VALVE OPENING AND CLOSING TIMING CONTROL DEVICE

A valve open/close timing controller including a driving-side rotating body rotating about a rotating shaft core synchronously with a crankshaft of an internal combustion engine with a driven-side rotating body inside the driving-side rotating body and coaxially with the rotating shaft core that rotates integrally with a camshaft to open/close an intake valve of an internal combustion engine. A phase adjusting mechanism sets a relative rotation phase between the driving-side and driven-side and a phase controller performs a retard operation to shift the relative rotation phase to a most retarded phase by displacing the driven-side rotating body in a direction opposite to the driving-side rotating body, and, when rotational speed of the engine reaches a lower limit rotational speed during stopping of the engine, advances the relative rotation phase as the most retarded phase by displacing the driven-side rotating body in a same direction as the driving-side rotating body.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2023-031255, filed on Mar. 1, 2023, the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a valve opening and closing range control device.

BACKGROUND DISCUSSION

Conventionally, there is known a valve opening and closing timing control device configured to control a valve opening and closing timing by cam portions of a camshaft based on torque transmitted from a crankshaft of an internal combustion engine. A vehicle including such a valve opening and closing timing control device is, for example, disclosed in Japanese Patent Application Publication No. 2016-205195 below.

A hybrid vehicle is disclosed in Japanese Patent Application Publication No. 2016-205195. In the hybrid vehicle, while the engine is being stopped, the valve opening and closing timing control device is configured to shift a valve opening timing of an intake valve to a retard side. While shifting the valve opening timing of the intake valve to the retard side, and upon receipt of a request to restart the engine before the engine stops, the valve opening and closing timing control device is configured to shift the valve opening timing of the intake valve to an advance side.

In the hybrid vehicle disclosed in Japanese Patent Application Publication No. 2016-205195, when a supply of fuel to the engine is stopped, the valve opening timing of the intake valve is shifted to the retard side. With this configuration, a supply of fresh air, which may deteriorate a catalyst (catalyst for purifying an exhaust gas) in an exhaust flow path, is less prone to occur. Additionally, while the engine is being stopped, the catalyst is not brought into a lean state (oxygen-rich state), so that an excessive supply of the fuel is less prone to occur at next start of the engine. However, upon receipt of the request to restart the engine when the valve opening timing of the intake valve is in the retard phase, the valve opening timing needs to be advanced to a phase in which the engine can be ignited. Accordingly, with the hybrid vehicle disclosed in Japanese Patent Application Publication No. 2016-205195, a delay (response delay) may occur in response to the request to restart the engine and thus, drivability may deteriorate.

A need thus exists for a valve opening and closing timing control device which is not susceptible to the drawback mentioned above.

SUMMARY

A valve opening and closing timing control device includes: a driving-side rotating body configured to rotate about a rotating shaft core synchronously with a crankshaft of an internal combustion engine; a driven-side rotating body located inside the driving-side rotating body and coaxially with the rotating shaft core, and configured to rotate integrally with a camshaft for opening and closing an intake valve of the internal combustion engine; a phase adjusting mechanism configured to set a relative rotation phase between the driving-side rotating body and the driven-side rotating body by a driving force of an electric motor; and a phase controller configured, upon receipt of a command to stop the internal combustion engine, to perform retard operation control to shift the relative rotation phase to a most retarded phase by displacing the driven-side rotating body in a direction opposite to a rotating direction of the driving-side rotating body, and configured, when rotational speed of the internal combustion engine reaches a lower limit rotational speed predetermined during stopping of the internal combustion engine, to perform advance operation control to advance the relative rotation phase as the most retarded phase by displacing the driven-side rotating body in a direction same as the rotating direction of the driving-side rotating body.

DETAILED DESCRIPTION

An embodiment of this disclosure will be described with reference to the attended drawings.

Hereinafter, a valve opening and closing timing control device100of this embodiment will be described.FIG.1is a cross-sectional view of an internal combustion engine (hereinafter, referred to as an “engine E”) including the valve opening and closing timing control device100.FIG.2is a cross-sectional view of the valve opening and closing timing control device100.FIG.3is a cross-sectional view taken along line III-III ofFIG.2.

As illustrated inFIG.1, the engine E includes an intake valve Va and an exhaust valve Vb. The valve opening and closing timing control device100sets a valve timing (valve opening and closing timing) of the intake valve Va. In this embodiment, a valve opening and closing timing control device101is also provided to set a valve timing of the exhaust valve Vb. The valve opening and closing timing control device100, the valve opening and closing timing control device101, and driving of the engine E are controlled by a phase controller9.

The valve opening and closing timing control device101for setting the valve timing of the exhaust valve Vb may be omitted.

The engine E is arranged in a vehicle and outputs travel driving force of the vehicle. The phase controller9is designed, when an operation of the engine E is temporarily stopped during travel of the vehicle, to reduce degradation in fuel consumption as well as increase drivability at restart of the engine E (as will be described in detail later).

As illustrated inFIGS.1and2, in the engine E, a cylinder head103is connected to an upper portion of a cylinder block102that rotatably supports a crankshaft1, and a piston4is reciprocatably housed in a plurality of cylinder bores in the cylinder block102. In this embodiment, the piston4is connected to the crankshaft1through a connecting rod5, and is designed as a four-cycle piston.

As described above, the intake valve Va and the exhaust valve Vb are arranged in the cylinder head103. An intake camshaft2for opening and closing the intake valve Va and an exhaust camshaft3for opening and closing the exhaust valve Vb are provided above the cylinder head103.

The cylinder head103includes an injector109for injecting fuel into a combustion chamber and an ignition plug110. An intake manifold111for supplying air to the combustion chamber through the intake valve Va and an exhaust manifold112for expelling combustion gas out of the combustion chamber through the exhaust valve Vb are connected to the cylinder head103. The exhaust manifold112includes a catalyst113for purifying exhaust gas flowing through the exhaust manifold112. The catalyst113corresponds to a typically called three-way catalyst for oxidation reaction of CO or HC and reduction reaction of NOx. The engine E includes a starter motor115for driving and rotating the crankshaft1at start of the engine E.

As illustrated inFIG.2, the valve opening and closing timing control device100includes a driving-side rotating body A, a driven-side rotating body B, and a phase adjusting mechanism C. The driving-side rotating body A rotates about a rotating shaft core X synchronously with the crankshaft1of the engine E as the internal combustion engine. The driven-side rotating body B is located inside the driving-side rotating body A and coaxially with the rotating shaft core X. The driven-side rotating body B rotates integrally with the intake camshaft2(as an example of a “camshaft”) for opening and closing the intake valve Va of the engine E. The phase adjusting mechanism C sets a relative rotation phase between the driving-side rotating body A and the driven-side rotating body B by a driving force of an electric motor M.

A timing chain6(a timing belt or the like may be used instead) is wound about an output sprocket1S of the crankshaft1of the engine E and a driving sprocket11S of the driving-side rotating body A.

During the operation of the engine E, the entire valve opening and closing timing control device100rotates about the rotating shaft core X in a driving rotational direction S by the driving force from the timing chain6. Additionally, the driving force of the electric motor M activates the phase adjusting mechanism C, causing the driven-side rotating body B to be displaceable in the same direction as or in the opposite direction to a rotating direction of the driving-side rotating body A. When the driven-side rotating body B is displaced as described above, the same direction as the driving rotational direction S is referred to as an advance direction Sa, and the opposite direction to the driving rotational direction S is referred to as a retard direction Sb. The phase adjusting mechanism C sets the relative rotation phase between the driving-side rotating body A and the driven-side rotating body B by these displacements, thereby resulting in control of the valve opening and closing timing of the intake valve Va performed by cam portions2A of the intake camshaft2.

Here, an operation to displace the driven-side rotating body B relatively in the same direction as the rotating direction of the driving-side rotating body A is referred to as an advance operation, which increases an intake compression ratio. On the other hand, an operation to displace the driven-side rotating body B relatively in the opposite direction to the rotating direction of the driving-side rotating body A (in the opposite direction to the direction selected in the advance operation) is referred to as a retard operation, which reduces the intake compression ratio.

[Valve Opening and Closing Timing Control Device]

As illustrated inFIG.2, the driving-side rotating body A includes an outer case11, and a front plate12fastened to the outer case11with a plurality of fastening bolts13. The outer case11has a driving sprocket11S formed on its outer circumference. The outer case11, having a bottomed tubular shape, has an opening at its bottom. The front plate12is located opposite to the intake camshaft2with respect to an eccentric member26in a direction along the rotating shaft core X.

As illustrated inFIGS.2and3, an intermediate member20as the driven-side rotating body B and the phase adjusting mechanism C having a hypocycloid gear mechanism are housed in an inner space of the outer case11. The phase adjusting mechanism C also includes an Oldham coupling Cx that reflects the phase shifting on the driving-side rotating body A and the driven-side rotating body B.

In the intermediate member20as the driven-side rotating body B, a support wall21and a tubular wall22are integrally formed. The support wall21is connected to the intake camshaft2in an orientation orthogonal to the rotating shaft core X, and the tubular wall22has a tubular shape about the rotating shaft core X and protrudes from an outer peripheral edge of the support wall21in a direction away from the intake camshaft2.

The intermediate member20is relatively rotatably fitted, with an outer surface of the tubular wall22being in contact with an inner surface of the outer case11, and then fixed to an end of the intake camshaft2with a connecting bolt23inserted through a through hole at a center of the support wall21. In this fixed state, an outer end of the tubular wall22(an end farther from the intake camshaft2) is located inward of the front plate12.

As illustrated inFIG.2, the electric motor M is supported to the engine E by a support frame7such that an output shaft Ma of the electric motor M is arranged coaxially with the rotating shaft core X. On the output shaft Ma of the electric motor M, a pair of engaging pins8are formed orthogonally to the rotating shaft core X.

As illustrated inFIGS.2and3, the phase adjusting mechanism C includes the intermediate member20, an output gear25on an inner circumferential surface of the tubular wall22of the intermediate member20, the eccentric member26, an elastic member SP, a first bearing28, a second bearing29, an input gear30, a fixing ring31, a spacer32having a ring shape, and the Oldham coupling Cx. In this embodiment, the first bearing28corresponds to a ball bearing having an inner ring28ain contact with an outer circumferential surface of the eccentric member26and an outer ring28bin contact with an inner peripheral surface of the intermediate member20. The second bearing29corresponds to a ball bearing having an inner ring29ain contact with the outer circumferential surface of the eccentric member26and an outer ring29bin contact with an inner peripheral surface of the input gear30.

As illustrated inFIG.2, at a position inward of the inner circumference of the tubular wall22(position adjacent to the support wall21) of the intermediate member20, a support surface22S is formed about the rotating shaft core X in a direction extending along the rotating shaft core X (hereinafter, referred to as “axially”), and the output gear25is formed about the rotating shaft core X at a position outward of the support surface22S (at a side farther from intake camshaft2).

The eccentric member26has a tubular shape. On the outer circumferential surface of the eccentric member26, a circumferential support surface26S is formed axially inward of the rotating shaft core X (formed at a side closer to the intake camshaft2). At a position axially more inward of the circumferential support surface26S (at a position further closer to the intake camshaft2), a flange26Q protrudes radially outward from the circumferential support surface26S. Additionally, on the outer circumferential surface of the eccentric member26(at the side farther from the intake camshaft2), an eccentric support surface26E is formed about an eccentric shaft core Y extending eccentrically parallel to the rotating shaft core X. Thus, on the eccentric member26, the flange26Q, the circumferential support surface26S, and the eccentric support surface26E are axially arranged in this sequential order from the side closer to the intake camshaft2. A direction extending along the eccentric shaft core Y is identical to the direction that has been referred to as “axially”, and is thus hereinafter referred to simply as “axially”.

As illustrated inFIGS.2and3, the eccentric support surface26E has a first recess70recessed radially inward of the eccentric member26. On a bottom surface of the first recess70and at both circumferential ends of the eccentric member26, a pair of second recesses79,79are recessed radially and axially with respect to the eccentric member26. In this embodiment, the first recess70has a circumferentially symmetric shape.

Each of the pair of second recesses79,79is formed at the corresponding circumferential end of the eccentric member26in the first recess70. Each of the pair of second recesses79,79has a bottom surface formed radially of the eccentric member26, and the bottom surface has a maximum depth that is greater than a depth of the bottom surface of the first recess70near a circumferential center of the eccentric member26. In each of the pair of second recesses79,79formed circumferentially of the eccentric member26, a surface from the corresponding bottom surface to the corresponding end has a shape along a curved shape of a spring member71as will be described later.

An elastic member SP is fitted into the first recess70. The elastic member SP includes the pair of spring members71,71. In this embodiment, the pair of spring members71,71are identical in shape and size. The elastic member SP applies an energizing force to the input gear30through the second bearing29such that a part of external teeth30A of the input gear30engage with a part of internal teeth25A of the output gear25.

On the inner circumference of the eccentric member26, a pair of engaging grooves26T, to which the pair of engaging pins8of the electric motor M are respectively engageable, are formed parallel to the rotating shaft core X.

When the first bearing28has been fitted to an outer circumference of the circumferential support surface26S, and then the first bearing28has been fitted to the support surface22S of the tubular wall22, the eccentric member26is rotatably supported about the rotating shaft core X with respect to the intermediate member20. The input gear30is supported to the eccentric support surface26E of the eccentric member26through the second bearing29so as to be rotatable about the eccentric shaft core Y.

In the phase adjusting mechanism C, the external teeth30A of the input gear30have one tooth less than the internal teeth25A of the output gear25. In this state, a part of the external teeth30A of the input gear30engage with a part of the internal teeth25A of the output gear25.

As illustrated inFIG.2, the fixing ring31is supported by the outer circumference of the eccentric member26in a fitted state so that, with the spacer32interposed between the fixing ring31and the second bearing29, the fixing ring32prevents the second bearing29from coming off.

As illustrated inFIG.3, the Oldham coupling Cx corresponds to a coupling member40having a plate shape, and in the coupling member40, an annular portion41, a pair of external engaging arms42, and a pair of internal engaging arms43are integrally formed. The annular portion is located at a center of the coupling member40, the pair of external engaging arms42protrude radially outward from the annular portion41in a first direction (left to right inFIG.3), and the pair of internal engaging arms43protrude radially outward from the annular portion41in a second direction (top to bottom inFIG.3) orthogonal to the first direction.

Each of the pair of internal engaging arms43has an engaging recess43acontinuous with an opening of the annular portion41.

As illustrated inFIGS.2and3, the outer case11has a pair of guide grooves11aat its opening edges that the front plate12abuts. Each of the pair of guide grooves11ais designed as a through groove extending radially about the rotating shaft core X from the inner space to an outer space of the outer case11. Each of the guide grooves11ahas a groove width designed slightly greater than a width of the corresponding external engaging arm42.

The input gear30has an end face opposing the front plate12, and a pair of engaging projections30T are integrally formed on the end faces. Each of the engaging projections30T has an engaging width designed slightly smaller than an engaging width of the corresponding engaging recess43aof the pair of internal engaging arms43.

With this configuration, the pair of external engaging arms42of the coupling member40respectively engage with the pair of guide grooves11aof the outer case11, and the pair of engaging projections30T of the input gear30respectively engage with the pair of engaging recesses43aof the pair of internal engaging arm43of the coupling member40, thereby causing the Oldham coupling Cx to function.

The coupling member40is displaceable in the first direction (left to right inFIG.3) in which the pair of external engaging arms42extend with respect to the outer case11, and the input gear30is displaceable in the second direction (top to bottom inFIG.3) along which the pair of engaging recesses43aof the pair of internal engaging arms43are formed with respect to the coupling member40.

With the spacer32interposed between the Oldham coupling Cx (coupling member40) and the second bearing29, the second bearing29moves axially only within a distance equal to or smaller than a predetermined set value.

On a surface of the front plate12opposing the input gear30, a recess12dis recessed outward (to the side farther from the intake camshaft2). The recess12dopposes an opening of the coupling member40of the front plate12, and is formed slightly greater in circumferential length and axial length than the opening of the coupling member40. Thus, the engaging projection30T of the input gear30is prevented from coming into contact with the front plate12.

[Valve Opening and Closing Timing Control Device-Location of Each Component]

As illustrated inFIG.2, in the valve opening and closing timing control device100, the support wall21of the intermediate member20is connected to the end of the intake camshaft2with the connecting bolt23, and these components rotate integrally. The eccentric member26is supported to the intermediate member20by the first bearing28so as to be relatively rotatable about the rotating shaft core X. As illustrated inFIG.2, the input gear30is supported to the eccentric support surface26E of the eccentric member26by the second bearing29, so that a part of the external teeth30A of the input gear30engage with a part of the internal teeth25A of the output gear25.

Further, as illustrated inFIG.3, each of the pair of external engaging arms42of the Oldham coupling Cx engages with the corresponding guide groove11aof the outer case11, and each of the pair of engaging projections30T of the input gear30engages with the corresponding engaging recess43aof the pair of internal engaging arms43of the Oldham coupling Cx. As illustrated inFIG.2, the front plate12is located outward of the coupling member40of the Oldham coupling Cx, so that the coupling member40is movable orthogonally to the rotating shaft core X while being in contact with an inner surface of the front plate12. With this configuration, the Oldham coupling Cx is located outward of the first bearing28and the second bearing29(at the side farther from the intake camshaft2) and inward of the front plate12(at the side closer to the intake camshaft2).

As illustrated inFIG.2, each of the pair of engaging pins8formed on the output shaft Ma of the electric motor M engages with the corresponding engaging groove26T of the eccentric member26.

[Mode of Operation of Phase Adjusting Mechanism]

As illustrated inFIGS.1and2, in a vicinity of the crankshaft1, a crank angle sensor116is provided to detect a rotational angle of the crankshaft1. In a vicinity of the intake camshaft2, an intake-side cam angle sensor117is provided to detect a rotational angle of the intake camshaft2; and in a vicinity of the exhaust camshaft3, an exhaust-side cam angle sensor118is provided to detect a rotational angle of the exhaust camshaft3.

Each of the crank angle sensor116, the intake-side cam angle sensor117, and the exhaust-side cam angle sensor118is designed to intermittently output a pulse signal as the corresponding shaft rotates. When the crankshaft1rotates, the crank angle sensor116counts the pulse signals from a rotation reference of the crankshaft1to acquire the rotational angle from the rotation reference. Similarly, when the intake camshaft2rotates, each of the intake-side cam angle sensor117and the exhaust-side cam angle sensor118counts the pulse signals from a rotation reference of the intake camshaft2such that the phase controller9acquires the rotational angle from the rotation reference.

Here, for example, with the outer case11and the intermediate member20being in predetermined reference phases (e.g., intermediate phases), the counts from the crank angle sensor116and the counts from the intake-side cam angle sensor117or the exhaust-side cam angle sensor118are stored. As a result, even when the relative rotation phase is displaced from the reference phase to any one of the advance side (in the advance direction Sa) and the retard side (in the retard direction Sb), it is possible to acquire the relative rotation phase based on comparison between the counts from the two sensors.

The phase controller9receives inputs of detection signals from the crank angle sensor116, the intake-side cam angle sensor117, and the exhaust-side cam angle sensor118, together with inputs of detection signals from a main switch145, a temperature sensor146, and an accelerator pedal sensor147. The phase controller9outputs a control signal to the starter motor115, the electric motor M, and a combustion management unit119.

In this control configuration, the main switch145is located on a panel of a driver's seat of the vehicle, and allows the start and complete stop of the engine E by manual operation. The accelerator pedal sensor147acquires a stepping amount of an accelerator pedal (not illustrated). The combustion management unit119manages operations of pumps for supplying fuel to the injector109, and manages an ignition order and timing by controlling an ignition circuit for supplying power to the ignition plug110.

The electric motor M is under control of the phase controller9. As described above, the engine E includes the crank angle sensor116, the intake-side cam angle sensor117, and the exhaust-side cam angle sensor118for detecting rotational speed (number of revolutions per unit time) of the crankshaft1or the intake camshaft2, and the detection signals from these sensors are input to the valve opening and closing timing control device.

The phase controller9maintains the relative rotation phase by driving the electric motor M at a speed equal to the rotational speed of the intake camshaft2during the operation of the engine E. When the rotational speed of the electric motor M is lower than the rotational speed of the intake camshaft2, the phase controller9performs the advance operation. On the other hand, when the rotational speed of the electric motor M is higher, the phase controller9performs the retard operation. The advance operation increases the intake compression ratio, while the retard operation reduces the intake compression ratio.

When the electric motor M rotates at a speed equal to rotational speed of the outer case11(the speed equal to the rotational speed of the intake camshaft2), an engaging position of the external teeth30A of the input gear30with the internal teeth25A of the output gear25does not change. Thus, the relative rotation phase of the driven-side rotating body B to the driving-side rotating body A is maintained.

On the other hand, when the output shaft Ma of the electric motor M is driven and rotated at a speed higher or lower than the rotational speed of the outer case11, the eccentric shaft core Y of the phase adjusting mechanism C revolves about the rotating shaft core X. Due to this revolution, the engaging position of the external teeth30A of the input gear30with the internal teeth25A of the output gear25is displaced along an inner periphery of the output gear25, and a rotational force acts between the input gear30and the output gear25. In other words, a rotational force about the rotating shaft core X acts on the output gear25, and a rotational force for rotating about the eccentric shaft core Y acts on the input gear30.

Each of the pair of engaging projections30T of the input gear30engages with the corresponding engaging recess43aof the pair of internal engaging arms43of the coupling member40. In this state, the input gear30does not rotate with respect to the outer case11, and the rotational force thus acts on the output gear25. Due to the rotational force acted on the output gear25, the intermediate member20along with the output gear25rotates about the rotating shaft core X with respect to the outer case11. As a result, the relative rotation phase between the driving-side rotating body A and the driven-side rotating body B is set, and the valve opening and closing timing is set by the intake camshaft2.

Additionally, when the eccentric shaft core Y of the input gear30revolves about the rotating shaft core X, the input gear30is displaced, in response to which the coupling member40as the Oldham coupling Cx is displaced in the direction (first direction) in which the pair of external engaging arms42extend with respect to the outer case11. The input gear30is displaced in the direction (second direction) in which the pair of internal engaging arms43extend.

As described above, the external teeth30A of the input gear30have one tooth less than the internal teeth25A of the output gear25. Thus, when the eccentric shaft core Y of the input gear30revolves once about the rotating shaft core X, the output gear25rotates by one tooth, thereby resulting in a greater deceleration.

The relative rotation phase between the outer case11and the intermediate member20is under control of the phase controller9.FIG.4is a diagram illustrating an intake timing In of the intake valve Va under control of the valve opening and closing timing control device100at the intake side and an exhaust timing Ex of the exhaust valve Vb under control of the valve opening and closing timing control device101at the exhaust side.FIG.4is a diagram when the intake timing In of the intake valve Va is set to the retard side and the exhaust timing Ex of the exhaust valve Vb is set to normal.

Specifically, when the intake timing In of the intake valve Va is set to the retard side, the valve opening timing of the intake valve Va (hereinafter, referred to as an intake valve open (IVO)) is retarded from (in the retard direction Sb of) a top dead center (TDC), and the valve closing timing of the intake valve Va (hereinafter, referred to as an intake valve close (IVC)) is retarded from (in the retard direction Sb of) a bottom dead center (BDC). In other words, during a compression stroke in which the piston4moves from the BDC to the TDC, the intake valve Va shifts from an open state to a closed state.

When the exhaust timing Ex of the exhaust valve Vb is set to normal, the valve closing timing of the exhaust valve Vb (hereinafter, referred to as an exhaust valve close (EVC)) is aligned with the TDC, and the valve opening timing of the exhaust valve Vb (hereinafter, referred to as an exhaust valve open (EVO)) is advanced from (arranged in the advance direction Sa of) the BDC. In other words, during an exhaust stroke in which the piston4moves from the BDC to the TDC, the exhaust valve Vb is constantly maintained at an open state.

With the intake timing In of the intake valve Va being set to the retard side, when the exhaust valve Vb has shifted to a closed state at the EVC, causing the crankshaft1to rotate by a predetermined amount, the intake valve Va starts to shift to the open state at the IVO. Then, during the compression stroke in which the piston4moves from the BDC to the TDC, the intake valve Va shifts from the open state to the closed state.

With this configuration, before the piston4reaches the TDC, the gas is sealed in the combustion chamber, and in-cylinder pressure (pressure in the combustion chamber) is thus increased, leading to compression of the gas and an increase in temperature of the gas in combustion chamber.

On the other hand, when the rotational speed of the engine E is increased during the travel of the vehicle, the phase controller9increases an amount of intake air. In this case, the valve opening and closing timing control device100at the intake side is under control to rearrange the IVO to the advance side (in the advance direction Sa).FIG.5is a diagram when the intake timing In of the intake valve Va is set to the advance side and the exhaust timing Ex of the exhaust valve Vb is set to normal.

Specifically, when the intake timing In of the intake valve Va is set to the advance side, the IVO is advanced from (arranged in the advance direction Sa of) the TDC. In this state too, the IVC is retarded from (in the retard direction Sb of) the BDC. In other words, during the compression stroke in which the piston4moves from the BDC to the TDC, the intake valve Va shifts from the open state to the closed state.

Concurrently, when the exhaust timing Ex of the exhaust valve Vb is set to normal, the EVC is aligned with the TDC, and the EVO is advanced from (arranged in the advance direction Sa of) the BDC. In other words, during the exhaust stroke in which the piston4moves from the BDC to the TDC, the exhaust valve Vb is constantly maintained at the open state.

With the intake timing In of the intake valve Va being set to the advance side, when the intake valve Va has shifted to the open state at the IVO, causing the crankshaft1to rotate by the predetermined amount, the exhaust valve Vb starts to shift to the closed state at the EVC. As described above, with the intake timing In of the intake valve Va being set to the advance side, immediately before the exhaust valve Vb shifts to the closed state at the EVC, the intake valve Va starts to shift to the open state at the IVO, thereby forming an overlap range where the exhaust valve Vb and the intake valve Va are simultaneously open.

In this embodiment, upon receipt of a command to stop the engine E, the phase controller9performs retard operation control to shift the relative rotation phase to a most retarded phase by displacing the intermediate member20in the opposite direction to a rotating direction of the outer case11; and when the rotational speed of the engine E reaches a lower limit rotational speed N2predetermined during stopping of the engine E, the phase controller9performs advance operation control to advance the relative rotation phase as the most retarded phase by displacing the intermediate member20in the same direction as the rotating direction of the outer case11.

The command to stop the engine E is transmitted from a host system of the phase controller9. The command to stop the engine E corresponds to an intermittent stop command to temporarily stop the operation of the engine E during the travel of the vehicle. In this intermittent stop command, the engine E is stopped when, for example, the vehicle is at a speed equal to or lower than a first speed predetermined, and the engine E is stopped for a predetermined period of time (e.g., a typically called idling stop) when the vehicle is at a speed equal to or higher than a second speed predetermined. In these cases, the phase controller9performs the retard phase control to shift the relative rotation phase to the most retarded phase. In this embodiment, the most retarded phase corresponds to a most retarded closing timing where the IVC of the intake valve Va is arranged within a range defined by a first timing at which the IVC is off the TDC of the piston4of the engine E, the TDC as a reference point, to the advance side by a first crank angle predetermined, and a second timing at which the IVC is off the TDC to the retard side by a second crank angle predetermined. The second speed is lower than the first speed.

FIG.6is a diagram when the intake timing In of the intake valve Va is set to the most retarded closing timing and the exhaust timing of the exhaust valve Vb is set to normal. With the intake timing In of the intake valve Va being set to the most retarded closing timing, the IVC is arranged near the TDC, in other words, between the first timing at which the IVC is advanced from (arranged in the advance direction Sa of) the TDC by the first crank angle (e.g., by five crank angles), and the second timing at which the IVC is retarded from (in the retard direction Sb of) the TDC by the second crank angle (e.g. by five crank angles).

With the valve timing being set as above, the intake valve Va is displaced in the retard direction Sb such that the intake valve Va is closed (shifts to the IVC) around when the piston4reaches the TDC. Concurrently, the intake valve Va is open (shifts to the IVO) around when the piston4is located near the middle between the TDC and the BDC.

Specifically, as the most retarded closing timing, the timing at which the intake valve Va shifts to the closed state (IVC) is more retarded than the retarded closing timing illustrated inFIG.4, and the IVO is arranged “before BDC (BBDC)” with respect to the BDC as a reference point. Thus, the IVC is arranged near the TDC.

When the exhaust valve Vb has shifted to the closed state at the EVC, causing the crankshaft1to rotate by the predetermined amount, the intake valve Va starts to shift to the open state at the IVO. During the compression stroke, the intake valve Va is maintained at the open state and then, around when the piston4reaches the TDC, the intake valve Va shifts to the closed state at the IVC.

With this configuration, the air supplied to the combustion chamber through the intake valve Va until the piston4reaches the BDC from the TDC is to be almost entirely returned to the intake manifold111from the combustion chamber through the intake valve Va before the piston4reaches the TDC from the BDC. As a result, in the exhaust stroke, an oxygen-containing air discharged from the combustion chamber to the exhaust manifold112through the exhaust valve Vb is kept to minimum, and the catalyst113is thus less prone to deteriorate.

As described above, upon receipt of the command to stop the engine E, the phase controller9performs the retard operation control to shift the relative rotation phase between the intermediate member20and the outer case11to the most retarded phase. Further, when the rotational speed of the engine E reaches the lower limit rotational speed N2predetermined during the stopping of the engine E, the phase controller9performs the advance operation control to advance the relative rotation phase as the most retarded phase by displacing the intermediate member20in the same direction as the rotating direction of the outer case11.

FIG.7shows a timing chart. Here, before reaching t1, the engine E runs at the rotational speed predetermined, with the relative rotation phase being at the advance side. In this state, the command to stop the engine E is presumably transmitted (t1). Then, the vehicle decelerates and when the rotational speed of the engine E reaches N1, the phase controller9shifts the relative rotation phase to the most retarded rotation phase that corresponds to the most retarded closing timing of the intake valve Va (t2).

The rotational speed of the engine E is reduced in response to the command to stop the engine E. In this state, when the rotational speed of the engine E reaches the lower limit rotational speed N2, the phase controller9advances the relative rotation phase from the most retarded phase corresponding to the most retarded closing timing (shifts the relative rotation phase in the advance direction Sa from the most retarded phase) (t3). In this advance operation control, the relative rotation phase is not shifted to the advance side but is at least advanced from the most retarded phase. Specifically, the phase controller9controls the relative rotation phase to be suitable for next start of the engine E. A relative rotation phase of this type may correspond to, for example, the relative rotation phase illustrated inFIG.4.

Accordingly, it is possible to appropriately start the engine E upon receipt of a command to start the engine E (t4). When the engine E has started, the phase controller9may preferably shift the relative rotation phase in accordance with a traveling state of the vehicle (in an example ofFIG.7, the phase controller9performs the advance operation control at t5). The phase controller may also perform the retard operation control in accordance with the traveling state of the vehicle.

Here, the phase controller9may be configured, during the stopping of the engine E, to switch between an eco mode not to perform the advance operation control and a torque mode to perform the advance operation control. The eco mode not to perform the advance operation control during the stopping of the engine E is a low fuel consumption travel mode where a reduction in amount of fuel used in the engine E is prioritized over a response (drivability) of the vehicle. Switching between the eco mode and the torque mode may be executed by a user operating a touch panel or a button, or may be automatically executed based on a travel scene of the vehicle. When the mode switching is automatically executed based on the travel scene of the vehicle, the vehicle presumably is in the torque mode while, for example, traveling on a highway, and is in the eco mode while traveling on a general road.

In the case above, even when, in response to the command to stop the engine E, the rotational speed of the engine E is reduced until reaching the lower limit rotational speed N2, the phase controller9does not advance the relative rotation phase from the most retarded phase as the most retarded closing timing (does not shift the relative rotation phase in the advance direction Sa from the most retarded phase). Thus, on receipt of the command to start the engine E next, the phase controller9is to perform the advance operation control. This may deteriorate the response until the vehicle starts to travel, but blocks the supply of fresh air to the catalyst. Accordingly, the catalyst is less prone to deteriorate while enabling the low fuel consumption travel.

On the other hand, in the torque mode to perform the advance operation control during the stopping of the engine E, the response (drivability) of the vehicle is prioritized over the reduction in amount of fuel used in the vehicle. In this case, as described above, when the rotational speed of the engine E reaches the lower limit rotational speed N2, the phase controller9may preferably advance the relative rotation phase from the most retarded phase as the most retarded closing timing (shift the relative rotation phase in the advance direction Sa from the most retarded phase).

The phase controller9may be configured to perform the advance operation control not only when the rotational speed of the engine E is equal to or lower than the lower limit rotational speed N2, but also upon receipt of a request to open a throttle and when the rotational speed of the engine E is equal to or lower than the lower limit rotational speed N2. The request to open the throttle is a command for the driver to operate the accelerator pedal (or an accelerator lever) to open the throttle (not illustrated) of the engine E. The request is detected by the accelerator pedal sensor147, which makes clear that the driver has an intention of starting the engine E. Accordingly, when the request to open the throttle has been detected by the accelerator pedal sensor147and when the rotational speed of the engine E has been equal to or lower than the lower limit rotational speed N2, the phase controller9may perform the advance operation control.

Other Embodiments

In the foregoing embodiment, the most retarded phase corresponds to the most retarded closing timing where the IVC of the intake valve Va is arranged within the range defined by the first timing at which the IVC is off the TDC of the piston4of the engine E, the TDC as the reference point, to the advance side by the first crank angle predetermined, and the second timing at which the IVC is off the TDC to the retard side by the second crank angle predetermined. The most retarded phase may not correspond to the most retarded closing timing, but may be a retarded phase advanced from the most retarded closing timing. The most retarded closing timing may be arranged within a range defined by the TDC of the piston4and the first timing at which the IVC is off the TDC to the advance side by the first crank angle predetermined, or may be arranged within a range defined by the TDC of the piston4and the second timing at which the IVC is off the TDC to the retard side by the second crank angle predetermined. The first crank angle and the second crank angle may be equal to each other, the first crank angle may be greater than the second crank angle, or the second crank angle may be greater than the first crank angle.

In the foregoing embodiment, the command to stop the engine E corresponds to the intermittent stop command to temporarily stop the operation of the engine E during the travel of the vehicle. Alternatively, the command to stop the engine E may not be the intermittent stop command to temporarily stop the vehicle, but may be a command to park the vehicle. The command to stop the engine E may be an idling stop command to temporarily stop the engine E of the vehicle while waiting for a traffic light.

In the foregoing embodiment, the phase controller9is configured, during the stopping of the engine E, to switch between the eco mode not to perform the advance operation control and the torque mode to perform the advance operation control. Alternatively, the phase controller9may be configured, during the stopping of the engine E, not to switch to the eco mode in which the advance operation control is not performed.

In the foregoing embodiment, upon receipt of the request to open the throttle and when the rotational speed of the engine E is equal to or lower than the lower limit rotational speed, the phase controller9performs the advance operation control. Alternatively, even when the rotational speed of the engine E is higher than the lower limit rotational speed, upon receipt of the request to open the throttle, the phase controller9may perform the advance operation control.

This disclosure is applicable to a valve opening and closing range control device.

A valve opening and closing timing control device includes: a driving-side rotating body configured to rotate about a rotating shaft core synchronously with a crankshaft of an internal combustion engine; a driven-side rotating body located inside the driving-side rotating body and coaxially with the rotating shaft core, and configured to rotate integrally with a camshaft for opening and closing an intake valve of the internal combustion engine; a phase adjusting mechanism configured to set a relative rotation phase between the driving-side rotating body and the driven-side rotating body by a driving force of an electric motor; and a phase controller configured, upon receipt of a command to stop the internal combustion engine, to perform retard operation control to shift the relative rotation phase to a most retarded phase by displacing the driven-side rotating body in a direction opposite to a rotating direction of the driving-side rotating body, and configured, when rotational speed of the internal combustion engine reaches a lower limit rotational speed predetermined during stopping of the internal combustion engine, to perform advance operation control to advance the relative rotation phase as the most retarded phase by displacing the driven-side rotating body in a direction same as the rotating direction of the driving-side rotating body.

With this configuration, for example, when the retard operation control is performed in response to the command to stop the internal combustion engine, in a case of the user's “change of mind”, the internal combustion engine needs to restart. Examples of the user's change of mind include a case where the user changes his or her mind to overtake a preceding vehicle with his or her foot off from the accelerator. With the configuration described above, when the rotational speed of the internal combustion engine has reached the lower limit rotational speed predetermined during the stopping of the internal combustion engine, the valve opening and closing timing control device performs the advance operation control to advance the relative rotation phase between the driving-side rotating body and the driven-side rotating body so as to be prepared for restart of the internal combustion engine. Thus, the response delay (delay in response to the request to restart the internal combustion engine) is less prone to occur.

Further, in the valve opening and closing timing control device, the most retarded phase preferably corresponds to the most retarded closing timing where the closing of the intake valve is arranged within the range defined by the first timing at which the closing timing is off a top dead center of the piston of the internal combustion engine, the top dead center as the reference point, to the advance side by the first crank angle predetermined, and the second timing at which the closing timing is off the top dead center to the retard side by the second crank angle predetermined.

With this configuration, when the supply of fuel is stopped in response to the command to stop the internal combustion engine, the valve opening and closing timing control device performs the retard operation control to shift the relative rotation phase between the driving-side rotating body and the driven-side rotating body to the most retarded phase corresponding to the most retarded closing timing of the intake valve, so as to block the supply of fresh air to the catalyst in the exhaust flow path of the internal combustion engine. Accordingly, the catalyst is less prone to deteriorate.

In the valve opening and closing timing control device, the command to stop the internal combustion engine corresponds to the intermittent stop command to temporarily stop the operation of the internal combustion engine during the travel of a vehicle.

With this configuration, the valve opening and closing timing control device is applicable to a hybrid vehicle having a typically called intermittent idling stop function to repeatedly operate and stop the internal combustion engine while traveling in response to, for example, the speed of the vehicle or an output torque required of the internal combustion engine. Then, as described above, the delay in response to the command to restart the internal combustion engine is less prone to occur.

In the valve opening and closing timing control device, during the stopping of the internal combustion engine, the phase controller preferably switches between the eco mode not to perform the advance operation control and the torque mode to perform the advance operation control.

With this configuration, in the eco mode, the reduction in fuel consumption is prioritized over the delay in response to the command to restart the internal combustion engine, and in the torque mode, the reduction in delay in response to the command to restart the internal combustion engine is prioritized over the reduction in fuel consumption. Accordingly, the driving condition is provided to meet the users' request.

In the valve opening and closing timing control device, the phase controller preferably performs the advance operation control upon receipt of the request to open the throttle and when the rotational speed of the internal combustion engine is equal to or lower than the lower limit rotational speed.

With this configuration, upon receipt of the command to stop the internal combustion engine in addition to the request to open the throttle, it is highly likely that the internal combustion engine needs to restart. Thus, this configuration facilitates smooth restart of the internal combustion engine.