JP2013104380A - Regenerating device of exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent an excessive temperature rise of an exhaust emission control means and allow regenerating time to be reduced by enabling an accurate temperature control of the exhaust emission control means.SOLUTION: A regenerating device of an exhaust emission control device which regenerates a DPF 21 by increasing temperature of exhaust flowing into the DPF 21 provided to an exhaust passage 20 of an engine 1 through post injection, consists of a first temperature drop function which stops the post injection at regeneration of the DPF 21 and reduces temperature of exhaust flowing into the DPF 21, a second temperature drop function which contains a heat exchange means 53 in a bypass passage 52 by connecting the bypass passage 52 in parallel to the exhaust passage 20 on the upstream side of the DPF 21, controls a flow rate of exhaust passing through the bypass passage 52 and reduces the temperature of exhaust flowing into the DPF 21. On the basis of a temperature state of the DPF 21, the first temperature drop function and second temperature drop function can be selected or both utilized to operate the device.

Description

  The present invention relates to a temperature control technique during regeneration of an exhaust purification device provided in an exhaust passage of an engine.

  A diesel particulate filter (hereinafter referred to as DPF) is known as an exhaust gas purification device that purifies exhaust gas from a diesel engine. The DPF is provided in the exhaust passage and collects particulate matter (particulate matter, hereinafter referred to as PM) in the exhaust. In addition, a technique is known in which the DPF is reheated by raising the temperature of the DPF to combust and remove PM trapped in the DPF.

The PM deposited on the DPF contains a large amount of soot containing carbon as a main component, generates heat due to combustion during regeneration, and the DPF may rise above the exhaust temperature. In particular, when a large amount of PM is accumulated, if the PM burns at a time, the temperature of the DPF increases significantly, and the DPF may be burned out.
Therefore, a technology has been proposed in which an exhaust cooling device is provided in the exhaust passage, and when the temperature of the exhaust gas is excessively high, the exhaust gas flowing into the exhaust purification unit is cooled by the exhaust cooling device to prevent an excessive temperature rise of the exhaust purification unit. (Patent Document 1).

JP-A-5-321640

  However, in the said patent document 1, it has the structure which controls whether exhaust_gas | exhaustion passes an exhaust_gas | exhaustion cooling device by switching an exhaust passage with an exhaust control valve. Here, in order to shorten the regeneration time in order to ensure fuel economy and exhaust purification performance, it is desirable to set the temperature of the exhaust purification means as high as possible, but there is an increased risk that the exhaust purification means will overheat. End up. Therefore, in Patent Document 1, although it is possible to reduce the risk of excessive temperature rise by adopting a large-capacity exhaust cooling device, it causes an increase in cost and installation space, and a large-capacity exhaust cooling. There is a risk that fine temperature control becomes difficult in the apparatus.

  The present invention has been made in order to solve such a problem, and an object of the present invention is to reliably prevent an excessive temperature rise of the exhaust purification means during regeneration and to provide an accurate exhaust purification means. A regenerator for an exhaust gas purification apparatus that can control the temperature of the exhaust gas and that can shorten the regenerative time is provided.

  In order to achieve the above object, a regenerator for an exhaust gas purification device according to claim 1 increases the temperature of the exhaust gas flowing into the exhaust gas purification unit provided in the exhaust passage of the internal combustion engine to regenerate the exhaust gas purification unit. A regenerator for a purifying device, wherein the first temperature control means for controlling the amount of heat supplied to the exhaust by controlling the amount of fuel added to the exhaust flowing into the exhaust purifying means, and the upstream side of the exhaust purifying means A second temperature control unit that includes a heat exchange unit in the exhaust passage, controls a flow rate of exhaust gas passing through the heat exchange unit, and controls the amount of heat recovered from the exhaust gas flowing into the exhaust gas purification unit; and a temperature of the exhaust gas purification unit Control for selecting or using the first temperature control means and the second temperature control means based on the temperature state detection means for detecting the state and the temperature state of the exhaust purification means detected by the temperature state detection means Means and And wherein the door.

  According to a second aspect of the present invention, there is provided a regeneration device for an exhaust gas purification device according to the first aspect, wherein the first temperature control means reduces the amount of fuel added during regeneration of the exhaust gas purification means, and reduces exhaust gas flowing into the exhaust gas purification means. The second temperature control means includes a bypass path connected in parallel to the exhaust passage on the upstream side of the exhaust purification means, and includes a heat exchange means in the bypass path. The exhaust gas purifying means includes a second temperature lowering means for controlling the flow rate of the exhaust gas passing through the bypass path and lowering the temperature of the exhaust gas flowing into the exhaust gas purifying means.

According to a third aspect of the present invention, there is provided a regeneration device for an exhaust purification device according to the first or second aspect, wherein the control means is configured to overheat the exhaust purification means based on the temperature state of the exhaust purification means detected by the temperature detection means. The second temperature lowering means is operated in preference to the first temperature lowering means based on the possibility of excessive temperature rise.
According to a fourth aspect of the present invention, there is provided a regeneration device for an exhaust purification device according to the second or third aspect, wherein the control means controls the temperature state of the exhaust purification means based on the temperature of the exhaust purification means and the temperature increase rate of the exhaust purification means. It is characterized by determining.

According to the first aspect of the present invention, the first temperature control means controls the temperature of the exhaust gas flowing into the exhaust purification means by increasing / decreasing the fuel addition amount, so that the temperature of the exhaust purification means can be greatly changed. .
Further, since the second temperature control means controls the temperature of the exhaust gas by passing the exhaust gas through the heat exchanging means, the exhaust temperature can be changed quickly, and the temperature of the exhaust gas purification means can be changed in a timely manner. The temperature control of the exhaust purification means can be performed with high accuracy.

Then, based on the temperature state of the exhaust purification means, the first temperature control means and the second temperature control means are selected or used in combination, and thus the two temperature control means having different characteristics are exhausted. By appropriately using the temperature based on the temperature state of the means, the temperature of the exhaust purification means can be accurately controlled.
According to the second aspect of the present invention, the first temperature reduction means reduces the temperature of the exhaust gas flowing into the exhaust gas purification means by reducing the fuel injection amount in the internal combustion engine. It can be greatly reduced.

Further, since the second temperature lowering means causes the exhaust gas to pass through the heat exchanging means and lowers the temperature of the exhaust gas, the exhaust temperature can be lowered quickly, and the temperature of the exhaust gas purifying means can be lowered at the time of regeneration. Thus, the temperature control of the exhaust purification means can be performed with high accuracy.
Then, at the time of regeneration of the exhaust purification means, the first temperature reduction means and the second temperature reduction means are selected or used together based on the temperature state of the exhaust purification means, and thus the characteristics are different. By appropriately using the two temperature lowering means based on the temperature state of the exhaust purification means, an excessive temperature rise of the exhaust purification means can be surely prevented and the temperature of the exhaust purification means can be accurately controlled. . Therefore, it becomes possible to set the target temperature of the exhaust gas purification means at the time of regeneration high, and the regeneration time can be shortened.

According to the invention of claim 3, the possibility of excessive temperature rise of the exhaust purification means is determined based on the temperature state of the exhaust purification means, and the first temperature drop is determined based on the possibility of excessive temperature rise. Since the second temperature lowering means is operated in preference to the first means, the operation opportunities of the second temperature lowering means are increased over the first temperature lowering means, and the temperature control of the exhaust purification means is performed with higher accuracy. Can do.
According to the invention of claim 4, since the temperature state of the exhaust purification means is determined not only by the temperature of the exhaust purification means but also by the temperature increase rate of the exhaust purification means, the exhaust purification means is overheated. Can be more accurately determined. Therefore, by reducing the temperature of the exhaust gas flowing into the exhaust gas purification unit based on the temperature state of the exhaust gas purification unit, it is possible to more reliably avoid the excessive temperature rise of the exhaust gas purification unit.

1 is a configuration diagram of an intake / exhaust system of a diesel engine to which a regeneration device for an exhaust gas purification apparatus according to a first embodiment of the present invention is applied. 1 is a structural diagram of an exhaust heat recovery apparatus according to a first embodiment of the present invention. It is a map for selection of a temperature fall function.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration of an intake / exhaust system of a diesel engine (hereinafter referred to as an engine 1) to which a regeneration device for an exhaust gas purification apparatus according to a first embodiment of the present invention is applied.
The engine 1 is, for example, a common rail type in-line multi-cylinder diesel engine mounted on a vehicle. The cylinder head 2 of the engine 1 is provided with an electromagnetic fuel injection valve 4 for injecting fuel into the combustion chamber 3 for each cylinder. Each fuel injection valve 4 is connected to a common rail (not shown), and high-pressure fuel is supplied from the common rail.

An intake passage 10 of the engine 1 is provided with an electromagnetic intake throttle valve 11 that adjusts the intake air amount, and an airflow sensor 12 that detects an intake air flow rate upstream thereof.
The exhaust passage 20 of the engine 1 is provided with a diesel particulate filter (DPF21: exhaust purification means) that collects particulate matter (PM) in the exhaust. For example, the DPF 21 is formed by alternately closing the upstream and downstream sides of the passage of the honeycomb carrier with plugs, and a catalytic noble metal such as platinum (Pt), palladium (Pd), and rhodium (Rh) on the porous wall forming the passage. Is formed.

The exhaust passage 20 upstream of the DPF 21 is provided with an oxidation catalyst (hereinafter referred to as DOC22). The DOC 22 is formed, for example, by supporting a catalyst noble metal such as platinum (Pt), palladium (Pd), rhodium (Rh) on a porous wall forming a passage, and oxidizes CO and HC in the exhaust. together is converted to CO ₂ and H ₂ O Te has a function of NO in the exhaust is oxidized to generate NO _2.

Further, an exhaust gas temperature sensor 30 that detects the exhaust gas temperature immediately after passing through the oxidation catalyst 22 is provided on the downstream side of the oxidation catalyst 22. An exhaust gas temperature sensor 31 that detects the exhaust gas temperature immediately after passing through the DPF 21 is provided on the downstream side of the DPF 21. Further, a differential pressure sensor 32 that detects a differential pressure between the upstream side and the downstream side of the DPF 21 is provided.
An electronic control unit (hereinafter referred to as ECU 40) (control means) is a control device for performing comprehensive control including operation control of the engine 1, and includes an input / output device, a storage device (ROM, RAM, nonvolatile RAM). Etc.), a central processing unit (CPU) and the like.

On the input side of the ECU 40, in addition to the air flow sensor 12, the exhaust temperature sensors 30, 31 and the differential pressure sensor 32 described above, a crank angle sensor 33 for detecting the crank angle, and an accelerator position sensor 34 for detecting the depression amount of the accelerator pedal. , And a vehicle speed sensor 35 for detecting the vehicle speed are connected, and detection information from these sensors is input.
On the other hand, various output devices such as the fuel injection valve 4 and the intake throttle valve 11 are connected to the output side of the ECU 40, and the fuel calculated by the ECU 40 based on detection information from various sensors is connected to these various output devices. The injection amount, the fuel injection timing, and the like are output, and thereby the intake throttle valve 11 and the fuel injection valve 4 are controlled at an appropriate timing.

When the DOC 22 is arranged upstream of the DPF 21 as described above, NO ₂ generated in the DOC 22 flows into the DPF 21 during normal engine operation, and is a carbon component in PM collected and accumulated in the DPF 21. It reacts with a certain trap to oxidize it. Oxidized soot becomes CO _{2 and} is removed from the DPF 21, whereby continuous regeneration is performed in which the DPF 21 is continuously regenerated.

On the other hand, depending on the operating condition of the engine 1, the DPF 21 may not be sufficiently regenerated only by the continuous regeneration. Therefore, the ECU 40 has a function (regeneration device) for controlling the operation of the engine 1 to forcibly regenerate the DPF 21.
Specifically, the ECU 40 calculates the PM accumulation amount in the DPF 21 from the differential pressure detected by the differential pressure sensor 32. When the calculated accumulation amount is equal to or greater than the allowable accumulation amount set in advance in the experiment, the exhaust temperature after passing through the DPF 21 detected by the exhaust temperature sensor 31, that is, the temperature of the DPF 21, is a target regeneration whose target value is the forced regeneration temperature. The forced regeneration temperature is raised so as to reach the temperature.

  In the forced regeneration, post-injection (sub-injection) of fuel is performed so that the forced regeneration temperature is reached after, for example, the expansion stroke after the main injection of fuel during operation of the engine 1, and unburned fuel (HC, CO, etc.) Exhaust gas containing the gas is discharged into the exhaust passage 20. The unburned fuel mixed in the exhaust flows into the DOC 22 and is oxidized, and the exhaust temperature is raised by the reaction heat of oxidation. As a result, the high-temperature exhaust gas flows into the DPF 21 on the downstream side of the exhaust gas, and the PM deposited on the DPF 21 can be heated and burned to forcibly regenerate the DPF 21.

Further, in the present embodiment, an exhaust heat recovery device 50 for recovering exhaust heat is provided.
The exhaust heat recovery device 50 includes a bypass passage 52 provided in parallel to the main exhaust passage 51 that is a part of the exhaust passage 20 between the DOC 22 and the DPF 21, and a heat exchanger 53 provided in the bypass passage 52. (Heat exchange means) and an on-off valve 54 provided at a branch portion between the main exhaust passage 51 and the bypass passage 52.

The heat exchanger 53 is introduced with cooling water of the engine 1 and has a function of exchanging heat between the exhaust gas passing through the bypass passage 52 and the cooling water.
The on-off valve 34 is controlled by the ECU 40 and has a function of opening and closing the main exhaust passage 51, and is between a fully open state in which the main exhaust passage 51 is fully opened and a fully closed state in which the main exhaust passage 51 is fully closed. Switching is possible. The bypass passage 52 has a smaller flow passage cross-sectional area than the main exhaust passage 51 and is provided with a heat exchanger 53. Therefore, the bypass passage 52 has a larger flow passage resistance, so that the exhaust discharged from the oxidation catalyst 22 when the on-off valve 54 is fully opened. Most of them pass through the main exhaust passage 51. On the other hand, when the on-off valve 54 is fully closed, all the exhaust discharged from the oxidation catalyst 22 passes through the bypass passage 52. Therefore, the on-off valve 54 has a function equivalent to the function of switching the flow path so that the exhaust discharged from the oxidation catalyst 22 passes through either the bypass path 52 or the main exhaust path 51.

Then, the ECU 40 controls the opening / closing valve 54 so that the exhaust gas passes through the bypass passage 52, so that heat exchange is performed between the exhaust gas passing through the bypass passage 52 and the cooling water by the heat exchanger 53. Exhaust heat can be recovered.
The ECU 40 controls the closing of the on-off valve 34 so that the exhaust gas passes through the bypass 52 when the engine 1 is cold-started (for example, when the coolant temperature is equal to or lower than a predetermined temperature). Thereby, since the cooling water of the engine 1 is warmed, when the engine 1 is cold-started, warm-up can be promoted using exhaust heat, and the warm-up operation time can be shortened.

Further, the engine 1 of the present embodiment is provided with two temperature lowering functions for lowering the exhaust gas temperature flowing into the DPF 21 in order to prevent an excessive temperature rise of the DPF 21 during the forced regeneration.
In the first temperature reduction function (first temperature reduction means, first temperature control means) of the two temperature reduction functions, the ECU 40 causes the fuel injection valve 4 to stop post injection during forced regeneration. Control the operation. Thereby, the supply of unburned fuel to the DOC 22 is stopped, oxidation at the DOC 22 is suppressed, and the temperature of the exhaust gas flowing into the DPF 21 is lowered.

In the second temperature reduction function (second temperature reduction means, second temperature control means) of the two temperature reduction functions, the ECU 40 opens the on-off valve 54 so that the exhaust gas passes through the bypass passage 52. Control the operation. As a result, the exhaust gas passing through the bypass passage 52 exchanges heat with the cooling water in the heat exchanger 53, and the exhaust gas temperature decreases.
The ECU 40 selects or executes the first temperature lowering function and the second temperature lowering function based on the temperature state of the DPF 21 during forced regeneration.

FIG. 3 is a map for selecting the temperature lowering function.
Specifically, during forced regeneration, the ECU 40 sequentially inputs the exhaust temperature from the exhaust temperature sensor 31 as the DPF temperature, and based on the DPF temperature and the DPF temperature increase rate that is the amount of increase in the DPF temperature per unit time, Using FIG. 3, the risk that the DPF 21 is overheated is determined in three stages of zones 1 to 3.

As shown in FIG. 3, when the DPF temperature is low and the DPF temperature increase rate is a low increase rate, the risk of overheating is high in the zone 1 where the risk of overheating is low, and at the high temperature and high increasing rate. The high zone 3 is set to be determined to be zone 2 in which the risk of overheating is moderate between zone 1 and zone 2.
Then, in the zone 1, the ECU 40 does not execute any of the first temperature lowering function and the second temperature lowering function, and performs forced regeneration as it is.

In zone 2, only the second temperature lowering function of the two temperature lowering functions is executed.
In zone 3, both the first temperature lowering function and the second temperature lowering function are executed.
By controlling as described above, in the present embodiment, at the time of forced regeneration, the temperature rise of the DPF 21 is regulated by selecting or using the first temperature lowering function and the second temperature lowering function. . Specifically, when the temperature state of the DPF 21 is low in the risk of overheating, neither the first temperature lowering function nor the second temperature lowering function is operated, and the risk of overheating is moderate. Causes only the second temperature lowering function to be executed. Furthermore, when the risk of overheating is high, both the first temperature lowering function and the second temperature lowering function are executed.

Since the first temperature lowering function controls the operation of the fuel injection valve 4 so as to stop the post-injection, the DPF temperature can be significantly reduced. Moreover, since post injection is stopped, wasteful fuel consumption can be suppressed.
The second temperature lowering function can cool the exhaust gas instantaneously by passing the exhaust gas through the heat exchanger 53. Therefore, the temperature of the DPF 21 can be lowered at an appropriate timing with good responsiveness, and the temperature of the DPF 21 can be adjusted with high accuracy.

  As described above, in this embodiment, two temperature lowering functions having different characteristics are provided, and these temperature lowering functions are selected and used in accordance with the degree of the risk of excessive temperature rise, so that an excessive temperature rise of the DPF 21 occurs. Can be reliably prevented, and the temperature of the DPF 21 can be quickly lowered with good timing. Therefore, the temperature of the DPF 21 can be set as high as possible during regeneration, and the regeneration time can be shortened.

  Further, in the present embodiment, the second temperature lowering function is performed in the zone 2 where the risk of overheating is moderate, and the second temperature lowering function and the first temperature are performed in the zone 3 where the risk of overheating is high. Since the lowering function is implemented, the second temperature lowering function is prioritized over the first temperature lowering function. Therefore, the opportunity for performing the second temperature lowering function is increased as compared with the first temperature lowering function, the temperature of the DPF 21 can be quickly lowered at a good timing, and the temperature control of the DPF 21 can be performed with higher accuracy. It has become.

Further, since the ECU 40 determines the risk of overheating as the temperature state of the DPF 21 together with the temperature rise rate of the DPF 21 as well as the temperature of the DPF 21, it more accurately determines the risk that the DPF 21 will overheat. It is possible to avoid the excessive temperature rise of the DPF 21 more reliably.
Further, even when the regeneration is not performed, it is possible to accurately control the temperature of the DPF by appropriately selecting or implementing the first temperature lowering function and the second temperature lowering function.

In addition, this invention is not limited to the above embodiment.
For example, the temperature state of the DPF 21 may be subdivided in the zone 2, and the opening degree of the on-off valve 54 may be changed in a plurality of steps or continuously according to the risk of excessive temperature rise based on this subdivided temperature state. In this way, the temperature control of the DPF 21 can be further accurately performed.

In the first temperature lowering function, the post injection amount may be controlled not to be stopped but to be decreased.
Further, the present invention can be applied not only to the regeneration of the DPF but also to temperature control of various exhaust purification apparatuses such as other filters and catalysts. However, the present invention is particularly effective for an exhaust emission control device such as a DPF, in which accumulated deposits are likely to burn during regeneration and become overheated.

1 Engine 4 Fuel Injection Valve 20 Exhaust Passage 21 DPF
22 DOC
31 Temperature sensor 40 ECU
50 Exhaust heat recovery device 52 Bypass path 53 Heat exchanger

Claims (4)

A regeneration device for an exhaust purification device for increasing the temperature of exhaust gas flowing into exhaust purification means provided in an exhaust passage of an internal combustion engine and regenerating the exhaust purification means,
First temperature control means for controlling the amount of heat supplied to the exhaust by controlling the amount of fuel added to the exhaust flowing into the exhaust purification means;
A second heat exchanger for controlling the amount of heat recovered from the exhaust gas flowing into the exhaust gas purification device by controlling a flow rate of the exhaust gas passing through the heat exchange device; Temperature control means;
Temperature state detection means for detecting a temperature state of the exhaust purification means;
Control means for selecting or operating the first temperature control means and the second temperature control means based on the temperature state of the exhaust gas purification means detected by the temperature state detection means. A regenerator for an exhaust gas purification device. The first temperature control means includes first temperature lowering means for reducing the temperature of exhaust flowing into the exhaust purification means by reducing the amount of fuel added during regeneration of the exhaust purification means,
The second temperature control means includes a bypass path connected in parallel to an exhaust passage upstream of the exhaust purification means, the heat exchange means is provided in the bypass path, and the bypass path is provided during regeneration of the exhaust purification means. The regeneration of the exhaust gas purification apparatus according to claim 1, further comprising a second temperature reducing means for controlling the flow rate of the exhaust gas passing through the exhaust gas to lower the temperature of the exhaust gas flowing into the exhaust gas purification means. apparatus.   The control means determines the possibility of overheating of the exhaust purification means based on the temperature state of the exhaust purification means detected by the temperature state detection means, and based on the possibility of overheating. The regeneration device for an exhaust gas purification apparatus according to claim 2, wherein the second temperature lowering means is operated with priority over the first temperature lowering means.   The exhaust gas purification unit according to claim 2 or 3, wherein the control unit determines a temperature state of the exhaust gas purification unit based on a temperature of the exhaust gas purification unit and a temperature increase rate of the exhaust gas purification unit. Device playback device.

Images