Valve timing control apparatus of internal combustion engine

In a valve timing control apparatus, phase-retard and phase-advance hydraulic chambers are defined among a plurality of shoes formed in a housing and a plurality of vanes formed integral with a rotor fixed to a camshaft. The rotor has a large-diameter portion formed between a first group of adjacent vanes and a small-diameter portion formed between a second group of adjacent vanes. The innermost end of a shoe of the shoes, opposed to the outer peripheral surface of the small-diameter portion, is configured to protrude radially inward rather than the innermost end of a shoe of the shoes, opposed to the outer peripheral surface of the large-diameter portion. A lock pin is located in the large-diameter portion of the rotor, whereas a lock hole, with which the lock pin slides into and out of engagement, is located in the inner face of a sprocket.

TECHNICAL FIELD

The present invention relates to a valve timing control apparatus of an internal combustion engine for variably controlling valve timing of an engine valve, such as an intake valve and/or an exhaust valve, depending on an engine operating condition.

BACKGROUND ART

In recent years, there have been proposed and developed various hydraulically-operated vane member equipped variable valve timing control devices, capable of locking a vane member at an intermediate position between a maximum phase-advance position and a maximum phase-retard position by means of a lock mechanism. One such variable valve timing control device has been disclosed in Japanese Patent Provisional Publication No. 2010-537120 (hereinafter is referred to as “JP2010-537120”), corresponding to U.S. Pat. No. 7,874,274, issued on Jan. 25, 2011. In the valve timing control device disclosed in JP2010-537120, a large-diameter rotor is rotatably accommodated in a housing, and radially-outward spring-loaded five vanes are installed in respective vane grooves in the outer periphery of the rotor. Also provided is a lock mechanism arranged between the rotor and a front plate (a first side cover). The lock mechanism is comprised of two slidable lock pins held in respective accommodation bores of the rotor, and two lock holes (two lock-pin receptacles) formed in the front plate so as to permit sliding movement of the lock pin into and out of engagement with the associated lock hole.

As discussed above, in the valve timing control device disclosed in JP2010-537120, the lock pins are installed on the rotor rather than the respective vanes. This contributes to a reduction in circumferential thickness of each of the vanes, thereby enlarging a relative-rotation angle of a camshaft (the rotor) relative to an engine crankshaft (the housing with a chain wheel or a timing sprocket).

SUMMARY OF THE INVENTION

However, in the valve timing control device described in JP2010-537120, for the purpose of ensuring the accommodation bores, in which the lock pins are slidably accommodated, the outside diameter of the rotor has to be expanded. Owing to the expanded outside diameter of the rotor, the outside diameter of the housing also has to be expanded. Otherwise, the radial length of each of the vanes is undesirably limited, thereby reducing pressure-receiving surface areas of both side faces of the vane, facing respective phase-change chambers, namely, a phase-retard chamber and a phase-advance chamber. This results in a deteriorated conversion responsiveness for the relative-rotation phase of the camshaft (the rotor) relative to the crankshaft (the housing).

Accordingly, it is an object of the invention to provide a valve timing control apparatus of an internal combustion engine capable of ensuring adequate pressure-receiving surface areas of vanes, while enlarging a relative-rotation angle of a rotor (a camshaft) relative to a housing (a crankshaft).

In order to accomplish the aforementioned and other objects of the present invention, a valve timing control apparatus of an internal combustion engine, comprises a cylindrical housing having a plurality of shoes protruding radially inward from an inner peripheral surface of the housing, a vane rotor having a rotor adapted to be fixedly connected to a camshaft and a plurality of radially-extending vanes formed on an outer periphery of the rotor for partitioning a working-fluid chamber of the housing by the shoes and the vanes to define phase-advance hydraulic chambers and phase-retard hydraulic chambers, an axially-slidable locking member located in one of the rotor and the housing, and a lock hole located in the other of the rotor and the housing, for restricting rotary motion of the vane rotor relative to the housing with the locking member engaged with the lock hole, wherein the rotor has a large-diameter portion formed between a first group of adjacent vanes of the plurality of vanes of the rotor and a small-diameter portion formed between a second group of adjacent vanes of the plurality of vanes of the rotor, wherein an innermost end of a shoe of the plurality of shoes, opposed to an outer peripheral surface of the small-diameter portion, is configured to protrude radially inward rather than an innermost end of a shoe of the plurality of shoes, opposed to an outer peripheral surface of the large-diameter portion, and wherein the one of the locking member and the lock hole, located in the rotor, is arranged in an area except the small-diameter portion of the rotor.

According to another aspect of the invention, a valve timing control apparatus of an internal combustion engine, comprises a cylindrical housing having a plurality of shoes protruding radially inward from an inner peripheral surface of the housing, a vane rotor having a rotor adapted to be fixedly connected to a camshaft and a plurality of radially-extending vanes formed on an outer periphery of the rotor for partitioning a working-fluid chamber of the housing by the shoes and the vanes to define phase-advance hydraulic chambers and phase-retard hydraulic chambers, an axially-slidable locking member located in the rotor, a lock hole located in the housing to be opposed to the locking member, for restricting rotary motion of the vane rotor relative to the housing with the locking member engaged with the lock hole, and a plurality of seal members attached to respective innermost ends of the plurality of shoes and kept in sliding-contact with the outer periphery of the rotor, wherein the rotor has a large-diameter portion and a small-diameter portion, wherein innermost ends of the plurality of shoes are respectively configured to protrude so as to be substantially conformable to outside diameters of the large-diameter portion and the small-diameter portion, thereby enabling the seal members to be kept in sliding-contact with outer peripheral surfaces of the large-diameter portion and the small-diameter portion, and wherein the locking member is located in the large-diameter portion.

According to a further aspect of the invention, a valve timing control apparatus of an internal combustion engine, comprises a cylindrical housing having a plurality of shoes protruding radially inward from an inner peripheral surface of the housing, a vane rotor having a rotor adapted to be fixedly connected to a camshaft and a plurality of radially-extending vanes formed on an outer periphery of the rotor for partitioning a working-fluid chamber of the housing by the shoes and the vanes to define phase-advance hydraulic chambers and phase-retard hydraulic chambers, an axially-slidable locking member located in the rotor, and an abutment portion located in the housing, for restricting rotary motion of the vane rotor relative to the housing with the locking member engaged with the abutment portion, wherein the phase-advance hydraulic chambers and the phase-retard hydraulic chambers are classified into a hydraulic chamber configured to provide a relatively large pressure-receiving surface area for a first group of circumferentially-opposed adjacent vanes of the plurality of vanes and a hydraulic chamber configured to provide a relatively small pressure-receiving surface area for a second group of circumferentially-opposed adjacent vanes of the plurality of vanes, and wherein the locking member is located in a circumferential portion of the rotor, facing the hydraulic chamber configured to provide the relatively small pressure-receiving surface area.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, particularly toFIGS. 1-3, the valve timing control apparatus of the embodiment is exemplified in a phase control apparatus which is applied to an intake-valve side of an internal combustion engine.

As shown inFIGS. 1-3, the valve timing control apparatus includes a timing sprocket1driven by an engine crankshaft via a timing chain and serving as a driving rotary member, an intake-valve side camshaft2arranged in a longitudinal direction of the engine and configured to be relatively rotatable with the sprocket1, a phase-change mechanism3installed between sprocket1and camshaft2to change a relative angular phase of camshaft2to sprocket1(the crankshaft), a lock mechanism4provided for locking or holding the phase-change mechanism3at a predetermined intermediate-phase angular position between a maximum phase-advance position and a maximum phase-retard position, and a hydraulic circuit5provided for hydraulically operating phase-change mechanism3and lock mechanism4independently of each other.

Sprocket1is constructed as a rear cover that hermetically closes the rear end opening of a housing (described later). Sprocket1is formed into a thick-walled disc-shape. The outer periphery of sprocket1has a toothed portion1aon which the timing chain is wound. Sprocket1is also formed with a supported bore6(a central through hole), which is rotatably supported on the outer periphery of one axial end2aof camshaft2. Also, sprocket1has circumferentially equidistant-spaced four female-screw threaded holes1bformed on its outer peripheral side.

Camshaft2is rotatably supported on a cylinder head (not shown) via cam bearings (not shown). Camshaft2has a plurality of cams integrally formed on its outer periphery and spaced apart from each other in the axial direction of camshaft2, for operating engine valves (i.e., intake valves). Camshaft2has a female-screw threaded hole2bformed along the camshaft center at the axial end2a.

As shown inFIGS. 1-3, phase-change mechanism3is comprised of a housing7, a vane rotor9, four phase-retard hydraulic chambers (simply, four phase-retard chambers)11,11,11,11and four phase-advance hydraulic chambers (simply, four phase-advance chambers)12,12,12,12. Housing7is integrally connected to the sprocket1in the axial direction. Vane rotor9is fixedly connected to the axial end of camshaft2by means of a cam bolt8screwed into the female screw-threaded hole2bof the axial end of camshaft2, and serves as a driven rotary member rotatably enclosed in the housing7. Housing7has radially-inward protruded four shoes (described later) integrally formed on the inner peripheral surface of housing7. Four phase-retard chambers11and four phase-advance chambers12are defined by partitioning the working-fluid chamber (the internal space) of housing7by four shoes of housing7and four vanes (described later) of vane rotor9.

Housing7includes a cylindrical housing body10, a front plate13, and the sprocket1serving as the rear cover for the rear opening end of housing7. Housing body10is formed as a cylindrical hollow housing member, opened at both ends in the two opposite axial directions. Front plate13is produced by pressing. Front plate13is provided for hermetically covering the front opening end of housing body10.

Housing body10is made of sintered alloy materials, such as iron-based sintered alloy materials. Housing body10has four radially-inward protruded shoes10a,10b,10c, and10d, integrally formed on its inner periphery. Four bolt insertion holes, namely axial through holes10e,10e,10e,10eare formed in respective shoes10a-10d.

Front plate13is formed as a thin-walled metal disc. Front plate13is formed with a central through hole13a. Also, front plate13has four circumferentially equidistant-spaced bolt insertion holes, namely axial through holes13b,13b,13b,13b.

Sprocket1, housing body10, and front plate13are integrally connected to each other by fastening them together with four bolts14,14,14,14penetrating respective bolt insertion holes (i.e., four through holes13bformed in the front plate13and four through holes10eformed in respective shoes10a-10d) and screwed into respective female-screw threaded holes1bof sprocket1.

Vane rotor9is formed of a metal material. Vane rotor9is comprised of a rotor15fixedly connected to the axial end of camshaft2by means of the cam bolt8, and four radially-extending vane blades (simply, vanes)16a,16b,16c, and16d, formed on the outer periphery of rotor15and circumferentially spaced apart from each other by approximately 90 degrees.

Rotor15is formed into an axially-thick-walled, different-diameter deformed disc-shape. Rotor15is integrally formed with a central bolt insertion hole (an axial through hole). A substantially circular recessed bearing surface15b, on which the head of cam bolt8is seated, is formed in the front end face of rotor15.

Regarding the shape of rotor15, in particular, the lateral cross-sectional configuration of rotor15, the contour between the first vane16aand the fourth vane16dcircumferentially adjacent to each other is configured as a small-diameter portion15c, whereas the contour between the second vane16band the third vane16ccircumferentially adjacent to each other is also configured as a small-diameter portion15d. The small-diameter pair (i.e., the first small-diameter portion15cand the second small-diameter portion15d) serves as a base circle. In contrast, the contour between the first vane16aand the second vane16bcircumferentially adjacent to each other is configured as a second large-diameter portion15fhaving an outside diameter greater than the first and second small-diameter portions15c-15d. Also, the contour between the third vane16cand the fourth vane16dcircumferentially adjacent to each other is configured as a first large-diameter portion15ehaving an outside diameter greater than the first and second small-diameter portions15c-15d.

First small-diameter portion15cand second small-diameter portion15dare arranged at angular positions circumferentially spaced apart from each other by approximately 180 degrees. That is, first and second small-diameter portions15c-15dare arranged to be diametrically opposed to each other. The outer peripheral surface of each of first and second small-diameter portions15c-15dis formed into a circular-arc shape having the same radius of curvature.

On the other hand, first and second large-diameter portions15e-15fare arranged at angular positions circumferentially spaced apart from each other by approximately 180 degrees. That is, first and second large-diameter portions15e-15fare also arranged to be diametrically opposed to each other. The outer peripheral surface of each of first and second large-diameter portions15e-15fis formed into a circular-arc shape having the same radius of curvature. However, the outside diameter of the outer peripheral surfaces of large-diameter portions15e-15fis configured to be one-size greater than that of small-diameter portions15c-15d.

Therefore, the first shoe10a, whose tip faces the outer peripheral surface of first small-diameter portion15c, is formed as a comparatively long, radially-inward protruded partition wall having substantially rectangular side faces. In a similar manner, the second shoe10b, whose tip faces the outer peripheral surface of second small-diameter portion15d, is formed as a comparatively long, radially-inward protruded partition wall having substantially rectangular side faces. In contrast, the third shoe10c, whose tip faces the outer peripheral surface of second large-diameter portion15f, is formed as a comparatively short, radially-inward protruded partition wall having substantially circular-arc side faces. In a similar manner, the fourth shoe10d, whose tip faces the outer peripheral surface of first large-diameter portion15e, is formed as a comparatively short, radially-inward protruded partition wall having substantially circular-arc side faces.

Four shoes10a-10dhave respective axially-elongated seal retaining grooves, formed in their innermost ends (apexes) and extending in the axial direction. Each of four seal retaining grooves of the shoes is formed into a substantially rectangle. Four oil seal members (four apex seals)17a,17a,17a,17a, each having a substantially square lateral cross section, are fitted into respective seal retaining grooves of four shoes10a-10dso as to bring the four apex seals17ainto sliding-contact with the respective outer peripheral surfaces of first and second small-diameter portions15c-15dand first and second large-diameter portions15e-15f. Leaf springs (not shown) are installed in the respective seal retaining grooves of four shoes10a-10d, for permanently biasing the four apex seals of four shoes10a-10dtoward the respective outer peripheral surfaces of first and second small-diameter portions15c-15dand first and second large-diameter portions15e-15f, thereby providing a sealing action between the different-diameter deformed outer peripheral surface of rotor15and the innermost ends (apexes) of shoes10a-10d.

Regarding four vanes16a-16dformed integral with the rotor15and radially extending outward from the outer peripheral surface of rotor15, their entire lengths are dimensioned to be substantially identical to each other. Circumferential widths of four vanes16a-16dare dimensioned to be substantially identical to each other, and thus each of vanes16a-16dis formed into a thin-walled plate. Four vanes16a-16dare disposed in respective internal spaces defined by four shoes10a-10d. In a similar manner to the four shoes10a-10d, four vanes16a-16dhave respective axially-elongated seal retaining grooves, formed in their outermost ends (apexes) and extending in the axial direction. Each of four seal retaining grooves of the vanes is formed into a substantially rectangle. Four oil seal members (four apex seals)17b,17b,17b,17b, each having a substantially square lateral cross section, are fitted into respective seal retaining grooves of four vanes16a-16dso as to bring the four apex seals17binto sliding-contact with the inner peripheral surface of housing body10. Leaf springs (not shown) are installed in the respective seal retaining grooves of four vanes16a-16d, for permanently biasing the four apex seals of four vanes16a-16dtoward the inner peripheral surface of housing body10, thereby providing a sealing action between the inner peripheral surface of housing body10and the outermost ends (apexes) of vanes16a-16d.

As discussed above, apex seals17aof shoes10a-10dand apex seals17bof vanes16a-16dare cooperated with each other to ensure a fluid-tight sealing structure between phase-retard chamber11and phase-advance chamber12.

As shown inFIG. 3, when vane rotor9rotates relative to the housing7(or the sprocket1) in the phase-retard direction, one side face (an anticlockwise side face16e, viewingFIG. 3) of the first vane16ais brought into abutted-engagement with a radially-inward protruding surface formed on one side face (a clockwise side face, viewingFIG. 3) of the opposed first shoe10a, and thus a maximum phase-retard angular position of vane rotor9is restricted. Conversely, as shown inFIG. 5, when vane rotor9rotates relative to the housing7(or the sprocket1) in the phase-advance direction, the other side face (a clockwise side face, viewingFIG. 5) of the first vane16ais brought into abutted-engagement with a radially-inward protruding surface formed on one side face (an anticlockwise side face, viewingFIG. 5) of the opposed third shoe10c, and thus a maximum phase-advance angular position of vane rotor9is restricted.

With the first vane16akept in its maximum phase-retard angular position (seeFIG. 3) or with the first vane16akept in its maximum phase-advance angular position (seeFIG. 5), both side faces of each of the other vanes16b-16dare kept in a spaced, contact-free relationship with respective side faces of the associated shoes. Hence, the accuracy of abutment between the vane rotor9and the shoe (i.e., the first shoe10a) can be enhanced, and additionally the speed of hydraulic pressure supply to each of hydraulic chambers11and12can be increased, thus a responsiveness of normal-rotation/reverse-rotation of vane rotor9can be improved.

The previously-discussed four phase-retard chambers11and four phase-advance chambers12are defined by both side faces of each of vanes16a-16dand both side faces of each of shoes10a-10d. Regarding volumetric capacities of phase-retard chambers11and phase-advance chambers12, by virtue of the different-diameter deformed outer peripheral surface of rotor15, the total volumetric capacity of hydraulic chambers11aand12a, located in the area corresponding to the small-diameter portion (each of first and second small-diameter portions15c-15d) of rotor15, is set to be greater than the total volumetric capacity of hydraulic chambers11band12b, located in the area corresponding to the large-diameter portion (each of first and second large-diameter portions15e-15f). Thus, the pressure-receiving surface area of each of side faces16e-16hof vanes16a-16d, facing hydraulic chambers11aand12alocated in the area corresponding to the small-diameter portion (each of first and second small-diameter portions15c-15d), is set to be greater than that of each of side faces of vanes16a-16d, facing hydraulic chambers11band12blocated in the area corresponding to the large-diameter portion (each of first and second large-diameter portions15e-15f).

Each of phase-retard chambers11is configured to communicate with the hydraulic circuit5(described later) via the first communication hole11cformed in the rotor15. In a similar manner, each of phase-advance chambers12is configured to communicate with the hydraulic circuit5via the second communication hole12cformed in the rotor15.

Lock mechanism4is provided for holding or locking an angular position of vane rotor9relative to housing7at an intermediate-phase angular position (corresponding to the angular position of vane rotor9inFIG. 4) between the maximum phase-retard angular position (seeFIG. 3) and the maximum phase-advance angular position (seeFIG. 4).

That is, as shown in FIGS.2and6-11, lock mechanism4is comprised of a first lock hole24, a second lock hole25, a third lock hole26, a first lock pin27, a second lock pin28, a third lock pin29, and a lock-unlock passage (simply, a lock passage)20. The first, second and third lock holes24-26(serving as abutment portions) are disposed in the inner face1cof sprocket1, and arranged at respective given circumferential positions. The first lock pin27(serving as a substantially cylindrical locking member engaged with the associated abutment portion) is operably disposed in the first large-diameter portion15eof rotor15such that movement of first lock pin27into and out of engagement with the first lock hole24is permitted. The second lock pin28(serving as a substantially cylindrical locking member) is operably disposed in the second large-diameter portion15fof rotor15such that movement of second lock pin28into and out of engagement with the second lock hole25is permitted. In a similar manner, the third lock pin29(serving as a substantially cylindrical locking member) is operably disposed in the second large-diameter portion15fof rotor15such that movement of third lock pin29into and out of engagement with the third lock hole26is permitted. The first, second and third lock pins27-29are arranged at respective given circumferential positions of rotor15. Lock passage20is provided for disengagement of the first lock pin27from the first lock hole24and for disengagement of the second lock pin28from the second lock hole25and for disengagement of the third lock pin29from the third lock hole26.

As seen in FIGS.2and6-11, the first lock hole24is arranged on the side of first large-diameter portion15eof rotor15and formed into a cocoon shape (or a circular-arc circumferentially-elongated groove) extending in the circumferential direction of sprocket1. The first lock hole24is formed in the inner face1cof sprocket1and arranged at an intermediate position somewhat displaced toward the phase-advance side with respect to the maximum phase-retard angular position of vane rotor9. Additionally, the first lock hole24is formed as a two-stage stepped hole whose bottom face lowers stepwise from the phase-retard side to the phase-advance side. The first lock hole24(i.e., the two-stage stepped groove) is configured to serve as a lock guide groove.

That is, as seen inFIGS. 6-11, assuming that the inner face1cof sprocket1is regarded as an uppermost level, the first lock guide groove (the two-stage stepped groove)24is configured to gradually lower from the first bottom face24ato the second bottom face24b, in that order. Each of inner faces, vertically extending from respective bottom faces24a-24bon the phase-retard side, is formed as an upstanding wall surface (viewingFIGS. 6-11). The inner face24c, vertically extending from the second bottom face24bon the phase-advance side, is also formed as an upstanding wall surface (viewingFIGS. 6-11).

As best seen inFIG. 11, a further movement of first lock pin27in the phase-advance direction is restricted by a combined locking action of second and third lock pins28-29(that is, by abutment of the outer periphery (the edge) of the tip28aof second lock pin28with the upstanding inner face25cand by abutment of the outer periphery (the edge) of the tip29aof third lock pin29with the upstanding inner face26b) under a specified state where the outer periphery of the tip27aof first lock pin27is slightly spaced apart from the upstanding inner face24cvertically extending from the second bottom face24b.

As seen inFIGS. 3-5, the second lock hole25is formed into an elliptic or oval shape (a circumferentially-elongated groove) extending in the circumferential direction of sprocket1, and dimensioned to be shorter than the circumferential length of first lock hole24. In a similar manner to the first lock hole24, the second lock hole25is formed as a two-stage stepped hole whose bottom face lowers stepwise from the phase-retard side to the phase-advance side. The second lock hole25(i.e., the two-stage stepped groove) is configured to serve as a second lock guide groove. That is, assuming that the inner face1cof sprocket1is regarded as the uppermost level, the second lock guide groove (the two-stage stepped groove)25is configured to gradually lower from the first bottom face25ato the second bottom face25b, in that order. Each of inner faces, vertically extending from respective bottom faces25a-25bon the phase-retard side, is formed as an upstanding wall surface (viewingFIGS. 6-11). The inner face25c, vertically extending from the second bottom face25bon the phase-advance side, is also formed as an upstanding wall surface (viewingFIGS. 6-11).

The second bottom face25bis formed as a somewhat circumferentially-elongated recessed groove extending to the phase-advance side. With the tip28aof second lock pin28engaged with the second bottom face25b, the somewhat circumferentially-elongated second bottom face25bpermits a slight movement of second lock pin28in the phase-advance direction (seeFIGS. 10-11).

The third lock hole26is formed into a cylindrical-hollow shape having an inside diameter greater than an outside diameter of the tip29aof third lock pin29so as to permit a slight circumferential movement of the tip29aof third lock pin29engaged with the third lock hole26. Also, the third lock hole26is formed in the inner face1cof sprocket1and arranged at an intermediate position somewhat displaced toward the phase-advance side with respect to the maximum phase-retard angular position of vane rotor9.

Additionally, the depth of the bottom face26aof third lock hole26is dimensioned or set to be almost the same depth as the second bottom face24bof first lock hole24and also dimensioned to be almost the same depth as the second bottom face25bof second lock hole25. Hence, in the presence of movement of third lock pin29into engagement with the third lock hole26owing to rotary motion of the vane rotor9in the phase-advance direction, the tip29aof third lock pin29is brought into abutted-engagement with the bottom face26aof third lock hole26. At the same time, the outer periphery (the edge) of the tip29aof third lock pin29is brought into abutted-engagement with the upstanding inner face26bof third lock hole26, and whereby rotary motion of vane rotor9in the phase-retard direction is restricted.

Regarding the relative-position relationship of first, second, and third lock holes24-26formed in the inner face1cof sprocket1, in a phase wherein the first lock pin27is brought into engagement with the first bottom face24aof first lock hole24(seeFIG. 7), and in a phase just after the first lock pin27has been brought into engagement with the second bottom face24b(seeFIG. 8), the axial end face of the tip28aof second lock pin28and the axial end face of the tip29aof third lock pin29are still kept in abutted-engagement with the inner face1cof sprocket1.

Thereafter, as seen inFIG. 9, when, owing to a slight rotary motion of vane rotor9in the phase-advance direction, the axial end face of the tip27aof first lock pin27slides along the second bottom face24bof first lock hole24and then reaches a substantially midpoint of the second bottom face24b, the tip28aof second lock pin28is brought into abutted-engagement with the first bottom face25aof second lock hole25.

As seen inFIG. 10, when the tip27aof first lock pin27further moves in the phase-advance direction, while being kept in sliding-contact with the second bottom face24b, the tip28aof second lock pin28slides out of engagement with the first bottom face25aof second lock hole25but slides into abutted-engagement with the second bottom face25b. At this time, the axial end face of the tip29aof third lock pin29slides in the phase-advance direction, while being still kept in abutted-engagement with the inner face1cof sprocket1.

Thereafter, when, owing to a further rotary motion of vane rotor9in the phase-advance direction, the first lock pin27kept in abutted-engagement with the second bottom face24band the second lock pin28kept in abutted-engagement with the second bottom face25bfurther move in the same phase-advance direction, the tip29aof third lock pin29slides into engagement with the third lock hole26(seeFIG. 11). In this manner, the relative-position relationship among first, second and third lock holes24-26is preset. With three lock pins27-29engaged with respective lock holes24-26, the circumferentially-opposed outer peripheral edges of second and third lock pins28-29, circumferentially opposed to each other, abut with the circumferentially-opposed upstanding inner faces25cand26bof second and third lock holes25-26, respectively, such that the specified area of the inner face1cof sprocket1, ranging between the two upstanding inner faces25cand26b, is sandwiched with the two lock pins28-29.

Briefly speaking, as can be seen from the cross sections ofFIGS. 6-11, according to rotary motion of vane rotor9relative to sprocket1from the phase-retard position toward the phase-advance position, the first lock pin27is brought into abutted-engagement with the first and second bottom faces24a-24b, one-by-one (in a stepwise manner) and further moves in the phase-advance direction, while being kept in sliding-contact with the second bottom face24b. From the middle of sliding movement of the tip27aof first lock pin27along the second bottom face24b, the second lock pin28slides into engagement with the second lock hole25and then brought into abutted-engagement with the first and second bottom faces25a-25b, one-by-one (in a stepwise manner). Thereafter, the third lock pin29is sequentially brought into engagement with the third lock hole26. As discussed above, the first and second lock guide groove structures (i.e., first and second holes24-25) and the third lock hole26permit normal rotation of vane rotor9relative to sprocket1in the phase-advance direction, but restrict or prevent reverse-rotation (counter-rotation) of vane rotor9relative to sprocket1in the phase-retard direction by virtue of a five-stage ratchet action in total. Finally, the angular position of vane rotor9relative to sprocket1is held or locked at the intermediate-phase angular position (seeFIG. 4) between the maximum phase-retard angular position (seeFIG. 3) and the maximum phase-advance angular position (seeFIG. 5).

As best seen inFIGS. 2-6, the first lock pin27is slidably disposed in a first lock-pin hole31a(an axial through hole) formed in the first large-diameter portion15eor15. The first lock pin27is contoured as a stepped shape, comprised of the comparatively small-diameter tip27a, a comparatively large-diameter cylindrical-hollow basal portion27bintegrally formed continuously with the rear end of small-diameter tip27a, and a stepped pressure-receiving surface27cdefined between the tip27aand the large-diameter cylindrical-hollow basal portion27b. The end face of tip27ais formed as a flat face, which can be brought into abutted-engagement (exactly, into wall-contact) with each of bottom faces24aand24b.

The first lock pin27is permanently biased in a direction of movement of first lock pin27into engagement with the first lock hole24by a spring force of a first spring36(biasing means). The first spring36is disposed between the bottom face of an axial spring bore formed in the large-diameter cylindrical-hollow basal portion27bin a manner so as to axially extend from the rear end face and the inner wall surface of front cover13under preload.

The first lock pin27is also configured such that hydraulic pressure from a first unlocking pressure-receiving chamber32, which chamber is formed in the rotor15, is applied to the stepped pressure-receiving surface27c. The applied hydraulic pressure causes a backward movement of first lock pin27against the spring force of first spring36, and thus the first lock pin27is disengaged from the first lock hole24.

In a similar manner to the first lock pin27, the second lock pin28is slidably disposed in a second lock-pin hole31b(an axial through hole) formed in the second large-diameter portion15fof rotor15. The second lock pin28is contoured as a stepped shape, comprised of the comparatively small-diameter tip28a, a comparatively large-diameter cylindrical-hollow basal portion28bintegrally formed continuously with the rear end of small-diameter tip28a, and a stepped pressure-receiving surface28cdefined between the tip28aand the large-diameter cylindrical-hollow basal portion28b. The end face of tip28ais formed as a flat face, which can be brought into abutted-engagement (exactly, into wall-contact) with each of bottom faces25aand25b.

The second lock pin28is permanently biased in a direction of movement of second lock pin28into engagement with the second lock hole25by a spring force of a second spring37(biasing means). The second spring37is disposed between the bottom face of an axial spring bore formed in the large-diameter cylindrical-hollow basal portion28bin a manner so as to axially extend from the rear end face and the inner wall surface of front cover13under preload.

The second lock pin28is also configured such that hydraulic pressure from a second unlocking pressure-receiving chamber33, which chamber is formed in the rotor15, is applied to the stepped pressure-receiving surface28c. The applied hydraulic pressure causes a backward movement of second lock pin28against the spring force of second spring37, and thus the second lock pin28is disengaged from the second lock hole25.

In a similar manner to the first and second lock pins27-28, the third lock pin29is slidably disposed in a third lock-pin hole31c(an axial through hole) formed in the second large-diameter portion15fof rotor15. The third lock pin29is contoured as a stepped shape, comprised of the comparatively small-diameter tip29a, a comparatively large-diameter cylindrical-hollow basal portion29bintegrally formed continuously with the rear end of small-diameter tip29a, and a stepped pressure-receiving surface29cdefined between the tip29aand the large-diameter cylindrical-hollow basal portion29b. The end face of tip29ais formed as a flat face, which can be brought into abutted-engagement (exactly, into wall-contact) with the bottom face26a.

The third lock pin29is permanently biased in a direction of movement of third lock pin29into engagement with the third lock hole26by a spring force of a third spring38(biasing means). The third spring38is disposed between the bottom face of an axial spring bore formed in the large-diameter cylindrical-hollow basal portion29bin a manner so as to axially extend from the rear end face and the inner wall surface of front cover13under preload.

The third lock pin29is also configured such that hydraulic pressure from a third unlocking pressure-receiving chamber34, which chamber is formed in the rotor15, is applied to the stepped pressure-receiving surface29c. The applied hydraulic pressure causes a backward movement of third lock pin29against the spring force of third spring38, and thus the third lock pin29is disengaged from the third lock hole26.

Returning toFIG. 1, the rear end of each of first, second, and third lock-pin holes31a-31cis configured to be opened to the atmosphere via a breather39, thereby ensuring a smooth sliding movement of each of lock pins27,28and29.

As shown inFIG. 1, hydraulic circuit5includes a phase-retard passage18, a phase-advance passage19, lock passage20, an oil pump40(serving as a fluid-pressure supply source), and a single electromagnetic directional control valve41. Phase-retard passage18is provided for fluid-pressure supply-and-exhaust for each of phase-retard chambers11via the first communication hole11c. Phase-advance passage19is provided for fluid-pressure supply-and-exhaust for each of phase-advance chambers12via the second communication hole12c. Lock passage20is provided for fluid-pressure supply-and-exhaust for each of first, second, and third unlocking pressure-receiving chambers32-34. Oil pump40is provided for supplying working fluid pressure to at least one of phase-retard passage18and phase-advance passage19, and also provided for supplying working fluid pressure to lock passage20. Single electromagnetic directional control valve41is provided for switching between phase-retard passage18and phase-advance passage19, and also provided for switching between working-fluid supply to lock passage20and working-fluid exhaust from lock passage20.

One end of phase-retard passage18and one end of phase-advance passage19are connected to respective ports (not shown) of electromagnetic directional control valve41. The other end of phase-retard passage18is configured to communicate with each of phase-retard chambers11via an axial passage portion18aformed in the camshaft2and the first communication hole11cformed in the rotor15. The other end of phase-advance passage19is configured to communicate with each of phase-advance chambers12via an axially-extending but partly-radially-bent passage portion19aformed in the camshaft2and the second communication hole12cformed in the rotor15.

As shown inFIGS. 1-2, one end of lock passage20is connected to a lock port (not shown) of electromagnetic directional control valve41. The other end of lock passage20, serving as a fluid-passage portion20a, is formed in the camshaft to be bent from the radial direction to the axial direction. The fluid-passage portion20aof lock passage20is configured to communicate with respective unlocking pressure-receiving chambers32-34via branch oil holes formed in the rotor15and branching away.

In the shown embodiment, an internal gear rotary pump, such as a trochoid pump having inner and outer rotors, is used as the oil pump40driven by the engine crankshaft. During operation of oil pump40, when the inner rotor is driven, the outer rotor also rotates in the same rotational direction as the inner rotor by mesh between the outer-rotor inner-toothed portion and the inner-rotor outer-toothed portion. Working fluid in an oil pan42is introduced through a suction passage into the pump, and then discharged through a discharge passage40a. Part of working fluid discharged from oil pump40is delivered through a main oil gallery M/G to sliding or moving engine parts. The remaining working fluid discharged from oil pump40is delivered to electromagnetic directional control valve41. An oil filter (not shown) is disposed in the downstream side of discharge passage40a. Also, a flow control valve (not shown) is provided to appropriately control an amount of working fluid discharged from oil pump40into discharge passage40a, thus enabling surplus working fluid discharged from oil pump40to be directed via a drain passage43to the oil pan42.

As seen inFIG. 1, electromagnetic directional control valve41is an electromagnetic-solenoid operated, six-port, six-position, spring-offset, proportional control valve. Electromagnetic directional control valve41is comprised of a substantially cylindrical-hollow, axially-elongated valve body (a valve housing), a valve spool (an electrically-actuated valve element) slidably installed in the valve body in a manner so as to axially slide in a very close-fitting bore of the valve body, a valve spring installed inside of one axial end of the valve body for permanently biasing the valve spool in an axial direction, and an electromagnetic solenoid attached to the valve body so as to cause axial sliding movement of the valve spool against the spring force of the valve spring.

Electromagnetic directional control valve41is configured to move the valve spool to either one of six axial positions by the two opposing pressing forces, produced by a spring force of the valve spring and a control current generated from a controller35and flowing through the electromagnetic solenoid coil, so as to change a state of fluid-communication between the discharge passage40aof oil pump40and each of three passages (that is, phase-retard passage18, phase-advance passage19, and lock passage20) and simultaneously change a state of fluid-communication between the drain passage43and each of the three passages18,19, and20, depending on a selected one of the six positions of the valve spool.

As discussed above, electromagnetic directional control valve41is configured to change the path of flow through the directional control valve41by selective switching among the ports depending on a given axial position of the valve spool, determined based on latest up-to-date information about an engine operating condition (e.g., engine speed and engine load), thereby changing a relative angular phase of vane rotor9(camshaft2) to sprocket1(the crankshaft) and also enabling selective switching between locked and unlocked states of lock mechanism4, in other words, selective switching between a locked (engaged) state of lock pins27-29with respective lock holes24-26and an unlocked (disengaged) state of lock pins27-29from respective lock holes24-26. Accordingly, by means of electromagnetic directional control valve41as previously discussed, free rotation of vane rotor9relative to sprocket1can be enabled (permitted) or disabled (restricted) depending on the engine operating condition.

Controller (ECU)35generally comprises a microcomputer. Controller35includes an input/output interface (I/O), memories (RAM, ROM), and a microprocessor or a central processing unit (CPU). The input/output interface (I/O) of controller35receives input information from various engine/vehicle switches and sensors, namely a crank angle sensor (a crank position sensor), an airflow meter, an engine temperature sensor (e.g., an engine coolant temperature sensor), a throttle opening sensor (a throttle position sensor), a cam angle sensor, an oil-pump discharge pressure sensor, and the like. The crank angle sensor is provided for detecting revolution speeds of the engine crankshaft and for calculating an engine speed. The airflow meter is provided for generating an intake-air flow rate signal indicating an actual intake-air flow rate or an actual air quantity. The engine temperature sensor is provided for detecting an actual operating temperature of the engine. The cam angle sensor is provided for detecting latest up-to-date information about an angular phase of camshaft2. The discharge pressure sensor is provided for detecting a discharge pressure of working fluid discharged from the oil pump40. Within controller35, the central processing unit (CPU) allows the access by the I/O interface of input informational data signals from the previously-discussed engine/vehicle switches and sensors, so as to detect the current engine operating condition, and also to generate a control pulse current, determined based on latest up-to-date information about the detected engine operating condition and the detected discharge pressure, to the electromagnetic coil of the solenoid of electromagnetic directional control valve41, for controlling the axial position of the sliding valve spool, thus achieving selective switching among the ports depending on the controlled axial position of the valve spool.

InFIGS. 2-3, a pin denoted by reference sign50is a positioning pin attached onto the inner face1cof sprocket1, whereas an axially-elongated groove denoted by reference sign51is a positioning groove formed in the outer periphery of the first shoe10aof housing body10. When assembling, the positioning pin50of sprocket1is fitted into the positioning groove51of the first shoe10aof housing body10, thus ensuring easy positioning of housing body10relative to the sprocket1.

[Operation of Valve Timing Control Apparatus of Embodiment]

Details of operation of the valve timing control apparatus of the embodiment are hereunder described.

For instance, when an ignition switch has been turned OFF after normal vehicle traveling and thus the engine has stopped rotating, a supply of control current from controller35to the electromagnetic coil of electromagnetic directional control valve41is stopped and thus the solenoid is de-energized. Thus, the valve spool is positioned at the maximum rightward axial position (i.e., the “first position”, in other words, the spring-loaded or spring-offset position) by the spring force of the valve spring. Hence, the discharge passage40acommunicates with both of the phase-retard passage18and the phase-advance passage19, whereas the lock passage20communicates with the drain passage43.

At the same time, oil pump40is placed into an inoperative state, and thus working-fluid supply to phase-retard chamber11or phase-advance chamber12becomes stopped, and also working-fluid supply to each of first, second, and third unlocking pressure-receiving chambers32-34becomes stopped.

That is, when the ignition switch becomes turned OFF under a state where vane rotor9has been placed into a phase-retard angular position by the working-fluid pressure supply to each of phase-retard chambers11during idling before the engine is brought into a stopped state, alternating torque, acting on camshaft2immediately before the engine stops, occurs. In particular, when rotary motion of vane rotor9relative to sprocket1in the phase-advance direction occurs owing to the negative torque of alternating torque acting on camshaft2and thus the angular position of vane rotor9relative to sprocket1reaches the intermediate-phase angular position (seeFIG. 4), the tip27aof first lock pin27, the tip28aof second lock pin28, and the tip29aof third lock pin29are brought into engagement with respective lock holes24-26by the spring forces of first, second, and third springs36-38(seeFIG. 11). As a result of this, the angular position of vane rotor9relative to sprocket1is held or locked at the intermediate-phase angular position (seeFIG. 4) between the maximum phase-retard angular position (seeFIG. 3) and the maximum phase-advance angular position (seeFIG. 5).

More concretely, when a slight rotary motion of vane rotor9relative to sprocket1in the phase-advance direction from the angular position ofFIG. 6to the angular position ofFIG. 7occurs owing to the negative torque of alternating torque acting on camshaft2, the tip27aof first lock pin27is brought into abutted-engagement with the first bottom face24aof first lock hole24. At this time, even when vane rotor9tends to rotate relative to sprocket1in the opposite direction (i.e., in the phase-retard direction) owing to the positive torque of alternating torque acting on camshaft2, such a rotary motion of vane rotor9in the phase-retard direction can be restricted by abutment of the outer periphery (the edge) of the tip27aof first lock pin27with the upstanding stepped inner face vertically extending from the first bottom face24a.

Thereafter, when a further rotary motion of vane rotor9relative to sprocket1in the phase-advance direction occurs owing to the negative torque acting on camshaft2, as shown inFIGS. 7-8, first lock pin27lowers from the first bottom face24ato the second bottom face24bstepwise in the phase-advance direction and thus the tip27aof first lock pin27is brought into abutted-engagement with the second bottom face24b. Then, by virtue of the ratchet action, the tip27aof first lock pin27moves along the second bottom face24bin the phase-advance direction, and then reaches a substantially midpoint of the second bottom face24b. At this time, as shown inFIG. 9, the tip28aof second lock pin28slides into abutted-engagement with the first bottom face25aof second lock hole25.

Thereafter, when vane rotor9further rotates in the phase-advance direction, as shown inFIGS. 9-10, the tip27aof first lock pin27moves to the vicinity of the upstanding inner face24cof first lock hole24. At the same time, the tip28aof second lock pin28is brought into abutted-engagement with the second bottom face25bby virtue of the ratchet action.

When vane rotor9still further rotates in the phase-advance direction owing to the negative torque, as shown inFIGS. 10-11, the tip29aof third lock pin29slides into engagement with the third lock hole26, while first and second lock pins27-28slide in the same direction. Under these conditions, as previously discussed, the circumferentially-opposed outer peripheral edges of second and third lock pins28-29, circumferentially opposed to each other, abut with the circumferentially-opposed upstanding inner faces25cand26bof second and third lock holes25-26, respectively, such that the specified area of the inner face1cof sprocket1, ranging between the two upstanding inner faces25cand26b, is sandwiched with the two lock pins28-29. Hence, vane rotor9can be stably surely held or locked at the intermediate-phase angular position (seeFIG. 4) between the maximum phase-retard angular position and the maximum phase-advance angular position.

Thereafter, immediately after the ignition switch has been turned ON to start up the engine, due to initial explosion (the start of cranking) oil pump40begins to operate. Thus, the discharge pressure of working fluid discharged from oil pump40is delivered to each phase-retard chamber11and each phase-advance chamber12via respective passages18and19. On the other hand, the lock passage20is kept in a fluid-communication relationship with the drain passage43. Thus, first, second, and third lock pins27-29are kept in engagement with respective lock holes24-26by the spring forces of first, second, and third springs36-38.

As previously discussed, the axial position of the valve spool of electromagnetic directional control valve41is controlled by means of controller35depending on latest up-to-date information about the detected engine operating condition and the detected pump discharge pressure. Hence, with the engine at an idle rpm, at which the discharge pressure of working fluid discharged from oil pump40is unstable, the engaged states (locked states) of first, second, and third lock pins27-29are maintained.

After this, immediately before the engine operating condition shifts from the idling condition to a low-speed low-load operating range or a high-speed high-load operating range, a control current is outputted from controller35to the electromagnetic coil of electromagnetic directional control valve41. Thus, the valve spool is slightly displaced against the spring force of the valve spring. The axial position of the valve spool, slightly displaced from the “first position” (the spring-offset position) is referred to as “sixth position”. With the valve spool held at the “sixth position”, fluid communication between the discharge passage40aand the lock passage20becomes established. On the other hand, both of the phase-retard passage18and the phase-advance passage19remain kept in a fluid-communication relationship with the discharge passage40a.

Therefore, working fluid can be supplied via the fluid-passage portion20aof lock passage20to each of first, second, and third unlocking pressure-receiving chambers32-34. Hence, movement of the tip27aof first lock pin27out of engagement with the first lock hole24against the spring force of first spring36, movement of the tip28aof second lock pin28out of engagement with the second lock hole25against the spring force of second spring37, and movement of the tip29aof third lock pin29out of engagement with the third lock hole26against the spring force of third spring38simultaneously occur. Thus, free rotation of vane rotor9relative to sprocket1in the normal-rotational direction or in the reverse-rotational direction can be permitted. At the same time, working fluid is supplied to both of the phase-retard chamber11and the phase-advance chamber12.

Hereupon, assume that working-fluid pressure is merely delivered to either one of phase-retard chamber11and phase-advance chamber12. In such a case, a rotary motion of vane rotor9relative to sprocket1in either one of the phase-retard direction and the phase-advance direction occurs, and hence the first lock pin27has to receive a shearing force caused by a circumferential displacement of the first lock-pin hole31aof rotor15relative to the first lock hole24. In a similar manner, the second lock pin28has to receive a shearing force caused by a circumferential displacement of the second lock-pin hole31bof rotor15relative to the second lock hole25. In a similar manner, the third lock pin29has to receive a shearing force caused by a circumferential displacement of the second lock-pin hole31cof rotor15relative to the second lock hole26. As a result of this, the first lock pin27is brought into a so-called jammed (bitten) condition between the first lock-pin hole31aand the first lock hole24displaced relatively. The second lock pin28is also brought into a so-called jammed (bitten) condition between the second lock-pin hole31band the second lock hole25displaced relatively. The third lock pin29is also brought into a so-called jammed (bitten) condition between the third lock-pin hole31cand the third lock hole26displaced relatively. Hence, there is a possibility that the locked (engaged) state of lock pins27-29with respective lock holes24-26cannot be easily released.

Also, assume that there is no hydraulic-pressure supply to both of the phase-retard chamber11and the phase-advance chamber12. In such a case, owing to alternating torque transmitted from the camshaft2, vane rotor9tends to flutter, and thus vane rotor9(especially, the first vane16a) is brought into collision-contact with the shoe10aof housing body10, and whereby there is an increased tendency for hammering noise to occur.

In contrast to the above, according to the valve timing control apparatus of the embodiment, working-fluid pressure (hydraulic pressure) can be simultaneously supplied to both of the phase-retard chamber11and the phase-advance chamber12. Thus, it is possible to adequately suppress vane rotor9from fluttering and also to adequately suppress the jammed (bitten) condition of the first lock pin27between the first lock-pin hole31aand the first lock hole24, the jammed (bitten) condition of the second lock pin28between the second lock-pin hole31band the second lock hole25, and the jammed (bitten) condition of the third lock pin29between the third lock-pin hole31cand the third lock hole26.

Thereafter, when the engine operating condition has been shifted to a low-speed low-load operating range, the valve spool is further displaced against the spring force of the valve spring by energizing the solenoid with a further increase in electric current flowing through the electromagnetic coil of electromagnetic directional control valve41, and thus positioned at the “third position”. Both of the lock passage20and the phase-retard passage18remain kept in a fluid-communication relationship with the discharge passage40a. Fluid-communication between the phase-advance passage19and the drain passage43becomes established.

As a result of this, first, second, and third lock pins27-29become kept out of engagement with respective lock holes24-26. Also, working fluid in phase-advance chamber12is drained through the drain passage43and thus hydraulic pressure in phase-advance chamber12becomes low, whereas working fluid is delivered via the discharge passage40ato the phase-retard chamber11and thus hydraulic pressure in phase-retard chamber11becomes high. Accordingly, vane rotor9rotates relative to the housing7(i.e., sprocket1) toward the maximum phase-retard angular position.

Accordingly, a valve overlap of open periods of intake and exhaust valves becomes small and thus the amount of in-cylinder residual gas also reduces, thereby enhancing a combustion efficiency and consequently ensuring stable engine revolutions and improved fuel economy.

Thereafter, when the engine operating condition has been shifted to a high-speed high-load operating range, the valve spool is displaced by energizing the solenoid of electromagnetic directional control valve41with a small amount of control current flowing through the electromagnetic coil, and thus positioned at the “second position”. As a result, fluid-communication between the phase-retard passage18and the drain passage43becomes established. The lock passage20remains kept in a fluid-communication relationship with the discharge passage40a. At the same time, fluid-communication between the phase-advance passage19and the discharge passage40abecomes established.

Therefore, first, second, and third lock pins27-29are kept out of engagement with respective lock holes24-26. Also, working fluid in phase-retard chamber11is drained through the drain passage43and thus hydraulic pressure in phase-retard chamber11becomes low, whereas working fluid is delivered via the discharge passage40ato the phase-advance chamber12and thus hydraulic pressure in phase-advance chamber12becomes high. Accordingly, vane rotor9rotates relative to the housing7(i.e., sprocket1) toward the maximum phase-advance angular position (seeFIG. 5). Thus, the angular phase of camshaft2relative to sprocket1is converted into the maximum advanced relative-rotation phase.

Accordingly, a valve overlap of open periods of intake and exhaust valves becomes large and thus the intake-air charging efficiency is increased, thereby improving engine torque output.

Conversely when the engine operating condition shifts from the low-speed low-load operating range or the high-speed high-load operating range to the idling condition, a supply of control current from controller35to the electromagnetic coil of electromagnetic directional control valve41is stopped and thus the solenoid is de-energized. Thus, the valve spool is positioned at the “first position” (i.e., the spring-offset position) shown inFIG. 1by the spring force of the valve spring. The lock passage20communicates with the drain passage43, whereas the discharge passage40acommunicates with both of the phase-retard passage18and the phase-advance passage19. Accordingly, hydraulic pressures having almost the same pressure value are applied to respective hydraulic chambers (phase-retard chamber11and phase-advance chamber12).

For the reasons discussed above, even when vane rotor9has been positioned at a phase-retard angular position, rotary motion of vane rotor9relative to sprocket1in the phase-advance direction occurs owing to alternating torque acting on camshaft2. Hence, by the spring force of first spring36and by virtue of the ratchet action of the first lock guide stepped groove (bottom faces24a-24b), first lock pin27is brought into engagement with the first and second bottom faces24a-24bof first lock hole24, one-by-one, owing to rotary motion of vane rotor9in the phase-advance direction. In a similar manner, by the spring force of second spring37and by virtue of the ratchet action of the second lock guide stepped groove (bottom faces25a-25b), second lock pin28is brought into engagement with the first and second bottom faces25a-25bof second lock hole25, one-by-one, owing to rotary motion of vane rotor9in the phase-advance direction. Also, by the spring force of third spring38and by virtue of the ratchet action of the third lock guide groove (bottom face26a), third lock pin29is brought into engagement with the bottom face26aof third lock hole26, owing to rotary motion of vane rotor9in the phase-advance direction. Hence, the angular position of vane rotor9relative to sprocket1is held or locked at the intermediate-phase angular position (seeFIG. 4) between the maximum phase-retard angular position and the maximum phase-advance angular position.

Also, when stopping the engine, the ignition switch is turned OFF. As previously described, first, second, and third lock pins27-29are maintained in their locked states where the tip27aof first lock pin27has been engaged with the second bottom face24bof first lock hole24, the tip28aof second lock pin28has been engaged with the second bottom face25bof second lock hole25, and the tip29aof third lock pin29has been engaged with the bottom face26aof third lock hole26.

Furthermore, assume that the engine is operating continuously in a given engine operating range, the electromagnetic coil of the solenoid of electromagnetic directional control valve41is energized with a given amount of control current, and thus the valve spool is positioned at a substantially intermediate axial position, that is, the “fourth position”. As a result, fluid communication between the phase-advance passage19and the discharge passage40ais blocked and fluid communication between the phase-retard passage18and the drain passage43is blocked. On the other hand, fluid communication between the discharge passage40aand the lock passage20is established.

Hence, hydraulic pressure of working fluid in each of phase-retard chambers11and hydraulic pressure of working fluid in each of phase-advance chambers12are held constant. Also, by the hydraulic-pressure supply from the discharge passage40ato the lock passage20, first, second, and third lock pins27-29are kept out of engagement with respective lock holes24-26, that is, held in their unlocked states.

Therefore, the angular position of vane rotor9relative to sprocket1is held at a desired angular position corresponding to the given amount of control current, and thus the angular phase of camshaft2relative to sprocket1(i.e., housing7) is held at a desired relative-rotation phase. Accordingly, intake valve open timing (IVO) and intake valve closure timing (IVC) can be held at respective desired timing values.

In this manner, by energizing the solenoid of electromagnetic directional control valve41with a desired amount of control current or de-energizing the solenoid, by means of controller35depending on latest up-to-date information about an engine operating condition, and thus controlling axial movement of the valve spool, the axial position of the valve spool can be controlled to either one of the first, second, third, and fourth positions. As discussed above, the angular phase of camshaft2relative to sprocket1(i.e., housing7) can be adjusted or controlled to a desired relative-rotation phase (an optimal relative-rotation phase) by controlling both of the phase-change mechanism3and the lock mechanism4, thus more certainly enhancing the control accuracy of valve timing control.

Moreover, assume that the axially sliding spool of the energized electromagnetic directional control valve41has been stuck due to contamination, dirt or debris (e.g., a very small piece of metal) contained in working fluid used in the hydraulic circuit5and jammed between the edge of each of land portions of the spool and the edge of each of the ports, when the engine has stopped abnormally due to an undesirable engine stall, or when restarting the engine after the engine has stopped normally. Owing to the sticking spool, it is difficult to achieve selective switching among the ports, that is, a change in the path of flow through the electromagnetic directional control valve41. Under such an abnormal condition, that is, under a disabling state of sliding movement of the valve spool, the control valve system of the embodiment operates as follows.

That is, when, due to the sticking valve spool, the valve spool is in the disabling state of sliding movement, as a matter of course, it is impossible to execute angular phase control of vane rotor9. The abnormal condition (i.e., the disabling state of movement of the valve spool) is determined by controller35, based on a result of comparison between the actual angular phase detected by the cam angle sensor and the desired angular phase of camshaft2, in other words, based on a time duration during which a state where a command value (a desired valve timing value) for valve timing control differs from an actually detected valve timing value continues, and its predetermined threshold time duration. When the abnormal condition has been determined by means of controller35, controller35generates a maximum amount of control current to the electromagnetic coil of the solenoid of electromagnetic directional control valve41. As a result of this, the valve spool is forcibly displaced axially against the spring force of the valve spring by a maximum magnitude of electromagnetic force produced by the solenoid, while shearing the contamination or debris, and thus positioned at the “fifth position”. Hence, all of phase-retard passage18, phase-advance passage19, and lock passage20communicate with the drain passage43, and as a result working fluid in each of phase-retard chambers11, working fluid in each of phase-advance chambers12, and working fluid in each of first, second, and third unlocking pressure-receiving chambers32-34are all drained into the oil pan42. As discussed above, electromagnetic directional control valve41has six different envelope configurations. InFIG. 1, the rightmost envelope configuration of electromagnetic directional control valve41corresponds to the “first position”, whereas the leftmost envelope configuration corresponds to the “fifth position”. That is, the rightmost envelope configuration corresponding to the “first position”, the envelope configuration corresponding to the “sixth position”, the envelope configuration corresponding to the “third position”, the envelope configuration corresponding to the “fourth position”, the envelope configuration corresponding to the “second position”, and the leftmost envelope configuration corresponding to the “fifth position” are arranged in that order in the right-to-left direction.

As discussed above, in the valve timing control apparatus of the embodiment, first, second, and third lock pins27-29are installed in the rotor15of vane rotor9via respective lock-pin holes31a-31c. Thus, it is possible to adequately reduce a circumferential thickness of each of vanes16a-16d, thereby adequately enlarging a relative-rotation angle of vane rotor9relative to housing7.

Hitherto, in order to retain or hold lock pins, the rotor diameter of a vane rotor (a vane member) in itself had to be expanded. In contrast, in the apparatus of the embodiment, the rotor15of vane rotor9has partly-expanded, circumferentially-spaced large-diameter portions15e-15fwithout expanding the entire circumference of rotor15, and three lock pins27-29are installed in the partly-expanded large-diameter portions15e-15fof rotor15. By virtue of the different-diameter deformed outer peripheral surface of rotor15, the total volumetric capacity of hydraulic chambers11aand12a, located in the area corresponding to the small-diameter portion (each of first and second small-diameter portions15c-15d) of rotor15, is set to be greater than the total volumetric capacity of hydraulic chambers11band12b, located in the area corresponding to the large-diameter portion (each of first and second large-diameter portions15e-15f).

Thus, the pressure-receiving surface area of each of side faces16e-16hof vanes16a-16d, facing hydraulic chambers11aand12alocated in the area corresponding to the small-diameter portion (each of first and second small-diameter portions15c-15d), is set to be adequately greater than that of each of side faces of vanes16a-16d, facing hydraulic chambers11band12blocated in the area corresponding to the large-diameter portion (each of first and second large-diameter portions15e-15f). Hence, during valve timing control, a relative-rotation speed of vane rotor9to housing7can be increased, thereby adequately enhancing a conversion responsiveness of the relative-rotation phase of camshaft2to housing7(the crankshaft) and satisfactorily improving a responsiveness of intake-valve timing control.

Furthermore, two small-diameter portions15c-15dare arranged at angular positions circumferentially spaced apart from each other and diametrically opposed to each other (concretely, by approximately 180 degrees), whereas two large-diameter portions15e-15fare arranged at angular positions circumferentially spaced apart from each other and diametrically opposed to each other (concretely, by approximately 180 degrees). As a whole, the weight of vane rotor9can be circumferentially balanced and uniformed, thereby avoiding rotational unbalance of vane rotor9. This ensures a smooth rotary motion of vane rotor9relative to housing7.

Additionally, two large-diameter portions15e-15fare arranged at angular positions circumferentially spaced apart from each other by an angular range of approximately 180 degrees greater than 120 degrees. When fixing the rotor onto a machine tool (e.g., a metalworking machine tool), the diametrically-opposed large-diameter portions15e-15fcan be easily secured or grasped in a chuck. Thus, the working efficiency can be improved.

Additionally, in the embodiment, a function of hydraulic-pressure control for each of the hydraulic pressure chambers (phase-retard chamber11and phase-advance chamber12) and a function of hydraulic-pressure control for each of first, second, and third unlocking pressure-receiving chambers32-34are both achieved by means of the single electromagnetic directional control valve41. Thus, it is possible to enhance the flexibility of layout of the VTC system on the engine body, thus ensuring lower system installation time and costs.

Furthermore, it is possible to enhance the ability to hold the angular position of vane rotor9relative to sprocket1at the intermediate-phase angular position by means of the lock mechanism4. Additionally, by virtue of the first lock guide groove (the two-stage stepped lock guide groove with two bottom faces24a-24b, serving as a one-way clutch, in other words, a ratchet) and the second lock guide groove (the two-stage stepped lock guide groove with two bottom faces25a-25b, serving as a one-way clutch, in other words, a ratchet), movement of first lock pin27only into engagement with the first lock hole24and movement of second lock pin28only into engagement with the second lock hole25are permitted, thus assuring more safe and certain guiding action for movement of lock pins27-28into engagement.

Even when vane rotor9tends to rotate relative to sprocket1in the phase-retard direction owing the positive torque, it is possible to safely certainly guide the vane rotor9toward the intermediate-phase angular Position (seeFIG. 4) by virtue of a long five-stage ratchet action, created by two bottom faces24a-24bof first lock hole24, two bottom faces25a-25bof second lock hole25, and bottom face26aof third lock hole26.

Hydraulic pressure in each of phase-retard chamber11and phase-advance chamber12is not used as hydraulic pressure acting on each of first, second, and third unlocking pressure-receiving chambers32-34. In comparison with a system that hydraulic pressure in each of phase-retard chamber11and phase-advance chamber12is also used as hydraulic pressure acting on each of unlocking pressure-receiving chambers, a responsiveness of the hydraulic system of the embodiment to hydraulic pressure supply to each of unlocking pressure-receiving chambers32-34can be greatly improved. Thus, it is possible to improve a responsiveness of each of lock pins27-29to backward movement for unlocking (disengaging). Also, the hydraulic system of the embodiment, in which hydraulic pressure can be supplied to each of unlocking pressure-receiving chambers32-34without using hydraulic pressure in each of phase-retard chamber11and phase-advance chamber12, more concretely, the single electromagnetic directional control valve41eliminates the need for a fluid-tight sealing device between each of phase-retard chamber11and phase-advance chamber12and each of unlocking pressure-receiving chambers32-34.

In addition to the above, in the shown embodiment, lock mechanism4is comprised of three separate lock devices, that is, (i) the first lock pin27and the first lock guide groove (the two-stage stepped groove) with first and second bottom faces24a-24b, (ii) the second lock pin28and the second lock guide groove (the two-stage stepped groove) with first and second bottom faces25a-25b, and (iii) the third lock pin29and the third lock guide groove with bottom face26a. Hence, it is possible to reduce the wall thickness of sprocket1in which each of lock holes24-26is formed. In more detail, for instance assume that the lock mechanism is constructed by a single lock pin and a single lock guide groove (a single multi-stage stepped groove). In such a case, five bottom faces have to be formed in the sprocket in a manner so as to continuously lower stepwise from the phase-retard side to the phase-advance side. As a matter of course, to provide the five-stage stepped groove, the wall thickness of the sprocket also has to be increased. In contrast, the embodiment adopts three separate lock devices (27,24a-24b;28,25a-25b;29,26a) as the lock mechanism, and hence it is possible to reduce the thickness of sprocket1, thereby shortening the axial length of the VTC apparatus and consequently enhancing the flexibility of layout of the VTC system on the engine body.

Second Embodiment

Referring now toFIG. 12, there is shown the cross section of the VTC apparatus of the second embodiment. The VTC apparatus of the second embodiment shown inFIG. 12differs from the first embodiment shown inFIGS. 1-11, in that the structure of lock mechanism4is somewhat modified. Concretely, in the second embodiment, first large-diameter portion15e, first lock-pin hole31a, first lock pin27, and first lock hole24are eliminated. That is, rotor15of the VTC apparatus of the second embodiment has only the second large-diameter portion15f, and thus second and third lock-pin holes31b-31c, second and third lock pins28-29, and second and third lock holes25-26exist. Note that, in the second embodiment, first large-diameter portion15eis replaced by and formed as a third small-diameter portion15g.

In the second embodiment, owing to the eliminated first lock guide stepped groove (the eliminated first lock hole24), the previously-discussed ratchet action, based on the first lock device (first lock pin27and first lock hole24), cannot be created within a phase-angle range of vane rotor9held in the vicinity of the maximum phase-retard position with the ignition switch turned OFF. However, when rotary motion of vane rotor9relative to sprocket1in the phase-advance direction occurs owing to the negative torque of alternating torque acting on camshaft2, and then vane rotor9reaches an angular position as shown inFIG. 9, the second lock pin28slides into engagement with the second lock hole25and then brought into abutted-engagement with the first and second bottom faces25a-25b, in a stepwise manner (see the ratchet action, based on the second lock device (second lock pin28and second lock hole25), at angular positions of vane rotor9as shown inFIGS. 9-10).

Thereafter, when the tip28aof second lock pin28further moves in the phase-advance direction, while being kept in sliding-contact with the second bottom face25b, as shown inFIG. 11, the tip29aof third lock pin29slides into engagement with the third lock hole26. With two lock pins28-29engaged with respective pin holes25-26, the circumferentially-opposed outer peripheral edges of second and third lock pins28-29, circumferentially opposed to each other, abut with the circumferentially-opposed upstanding inner faces25cand26bof second and third lock holes25-26, respectively, such that the specified area of the inner face1cof sprocket1, ranging between the two upstanding inner faces25cand26b, is sandwiched with the two lock pins28-29.

The other construction of the VTC apparatus of the second embodiment ofFIG. 12is the same as that described for the first embodiment. Hence, in the same manner as the first embodiment, in the apparatus of the second embodiment, it is possible to adequately reduce a circumferential thickness of each of vanes16a-16d, thereby adequately enlarging a relative-rotation angle of vane rotor9relative to housing7.

Additionally, in the second embodiment, the total volumetric capacity of hydraulic chambers11aand12a, located in the area corresponding to the small-diameter portion (each of first, second, and third small-diameter portions15c,15d, an15g) of rotor15, is set to be greater than the total volumetric capacity of hydraulic chambers11band12b, located in the area corresponding to the large-diameter portion (only one large-diameter portion15f). Thus, the pressure-receiving surface area of each of side faces16e-16hof vanes16a-16d, facing hydraulic chambers11aand12alocated in the area corresponding to the small-diameter portion (each of first and second small-diameter portions15c-15d), is set to be greater than that of each of side faces of vanes16a-16d, facing hydraulic chambers11band12blocated in the area corresponding to the large-diameter portion (second large-diameter portion15f). Additionally, the pressure-receiving surface area of a side face16iof the fourth vane16d, facing the hydraulic chamber (the phase-advance chamber12a) located in the area corresponding to the additional small-diameter portion (the third small-diameter portion15g), is also set to be greater than that of each of side faces of vanes16a-16d, facing hydraulic chambers11band12blocated in the area corresponding to the large-diameter portion (second large-diameter portion15f). Therefore, as compared to the first embodiment, the apparatus of the second embodiment can attain a more greatly increased relative-rotation speed of vane rotor9to housing7during valve timing control, thereby more adequately enhancing a conversion responsiveness of the relative-rotation phase of camshaft2to housing7(the crankshaft) and more satisfactorily improving a responsiveness of intake-valve timing control.

Third Embodiment

Referring now toFIG. 13, there is shown the cross section of the VTC apparatus of the third embodiment. The VTC apparatus of the third embodiment shown inFIG. 13is similar to the first embodiment shown inFIGS. 1-11, except that, in the third embodiment, first small-diameter portion15cis replaced by and formed as a third large-diameter portion15hhaving almost the same radius of curvature as each of first and second large-diameter portions15e-15f, and a fourth lock device (i.e., a fourth lock pin30and a fourth lock hole23formed in the inner face1cof sprocket1) is added.

The third large-diameter portion15hhas a fourth lock-pin hole31d(an axial through hole) formed therein, such that the fourth lock pin30is slidably disposed in the fourth lock-pin hole31d. The fourth lock pin30is permanently biased in a direction of movement of fourth lock pin30into engagement with the fourth lock hole23by a spring force of a fourth spring44(biasing means).

In a similar manner to the first lock hole24, the fourth lock hole23is arranged on the side of fourth large-diameter portion15hof rotor15and formed into a cocoon shape (or a circular-arc elliptic shape) extending in the circumferential direction of sprocket1. The fourth lock hole23is formed as a two-stage stepped hole whose bottom face lowers stepwise from the phase-retard side to the phase-advance side. The fourth lock hole23(i.e., the two-stage stepped groove) is configured to gradually lower from the first bottom face23ato the second bottom face23b, in that order.

The operation of the fourth lock device (fourth lock pin30and fourth lock hole23) is the same as the first lock device (first lock pin27and first lock hole24). That is, in the presence of rotary motion of vane rotor9relative to sprocket1in the phase-advance direction occurring owing to the negative torque of alternating torque acting on camshaft2immediately after the engine stops, the tip of fourth lock pin30can be brought into engagement with the first and second bottom faces23a-23bof fourth lock hole23, one-by-one, by the spring force of fourth spring44and by virtue of the ratchet action of the fourth lock guide stepped groove (bottom faces23a-23b). Hence, in a similar manner to the first lock device, the fourth lock device (fourth lock pin30and fourth lock hole23) also permits normal rotation of vane rotor9relative to sprocket1in the phase-advance direction, but restricts or prevents reverse-rotation of vane rotor9relative to sprocket1in the phase-retard direction by virtue of the ratchet action. Thus, vane rotor9can be stably surely shifted in the phase-advance direction, while restricting reverse-rotation of vane rotor9.

The other construction of the VTC apparatus of the third embodiment ofFIG. 13is the same as that described for the first embodiment. Basically, the apparatus of the third embodiment can provide the same effects as the first embodiment. In particular, in the third embodiment, the fourth lock device (fourth lock pin30and fourth lock hole23) is added, and hence it is possible to more certainly lock or hold the vane rotor9at the intermediate-phase angular position.

It will be appreciated that the invention is not limited to the particular embodiments shown and described herein, but that various changes and modifications may be made. The valve timing control (VTC) apparatus of the shown embodiment is exemplified in the phase control apparatus applied to an intake-valve side of an internal combustion engine. In lieu thereof, the VTC apparatus may be used for a phase control apparatus installed on an exhaust-valve side.

In the shown embodiment, the number of vanes of vane rotor9is “4”. As can be appreciated from the above, the fundamental concept of the invention may be applied to a valve timing control apparatus equipped with a vane rotor having four or more vanes or four or less vanes.

The entire contents of Japanese Patent Application No. 2011-226561 (filed Oct. 14, 2011) are incorporated herein by reference.

While the foregoing is a description of the preferred embodiments carried out the invention, it will be understood that the invention is not limited to the particular embodiments shown and described herein, but that various changes and modifications may be made without departing from the scope or spirit of this invention as defined by the following claims.