an internal combustion engine that purifies particulates, NOx, and the like contained in exhaust gas of a diesel engine or the like.
[0002]
[Prior art and problems]
Diesel engine exhaust contains particulates and nitrogen oxides (NOx) consisting of gaseous and solid components, and these harmful components are environmentally problematic.
Of these, for particulates, a method of purifying only gaseous components with an oxidation catalyst provided in the exhaust passage of a diesel engine has been put into practical use. However, this method has a problem that the solid component of the 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.
[0003]
On the other hand, in Japanese Patent Publication No. 6-10409, particulates are collected by a trap filter carrying a catalyst, and after a predetermined amount of particulates has been collected, the intake throttle provided in the intake passage of the engine is throttled. A method for regenerating the trap filter by raising the exhaust gas temperature and burning the particulates has been proposed.
However, this method necessitates a new intake throttle means, its actuator, control device, and the like, which complicates the configuration. In addition, since the temperature rise of the exhaust by 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 running in an urban area. Furthermore, if the intake air is throttled, the combustion state of the engine deteriorates, so that the output decreases and the emission deteriorates.
[0004]
Further, in the above method, NOx, which is another harmful component, cannot be purified. Therefore, another purification means is required to purify NOx, resulting in an increase in 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, and this reducing agent and exhaust gas are mixed to reduce and purify NOx on the catalyst. It is.
However, this method has a problem in that the reducing agent is a high-boiling molecule, so that the reactivity is low and the reduction and purification efficiency of NOx is low. Furthermore, since the configuration is complicated, there is a problem that the apparatus becomes large.
[0005]
Japanese Patent Application Laid-Open No. 5-156993 proposes a method of controlling the fuel injection timing of a fuel injector that injects fuel into a cylinder chamber by using an electromagnetic valve, thereby promoting purification. That is, after injection of main fuel for generating 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 has decreased. It is thermally decomposed without burning it to produce highly reactive hydrocarbons. Then, this hydrocarbon is mixed with exhaust gas, and NOx contained in the exhaust gas is reduced and purified on the catalyst.
However, this method has a problem that NOx cannot be purified when the exhaust gas temperature is lower than the activation temperature of the catalyst.
[0006]
Further, in the method proposed in the above publication, since the post-injection is always performed at a fixed time in the stroke, the degree of fuel decomposition is uniquely determined. That is, the higher the exhaust gas temperature, the more hydrocarbon having a higher degree of decomposition and a smaller number of carbons is supplied. However, as shown in FIG. 19, which will be 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 carbons (B in FIG. 19) is supplied. There is a need. Therefore, this method has a problem that a reducing agent (hydrocarbon) that maximizes the reduction and purification efficiency of NOx that varies depending on the exhaust temperature cannot always be supplied to the catalyst.
[0007]
Furthermore, in order to control a very small amount of post-injection fuel, a highly responsive solenoid valve is required, which causes an increase in cost and volume.
In addition, this method cannot purify particulates, which are another harmful component, so that a separate purification device is required to purify the particulates, which increases the cost and volume.
[0008]
[Problems to be solved by the invention]
Therefore, the present invention is intended to provide an exhaust gas purification apparatus for an internal combustion engine that can efficiently purify exhaust gas including both particulates and NOx with a simple configuration.
[0009]
[Means for Solving the Problems]
For convenience of explanation, the first reference invention will be described first.
  First reference inventionThe fuel injection means provided for each cylinder, the exhaust processing means interposed in the exhaust passage, the operating state detecting means, and the exhaust temperature estimating means for estimating the exhaust temperature based on 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, and determining a fuel injection timing and a fuel injection amount in the fuel injecting means based on the output of the temperature comparing means. In an internal combustion engine exhaust purification device having a fuel injection control means to be operated,
  When the exhaust gas temperature is less than the predetermined value, the fuel injection control means commands the fuel post-injection after the main fuel injection for generating the engine output, whereby the engine exhaust temperature is controlled by the operation of the exhaust gas processing means. To a temperature range suitable for
[0010]
  In the first reference invention, A fuel injection control means for controlling the fuel injection amount and fuel injection timing, a temperature estimation means and a temperature comparison means are provided, and the fuel injection control means is configured to perform post-injection of fuel when the exhaust temperature is below a predetermined value. And the fuel injection means is controlled so that the exhaust processing means has a temperature at which it operates satisfactorily.
  The post-injection is preferably performed at the first half of the expansion stroke. This is because if the post-injection is performed in the first half of the expansion stroke, the temperature in the cylinder chamber is high, the fuel burns effectively, and the exhaust temperature can be increased efficiently.
[0011]
  The second reference invention is, Fuel injection means provided for each cylinder, particulate collection means interposed in the exhaust passage, pressure detection means provided on the inlet side of the particulate collection means, operating state detection means, Based on the exhaust temperature estimating means for estimating the exhaust temperature based on the output from the operating condition detecting means, the temperature comparing means for comparing the output of the exhaust temperature estimating means with a predetermined value, and the outputs of the operating condition detecting means and the pressure detecting means. The accumulation amount calculating means for calculating the particulate accumulation amount in the particulate collection means, the accumulation amount comparing means for comparing the output of the accumulation amount calculating means with a predetermined value, and the outputs of the temperature comparing means and the accumulation amount comparing means An exhaust purification device for an internal combustion engine having 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 based on Oite,
  When the particulate accumulation amount in the particulate collection means exceeds a predetermined value and the exhaust gas temperature is equal to or lower than the predetermined value, the fuel injection control means performs the expansion of the engine after the main fuel injection for generating engine output. Command post fuel injection in the first half of the stroke.
[0012]
  In the second reference invention,Particulate collecting means as exhaust treatment means, exhaust temperature estimation means and temperature comparison means, accumulation amount calculation means and accumulation amount comparison means, and fuel injection control means are provided, and the fuel injection control means comprises: When the particulate accumulation amount exceeds a predetermined value and the exhaust gas temperature is equal to or lower than the predetermined value, the post-injection is commanded in the first half of the expansion stroke.
[0013]
  No. of this application1DepartureTomorrowThe fuel injection means provided for each cylinder, the nitrogen oxide reduction means interposed in the exhaust passage, the operating state detecting means, and the exhaust temperature estimation for estimating the exhaust temperature based on the output from the operating state detecting means Means, a temperature comparison means for comparing the output from the exhaust temperature estimation means with a predetermined value, and the fuel injection timing and the fuel injection amount in the fuel injection means are determined by the output of the temperature comparison means, and the fuel injection means is operated. An exhaust purification device for an internal combustion engine having fuel injection control means for causing
  The fuel injection control means performs the fuel post-injection in the latter half of the expansion stroke after the main fuel injection for generating engine output when the exhaust temperature is higher than a predetermined value, and when the exhaust temperature is lower than the predetermined value. In addition, an exhaust purification device for an internal combustion engine that commands to perform post-injection even in the first half of the expansion stroke(Claim 1).
[0014]
  First1The most notable aspect of the present invention is that nitrogen oxide reduction means, exhaust temperature estimation means and temperature comparison means, and fuel injection control means as exhaust treatment means are provided. Is instructed to carry out post-injection in the latter half of the expansion stroke if the value is greater than or equal to a predetermined value, and to perform post-injection in the first half of the expansion stroke if the exhaust gas temperature is less than or equal to the predetermined value.
[0015]
  No. of this application2DepartureTomorrowThe fuel injection means provided for each cylinder, the particulate collection means interposed in the exhaust passage, the nitrogen oxide reduction means interposed in the exhaust passage, and the inlet side of the particulate collection means The pressure detection means provided in the engine, the operation state detection means, the exhaust temperature estimation means for estimating the exhaust temperature from the output from the operation state detection means, and the temperature comparison for comparing the output from the exhaust temperature estimation means with a predetermined value Means, a deposition amount calculating means for calculating a particulate deposition amount in the particulate collection means based on outputs from the operating state detecting means and the pressure detecting means, and a deposition for comparing the output from the deposition amount calculating means with a predetermined value. The fuel injection means and the fuel injection amount in the fuel injection means are determined by the output from the quantity comparison means, the temperature comparison means, and the deposit amount comparison means, and the fuel injection means is operated. In the exhaust purification system of an internal combustion engine having a fuel injection control means that,
  The fuel injection control means performs post-injection after main fuel injection for generating engine output in the latter half of the expansion stroke when the particulate accumulation amount in the particulate collection means is less than a predetermined value. If the particulate accumulation amount on the collecting means exceeds a predetermined value and the exhaust temperature is not more than a predetermined value, in addition to this, the exhaust of the internal combustion engine is commanded to be executed even in the first half of the expansion stroke Purification device(Claim 2).
[0016]
  First2The most notable aspects of the invention are 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, fuel injection And when the particulate accumulation amount is less than a predetermined value, post-injection is performed in the latter half of the expansion stroke, and the particulate accumulation amount exceeds the predetermined value and the exhaust temperature is less than the predetermined value. In some cases, a post-injection is also performed in the first half of the expansion stroke.
[0017]
  Of this application3DepartureTomorrowThe fuel injection means provided for each cylinder, the particulate collection means interposed in the exhaust passage, the nitrogen oxide reduction means interposed in the exhaust passage, and the inlet side of the particulate collection means The pressure detection means provided in the operation state detection means, the exhaust temperature estimation means for estimating the exhaust temperature based on the output of the operation state detection means, and the fuel injection timing is corrected based on the output of the exhaust temperature estimation means The fuel injection timing correcting means to be changed, the temperature comparing means for comparing the output of the exhaust temperature estimating means with a predetermined value, and the particulate accumulation in the particulate collecting means based on the outputs of the operating state detecting means and the pressure detecting means A deposit amount calculating means for calculating the amount, a deposit amount comparing means for comparing the output of the deposit amount calculating means with a predetermined value, and outputs of the temperature comparing means and the deposit amount comparing means. In the exhaust purification system of an internal combustion engine having a fuel injection control means for actuating the decided fuel injection means and a fuel injection timing and the fuel injection amount in serial fuel injection means,
  The fuel injection control means implements fuel post-injection in the latter half of the engine expansion stroke after the main fuel injection for generating engine output when the particulate accumulation amount in the particulate collection means is less than a predetermined value. Command
  When the particulate accumulation amount in the particulate collection means exceeds a predetermined value and the exhaust temperature is lower than the predetermined value, in addition to that, the post-injection of fuel is commanded to be performed even in the first half of the expansion stroke,
  In addition, the injection timing of the post-injection in the latter half of the expansion stroke when the particulate accumulation amount is not more than a predetermined value is changed based on the output of the exhaust temperature estimating means, and the post-injection timing is changed from the set timing as the exhaust temperature becomes higher. An exhaust purification device for an internal combustion engine, characterized by instructing to delay(Claim 3).
[0018]
  First3The most notable aspect of the invention is that2In addition to the configuration of the invention, fuel injection timing correction means for correcting and changing the fuel injection timing is provided, and the timing of post-injection performed in the latter half of the expansion stroke when the particulate accumulation amount is not more than a predetermined value is set as the exhaust temperature. To delay the higher the temperature is.
[0019]
  On the other hand,4The invention is as described above.2, Number3In the present invention, when the particulate accumulation amount in the particulate collecting means exceeds the predetermined value and the exhaust temperature is equal to or lower than the predetermined value, the post-injection is not performed in the latter half of the expansion stroke, and the post-injection is performed only in the first half of the expansion stroke. To do.
[0020]
In each of the above inventions, it is preferable that the post-injection is performed in a specific cylinder or a specific cycle. As will be described in detail later, if the amount of post-injection is increased by collectively performing post-injection, the configuration of an actuator such as a solenoid valve can be made inexpensive and control can be facilitated.
[0021]
  Further, the number of operations of the fuel injection means can be equalized by a method in which the post-injection in the first half of the expansion stroke and the post-injection in the second half of the expansion stroke are performed in different cylinders, or the cylinders that perform the post-injection are sequentially switched preferable. This is because the average life of the fuel injection means can be extended by making the number of operations of the fuel injection means equal so that the operation of the fuel injection means is not concentrated on a specific cylinder.
  Further, the exhaust temperature can be directly detected by the exhaust temperature detecting means without using the exhaust temperature estimating means.
Further, in the post-injection performed in the first half of the expansion process, it is preferable to inject 5 to 20% of the main injection amount fuel for generating engine output into the cylinder chamber.
Further, in the post-injection performed in the second half of the expansion process, it is preferable to inject fuel with a main injection amount of 0.3 to 5% for generating engine output into the cylinder chamber.
[0022]
[Action]
  aboveFirst reference inventionAccording to this, 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 after the injection of the main fuel for generating engine output. As a result, the post-injected fuel burns and the exhaust temperature can be raised. On the other hand, the exhaust temperature changes depending on the timing of post-injection as shown in FIG. 2, which will be described in detail later, or the amount of fuel to be injected as shown in FIG. 3, and the exhaust temperature is controlled by controlling this timing and amount. Is possible.
[0023]
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) (the post-injection a in FIG. 2), the fuel is injected to a place where the temperature in the cylinder chamber is sufficiently high. Fuel burns and the exhaust temperature rises. At that time, the gas in the cylinder chamber expands with the lowering of the piston until the exhaust valve opens, and the temperature decreases. After the exhaust valve opens, the gas exits from the cylinder chamber. The decrease is reduced and the exhaust temperature is increased.
Further, when the post-injection is performed in the first half of the expansion stroke, the exhaust gas temperature increases as the post-injection amount increases as shown in FIG.
[0024]
On the other hand, when post-injection is performed in the latter half of the expansion stroke (after ATDC 90 degrees) (post-injection b in FIG. 2), the fuel injected after combustion is injected in order to inject fuel into a place where the temperature in the cylinder chamber is low. The exhaust temperature does not increase too much. 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.
Other methods of raising the exhaust temperature include a method of retarding the main fuel injection timing and a method of changing only the injection timing while fixing the post-injection amount. This is not preferable from the viewpoint of fuel consumption.
[0025]
As described above, the purification efficiency can be greatly improved by controlling the exhaust temperature so that the exhaust temperature becomes a temperature suitable for the operation of the exhaust treatment means. 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.
[0026]
  AlsoSecond reference inventionAccording to the above, the particulates in the exhaust gas are collected by the filter with catalyst for collecting and purifying the particulates. The particulates on the filter are burned in the operating state where the exhaust temperature is high, and the filter is regenerated. However, when the operation state where the exhaust temperature is low continues for a long time due to traffic jams or the like, the amount of particulate accumulation on the filter exceeds a predetermined value, the engine output decreases, and the fuel consumption deteriorates.
[0027]
Therefore, when the particulate accumulation amount on the filter exceeds the predetermined value and the exhaust temperature is below the predetermined value and the filter cannot be regenerated, a small amount of fuel (for example, 5 to 20% of the main injection amount) is supplied to the engine. After injection of the main fuel for generation, post-injection is performed in the cylinder chamber where the temperature in the first half of the expansion stroke is high, and the exhaust temperature is raised.
At that time, by controlling the timing and amount of post-injection, the exhaust temperature can be adjusted to a temperature suitable for particulate combustion by the catalyst (for example, 400 ° C. or more), and the particulates on the filter are thereby reduced. It burns and the filter is regenerated.
[0028]
  Also,First1According to the invention, when the exhaust gas temperature is higher than a predetermined value (for example, 250 ° C.) that is the activation temperature of the NOx purification reduction catalyst, a very small amount (for example, the main injection amount) is injected after the main fuel is injected for generating the engine output. 0.3 to 5%) of the fuel is post-injected into the cylinder chamber where the temperature in the latter half of the expansion stroke has decreased. In this case, since the temperature in the cylinder chamber is low, the fuel for the post-injection is pyrolyzed without burning to produce highly reactive hydrocarbons, which are mixed with the exhaust gas. And, by the action of this hydrocarbon, NOx contained in the exhaust gas can be effectively reduced and purified on the catalyst.
[0029]
However, when the exhaust gas temperature is below a predetermined value, purification with a catalyst is impossible, so a smaller amount (for example, 5 to 20% of the main injection amount) of fuel is post-injected into the cylinder chamber where the temperature in the first half of the expansion stroke is high. To do. In this case, the post-injected fuel burns and the exhaust temperature rises. At this time, NOx in the exhaust can be reduced and purified by controlling the timing and amount of post-injection so that the exhaust temperature is set to a temperature suitable for NOx purification by the catalyst (for example, 250 ° C. or higher).
[0030]
  MaIn the second invention,It has particulate collection means and nitrogen oxide reduction means.
AndFirst2In the invention, normally (when the particulate accumulation amount on the filter is equal to or less than a predetermined value), after injection of the main fuel for generating engine output, a very small amount of fuel (for example, 0.3 to 5% of the main injection amount) is used. Are injected into the cylinder chamber where the temperature in the latter half of the expansion stroke has decreased. In this case, the post-injected fuel is pyrolyzed without burning to produce highly reactive hydrocarbons, and the hydrocarbons are mixed with the exhaust gas, so that NOx contained in the exhaust gas is adsorbed on the catalyst. It can be reduced and purified well. At the same time, the particulates in the exhaust are collected by a filter. Then, the particulates on the filter are burned when the exhaust gas temperature is in an operating state, and the filter is regenerated.
[0031]
  On the other hand, if the operation at a low exhaust temperature continues for a long time due to traffic jams, etc., the particulate accumulation amount on the filter exceeds a predetermined value, the engine output decreases and the fuel consumption deteriorates. Therefore, in the present invention, when the particulate accumulation amount on the filter exceeds a predetermined value and the exhaust temperature is not more than the predetermined value and the regeneration of the filter cannot be expected, a small amount (for example, 5 to 20% of the main injection amount) of fuel Are injected into the cylinder chamber where the temperature in the first half of the expansion stroke is high. In this case, the post-injected fuel burns and the exhaust temperature rises greatly. Then, by controlling the timing and amount of post-injection, the exhaust temperature is set to a temperature suitable for particulate combustion by the catalyst (for example, 400 ° C. or higher), the particulates on the filter are burned, and the filter can be regenerated.
  As above,2According to the invention, it is possible to efficiently purify both NOx and particulates with a simple configuration without adding a particularly complicated member.
[0032]
  Also above3According to the invention, by changing the timing of post-injection performed in the latter half of the expansion stroke in order to supply the reducing agent to the NOx catalyst according to the exhaust temperature, the optimum decomposition degree (used as a reducing agent at any exhaust temperature) The number of hydrocarbon carbon atoms) can be supplied to the catalyst, and the NOx reduction and purification efficiency can be greatly improved. That is, as shown in FIG. 19 to be described in detail later, when hydrocarbon is supplied as a reducing agent, the NOx reduction purification efficiency by the catalyst peaks at a certain temperature, and the temperature at which the peak purification rate is obtained is the reducing agent (carbonization). Hydrogen) depends on the number of carbon atoms. The temperature increases as the number of carbon atoms 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 at which T1 <T2). On the contrary, the efficiency is higher when B having a larger number of carbon atoms is used.
[0033]
On the other hand, if the timing of the post-injection is always constant as in the conventional apparatus, when the exhaust temperature is high, the degree of decomposition is large (the carbon number is small), and high NOx purification efficiency is obtained at a low temperature. When only hydrocarbons are supplied and the exhaust temperature is low, only hydrocarbons that can obtain high NOx purification efficiency at high temperatures (large number of carbon atoms) are supplied. Therefore, it is impossible to supply fuel having a decomposition degree suitable for each temperature, and high NOx reduction purification efficiency cannot be obtained.
[0034]
  On the other hand, it is known that the carbon number of pyrolyzed fuel (hydrocarbon) obtained by post-injection in the latter half of the expansion stroke differs depending on the post-injection timing as shown in FIG. In other words, 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 is reduced and the carbon number of the resulting hydrocarbon is increased.
  So, first3In the invention, the injection timing for post-injection is changed according to the exhaust gas temperature, and the post-injection timing is delayed as the exhaust gas temperature increases, so that the reducing agent having a larger carbon number is supplied. As a result, the catalyst can always be used with a high NOx reduction efficiency regardless of the exhaust temperature. Therefore, both NOx and particulates can be efficiently purified with a simple configuration.
[0035]
  On the other hand4The invention is the first2, Number3In the present invention, post-injection is performed only in the first half of the expansion stroke when the particulate accumulation amount exceeds a predetermined value and the exhaust temperature is not higher than the predetermined value. The reason is as follows.
  Depending on the operating conditions, when the exhaust temperature is increased by the post-injection in the first half of the expansion stroke, and the post-injection is subsequently performed in the second half of the expansion stroke, the post-injected fuel burns and is an effective reducing agent. It becomes impossible to supply hydrocarbons. When emphasizing avoidance of such a situation, it is preferable to stop the fuel post-injection in the latter half of the expansion stroke and perform only the post-injection in the first half of the expansion stroke as in the present invention.
[0036]
Further, in the above-described inventions, when only a specific cylinder among the entire cylinders (N cylinders) injects the post-injection amount for N cylinders at the same time, the subsequent injection amount is increased by N times. Therefore, it is not necessary to make the injection amount extremely small. As a result, an actuator such as a solenoid valve does not require extremely high responsiveness and is easy to control, so that the cost and the volume of the actuator can be reduced as compared with the prior art.
Furthermore, it is possible to absorb the variation in the injection amount between the nozzles of each cylinder, which becomes noticeable in a very small amount of injection. In addition, since the number of times the injection nozzle is seated can be reduced, the durability of the nozzle sheet can be greatly improved.
[0037]
In addition, each cylinder or a specific cylinder injects the post-injection amount for M cycles at a rate of once every M cycles (M ≧ 2), and further sequentially changes the cylinders that perform the post-injection, It is possible to obtain a further effect of absorbing the variation in the injection amount and improving the durability of the nozzle sheet portion.
Further, as is known from the embodiments described later, each invention of the present application can be realized with a simple configuration without newly adding complicated members.
[0038]
【The invention's effect】
As described above, according to the invention of the present application, it is possible to provide an exhaust purification device for an internal combustion engine such as a diesel engine that can efficiently purify particulates or nitrogen oxides with a simple configuration.
[0039]
【Example】
Example 1
  Applies to 4-cylinder diesel enginesFirstOne embodiment will be described with reference to FIG.
  In this example, as shown in FIG. 1, a fuel injector 13 and an electromagnetic valve 14 as fuel injection means provided for each cylinder, an exhaust treatment device 17 interposed in an exhaust passage 16, a rotation sensor 30, The ECU 18 as an operation state detection unit that detects an operation state using the load sensor 31 and the pressure sensor 32, the ECU 18 as an exhaust temperature estimation unit that estimates the exhaust temperature based on information of the operation state detection unit, and the estimated exhaust gas An internal combustion engine having an ECU 18 as temperature comparison means for comparing the temperature with a predetermined value, and an ECU 18 as fuel injection control means for determining the fuel injection timing and fuel injection amount based on the result of the temperature comparison means and operating the fuel injection means. 1 is an exhaust purification device 1 of an engine (diesel engine) 10.
  The fuel injection control means commands the fuel post-injection after the main fuel injection for generating the engine output when the exhaust temperature is equal to or lower than a predetermined value, whereby the exhaust temperature is a temperature suitable for the operation of the exhaust processing means 17. Control to range.
[0040]
Each is described in detail below.
As shown in FIG. 1, the diesel engine 10 and the exhaust emission control device 1 have four cylinder bores, in which pistons are fitted so as to be slidable back and forth, and a cylinder block 11 having a cylinder chamber inside each cylinder, cylinder A cylinder head 12 assembled on the block 11 and closing each of its cylinder chambers, a crankshaft in which its piston is connected by a connecting rod, a valve mechanism for opening and closing an intake valve and an exhaust valve, and a cylinder corresponding to the cylinder chamber Four fuel injectors 13 as fuel injection means installed in the head 12, four electromagnetic valves 14 assembled to the fuel injector 13, and a feed pump 15 for supplying fuel to the fuel injector 13 from a fuel tank (not shown). , 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.
[0041]
The ECU 18 is connected to a rotation sensor 30, a load sensor 31, and a pressure sensor 32 that constitute an operating state detection means in its input circuit, and the electromagnetic valve 14 is electrically connected to its output circuit. 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 controlled to open and close based on the result. Further, the ECU 18 has a comparison circuit that calculates the exhaust gas 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 disposed on the crankshaft, the load sensor 31 is disposed on an accelerator pedal (not shown), and the pressure sensor 32 is disposed on the fuel header 22.
[0042]
Further, the feed pump 15 is connected to the fuel injector 13 through the fuel headers 22 and 23 via the fuel header 22. 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, 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 engine output and the post-injection for improving the purification efficiency are operated by a common device.
[0043]
The exhaust treatment device 17 includes the following. For example, there is an oxidation catalyst in which a wash coat layer such as alumina is provided on the surface of a carrier such as ceramic, and a noble metal catalyst such as Pt, Pd, Rh is supported to purify gas components in the particulates. Alternatively, a large number of channels are formed by a honeycomb-like lattice made of a porous material such as ceramic, the inlets and outlets of the channels are alternately closed with a sealing material, and a washcoat layer such as alumina is provided on the surface. , A filter with a catalyst for collecting and purifying particulates carrying a precious metal such as Pt or Pd or a base metal catalyst such as Cu. Alternatively, there is a NOx catalyst or the like which supports a carrier such as ceramic, which can reduce and purify NOx in an oxygen-excess atmosphere such as diesel exhaust in the presence of a reducing agent, such as Cu-zeolite or Pt-zeolite.
[0044]
Next, the function and effect of this example will be described.
In the exhaust emission control device 1 configured as described above, the ECU 18 outputs the engine output 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 catalyst activation temperature in the exhaust treatment device 17. A command is given to post-inject a small amount of fuel (for example, 5 to 20% of the main injection amount) in the first half of the expansion stroke (for example, ATDC 40 to 90 degrees) after the main fuel injection for generation. Then, the post-injected fuel is burned and the exhaust temperature can be raised.
[0045]
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, the exhaust temperature can be controlled by controlling this timing and amount.
That is, as shown by the symbol a in FIG. 2A, when the post-injection is performed in the first half of the expansion stroke (before ATDC 90 degrees), the fuel is injected to a place where the temperature in the cylinder chamber is sufficiently high. As a result, the exhaust gas temperature rises as shown in FIG. At that time, the gas in the cylinder chamber expands with the lowering of the piston until the exhaust valve opens, and the temperature decreases. After the exhaust valve opens, the gas exits from the cylinder chamber. Becomes smaller and the exhaust temperature becomes higher.
[0046]
Further, when the 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.
However, as shown by symbol b in FIG. 2A, when post-injection is performed in the latter half of the expansion stroke (after ATDC 90 degrees), fuel is injected into a place where the temperature in the cylinder chamber is low. It does not burn and therefore 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.
The purification efficiency can be greatly improved by setting the exhaust temperature to a temperature suitable for the operation of the exhaust treatment means.
[0047]
Next, a method for controlling the post-injection timing and amount in the exhaust purification apparatus 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 temperature t obtained based on the outputs of the rotation sensor 30 and the load sensor 31 is shown. However, as shown in the second embodiment, the exhaust temperature is directly controlled. It may be detected.
First, in S (step) 101, the exhaust temperature t obtained by the ECU 18 based on the outputs of the rotation sensor 30 and the load sensor 31 is read. Since the exhaust temperature t is determined by the engine speed and the engine load as shown in FIG. 4, for example, the exhaust temperature can be obtained by storing this in the ECU 18 in advance.
[0048]
In S102, t is compared with a 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, and the process returns to S101.
On the other hand, if the exhaust gas temperature t is smaller than t1, the exhaust gas purification by the catalyst cannot be expected, so the process proceeds to S103, and the post-injection timing and the post-injection amount for increasing the temperature are determined. This timing and amount are stored in advance in the ECU 18, and according to this, 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 can be obtained.
[0049]
In S104, for example, as shown in FIG. 6, a small amount of fuel is post-injected in the first half of the expansion stroke after the main fuel injection for generating engine output, and the process returns to S101.
However, if post-injection is performed more than necessary, the fuel consumption deteriorates. Therefore, the above cycle is executed, for example, once per second. If the exhaust temperature becomes higher than the set value t1 in S102, the post-injection is immediately stopped in S105. Like that.
As described above, according to this example, it is possible to provide an exhaust emission control device for a diesel engine that can adjust exhaust gas temperature and efficiently purify particulates or nitrogen oxides.
[0050]
Example 2
As shown in FIG. 7, this example is another example in which a temperature sensor 33 is provided in the exhaust pipe 16 upstream of the exhaust treatment device 17 in FIG.
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. On the other hand, in this example, the exhaust temperature is directly detected by the temperature sensor 33. As a result, the exhaust gas temperature in an engine transient state can be grasped more accurately, and control with higher accuracy becomes possible.
Others are the same as in the first embodiment.
[0051]
Example 3
In this example, as shown in FIG. 8 and FIG. 10, a filter with a catalyst 171 is used as the exhaust treatment device 17 in FIG. 1 or FIG. Further, in addition to the configuration of FIG. 1, the pressure sensor 35 is electrically connected to the input circuit of the ECU 18. Further, the ECU 18 calculates the particulate accumulation amount on the catalyst-equipped filter 171 based on the engine speed detected by the sensors 30, 31, and 35, the engine load, and the pressure upstream of the filter, and compares it with a predetermined value. Then, the solenoid valve 14 is controlled to open and close based on the result and the detected or estimated exhaust temperature. The pressure sensor 35 is disposed in the exhaust pipe 16 upstream of the filter with catalyst 171.
[0052]
The catalyst-equipped filter 171 has a large number of flow paths formed by a honeycomb lattice made of a porous member such as ceramic, and the inlets and outlets of the flow paths are alternately closed with a sealing material. The surface is provided with a washcoat layer of alumina, for example, and carries a noble metal such as Pt or Pd or a base metal catalyst such as Cu. Thereby, the particulate combustion temperature at the time of filter regeneration can be reduced.
[0053]
Next, the function and effect of this example will be described.
In the exhaust purification apparatus 1 configured as described above, when particulates accumulate on the filter with catalyst 171, the flow path is clogged, so that the pressure detected by the pressure sensor 35 increases. Based on the output of the pressure sensor 35 and the outputs of the rotation sensor 30 and the load sensor 31, the ECU 18 calculates the particulate accumulation amount in the filter 171 with the catalyst.
[0054]
Then, the amount of accumulation is compared with a predetermined value, and the exhaust value obtained by the ECU 18 from the operating condition detected by the rotation sensor 30 and the load sensor 31 exceeds a set value (for example, 10 g) that requires particulate removal by combustion. When the temperature is equal to or lower than the particulate combustion temperature (for example, 400 ° C.) by the catalyst, the first half of the expansion stroke after the main fuel injection for engine output generation (for example, ATDC 40 to A small amount of fuel (for example, 5 to 20% of the main injection amount) is post-injected at 90 degrees.
In this case, the post-injected fuel burns in the cylinder chamber where the temperature is still high and the exhaust gas temperature rises greatly, so that the particulates on the filter burn and the catalyst-equipped filter 171 is regenerated.
[0055]
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 for controlling the post-injection timing and amount in the exhaust emission control device will be described with reference to the flowchart shown in FIG.
In this example, the timing and amount of post-injection are controlled based on the particulate accumulation amount m and the exhaust temperature t in the filter with catalyst 171 calculated by the ECU 18.
[0056]
First, in S (step) 201, the particulate deposition amount m in the filter with catalyst 171 calculated by the ECU 18 is read. Next, in S202, this m is compared with a set value m1 (for example, 10 g) that requires removal of the particulates. If it is smaller than m1, the catalyst-equipped filter 171 does not need to be regenerated, and the process returns to S201. On the other hand, if the particulate deposition amount m is larger than m1, the process proceeds to S203, and the exhaust temperature t obtained by the ECU 18 based on the outputs of the rotation sensor 30 and the load sensor 31 is read.
[0057]
Then, in S204, this t is compared with a set value t2 (for example, 400 ° C.) that is the temperature at which particulate combustion by the catalyst is possible. When the exhaust temperature t is higher than t2, the particulates on the filter with catalyst 171 are combusted by the high-temperature exhaust, and the process returns to S201. On the other hand, if the exhaust gas temperature t is lower than t2, the process proceeds to S205, where the post-injection timing and post-injection amount are determined. This value is stored in the ECU 18 in advance, and is determined to be a value at which the particulate combustion temperature (for example, 400 ° C.) by the catalyst can be obtained.
[0058]
In S206, in the first half of the expansion stroke after the main fuel injection for generating engine output, a small amount of fuel is post-injected, for example, as shown in FIG. Burn particulates.
In step S207, the particulate deposition amount m on the filter is read again, and in step S208, it is compared with the set value m2 (for example, 0.5 g) of the particulate deposition amount serving as a reference for completion of the filter regeneration. If YES, the process returns to S206. If the regeneration is completed, the post-injection is stopped in S209 and the process returns to S201.
The above cycle is executed once per second, for example.
In this example as well, 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 disposed upstream of the filter 171 with catalyst.
[0059]
Example 4
As shown in FIG. 11, this example is another example 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 capable of reducing and purifying NOx in a carrier such as ceramic, such as Cu-zeolite and Pt-zeolite, in the presence of a reducing agent and in an oxygen-excess atmosphere such as in diesel exhaust. And NOx can be purified by supplying a reducing agent.
[0060]
Next, the function and effect of this example will be described.
When the exhaust temperature is higher than a predetermined value (for example, 250 ° C.) that is the activation temperature of the catalyst, a very small amount of fuel (for example, 0.3 to 5% of the main injection amount) is injected after the main fuel is injected for generating engine output. Is post-injected into the cylinder chamber where the temperature in the latter half of the expansion stroke (for example, ATDC 90 to 130 degrees) has decreased. In this case, the fuel for the post-injection is thermally decomposed without burning because the temperature in the cylinder chamber is low, and a highly reactive hydrocarbon is generated, and the hydrocarbon is mixed with the exhaust gas. Therefore, NOx contained in the exhaust gas can be reduced and purified on the catalyst.
[0061]
However, when the exhaust gas temperature is below a predetermined value, purification by the catalyst is impossible, so a further small amount (for example, 5 to 20% of the main injection amount) of fuel is used for the first half of the expansion stroke (for example, ATDC 40 to 90 degrees). After-injection into the high cylinder chamber. In this case, the post-injected fuel burns and the exhaust temperature rises. By controlling the timing and amount of post-injection, it becomes possible to make the exhaust temperature a temperature suitable for NOx purification by the catalyst (for example, 250 ° C. or higher), and NOx in the exhaust can be efficiently reduced and purified. it can.
[0062]
Next, a method for controlling the post-injection timing in the exhaust emission control device 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 temperature t obtained based on the outputs of the rotation sensor 30 and the load sensor 31 is shown.
First, in S (step) 301, after injection of main fuel for generating engine output, a very small amount of fuel is post-injected in the latter half of the expansion stroke, for example, as shown in FIG. 13 (post injection c in FIG. 13).
[0063]
Next, in S302, the exhaust temperature t obtained by the ECU 18 based on the outputs of the rotation sensor 30 and the load sensor 31 is read. In step S303, t is compared with a set value t3 that is an 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 smaller than the above-mentioned t3, exhaust purification by the catalyst cannot be expected, so the process proceeds to S304, and the post injection timing and amount are determined. This value is stored in advance in the ECU 18, and the post-injection timing and amount are determined so as to obtain the catalyst activation temperature (for example, 250 ° C.).
[0064]
In S305, for example, as shown in FIG. 14, 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 (rear injection d in FIG. 14), and the process returns to S302. If the post-injection is performed more than necessary, the fuel consumption deteriorates. If the exhaust temperature becomes higher than 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.
Also in this example, the exhaust temperature may be directly detected and controlled by the temperature sensor 33 in the same manner as described above. The configuration in this case is shown in FIG.
[0065]
Example 5
The purification device 1 of the present example is configured in the same manner as that of the third embodiment 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 flow paths formed by a honeycomb lattice made of a porous member such as ceramic, and the inlets and outlets of the flow paths are alternately closed by a sealing material. Then, for example, an alumina or zeolite layer is provided on the surface, and a noble metal such as Pt or Pd or a base metal catalyst such as Cu is supported, and a hydrocarbon is supplied as a reducing agent to the oxygen-excess atmosphere. NOx can be reduced and purified, and the particulate combustion temperature during filter regeneration can be reduced.
[0066]
Next, the function and effect of this example will be described.
In the exhaust purification apparatus configured as described above, when the amount of particulate accumulation on the catalyst-equipped filter 171 is small and it is not necessary to regenerate the filter, as in the fourth embodiment, after injection of main fuel for generating engine output, , A very small amount of fuel (for example, 0.3 to 5% of the main injection amount) is post-injected in the latter half of the expansion stroke (for example, ATDC 90 to 130 degrees). Thereby, NOx can be reduced and purified on the catalyst.
[0067]
On the other hand, the accumulation amount exceeds a set value (for example, 10 g) that requires particulate removal by combustion, and the exhaust temperature obtained by the ECU 18 based on the operating conditions detected by the rotation sensor 30 and the load sensor 31 is the particulate by the catalyst. When the combustion temperature is lower than 400 ° C. (for example, 400 ° C.), the catalyst-equipped filter 171 is forcibly regenerated, as in the third embodiment, in the first half of the expansion stroke (for example, ATDC 40 to 90 degrees). ~ 20%) of fuel is post-injected. As a result, the exhaust gas temperature rises, so that the particulates on the filter burn and the catalyst-equipped filter 171 is regenerated.
[0068]
Next, a method for controlling the post-injection timing and the injection amount in the exhaust emission control device 1 will be described with reference to the flowchart shown in FIG.
In this example, the post-injection timing and amount are controlled based on the particulate accumulation amount m and the exhaust gas temperature t in the filter 171 with catalyst calculated by the ECU 18.
First, in S (step) 401, 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.
[0069]
Then, the process proceeds to S402, and the particulate deposition 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 particulate removal, and if it is smaller than m1, the catalyst-equipped filter 171 does not need to be regenerated, and the process returns to S401. On the other hand, if the particulate accumulation amount m is larger than m1, the process proceeds to S404, and the exhaust temperature t obtained by the ECU 18 based on the outputs of the rotation sensor 30 and the load sensor 31 is read.
[0070]
In step S405, the exhaust temperature t is compared with a set value t1 (for example, 400 ° C.) that is the particulate combustion temperature of the catalyst. If the exhaust temperature t is higher than t1, the particulates on the catalyst-equipped filter 171 are combusted by the high-temperature exhaust, and the process directly returns to S401. On the other hand, if the exhaust gas temperature t is smaller than t1, a small amount of fuel is post-injected in the first half of the expansion stroke after the main fuel injection for generating engine output in S406. Then, the exhaust temperature is raised by this, and the particulates on the filter with catalyst 171 are burned.
[0071]
In S407, the particulate deposition amount m on the filter is read again. In S408, the particulate deposition amount m2 is compared with the set value m2 (for example, 0.5 g) for completing the regeneration of the filter. If not, the process returns to S406. If regeneration is completed, the post-injection in the first half of the expansion stroke is stopped in S409, and the process returns to S401.
The above cycle is executed once per second, for example.
Also in this example, the exhaust temperature may be directly detected and controlled by the temperature sensor 33 in the same manner as described above. The configuration in this case is the same as that shown in FIG.
[0072]
Example 6
As shown in FIG. 17, this example is another example in which two exhaust treatment means of the filter with catalyst 174 and the NOx catalyst 173 are provided in the example 5.
That is, in Example 5, both NOx reduction purification and particulate collection / incineration purification were performed in the filter 171 with catalyst. On the other hand, in this example, NOx reduction purification is performed by the NOx catalyst 173, and particulate collection / incineration purification is performed by the filter with catalyst 174 provided downstream of the NOx catalyst 173.
[0073]
The catalytic converter 173 carries a catalyst capable of reducing and purifying NOx in an oxygen-excess atmosphere such as diesel exhaust in the presence of a reducing agent, such as Cu-zeolite or Pt-zeolite, on a carrier such as ceramic. On the other hand, the catalyst-equipped filter 174 has a large number of flow paths formed by a honeycomb lattice made of a porous member such as ceramic, and the inlets and outlets of the flow paths are alternately closed by a sealing material. On the surface, for example, a washcoat layer of alumina is provided, and a noble metal such as Pt or Pd or a base metal catalyst such as Cu is supported.
[0074]
As a result, more suitable catalysts 173 and 174 can be used for the respective purposes of NOx reduction and particulate oxidation, and more efficient purification of both components becomes possible.
Also in this example, the exhaust temperature may be directly detected and controlled by the temperature sensor 33 in the same manner as described above. The configuration in this case is as shown in FIG. Others are the same as in the fifth embodiment.
[0075]
Example 7
In this example, NOx purification is performed on the catalyst in the same configuration as that of Example 4, FIGS. 8 and 10 shown in FIGS. 11 and 15, or Example 6 shown in FIGS. The timing of post-injection performed in the latter half of the expansion stroke for supplying hydrocarbons (thermally decomposed fuel) as a reducing agent for use is changed according to the exhaust temperature detected by the temperature estimation means or the temperature sensor 33. This is another embodiment.
As shown by a broken line or a solid curve in FIG. 19, when hydrocarbon is supplied as a reducing agent, the NOx reduction purification efficiency by the catalyst peaks at a certain temperature, and the purification efficiency decreases at both higher and lower temperatures.
[0076]
Further, the temperature at which the peak purification rate can be obtained varies depending on the carbon number of the reducing agent (hydrocarbon), and the higher the carbon number, the higher the temperature. Therefore, NOx reduction purification is more effective when using hydrocarbon A having a small carbon number (for example, 5 or less carbon atoms) as a reducing agent at temperature T1 (for example, 350 ° C.) than using B having a larger carbon number (for example, having 10 or more carbon atoms). Although the efficiency is high, at the temperature T2 (for example, 400 ° C.), conversely, the use of B having a large number of carbons increases the efficiency. On the other hand, if the post-injection timing is always constant as in the conventional device, only the hydrocarbons that have a high degree of decomposition (low carbon number) and high NOx purification efficiency are supplied at a low temperature when the exhaust temperature is high, Conversely, when the exhaust gas temperature is low, only hydrocarbons that can obtain high NOx purification efficiency at a high temperature (large carbon number) are supplied.
[0077]
Therefore, it is impossible to supply fuel having a decomposition degree suitable for each temperature, and high NOx reduction purification efficiency cannot be obtained. On the other hand, the carbon number of the pyrolyzed fuel (hydrocarbon) obtained by the post-injection in the latter half of the expansion stroke differs depending on the post-injection timing as shown in FIG. In other words, 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 is reduced and the carbon number of the resulting hydrocarbon is increased.
Therefore, in this example, hydrocarbons having a carbon number (thermally decomposed fuel) that maximize the NOx reduction and purification efficiency of the catalyst according to the exhaust temperature are supplied as the reducing agent.
[0078]
In other words, since the optimum carbon number of the reducing agent varies depending on the exhaust temperature, the injection timing for post-injection is changed according to the exhaust temperature, and the higher the exhaust temperature, the later the injection timing is delayed to supply a reducing agent having a larger carbon number. Like that. Thus, when the exhaust gas temperature is low, hydrocarbons having a low NOx reduction and purification efficiency and a low carbon number (for example, 5 or less) are supplied at a low temperature. When the exhaust gas temperature is high, the catalyst is heated at a high temperature. A hydrocarbon having a high NOx reduction purification efficiency and a large carbon number (for example, 10 or more) is supplied.
[0079]
In this case, the timing of post-injection is changed in multiple steps or continuously with respect to the exhaust temperature. As a result, the catalyst can be used in a state where the NOx reduction efficiency is always high regardless of the exhaust temperature, and the NOx reduction purification efficiency of the catalyst can be greatly improved.
In this example, the optimum post-injection pattern for each exhaust temperature is stored in advance in the ECU 18 and is determined in the ECU 18 based on the exhaust temperature.
Others are the same as those in Example 4, Example 5, or Example 6.
[0080]
Next, an example in which the method for controlling the post-injection timing in the exhaust gas purification apparatus is applied to the fifth embodiment shown in FIG. 8 will be described with reference to the flowchart shown in FIG.
This flowchart shows an example in which the post-injection timing and amount are controlled based on the particulate accumulation amount m and the exhaust gas temperature t in the filter 171 with catalyst calculated by the ECU 18.
[0081]
First, in S (step) 501, the exhaust temperature t obtained by the ECU 18 based on the outputs of the rotation sensor 30 and the load sensor 31 is read. For example, as shown in FIG. Decide when. In S502, 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. In step S503, the particulate deposition amount m in the filter with catalyst calculated by the ECU 18 is read.
[0082]
Next, in S504, this m is compared with a set value m1 (for example, 10 g) that requires particulate removal, and 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 m1, the process proceeds to S505, and the exhaust temperature t read in S501 is compared with a set value t1 (for example, 400 ° C.) that is the particulate combustion temperature by the catalyst. If the exhaust temperature t is higher than t1, the particulates on the filter with catalyst are combusted by the high-temperature exhaust, and the process directly returns to S501.
[0083]
On the other hand, if the exhaust temperature t is lower than the above-mentioned t1, in S506, a small amount (for example, 5 to 20% of the main injection amount) of fuel is post-injected in the first half of the expansion stroke after the main fuel injection for generating engine output. As a result, the exhaust temperature is raised, and the particulates on the catalyst-equipped filter 171 are combusted.
In step S507, the particulate deposition amount m on the filter is read again. In step S508, the particulate deposition amount m is compared with a particulate deposition amount setting value m2 (for example, 0.5 g) at which the filter regeneration is terminated. If not, the process returns to S506, and when 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.
[0084]
If the above control is applied to the sixth embodiment shown in FIG. 17, NOx and particulates can be purified more efficiently.
In this example as well, the exhaust temperature may be directly detected and controlled by the temperature sensor 33 (FIGS. 10, 15, and 18). The effect in this case is as described above.
[0085]
Example 8
In this example, in Example 5, Example 6, and Example 7, when the particulate deposition amount exceeds a predetermined value and the exhaust temperature is equal to or lower than the predetermined value, the post-injection in the latter half of the expansion stroke is stopped, and the expansion stroke It is another Example which implemented the post injection only in the first half.
That is, in Example 5, Example 6, and Example 7, when the particulate accumulation amount exceeds the set value and the exhaust temperature is equal to or less than the set value, in addition to a very small amount of post-injection in the latter half of the expansion stroke. In the first half of the expansion stroke, a small amount of fuel is post-injected (see FIG. 14). In contrast, in this example, in this case, a very small amount of post-injection is stopped in the latter half of the expansion stroke, and a small amount of fuel is post-injected only in the first half of the expansion stroke (see FIG. 6).
[0086]
This is because if the post-injection in the second half of the expansion stroke is continued in the cylinder chamber where the exhaust temperature has increased due to the post-injection in the first half of the expansion stroke, the post-injection amount in the second half of the expansion stroke may also increase due to the exhaust temperature rise. This is because there is a case where an effective reducing agent cannot be supplied to the NOx catalyst due to combustion. Therefore, when there is a concern about such engine operation, priority is given to suppression of deterioration of fuel consumption, and only after-fuel injection is performed in the first half of the expansion stroke as shown in FIG.
[0087]
Next, FIG. 23 shows a method for controlling the post-injection timing in the exhaust purification apparatus. This is obtained by adding S601 between S405 and S406 in the flowchart of FIG. 16 in the fifth and sixth embodiments. When this example is applied to the seventh embodiment, S601 is added between S505 and S5O6 in FIG. In S601, the post-injection in the latter half of the expansion stroke is stopped.
In this example as well, the exhaust temperature may be directly detected by the temperature sensor 33 as described above.
[0088]
Example 9
This example is another embodiment in which the post-injection is performed only in a specific cylinder in the first to eighth embodiments.
That is, in the first to eighth embodiments, the post-injection is always performed in all cylinders for exhaust gas temperature control or the supply of the reducing agent to the catalyst, whereas in this example, this is performed only in a specific cylinder. To do.
[0089]
Hereinafter, the post-injection in the latter half of the expansion stroke for supplying the reducing agent to the NOx catalyst will be described as an example. As shown in FIG. 29, the conventional apparatus has a very small amount of fuel (for example, 0% of the main injection amount) after the main injection is completed. .3% to 3%) was post-injection, and all cylinders were constantly injecting. Since this post-injection is for supplying hydrocarbons (thermally decomposed fuel) as a reducing agent to the catalyst, it is indispensable for reducing and purifying NOx in the exhaust gas in the catalyst. Since the fuel used deteriorates the fuel efficiency, it is very important to control the amount with a very small amount with high accuracy.
[0090]
Therefore, in the past, in order to control the very small amount of post-injection, an extremely good responsive solenoid valve was required. As a result, the cost and volume of the solenoid valve have increased.
On the other hand, in this example, the post-injection is performed only by the first cylinder as shown in FIG. That is, by performing post-injection for four cylinders only with the first cylinder, the post-injection amount can be made four times the post-injection amount of 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 prior art, so that extremely quick response is not required for the solenoid valve 14, and the cost and size can be greatly reduced.
[0091]
Furthermore, since it is possible to absorb the variation in the injection amount between the nozzles of each cylinder, which is conspicuous in the control of a very small amount of injection, stable performance can be obtained.
Further, in the second to fourth cylinders that do not perform post-injection, the number of seating of the injection nozzle can be reduced as compared with the conventional one, so that the durability of the nozzle seat portion can be greatly improved.
The case where the post-injection is performed only with the first cylinder has been described above as an example, but this may be performed with one or a plurality of other cylinders.
[0092]
Further, in the above description, the post-injection in the latter half of the expansion stroke when supplying the reducing agent necessary for NOx purification has been described as an example, but this raises the exhaust temperature and burns the particulates on the catalyst-equipped filter. Needless to say, the present invention can also be applied to post-injection in the first half of the expansion stroke.
[0093]
In this case, for example, in the case of Example 5, if the particulate accumulation amount exceeds the set value and the exhaust temperature is not more than the set value, a very small amount of post-injection in the latter half of the expansion stroke and a small amount in the first half of the expansion stroke. In addition to the method of performing both post-injections in the pattern shown in FIG. 14 using only the first cylinder, for example, a very small amount of post-injection in the latter half of the expansion stroke is performed in the pattern shown in FIG. A small amount of post-injection may be performed in the pattern shown in FIG.
[0094]
As a result, the number of seats of the injection nozzle of the first cylinder can be reduced, so that the durability of the nozzle seat can be greatly improved. The same applies to other embodiments.
In the above description, the case of post-injection using only the first cylinder or the second cylinder has been described as an example. However, other cylinders may be used.
[0095]
Example 10
As shown in FIG. 25, this example is an example in which after-injection is performed once every M cycles (M ≧ 2, for example, 4) in the ninth embodiment.
That is, in the first cylinder, the conventional M × 4 times of post-injection are performed once every M cycles. Thereby, the request | requirement of the responsiveness with respect to the solenoid valve 14 demonstrated in Example 1 can further be reduced.
The case where the post-injection is performed only with the first cylinder has been described above as an example, but this may be performed with one or a plurality of other cylinders.
Similarly to the ninth embodiment, 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.
[0096]
Example 11
As shown in FIG. 26, the present example is an example in which the post-injection performed only in the first cylinder or a specific cylinder in the ninth and tenth embodiments is sequentially switched in the other cylinders. is there.
That is, for example, each of the first to fourth cylinders performs the post-injection for four cylinders once every four cycles, and the cylinders that perform the post-injection are, for example, the first, second, fourth, and third cylinders. In this case, the change is made sequentially every cycle.
[0097]
Thereby, in addition to the effect demonstrated in the said Example 10, the durability of the injection nozzle sheet | seat part of a 1st cylinder can be improved.
In addition to the method shown in FIG. 26, as a method of sequentially changing the cylinders for post-injection, for example, in the case of a four-cylinder engine, as shown in FIG. 27 and FIG. If only the main injection is performed, the cylinder to be injected next may be sequentially changed so that the main injection and the post injection are performed and the post injection is performed.
[0098]
In the above, the case where the post-injection is performed by only one cylinder in one cycle has been described as an example, but the post-injection may be performed by a plurality of cylinders.
Further, similarly to 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 the drawings]
FIG. 1 is a system configuration diagram of an exhaust emission control device according to a first embodiment.
FIG. 2 is a graph showing the relationship between the post-injection timing, the injection amount (a), and the 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 the relationship between the engine speed and the exhaust temperature with respect to the 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 according to the third embodiment.
FIG. 10 is another system configuration diagram of the exhaust emission control device according to the third embodiment.
FIG. 11 is a system configuration diagram of an exhaust emission control apparatus according to a fourth embodiment.
FIG. 12 is a control flowchart of the exhaust emission control device according to the fourth embodiment.
FIG. 13 is a diagram showing the relationship between the crank angle and the fuel injection amount in the fourth embodiment (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 Embodiment 4 (when the exhaust temperature is equal to or lower than a predetermined value).
FIG. 15 is another system configuration diagram of the exhaust emission control device according to the fourth embodiment.
FIG. 16 is a control flowchart of the exhaust gas purification apparatus according to the fifth embodiment.
FIG. 17 is a system configuration diagram of an exhaust emission control device according to a sixth embodiment.
18 is another system configuration diagram of the exhaust emission control device of Embodiment 6. FIG.
19 is a graph showing the relationship between catalyst temperature and nitrogen oxide purification rate in Example 7. FIG.
20 is a graph showing the relationship between the timing of post-injection and the number of carbon atoms of hydrocarbons generated in Example 7. FIG.
FIG. 21 is a control flowchart of the exhaust emission control device according to the seventh embodiment.
22 is a graph showing the relationship between the exhaust temperature and the timing of post-injection in Example 7. FIG.
FIG. 23 is a control flowchart of the exhaust emission control device according to the eighth embodiment.
24 is a graph showing the relationship between the fuel injection generation timing and the injection amount in each cylinder in Embodiment 9. FIG.
FIG. 25 is a diagram showing the relationship between the fuel injection generation timing and the injection amount in each cylinder in the tenth embodiment.
FIG. 26 is a diagram showing the relationship between the fuel injection generation timing and the injection amount in each cylinder in the eleventh embodiment.
FIG. 27 is another view (part 1) showing the relationship between the fuel injection generation timing and the injection amount in each cylinder in the eleventh embodiment.
FIG. 28 is another view (No. 2) showing the relationship between the fuel injection generation timing and the injection amount in each cylinder in the eleventh embodiment.
FIG. 29 is another diagram showing the relationship between the fuel injection generation timing and the injection amount in each cylinder in the conventional device.
[Explanation of symbols]
1. . . Exhaust purification equipment,
17. . . Exhaust treatment means (device),
18. . . Fuel injection control means (ECU),

Claims (11)

Fuel injection means provided for each cylinder, nitrogen oxide reduction means interposed in the exhaust passage, operating state detecting means, and exhaust temperature estimating means for estimating the exhaust temperature based on the output from the operating state detecting means And a temperature comparison means for comparing the output from the exhaust temperature estimation means with a predetermined value, and the fuel injection timing and the fuel injection amount in the fuel injection means are determined by the output of the temperature comparison means to operate the fuel injection means. An internal combustion engine exhaust gas purification device having fuel injection control means,
The fuel injection control means performs the fuel post-injection in the latter half of the expansion stroke after the main fuel injection for generating engine output when the exhaust temperature is higher than a predetermined value, and when the exhaust temperature is lower than the predetermined value. In addition to the above, an exhaust purification device for an internal combustion engine that commands to perform post-injection even in the first half of the expansion stroke. Fuel injection means provided for each cylinder, particulate collection means interposed in the exhaust passage, nitrogen oxide reduction means interposed in the exhaust passage, and inlet side of the particulate collection means Provided pressure detecting means, operating state detecting means, exhaust temperature estimating means for estimating the exhaust temperature from the output from the operating state detecting means, and temperature comparing means for comparing the output from the exhaust temperature estimating means with a predetermined value And a deposit amount calculating means for calculating a particulate deposit amount in the particulate collecting means based on outputs from the operating state detecting means and the pressure detecting means, and a deposit amount for comparing the output from the deposit amount calculating means with a predetermined value. A fuel injection timing and a fuel injection amount in the fuel injection means are determined by outputs from the comparison means, the temperature comparison means and the deposit amount comparison means, and the fuel injection means is operated. In the exhaust purification system of an internal combustion engine having a fuel injection control means,
The fuel injection control means performs post-injection after main fuel injection for generating engine output in the latter half of the expansion stroke when the particulate accumulation amount in the particulate collection means is less than a predetermined value. If the particulate accumulation amount on the collecting means exceeds a predetermined value and the exhaust temperature is not more than a predetermined value, in addition to this, the exhaust of the internal combustion engine is commanded to be executed even in the first half of the expansion stroke Purification equipment. Fuel injection means provided for each cylinder, particulate collection means interposed in the exhaust passage, nitrogen oxide reduction means interposed in the exhaust passage, and inlet side of the particulate collection means The provided pressure detection means, the operation state detection means, the exhaust temperature estimation means for estimating the exhaust temperature based on the output of the operation state detection means, and the fuel injection timing is corrected and changed based on the output of the exhaust temperature estimation means The fuel injection timing correcting means for performing the temperature comparison means for comparing the output of the exhaust gas temperature estimating means with a predetermined value, and the particulate accumulation amount in the particulate collecting means based on the outputs of the operating state detecting means and the pressure detecting means. On the basis of the outputs of the accumulation amount calculating means for calculating the accumulation amount, the accumulation amount comparing means for comparing the output of the accumulation amount calculating means with a predetermined value, and the outputs of the temperature comparing means and the deposit amount comparing means. In the exhaust purification system of an internal combustion engine having a fuel injection control means for actuating the decided fuel injection means and a fuel injection timing and the fuel injection amount in the fuel injection means,
The fuel injection control means implements fuel post-injection in the latter half of the engine expansion stroke after the main fuel injection for generating engine output when the particulate accumulation amount in the particulate collection means is less than a predetermined value. Command
When the particulate accumulation amount in the particulate collection means exceeds a predetermined value and the exhaust temperature is lower than the predetermined value, in addition to that, the post-injection of fuel is commanded to be performed even in the first half of the expansion stroke,
In addition, the injection timing of the post-injection in the latter half of the expansion stroke when the particulate accumulation amount is not more than a predetermined value is changed based on the output of the exhaust temperature estimating means, and the post-injection timing is changed from the set timing as the exhaust temperature becomes higher. An exhaust emission control device for an internal combustion engine, characterized by commanding to delay. According to claim 2 or claim 3, beyond the particulate matter deposit amount is the predetermined value in the particulate collecting means, and when the exhaust temperature is below the predetermined value, without performing the post injection in the latter half the expansion stroke An exhaust purification device for an internal combustion engine, which performs only post-injection in the first half of the expansion stroke. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 4 , wherein the post-injection of the fuel is performed only for a specific cylinder. In any one of claims 1 to 4, the cylinder causing the post injection in the expansion stroke the first half, the exhaust purification system of an internal combustion engine, characterized in that the cylinders to perform the post injection in the latter half the expansion stroke are different . According to claim 5 or claim 6, summarizes the injection quantity of post injection for multiple cycles performed at a time, the exhaust purification system of an internal combustion engine, characterized in that to reduce the number of post-injection. The exhaust emission control device for an internal combustion engine according to any one of claims 5 to 7 , wherein a cylinder for performing post-injection is sequentially switched and changed. In any one of claims 1-8, wherein the exhaust instead of the temperature estimation means, an exhaust purifying apparatus for an internal combustion engine, characterized in that to detect the exhaust gas temperature directly by the temperature detecting means. 10. The post-injection performed in the first half of the expansion step according to any one of claims 1 to 9, wherein fuel having a main injection amount of 5 to 20% for generating engine output is injected into the cylinder chamber. An exhaust purification device for an internal combustion engine. The post-injection performed in the second half of the expansion step in any one of claims 1 to 9 is to inject a fuel having a main injection amount of 0.3 to 5% for generating engine output into the cylinder chamber. An exhaust gas purification apparatus for an internal combustion engine characterized by the above.

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