JP6070980B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine. In particular, the present invention relates to control for adjusting a negative pressure to be supplied to a brake booster that is a booster that boosts a brake operation force by using an intake negative pressure of an internal combustion engine.

  2. Description of the Related Art Conventionally, a brake booster that boosts the pedal effort using intake negative pressure of an internal combustion engine has been employed to reduce the operating force required when braking the vehicle, that is, the pedal effort of the brake pedal (for example, the following) See patent literature). This type of brake booster has a constant pressure chamber in which intake negative pressure is stored and a variable pressure chamber into which atmospheric pressure is introduced. When the driver is not stepping on the brake pedal, the constant pressure chamber communicates with the variable pressure chamber, and the introduction of atmospheric pressure into the variable pressure chamber is blocked. When the driver depresses the brake pedal, the constant pressure chamber and the variable pressure chamber are shut off, and atmospheric pressure is introduced into the variable pressure chamber, and a boosting action is generated due to a pressure difference between the constant pressure chamber and the variable pressure chamber.

JP 2003-148194 A

  When the vehicle is coasting with little or no depression of the accelerator pedal, so-called coasting, the opening of the throttle valve becomes 0 or almost 0, and the pumping loss increases. At this time, the internal combustion engine performs an engine braking action and consumes kinetic energy.

  Using the kinetic energy to drive the alternator to generate electric power, that is, to perform regenerative braking that recovers kinetic energy as electric energy, it can contribute to an improvement in the effective fuel consumption of the vehicle.

  Ideally, during regenerative braking, the throttle valve opening should be greatly opened to reduce engine braking. However, when the throttle valve is opened, the intake negative pressure generated on the downstream side of the throttle valve in the intake passage disappears. If so, there is a possibility that a sufficient negative pressure cannot be supplied to the brake booster.

  An object of the present invention is to suppress the pumping loss (or engine braking action) as much as possible while securing the negative pressure to be supplied to the brake booster.

In the present invention, when the fuel cut for temporarily stopping the fuel supply to the cylinder of the internal combustion engine is started, the negative pressure on the downstream side of the throttle valve in the intake passage is brought close to the target value of the negative pressure to be supplied to the brake booster. After that, the throttle valve opening is reduced, and then the brake booster is actually applied when the negative pressure downstream of the throttle valve in the intake passage reaches the target value or slightly exceeds the target value. Before the negative pressure supplied to the target value reaches the target value, an operation for increasing the opening of the throttle valve again is started.

  In addition, in the present invention, when the fuel cut for temporarily stopping the fuel supply to the cylinder of the internal combustion engine is started, the negative pressure target value to be supplied to the brake booster, the negative pressure on the downstream side of the throttle valve in the intake passage. The throttle valve opening is gradually reduced so that the difference between the negative pressure on the downstream side of the throttle valve and the negative pressure actually supplied to the brake booster does not increase beyond a predetermined level. A control device for an internal combustion engine characterized in that is constructed.

  ADVANTAGE OF THE INVENTION According to this invention, the pumping loss at the time of coasting can be suppressed, ensuring the negative pressure which should be supplied to a brake booster.

The figure which shows schematic structure of the internal combustion engine in one Embodiment of this invention. The flowchart which shows the example of the procedure of the process which the control apparatus of the embodiment performs. The flowchart which shows the example of the procedure of the process which the control apparatus of the embodiment performs. The figure which shows transition of the fluctuation | variation of the intake negative pressure during fuel cut, and the constant pressure chamber negative pressure of a brake booster.

  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. The internal combustion engine in the present embodiment is a spark ignition gasoline engine and includes a plurality of 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, 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 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  A brake booster 5 is attached to the vehicle of this embodiment. The brake booster 5 introduces intake negative pressure from a portion of the intake passage 3 downstream of the throttle valve 32, more specifically, from the surge tank 33, and uses this negative pressure to boost the pedaling force of the brake pedal. It is widely known in the field. The brake booster 5 has a constant pressure chamber for storing negative pressure and a variable pressure chamber for applying atmospheric pressure, and the constant pressure chamber is connected to the surge tank 33 via the negative pressure line 51. The negative pressure line 51 guides the intake negative pressure downstream of the throttle valve 32 to the constant pressure chamber. A check valve 52 is provided on the negative pressure line 51 to keep the negative pressure in the constant pressure chamber and prevent the positive pressure from being applied to the constant pressure chamber.

  When the brake pedal is not operated by the driver, the constant pressure chamber and the variable pressure chamber communicate with each other, and the variable pressure chamber is isolated from the atmospheric pressure. When the brake pedal is operated, the constant pressure chamber and the variable pressure chamber are interrupted, and the atmosphere is introduced into the variable pressure chamber. As a result, the pressure difference between the constant pressure chamber and the variable pressure chamber becomes a control pressure that boosts the depression force of the brake pedal. The brake pedal force amplified by the brake booster 5 is converted into hydraulic pressure in a master cylinder (not shown), and is supplied to a brake device (not shown) such as a brake caliper and a wheel cylinder via a hydraulic circuit (not shown). Communicated.

  An alternator (not shown) is connected to the crankshaft of the internal combustion engine via a winding transmission (belt and pulley, or chain and sprocket), a gear transmission (not shown), and the like. The alternator rotates by receiving a driving force transmitted from the crankshaft, and charges the generated power to an in-vehicle battery (not shown).

  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, Accelerator depression signal c output from a sensor that detects the amount of depression of the accelerator pedal (so-called required load), brake depression signal d output from a sensor that detects the depression amount of the brake pedal or master cylinder pressure, and intake passage 3 (in particular, surge tank 33), an intake air temperature / intake negative pressure signal e output from a temperature / pressure sensor that detects intake air temperature and intake negative pressure, and a pressure sensor that detects negative pressure in the constant pressure chamber of the brake booster 5. From the constant pressure chamber negative pressure signal f output from the sensor (shift position switch) to know the range of the shift lever Shift range signal g is the force, the cam angle signal (G signal) which is output from the cam angle sensor at a plurality of cam angle of the intake camshaft or an exhaust camshaft h the like are input.

  From the output interface, an ignition signal i is output to the igniter of the spark plug 12, a fuel injection signal j is output to the injector 11, an opening operation signal k is output to the throttle valve 32, and the like.

  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. A known method can be adopted as the operation parameter determination method itself. The ECU 0 applies various control signals i, j, k corresponding to the operation parameters via the output interface.

  When coasting is performed in which the driver's foot is away from the accelerator pedal and the vehicle is coasting, a fuel cut is performed to temporarily stop fuel supply (and ignition) to the cylinder 1 of the internal combustion engine. Normally, the ECU 0 performs the fuel cut when the fuel cut condition is satisfied when the accelerator pedal depression amount is 0 or less than a threshold value close to 0 and the engine speed is equal to or higher than the fuel cut permission speed. Then, when any fuel cut end condition is satisfied, such as when the accelerator pedal depression amount exceeds the threshold value, or the engine speed decreases to the fuel cut return speed, the fuel cut ends and the fuel injection resumes. .

  FIG. 2 and FIG. 3 show a procedure example of processing executed by the ECU 0 of the present embodiment during coasting. When the fuel cut condition is satisfied (stop S1), the ECU 0 stops fuel injection from the injector 11 (and ignition by the spark plug 12) (step S2). Further, in response to the operation of the accelerator pedal by the driver, that is, in response to the amount of depression of the accelerator pedal being 0 or below a threshold value close to 0, an operation of gradually reducing the opening of the throttle valve 32 is performed (step S3). ). In step S3, the negative pressure supplied to the constant pressure chamber of the brake booster 5 through the increase of the intake negative pressure (decrease as the pressure in the surge tank 33) is set to a target that is large enough to boost the brake operation force. It is intended to increase to a value (decrease as the constant pressure chamber pressure).

  FIG. 4 shows changes in changes in intake negative pressure downstream of the throttle valve 32 and negative pressure in the constant pressure chamber of the brake booster 5 during coasting. In FIG. 4, the intake negative pressure is drawn with a solid line, and the negative pressure inside the constant pressure chamber is drawn with a broken line.

  If the opening of the throttle valve 32 is reduced along with the establishment of the fuel cut condition, the intake negative pressure increases, and the negative pressure in the constant pressure chamber also increases following this intake negative pressure. However, the negative pressure line 51 and the check valve 52 are interposed between the surge tank 33 and the constant pressure chamber of the brake booster 5, and these serve as resistance against the air flow. Therefore, a time lag Δt is generated between the fluctuation of the intake negative pressure and the fluctuation of the constant pressure chamber negative pressure. Even if the throttle valve 32 is closed rapidly and the intake negative pressure is increased stepwise, the constant-pressure chamber negative pressure increases with a delay relative to the increase in the intake negative pressure. From the viewpoint of securing the negative pressure to be supplied to the brake booster 5, it is not always meaningful to close the throttle valve 32 rapidly when the fuel cut condition is satisfied.

  Therefore, in this embodiment, in step S3, the throttle valve 32 is gradually adjusted so that the amount of change (the absolute value thereof, in other words, the amount of decrease) per unit time of the opening degree of the throttle valve 32 is not more than a predetermined value. Slowly increase the throttle and intake negative pressure to suppress any pumping loss or engine braking action. In step S3, the time lag Δt between the intake negative pressure and the constant pressure chamber negative pressure or the difference Δp between the intake negative pressure and the constant pressure chamber negative pressure is measured, and the throttle is set so that the time lag Δt or the pressure difference Δp does not spread more than a predetermined value. It is preferable to adjust the amount of change per unit time of the opening of the valve 32.

  Thereafter, the ECU 0 starts the throttle valve 32 when the intake negative pressure reaches the target value or slightly exceeds the target value, that is, before the negative pressure in the constant pressure chamber reaches the target value (step S4). The operation of again expanding the opening degree of is performed (step S5). By step S3, a necessary and sufficient negative pressure is stored in the constant pressure chamber of the brake booster 5, and this negative pressure is maintained until the next time the brake pedal is depressed. Therefore, even during the fuel cut, the opening of the throttle valve 32 is increased after step S5 to reduce the pumping loss or the engine braking action.

  Furthermore, if the negative pressure in the constant pressure chamber reaches the target value (step S6), the speed at which the opening of the throttle valve 32 is increased is increased (step S7). That is, the amount of change per unit time of the opening degree of the throttle valve 32 is made larger than that in step S5.

  When the fuel cut end condition is satisfied (steps S8, S9, S10), the opening degree of the throttle valve 32 is corrected to an opening degree corresponding to the accelerator pedal depression amount by the driver (step S11). Fuel injection (and ignition by the spark plug 12) is resumed (step S12).

  In the present embodiment, when a fuel cut that temporarily stops the fuel supply to the cylinder 1 of the internal combustion engine is started, the negative pressure on the downstream side of the throttle valve 32 in the intake passage 3 is to be supplied to the brake booster 5. The control device 0 for the internal combustion engine is configured to perform the operation of reducing the opening of the throttle valve 32 until the target value is reached.

  In the present embodiment, during the fuel cut, the opening of the throttle valve 32 is not reduced until the intake negative pressure greatly increases beyond the target value, and the intake negative pressure is suppressed to a level slightly exceeding the target value. . This makes it possible to weaken the effectiveness of the engine brake during coasting, increase the amount of power generated by the alternator instead, and convert as much kinetic energy of coasting as possible into electrical energy for recovery (regeneration). Become. As a result, it is effective in improving the fuel consumption of the vehicle.

  In the present embodiment, when the fuel cut for temporarily stopping the fuel supply to the cylinder 1 of the internal combustion engine is started, the negative pressure on the downstream side of the throttle valve 32 in the intake passage 3 should be supplied to the brake booster 5. An operation of reducing the opening of the throttle valve 32 is performed so as to approach the target value of the negative pressure, and then the throttle valve is operated before the negative pressure actually supplied to the brake booster 5 reaches the target value. The control device 0 for the internal combustion engine is configured to start the operation of increasing the opening degree of 32 again.

  As described above, there is a time lag Δt between the fluctuation of the intake negative pressure and the fluctuation of the negative pressure in the constant pressure chamber. Therefore, by starting to increase the opening of the throttle valve 32 before the negative pressure in the constant pressure chamber reaches the target value, an unnecessary increase in the intake negative pressure is supplied while supplying the necessary and sufficient negative pressure to the brake booster 5. Is suppressed, pumping loss is reduced as much as possible, and regeneration by the alternator is increased as much as possible.

  In the present embodiment, when the fuel cut for temporarily stopping the fuel supply to the cylinder 1 of the internal combustion engine is started, the negative pressure on the downstream side of the throttle valve 32 in the intake passage 3 should be supplied to the brake booster 5. The throttle valve 32 is opened so that the difference Δp between the negative pressure on the downstream side of the throttle valve 32 and the negative pressure actually supplied to the brake booster 5 does not spread more than a predetermined value while approaching the negative pressure target value. A control device 0 for an internal combustion engine characterized in that an operation for gradually reducing the degree is performed.

  This also achieves the intended purpose of reducing the pumping loss as much as possible while ensuring the necessary and sufficient negative pressure for the brake booster 5.

  The present invention is not limited to the embodiment described in detail above. For example, in the above embodiment, the pressure in the constant pressure chamber of the brake booster 5 is actually measured through a sensor. However, the speed or time constant of the constant pressure chamber pressure following the fluctuation of the intake negative pressure is experimentally determined in advance. If it is obtained, the pressure difference Δp and the time lag Δt can be obtained by estimating the current constant pressure chamber pressure based on the time series of the actually measured value of the intake negative pressure. In short, a sensor for detecting the constant pressure chamber pressure is not essential.

  The present invention can also be applied to a hybrid vehicle. However, since the hybrid vehicle is operated for a long time in the fuel cut state, it is necessary to add a procedure not shown in the flowcharts of FIGS. That is, once the necessary and sufficient negative pressure is stored in the constant pressure chamber of the brake booster 5 in step S3, the negative pressure is maintained until the next time the brake pedal is depressed, but after the brake pedal is depressed, Then, it is necessary to return the process to step S3 again and gradually throttle the throttle valve 32 to ensure the negative pressure again.

  In addition, the specific configuration of each part, the specific processing procedure, and the like can be variously modified without departing from the spirit of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be used for the control of an automobile attached with a brake booster.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 3 ... Intake passage 5 ... Brake booster e ... Intake negative pressure signal f ... Constant pressure indoor negative pressure signal

Claims (2)

When starting a fuel cut that temporarily stops the fuel supply to the cylinders of the internal combustion engine, the throttle is set so that the negative pressure downstream of the throttle valve in the intake passage approaches the target value of the negative pressure to be supplied to the brake booster Perform the operation to reduce the valve opening,
Thereafter, when the negative pressure on the downstream side of the throttle valve in the intake passage reaches the target value or slightly exceeds the target value, the negative pressure actually supplied to the brake booster reaches the target value. A control apparatus for an internal combustion engine, wherein an operation for increasing the opening of the throttle valve again is started before. When the fuel cut to temporarily stop the fuel supply to the cylinder of the internal combustion engine is started, the negative pressure on the downstream side of the throttle valve in the intake passage is brought closer to the target value of the negative pressure to be supplied to the brake booster, An internal combustion engine characterized by performing an operation of gradually reducing the opening of the throttle valve so that the difference between the negative pressure downstream of the throttle valve and the negative pressure actually supplied to the brake booster does not spread beyond a predetermined level. Engine control device.

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