JP2015190349A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a turbo lag as much as possible in an internal combustion engine with an exhaust gas turbocharger.SOLUTION: An internal combustion engine with an exhaust gas turbocharger mounts therein a control device correcting an injection quantity of fuel to be increased so as to make an air-fuel ratio in a case in which an actual intake air pressure is lower than a target boost pressure in response to the opening of an accelerator or a change rate of the opening of the accelerator per unit time by a predetermined value in an operation range in which the opening of the accelerator or the change rate of the opening of the accelerator per unit time exceeds a predetermined value, than an air-fuel ratio in a case otherwise.

Description

  The present invention relates to a control device for an internal combustion engine including an exhaust turbocharger.

  In a vehicle equipped with an internal combustion engine equipped with an exhaust turbocharger, the flow rate and temperature of the exhaust gas flowing into the exhaust turbine are low when the driver performs an operation to increase the accelerator opening in order to accelerate the vehicle, The turbine is not driven sufficiently. Therefore, even if the driver increases the accelerator opening, the so-called turbo lag, which takes time until the engine torque rises, is not a problem because the boost pressure and thus the amount of air charged in the cylinder does not increase. Yes.

  One way to mitigate this turbo lag is to open the throttle valve more than the normal opening according to the amount of depression of the accelerator pedal when the required load is high and the boost pressure is below a specified value. It is considered to perform correction control to increase the degree (see, for example, Patent Document 1). By such correction control, the intake air amount can be increased during the turbo lag period, and the engine torque can be increased more quickly.

JP-A-62-240436

  However, increasing the amount of intake air by increasing the opening of the throttle valve is equivalent to incorporating a large amount of low temperature fresh air into the internal combustion engine. Therefore, depending on the conditions of the outside air temperature and the like, the work amount of the exhaust turbine does not necessarily increase as expected, and the turbo lag may not be sufficiently eliminated.

  The present invention pays attention to the above points and aims at reducing the turbo lag as much as possible.

  In order to solve the above problems, a control device for an internal combustion engine according to the present invention has a configuration as described below. In other words, the control device for an internal combustion engine according to the present invention is configured so that the actual intake pressure depends on the accelerator opening or the rate of change per unit time in an operating region where the accelerator opening or the rate of change per unit time exceeds a predetermined value. When the target boost pressure is smaller than a predetermined value, the fuel injection amount increase correction is executed so that the air-fuel ratio becomes smaller than when the target boost pressure is not.

  In such a case, the fuel injection amount is increased so that the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio during a period until the difference between the actual intake pressure and the target supercharging pressure falls below a predetermined value. Thus, the engine torque generated in the cylinder can be increased and the turbo lag can be reduced. Further, since the temperature of the exhaust gas passing through the turbine can be increased by increasing the fuel injection amount and the thermal expansion when passing through the turbine can be promoted, the turbo lag can also be reduced from this point.

  In the present invention, “the actual intake pressure is smaller than the target boost pressure corresponding to the accelerator opening or the rate of change per unit time by a predetermined value or more” includes a case where the predetermined value is zero. In other words, it includes a case where the actual intake pressure is simply smaller than the target boost pressure corresponding to the accelerator opening or the rate of change per unit time.

  According to the present invention, the turbo lag can be reduced as much as possible.

1 is a schematic diagram showing an internal combustion engine according to an embodiment of the present invention. The flowchart which shows the control procedure of the embodiment roughly. Action | operation explanatory drawing of the same embodiment.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment.

  The internal combustion engine in the present embodiment is a spark ignition gasoline engine, and includes a plurality of, in the present embodiment, three cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes spark discharge between the center electrode and the ground electrode. The ignition coil is integrally incorporated in a coil case together with an igniter that is a semiconductor switching element.

  The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, a compressor 51 of the exhaust turbo supercharger 5, an intercooler 35, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

  The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42, a drive turbine 52 of the exhaust turbocharger 5, and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4. In addition, an exhaust bypass passage 43 that bypasses the turbine 52 and a waste gate valve 44 that is a bypass valve that opens and closes the inlet of the bypass passage 43 are provided. The waste gate valve 44 is an electric waste gate valve that can be opened and closed by inputting a control signal n to the actuator, and a DC servo motor is used as the actuator.

  The exhaust turbocharger 5 is configured such that the drive turbine 52 and the compressor 51 are connected and linked in a coaxial manner. Then, the driving turbine 52 is rotationally driven by using the energy of the exhaust gas, and the compressor 51 is pumped by using the rotational force, whereby the intake air is pressurized and compressed (supercharged) and sent to the cylinder 1.

  An ECU (Electronic Control Unit) 0 that is a control device of the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal (N signal) b output from an engine rotation sensor that detects the rotation angle of the crankshaft and the engine speed, An accelerator opening signal c output from a sensor that detects the amount of depression of the accelerator pedal or the opening of the throttle valve 32 as an accelerator opening (so-called required load), and a brake that is output from a sensor that detects the amount of depression of the brake pedal Stepping amount signal d, intake air temperature / intake pressure signal e output from a temperature / pressure sensor for detecting intake air temperature and intake pressure in intake passage 3 (especially surge tank 33), water temperature sensor for detecting engine cooling water temperature The coolant temperature signal f output from the sensor (or the shift position switch) Shift range signal g outputted from), a cam angle signal (G signal output from the cam angle sensor at a plurality of cam angle of the intake camshaft or an exhaust camshaft) h or the like is input.

  From the output interface, an ignition signal i for the igniter of the spark plug 12, a fuel injection signal j for the injector 11, an opening operation signal k for the throttle valve 32, and an opening operation signal for the waste gate valve 44. n and the like are output.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed, the intake air amount, and the like, various operating parameters such as required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, and ignition timing are determined. As the operation parameter determination method itself, a known method can be adopted. Thus, the ECU 0 applies various control signals i, j, k, n corresponding to the operation parameters via the output interface.

The ECU ₀ determines whether the accelerator opening θ or the accelerator opening θ indicated by the accelerator opening signal c, or the change rate dθ / dt per unit time thereof exceeds the predetermined values θ ₀ and (dθ / dt) ₀ , respectively. A target boost pressure p ₀ is determined in accordance with the rate of change dθ / dt per unit time. Then, the following control is performed to reduce the turbo lag.

That is, when the actual intake pressure p in the surge tank 33 indicated by the intake air temperature / intake pressure signal e is smaller than the target boost pressure p ₀ by a predetermined value Δp ₀ or more, the cylinder 1 is compared with the other cases. An increase correction program for executing an increase correction of the fuel injection amount is executed so that the air-fuel ratio of the intake air to be filled becomes smaller, that is, on the rich side. The predetermined value Δp ₀ is a value arbitrarily determined within a range of 0 or more, and is specifically determined based on experiments or the like. A control procedure by the increase correction program will be described below with reference to FIG. 2 which is a flowchart.

When the accelerator opening θ exceeds the predetermined value θ ₀ or the rate of change dθ / dt per unit time thereof exceeds the predetermined value (dθ / dt) ₀ (S1), the accelerator opening θ and the unit time per unit time The target boost pressure p ₀ is determined using the change rate dθ / dt of the parameter as a parameter (S2). After that, the fuel injection amount at which the air-fuel ratio becomes the stoichiometric air-fuel ratio is determined using the actual intake pressure p as a parameter (S3), the actual intake pressure p is smaller than the target boost pressure p ₀ and the difference is a predetermined value Δp. _When it exceeds ₀ (S4), the fuel injection amount is increased so that the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio, and more preferably the air-fuel ratio becomes about 13-14 (S5). On the other hand, otherwise, the fuel injection amount is not increased.

In the control described above, as shown in FIG. 3, when the accelerator opening θ is increased (time t ₁ ), the fuel injection amount is increased from the injection amount that becomes the stoichiometric air-fuel ratio indicated by the broken line in FIG. It becomes the quantity shown by. Thereafter, after the accelerator opening θ becomes constant (time t ₂ ), the difference between the actual intake pressure p and the target boost pressure p ₀ falls below the predetermined value Δp ₀ (time t ₃ ). That is, the fuel injection amount is increased until the engine torque generated in the cylinder reaches a desired value. That is, the length of the turbo lag period is d ₁ in FIG. The length of the period during which the fuel injection amount is increased is the time until the air at the outlet of the compressor 51 of the exhaust turbocharger 5 reaches the inside of the surge tank 33 when the accelerator opening θ starts to increase. This is roughly equivalent to one engine revolution. On the other hand, since the length of the turbo lag period when the fuel injection amount is not increased is d ₂ in the figure, the turbo lag is reduced by performing the above-described control. Then, when the difference between the actual intake pressure p and the target supercharging pressure p ₀ falls below a predetermined value Δp ₀ , the control returns to the control of injecting fuel by an amount that becomes the stoichiometric air-fuel ratio.

As described above, according to the present embodiment, the air-fuel ratio is richer than the stoichiometric air-fuel ratio during the period until the difference between the actual intake pressure p and the target boost pressure p ₀ falls below the predetermined value Δp _0. By increasing the fuel injection amount so as to be on the side, the engine torque generated in the cylinder 1 can be increased, so that the turbo lag can be reduced. At the same time, drivability can be improved. Further, since the temperature of the exhaust gas passing through the turbine 52 can be increased by increasing the fuel injection amount and thermal expansion when passing through the turbine 52 can be promoted, the turbo lag can also be shortened from this point. it can. Further, increasing the fuel injection amount also increases the exhaust gas pressure, and the work amount due to expansion when the exhaust gas passes through the turbine 52 also increases. That is, it is possible to more effectively perform energy conversion using the expansion when the exhaust gas passes through the turbine 52 as drive energy for the turbine 52.

  The present invention is not limited to the embodiment described above.

For example, in the above-described embodiment, the predetermined value Δp ₀ may be zero. In other words, when the actual intake pressure is simply smaller than the target boost pressure corresponding to the accelerator opening or its rate of change per unit time, the air-fuel ratio becomes smaller, that is, on the rich side compared to the case where it is not. In this manner, the fuel injection amount increase correction may be executed.

  Further, in the above-described embodiment, the control of the present invention is performed to reduce the turbo lag in the operation region where the accelerator opening or the rate of change of the accelerator opening per unit time exceeds a predetermined value. In the operation region where the engine pressure exceeds the predetermined value, the control of the present invention is performed to reduce the turbo lag, that is, the condition of step S1 of the above-described embodiment is that the accelerator opening exceeds the predetermined value. Good. On the other hand, even if the control of the present invention is performed to reduce the turbo lag in the operation region where the rate of change of the accelerator opening per unit time exceeds a predetermined value, in other words, the condition of step S1 of the above-described embodiment is satisfied. “The rate of change of the accelerator opening per unit time may exceed a predetermined value”. Further, in the operation region where the accelerator opening and the change rate per unit time of the accelerator opening each exceed a predetermined value, the control of the present invention may be performed to reduce the turbo lag, that is, step S1 of the above-described embodiment. The above condition may be that “the accelerator opening and the rate of change of the accelerator opening per unit time each exceed a predetermined value”.

  In addition, various changes may be made without departing from the spirit of the present invention.

0 ... Control unit (ECU)
11 ... Injector 5 ... Exhaust turbocharger c ... Accelerator opening signal e ... Intake air temperature / intake pressure signal

Claims (1)

A control device for an internal combustion engine including an exhaust turbocharger,
In the operating range where the accelerator opening or the rate of change per unit time exceeds the specified value,
When the actual intake pressure is smaller than the target boost pressure according to the accelerator opening or its rate of change per unit time by a predetermined amount or more, the fuel injection amount is set so that the air-fuel ratio is smaller than when the actual intake pressure is not. A control device for an internal combustion engine that performs an increase correction.

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