JP6759557B2 - Engine control - Google Patents

Description

The present invention relates to an engine control device including a supercharger, and more particularly to an engine control device that suppresses the generation of smoke during acceleration.

In an engine equipped with a supercharger, when the driver depresses the accelerator to accelerate, the increase in the intake pipe pressure, which is the pressure of the intake air introduced into the combustion chamber, is slightly delayed with respect to the depressing of the accelerator. There is a tendency. Injecting a large amount of fuel to meet the acceleration requirement when the intake pipe pressure is not rising may increase the smoke in the exhaust.

Therefore, for example, Patent Document 1 discloses a technique for suppressing smoke in the exhaust gas by executing so-called "smoothing" control when the accelerator is depressed and the engine shifts to the acceleration state. ing.

The smoothing control prevents the generation of smoke due to excessive fuel by gradually increasing the fuel injection amount over time without increasing the fuel injection amount at once even when the driver suddenly depresses the accelerator.

In addition, when the driver depresses the accelerator to accelerate, a smoke limit injection amount lower than the target fuel injection amount corresponding to the depressing amount of the accelerator is set to limit the amount of fuel actually injected. Therefore, there is also a technology to suppress smoke.

Japanese Unexamined Patent Publication No. 2001-159356

In the technique of Patent Document 1, the fuel injection amount is continuously increased by smoothing control immediately after the accelerator is depressed, which is a request for acceleration. For this reason, for example, in an operating situation in which the increase in the intake pipe pressure is significantly delayed with respect to the depression of the accelerator, the amount of fuel is increased immediately after the depression of the accelerator, which may cause a temporary excess fuel state. .. Therefore, it is assumed that the technique of Patent Document 1 cannot suppress smoke depending on the driving situation.

In addition, in the conventional technology of setting a smoke limit injection amount lower than the target fuel injection amount corresponding to the accelerator depression amount when acceleration is requested, the amount of fuel actually injected is immediately after the accelerator is depressed and when acceleration is completed. It is continuously set to be less than the target fuel injection amount. Therefore, the actual fuel injection amount is small with respect to the target torque corresponding to the acceleration request, which may cause acceleration failure.

Therefore, an object of the present invention is to more reliably suppress the generation of smoke at the time of requesting acceleration without sacrificing torque.

In order to solve the above problems, the present invention presents a supercharger that increases the pressure of the intake air introduced into the combustion chamber, a fuel injection valve that injects fuel into the intake air, and a fuel injection timing by the fuel injection valve. The fuel injection control means for controlling the injection amount and the delay amount for delaying the increase in the fuel injection amount corresponding to the acceleration request with respect to the acceleration request are determined, and the fuel is injected into the fuel injection control means based on the delay amount. The delay amount determining means includes a delay amount determining means for issuing a timing command, and the delay amount determining means is after the delay amount performed at the start timing of the acceleration request and the delay amount performed at the start timing of the acceleration request have elapsed. The delay amount performed during the acceleration according to the acceleration request is determined, and the delay amount performed at the start time of the acceleration request is set smaller as the engine speed increases and corresponds to the acceleration request. The larger the required torque is, the smaller the delay amount is set, and the larger the engine speed is, the smaller the delay amount is set, and the target intake pressure corresponding to the acceleration request and the actual intake pressure are set. The engine control device, which is set larger as the difference is larger, is adopted.

The present invention provides a delay amount determining means for determining a delay amount for delaying an increase in the injection amount of fuel corresponding to the acceleration request and issuing a command for a fuel injection timing based on the delay amount. Therefore, it is possible to more reliably suppress the generation of smoke without sacrificing torque when acceleration is required.

It is a schematic diagram which shows the structure of the engine of one Embodiment of this invention. (A) to (d) are graphs showing the control of the present invention. It is a flowchart which shows the control of this invention. (A) and (b) are graphs showing the control of the present invention.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall view showing the configuration of the engine E of the present invention and the control device of the engine E. Although the engine E of this embodiment is a diesel engine, the present invention can also be applied to a gasoline engine.

The configuration of the engine E includes an intake passage 1 for sending intake air into the combustion chamber 12 of the cylinder accommodating the piston 11, an exhaust passage 2 drawn out from the combustion chamber 12, a fuel injection valve (injector) 13 facing the combustion chamber 12, and the like. It has. The intake port, which is an opening of the intake passage 1 to the combustion chamber 12, and the exhaust port, which is an opening of the exhaust passage 2 to the combustion chamber 12, are opened and closed by valves, respectively.

In the intake passage 1, an air flow sensor 14 that detects the amount of intake air introduced into the combustion chamber 12, a throttle valve 25 that adjusts the flow path area of the intake passage 1, and an intake passage 1 flow from the intake port toward the upstream side. An intake air cooling device (intercooler) 6 for cooling the intake air, an intake pipe pressure detecting means 18 for detecting the intake air pressure in the intake air passage 1, a turbocharger compressor 17, and a throttle valve 22 for adjusting the flow path area of the intake air passage 1. , A case containing an air cleaner is provided. Inside the case of the air cleaner, a temperature sensor capable of detecting the intake air temperature in the pipe is provided as an atmospheric temperature detecting device 19.

In the exhaust passage 2, from the exhaust port to the downstream side, a turbocharger turbine 7, an exhaust purification unit 8 equipped with a catalyst for removing nitrogen oxides (NOx) in the exhaust, and the amount of smoke in the exhaust. A smoke sensor 16 and a muffler 9 for detecting the above are provided.

In the supercharger T, the rotation of the turbine 7 provided in the exhaust passage 2 is transmitted to the compressor 17 provided in the intake passage 1, and the rotation of the compressor 17 introduces the intake air into the combustion chamber 12. The pressure is increasing. The turbocharger T is a variable-capacity turbocharger that adjusts the flow velocity of exhaust gas in the turbine 7 by providing a movable vane 15 in the turbine 7 that drives the compressor 17. By adjusting the direction of the movable vane 15 according to the rotation speed of the engine, the flow velocity of the exhaust gas in the turbine 7 can be increased or decreased, and the optimum turbine capacity can be set according to the rotation speed of the engine.

Further, the turbine 7 and the exhaust port of the exhaust passage 2 and the intake port of the intake passage 1 and the throttle valve 25 are communicated with each other by the high pressure exhaust recirculation passage 23 constituting the high pressure exhaust gas recirculation device. .. A part of the exhaust gas discharged from the combustion chamber 12 is returned to the intake passage 1 as a return gas through the high-pressure exhaust return passage 23. The recirculated gas joins the intake air in the intake passage 1 according to the pressure state in the intake passage 1 accompanying the opening and closing of the high pressure exhaust recirculation valve 24 provided in the high pressure exhaust recirculation passage 23 and the opening and closing of the throttle valve 25.

Further, a low-pressure exhaust recirculation passage 20 constituting a low-pressure exhaust gas recirculation device communicates between the exhaust purification unit 8 of the exhaust passage 2 and the silencer 9 and between the compressor 17 and the throttle valve 22 of the intake passage 1. are doing. The low-pressure exhaust return passage 20 is provided with a return gas cooler 10 for cooling the return gas. A part of the exhaust gas discharged from the combustion chamber 12 through the low-pressure exhaust / return passage 20 returns to the upstream side of the intercooler 6 of the intake passage 1 as a return gas. The recirculated gas joins the intake air in the intake passage 1 according to the pressure state in the intake passage 1 accompanying the opening and closing of the low pressure exhaust recirculation valve 21 provided in the low pressure exhaust recirculation passage 20 and the opening and closing of the throttle valve 22.

The electronic control unit (Electronic Control Unit) 30 included in the vehicle equipped with the engine E controls the supply of fuel and air to the engine E, the opening and closing of the valve, the supercharger T, and the like.

Further, the fuel injection timing and the injection amount are controlled by the fuel injection valve 13 by the fuel injection control means 31 provided in the electronic control unit 30.

The electronic control unit 30 determines a delay amount for delaying the depression of the accelerator by the driver, that is, an increase in the injection amount of fuel corresponding to the acceleration request, and fuel injection based on the delay amount. The control means 31 is provided with a delay amount determining means 32 that issues a command for fuel injection timing.

The delay amount determination means 32 determines the delay amount, and the fuel injection control means 31 is instructed to inject fuel to the fuel injection control means 31 based on the delay amount, respectively, at the start time of the acceleration request and during the acceleration according to the acceleration request. ..

The delay amount means the time for delaying the increase in the injection amount of the fuel corresponding to the acceleration request with respect to the acceleration request. When the accelerator opening is increased by the driver's accelerator operation, that is, when the delay amount is set when an acceleration request is made, the fuel injection amount is increased until the time corresponding to the delay amount elapses. If it does not start, or if the fuel injection amount is being increased, the increase is suspended, and the fuel injection amount is not increased until the time corresponding to the delay amount has elapsed.

The execution of the delay is a control that delays the start time of the fuel injection increase based on the set delay amount, or suspends the fuel injection increase and restarts the increase after the time corresponding to the delay amount elapses. It is control.

The amount of delay is determined by the engine speed and the required torque corresponding to the acceleration requirement. For example, the delay amount can be calculated using a map in which the delay amount is determined according to the engine speed and the required torque. Alternatively, the delay amount may be determined by calculation each time according to the engine speed and the required torque. In particular, it is desirable that the delay amount determined at the start time of the acceleration request is determined by the above-mentioned determination method using the engine speed and the required torque.

Further, the delay amount may be determined by the difference between the engine speed and the target intake pressure corresponding to the acceleration request and the actual intake pressure. For example, the delay amount can be calculated using a map in which the delay amount is determined according to the difference between the engine speed and the target intake pressure and the actual intake pressure. Alternatively, the delay amount may be determined by calculation each time according to the difference between the engine speed, the target intake pressure, and the actual intake pressure. In particular, it is desirable that the amount of delay performed during acceleration according to the acceleration request is determined by the above method using the difference between the engine speed and the target intake pressure and the actual intake pressure.

The fuel injection control means 31 increases the fuel injection amount to the target fuel injection amount corresponding to the acceleration request after the time corresponding to the delay amount has elapsed. Here, the smoke limit injection amount is not set as in the conventional case, and the injection amount is continuously increased up to the fuel injection amount originally required based on the accelerator opening degree. Further, the rate of increase, that is, the degree of increase per unit time is also set in the same manner as in normal control.

An engine control method using this engine control device will be described with reference to FIGS. 2 to 4.

In the flowchart of FIG. 3, first, in step S1, the operating state of the engine and the driving state of the vehicle are detected. Here, the operating state includes the engine speed, the pressure in the intake passage 1 by the supercharger T (hereinafter, referred to as the intake pipe pressure), the accelerator opening degree, the torque of the engine, and the like.

Based on these information on the operating state, the acceleration determination is performed in step S2. The acceleration determination can be set so as to determine that an acceleration request has been made, for example, when the amount of change in the accelerator opening within a predetermined time exceeds a predetermined amount, that is, when the accelerator is depressed deeply. Alternatively, it can be set to determine that an acceleration request has been made when the speed of change of the accelerator opening exceeds a predetermined speed, that is, when the accelerator is suddenly depressed.

When it is determined that the acceleration request has been made, the process proceeds to step S3, and the delay control at the start time of the acceleration request is started. If it is determined that there is no acceleration request, the process proceeds to step S13, and normal control is continued.

In step S3, the delay amount of the response delay at the time of acceleration determination is calculated as the control of the delay at the start time of the acceleration request.

The delay amount at the start time of the acceleration request is calculated by, for example, as shown in FIG. 4A, a graph composed of the engine speed and the required torque corresponding to the acceleration request.

In FIG. 4A, one delay amount is determined for each region on the graph corresponding to the engine speed on the horizontal axis of the coordinates and the required torque on the vertical axis. In the regions a to g in the figure, the region a has the smallest delay amount, and the region g has the largest delay amount. Therefore, the delay amount tends to be set smaller as the engine speed increases, and the delay amount tends to be set smaller as the required torque increases.

When the delay amount is determined, the process proceeds to step S4 and the delay is executed. When the delay is executed, the fuel injection amount is not increased until the time corresponding to the delay amount elapses. That is, if the fuel injection amount is zero before the acceleration request, the injection amount is maintained at zero, and if the fuel injection amount is a certain value before the acceleration request, the injection amount of a certain value is maintained, and the delay amount is maintained. Wait for the passage of time corresponding to. When the time corresponding to the delay amount has elapsed, in step S5, the increase in the fuel injection amount that should be originally performed is started.

Next, in step S6, the engine speed and the supercharging pressure are detected in order to determine whether or not to control the delay during acceleration due to the acceleration request. The supercharging pressure is the intake pipe pressure. At this time, the increase in fuel injection amount based on the acceleration request is still in progress.

Here, if the boost pressure difference is equal to or less than the threshold value (step S7), there is no large difference between the target intake pipe pressure and the actual intake pipe pressure, so the delay is not controlled during acceleration. Therefore, after the currently ongoing increase in the fuel injection amount is completed, the process proceeds to step S13, and the normal control is continued. At this time, the amount of fuel is increased up to the target fuel injection amount corresponding to the acceleration request.

If the boost pressure difference exceeds the threshold value (step S7), there is a large difference between the target intake pipe pressure and the actual intake pipe pressure, so the delay during acceleration is controlled.

First, in step S8, the increase in fuel injection is temporarily stopped. Next, in step S9, the delay amount during acceleration is calculated based on the boost pressure difference, which is the difference between the engine speed and the target intake pipe pressure corresponding to the acceleration request and the actual intake pipe pressure.

The amount of delay during acceleration is calculated, for example, by a graph composed of the engine speed and the difference in boost pressure, as shown in FIG. 4 (b).

In FIG. 4B, one delay amount is determined for each region on the graph corresponding to the engine speed on the horizontal axis of the coordinates and the boost pressure difference on the vertical axis. In the regions a'to h'in the figure, the region a'has the smallest delay amount, and the region h'has the largest delay amount. Therefore, the delay amount tends to be set smaller as the engine speed increases, and the delay amount tends to be set smaller as the boost pressure difference decreases.

If the amount of delay during acceleration is determined, the delay is executed in step S10. In step S8, since the increase in the fuel injection amount has already been suspended, the increase in the fuel injection amount is not restarted until the time corresponding to the determined delay amount has elapsed. That is, the fuel injection amount immediately before the delay execution is maintained, and the elapse of the time corresponding to the delay amount is awaited. When the time corresponding to the delay amount has elapsed, in step S11, the increase in the fuel injection amount that should be originally performed is started. The amount of fuel is increased up to the target fuel injection amount corresponding to the acceleration request, and the control returns to the normal control (step S12, step S13).

That is, here, the determination of the delay amount performed during acceleration and the command of the fuel injection timing to the fuel injection control means 31 based on the delay amount are the fuel injection based on the passage of the delay amount performed at the start timing of the acceleration request. This is done after the fuel has been injected into the control means 31.

The effects of adopting the engine control device and the engine control method are shown in FIGS. 2 (a) to 2 (d).

FIG. 2A shows a change in the accelerator opening based on the operation of the driver. The rising point of the graph at the left end of the graph is the start time of the acceleration request. After the accelerator opening reaches a certain value, it is assumed that a constant accelerator opening is maintained.

FIG. 2B shows the time course of the change in the intake pipe pressure. FIG. 2C shows the passage of fuel injection amount over time. FIG. 2D shows the time course of the amount of smoke generated in the exhaust gas.

The broken line (corresponding to reference numeral 1) in each graph shows the transition of the numerical value when the fuel injection amount corresponding to the acceleration request is increased as usual without controlling the delay. As shown in FIG. 2D, the amount of smoke generated is large.

The thick solid line (corresponding to reference numeral 2) in each graph shows the transition of the numerical value when the smoke limit injection amount is set and the total fuel injection amount is reduced without controlling the delay. Shown. As shown in FIG. 2D, the amount of smoke generated is reduced, but the rise of the intake pipe pressure is delayed. In addition, since the fuel injection amount is reduced from beginning to end, it is assumed that the generated torque often does not reach the target torque.

The solid thin line (corresponding to reference numeral 3) in each graph shows the transition of the numerical value when the delay is executed. As shown in FIG. 2D, the amount of smoke generated is reduced, and the rise of the intake pipe pressure is sufficiently ensured. In FIG. 2B, the intake pipe pressure at the time of executing the delay almost coincides with the target intake pipe pressure, and the response delay of the boost pressure is almost eliminated.

In particular, in this embodiment, since the variable capacity turbocharger is used as the supercharger T, it can be said that the effect of eliminating the response delay of the supercharging pressure is high. This is because in the variable capacity turbocharger, when the movable vane is operated by negative pressure control, the operation responsiveness of the movable vane tends to be delayed.

In this way, for the acceleration request, the delay amount that delays the increase in the fuel injection amount corresponding to the acceleration request is set, so that the generation of smoke is more reliably suppressed without sacrificing the torque at the time of the acceleration request. be able to.

1 Intake passage 2 Exhaust passage 20 Low pressure exhaust recirculation passage 21, 24 Exhaust recirculation valve 22, 25 Throttle valve 23 High pressure exhaust recirculation passage 6 Intake cooling device (intercooler)
7 Turbine 8 Exhaust purification unit 9 Muffler 10 Reflux gas cooler 11 Piston 12 Combustion chamber 13 Fuel injection valve (injector)
14 Airflow sensor 15 Movable vane 16 Smoke sensor 17 Compressor 18 Intake pipe pressure detecting means 30 Electronic control unit 31 Fuel injection controlling means 32 Delay amount determining means

Claims (1)

A supercharger that increases the pressure of the intake air introduced into the combustion chamber,
A fuel injection valve that injects fuel into the intake air and
A fuel injection control means for controlling the fuel injection timing and injection amount by the fuel injection valve, and
A delay amount determining means for determining a delay amount for delaying an increase in the fuel injection amount corresponding to the acceleration request with respect to the acceleration request and issuing a command for the fuel injection timing to the fuel injection control means based on the delay amount. Prepare,
The delay amount determining means includes the delay amount performed at the start time of the acceleration request and the delay amount performed during acceleration by the acceleration request after the delay amount performed at the start time of the acceleration request has elapsed. Decide,
The delay amount performed at the start time of the acceleration request is set smaller as the engine speed is larger, and is set smaller as the required torque corresponding to the acceleration request is larger.
The delay amount performed during the acceleration is set smaller as the engine speed is larger, and is set larger as the difference between the target intake pressure corresponding to the acceleration request and the actual intake pressure is larger. Control device.

Images