JP4935640B2 - Engine deceleration control device - Google Patents

Description

  The present invention relates to an engine deceleration control device, and more particularly to an engine deceleration control device in which fuel cut is performed during deceleration, and belongs to the technical field of engine control during deceleration.

  In general, an exhaust purification device for purifying exhaust gas by, for example, oxidizing hydrocarbons or carbon monoxide contained in exhaust gas or reducing nitrogen oxides is disposed in the exhaust passage of an automobile engine. Has been. Since such an exhaust purification device uses a catalyst mainly composed of noble metals, in order for the exhaust purification device to become active, the exhaust purification device is warmed by the exhaust gas discharged from the engine, and the catalytic action It is necessary to raise the temperature to the activation temperature at which the gas starts.

  On the other hand, it is known to perform a fuel cut to stop fuel injection of the engine when the engine decelerates when the driver does not request acceleration and stops the depression of the accelerator pedal. At the time of this fuel cut, combustion does not occur in the engine, but the engine is rotating, so that relatively low temperature fresh air flows into the exhaust purification device as it is and the exhaust purification device is cooled. As a result, when the exhaust purification device is not yet in an active state, there is a problem that the time until the exhaust purification device becomes active becomes longer, or when the exhaust purification device is in an active state, There arises a problem that the exhaust purification device cools and becomes inactive.

  Therefore, in order to cope with such a problem, Patent Document 1 discloses an EGR passage for communicating an intake passage and an exhaust passage of an engine, and an EGR for adjusting a gas recirculation amount from the exhaust passage to the intake passage. In an engine equipped with a valve, a technique is disclosed in which when the fuel is cut, the EGR valve is fully opened and the intake control valve disposed in the intake passage is fully closed in order to adjust the intake air amount. ing.

  In this way, the amount of fresh air taken in is reduced and the amount of gas flowing into the exhaust purification device is reduced, so that the cooling of the exhaust purification device is delayed. In addition, since the amount of gas recirculation from the exhaust passage to the intake passage increases, the rate at which the gas passes through the engine body that is a heat source (although combustion does not occur) increases (while the gas flowing into the exhaust purification device) Even if the gas itself is delayed and the gas flows into the exhaust purification device, the degree of cooling of the exhaust purification device is reduced.

JP2007-16611 (paragraph 0024)

  However, at the time of deceleration, the exhaust pressure in the exhaust passage relatively decreases due to a decrease in the intake air amount and a decrease in the engine speed (due to the automatic shift up of the gear stage in the case of an automatic transmission). Therefore, even if the EGR valve is fully opened as in the above technique, the amount of gas recirculation from the exhaust passage to the intake passage does not increase so much (the amount of gas flowing into the exhaust purification device does not decrease so much), and as a result The ratio of the gas passing through the engine body, which is the heat source, does not increase so much, the cooling delay effect of the gas itself cannot be obtained so much, and the cooling effect of the exhaust purification device when the gas flows into the exhaust purification device is not so much It will not be obtained.

  The present invention addresses the above-described problems in an engine in which fuel cut is performed during engine deceleration, and the EGR valve is opened and the intake control valve is closed. It is an object to reliably increase the amount of gas recirculated from the exhaust passage to the intake passage even in a state where the exhaust pressure of the exhaust gas is relatively lowered, thereby avoiding cooling of the exhaust purification device.

  In order to solve the above problems, the present invention uses the following means.

That is, the invention according to claim 1 of the present application is provided in an EGR passage that communicates an intake passage and an exhaust passage of an engine, and an EGR valve for adjusting a gas recirculation amount from the exhaust passage to the intake passage. An intake control valve for adjusting the amount of intake air and an exhaust passage downstream of the connection portion with the EGR passage, and disposed in the intake passage upstream of the connection portion with the EGR passage. An exhaust gas purification device for purifying gas, a deceleration detection means for detecting a deceleration state of the engine, and a fuel supply stop means for stopping the fuel supply of the engine when the deceleration state of the engine is detected by the deceleration detection means; A deceleration control device for an engine having a deceleration control means for opening the EGR valve and closing the intake control valve when the fuel supply is stopped by the fuel supply stop means; When decelerating state of the engine is detected, with is provided with exhaust pressure raising means for raising the exhaust pressure at the connecting portion of at least the EGR passage in the exhaust passage, the exhaust pressure increasing means, and said EGR passage The opening control of the nozzle formed by the movable vane provided in the turbine section of the variable capacity turbocharger disposed in the exhaust passage downstream from the connecting section is controlled in the closing direction, and the deceleration control The means is characterized in that the opening when the EGR valve is opened is set to an opening at which the rate of increase of the gas recirculation amount with respect to the increase in the opening of the EGR valve starts to become smaller than a predetermined value .

  Here, “opening operation” for the EGR valve means that the opening degree of the EGR valve is set to an opening degree other than full closing, and preferably, it would have been set if the EGR valve was normally controlled. This means that the opening is larger than the opening. Similarly, “closed operation” for the intake control valve means that the opening of the intake control valve is set to an opening other than full open, and preferably set if the intake control valve was normally controlled. This means that the opening is smaller than the expected opening.

Next, the invention according to claim 2 of the present application is the engine deceleration control device according to claim 1, further comprising temperature detection means for detecting the temperature of the exhaust purification device, wherein the deceleration control means includes: Only when the temperature detected by the temperature detecting means is lower than a predetermined temperature, the EGR valve is opened and the intake control valve is closed.

Next, the invention according to claim 3 of the present application is the engine deceleration control device according to claim 1, further comprising temperature detection means for detecting the temperature of the exhaust purification device, wherein the deceleration control means includes: The opening degree when the intake control valve is closed is set according to the temperature detected by the temperature detecting means.

Next, an invention according to claim 4 of the present application is the engine deceleration control device according to claim 1, wherein the deceleration control means determines the opening degree of the intake control valve when the intake control valve is closed. The opening is set such that the intake pressure downstream of the control valve becomes a predetermined target pressure.

Next, the invention according to claim 5 of the present application is the engine deceleration control device according to claim 4 , further comprising temperature detection means for detecting the temperature of the exhaust purification device, wherein the deceleration control means includes: The target pressure is set according to the temperature detected by the temperature detecting means.

  First, according to the first aspect of the present invention, when the engine is decelerated (when the engine decelerating state is detected), fuel cut (stop of fuel supply of the engine) is performed and the EGR valve is opened. In an engine that closes the intake control valve, at the time of deceleration, the exhaust pressure in the exhaust passage is increased at least at the connection portion with the EGR passage. Even in the lowered state, the exhaust pressure rises at least at the connection portion between the exhaust passage and the EGR passage, and as a result, the amount of gas recirculation from the exhaust passage through the EGR passage to the intake passage reliably increases. It will be.

  As a result, the rate at which the gas passes through the engine body that is the heat source (although combustion does not occur) increases (while the rate of gas flowing into the exhaust purification device decreases), the cooling of the gas itself is delayed, Even when the gas flows into the exhaust purification device, the degree of cooling of the exhaust purification device is surely reduced. That is, cooling of the exhaust purification device is avoided.

In this case, according to the present invention, the exhaust pressure can be increased during deceleration using the turbine section of an existing variable capacity turbocharger. That is, it is not necessary to separately provide a dedicated device for achieving an increase in the exhaust pressure during deceleration in the exhaust passage.

Further, since the opening when the EGR valve is opened is set to an opening at which the rate of increase of the gas recirculation amount with respect to the increase in the opening of the EGR valve starts to become smaller than a predetermined value, It will take various opening positions, and the adverse effect of always fixing the EGR valve fully open (that is, if the driver next presses the accelerator pedal to request acceleration, the EGR valve will be closed) However, the problem that the problem of a decrease in the gas recirculation amount due to the delay in the closing operation of the EGR valve becomes significant) is reduced. That is, a significant decrease in acceleration response is suppressed. Moreover, since the exhaust pressure rises at least at the connection portion between the exhaust passage and the EGR passage, the amount of gas recirculation from the exhaust passage to the intake passage through the EGR passage is considerable even if the EGR valve is not fully opened. Therefore, the cooling delay effect of the gas itself is sufficiently obtained.

Note that the turbine section of the variable capacity supercharger may be disposed either upstream or downstream of the exhaust purification device.

Next, according to the second aspect of the invention, the EGR valve is opened and the intake control valve is closed only when the temperature of the exhaust purification device is lower than the predetermined temperature. The adverse effect of forcibly opening the valve (ie, the problem that the gas recirculation amount decreases with the delay in closing the EGR valve during the next acceleration ) is reduced, and the intake control valve is forced. Adverse effects of controlling in the closing direction (i.e., if the driver next presses the accelerator pedal to request acceleration, the intake control valve will be opened) The problem of a delay in the increase in the amount of fresh air that accompanies the delay in opening the valve) will be reduced. That is, a decrease in acceleration response is suppressed.

  Here, the predetermined temperature is, for example, an activation temperature of the exhaust purification device or a temperature higher than that. Then, when the exhaust purification device is sufficiently active, the EGR valve and the intake control valve are normally controlled. However, since the exhaust purification device is sufficiently active, the Even if the gas flows into the exhaust purification device as it is, it is unlikely that the exhaust purification device will be cooled until it becomes inactive.

  The temperature of the exhaust purification device can be detected in association with, for example, the temperature of engine cooling water, the temperature of exhaust gas immediately before flowing into the exhaust purification device or immediately after flowing out of the exhaust purification device, and the like. In other words, the temperature detection means includes not only a device that directly detects the temperature of the exhaust gas purification device but also a device that detects other related temperatures as described above.

Next, according to the invention described in claim 3 , since the opening when the intake control valve is closed is set according to the temperature of the exhaust purification device, the intake control valve can be opened in various ways. Therefore, the adverse effect of always fixing the intake control valve to the fully closed state (that is, the problem that the delay in increasing the fresh air amount at the next acceleration becomes significant) is reduced. That is, a significant decrease in acceleration response is suppressed.

  For example, if the opening degree of the intake control valve is increased as the temperature of the exhaust purification device is higher, the problem of cooling of the exhaust purification device and the problem of lowering acceleration response will be solved in a balanced manner.

Next, according to the invention of claim 4 , the opening when the intake control valve is closed is set to an opening at which the intake pressure downstream of the intake control valve becomes a predetermined target pressure. As a result, the intake control valve takes various openings, and the adverse effect of always fixing the intake control valve to the fully closed state (that is, the problem of the delay in the increase of the new air amount at the next acceleration is remarkable). Will be reduced). That is, a significant decrease in acceleration response is suppressed.

  Here, the target pressure is, for example, atmospheric pressure (1 atmospheric pressure = 101.325 kPa). If it does so, the problem of cooling of an exhaust gas purification device and the problem of decline in acceleration response will be solved with good balance.

Next, according to the invention described in claim 5 , since the target pressure is set according to the temperature of the exhaust purification device, for example, the higher the temperature of the exhaust purification device, the higher the target pressure. In the end, the higher the temperature of the exhaust purification device, the larger the opening of the intake control valve. This also solves the problem of cooling of the exhaust purification device and the problem of reduced acceleration response in a well-balanced manner. The Rukoto.

Hereinafter, the present invention will be described in more detail through the best mode for carrying out the invention.

  FIG. 1 is an overall configuration diagram including a control system of a deceleration control device 10 for an engine 1 according to the best embodiment of the present invention. The diesel engine 1 has an intake passage 2 and an exhaust passage 3. An intake valve 4 is provided at an intake port that is a terminal portion of the intake passage 2, and an exhaust valve 5 is provided at an exhaust port that is a start end portion of the exhaust passage 3. A fuel injection valve 6 that directly injects fuel into the combustion chamber and a piston 7 that moves up and down in the cylinder bore are provided for each cylinder. The diesel engine 1 further includes an EGR passage 8 that communicates the intake passage 2 and the exhaust passage 3.

  In the intake passage 2, from the upstream side, the blower portion 12 of the supercharger 11, an intercooler 14 that cools the intake air that has been compressed and heated by the blower portion 12, and intake control for adjusting the intake air amount Valves 15 are arranged in this order.

  From the upstream side, the exhaust passage 3 is provided with an oxidation catalyst (DOC) for purifying the exhaust gas by oxidizing (burning) hydrocarbons and carbon monoxide contained in the turbine section 13 of the supercharger 11 and the exhaust gas from the upstream side. An exhaust purification device) 16 and a particulate filter (DPF) 17 for collecting exhaust particulates such as soot contained in the exhaust gas are arranged in this order.

  In the EGR passage 8, an EGR cooler 18 that cools the gas recirculated from the exhaust passage 3 to the intake passage 2 from the exhaust passage 3 side, and a gas recirculation amount from the exhaust passage 3 to the intake passage 2 are adjusted. EGR valves 19 are arranged in this order.

  In that case, the intake control valve 15 is disposed upstream of the connection portion between the intake passage 2 and the EGR passage 8. Further, the oxidation catalyst 16 is disposed downstream of the connection portion between the exhaust passage 3 and the EGR passage 8.

  The control unit 30 of the engine 1 includes a signal from a water temperature sensor (temperature detecting means) 31 that detects the temperature of the cooling water of the engine 1, a signal from the engine speed sensor 32 that detects the speed of the engine 1, an oxidation catalyst A signal from an exhaust gas temperature sensor (temperature detection means) 33 that detects the temperature of the exhaust gas immediately after flowing out from the engine 16, and an accelerator opening sensor that detects the amount of depression of the accelerator pedal 20 that is depressed by the driver ( A signal from the deceleration detecting means) 34 is input.

  The control unit 30 is movable in the fuel injection valve 6, the intake control valve 15, the EGR valve 19, and the turbine unit 13 of the supercharger 11 according to the operating state of the engine 1 indicated by the various signals. A control signal is input to the vane 13b or the like.

  FIG. 2 is an enlarged sectional view showing the configuration of the turbine section 13 of the supercharger 11. In the present embodiment, the supercharger 11 is a known variable whose supercharging efficiency can be controlled by adjusting the opening of a nozzle formed by movable vanes 13b... 13b provided in the turbine section 13. It is a capacity type supercharger (VGT).

  That is, the turbine section 13 of the VGT 11 disposed in the exhaust passage 3 is provided with turbine blades 13a that are rotated by the pressure of exhaust gas flowing in the direction of the arrow in the figure, and a plurality of turbine blades 13a are provided around the turbine blades 13a. Movable vanes 13b... 13b are provided, and a nozzle 13d for ejecting exhaust gas toward the turbine blade 13a is formed between the adjacent vanes 13b and 13b.

  Each of the movable vanes 13b... 13b can be rotated around a shaft 13c... 13c, and the opening degree of the nozzles 13d.

  For example, as shown by a solid line in FIG. 2, if the adjacent vanes 13b and 13b are rotated so as to be close to each other, the opening degree of the nozzle 13d is closed small. That is, the opening degree of the nozzle 13d is controlled in the closing direction. In particular, if the opening of the nozzle 13d is reduced when the rotational speed of the engine 1 is small, the flow velocity of the exhaust gas ejected toward the turbine blade 13a increases, and the flow is directed in the tangential direction of the turbine blade 13a. Supercharging efficiency will increase. In exchange for this, in the exhaust passage 3, the exhaust pressure rises in a range from the exhaust port provided with the exhaust valve 5 to the turbine section 13.

  In this case, the turbine portion 13 is disposed downstream of the connection portion between the exhaust passage 3 and the EGR passage 8 (note that the turbine portion 13 is disposed upstream of the oxidation catalyst 16). Therefore, when the opening degree of the nozzle 13d is reduced, the exhaust pressure at the connection portion between at least the EGR passage 8 in the exhaust passage 3 increases.

  On the other hand, as shown by a chain line in FIG. 2, if the adjacent vanes 13b and 13b are turned away from each other, the opening of the nozzle 13d is greatly opened. That is, the opening degree of the nozzle 13d is controlled in the opening direction. In particular, if the opening degree of the nozzle 13d is increased when the engine 1 is rotating at a high speed, the flow rate of the exhaust gas ejected toward the turbine blade 13a is increased, so that the supercharging efficiency is increased.

  The control unit 30 controls the opening degree of the nozzles 13d... 13d formed by these movable vanes 13b... 13b from fully closed (solid line state) to fully open (chain line state) (see FIG. 4). : Described later).

  FIG. 3 is a flowchart showing an example of a specific control operation performed by the control unit 30 of the exhaust purification device 10.

  First, in step S1, various signals are read, and in step S2, it is determined whether the oxidation catalyst 16 is in an active state. For this determination, a signal from the water temperature sensor 31 or a signal from the exhaust gas temperature sensor 33 is used. For example, the temperature of the cooling water of the engine 1 is 70 ° C. or higher, or the exhaust gas immediately after flowing out of the oxidation catalyst 16. If temperature is 200 degreeC or more, it will determine with the oxidation catalyst 16 being an active state.

  As a result, when the oxidation catalyst 16 is in the active state, normal control is performed on the intake control valve 15, the EGR valve 19, and the movable vane 13b of the VGT 11 in steps S3 to S5, and the process returns.

  Here, as illustrated in FIG. 4, for the movable vane 13 b of the VGT 11, as the engine speed increases and the engine load (represented by the intake air amount or the fuel injection amount) increases, The opening degree (specifically, the opening degree of the nozzle 13d) is controlled to be large (the fully open state is fully open and the maximum closed state is fully closed). The effect obtained by this is as described above.

  On the other hand, when the oxidation catalyst 16 is not in the active state in step S2, it is determined in step S6 whether or not the accelerator opening (depressed amount of the accelerator pedal 20) detected by the accelerator opening sensor 34 is fully closed (zero). To do.

  As a result, when the accelerator opening is not fully closed, that is, when the engine 1 is not decelerated, normal control is performed on the intake control valve 15, the EGR valve 19, and the movable vane 13b of the VGT 11 in steps S3 to S5. Execute and return.

  On the other hand, when the accelerator opening is fully closed, that is, when the engine 1 is in a deceleration state, the fuel injection valve 6 is controlled to stop the fuel injection of the engine 1 in step S7. That is, the fuel is cut (fuel supply stop means).

  Next, in steps S8 to S10, control during deceleration is executed on the intake control valve 15, the EGR valve 19, and the movable vane 13b of the VGT 11, respectively, and the process returns.

  Specifically, in step S8, first, the target intake pressure is set according to the engine speed and the exhaust gas temperature. Here, as illustrated in FIG. 5, the target intake pressure is set so as to increase as the engine speed increases and as the exhaust gas temperature increases.

  Alternatively, the target intake pressure may be fixed to, for example, atmospheric pressure (1 atmosphere = 101.325 kPa) (the operation in this case is displayed in step S8 in FIG. 3).

  Then, the opening degree of the intake control valve 15 is set to an opening degree (β is set to, for example, 30%) at which the intake pressure downstream of the intake control valve 15 is set to a target intake pressure (or fixed atmospheric pressure), Such a control signal is output to the intake control valve 15 (closing operation: deceleration control means).

  In step S9, the opening degree of the EGR valve 19 is set to an opening degree at which the increasing rate of the gas recirculation amount with respect to the increase in the opening degree of the EGR valve 19 starts to become smaller than a predetermined value. Output a control signal.

  For example, as illustrated in FIG. 6, in the engine 1 according to this embodiment, the gas recirculation amount increases linearly as the opening degree of the EGR valve 19 increases from zero (fully closed). When the opening degree of the EGR valve 19 exceeds α (for example, 50%), the increasing rate of the gas recirculation amount starts to decrease, and thereafter, the gas recirculation amount does not increase so much even if the opening degree of the EGR valve 19 is increased.

  Therefore, in the present embodiment, in step S9, the opening degree of the EGR valve 19 is fixed to α, and such a control signal is output to the EGR valve 19 (opening operation: deceleration control means).

  In step S10, the opening degree of the movable vane 13b of the VGT 11 is fixed to the maximum closed state (fully closed: the solid line state in FIG. 2), and such a control signal is output to the movable vane 13b (closing operation: Exhaust pressure increasing means).

  The effect obtained by the control operation as described above will be described with reference to the time chart of FIG.

  When the driver stops the depression of the accelerator pedal 20 and starts deceleration (YES in step S6), the control shifts from normal control (steps S3 to S5) to deceleration control (steps S8 to S10).

  As a result, the opening degree of the intake control valve 15 is controlled (closed operation) to β, which is not fully closed, as indicated by the symbol a. Further, the opening degree of the EGR valve 19 is controlled (opening operation) to α which is not fully opened, as indicated by a symbol a. Further, the opening degree of the vane 13b of the VGT 11 is fixed to the fully closed position (closed operation), as indicated by the symbol C.

  From this state, when the driver next resumes depression of the accelerator pedal 20 and acceleration starts (NO in step S6), the control shifts from deceleration control (steps S8 to S10) to normal control (steps S3 to S5). .

  As a result, the opening degree of the intake control valve 15 is increased in order to increase the fresh air amount. Further, the opening degree of the EGR valve 19 is reduced in order to reduce the gas recirculation amount. Furthermore, the opening degree of the vane 13b of the VGT 11 is increased in order to increase the supercharging efficiency (see FIG. 4).

  At this time, since the opening degree of the intake control valve 15 is not fully closed at the time of deceleration, the problem of an increase in the fresh air amount accompanying a delay in the opening operation of the intake control valve 15 is reduced. Further, since the opening degree of the EGR valve 19 is not fully opened, the problem of the delay in reducing the gas recirculation amount accompanying the delay in the closing operation of the EGR valve 19 is reduced.

  Thus, in the deceleration control device 10 for the engine 1 according to the present embodiment, when the engine 1 is decelerated (when the deceleration state of the engine 1 is detected) (YES in step S6), the fuel is cut (the fuel of the engine 1). The supply is stopped) (step S7), the EGR valve 19 is opened (step S9), and the intake control valve 15 is closed (step S8).

  Moreover, at the time of deceleration, the exhaust pressure in the exhaust passage 3 is increased at least at the connection portion with the EGR passage 8 (step S10), so that the exhaust pressure in the exhaust passage 3 relatively decreases during deceleration. Even in this state, the exhaust pressure rises at least at the connection portion between the exhaust passage 3 and the EGR passage 8, and as a result, the amount of gas recirculation from the exhaust passage 3 to the intake passage 2 through the EGR passage 8 is ensured. Will increase.

  As a result, the rate at which the gas passes through the main body of the engine 1 that is a heat source (although combustion does not occur) increases (while the rate of the gas flowing into the oxidation catalyst 16 decreases), the cooling of the gas itself is delayed. Even when the gas flows into the oxidation catalyst 16, the degree of cooling of the oxidation catalyst 16 is reliably reduced. That is, cooling of the oxidation catalyst 16 is avoided.

  Also, since the exhaust pressure is increased during deceleration using the turbine section 13 of the VGT 11 (see FIG. 2), a dedicated device for achieving the increase of the exhaust pressure during deceleration is provided. There is no need to newly install the exhaust passage 3.

  Further, only when the temperature of the oxidation catalyst 16 is lower than a predetermined temperature (70 ° C. in the case of the water temperature sensor 31 or 200 ° C. in the case of the exhaust gas temperature sensor 33) (NO in step S2), the EGR valve 19 is opened. Since the operation (step S9) and the intake control valve 15 are closed (step S8), the adverse effect of forcibly opening the EGR valve 19 (that is, the driver next requests acceleration) Then, when the accelerator pedal 20 is depressed, the EGR valve 19 is controlled in the closing direction, but the problem that the gas recirculation amount decreases with the delay in the closing operation of the EGR valve 19 is reduced. Further, the adverse effect of forcibly closing the intake control valve 15 (that is, if the driver next depresses the accelerator pedal 20 to request acceleration), the intake control valve 1 Although it will be controlled in the opening direction, and a problem that fresh air amount increasing delays associated with opening operation delay of the intake control valve 15 occurs) is reduced. That is, a decrease in acceleration response is suppressed.

  Moreover, since it is determined in step S2 whether or not the oxidation catalyst 16 is in an active state, when the oxidation catalyst 16 is sufficiently active (YES in step S2), the EGR valve 19 and the intake control valve 15 are Although normally controlled (steps S3 and S4), since the oxidation catalyst 16 is sufficiently active, the oxidation catalyst 16 remains active even if relatively low temperature fresh air flows into the oxidation catalyst 16 as it is. It is unlikely that it will cool down.

  Further, the opening when the intake control valve 15 is closed during deceleration is set to the opening β at which the intake pressure downstream of the intake control valve 15 becomes a predetermined target pressure (step S8). Since the control valve 15 takes various opening degrees, there is an adverse effect of always fixing the intake control valve 15 to be fully closed (that is, the problem of a delay in the increase in the fresh air amount at the next acceleration becomes significant). Will decrease. That is, a significant decrease in acceleration response is suppressed.

  In that case, when the target pressure is fixed at atmospheric pressure (1 atm = 101.325 kPa), the problem of cooling of the oxidation catalyst 16 and the problem of deterioration of acceleration response are solved in a well-balanced manner. It becomes.

  Further, since the target pressure is set according to the temperature of the oxidation catalyst 16 (see FIG. 5), for example, if the target pressure is increased as the temperature of the oxidation catalyst 16 is higher, the oxidation catalyst 16 is eventually obtained. The higher the temperature is, the larger the opening degree of the intake control valve 15 is. In this case as well, the problem of cooling the oxidation catalyst 16 and the problem of reduced acceleration response are solved in a well-balanced manner.

  Further, the opening when the EGR valve 19 is opened during deceleration is set to an opening α at which the rate of increase of the gas recirculation amount with respect to the increase in the opening of the EGR valve 19 starts to become smaller than a predetermined value. From (step 9), the EGR valve 19 takes various opening degrees, and the adverse effect of always fixing the EGR valve 19 to the fully open state (that is, the problem of the delay in reducing the gas recirculation amount at the next acceleration becomes significant). Problem) will be reduced. That is, a significant decrease in acceleration response is suppressed.

  Moreover, since the opening degree of the movable vane 13b of the VGT 11 is fully closed during deceleration (step S10), the exhaust pressure increases at least at the connection portion between the exhaust passage 3 and the EGR passage 8, and the EGR valve 19 is fully opened. Even if not, the amount of gas recirculation from the exhaust passage 3 to the intake passage 2 via the EGR passage 8 has increased considerably, so that the cooling delay effect of the gas itself can be sufficiently obtained.

  The above embodiment is the best embodiment of the present invention, but it goes without saying that various modifications and changes may be made without departing from the scope of the claims.

  For example, in step S8, the opening when the intake control valve 15 is closed is set to an opening at which the intake pressure downstream of the intake control valve 15 becomes a predetermined target pressure. Instead, as illustrated in FIG. 8, the opening when the intake control valve 15 is closed may be set according to the temperature of the oxidation catalyst 16.

  Even in this case, the intake control valve 15 takes various opening degrees, and the adverse effect of always fixing the intake control valve 15 to the fully closed state (that is, the problem of the delay in the increase in fresh air amount at the next acceleration) Will be reduced). That is, a significant decrease in acceleration response is suppressed.

  As shown in the figure, if the opening degree of the intake control valve 15 is increased as the temperature of the oxidation catalyst 16 increases, the problem of cooling of the oxidation catalyst 16 and the problem of deterioration of acceleration response are solved in a well-balanced manner. The Rukoto.

Further, the turbine section 13 of the VGT 11 may be disposed either upstream or downstream of the oxidation catalyst 16.

  As described above in detail with reference to specific examples, the present invention is an engine that performs fuel cut when the engine is decelerated, opens the EGR valve, and closes the intake control valve. This is a technique that can reliably increase the amount of gas recirculated from the exhaust passage to the intake passage even in a state where the exhaust pressure in the passage is relatively lowered, thereby avoiding cooling of the exhaust purification device. In the technical field of engine deceleration control devices, particularly engine deceleration control devices in which fuel cut is performed during deceleration, wide industrial applicability is expected.

1 is an overall configuration diagram including a control system of an engine deceleration control device according to the best embodiment of the present invention. It is sectional drawing which expands and shows the structure of the turbine part of the variable capacity | capacitance supercharger (VGT) contained in the said deceleration control apparatus. It is a flowchart which shows one example of control operation of the said deceleration control apparatus. It is a conceptual diagram which shows the characteristic of control of the movable vane of VGT used by the said control action. It is a conceptual diagram which shows the setting characteristic of the target intake pressure used by the said control action. It is a conceptual diagram which shows the relationship between the opening degree of the EGR valve contained in the said deceleration control apparatus, and a gas recirculation amount. It is a time chart which shows the effect | action obtained by the said control action. It is a conceptual diagram which shows the setting characteristic of the opening degree of the intake control valve used by control operation of 2nd Embodiment.

Explanation of symbols

1 Diesel Engine 2 Intake Passage 3 Exhaust Passage 6 Fuel Injection Valve 8 EGR Passage 10 Deceleration Control Device 11 Variable Capacity Supercharger (VGT)
13 Turbine part 13b Movable vane 13d Nozzle 15 Intake control valve 16 Oxidation catalyst (DOC: exhaust purification device)
17 Particulate filter (DPF)
19 EGR valve 30 control unit (fuel supply stop means, deceleration control means, exhaust pressure raising means)
31 Water temperature sensor (temperature detection means)
33 Exhaust gas temperature sensor (temperature detection means)
34 Accelerator opening sensor (deceleration detection means)

Claims (5)

An EGR valve disposed in an EGR passage that communicates an intake passage and an exhaust passage of the engine, and for adjusting a gas recirculation amount from the exhaust passage to the intake passage;
An intake control valve disposed in an intake passage upstream of a connection portion with the EGR passage, and for adjusting an intake air amount;
An exhaust purification device for purifying exhaust gas, disposed in the exhaust passage downstream from the connection with the EGR passage;
Deceleration detection means for detecting the deceleration state of the engine;
A fuel supply stopping means for stopping the fuel supply of the engine when the deceleration detecting means detects a deceleration state of the engine;
A deceleration control device for an engine having a deceleration control means for opening the EGR valve and closing the intake control valve when the fuel supply is stopped by the fuel supply stop means;
Exhaust pressure increasing means is provided for increasing the exhaust pressure at least in the connection portion with the EGR passage in the exhaust passage when the deceleration state of the engine is detected by the deceleration detecting means .
The exhaust pressure increasing means closes the opening degree of the nozzle formed by the movable vane provided in the turbine section of the variable capacity supercharger disposed in the exhaust passage downstream of the connection portion with the EGR passage. And control
The deceleration control means sets the opening when the EGR valve is opened to an opening at which the increasing rate of the gas recirculation amount with respect to the increase in the opening of the EGR valve starts to become smaller than a predetermined value. The engine deceleration control device. The engine deceleration control device according to claim 1,
Temperature detection means for detecting the temperature of the exhaust purification device is provided;
The engine deceleration control is characterized in that the deceleration control means opens the EGR valve and closes the intake control valve only when the temperature detected by the temperature detection means is lower than a predetermined temperature. apparatus. The engine deceleration control device according to claim 1,
Temperature detection means for detecting the temperature of the exhaust purification device is provided;
The engine deceleration control device according to claim 1, wherein the deceleration control means sets an opening degree of the intake control valve when the intake control valve is closed according to the temperature detected by the temperature detection means . The engine deceleration control device according to claim 1,
The deceleration control means sets the opening when the intake control valve is closed to an opening at which the intake pressure downstream of the intake control valve becomes a predetermined target pressure. . The engine deceleration control device according to claim 4 ,
Temperature detection means for detecting the temperature of the exhaust purification device is provided;
The engine deceleration control device, wherein the deceleration control means sets the target pressure in accordance with the temperature detected by the temperature detection means .

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