JP6203658B2 - Exhaust gas purification system - Google Patents

Description

  The present invention relates to an exhaust gas purification system that purifies exhaust gas of a diesel engine.

As shown in Patent Document 1, a configuration including an oxidation catalyst and a filter is known as an exhaust gas purification device (DPF unit) for a diesel engine. The oxidation catalyst oxidizes unburned fuel, carbon monoxide, nitrogen monoxide and the like contained in the exhaust gas. The filter is disposed on the exhaust gas downstream side of the oxidation catalyst, and collects PM (particulate matter) contained in the exhaust gas. PM deposited on the filter can be removed by burning with O ₂ or NO ₂ .

  In addition to the configuration in which an oxidation catalyst and a filter are separately disposed, an exhaust gas purification device in which an oxidation catalyst is supported on a filter as shown in Patent Document 2 is known. In this exhaust gas purification device, the temperature between the oxidation catalyst and the filter cannot be measured. Therefore, when performing temperature control, it is necessary to use the temperature on the downstream side of the filter.

JP 2013-122182 A JP 2007-92662 A

  By the way, when performing the regeneration control of the filter, the exhaust gas purifying apparatus burns soot by raising the temperature in the DPF by increasing the injection amount of the post injection or the like.

  As in Patent Literature 1, when the oxidation catalyst and the filter are separate, the temperature between the oxidation catalyst and the filter can be detected. Therefore, in this type of exhaust gas purifying apparatus, the temperature can be raised to the target value by controlling the injection amount of the post injection using feedback control.

  However, in this case, when the rate of temperature increase is high, feedback control is performed when the difference between the target temperature and the current temperature is large, so that the amount of post injection increases, and overshoot is likely to occur ( (See the dashed line in FIG. 9). On the other hand, when the rate of temperature rise is low, overshoot is unlikely to occur, but the time until the target temperature is reached becomes long (see the chain line in FIG. 10).

  In the configuration of Patent Document 2, the temperature between the oxidation catalyst and the filter cannot be detected. If feedback control is performed using the temperature downstream of the filter, the response is poor and appropriate control cannot be performed. For example, the temperature of the filter may increase excessively. Therefore, in the configuration of Patent Document 2, feedback control based on temperature cannot be performed appropriately.

  The present invention has been made in view of the above circumstances, and its main object is to provide an exhaust gas purification device in which the oxidation catalyst and the filter are separate, and to quickly prevent the temperature of the exhaust gas purification device from overshooting. It is another object of the present invention to provide an exhaust gas purification system that raises the exhaust gas.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

According to an aspect of the present invention, an exhaust gas purification system having the following configuration is provided. That is, the exhaust gas purification system includes an exhaust gas purification device, a filter temperature sensor, and a control unit. The exhaust gas purification device is disposed in an exhaust path of an engine including a fuel injection device, and includes an oxidation catalyst and a filter disposed on the exhaust downstream side of the oxidation catalyst. The filter temperature sensor detects an oxidation catalyst outlet temperature that is a temperature between the oxidation catalyst and the filter. The control unit performs regeneration control for incinerating particulate matter accumulated in the exhaust gas purification device by increasing the oxidation catalyst outlet temperature. The regeneration control includes recovery regeneration control, and the recovery regeneration control includes recovery first regeneration control and recovery second regeneration control that is performed at a higher temperature and for a shorter time than the recovery first regeneration control. . When the control unit performs regeneration control by increasing the oxidation catalyst outlet temperature when shifting from the recovery first regeneration control to the recovery second regeneration control, the control unit sets the oxidation catalyst outlet temperature detected by the filter temperature sensor. calculating a temperature rise rate on the basis, according to the previous SL switching temperature or switching time is the oxidation catalyst outlet temperature to switch the feedback control of the control for increasing the oxidation catalyst outlet temperature from the open loop control the temperature increase rate To decide . The control unit calculates the temperature increase rate for determining the switching temperature or the switching time, and the oxidation catalyst outlet temperature includes a temperature of the first recovery regeneration control and a temperature of the second recovery regeneration control. And until it reaches the middle temperature.

In general, when temperature control is performed only by feedback control, complicated control such as changing a control coefficient or the like is required in order to achieve both a reduction rate of deviation and prevention of overshoot at the same time. In this regard, by performing the control of the present invention, it is possible to prevent overshoot when the temperature rise rate is high, for example, with simple control, and to quickly reach the target temperature even when the temperature rise rate is low. be able to. In addition, since it is preferable to perform temperature control so that overshoot does not occur quickly at the time of transition from recovery first regeneration control to recovery second regeneration control, the effect of the control of the present invention can be exhibited more effectively. Can do.

  In the exhaust gas purification system, it is preferable that the control unit delays the switching timing from the open loop control to the feedback control as the temperature increase rate is higher.

  Thus, it is possible to shorten the time to reach the target temperature when the temperature increase rate is low while preventing overshoot when the temperature increase rate is high.

  The exhaust gas purification system preferably has the following configuration. That is, the control unit calculates a switching temperature, which is a temperature at which the control is switched, based on the temperature increase rate, and switches from open loop control to feedback control when the oxidation catalyst outlet temperature reaches the switching temperature. The temperature increase rate and the switching temperature are in a proportional relationship.

  Thus, by determining whether or not to switch control using temperature, it is possible to switch control at a more accurate timing than when using time, for example. In addition, since the temperature increase rate and the switching temperature are in a proportional relationship, an appropriate switching temperature can be calculated by a simple process.

FIG. Explanatory drawing which shows a gas flow and various sensors typically. Explanatory drawing which shows the name and timing of fuel injection typically. A table explaining the types and characteristics of playback control. The flowchart which shows the process at the time of performing recovery control from stationary regeneration control. The flowchart which shows temperature control when transfering from 1st recovery reproduction | regeneration control to 2nd recovery reproduction | regeneration control. The graph which shows the change of DOC exit temperature, and a temperature rise rate. The graph which shows the correspondence of switching temperature and a temperature rise rate. The graph which shows the change of the DOC exit temperature of a prior art example and this embodiment, and the change of post injection quantity in the case where a temperature rise rate is high. The graph which shows the change of the DOC exit temperature of a prior art example and this embodiment, and the change of post injection quantity in the case where a temperature rise rate is low.

  Next, embodiments of the present invention will be described with reference to the drawings. The engine 100 is a diesel engine and is mounted on a work machine, a ship, and the like.

  As shown in FIG. 1, the engine 100 includes an intake pipe 20, a supercharger 21, a supercharge pipe 24, an intake throttle 25, an intake manifold 26, and a breather hose 27 as intake system members. Prepare.

  The suction pipe 20 sucks gas from the outside. The suction pipe 20 includes a filter that removes dust and the like in the gas.

  The supercharger 21 includes a turbine housing 22 and a compressor housing 23. A turbine wheel (not shown) in the turbine housing 22 is configured to rotate using exhaust gas. An unillustrated compressor wheel in the compressor housing 23 is connected to the same shaft 21a (FIG. 2) as the turbine wheel, and rotates as the turbine wheel rotates. The supercharger 21 can forcibly intake air by compressing air by rotating the compressor wheel.

  The gas sucked by the supercharger 21 flows through the supercharging pipe 24. One side of the supercharging pipe 24 is connected to the supercharger 21, and the other side of the supercharging pipe 24 is connected to the intake throttle 25.

  The intake throttle 25 includes an intake valve. The intake throttle 25 can change the amount of gas supplied to the cylinder by adjusting the opening of the intake valve. The gas that has passed through the intake throttle 25 is sent to the intake manifold 26. The opening degree of the intake valve is controlled by an ECU (engine control unit, control unit) 50 shown in FIG.

  The intake manifold 26 divides the gas supplied from the intake throttle 25 into a number corresponding to the number of cylinders (four in the present embodiment) and supplies it to the cylinder head 10. The cylinder head 10 is provided with a cylinder head cover 11 and an injector (fuel injection device) 12.

  The injector 12 injects fuel into the combustion chamber at a predetermined timing. Specifically, the injector 12 is configured to perform main injection near the top dead center (TDC) as shown in FIG. Further, the injector 12 can perform pre-injection for noise reduction immediately before the main injection, or can perform pilot injection for NOx reduction and noise reduction at a timing before the pre-injection. Further, the injector 12 performs after injection for the purpose of reducing PM and promoting exhaust gas purification immediately after the main injection, or performing post injection for the purpose of raising the temperature at a later timing of the after injection. can do.

  Power can be generated by injecting fuel and driving the piston in this way. Blow-by gas and exhaust gas are generated in the combustion chamber.

  The breather hose 27 supplies blow-by gas generated in the combustion chamber to the suction pipe 20. Thereby, it can prevent that unburned gas is discharged | emitted outside.

  Further, as shown in FIG. 2, an intake pressure sensor 51 and an intake air temperature sensor 52 are attached to the intake manifold 26.

  The intake pressure sensor 51 detects the gas pressure in the intake manifold 26 and outputs it to the ECU 50. The ECU 50 recognizes the input pressure as the intake pressure. The intake air temperature sensor 52 detects the temperature of the gas in the intake manifold 26 and outputs it to the ECU 50. Note that the intake pressure sensor 51 and the intake temperature sensor 52 may be arranged not in the intake manifold 26 but in a pipe upstream of the intake manifold 26.

  The engine 100 includes an exhaust manifold 30, an exhaust pipe 31, and an exhaust gas purification device 32 as exhaust system members. Thus, the engine 100 provided with the exhaust gas purification device 32 is particularly referred to as an exhaust gas purification system. Note that the exhaust gas purification device 32 may be arranged at a position slightly away from the engine 100.

  The exhaust manifold 30 collectively supplies exhaust gas generated in the plurality of combustion chambers to the turbine housing 22 of the supercharger 21. In addition, an exhaust pressure sensor 53 and an exhaust temperature sensor 54 are attached to the exhaust manifold 30.

  The exhaust pressure sensor 53 detects the gas pressure in the exhaust manifold 30 and outputs it to the ECU 50. The ECU 50 recognizes the input pressure as the exhaust pressure. The exhaust temperature sensor 54 detects the temperature of the gas in the exhaust manifold 30 and outputs it to the ECU 50.

  A part of the gas that has passed through the exhaust manifold 30 and the turbine housing 22 is supplied to the EGR device 40 via the EGR pipe 41 and the rest is supplied to the exhaust gas purification device 32 via the exhaust pipe 31.

  The engine 100 also includes an EGR device 40 as an intake system and exhaust system member.

  The EGR device 40 includes an EGR cooler 42 and an EGR valve 43. The EGR cooler 42 cools the exhaust gas. The EGR device 40 can change the amount of exhaust gas supplied to the intake manifold 26 by adjusting the opening of the EGR valve 43. The opening degree of the EGR valve 43 is controlled by the ECU 50. The ECU 50 adjusts the opening degree of the EGR valve 43 based on, for example, a differential pressure between the intake pressure and the exhaust pressure.

  The exhaust gas purification device 32 purifies the exhaust gas and discharges it. The exhaust gas purification device 32 includes an oxidation catalyst 33 and a filter 34. The oxidation catalyst 33 is made of platinum or the like, and is a catalyst for oxidizing (combusting) unburned fuel, carbon monoxide, nitrogen monoxide and the like contained in the exhaust gas. The filter 34 is configured as a wall flow type filter, for example, and collects PM (particulate matter) contained in the exhaust gas treated by the oxidation catalyst 33.

  Further, an oxidation catalyst temperature sensor 55, a filter temperature sensor 56, and a differential pressure sensor 57 are attached to the exhaust gas purification device 32. The oxidation catalyst temperature sensor 55 detects the temperature in the vicinity of the inlet of the exhaust gas purification device 32 (the exhaust upstream side of the oxidation catalyst 33). The filter temperature sensor 56 detects the temperature between the oxidation catalyst 33 and the filter 34 (exhaust upstream side of the filter 34).

  The differential pressure sensor 57 detects a pressure difference between the upstream side of the filter 34 (the exhaust downstream side of the oxidation catalyst 33) and the downstream side of the filter 34, and outputs the pressure difference to the ECU 50. The ECU 50 calculates the PM accumulation amount accumulated on the filter 34 based on the detection result of the differential pressure sensor 57. As a method for calculating the PM deposition amount, in addition to using the differential pressure, the oxidation reaction occurring in the exhaust gas purification device 32 is calculated based on the operation history of the engine 100, and the PM deposition amount is obtained based on the oxidation reaction. You can also.

  Engine 100 also includes an atmospheric pressure sensor 58 (FIG. 2). The atmospheric pressure sensor 58 detects the atmospheric pressure and outputs it to the ECU 50.

  Next, control (hereinafter referred to as regeneration control) for removing PM accumulated on the filter 34 of the exhaust gas purification device 32 will be described with reference to FIG. In the present embodiment, at least four types of regeneration control can be performed: assist regeneration control, reset regeneration control, stationary regeneration control, and recovery regeneration control.

The assist regeneration control is performed at a timing when the PM accumulation amount becomes a predetermined value or more. The assist regeneration control is performed so that the inside of the exhaust gas purification device 32 is relatively low in temperature (about 300 to 400 degrees). At this temperature, NO ₂ is generated in the oxidation catalyst 33, and PM is oxidized and removed by this NO ₂ . In the assist regeneration control, the intake throttle 25 is used and after injection is performed, but post injection is not performed. The assist regeneration control is performed during work using the engine.

The reset regeneration control is performed every predetermined time (for example, several tens of hours to several hundred hours). The reset regeneration control is also performed when the PM accumulation amount remains a predetermined amount even after the assist regeneration control is performed for a predetermined time. The reset regeneration control is performed so that the inside of the exhaust gas purification device 32 becomes relatively high temperature (about 500 to 700 degrees). At this temperature, NO ₂ is not generated in the oxidation catalyst 33, and PM is oxidized and removed by O ₂ . In the reset regeneration control, the intake throttle 25 is used, and after injection and post injection are performed. The temperature can be increased by performing post injection. The reset regeneration control is performed during work using the engine.

  Stationary regeneration control is performed when the PM accumulation amount remains more than a predetermined amount even if reset regeneration control is performed for a certain period of time. Stationary regeneration control is performed at a relatively high temperature (about 500 to 700 degrees), similarly to the reset regeneration control. Also in the stationary regeneration control, the intake throttle 25 is used, and after injection and post injection are performed. The difference between the reset regeneration control and the stationary regeneration control is that the reset regeneration control is performed during work using the engine, whereas the stationary regeneration control is performed during non-work. Further, in the stationary regeneration control, the engine speed is maintained at a predetermined high speed. As a result, the stationary regeneration control can remove PM under better conditions than the reset regeneration control.

  The recovery regeneration control is performed when the PM accumulation amount remains more than a predetermined amount even if the stationary regeneration control is performed for a predetermined time. As shown in FIG. 4, the recovery regeneration control is the same as the stationary regeneration control in the items of regeneration type, control target, and work availability. The recovery reproduction control is composed of two stages of first recovery reproduction control and second recovery reproduction control.

  Hereinafter, a description will be given with reference to the flowchart of FIG. In the stationary regeneration control, regeneration control is performed in a high temperature environment by increasing the post injection amount (S11). The ECU 50 determines whether or not the PM accumulation amount is equal to or greater than M1 after a predetermined time (for example, about several tens of minutes) has elapsed since the start of the stationary regeneration control (S12).

  When the PM accumulation amount is equal to or greater than M1, the ECU 50 determines that PM is not sufficiently removed by the stationary regeneration control, and performs the recovery regeneration control. First, the ECU 50 performs recovery first regeneration control (S13). In the recovery first regeneration control, the temperature in the exhaust gas purification device 32 (more specifically, the temperature between the oxidation catalyst 33 and the filter 34) is performed at a lower temperature than the stationary regeneration control by suppressing the post-injection amount. It is performed for a longer time (several hours) than the reproduction control. Thus, the process that takes a long time at a relatively low temperature is a feature of the recovery regeneration control, whereby the second recovery regeneration control can be performed in a state where there is no risk of runaway combustion. The ECU 50 determines whether or not the PM accumulation amount is equal to or greater than M2 after a predetermined time (that is, about several hours) has elapsed after the start of the recovery first regeneration control (S14).

  When the PM accumulation amount is M2 or more, the ECU 50 determines that PM is not sufficiently removed by the first recovery regeneration control, and performs the second recovery regeneration control (S15). The second recovery regeneration control is a process equivalent to the stationary regeneration control. Therefore, the ECU 50 increases the temperature in the exhaust gas purification device 32 by increasing the post injection amount. By continuing this process for several tens of minutes, the second recovery regeneration control is completed, and PM is removed.

  Next, processing for increasing the temperature in the exhaust gas purification device 32 when shifting from the first recovery regeneration control to the second recovery regeneration control will be described with reference to the flowchart of FIG. 6 and various graphs of FIG. . The flowchart shown in FIG. 6 shows processing performed at the start of the recovery second regeneration control (S15) of the flowchart shown in FIG.

  When the ECU 50 shifts from the recovery first regeneration control to the recovery second regeneration control, the ECU 50 starts the open loop control of the post injection amount (S151). Since it is open loop control, post injection is performed at a predetermined injection amount regardless of the target temperature (see the display of open loop control in FIGS. 9B and 10B).

  The ECU 50 stores the temperature detected by the filter temperature sensor 56 (hereinafter, DOC outlet temperature). FIG. 7 shows a graph showing the time change of the DOC outlet temperature. The ECU 50 calculates the temperature increase rate of the DOC outlet temperature at a predetermined timing (S152). The timing for calculating the temperature increase rate is arbitrary, but it is preferable that the timing for switching from open loop control to feedback control is determined in accordance with the temperature increase rate. For example, it is preferable to calculate the temperature change rate before reaching a temperature intermediate between the temperature of the first recovery regeneration control and the temperature of the second recovery regeneration control. In addition, since it is empirically known that the temperature change becomes substantially linear when the post injection amount is changed by open loop control as in this embodiment, the temperature increase rate can be calculated at any timing. There is no big difference. The temperature increase rate varies depending on, for example, the deterioration degree of the oxidation catalyst 33.

  Next, the ECU 50 calculates a temperature for switching from the open loop control to the feedback control (hereinafter referred to as switching temperature) based on the calculated temperature increase rate (S153). The switching temperature is calculated based on a map or a table showing the correspondence between the switching temperature and the temperature increase rate. FIG. 8A shows a graph showing a correspondence relationship between the switching temperature and the temperature increase rate in the present embodiment.

  As shown in FIG. 8A, basically, the switching temperature is increased as the temperature increase rate increases. In addition, since it is necessary to make switching temperature below target temperature, the switching temperature has an upper limit. In FIG. 8A, the switching temperature and the temperature increase rate are in a proportional relationship, but may not be in a proportional relationship.

  Next, the ECU 50 determines whether or not the DOC outlet temperature is equal to or higher than the switching temperature (S154). And when it determines with DOC exit | outlet temperature being more than switching temperature, it switches from open loop control to feedback control (S155, control switching process). In the feedback control, the post injection amount is determined based on the target DOC outlet temperature and the current DOC outlet temperature. Therefore, for example, when the difference between the target temperature and the current temperature is large, the post injection amount increases.

  Next, with reference to the graph of FIG. 9, the temperature change and the post injection amount change in the present embodiment and the conventional example when the temperature increase rate is high will be described. Here, the conventional example is an example in which the switching temperature for switching from the open loop control to the feedback control is constant. When the rate of temperature increase is high, the switching temperature of the present embodiment is high, so that the conventional example is switched to feedback control prior to the present embodiment.

  In the conventional example, since the control is switched to the feedback control in a state where the temperature difference from the target temperature is large, the post-injection with a very large injection amount is performed in the feedback control (chain line in FIG. 9B). Thereby, since the DOC outlet temperature also rises rapidly, an overshoot that greatly exceeds the target temperature occurs (dashed line in FIG. 9A).

  On the other hand, in this embodiment, since the temperature increase rate is high, the switching temperature becomes high. Therefore, since the control is switched to the feedback control in a state where the temperature difference from the target temperature is relatively small, post injection is performed with a smaller injection amount than in the conventional example (solid line in FIG. 9B). Thereby, it is possible to prevent the DOC outlet temperature from rapidly increasing and prevent overshoot (solid line in FIG. 9A).

  Next, with reference to the graph of FIG. 10, the temperature change and post injection amount change of the present embodiment and the conventional example when the temperature increase rate is low will be described. When the rate of temperature increase is low, the switching temperature of the present embodiment is lowered, so that the present embodiment is switched to feedback control before the conventional example.

  When the temperature increase rate is low, the post injection amount determined by the open loop control takes much time because the DOC outlet temperature increases. In the conventional example, since the switching temperature is higher than that of the present embodiment, it takes a long time to perform the open loop control, and as a result, it takes a long time for the DOC outlet temperature to reach the target temperature (FIG. 10A and FIG. b) chain line).

  On the other hand, in this embodiment, since the switching temperature is lower than that of the conventional example, the time for performing the open loop control can be shortened. Therefore, feedback control can be performed early. As a result, the time until the DOC outlet temperature reaches the target temperature can be shortened as compared with the conventional example (solid lines in FIGS. 10A and 10B).

  Note that, by increasing the switching temperature in the conventional example, it is possible to prevent overshoot when the temperature increase rate is high, but the time until the target temperature is reached when the temperature increase rate is low is further delayed. Also, by lowering the switching temperature in the conventional example, the time to reach the target temperature when the temperature increase rate is low can be shortened, but overshoot when the temperature increase rate is high becomes significant. Thus, the method in the conventional example causes a trade-off.

  In this regard, by changing the switching temperature according to the temperature increase rate as in the present embodiment, both effects of suppressing overshoot and shortening the time to reach the target temperature can be realized.

  It is not impossible to raise the DOC temperature only by feedback control without performing open loop control. However, as it is generally said that stability and rapid response are in a trade-off relationship in feedback control, it is difficult to solve the problem of the present application simply by improving the accuracy of feedback control. Even if it is possible, complicated control such as changing the control coefficient in the middle is required.

  As described above, the exhaust gas purification system of the present embodiment includes the exhaust gas purification device 32, the filter temperature sensor 56, and the ECU 50. The exhaust gas purification device 32 is disposed in the exhaust path of the engine 100 including the injector 12 and includes an oxidation catalyst 33 and a filter 34. The filter temperature sensor 56 detects a DOC outlet temperature that is a temperature between the oxidation catalyst 33 and the filter temperature sensor 56. The ECU 50 performs regeneration control to incinerate PM accumulated in the exhaust gas purification device 32 by raising the DOC outlet temperature. When the ECU 50 performs regeneration control by increasing the DOC outlet temperature, the ECU 50 calculates the temperature increase rate based on the DOC outlet temperature, and performs control for increasing the DOC outlet temperature based on the temperature increase rate from the open loop control. A control switching process for switching to feedback control is performed.

  Accordingly, it is possible to prevent the occurrence of overshoot when the temperature increase rate is high with simple control and to quickly reach the target temperature even when the temperature increase rate is low.

  In the exhaust gas purification system of the present embodiment, the ECU 50 calculates the switching temperature based on the temperature increase rate, and switches from the open loop control to the feedback control when the DOC outlet temperature reaches the switching temperature. Further, the rate of temperature rise and the switching temperature are in a proportional relationship.

  Thus, by determining whether or not to switch control using temperature, it is possible to switch control at a more accurate timing than when using time, for example. In addition, since the temperature increase rate and the switching temperature are in a proportional relationship, an appropriate switching temperature can be calculated by a simple process.

  In the exhaust gas purification system of the present embodiment, the recovery regeneration control includes recovery first regeneration control and recovery second regeneration control that is performed at a higher temperature and for a shorter time than the recovery first regeneration control. The ECU 50 performs a control switching process when shifting from the recovery first regeneration control to the recovery second regeneration control.

  Thus, when the transition from the recovery first regeneration control to the recovery second regeneration control is performed, the temperature control is performed quickly and without overshooting, so that the effect of the control of the present invention can be exhibited more effectively. .

  The preferred embodiment of the present invention has been described above, but the above configuration can be modified as follows, for example.

  In the above-described embodiment, the example in which the control of the present invention is applied when the temperature rises during the transition from the recovery first regeneration control to the recovery second regeneration control has been described. However, the control of the present invention is applied when other temperature increases. You can also. For example, the control of the present invention can be applied at the start of reset regeneration or stationary regeneration.

  In the above embodiment, the temperature of the exhaust gas purification device 32 is raised by changing the injection amount of the post injection, but other processing (processing such as changing the injection amount of the after injection and the opening degree of the intake throttle 25) is performed. The temperature of the exhaust gas purifying device 32 may be increased by going.

  The correspondence relationship between the switching temperature and the temperature increase rate is not limited to the example described above, and can be changed as appropriate. For example, as shown in FIG. 8B, the switching temperature may be changed stepwise.

  In the above embodiment, the control is switched at the timing when the DOC outlet temperature becomes equal to or higher than the switching temperature. However, for example, time may be used instead of the DOC outlet temperature. That is, the ECU 50 calculates the switching time based on the temperature increase rate of the DOC outlet temperature, and switches from the open loop control to the feedback control at the timing when the switching time is reached.

  The configuration of the engine 100 and the processing performed by the ECU 50 can be changed as appropriate without departing from the spirit of the present invention. For example, the present invention can be applied to a naturally aspirated engine.

12 Injector (fuel injection device)
21 Supercharger 26 Intake manifold 30 Exhaust manifold 32 Exhaust gas purification device 33 Oxidation catalyst 34 Filter 50 ECU (control unit)
56 Filter temperature sensor 100 Engine

Claims (3)

An exhaust gas purification device including an oxidation catalyst and a filter disposed on an exhaust downstream side of the oxidation catalyst, disposed in an exhaust path of an engine including a fuel injection device;
A filter temperature sensor for detecting an oxidation catalyst outlet temperature which is a temperature between the oxidation catalyst and the filter;
A control unit that performs regeneration control to increase the outlet temperature of the oxidation catalyst and incinerate particulate matter accumulated in the exhaust gas purification device;
With
The playback control includes recovery playback control,
The recovery playback control includes recovery first playback control and recovery second playback control that is performed at a higher temperature and for a shorter time than the recovery first playback control,
When the control unit performs regeneration control by increasing the oxidation catalyst outlet temperature when shifting from the recovery first regeneration control to the recovery second regeneration control, the control unit sets the oxidation catalyst outlet temperature detected by the filter temperature sensor. calculating a temperature rise rate on the basis, according to the previous SL switching temperature or switching time is the oxidation catalyst outlet temperature to switch the feedback control of the control for increasing the oxidation catalyst outlet temperature from the open loop control the temperature increase rate Decide
The control unit calculates the temperature increase rate for determining the switching temperature or the switching time, and the oxidation catalyst outlet temperature includes a temperature of the first recovery regeneration control and a temperature of the second recovery regeneration control. And an exhaust gas purification system that is performed until the temperature reaches an intermediate temperature . The exhaust gas purification system according to claim 1,
The said control part delays the timing which switches from open loop control to feedback control, so that the said temperature increase rate is high, The exhaust gas purification system characterized by the above-mentioned. The exhaust gas purification system according to claim 2,
The control unit calculates a switching temperature that is a temperature for switching control based on the temperature increase rate, and when the oxidation catalyst outlet temperature reaches the switching temperature, the control unit switches from open loop control to feedback control,
The exhaust gas purification system, wherein the temperature increase rate and the switching temperature are in a proportional relationship.

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