JP7559615B2 - Control device for internal combustion engine - Google Patents

Description

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

Known control devices for internal combustion engines that control the opening and closing timing of the intake valve or exhaust valve include those that improve the starting performance of the internal combustion engine as described in Patent Document 1 and Patent Document 2, and those that reduce the amount of intake air in the combustion chamber when the internal combustion engine is stopped as described in Patent Document 3.

Patent document 1 describes a variable valve timing mechanism that changes the timing of opening and closing the intake and exhaust valves, and by accelerating the timing of opening and closing the intake and exhaust valves when motoring in a cold state, it is possible to increase the compression ratio and increase the temperature in the combustion chamber due to the heat of compression.

Patent Document 2 also describes setting the intake valve opening and closing timing to the advanced side during cold start (motoring).

Furthermore, in Patent Document 3, by setting the intake valve to an ultra-retard angle, the problem of fresh air flowing from the exhaust system to the catalyst when the internal combustion engine is stopped, which leads to a drop in catalyst temperature and a worsening of fuel economy due to an increase in fuel consumption when the engine is restarted, is improved.

JP 2009-299538 A WO2020/022062A1 publication WO2019/244675A1 publication

As described in Patent Documents 1 and 2, in a four-stroke internal combustion engine, it is possible to increase the compression ratio and raise the temperature in the combustion chamber by shifting the opening and closing timing of the intake valve in the advance direction during cold start. However, it was conceivable that simply shifting the opening and closing timing of the intake valve in the advance direction would result in a shortage of heat, since compression occurs during only one of the two rotations of the crankshaft due to motoring.

Also, as described in Patent Document 3, when the engine is set to an ultra-retarded angle, there is little intake air, making it impossible to start the internal combustion engine.

When considering cold starting, there is concern that simply setting the intake valve opening and closing timing as described in Patent Documents 1 to 3 may not be enough to ensure smooth starting.

For these reasons, there is a demand for an internal combustion engine control device that can perform a good cold start.

The characteristic configuration of the control device for an internal combustion engine according to the present invention is a rotor on an exhaust drive side that rotates synchronously with a crankshaft of the internal combustion engine,
an exhaust driven rotor that rotates together with an exhaust camshaft to open and close an exhaust valve of a combustion chamber of the internal combustion engine and is disposed coaxially with a rotation axis of the exhaust driving rotor;
an exhaust-side valve timing control mechanism including an exhaust-side actuator that sets an exhaust-side relative rotation phase between the exhaust driving-side rotor and the exhaust driven-side rotor,
the exhaust-side valve timing control mechanism is configured to be capable of switching between a normal exhaust timing that constantly keeps the exhaust valve open while the piston of a predetermined cylinder of the internal combustion engine moves from the bottom dead center to the top dead center, and a limited exhaust timing that is more advanced than the normal exhaust timing so as to transition the exhaust valve to a closed state before the piston reaches the top dead center,
a control unit that switches between the normal exhaust timing and the limited exhaust timing by controlling the exhaust side actuator ,
an intake drive-side rotor that rotates synchronously with the crankshaft of the internal combustion engine;
an intake driven rotor that rotates integrally with an intake camshaft to open and close an intake valve of a combustion chamber of the internal combustion engine and is disposed coaxially with a rotation axis of the intake driving rotor;
an intake side actuator that sets an intake side relative rotation phase between the intake driving side rotor and the intake driven side rotor,
the intake-side valve timing control mechanism is configured to be capable of switching between a normal intake timing for opening the intake valve before the piston reaches the top dead center or simultaneously with the piston reaching the top dead center when a predetermined cylinder of the internal combustion engine is in an exhaust stroke, and a limited intake timing that is retarded from the normal intake timing and opens the intake valve after the piston reaches the top dead center,
the control unit sets the intake-side valve timing control mechanism to the limited intake timing in coordination with a control for setting the exhaust-side valve timing control mechanism to the limited exhaust timing,
When the bottom dead center is defined as BDC, the top dead center is defined as TDC, the timing at which the exhaust valve opens is defined as EVO, the timing at which the intake valve opens is defined as IVO, the timing at which the intake valve closes is defined as IVC, the timing at which the exhaust valve closes is defined as EVC, the timing before BDC is defined as BBDC, and the timing after BDC is defined as ABDC,
At the limited exhaust timing, the EVO is on the retard side of the TDC and the EVC is on the advance side of the TDC,
A relationship between a first angle θ1 from the BDC to the EVO at the BBDC and a second angle θ2 from the BDC to the EVC at the ABDC is θ1≧θ2, and
At the limited intake timing, the IVO is on the retard side of the TDC, the IVC is on the advance side of the TDC, and the IVC is greater than 90 degrees at the ABDC with respect to the BDC;
The relationship between a third angle θ3 from the BDC to the IVO at the BBDC and a fourth angle θ4 from the BDC to the IVC at the ABDC is such that θ3≧θ4 .

According to this characteristic configuration, the control unit controls the drive of the exhaust actuator, so that the exhaust valve timing control mechanism can switch between opening and closing the exhaust valve at normal exhaust timing and opening and closing the exhaust valve at timing corresponding to limited exhaust timing, which is more advanced than the normal exhaust timing. In normal exhaust timing, the exhaust valve is kept open until the piston reaches top dead center during the exhaust stroke, so all gas in the combustion chamber is discharged, allowing the engine to operate normally. In contrast, in limited exhaust timing, the exhaust valve is closed before the piston reaches top dead center, so the gas in the combustion chamber is compressed and the temperature of the gas in the combustion chamber is increased. In this limited exhaust timing, the discharge of gas from the combustion chamber to the exhaust side is suppressed, increasing the load acting on the crankshaft and facilitating the stopping of the internal combustion engine.

In particular, when the internal combustion engine is cold and the exhaust-side valve timing control mechanism is set to limited exhaust timing and motoring is performed, the crankshaft rotates twice in one cycle, compressing the gas in the combustion chamber twice, efficiently raising the temperature of the gas in the combustion chamber and making it easier to ignite the mixture in the combustion chamber.
Thus, a control device for an internal combustion engine capable of performing a good cold start has been configured.

In addition, according to this, the control unit controls the drive of the intake side actuator, so that the intake side valve timing control mechanism can switch between a state in which the intake valve is opened and closed at a timing corresponding to the normal intake timing and a state in which the intake valve is opened and closed at a timing corresponding to the limited intake timing, which is more advanced than the normal intake timing. In addition, in the normal intake timing, the intake valve is maintained in an open state when the piston starts to descend from the top dead center in the intake stroke, and gas (air) on the intake side can be sucked into the combustion chamber, enabling normal operation of the engine. In contrast, in the limited intake timing, the intake valve is closed when the piston is at the top dead center of the intake stroke, and then the intake valve opens after the piston starts to descend. As a result, by setting the intake side valve timing control mechanism to the limited intake timing in conjunction with the control for setting the exhaust side valve timing control mechanism to the limited exhaust timing, it is possible to completely seal gas in the combustion chamber when the piston moves toward the top dead center in the exhaust stroke, and to reliably increase the temperature by compressing the gas.

According to this , in normal exhaust timing in the exhaust-side valve timing control mechanism, for example, assuming that EVC coincides with TDC and EVO is closer to BBDC than BDC, when the exhaust-side valve timing control mechanism is set to limited exhaust timing, the relative rotation phase is displaced in the advance direction until the relationship of first angle θ1 ≧ second angle θ2 is established, and when the piston moves toward TDC (top dead center) in the exhaust stroke, it becomes possible to keep the exhaust valve closed before the piston reaches top dead center TDC. As a result, when set to limited exhaust timing, the exhaust valve can be set to EVC to compress gas in the combustion chamber before the piston reaches top dead center TDC in the exhaust stroke.

According to this , assuming that, for example, IVO is located on the advanced side of TDC and IVC is located on the ABDC side of BDC in normal intake timing in the intake-side valve timing control mechanism, when the intake-side valve timing control mechanism is set to the restricted intake timing, IVO is displaced in the retarded direction until the intake valve is closed at ABDC, and IVC becomes greater than 90 degrees at ABDC with respect to BDC, and the relationship of the third angle θ3≧the fourth angle θ4 is established. As a result, when the exhaust-side valve timing control mechanism is set to the restricted exhaust timing, gas is sealed in the combustion chamber until the piston passes TDC (top dead center) during the exhaust stroke, and the inconvenience of gas in the combustion chamber flowing to the intake side can be suppressed.

As an additional configuration to the above, a temperature sensor may be provided to measure the temperature of the internal combustion engine, and when the control unit starts the internal combustion engine in a situation where the temperature detected by the temperature sensor is less than a set value, the control unit may set the exhaust side valve timing control mechanism to the limited exhaust timing and start motoring to rotate the crankshaft, and then supply fuel to the combustion chamber and perform ignition.

According to this, when the temperature sensor detects that the temperature of the internal combustion engine is below a set value, motoring is started with the exhaust side valve opening/closing timing control mechanism set to limited exhaust timing, and during motoring, the gas in the combustion chamber is compressed as the piston rises during the exhaust stroke, raising the temperature of the combustion chamber, and fuel is supplied and ignited in this elevated temperature state, making it possible to perform a cold start.
In particular, when starting the internal combustion engine in this manner, by setting the intake side valve opening/closing timing control mechanism to the limited intake timing, it is possible to reliably compress the combustion gas while suppressing the inconvenience of gas in the combustion chamber flowing to the intake side, thereby enabling the temperature in the combustion chamber to be raised.

In addition to the above configuration, when the internal combustion engine is stopped, the control unit may stop the fuel supply to the combustion chamber with the exhaust valve timing control mechanism set to the limited exhaust timing.

According to this, when stopping an internal combustion engine in an operating state, by setting the exhaust side valve timing control mechanism to the limited exhaust timing, the load when the piston moves toward top dead center is increased, enabling the engine to be stopped quickly.
In particular, when stopping the internal combustion engine in this manner, by setting the intake side valve opening/closing timing control mechanism to the limited intake timing, the inconvenience of gas in the combustion chamber flowing to the intake side is suppressed, thereby achieving an even quicker stopping of the engine.

FIG. 2 is a diagram showing a cross section of an engine and a control unit. FIG. 2 is a cross-sectional view of a valve timing control mechanism. 3 is a cross-sectional view taken along line III-III in FIG. 2. 4 is a timing diagram of the variable valve mechanism when the engine is running. 4 is a timing chart of the intake valve and exhaust valve when the engine is running. 4 is a timing diagram of the variable valve mechanism during cold start. 4 is a timing chart of the intake valve and exhaust valve during cold start. 4 is a flowchart of a control mode of a variable valve mechanism. 4 is a flowchart of cold start control. 4 is a flowchart of a stop control.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[Basic configuration]
As shown in FIG. 1, an engine E as an internal combustion engine has an intake valve Va and an exhaust valve Vb, an intake side variable valve mechanism VTa (an example of an intake side valve timing control mechanism) that sets the valve timing (opening and closing timing) of the intake valve Va, and an exhaust side variable valve mechanism VTb (an example of an exhaust side valve timing control mechanism) that sets the valve timing (opening and closing timing) of the exhaust valve Vb, and an engine control device 40 (an example of a control device for an internal combustion engine) that controls the starting and stopping of the engine E and controls the intake side variable valve mechanism VTa and the exhaust side variable valve mechanism VTb.

Engine E (an example of an internal combustion engine) is provided in a vehicle to provide driving force for a passenger car or the like. In particular, the engine control device 40 controls the valve timing of the intake valve Va and the valve timing of the exhaust valve Vb when engine E is started and stopped, thereby enabling good starting even when the engine is cold and realizing good stopping of engine E. These control forms will be described later.

〔engine〕
As shown in Figures 1 and 2, engine E is a four-stroke engine having a cylinder head 3 connected to the upper part of a cylinder block 2 which rotatably supports a crankshaft 1, pistons 4 which are housed in a plurality of cylinder bores formed in the cylinder block 2 and can reciprocate freely, and the pistons 4 are connected to the crankshaft 1 by connecting rods 5.

The cylinder head 3 is equipped with an intake valve Va and an exhaust valve Vb, and an intake camshaft 7 that controls the intake valve Va and an exhaust camshaft 8 that controls the exhaust valve Vb are provided at the top of the cylinder head 3. A timing belt 6 is wound around the output pulley 1S of the crankshaft 1 and the drive pulleys 21S of the intake variable valve mechanism VTa and the exhaust variable valve mechanism VTb.

The cylinder head 3 is equipped with an injector 9 that injects fuel into the combustion chamber and a spark plug 10. Connected to the cylinder head 3 are an intake manifold 11 that supplies air to the combustion chamber via an intake valve Va, and an exhaust manifold 12 that sends out the combustion gas in the combustion chamber via an exhaust valve Vb. In addition, the cylinder head 3 is equipped with a catalyst 13 that purifies the exhaust gas from the exhaust manifold 12. The engine E is equipped with a starter motor 15 that drives and rotates the crankshaft 1 when the engine is started.

[Variable valve mechanism]
The intake side variable valve mechanism VTa (intake side valve timing control mechanism) and the exhaust side variable valve mechanism VTb (exhaust side valve timing control mechanism) as the variable valve mechanism VT have a common configuration, so in Figures 1 to 3, the common symbols are used for the common configuration, and symbols that enable distinction are used for parts that need to be distinguished.

The variable valve mechanism VT has a drive case 21 (an example of an intake driving rotor/exhaust driving rotor) and an internal rotor 22 (an example of an intake driven rotor/exhaust driven rotor) arranged coaxially with the rotation axis X of a camshaft (either the intake camshaft 7 or the exhaust camshaft 8, whichever corresponds), and is equipped with a phase adjustment mechanism G that adjusts the relative rotational phase between them using the driving force of a phase control motor M (a superordinate concept of the intake phase control motor Ma and the exhaust phase control motor Mb) as an actuator.

The drive case 21 has a drive pulley 21S formed on its outer periphery. The internal rotor 22 is contained within the drive case 21 and is connected and fixed to the camshaft by a connecting bolt 23. With this configuration, the drive case 21 is supported on the outer periphery of the internal rotor 22 so that it can rotate relatively freely, and the internal rotor 22 rotates integrally with the corresponding camshaft (intake camshaft 7 or exhaust camshaft 8).

The front plate 24 is fastened by multiple fastening bolts 25 in a position that covers the opening of the drive case 21. This allows the front plate 24 to restrict the displacement of the phase adjustment mechanism G and the internal rotor 22 in the direction along the rotation axis X.

As shown in Figures 1 and 3, the variable valve mechanism VT rotates as a whole in the drive rotation direction S due to the drive force from the timing belt 6. In addition, the drive force of the phase control motor M is transmitted to the internal rotor 22 via the phase adjustment mechanism G, displacing the relative rotation phase of the internal rotor 22 with respect to the drive case 21. Of this displacement, the direction of displacement in the same direction as the drive rotation direction S is called the advance direction Sa, and the opposite direction is called the retard direction Sb.

[Variable valve mechanism: Phase adjustment mechanism]
2 and 3, the phase adjustment mechanism G includes a ring gear 26 formed coaxially with the rotation axis X on the inner periphery of the inner rotor 22, an inner gear 27 rotatably arranged coaxially with the eccentric axis Y on the inner periphery side of the inner rotor 22, an eccentric cam body 28 arranged on the inner periphery side of the inner gear 27, the front plate 24, and a joint portion J. The eccentric axis Y is formed in a position parallel to the rotation axis X.

The ring gear 26 has multiple internal teeth 26T, and the inner gear 27 has multiple external teeth 27T. As described above, the inner gear 27 is arranged coaxially with the eccentric axis Y of the internal rotor 22, so that a portion of the external teeth 27T meshes with the internal teeth 26T of the ring gear 26. This phase adjustment mechanism G is configured as an internal planetary gear reducer in which the number of teeth of the external teeth 27T of the inner gear 27 is one less than the number of teeth of the internal teeth 26T of the ring gear 26.

The joint part J has a joint member 33 made by pressing a plate material, and is configured as an Oldham joint in which the outer periphery of this joint member 33 is engaged with the drive case 21, and the inner periphery of this joint member 33 is engaged with the engaging protrusion 27U of the inner gear 27. As a result, the joint part J realizes the operation of rotating the inner gear 27 and the drive case 21 together while maintaining an eccentric positional relationship of the inner gear 27 with respect to the drive case 21.

The eccentric cam body 28 is generally cylindrical, and a pair of engagement grooves 28B are formed on the inner circumference in a position parallel to the rotation axis X. The eccentric cam body 28 is supported by a first bearing 31 on the front plate 24 so that it rotates coaxially with the rotation axis X, and an eccentric cam surface 28A is formed on the outer circumference at the portion on the intake camshaft 7 side of this support position.

The eccentric cam surface 28A is formed in a circular shape (with a circular cross section) centered on the eccentric axis Y, which is parallel to the rotation axis X. The inner gear 27 is rotatably supported on this eccentric cam surface 28A via the second bearing 32. A spring body 29 is fitted into a recess formed in the eccentric cam surface 28A, and the biasing force of this spring body 29 is applied to the inner gear 27 via the second bearing 32. With this configuration, a part of the external teeth 27T of the inner gear 27 meshes with a part of the internal teeth 26T of the ring gear 26, and the meshing state is maintained by the biasing force of the spring body 29.

The phase control motor M is supported by the engine E, and an engagement pin 34 formed on the output shaft Ms is fitted into an engagement groove 28B on the inner circumference of the eccentric cam body 28. Although details are not shown, the phase control motor M is configured as a brushless type with a structure common to three-phase motors, by including a rotor having a permanent magnet, a stator having multiple field coils arranged in a position surrounding the rotor, and an output shaft Ms to which the rotation of the rotor is transmitted.

When the engine E is running, the variable valve mechanism VT maintains the relative rotational phase of the variable valve mechanism VT by driving and rotating the output shaft Ms in the drive rotation direction S at the same speed as the camshaft. In addition, when the relative rotational phase is shifted in the advance direction Sa, the rotational speed of the output shaft Ms is reduced, and when the relative rotational phase is shifted in the retard direction Sb, the rotational speed of the output shaft Ms is increased.

In other words, in the case where the engine E is stopped, when the eccentric cam body 28 rotates about the rotation axis X in accordance with the rotation of the output shaft Ms driven by the phase control motor M, the phase adjustment mechanism G rotates the inner gear 27 and the ring gear 26 relatively (rotates) by an angle corresponding to the difference in the number of teeth between the inner gear 27 and the ring gear 26 each time the inner gear 27 rotates (revolves) once about the rotation axis X, thereby achieving a large deceleration. As a result, by controlling the rotation speed of the phase control motor M, the drive case 21, which rotates integrally with the inner gear 27 via the joint J, and the camshaft, which is connected to the ring gear 26 by the connecting bolt 23, are rotated relative to each other, thereby achieving valve timing adjustment.

[Valve timing]
4 to 7 show diagrams and graphs of the intake timing of the intake valve Va controlled by the intake side variable valve mechanism VTa and the exhaust timing of the exhaust valve Vb controlled by the exhaust side variable valve mechanism VTb.

[Valve timing: during operation]
4 and 5 show the opening and closing timing (opening and closing time) when the intake valve Va is set to the normal intake timing and the exhaust side variable valve mechanism VTb is set to the normal exhaust timing while the engine E is running. When the engine E is running, the intake valve Va is set to the normal intake timing, so that the intake opening timing IVO is on the advanced side (advance direction Sa) of the top dead center TDC, and the intake closing timing IVC is on the retarded side (retard direction Sb) of the bottom dead center BDC.

In addition, by setting the exhaust valve Vb to normal exhaust timing, the exhaust close timing EVC coincides with top dead center TDC, and the exhaust open timing EVO is on the advanced side (advance direction Sa) of bottom dead center BDC. In particular, the exhaust valve Vb is always maintained in an open state while the piston 4 is moving from bottom dead center BDC to top dead center TDC.

In this normal intake timing, for example, when the rotation speed of engine E is increased, the intake side variable valve mechanism VTa is controlled to change the intake opening timing IVO in the advance direction Sa (counterclockwise in Figure 4) to increase the intake volume.

Figure 5 also shows a graph with the crank angle on the horizontal axis and the lift amount of the intake valve Va and exhaust valve Vb on the vertical axis (corresponding to normal intake timing and normal exhaust timing).

In particular, as shown in FIG. 5, the intake valve Va starts to open at the intake open timing IVO just before the exhaust valve Vb transitions to a closed state at the exhaust close timing EVC, creating an overlap region W where the exhaust valve Vb and the intake valve Va open simultaneously.

[Valve timing: cold start/shutdown]
6 and 7 show the intake timing of the intake valve Va and the exhaust timing of the exhaust valve Vb when the engine E is cold started or stopped. That is, Fig. 6 and Fig. 7 show the opening and closing timing (opening and closing time) when the intake side variable valve mechanism VTa is set to the limited intake timing and the exhaust side variable valve mechanism VTb is set to the limited exhaust timing. The limited exhaust timing is realized by setting the valve timing of the exhaust side variable valve mechanism VTb to the most advanced angle.

This valve timing is created by the control unit, either the start control unit 41 or the stop control unit 43, controlling the intake side variable valve mechanism VTa and the exhaust side variable valve mechanism VTb. In particular, to create the valve timing shown in Figures 6 and 7, the exhaust side variable valve mechanism VTb is configured so that the exhaust valve Vb closes (transitions to exhaust close timing EVC) before the piston 4 reaches top dead center TDC. Also, the intake side variable valve mechanism VTa is controlled so that the intake valve Va opens (transitions to intake open timing IVO) after the piston 4 reaches top dead center TDC.

To explain the valve timing shown in Figure 6 in more detail, in the case of limited exhaust timing, the exhaust opening timing EVO is more advanced than top dead center TDC. If the angle from bottom dead center BDC to the exhaust opening timing EVO at BBDC (Before Bottom Dead Center/Timing before BDC) is taken as the first angle θ1, the relationship with the second angle θ2 from bottom dead center BDC to the exhaust closing timing EVC at ABDC (After Bottom Dead Center/Timing after BDC) is θ1 ≧ θ2.

Similarly, in the case of limited intake timing, the intake open timing IVO is set to the retarded side of top dead center TDC, and the intake close timing IVC is set to be greater than 90 degrees at ABDC (Before Bottom Dead Center) with respect to bottom dead center BDC. Also, if the angle from bottom dead center BDC to the intake open timing IVO at BBDC is set as a third angle θ3, the relationship with the fourth angle θ4, which is the angle from bottom dead center BDC to the intake close timing IVC at ABDC (After Bottom Dead Center), is θ3 ≧ θ4.

Figure 7 shows a graph with the crank angle on the horizontal axis and the lift amount of the intake valve Va and the exhaust valve Vb on the vertical axis (corresponding to the intake restriction timing and the exhaust restriction timing).

As shown in the figure, as the crankshaft 1 rotates, the exhaust valve Vb begins to open at the exhaust open timing EVO and transitions to a closed state at the exhaust close timing EVC. In addition, in conjunction with this, after the exhaust valve Vb transitions to a closed state at the exhaust close timing EVC, the intake valve Va begins to open at the intake open timing IVO, increases and then reduces the lift amount, and transitions to a closed state at the intake close timing IVC.

In particular, as shown in FIG. 7, by setting the exhaust side to the limited exhaust timing and the intake side to the limited intake timing, the exhaust valve Vb transitions to a closed state at the exhaust close timing EVC, and after the crankshaft 1 rotates a set amount T from this transition, the intake valve Va begins to open at the intake open timing IVO.

This makes it possible, for example, to seal gas in the combustion chamber before the piston 4 reaches top dead center (TDC) when starting engine E, and as shown in the figure, the cylinder pressure P (combustion chamber pressure) is increased as the piston 4 rises twice. In this way, the gas temperature in the combustion chamber is increased by the compression of the gas by the cylinder pressure P caused by the rise of the piston 4, making ignition easier even in a cold state and improving the starting performance of engine E.

When engine E is stopped, the exhaust side is set to limited exhaust timing, and the intake side is set to limited intake timing. With fuel cut, gas is sealed inside the combustion chamber before the piston 4 reaches top dead center (TDC) when engine E is started. As the cylinder pressure P rises, the load acting on the crankshaft 1 is increased, and the engine is stopped quickly while preventing fresh air from being sent to the exhaust side.

[Control configuration]
As shown in Figures 1 and 2, engine E is equipped with a starter motor 15 that drives and rotates crankshaft 1, a crank angle sensor 16 capable of detecting the rotation angle is provided near crankshaft 1, an intake side cam angle sensor 17 capable of detecting the rotation angle of intake camshaft 7 is provided near intake camshaft 7, and an exhaust side cam angle sensor 18 capable of detecting the rotation angle of exhaust camshaft 8 is provided near exhaust camshaft 8.

The crank angle sensor 16, the intake side cam angle sensor 17, and the exhaust side cam angle sensor 18 are configured as pickups that output pulse signals intermittently as they rotate. The crank angle sensor 16 obtains the rotation angle from the rotation reference by counting pulse signals from the rotation reference of the crankshaft 1 as the crankshaft 1 rotates. Similarly, the intake side cam angle sensor 17 and the exhaust side cam angle sensor 18 are configured to count pulse signals from the rotation reference of the intake camshaft 7 as the intake camshaft 7 rotates, allowing the engine control device 40 to obtain the rotation angle from the rotation reference.

With this configuration, for example, by storing the count value of the crank angle sensor 16 when the drive case 21 and the internal rotor 22 are in a predetermined reference phase (e.g., intermediate phase) and the count value of the intake cam angle sensor 17 or the exhaust cam angle sensor 18, the relative rotational phase can be obtained by comparing the two count values regardless of whether the relative rotational phase is displaced from the reference phase to the advance side or the retard side (retard direction Sb).

As shown in FIG. 1, the engine control device 40 receives detection signals from the crank angle sensor 16, the intake cam angle sensor 17, and the exhaust cam angle sensor 18, as well as detection signals from the main switch 45, the temperature sensor 46, and the accelerator pedal sensor 47. The engine control device 40 also outputs control signals to the starter motor 15, the phase control motor M, and the combustion management unit 19.

In this control configuration, the main switch 45 is located on the panel of the driver's seat of the vehicle, and allows the engine E to be started and completely stopped manually. The accelerator pedal sensor 47 acquires the amount of depression of the accelerator pedal (not shown). The combustion management unit 19 manages the operation of pumps that supply fuel to the injectors 9, and manages the ignition order and timing by controlling the ignition circuit that supplies power to the spark plugs 10.

[Control configuration: engine control device]
The engine control device 40 includes a start control unit 41, an operating time control unit 42, and a stop control unit 43. These are configured as software, but each of them can also be partially configured as hardware.

The start control unit 41 starts the engine E when it is stopped. The operation control unit 42 basically sets the relative rotation phase between the drive case 21 and the internal rotor 22 when the engine E is operating. The stop control unit 43 stops the engine E based on the manual operation of the main switch 45. The stop control unit 43 may also automatically stop the engine E after the accelerator pedal is released, as in idling stop control.

[Control Mode]
An overview of the control of the engine E by the engine control device 40 is shown in the flowchart of Fig. 8. That is, when the engine E is started by turning on the main switch 45, a signal of the temperature of the engine E detected by the temperature sensor 46 is obtained (step #01), and if the obtained temperature is less than a set value (Yes in step #02), cold start control is performed (step #100), and if it is equal to or greater than the set value (No in step #02), normal start control is performed (step #03).

Cold start control (step #100) is set as a subroutine (details of this subroutine will be described later). In addition, in normal start control (step #03), the valve timing by the intake variable valve mechanism VTa and the valve timing by the exhaust variable valve mechanism VTb are set as shown in FIG. 4, or the timing of the intake valve Va is set to the retard side based on the timing in FIG. 4. Then, motoring is performed by driving the starter motor 15, and fuel is injected into the combustion chamber by the injector 9 at the set timing after motoring starts, and ignition is performed by the spark plug 10.

When the temperature of engine E is relatively high, such as after idle stop control, it is also possible to perform normal start control (step #03) by shifting the valve timing of the intake variable valve mechanism VTa to the retard side (retard direction Sb), motoring, inject fuel into the combustion chamber with the injector 9, and ignite the fuel with the spark plug 10.

Next, after engine E has started, operation control (step #04) is executed. This operation control (step #04) controls the intake side variable valve mechanism VTa based on information such as the depression amount of the accelerator pedal sensor 47 and the number of revolutions per unit time of the crankshaft 1 to control the intake amount, etc. This operation control (step #04) is continued as long as the situation continues in which no operation to stop engine E is performed (No in step #05), and when an operation to stop engine E is performed (Yes in step #05), stop control (step #200) is performed.

The stop control (step #200) is set as a subroutine, and the details of this subroutine will be described later. Furthermore, the operation of the main switch 45 is assumed as the operation for stopping the engine E. Note that the condition for stopping the engine E may be the timing when the accelerator pedal sensor 47 detects that the accelerator pedal has reached a non-operated state, as in the idle stop control described above.

[Control type: cold start control]
In cold start control (step #100), as shown in FIG. 9, the exhaust side variable valve mechanism VTb is set to limited exhaust timing (most advanced), the intake side variable valve mechanism VTa is set to limited intake timing (retarded) (steps #101 and #102), motoring is performed by driving the starter motor 15, and at the set timing after this motoring, fuel is injected into the combustion chamber by the injector 9 and ignition is performed by the spark plug 10 (steps #103 and #104).

If after motoring and ignition have been performed in this way, the start of engine E cannot be confirmed based on the detection signal of crank angle sensor 16, etc. (No in step #105), motoring and ignition are continued, and if the start of engine E is confirmed (Yes in step #105), control of this subroutine is terminated and the process returns to the operation control (step #04).

In this cold start control, as shown in Figures 6 and 7, the valve timing by the intake variable valve mechanism VTa is set to the retarded side, and the valve timing by the exhaust variable valve mechanism VTb is set to the most advanced side. This setting is performed by the start control unit 41, and when setting the valve timing in this way, the engine control device 40 controls the intake side and exhaust side phase control motors M while acquiring signals from the crank angle sensor 16, the intake side cam angle sensor 17, and the exhaust side cam angle sensor 18.

In this way, when the crankshaft 1 rotates with the valve timing set, the exhaust valve Vb transitions to a closed state at the exhaust close timing EVC, and after the crankshaft 1 rotates the set amount T, the intake valve Va begins to open at the intake open timing IVO, so that gas is sealed in the combustion chamber before the piston 4 reaches top dead center TDC, and the gas temperature in the combustion chamber is raised by the compression of the gas as the piston 4 rises, making ignition easier and improving the startability of the engine E. Then, for example, by this motoring, the crankshaft 1 is returned to the operating control after it is confirmed that it has rotated the set number of times.

[Control mode: Stop control]
In the stop control (step #200), as shown in Figures 6 and 7, the exhaust side variable valve mechanism VTb is set to the limited exhaust timing (most advanced), the intake side variable valve mechanism VTa is set to the limited exhaust timing (retarded) (steps #201 and #202), and fuel cut is performed (step #203). That is, in this (step #200), the valve timing is set in the same way as in the cold start control (step #100).

In this way, when stopping the engine E, the engine control device 40 controls the intake side and exhaust side phase control motors M while acquiring signals from the crank angle sensor 16, the intake side cam angle sensor 17, and the exhaust side cam angle sensor 18, sets the exhaust side variable valve mechanism VTb to the limited exhaust timing, and sets the intake side variable valve mechanism VTa to the limited exhaust timing. Control then returns after the fuel cut.

By performing this type of control, gas is sealed in the combustion chamber before the piston 4 reaches top dead center (TDC), increasing the load acting on the crankshaft 1 when the piston 4 rises, and quickly stopping the engine E. Also, by performing this type of control, fresh air is not sent from the combustion chamber to the exhaust manifold 12, preventing the inconvenience of reducing the performance of the catalyst 13.

[Effects of the embodiment]
In the conventional exhaust side variable valve mechanism VTb (exhaust side valve timing control mechanism), even when set to the most advanced phase, the EVC position was determined so as to maintain an open state until the piston 4 reached top dead center TDC during the exhaust stroke, so that gas could not be compressed in the cylinder during the exhaust stroke. In contrast, by configuring the exhaust side variable valve mechanism VTb to close the exhaust valve Vb (transition to exhaust closing timing EVC) before the piston 4 reaches top dead center TDC when set to the most advanced phase, it is possible to seal gas in the combustion chamber and compress it before the piston 4 reaches top dead center TDC.

With this configuration, when starting the engine E, the exhaust side variable valve mechanism VTb is set to exhaust restriction timing, and the gas in the combustion chamber is compressed twice in one cycle while remaining there, greatly increasing the in-cylinder pressure P (performing in-cylinder warming), thereby ensuring reliable starting even in cold starts. In particular, by controlling the intake side variable valve mechanism VTa to restricted intake timing in conjunction with the control of setting the exhaust side variable valve mechanism VTb to exhaust restriction timing, gas discharged from the combustion chamber is completely eliminated, further promoting in-cylinder warming and ensuring good starting of the engine E.

When engine E is stopped, the exhaust side variable valve mechanism VTb is set to exhaust restriction timing, which increases the load acting on the crankshaft 1 as the pressure in the combustion chamber increases, thereby realizing a quick stop and suppressing the inconvenience of gas flowing out of the combustion chamber into the exhaust manifold 12, thereby improving fuel efficiency. When engine E is stopped, the amount of fresh air sent from the exhaust valve Vb to the exhaust manifold 12 is greatly reduced, suppressing deterioration of the catalyst 13 caused by fresh air coming into contact with the catalyst 13 and suppressing a drop in the temperature of the catalyst 13.

In particular, when engine E is stopped, by controlling the intake side variable valve mechanism VTa to set the intake side variable valve mechanism VTa to the exhaust limit timing in conjunction with the exhaust side variable valve mechanism VTb to set the exhaust limit timing, engine E can be stopped more quickly, fuel economy can be improved, and adverse effects on the catalyst 13 can be eliminated.

It is also possible to use a conventional configuration in which the relative rotational phase is changed hydraulically as the intake side variable valve mechanism VTa (intake side valve timing control mechanism), and by simply setting the intake side variable valve mechanism VTa to the retarded side (it does not have to be fully retarded), good cold starting is possible and the engine E can be stopped quickly.

For example, if the intake side variable valve mechanism VTa sets the valve timing to a large retard side, and if the intake side variable valve mechanism VTa experiences a malfunction that makes it uncontrollable while the valve timing is set to a large retard side, it is conceivable that the engine E will be unable to start. However, if the exhaust side variable valve mechanism VTb is set to the restricted exhaust mode, the engine E will be able to start even if the exhaust side variable valve mechanism VTb fails.

Furthermore, when the exhaust side variable valve mechanism VTb is set to the restricted exhaust mode, the pressure in the combustion chamber increases, suppressing the phenomenon of negative pressure acting in the combustion chamber, and preventing lubricating oil from being unnecessarily sucked in due to the action of negative pressure.

[Another embodiment]
The present invention may be configured as follows other than the above-described embodiment (common numbers and symbols as in the embodiment are used to designate components having the same functions as in the embodiment).

(a) When engine E is cold started, the intake opening timing IVO of the intake variable valve mechanism VTa (intake valve timing control mechanism) is not set to the retarded side of top dead center TDC, but only the timing of the exhaust variable valve mechanism VTb (exhaust valve timing control mechanism) is set to the most advanced angle.

When this type of control is performed, some of the gas in the combustion chamber leaks out of the intake valve Va into the exhaust side when the piston 4 rises during the exhaust stroke. However, it is still possible to increase the pressure in the combustion chamber. Therefore, although there is some decrease in performance, it is possible to cold start and stop the engine E compared to when the intake opening timing IVO of the intake side variable valve mechanism VTa is set to the retard side of top dead center TDC.

(b) To enable cold starting, it is necessary to configure the exhaust side variable valve mechanism VTb (exhaust side valve timing control mechanism) to be of an electric type. However, for example, assuming stop control of engine E, the exhaust side variable valve mechanism VTb may be of a hydraulic type.

The present invention can be used in a control device for an internal combustion engine.

1 Crankshaft 4 Piston 7 Intake camshaft 8 Exhaust camshaft 21 Drive case (intake drive side rotor/exhaust drive side rotor)
22 Inner rotor (intake driven rotor/exhaust driven rotor)
41 Start control unit (control unit)
43 Stop control unit (control unit)
46 Temperature sensor E Engine (internal combustion engine)
Ma Intake side phase control motor (intake side actuator)
Mb Exhaust side phase control motor (exhaust side actuator)
Va: Intake valve Vb: Exhaust valve VTa: Intake side variable valve mechanism (intake side valve opening/closing timing control mechanism)
VTb Exhaust side variable valve mechanism (exhaust side valve timing control mechanism)
X Rotation axis TDC Top dead center BDC Bottom dead center EVO Exhaust opening timing EVC Exhaust closing timing IVO Intake opening timing IVC Intake closing timing θ1 First angle θ2 Second angle θ3 Third angle θ4 Fourth angle

Claims (3)

an exhaust drive side rotor that rotates synchronously with a crankshaft of the internal combustion engine;
an exhaust driven rotor that rotates together with an exhaust camshaft to open and close an exhaust valve of a combustion chamber of the internal combustion engine and is disposed coaxially with a rotation axis of the exhaust driving rotor;
an exhaust-side valve timing control mechanism including an exhaust-side actuator that sets an exhaust-side relative rotation phase between the exhaust driving-side rotor and the exhaust driven-side rotor,
the exhaust-side valve timing control mechanism is configured to be capable of switching between a normal exhaust timing that constantly keeps the exhaust valve open while the piston of a predetermined cylinder of the internal combustion engine moves from the bottom dead center to the top dead center, and a limited exhaust timing that is more advanced than the normal exhaust timing so as to transition the exhaust valve to a closed state before the piston reaches the top dead center,
a control unit that switches between the normal exhaust timing and the limited exhaust timing by controlling the exhaust side actuator ,
an intake drive-side rotor that rotates synchronously with the crankshaft of the internal combustion engine;
an intake driven rotor that rotates integrally with an intake camshaft to open and close an intake valve of a combustion chamber of the internal combustion engine and is disposed coaxially with a rotation axis of the intake driving rotor;
an intake side actuator that sets an intake side relative rotation phase between the intake driving side rotor and the intake driven side rotor,
the intake-side valve timing control mechanism is configured to be capable of switching between a normal intake timing for opening the intake valve before the piston reaches the top dead center or simultaneously with the piston reaching the top dead center when a predetermined cylinder of the internal combustion engine is in an exhaust stroke, and a limited intake timing that is retarded from the normal intake timing and opens the intake valve after the piston reaches the top dead center,
the control unit sets the intake-side valve timing control mechanism to the limited intake timing in coordination with a control for setting the exhaust-side valve timing control mechanism to the limited exhaust timing,
When the bottom dead center is defined as BDC, the top dead center is defined as TDC, the timing at which the exhaust valve opens is defined as EVO, the timing at which the intake valve opens is defined as IVO, the timing at which the intake valve closes is defined as IVC, the timing at which the exhaust valve closes is defined as EVC, the timing before BDC is defined as BBDC, and the timing after BDC is defined as ABDC,
At the limited exhaust timing, the EVO is on the retard side of the TDC and the EVC is on the advance side of the TDC,
A relationship between a first angle θ1 from the BDC to the EVO at the BBDC and a second angle θ2 from the BDC to the EVC at the ABDC is θ1≧θ2, and
At the limited intake timing, the IVO is on the retard side of the TDC, the IVC is on the advance side of the TDC, and the IVC is greater than 90 degrees at the ABDC with respect to the BDC;
A control device for an internal combustion engine, wherein a relationship between a third angle θ3 from the BDC to the IVO at the BBDC and a fourth angle θ4 from the BDC to the IVC at the ABDC is θ3≧θ4 . A temperature sensor is provided to measure a temperature of the internal combustion engine.
2. The control device for an internal combustion engine according to claim 1, wherein, when the internal combustion engine is started in a situation in which the temperature detected by the temperature sensor is less than a set value, the control unit sets the exhaust-side valve timing control mechanism to the limited exhaust timing, starts motoring to rotate the crankshaft, and then supplies fuel to a combustion chamber and performs ignition . 2. The control device for an internal combustion engine according to claim 1, wherein, when the internal combustion engine is stopped, the control unit stops the supply of fuel to the combustion chamber with the exhaust-side valve timing control mechanism set to the limited exhaust timing.

Images