JP2001065375A - Intake valve open timing control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure good operation of an engine even at cold time. SOLUTION: An electrically driven type intake valve open timing variable device 21 for changing the open timing of an intake valve is mounted in the intake valve 13 of an internal combustion engine 1 of hybrid system. When an engine cooling water temperature is lower than a preset temperature, the intake valve open timing is determined in accordance with the engine cooling water temperature, also the intake valve open timing, when the engine cooling water temperature is low, is advanced as compared with that when it is high. While when the engine cooling water temperature is high, the intake valve open timing, when the engine is in starting, is held to the most delay angle side, to reduce a vibration and noise of a vehicle. When the engine is after completion of starting, based on engine load and an engine speed, the intake valve open timing is calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake valve opening timing control device for an internal combustion engine.

[0002]

2. Description of the Related Art An intake valve opening timing variable device for changing the opening timing of an intake valve is provided, a basic intake valve opening timing is obtained, and a retard correction is made so that the opening timing increases as the engine cooling water temperature decreases. 2. Description of the Related Art An intake valve opening timing control device for an internal combustion engine which sets a value and corrects a basic intake valve opening timing with the retardation correction value is known (see Japanese Patent Application Laid-Open No. 6-346768). In this intake valve opening timing control device, the overlap period in which both the intake valve and the exhaust valve are open is reduced as the engine cooling water temperature decreases,
As a result, the amount of exhaust gas flowing back into the intake passage is reduced so that combustion is stabilized.

[0003]

By the way, as the retard correction value increases, that is, as the intake valve opening timing is retarded, the amount of intake air decreases, and therefore the engine output decreases. However, since the friction increases as the engine temperature decreases, if the intake valve opening timing is retarded as the engine cooling water temperature decreases as in the above-described intake valve opening timing control device, good engine operation is achieved. There is a problem that cannot be secured. This is particularly problematic during cold start of the engine.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an intake valve opening timing control device for an internal combustion engine that can ensure good engine operation when the engine is cold.

[0005]

According to the present invention, there is provided an electric-drive-type variable intake valve opening timing device for changing the opening timing of an intake valve. When the pressure is low, the opening timing of the intake valve is advanced compared to when the pressure is high. That is, a large amount of intake air is ensured during a cold period when friction is large, so that good engine operation is ensured.

[0006]

FIG. 1 shows a case in which the present invention is applied to an internal combustion engine for a hybrid system having an internal combustion engine and an electric motor. However, the present invention can be applied to other internal combustion engines. Referring to FIG. 1, an internal combustion engine main body 1 is connected to an input side of a power split device 2. The output side of the power split device 2 is connected on the one hand to the axle 4 of the vehicle via the speed reducer 3 and on the other hand to the generator 5. Generator 5 is electrically connected to storage battery 7 via inverter 6. The storage battery 7 is electrically connected to an electric motor 8 via an inverter 6, and the electric motor 8 is connected to an axle 4 of the vehicle via a speed reducer 3.

FIG. 2 shows the engine body 1 in detail. Referring to FIG. 2, 10 is a piston, 11 is a combustion chamber, 12
Is an intake port, 13 is an intake valve, 14 is an exhaust port, 15
Denotes an exhaust valve, and 16 denotes an ignition plug. The intake port 12 is connected to a surge tank 18 via a corresponding intake branch 17, and the surge tank 18 is connected to an air cleaner 20 via an intake duct 19. A fuel injection valve 21 is arranged in the intake branch 17, and a throttle valve 23 driven by an electromagnetic actuator 22 is arranged in the intake duct 19. On the other hand, the exhaust port 14 is connected to the exhaust manifold 2.
4 and a catalyst converter 26 via an exhaust pipe 25.

The intake valve 13 is provided with an electrically driven intake valve opening timing variable device 27 for controlling the valve opening timing. An example of the variable intake valve opening timing device 27 will be described briefly. A movable piston movable in the axial direction of the camshaft is arranged between a camshaft for driving the intake valve 13 and a pulley, The outer peripheral surface of the shaft and the inner peripheral surface of the movable piston are connected by a helical spline, and the outer peripheral surface of the movable piston and the inner peripheral surface of the pulley are also connected by a helical spline. On the other hand, the output shaft of the step motor is arranged concentrically with the rotation axis of the camshaft, and a rotating member that rotates integrally is attached to the output shaft. A worm gear is formed between the rotating member and the movable piston, so that when the angular position of the rotating member is changed by driving the stepping motor, the phase of the cam is changed because the movable piston is displaced in the axial direction. ,
Thus, the valve opening timing of the intake valve 13 is changed. In this embodiment, since the intake valve opening timing variable device 27 is of an electric drive type, the opening timing of the intake valve 13 can be changed at any time regardless of, for example, the vehicle running state or the engine operating state.

An electronic control unit (ECU) 30 is composed of a digital computer, and is connected to a ROM (Read Only Memory) 32, R
AM (random access memory) 33, CPU (microprocessor) 34, BR constantly connected to power supply
An AM (backup RAM) 35, an input port 36, and an output port 37 are provided. A water temperature sensor 38 for detecting an engine cooling water temperature THW indicating the engine temperature is attached to the engine body 1, and the water temperature sensor 38 generates an output voltage indicating the engine cooling water temperature THW. Throttle valve 2
An intake air amount sensor 39 for detecting an intake air mass flow rate Ga is arranged in the intake duct 19 upstream of the third, and this intake air amount sensor 39 generates an output voltage indicating the intake air mass flow rate Ga. A depression amount sensor 40 for detecting the depression amount DEP of the accelerator pedal is arranged on an accelerator pedal (not shown), and the depression amount sensor 40 generates an output voltage indicating the depression amount DEP. A charge amount sensor 41 for detecting the charge amount VBAT is attached to the storage battery 7 (FIG. 1), and the charge amount sensor 41 generates an output voltage indicating the charge amount VBAT. The output voltages of these sensors 38, 39, 40, 41 are input to the input port 3 via the corresponding AD converter 42.
6 is input. Further, the input port 36 has a rotation speed sensor 43a for generating an output pulse representing the engine rotation speed N.
And a vehicle speed sensor 43b for generating an output pulse representing the vehicle speed
Are connected. The CPU 34 calculates the required vehicle driving force from the depression amount of the accelerator pedal and the vehicle speed. On the other hand, the output port 37 is connected to the ignition plug 16, the fuel injection valve 21, the actuator 22, and the step motor of the intake valve opening timing variable device 27 via the corresponding drive circuit 44.

In the hybrid system shown in FIG. 1, the operation / stop of the engine 1 is repeatedly performed according to various conditions. First, an operation / stop control method of the engine 1 will be described with reference to an operation flag control routine shown in FIG. This routine is executed by interruption every predetermined set time. The operation flag is set when the engine 1 is to be operated, and is reset when the engine 1 is to be stopped.

Referring to FIG. 3, first, step 5
In the case of 0, the required vehicle driving force PV is a predetermined set amount P1.
It is determined whether the number is smaller than the number. When PV <P1, the routine proceeds to step 51, where it is determined whether or not the engine cooling water temperature THW is higher than a predetermined first set temperature T1 (for example, 65 ° C.). When THW> T1, the routine proceeds to step 52, where it is determined whether the charged amount VBAT of the storage battery 7 is larger than a predetermined set amount V1. When VBAT> V1, the routine proceeds to step 53, where the operation flag is reset. That is, the engine is stopped.

On the other hand, when PV ≧ P1 in step 50, the process proceeds to step 54, where it is determined whether the accelerator pedal depression amount DEP is 0, that is, whether the vehicle is in a deceleration operation. When DEP = 0, the routine proceeds to step 51. On the other hand, when DEP> 0, the routine proceeds to step 55. In step 51, T
When HW ≦ T1, or in step 52, VBAT
When ≤V1, the routine also proceeds to step 55, where the operation flag is set. That is, the engine 1 is operated.

Therefore, generally speaking, when the required vehicle driving force is low, the engine 1 is stopped, and when the required vehicle driving force is high, the engine 1 is operated. However, the engine cooling water temperature TH
When W is low or the charge amount is small, engine operation is performed to increase the engine cooling water temperature THW or increase the charge amount. As a result, the operation / stop of the engine 1 is frequently repeated.

By the way, if the most retarded intake valve opening timing which can be controlled by the intake valve opening timing variable device 27 is referred to as a reference opening timing, the intake valve opening timing is advanced from the reference opening timing. It can be specified by quantity. Therefore, in the following, description will be made using the advance angle ADV. During normal operation of the engine 1, the advance angle ADV is calculated based on the engine operating state, for example, the intake air amount Ga and the engine speed N.
E. The ADVE is, for example, an advance amount required to optimize the intake air amount and the overlap amount, and is obtained in advance by an experiment. The advance angle ADVE is stored in advance in the ROM 32 in the form of a map shown in FIG. 4 as a function of the intake air amount Ga and the engine speed N.

On the other hand, when the operation flag is switched from set to reset, that is, when the engine 1 is to be stopped, the advance angle ADV is returned to zero, and is maintained at zero while the engine is stopped. By doing so, for example, safety when the intake valve opening timing variable device 27 breaks down can be enhanced. Next, when the operation flag is switched from reset to set, that is, when the engine operation is to be started, the advance amount ADV is held at zero for a predetermined period of time, and then the above-mentioned ADVE is set when a predetermined period of time has elapsed. You. The reason why the advance amount ADV is held at zero when the engine is started is as follows. That is, when the advance angle ADV is large when the engine is started, the generated torque of the engine 1 sharply increases, thus increasing the vehicle vibration and noise. Therefore, the advance angle ADV
Is set to zero, that is, if the intake valve opening timing is set to the most retarded side, vehicle vibration and noise can be reduced.

However, as described at the beginning, the advance angle AD
As V becomes smaller, the amount of intake air decreases, and accordingly, the torque generated by engine 1 decreases. However, since the friction increases as the engine temperature decreases, a large generated torque is required for starting the engine. As a result, when the advance angle ADV is small when the engine 1 is to be started when the engine temperature is low, the engine start becomes difficult, and in some cases, the engine 1 may not be started. Further, even during the operation of the engine, if the advance amount ADV determined according to the engine operation state becomes small when the engine temperature is low, it may be difficult to continue the engine operation.

Therefore, in this embodiment, the engine cooling water temperature TH
W is a predetermined second set temperature T2 (for example, 60
° C), the advance angle ADV is determined according to the engine coolant temperature THW, and at this time, the engine coolant temperature T
When the HW is low, it is larger than when it is high. As the advance angle ADV increases, the intake air amount increases, and the engine generated torque increases. Therefore, a necessary engine generated torque can be secured according to the engine temperature. Therefore, good engine start or engine operation can be ensured even in the cold state.

In other words, when THW <T2, the advance amount ADV becomes equal to the engine cooling water temperature THW as shown in FIG.
Is low, the ADVT becomes larger than when it is high. This ADVT is obtained in advance by an experiment, and is stored in the ROM 32 in advance in the form of a map shown in FIG. 5 as a function of the engine cooling water temperature THW. If the advance amount ADV is held at zero when the engine is started, it can be seen that the control of the advance amount ADV is stopped when the engine is started. In this embodiment, when the engine temperature is low, the engine 1 is started and, at the same time, the control of the advance angle ADV is started. Therefore, the advance amount ADV
Can be optimally maintained.

On the other hand, when THW ≧ T2, if the engine is started, the advance angle ADV is held at zero to reduce the vibration and noise of the vehicle. If the engine start is completed, the above-mentioned ADVE is set as the advance angle ADV. The second set temperature T2 is set to be lower than the above-mentioned first set temperature T1. FIG. 6 shows a routine for calculating the advance angle ADV according to this embodiment. This routine is executed by interruption every predetermined set time.

Referring to FIG. 6, first, step 6
If it is 0, it is determined whether or not the operation flag (FIG. 3) is set. When the operation flag is reset, that is, when the engine operation is to be stopped, the routine proceeds to step 61, where the advance angle ADV is set to zero. On the other hand, when the operation flag is set, that is, when engine operation is to be performed, the routine proceeds to step 62, where the engine cooling water temperature TH
It is determined whether W is lower than second set temperature T2. When THW <T2, the process then proceeds to step 63, where ADVT is calculated from the map of FIG. In the following step 64, this ADVT is set as the advance amount ADV. On the other hand, when THW ≧ T2, the routine proceeds to step 65, where it is determined whether or not the engine is currently being started. When the engine is currently being started, the routine proceeds to step 61, where the advance amount ADV is held at zero. If the engine is not currently being started, then the routine proceeds to step 66, where A is obtained from the map of FIG.
DVE is calculated. In the following step 67, this ADV
E is the advance angle ADV. Intake valve opening timing variable device 2
Reference numeral 7 controls the position of the movable piston so that the actual advance amount becomes this ADV.

In the above embodiment, the engine temperature is represented by the engine cooling water temperature. However, the engine temperature can be represented by, for example, the intake air temperature, the cylinder temperature, the temperature of the engine body itself, the temperature of exhaust system components such as exhaust pipes and catalysts, the temperature of exhaust gas, or the temperature of engine oil.

[0022]

According to the present invention, good engine operation can be ensured when the engine is cold.

[Brief description of the drawings]

FIG. 1 is an overall view of a hybrid system.

FIG. 2 is an overall view of an internal combustion engine.

FIG. 3 is a flowchart illustrating a control routine of an operation flag.

FIG. 4 is a diagram showing an advance angle ADVE based on engine operating conditions.

FIG. 5 is a diagram showing an advance angle ADVT based on an engine cooling water temperature.

FIG. 6 is a flowchart showing a routine for calculating an advance amount ADV.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine body 13 ... Intake valve 27 ... Intake valve opening timing variable device 38 ... Water temperature sensor

Continued on front page F term (reference) 3G092 AA01 AA06 AA11 AC02 AC03 DA01 DA09 DG08 EA03 EA08 EA13 EA17 EA22 EC09 FA03 FA14 GA01 GA02 HA01Z HE01Z HE08Z HF02Z HF08Z HF21Z

Claims (1)

[Claims] 1. An electronically driven intake valve opening timing variable device for changing the opening timing of an intake valve, wherein the opening timing of the intake valve is advanced when the engine temperature is low as compared with when the engine temperature is high. An intake valve opening timing control device for an internal combustion engine.