JP6177111B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for controlling an internal combustion engine attached with a variable valve timing (Variable Valve Timing) mechanism.

  In an internal combustion engine mounted on a vehicle, it is known to perform a fuel cut that temporarily stops fuel injection in accordance with the driving situation. Normally, 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, the fuel cut is started assuming that the fuel cut condition is satisfied. 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. .

  If the fuel supply is cut off suddenly when the engine torque is relatively large, a torque shock that causes the engine speed and the vehicle speed to drop stepwise occurs, causing the passengers including the driver to feel the shock. In order to reduce this torque shock, conventionally, even if the fuel cut condition is satisfied, the fuel injection is not stopped immediately, but the fuel injection is stopped after waiting for a certain delay time (for example, (See the following patent document).

Japanese Patent Laid-Open No. 10-030477

  Fuel injection and combustion are also continued during the delay time from when the fuel cut condition is satisfied to when fuel cut is actually started. Therefore, the effective fuel consumption is deteriorated accordingly. Therefore, it is required to reduce the engine torque as quickly as possible during this delay time.

  Use of an intake VVT mechanism is an effective way to quickly reduce engine torque. If the intake valve opening timing is delayed more than the exhaust top dead center and / or the intake valve closing timing is delayed more than the intake bottom dead center, the amount of intake air that is filled and compressed in the cylinder will be sufficiently reduced. The fuel injection amount can be reduced by that amount, and the engine torque generated by the combustion of the fuel can be reduced.

  However, if the intake valve timing is significantly retarded during the delay time after the fuel cut condition is established, the intake air amount and fuel injection amount that are charged into the cylinders will suddenly decrease, and the engine torque will drop sharply. There was concern to cause.

  The present invention has been made by paying attention to the above-described problem, and an object of the present invention is to appropriately suppress a torque shock at the time of fuel cut.

The present invention controls an internal combustion engine with a VVT mechanism that can change the intake valve timing (intake valve opening timing and / or closing timing), and if the fuel cut condition is satisfied, the engine torque is set as a target. The fuel supply to the cylinder is stopped after the elapse of a delay time for reducing to the torque, and the intake valve timing is retarded from the reference timing during idling in the delay time, and the intake valve in the delay time is A control device for an internal combustion engine is configured to decrease the maximum value of the timing retard amount and / or the retard speed as the difference between the engine torque and the target torque when the fuel cut condition is satisfied increases .

  According to the present invention, torque shock at the time of fuel cut can be appropriately suppressed.

The figure which shows schematic structure of the internal combustion engine in one Embodiment of this invention. The figure which shows the structure of the variable valve timing mechanism accompanying the internal combustion engine of the embodiment. The timing diagram which shows the content of the control which the control apparatus of the embodiment performs. The timing diagram which shows the content of the control which the control apparatus of the embodiment implements. The flowchart which shows the example of the procedure of the control which the control apparatus of the embodiment implements.

  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 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 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.

  An external EGR device 2 is attached to the internal combustion engine of the present embodiment. The external EGR device 2 realizes a so-called high-pressure loop EGR. The EGR device 21 communicates the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3, and the EGR passage 21. The EGR cooler 22 provided in the EGR passage and the EGR valve 23 that opens and closes the EGR passage 21 and controls the flow rate of the EGR gas flowing through the EGR passage 21 are used as elements. The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined location downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3, specifically to a surge tank 33.

  As shown in FIG. 2, in the internal combustion engine in the present embodiment, a timing chain 74 is wound around a crank sprocket 71, an intake-side sprocket 72, and an exhaust-side sprocket 73. Is transmitted to the intake camshaft via the intake side sprocket 72 and to the exhaust camshaft via the exhaust side sprocket 73.

  In addition, a VVT mechanism 6 is interposed between the intake side sprocket 72 and the intake camshaft. The VVT mechanism 6 in the present embodiment changes the opening / closing timing of the intake valve by changing the rotational phase of the intake camshaft with respect to the crankshaft.

  The housing 61 of the VVT mechanism 6 is fixed to the intake side sprocket 72, and the intake side sprocket 72 and the housing 61 rotate integrally with the crankshaft. On the other hand, the rotor 62 fixed to one end portion of the intake camshaft is housed in the housing 61 and can rotate relative to the intake-side sprocket 72 and the housing 61. A plurality of fluid chambers into which hydraulic fluid flows in and out are formed inside the housing 61, and each fluid chamber is partitioned into an advance chamber 612 and a retard chamber 611 by a vane 621 formed on the outer peripheral portion of the rotor 62. Has been.

  The hydraulic fluid stored in the oil pan 81 is supplied from the hydraulic pump 82 to the hydraulic (hydraulic) circuit of the VVT mechanism 6. The hydraulic pump 82 is driven by power from the internal combustion engine. An OCV (Oil Control Valve) 9 that is a switching control valve is provided between the hydraulic pump 82 and the VVT mechanism 6. By operating the flow rate and direction of the hydraulic fluid via the OCV 9, the hydraulic fluid pumped from the oil pan 81 can be selectively supplied to the advance chamber 612 or the retard chamber 611. Then, the housing 61 rotates relative to the rotor 62, and the opening / closing timing of the intake valve can be advanced or retarded.

  The OCV 9 is a so-called electromagnetic four-way spool valve. As shown in FIG. 2, the OCV 9 has a supply port 91 connected to the discharge port of the hydraulic pump 82, an A port 92 connected to the advance chamber 612 of the housing 61, and a B port connected to the retard chamber 611 of the housing 61. 93 and drain ports 94 and 95 connected to the oil pan 81. The spool of the OCV 9 switches the internal particle path by an advancing and retreating operation, and connects the A port 92 and the B port 93 to one of the supply port 91 and the drain ports 94 and 95, respectively. Further, when the spool 96 is in the neutral position, the internal fluid path is interrupted, and the A port 92 and the B port 93 are not communicated with the supply port 91 and the drain ports 94 and 95. FIG. 2 shows a state where the spool 96 is in the neutral position.

  The spool 96 is driven by a solenoid 97. That is, the advance / retreat distance of the spool 96 changes according to the duty ratio of the pulse current (or voltage) input to the solenoid 97 as the control signal m.

  When the duty ratio of the control signal m is relatively large, the hydraulic fluid pressure discharged from the hydraulic pump 82 is supplied to the advance chamber 612 through the A port 92, while already stored in the retard chamber 611. The hydraulic fluid flows down toward the oil pan 81 through the B port 93, and the vane 621 and the rotor 62 are rotated so that the volume of the advance chamber 612 is enlarged and the volume of the retard chamber 611 is reduced. As a result, the rotational phase of the intake camshaft, in other words, the displacement angle of the intake camshaft with respect to the crankshaft is advanced, and the valve timing of the intake valve is advanced.

  On the contrary, when the duty ratio of the control signal m is relatively small, the hydraulic fluid pressure discharged from the hydraulic pump 82 is supplied to the retard chamber 611 through the B port 93, while already stored in the advance chamber 612. The working fluid that has flown down flows toward the oil pan 81 through the A port 92, and the vane 621 and the rotor 62 rotate so that the volume of the retard chamber 611 is expanded and the volume of the advance chamber 612 is decreased. . As a result, the displacement angle of the intake camshaft with respect to the crankshaft is retarded, and the valve timing of the intake valve is retarded.

  Generally speaking, the valve timing of the intake valve is advanced faster as the duty ratio of the control signal m is larger than neutral, and the valve timing of the intake valve is retarded faster as the duty ratio is smaller than neutral.

  An ECU (Electronic Control Unit) 0 serving as a control device for an internal combustion engine according to 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 b output from an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and depression of an accelerator pedal. Accelerator opening signal c output from a sensor that detects the amount as an accelerator opening (engine output required by the driver, so-called required load), and output from a sensor (shift position switch) to know the range of the shift lever The shift range signal d, the intake air temperature / intake pressure signal e output from the temperature / pressure sensor for detecting the intake air temperature and the intake pressure in the intake passage 3 (particularly, the surge tank 33), and the cooling indicating the temperature of the internal combustion engine. The coolant temperature signal f output from the water temperature sensor for detecting the water temperature, the intake camshaft or the exhaust camshaft A cam angle signal g output from the cam angle sensor at the cam angle, a brake depression amount signal h or the like to be output from the sensor for detecting the amount of depression of the brake pedal is inputted.

  From the output interface, an ignition signal i for the igniter 13 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 EGR valve 23. l, a control signal m or the like is output to the OCV 9.

  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 and intake air amount, etc., the required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, required EGR rate (or EGR amount), Various operating parameters such as ignition timing and intake valve timing are determined. The ECU 0 applies various control signals i, j, k, l and m corresponding to the operation parameters via the output interface.

  The intake valve timing takes a reference timing at the start of the internal combustion engine, at idle, and in a low load operation region. At the reference timing, the intake valve opens at a timing near or near the exhaust top dead center, and closes when a predetermined crank angle (for example, 45 ° CA) elapses after the intake bottom dead center. In the operation range of medium load or high load, the intake valve timing is advanced from the reference timing. However, in the high speed range, it is preferable to delay the closing timing of the intake valve as the engine speed increases.

  ECU0 of this embodiment performs the fuel cut which stops fuel injection from the injector 11 temporarily according to a driving | running condition. Normally, it is assumed that 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.

  However, even if the combustion cut condition is satisfied, the fuel injection to the cylinder 1 is not immediately stopped. FIG. 5 shows a procedure of processing executed by the ECU 0 of the present embodiment at the time of fuel cut.

  When the fuel cut condition is satisfied (step S1), the ECU 0 calculates the difference between the engine torque and the target torque when the fuel cut condition is satisfied (immediately before, when, or just after the fuel cut condition is satisfied). (Step S2) Based on the magnitude of the difference, the transition of the intake valve timing in the delay period from the fuel cut condition establishment to the fuel cut start is determined (Step S3).

  The engine torque when the fuel cut condition is satisfied can be estimated based on the engine speed when the fuel cut condition is satisfied, the intake pressure in the surge tank 33, the intake air temperature (or the intake air amount filled in the cylinder 1), and the like. . In the memory of the ECU 0, map data that defines the relationship between the engine speed, the intake pressure, the intake air temperature, and the like and the engine torque is stored in advance. The ECU 0 searches the map using the engine speed, intake pressure, intake air temperature, etc. when the fuel cut condition is satisfied as keys, and knows the engine torque when the fuel cut condition is satisfied.

The target torque is the amount of torque reduction corresponding to the deceleration of the vehicle speed that does not cause the driver or passenger to feel an impact;
Torque reduction amount = allowable deceleration × (vehicle weight + passenger weight) ÷ transmission efficiency × wheel (tire) diameter ÷ transmission gear ratio ÷ differential ratio. The allowable deceleration is 0.08G, for example. The crew weight is, for example, 60 kg multiplied by the assumed number of people. If mainly two passengers are assumed, the crew weight is 120 kg. The transmission efficiency is the overall transmission efficiency of a drive system (for example, a torque converter, a forward / reverse switching device, a transmission, and a differential device) and wheels, for example, 0.9. The gear ratio of the transmission is a value corresponding to the gear ratio and shift position when the fuel cut condition is satisfied.

The target torque is the maximum value allowed for a decrease in engine torque due to fuel cut or fuel injection stop;
Target torque = torque reduction amount−defined by the mechanical loss of the internal combustion engine and auxiliary equipment after the fuel cut condition is satisfied. The term of mechanical loss in the decrease in engine torque caused by fuel cut includes the engine speed and engine cooling temperature after the fuel cut condition is satisfied, the operating status of the compressor for compressor compression of the air conditioner, and The value depends on the amount of power generated by the alternator. The term of mechanical loss increases as the engine speed increases, and increases as the cooling water temperature decreases. In particular, the cooling water temperature suggests friction in various parts of the engine. The lower the coolant temperature, the lower the engine temperature, the higher the viscosity of the lubricating oil, and the greater the friction.

  When the compressor for compressing the refrigerant is operating, the mechanical loss is larger than when the compressor is not.

  Furthermore, it goes without saying that the mechanical loss increases as the power generation amount of the generator (alternator) increases. The amount of power generated by the generator also depends on the operating status of the electrical load at that time and the state of charge of the battery (for example, if the electrical load is almost not operating and the battery is nearly fully charged, a high output voltage is obtained. Even if the regulator is commanded, the generator is in a state close to no-load operation). If the power generation amount (output current or output power) of the alternator can be directly measured, the mechanical loss may be calculated using the measured value. Otherwise, the power generation amount of the generator is estimated based on the DUTY ratio (fDUTY) of energization to the field coil of the generator, the state of charge of the battery, the engine speed, etc., and the mechanical loss is calculated.

As shown in FIG. 3 or FIG. 4, the ECU ₀ of the present embodiment performs intake air via the VVT mechanism 6 during the delay time from the time t ₀ when the fuel cut condition is satisfied to the time when fuel cut starts (fuel injection stops) An operation for delaying the valve timing from the reference timing is performed. By this operation, the intake valve opens later than the exhaust top dead center and closes after greatly exceeding the intake bottom dead center. The retarding of the opening timing of the intake valve delays the start of inflow of intake air from the intake passage 3 to the cylinder 1. In addition, the delay in the closing timing of the intake valve causes a phenomenon in which the intake air once sucked into the cylinder 1 is partially discharged (returned back) into the intake passage 3. Both of them serve to reduce the effective intake amount that is filled and compressed in the cylinder 1, thereby reducing the fuel injection amount and lowering the engine torque.

Transition of the retard operation of the intake valve timing in the delay time determined in step S3 is
(I) Maximum value ΔA of retard amount from reference timing of intake valve timing in delay time
(II) The retarding speed of the intake valve timing during the delay time (retarding amount per unit time or unit cycle) dA / dt
Either one or both.

  The maximum value ΔA of the retard amount is made smaller as the difference between the engine torque when the fuel cut condition is satisfied and the target torque is larger. In other words, when the difference between the engine torque and the target torque when the fuel cut condition is satisfied is relatively small (indicated by a broken line in FIG. 3), the maximum value ΔA is set relatively large and the intake valve timing is set. The angle is greatly retarded, and an early decrease in engine torque during the delay time is promoted. On the other hand, when the difference between the engine torque and the target torque when the fuel cut condition is satisfied is relatively large (indicated by a solid line in FIG. 3), the maximum value ΔA is set to be relatively small and the intake valve timing is not so much. Without retarding, it is possible to avoid a sudden decrease in the intake air amount and the fuel injection amount charged in the cylinder 1 during the delay time, thereby preventing the occurrence of a shock due to a rapid decrease in engine torque.

  Further, the retarded speed dA / dt is decreased as the difference between the engine torque and the target torque when the fuel cut condition is satisfied is increased. In other words, when the difference between the engine torque and the target torque when the fuel cut condition is satisfied is relatively small (indicated by a broken line in FIG. 4), the retarded speed dA / dT is set to be relatively large and the intake valve is set. The timing is rapidly retarded to promptly reduce the engine torque during the delay time. Conversely, if the difference between the engine torque and the target torque when the fuel cut condition is satisfied is relatively large (indicated by a solid line in FIG. 4), the retarded angular velocity dA / dt is set to be relatively small and the intake valve timing is set. Is slowly retarded to avoid a sudden decrease in the intake air amount and the fuel injection amount charged into the cylinder 1 during the delay time, thereby preventing the occurrence of a shock due to a rapid decrease in engine torque.

  Then, the ECU 0 retards the intake valve timing through the VVT mechanism 6 to the maximum value ΔA determined in step S3 and / or intakes at the retarded speed dA / dt determined in step S3. While performing the operation of retarding the valve timing (step S4), the operation of injecting and burning fuel into the cylinder 1 is continued even after the fuel cut condition is satisfied (step S5). By retarding the intake valve timing from the reference timing during the delay time, the retard correction amount of the ignition timing for the purpose of reducing engine torque can be reduced, which also improves the thermomechanical conversion efficiency. Can contribute.

  Thus, the ECU 0 estimates the current engine torque and determines whether or not the engine torque has decreased to the target torque (step S6). As already described, the current engine torque can be obtained by searching the map data using the current engine speed, intake pressure, intake temperature and the like as keys.

  If the current engine torque drops to the target torque, the fuel injection can be stopped, that is, the fuel injection (and (Ignition) is stopped (step S7). After the start of the fuel cut, that is, after the delay time has elapsed, the intake valve timing is returned to the reference timing via the VVT mechanism 6 (step S8).

  After the start of fuel cut, that is, after stopping fuel injection, if the fuel cut end condition is satisfied, such as the accelerator pedal depression amount exceeds the threshold value, the engine speed has decreased to the fuel cut return speed, etc. (Step S9), the fuel cut is ended, and fuel injection (and ignition) is restarted (Step S10).

  In the present embodiment, the variable valve timing mechanism 6 that can change the intake valve timing is controlled, and when the fuel cut condition is satisfied, the delay time for reducing the engine torque to the target torque. In this delay time, the intake valve timing is retarded from the reference timing during idling, and the delay amount (maximum value ΔA and / or delay). The control device 0 for the internal combustion engine is configured to vary the angular velocity dA / dt) according to the difference between the engine torque when the fuel cut condition is satisfied and the target torque.

  According to this embodiment, the torque shock at the time of fuel cut can be suppressed appropriately. If the engine torque when the fuel cut condition is satisfied is relatively small, the delay time until the engine torque is reduced to the target torque is shortened by increasing the intake valve timing and / or rapidly retarding, It is possible to improve fuel efficiency. On the other hand, if the engine torque when the fuel cut condition is satisfied is relatively large, the intake valve timing is made smaller and / or slowly retarded to suppress the occurrence of a shock due to a sudden decrease in engine torque. .

  The present invention is not limited to the embodiment described in detail above. For example, the VVT mechanism 6 in the above embodiment is of a vane type that changes the rotational phase angle of the intake camshaft relative to the crankshaft by hydraulic pressure (hydraulic pressure), but the change of the rotational phase angle is realized by an electric motor. The motor drive VVT to be used may be employed as the VVT mechanism 6. In addition, various VVT mechanisms such as an electromagnetic solenoid valve that can be controlled to open and close by inputting a control signal from the ECU 0 can be used.

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

  The present invention can be applied to control of an internal combustion engine mounted on a vehicle.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 11 ... Injector 12 ... Spark plug 3 ... Intake passage 32 ... Throttle valve 6 ... Variable valve timing (VVT) mechanism

Claims (1)

Controlling an internal combustion engine with a variable valve timing mechanism capable of changing the intake valve timing,
When the fuel cut condition is satisfied, the fuel supply to the cylinder is stopped after waiting for the delay time to reduce the engine torque to the target torque.
In the delay time, the intake valve timing is delayed from the idle reference timing,
A control apparatus for an internal combustion engine, which decreases the maximum value or retard speed of the intake valve timing during the delay time as the difference between the engine torque and the target torque when the fuel cut condition is satisfied increases .

Images