DE102007000830B4 - Engine control system - Google Patents

Abstract

An engine control system comprising: a variable valve timing apparatus (31, 32) for variably controlling a valve timing of at least one of an intake valve (29) and an exhaust valve (30) of an internal combustion engine (11); andan intake air control device (33) for controlling an intake air amount, wherein a control unit (28) is provided with a transition control means (101-103, 105, 106) for controlling the variable valve timing device to have an operation time therefrom at the same time or in advance to an operation change the intake air control device (33) is an electronic throttle device that controls a throttle valve (16) of the internal combustion engine by an electric actuator (15); The control unit (28) further controls a throttle control means (107) for controlling the electronic throttle device to change a throttle position with a throttle delay time (Td) with respect to a change of an accelerator position and a valve timing controller (104) for controlling the variable valve timing apparatus such that an actual valve timing coincides with a target valve timing; andthe transient control means (101-103, 105, 106) includes load estimation means (101, 102) for estimating a load based on the accelerator position when the torque change request is generated in response to an accelerator position change, setting means (103) for setting a target valve time based on the accelerator position change load estimated by the load estimator and synchronization means (105, 106) for synchronizing the actual valve time, which varies with the target valve time, and the actual load, which varies with the throttle position, characterized in that the synchronizer (105, 106) has a valve time delay time ( Vd) which is from a target valve timing change to an actual valve timing change to be substantially equal to a throttle delay time thereby to synchronize the actual valve timing change and the actual load change , and the synchronizing means (105, 106) varies the throttle delay time to be equal to the valve timing delay time.

Description

The present invention relates to an engine control system having a variable valve timing apparatus that variably controls a valve operating time of an intake valve or an exhaust valve of an internal combustion engine.

A current internal combustion engine mounted in a vehicle has a variable valve timing device that variably adjusts valve timing (opening or closing operation timing) of an intake valve or an exhaust valve for increasing output, reducing fuel consumption, reducing exhaust emission, and the like controls.

DE 198 10 298 A1 discloses a valve timing control for an engine having an electronic throttle control system in which the response of a valve timing control (VVT) mechanism is estimated by the operating condition of the engine. In addition to controlling a relative rotation angle of the VVT, a throttle correction factor for correcting the opening angle of a throttle valve is calculated so that it is adjusted to the response of the VVT. The throttle valve is controlled by the calculated factor. If the response of the VVT is slow, then the throttle valve opening angle is corrected based on the response. Consequently, rapid engine acceleration is suppressed, thereby preventing the occurrence of misfire.

EP 1 405 997 A2 discloses a plurality of intake air quantity control means 17, 19, 21 for controlling an amount of air in conjunction with a depression stroke of an accelerator pedal being drawn into a combustion chamber. Each of the intake air amount control means responds to a change in the depression stroke of the accelerator pedal after elapse of a predetermined delay time. The electronic control unit delays response of each of the intake air quantity control units (17, 19, 21) with respect to depression of an accelerator pedal (14) by a delay time. The delay time is set so that timings when the intake air amount control units influence an amount of air drawn into the combustion chamber are coincident with each other.

When controlling the variable valve timing device as shown in FIG JP 2002-206456A For example, a data map of the target valve timing in accordance with various engine operating conditions is generated by matching with the timing of a design phase and stored in a memory of an engine control unit. During engine operation, the engine control unit scans the target valve timing stored in the memory in accordance with the engine operating condition, and controls the variable valve timing apparatus so that the actual valve timing is brought to the target valve timing.

The variable valve timing apparatus is combined with an electronic throttle device that controls a throttle opening angle (throttle position) of an internal combustion engine by an electric motor in response to an accelerator position. In such a system as in 4 10, when an accelerator position is changed to decrease an output torque of the internal combustion engine, a throttle position is shifted in a throttle closing direction with some time delay to reduce an intake air amount supplied to the internal combustion engine. An actual intake air amount that changes with the throttle position is detected or estimated. A target valve timing for opening an intake valve is set in accordance with the detected or estimated actual intake air amount by using a data map of the target valve time. The variable valve timing apparatus is controlled so that actual valve timing is brought to the target valve timing.

However, if the variable valve timing device is of a hydraulically actuated type, the actual valve timing (dotted line) is delayed relative to the target valve time (solid line), i.e., the valve timing. h., relative to the change of the actual intake air amount that varies in accordance with the throttle position. This delay is caused by a response delay of a hydraulic fluid supply system for the variable valve timing device. As a result, in the transient operation time in which the accelerator position is rapidly changed to change the engine output torque, the combustion condition is deteriorated for a moment and an uncomfortable excessive torque change is caused.

It is therefore proposed to limit a change in the target valve timing at the time of a rapid change in the engine operating condition, so that the delay of the actual valve timing relative to the target valve timing is reduced. Since this limiting operation reduces a change in the target valve timing, the target valve timing can not be set to a desired valve timing most appropriate for the engine operating condition at that time.

It is therefore an object of the present invention to provide an engine control system in which an appropriate target valve timing can be adjusted in accordance with an engine operating condition and fuel consumption improved without causing poor combustion in the internal combustion engine due to a response delay at the time of transient condition.

This object is achieved by an engine control system according to claim 1. Advantageous developments are the subject of the dependent claims.

According to the present invention, an engine control system includes a variable valve timing apparatus, an intake air control apparatus, and a control unit. The variable valve timing apparatus variably controls a valve timing of at least one of an intake valve and an exhaust valve of an internal combustion engine. The intake air control device controls an intake air amount. The control unit controls the variable valve timing device to change an operation time thereof at the same time or before a change of the operation of the intake air control device when a torque change request is generated to request a torque change of the internal combustion engine, thereby to cause combustion in the internal combustion engine increase.

• 1 ein schematisches Diagramm, das ein Brennkraftmaschinensteuerungssystem mit einer Vorrichtung zur variablen Ventilzeitabstimmung gemäß einer Ausführungsform der vorliegenden Erfindung zeigt;
• 2 ein Zeitdiagramm, das eine Übergangsventilzeit und einen Drosselsteuerungsbetrieb in der Ausführungsform zeigt;
• 3 ein Flussdiagramm, das eine Übergangsventilzeit und ein Drosselsteuerungsprogramm zeigt, das in der Ausführungsform ausgeführt wird; und
• 4 ein Zeitdiagramm, das einen Übergangsventilzeitsteuervorgang in einem System des Standes der Technik zeigt.

The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the attached drawings. In the drawings are:

• 1 12 is a schematic diagram showing an engine control system having a variable valve timing apparatus according to an embodiment of the present invention;
• 2 Fig. 10 is a time chart showing a transitional valve timing and a throttle control operation in the embodiment;
• 3 FIG. 10 is a flowchart showing a transitional valve timing and throttle control program executed in the embodiment; FIG. and
• 4 a timing chart showing a transition valve timing control in a system of the prior art.

First, referring to 1 has an internal combustion engine 11 an inlet pipe 12 , An air filter 13 is provided at the furthest upstream part of the intake pipe 12, and an air flow meter 14 is provided downstream of the air filter 13. A throttle valve 16 is provided downstream of the air flow meter 14, wherein an opening angle position thereof by an electric actuator, such as an electric motor 15 is controlled. Furthermore, downstream of the air filter 13 an electronic throttle device 33 as an intake air amount control means. The electronic throttle device 33 has a throttle position sensor 17 that detects a throttle opening angular position.

Downstream of the throttle valve 16 is a surge tank 18 intended. An inlet pressure sensor 19 is in the expansion tank 18 provided to detect an inlet pressure in the inlet pipe. A plurality of inlet distribution passages 20 are connected to the surge tank 18 connected to intake air in respective cylinders of the internal combustion engine 11 initiate. A fuel injector 21 is in each intake distribution passage 20 provided near the inlet port of the cylinder to inject fuel into the corresponding cylinder. At each cylinder head of the internal combustion engine 11 a spark plug 22 is mounted so that an air-fuel mixture in each cylinder by a spark discharge of the spark plug 22 is ignited.

The internal combustion engine 11 also has a hydraulically actuated intake-side variable valve timing device 31 and a hydraulically operated exhaust-side variable valve timing device 32 , The variable valve timing device 31 is for variably controlling a valve timing (opening and closing operation time) of an intake valve 29 from every cylinder. The variable valve timing device 32 is for variably controlling a valve timing of an exhaust valve 30 from every cylinder.

An exhaust gas sensor (air-fuel ratio sensor or oxygen sensor) 24 is in an exhaust pipe 23 the internal combustion engine 11 provided to detect an air-fuel ratio or a rich / lean state of the exhaust gas. A catalyst 25, such as a three-way catalyst, is provided downstream of the exhaust gas sensor 24 to purify the exhaust gas.

On the cylinder block of the internal combustion engine 11 are a coolant temperature sensor 26 and a crankshaft angle sensor 27 mounted to detect a coolant temperature or a rotational position of a crankshaft of the internal combustion engine 11. An engine speed, etc. is based on the output of the crankshaft angle sensor 27 detected. An accelerator sensor 34 is provided with an accelerator (not shown). which is operated by a driver to detect an accelerator position.

The output signals of these sensors are transferred to the electronic control unit (ECU) 28 entered. The ECU 28 has a microcomputer and executes various engine control programs stored in a built-in ROM, a fuel injection amount of the fuel injector 21, and an ignition timing (ignition timing) of the spark plug 22 in accordance with engine operating conditions. The ECU 28 also implements a transitional timing program, which will run in 3 is shown to the inlet side device for variable valve timing 31 and the electronic throttle device 33 in a transitional time in which the accelerator is operated to change an output torque of the internal combustion engine 11 in the following manner.

As in 2 is shown, when the accelerator position is changed to make a quick torque change (eg, prompt torque decrease request) at time t1, a load (eg, an intake air amount or an intake air pressure) in accordance with an accelerator position and a target valve time (predetermined advance angle of a valve opening operation ) of the inlet valve 29 estimated at this time. This load estimate can be made using a data map (table) or mathematical equations.

Further, a new target valve timing is calculated in accordance with the estimated load, an engine speed, and the like by referring to the data map of the target valve time. This data map of the target valve timing sets optimal valve timing determined by experimental data or design data according to various engine operating conditions, and is stored in the ROM of the ECU 28 saved. Thereby, the target valve timing may be changed at almost the same time as the accelerator position changes, as indicated by a solid line in FIG 2 is shown.

The valve timing is executed to control the variable valve timing device 31 so that the actual valve timing (valve operating advance angle), which is determined by the outputs of the crank angle sensor 27 and a camshaft angle sensor (not shown) to which target valve timing is controlled. In this control, since the variable valve timing device 31 is hydraulically driven, it has a response delay of the hydraulic control system from the timing of change of the target valve timing to the timing of actually changing the valve timing as indicated by a dotted line in FIG 2 is shown.

At time t2, which is after a throttle delay time Td from a time point t1 of the quick torque change request, a target throttle opening position (throttle position) as indicated by a solid line in FIG 2 is calculated in accordance with the accelerator position. The throttle control is executed to the engine 15 the electronic throttle device 33 so that the actual throttle position is controlled to the target throttle position.

Since the target valve timing is set based on the estimated load (estimated intake air amount or estimated intake air pressure) corresponding to the accelerator position and independent of the throttle position, the target valve timing is changed almost at the same time as the accelerator position is changed. As a result, the target valve timing is changed in advance of the actual change in the throttle position, which changes with a delay from the change of the accelerator position. Therefore, it becomes possible to change the actual valve timing that changes with a delay from the target valve timing, such as a dotted line in FIG 2 is shown, and the actual load (actual intake air amount or actual intake air pressure), which is in accordance with by a dotted line in 2 actual throttle position changes, synchronize or change almost at the same time.

In this embodiment, the throttle delay time Td from the change of the accelerator position to the actual change of the throttle position at the time of changing the accelerator position is almost the same as the delay time Vd of the valve timing from the change of the target valve time (change of the accelerator position) to the Actual change in valve time. Therefore, the actual valve timing, which changes in response to the target valve time, is substantially synchronized to the actual load, which changes in response to the actual throttle position.

Specifically, the throttle delay time Td is determined by using a data map in accordance with at least one of the sizes of coolant temperature, engine temperature, hydraulic fluid temperature of the variable valve timing device 31 , Engine speed and throttle position change amount. The throttle delay time Td becomes almost equal to the delay time Vd of the actual valve timing set by varying the throttle delay time Td.

The valve time delay time Vd changes with the fluid temperature (viscosity). Further, since a fluid pump (not shown) that supplies a fluid pressure by the internal combustion engine 11 is driven, the fluid pressure changes with the engine speed and in response, the valve timing delay changes. In addition, since the valve time change amount changes with the throttle position change amount, the delay time Vd of the valve timing changes accordingly. Therefore, by varying the throttle position delay time Td in accordance with the fluid temperature (or an alternative parameter such as coolant temperature, engine temperature), engine speed or the throttle position change amount, the throttle delay time Td and the valve time delay time Vd are almost equalized.

Thereby, by substantially equalizing the delay time Td of the throttle operation and the delay time Vd of the variable valve timing, the actual valve timing that changes in response to the target valve timing and the actual load that changes in response to the actual throttle position become Essentially synchronized. Thereby, for more desirable combustion at substantially the same time as the actual load changing with the actual throttle position, the actual valve timing may be changed. Consequently, the deterioration of the combustion situation caused by the reaction delay of the variable valve timing device 31 is caused in the transient state of the internal combustion engine 11 be reduced.

The foregoing transition timing is executed by executing an in 3 transitional program through the ECU 28 , This transitional timing program is executed every predetermined interval as long as the ECU 28 is supplied with electrical energy.

When execution of this control program is started, it is first checked in step 101 whether an accelerator position is changed to request a rapid torque change. If no accelerator position change is made, execution of this program is terminated. If the accelerator position is changed to request the rapid torque change, in step 102 by using a data map or a mathematical calculation based on the accelerator position and a target valve time at that time, a load (intake air amount or intake air pressure) is estimated.

Then in step 103 calculate a new target valve timing in accordance with the estimated load, an engine speed, and the like by referring to a data map of the target valve time. This map of the target valve timing sets optimum valve timing corresponding to various engine operating conditions determined by experimental data or design data, and is stored in the ROM of the ECU 28 saved. Then, in step 104, the valve timing is executed to control the variable valve timing device 31 so as to control the actual valve timing to the calculated target valve timing.

In step 105 For example, a throttle delay time Td is calculated by, for example, a data map in accordance with one or more quantities of the engine coolant temperature, engine temperature, fluid temperature, engine speed, and throttle position change amount. By varying the throttle delay time Td, the throttle delay time Td is made substantially equal to the valve time delay time Vd.

Then in step 106 checks whether the throttle delay time Td has elapsed from the time of the accelerator position change requesting a torque change. If the throttle delay time Td has elapsed, the target throttle position is calculated in accordance with the accelerator position. A throttle control is in step 107 executed to the engine 15 of the electronic throttle device 33 to control such that the actual throttle position is controlled to the target throttle angle out. Thereby, the throttle delay time Td from the change of the throttle position to the actual change of the throttle position at the time of change of the accelerator position is controlled to be almost equal to the delay time Vd of the valve timing from the change of the target valve time (change of the accelerator position) to the actual change of the valve timing be. Thereby, the actual valve timing, which changes in response to the target valve timing, is substantially synchronized to the actual load, which changes with the actual throttle position.

Then in step 108 the actual load (actual intake air amount or actual intake air pressure) is estimated or calculated by using a data map or mathematical equations based on the actual throttle position and the actual valve time. This calculated actual load may be used in a fuel injection control program or an ignition control program to determine an amount of fuel to be injected from the fuel injection device 21 or a spark discharge timing of the spark plug, respectively 22 to calculate.

According to the previous embodiment, as in 2 13, the target valve timing is set in the transitional time state based on the estimated load corresponding to the accelerator position at the time of the accelerator position change requesting the torque change, and the target valve timing is changed almost at the same time as the accelerator position change. Consequently, the target valve time (solid line in FIG 2 ) before the actual change of throttle position (dotted line in 2 ) which shifts relative to the accelerator position change. The throttle delay time Td is set by varying the throttle delay time Td to be almost the same as the delay time Vd of the actual valve timing. By the synchronization of the load change and the actual valve timing change, the deterioration of the combustion state caused by the response delay of the variable valve timing device 31 can be reduced and the uncomfortable torque variation is also reduced.

Further, it is not necessary to suppress the time delay Vd of the actual valve timing relative to the target valve time. Consequently, the amount of change of the target valve time need not be limited. Further, the target valve timing can be set to an optimum value, so that the fuel economy is improved.

The valve timing delay Vd from the change of the target valve timing to the change of the actual valve timing changes with the driving state (fluid temperature or fluid pressure) of the variable valve timing apparatus 31 , Therefore, it is difficult to set the time delay arbitrarily. However, the throttle delay time Td may be arbitrarily set from the change of the accelerator position to the change of the throttle position. Based on this point, the throttle delay time Td is varied so as to become substantially equal to the delay time Vd of the valve timing. Therefore, by simply varying the throttle delay time Td, the throttle delay time Td may be substantially equal to the delay time Vd of the valve timing apparatus 31 be made.

In addition, the load is estimated in accordance with the accelerator position and the target valve time when the accelerator position is changed to request the torque change. Consequently, the load can be estimated with high accuracy in accordance with the accelerator position and the target valve timing before the throttle position and the actual valve timing change.

In the foregoing embodiment, the actual load and the actual valve timing are substantially synchronized by controlling the actual throttle position and the actual valve timing to change at almost the same time. However, if the delay of the change of the actual load relative to the change of the actual throttle position is comparatively large, the valve timing may be controlled to change in advance to the actual change of the throttle position so that the actual load will be at almost the same time the actual valve time changes. Further, it is possible the variable valve timing device 31 at the same time as or earlier than an intake air control device (eg, idle speed control device, exhaust gas recirculation device, etc.) other than the electronic throttle device 33 to act for better combustion when the torque change is requested. In addition to or instead of the variable valve timing device 31 on the inlet side, the variable valve timing device 32 be controlled on the exhaust side in a similar manner as the previous embodiment.

In a transient state in which an accelerator position is changed to change an engine output torque, an engine load is estimated 102 in accordance with an accelerator position, and an intake valve target valve timing is set based on the estimated load 103. Therefore, the target valve timing becomes previous to the actual one Change in throttle position changed 104, which changes with a delay relative to the accelerator position. A throttle delay time Td from the accelerator position change to the actual valve timing change is made substantially equal to a delay time Vd that is from the target valve timing change to the actual valve timing change. As a result, the actual load change and the actual valve timing change are almost synchronized with each other.

Claims (3)

An engine control system including a variable valve timing apparatus (31, 32) for variably controlling a valve timing of at least one of an intake valve (29) and an exhaust valve (30) of an internal combustion engine (11); and an intake air control device (33) for controlling an intake air amount, wherein a control unit (28) having transitional control means (101-103, 105, 106) for controlling the variable valve timing apparatus is provided to change an operation time therefrom at the same time or prior to a change of operation of the intake air control apparatus when generating a torque change request is to request a torque change of the internal combustion engine, thereby to improve combustion of the internal combustion engine; the intake air control device (33) is an electronic throttle device that controls a throttle valve (16) of the internal combustion engine by an electric actuator (15); the control unit (28) further includes throttle control means (107) for controlling the electronic throttle device to change a throttle position with a throttle delay time (Td) with respect to a change in accelerator position, and valve timing control means (104) for controlling the variable valve timing device; such that an actual valve operating time coincides with a target valve time; and the transient control means (101-103, 105, 106) includes load estimation means (101, 102) for estimating a load based on the accelerator position when the torque change request is generated in response to an accelerator position change, setting means (103) for setting a target valve time based on the load estimated by the load estimator, and a synchronizer (105, 106) for synchronizing the actual valve time, which varies with the target valve time, and the actual load, which varies with the throttle position, characterized in that the synchronizer (105, 106) controls a valve time delay time (Vd), which is from a target valve time change to an actual valve time change, to be substantially equal to a throttle delay time thereby to synchronize the actual valve time change and the actual load change and the synchronizer (105, 106) varies the throttle delay time to be equal to the valve time delay time. Engine control system according to Claim 1 wherein the synchronizer (105, 106) varies the throttle delay time based on at least one of the engine temperature, fluid temperature, coolant temperature, speed, and throttle position change amount. Internal combustion engine control system according to one of Claims 1 or 2 wherein the load estimation means (101, 102) estimates the load based on the accelerator position and the target valve time when the accelerator position is changed.

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