Patent Publication Number: US-10329968-B2

Title: Valve timing control device for internal combustion engine

Description:
TECHNICAL FIELD 
     The present invention relates to a valve timing control device for an internal combustion engine for controlling valve timings (i.e., valve open timing and valve closure timing) of intake and/or exhaust valves depending on engine operating conditions. 
     BACKGROUND ART 
     One such valve timing control device for an internal combustion engine, has been disclosed in the following prior-art Patent document 1. 
     That is to say, the valve timing control device disclosed in the Patent document 1, is configured to lock a relative rotation phase of a vane rotor to a housing (a timing sprocket) in a predetermined relative rotation phase relationship between them by engagement of a lock pin during an engine stopping period, thereby improving a startability. 
     Also provided in the vane rotor is a fluid-communication control mechanism for permitting fluid-communication between a phase-retard side communication passage and a phase-advance side communication passage through an annular groove formed in the outer periphery of a communication pin. For instance, when an engine has stalled with the vane rotor whose relative rotation phase has been kept in a maximum phase-retard state, the fluid-communication control mechanism permits two adjacent hydraulic chambers (that is, a phase-retard side hydraulic chamber and a phase-advance side hydraulic chamber), arranged circumferentially adjacent to each other and defined on both sides of a vane, to be communicated with each other. This increases a fluttering motion of the vane rotor, caused by positive and negative alternating torque transmitted from the camshaft, thereby enabling the vane rotor to be moved to the predetermined relative rotation phase rapidly. 
     CITATION LIST 
     Patent Literature 
     Patent document 1: JP2013-185442 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     By the way, in the previously-discussed prior-art valve timing control device, release (or unlocking) of the lock pin and release of the communication pin are performed by pushing the respective pins away by hydraulic pressures applied to the tips of the pins and acting against the biasing forces of springs biasing these pins respectively. 
     With the previously-discussed configuration, assuming that the locked state of the lock pin is released prior to shutting off fluid-communication between the adjacent hydraulic chambers by means of the fluid-communication control mechanism, it is impossible to apply a satisfactorily controlled hydraulic pressure to the vane rotor, and thus there is a possibility for the control responsiveness of the vane rotor to be degraded after having restarted the engine. 
     It is, therefore, in view of the previously-described drawbacks of the prior art, an object of the invention to provide a valve timing control device for an internal combustion engine capable of ensuring the improved control responsiveness after having restarted the engine. 
     Solution to Problem 
     In order to accomplish the aforementioned and other objects, according to the present invention, a valve timing control device for an internal combustion engine, includes a housing adapted to be driven by torque transmitted from a crankshaft and having a plurality of shoes formed to protrude radially inward from an inner periphery of the housing for partitioning an internal space into a plurality of working chambers, a vane rotor having a rotor configured to rotate relatively to the housing and a plurality of vanes fixedly connected to a camshaft together with the rotor and formed to protrude radially outward from an outer periphery of the rotor for partitioning the working chambers into phase-retard chambers and phase-advance chambers in cooperation with the shoes, a lock mechanism interposed between the vane rotor and the housing for restricting rotation (rotary motion) of the vane rotor relative to the housing depending on an engine operating condition, and a fluid-communication control mechanism having a communication hole formed in at least one of the plurality of vanes so as to permit fluid-communication between the phase-retard chamber and the phase-advance chamber defined by the at least one vane through the communication hole, and configured such that a state of fluid-communication of the communication hole is switchable. The communication hole is switched to a fluid-communication restricted state by the fluid-communication control mechanism at a relatively earlier time than restriction release (unlocking) of the lock mechanism. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to control or switch the communication hole to its fluid-communication restricted state at an earlier time than restriction release (unlocking) of the lock mechanism, thereby enabling application of an appropriately controlled hydraulic pressure during valve timing control after having restarted the engine. As a result, it is possible to ensure the improved control responsiveness. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective disassembled view illustrating an internal combustion engine valve timing control device of the first embodiment according to the invention. 
         FIG. 2  is a longitudinal cross-sectional view illustrating the internal combustion engine valve timing control device shown in  FIG. 1 , simultaneously with essential parts of a hydraulic circuit concerned with the valve timing control device. 
         FIG. 3  is a cross-sectional view taken along the line A-A of  FIG. 2 . 
         FIG. 4  is a cross-sectional view taken along the line B-B of  FIG. 3 . 
         FIG. 5  is a cross-sectional view taken along the line C-C of  FIG. 3 . 
         FIG. 6  illustrates a vane-rotor maximum phase-retard state, and  FIG. 6A  is a lateral cross-sectional view taken along the line A-A of  FIG. 2  under the maximum phase-retard state, whereas  FIG. 6B  is a cross-sectional view taken along the line C-C of  FIG. 3  under the maximum phase-retard state. 
         FIG. 7  illustrates a vane-rotor lock state, and  FIG. 7A  is a lateral cross-sectional view taken along the line A-A of  FIG. 2  under the vane-rotor lock state, whereas  FIG. 7B  is a cross-sectional view taken along the line C-C of  FIG. 3  under the vane-rotor lock state. 
         FIG. 8  illustrates a vane-rotor maximum phase-advance state, and  FIG. 8A  is a lateral cross-sectional view taken along the line A-A of  FIG. 2  under the maximum phase-advance state, whereas  FIG. 8B  is a cross-sectional view taken along the line C-C of  FIG. 3  under the maximum phase-advance state. 
         FIG. 9  illustrates the second embodiment according to the invention, and  FIG. 9A  is a view corresponding to  FIG. 4  that shows the longitudinal cross-section of a lock mechanism, whereas  FIG. 9B  is a view corresponding to  FIG. 5  that shows the longitudinal cross-section of a fluid-communication control mechanism. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Details of the internal combustion engine valve timing control device of each of the embodiments according to the invention are hereinafter described in reference to the drawings. By the way, in the shown embodiments, the valve timing control device is applied to a valve actuating device of the intake-valve side. 
     First Embodiment 
     Referring now to the drawings, particularly to  FIGS. 1-8 , there is shown the internal combustion engine valve timing control device of the first embodiment according to the invention. As shown in  FIG. 1 , the valve timing control device of the first embodiment includes a sprocket  1 , a camshaft  2 , a phase-change mechanism  3 , a pair of lock mechanisms  4 ,  4 , a pair of fluid-communication control mechanisms  5 ,  5 , and a hydraulic-pressure supply-discharge mechanism  6 . Sprocket  1  is rotated and driven by torque transmitted from a crankshaft (not shown). Camshaft  2  is configured to be rotated relatively to the sprocket  1 . Phase-change mechanism  3  is interposed between the sprocket  1  and the camshaft  2  for converting a relative rotation phase between the sprocket  1  and the camshaft  2 . Lock mechanisms  4  are configured to restrict relative rotation between the sprocket  1  and the camshaft  2  by locking the phase-change mechanism  3  at a predetermined intermediate angular position. Fluid-communication control mechanisms  5  are configured to control switching between a communicated state and a shut-off state (a fluid-communication restricted state) of each of a first prescribed adjacent pair (Re 2 , Ad 2 ) of phase-retard chambers Re 1 -Re 4  (described later) and phase-advance chambers Ad 1 -Ad 4  (described later) and a second prescribed adjacent pair (Re 4 , Ad 4 ). Hydraulic-pressure supply-discharge mechanism  6  is configured to selectively operate the phase-change mechanism  3 , the lock mechanisms  4 , and the fluid-communication control mechanisms  5  by switching between pressure-supply and pressure-discharge to and from each of the phase-change mechanism  3 , the lock mechanisms  4 , and the fluid-communication control mechanisms  5 . 
     By the way, the meaning of the previously-noted term “fluid-communication restricted state” includes a slight fluid-communicated state as well as a completely non-communicated state. 
     As shown in  FIGS. 1-3 , phase-change mechanism  3  is comprised of a housing  10 , a vane rotor  20 , and phase-retard working chambers (that is, a first phase-retard chamber Re 1 , a second phase-retard chamber Re 2 , a third phase-retard chamber Re 3 , and a fourth phase-retard chamber Re 4 ) and phase-advance working chambers (that is, a first phase-advance chamber Ad 1 , a second phase-advance chamber Ad 2 , a third phase-advance chamber Ad 3 , and a fourth phase-advance chamber Ad 4 ). In the first embodiment, housing  10  has four shoes (that is, a first shoe  11 , a second shoe  12 , a third shoe  13 , and a fourth shoe  14 ) formed integral with the sprocket  1  and configured to protrude radially inward from the inner periphery of sprocket. Vane rotor  20  is rotatably housed in the inner periphery of housing  10  such that relative rotation of vane rotor  20  to housing  10  is permitted. Also, vane rotor  20  is fixedly connected to one axial end of camshaft  2  such that vane rotor  20  can be rotated integrally with the camshaft  2 . In the shown embodiment, the internal space, defined between the vane rotor  20  and the shoes  11 - 14  of housing  10 , are partitioned into four phase-retard chambers Re 1 -Re 4  and four phase-advance chambers Ad 1 -Ad 4 . The relative rotation phase of vane rotor  20  is controlled by selectively switching between hydraulic-pressure supply to the phase-retard chambers Re 1 -Re 4  and hydraulic-pressure supply (working-fluid supply) to the phase-retard chambers Re 1 -Re 4  by way of the hydraulic-pressure supply-discharge mechanism  6 . 
     Housing  10  is constructed by a substantially cylindrical housing main body  15 , a front plate  16  configured to hermetically close the front opening end of housing main body  15 , and a rear plate  17  configured to hermetically close the rear opening end of housing main body  15 . Front plate  16 , housing main body  15 , and rear plate  17  are axially fastened together with a plurality of bolts  7  and integrally connected to each other by screwing these bolts  7  into the rear plate  17 . 
     Housing main body  15  is formed of a sintered metal material and formed into a substantially cylindrical shape. As previously discussed, the inner periphery of housing main body  15  is formed integral with radially-inward protruding shoes  11 - 14 , whereas the outer periphery of housing main body  15  is formed integral with the sprocket  1 . Each of shoes  11 - 14  has a bolt-insertion hole (a through hole)  15   a  through which bolt  7  is screwed into the rear plate. 
     Front plate  16  is formed of a metal material and formed into a comparatively thin-wall disk shape. The center of front plate  16  is formed as a substantially circular cam-bolt receiving bore  16   a  in which the head of a cam bolt  8  is received. Also, front plate  16  has four bolt insertion holes  16   b  formed around the cam-bolt receiving bore  16   a  and circumferentially spaced from each other. When installing the front plate, four bolts  7  are inserted into respective bolt insertion holes  16   b.    
     Rear plate  17  is formed of a metal material and formed into a substantially disk shape. The center of rear plate  17  is formed as a substantially circular camshaft-end insertion bore  17   a  into which camshaft  2  is inserted. Also, rear plate  17  has four female screw-threaded holes  17   b  formed around the camshaft-end insertion bore  17   a  and circumferentially spaced from each other. When installing the rear plate, four bolts  7  are screwed into respective female screw-threaded holes  17   b.    
     Vane rotor  20  is comprised of a rotor main body  25  and a plurality of vanes (four vanes in the first embodiment). Rotor main body  25  and vanes  21 - 24  are formed of a metal material. Rotor main body  25  is integrally connected to the axial end of camshaft  2  by means of the cam bolt  8 . Rotor main body  25  is formed integral with four vanes (that is, a first vane  21 , a second vane  22 , a third vane  23 , and a fourth vane  24 ) configured to protrude radially outward from the outer periphery of rotor main body  25  and almost equidistant-spaced from each other at approximately equal intervals, such as 90 degrees, in the circumferential direction. The first vane  21  is configured to be substantially conformable to the space defined between the fourth shoe  14  and the first shoe  11 . The second vane  22  is configured to be substantially conformable to the space defined between the first shoe  11  and the second shoe  12 . The third vane  23  is configured to be substantially conformable to the space defined between the second shoe  12  and the third shoe  13 . The fourth vane  24  is configured to be substantially conformable to the space defined between the third shoe  13  and the fourth shoe  14 . 
     By the way, four shoes  11 - 14  have respective seal retaining grooves, formed in their innermost ends (apexes) opposed to the rotor main body  25 . Seal members (apex seals) S 2  are fitted into the respective seal retaining grooves of shoes  11 - 14  so as to bring these seal members S 2  into sliding-contact with the outer peripheral surface of rotor main body  25  (small-diameter portions  26   a  and large-diameter portions  26   b , described later) of vane rotor  20 . In a similar manner to the shoes, four vanes  21 - 24  have respective seal retaining grooves, formed in their outermost ends (apexes) opposed to the housing main body  15 . Seal members (apex seals) S 1  are fitted into the respective seal retaining grooves of vanes  21 - 24  so as to bring these seal members S 1  into sliding-contact with the inner peripheral surface of housing main body  15 . Accordingly, the spaces defined among the vanes  21 - 24  are partitioned, in cooperation with the respective shoes, into four pairs of hydraulic chambers, that is, the first phase-advance chamber Ad 1  and the first phase-retard chamber Re 1 , the second phase-advance chamber Ad 2  and the second phase-retard chamber Re 2 , the third phase-advance chamber Ad 3  and the third phase-retard chamber Re 3 , and the fourth phase-advance chamber Ad 4  and the fourth phase-retard chamber Re 4 . 
     Rotor main body  25  is formed into a deformed cylindrical shape. The center of rotor main body  25  is formed as a cam-bolt insertion hole (an axial through hole)  25   a  into which the shank of cam bolt  8  is inserted. The front end of cam-bolt insertion hole  25   a  is formed as an axially-protruding cam-bolt seat section  25   b  on which the head of cam bolt  8  is seated. 
     Regarding the rotor main body, the circumference of rotor main body  25  defined between the fourth vane  24  and the first vane  21  and the circumference of rotor main body  25  defined between the second vane  22  and the third vane  23  are formed as a pair of diametrically-opposed, comparatively thin-walled small-diameter portions  26   a ,  26   a . In contrast, the circumference of rotor main body  25  defined between the first vane  21  and the second vane  22  and the circumference of rotor main body  25  defined between the third vane  23  and the fourth vane  24  are formed as a pair of diametrically-opposed, comparatively thick-walled large-diameter portions  26   b ,  26   b.    
     With the previously-discussed configuration of the deformed rotor main body, regarding the vanes  21 - 24 , the pressure-receiving surface area of each of the side face  24   a  of the fourth vane  24  and the side face  21   a  of the first vane  21 , both facing the small-diameter portion  26   a  defined between the fourth vane  24  and the first vane  21 , and the pressure-receiving surface area of each of the side face  22   a  of the second vane  22  and the side face  23   a  of the third vane  23 , both facing the small-diameter portion  26   a  defined between the second vane  22  and the third vane  23 , are dimensioned to be greater than the pressure-receiving surface area of each of the side face  21   b  of the first vane  21  and the side face  22   b  of the second vane  22 , both facing the large-diameter portion  26   b  defined between the first vane  21  and the second vane  22 , and the pressure-receiving surface area of each of the side face  23   b  of the third vane  23  and the side face  24   b  of the fourth vane  24 , both facing the large-diameter portion  26   b  defined between the third vane  23  and the fourth vane  24 . In other words, the first vane  21  (not equipped with the fluid-communication control mechanism  5 ) and the third vane  23  (not equipped with the fluid-communication control mechanism  5 ) are configured such that the summed value of the pressure-receiving surface area of the side face  21   a  of the first vane  21 , facing the first phase-advance chamber Ad 1 , and the pressure-receiving surface area of the side face  23   a  of the third vane  23 , facing the third phase-advance chamber Ad 3 , is set greater than the summed value of the pressure-receiving surface area of the side face  21   b  of the first vane  21 , facing the first phase-retard chamber Re 1 , and the pressure-receiving surface area of the side face  23   b  of the third vane  23 , facing the third phase-retard chamber Re 3 . In contrast, the second vane  22  (equipped with the fluid-communication control mechanism  5 ) and the fourth vane  24  (equipped with the fluid-communication control mechanism  5 ) are configured such that the summed value of the pressure-receiving surface area of the side face  22   b  of the second vane  22 , facing the second phase-advance chamber Ad 2 , and the pressure-receiving surface area of the side face  24   b  of the fourth vane  24 , facing the fourth phase-advance chamber Ad 4 , is set less than the summed value of the pressure-receiving surface area of the side face  22   a  of the second vane  22 , facing the second phase-retard chamber Re 2 , and the pressure-receiving surface area of the side face  24   a  of the fourth vane  24 , facing the fourth phase-retard chamber Re 4 . 
     Also, regarding the deformed configuration of the rotor main body, the side face  24   a  of the fourth vane and the side face  21   a  of the first vane, both facing the small-diameter portion  26   a  defined between the fourth vane and the first vane, are arranged to be circumferentially opposed to each other. The side face  22   a  of the second vane and the side face  23   a  of the third vane, both facing the small-diameter portion  26   a  defined between the second vane and the third vane, are arranged to be circumferentially opposed to each other. Additionally, the side face  21   b  of the first vane and the side face  22   b  of the second vane, both facing the large-diameter portion  26   b  defined between the first vane and the second vane, are arranged to be circumferentially opposed to each other. The side face  23   b  of the third vane and the side face  24   b  of the fourth vane, both facing the large-diameter portion  26   b  defined between the third vane and the fourth vane, are arranged to be circumferentially opposed to each other. Hence, the previously-discussed pressure-receiving surface area differences are canceled. That is, hydraulic pressures (working fluid pressures) acting the vane rotor  20  are totally balanced to each other without undesirably biased hydraulic pressure force. 
     A plurality of phase-retard side communication holes (radial through holes)  25   c  are formed in the rotor main body  25 . A phase-retard side oil passage  51  (described later), which is formed in the camshaft  2 , is communicated with phase-retard chambers Re 1 -Re 4  through respective phase-retard side communication holes  25   c . Thus, working fluid (working oil), which is introduced from the hydraulic-pressure supply-discharge mechanism  6  into the phase-retard side oil passage in the camshaft  2 , is delivered into phase-retard chambers Re 1 -Re 4  by way of respective phase-retard side communication holes  25   c.    
     In addition to the above, a plurality of phase-advance side communication holes (through holes)  25   d  are formed in the rotor main body  25 . A phase-advance side oil passage  52  (described later), which is formed in the camshaft  2 , is communicated with phase-advance chambers Ad 1 -Ad 4  through respective phase-advance side communication holes  25   d . Thus, working fluid (working oil), which is introduced from the hydraulic-pressure supply-discharge mechanism  6  into the phase-advance side oil passage in the camshaft  2 , is delivered into phase-advance chambers Ad 1 -Ad 4  by way of respective phase-advance side communication holes  25   d.    
     As shown in  FIGS. 1-4 , each of lock mechanisms  4  is arranged or installed substantially in a middle of the associated large-diameter portion  26   b  and provided to hold a relative rotation phase of vane rotor  20  to housing  10  at a predetermined intermediate angular phase between a maximum phase-retard position and a maximum phase-advance position. That is, each of lock mechanisms  4  is mainly constructed by a pin housing hole (serving as a lock housing hole)  31 , a lock pin  32  serving as a substantially cylindrical lock member, and a coil spring  33 . Pin housing hole  31  is formed in the large-diameter portion  26   b  as an axial through hole. Lock pin  32  is slidably accommodated in the pin housing hole  31  for restricting rotary motion of vane rotor  20  relative to housing  10  by engagement with an engagement hole  18  recessed or bored in the rear plate  17 . Coil spring  33  is interposed between the lock pin  32  and the front plate  16  for permanently biasing the lock pin  32  toward the rear plate  17 . 
     As shown in  FIG. 4 , lock pin  32  is formed as a stepped cylindrical shape whose diameter decreases toward its front end and which is constructed by a large-diameter portion  32   a , a small-diameter portion  32   b , and a stepped or shouldered portion  32   c  between the large-diameter portion  32   a  and the small-diameter portion  32   b . Under preload, coil spring  33  is elastically installed in a cylindrical-hollow spring housing portion  32   d , bored in the rear end of large-diameter portion  32   a . By virtue of the stepped portion  32   c  of lock pin  32 , a pressure-receiving chamber  35  is defined between the outer peripheral surface of small-diameter portion  32   b  and the inner peripheral surface of pin housing hole  31 . The aforementioned pressure-receiving chambers  35 ,  35 , defined around the small-diameter portions  32   b ,  32   b , are configured to be communicated with a lock mechanism passage  53  through respective communication grooves  36 ,  36  cut in the rear end faces of large-diameter portions  26   b ,  26   b , facing the rear plate  17 . Each of lock mechanisms  4  is configured such that lock pin  32  retreats and moves out of engagement with the engagement hole  18  against the spring force of coil spring  33  by applying hydraulic pressure (serving as an unlock pressure) introduced from the lock mechanism passage  53  to the stepped portion  32   c.    
     As shown in  FIGS. 1-3 and 5 , fluid-communication control mechanisms  5  are provided at the second vane  22  and the fourth vane  24 , respectively, in a manner so as to penetrate each of the second vane and the fourth vane in their width directions. In the shown embodiment, the first fluid-communication control mechanism  5 , provided at the second vane  22 , is mainly constructed by a communication hole  40  which is formed in the second vane  22  such that the two adjacent chambers (that is, the second phase-retard chamber Re 2  and the second phase-advance chamber Ad 2 ) are communicated with each other through the communication hole  40 , a pin housing hole  41 , a communication pin  42 , and a coil spring  43 . Pin housing hole  41  is formed in the second vane  22  as an axial through hole penetrating a substantially midpoint of communication hole  40 . Communication pin  42  serves as a valve element slidably accommodated in the pin housing hole  41  of the second vane. Coil spring  43  (serving as a pin biasing member) is interposed between the communication pin  42  of the second vane and the front plate  16  for permanently biasing the communication pin  42  toward the rear plate  17 . In a similar manner, the second fluid-communication control mechanism  5 , provided at the fourth vane  24 , is mainly constructed by a communication hole  40  which is formed in the fourth vane  24  such that the two adjacent chambers (that is, the fourth phase-retard chamber Re 4  and the fourth phase-advance chamber Ad 4 ) are communicated with each other through the communication hole  40 , a pin housing hole  41 , a communication pin  42 , and a coil spring  43 . Pin housing hole  41  is formed in the fourth vane  24  as an axial through hole penetrating a substantially midpoint of communication hole  40 . Communication pin  42  serves as a valve element slidably accommodated in the pin housing hole  41  of the fourth vane. Coil spring  43  (serving as a pin biasing member) is interposed between the communication pin  42  of the fourth vane and the front plate  16  for permanently biasing the communication pin  42  toward the rear plate  17 . 
     As shown in  FIG. 3 , the communication hole  40  of the second vane  22  is configured such that the side face of the root of the second vane  22 , facing the small-diameter portion  26   a , and the side face of the root of the second vane  22 , facing the large-diameter portion  26   b , are communicated with each other through the communication hole  40 . In a similar manner, the communication hole  40  of the fourth vane  24  is configured such that the side face of the root of the fourth vane  24 , facing the small-diameter portion  26   a , and the side face of the root of the fourth vane  24 , facing the large-diameter portion  26   b , are communicated with each other through the communication hole  40 . That is, communication hole  40  is configured to be inclined with respect to the width direction (the circumferential direction) of each of the second vane  22  and the fourth vane  24 . Hence, as compared to one opening end of communication hole  40 , facing the large-diameter portion  26   b , the other opening end of communication hole  40 , facing the small-diameter portion  26   a , is formed radially inward. 
     As shown in  FIG. 5 , communication pin  42  is formed as a stepped cylindrical shape whose diameter decreases toward its front end and which is constructed by a large-diameter portion  42   a , a small-diameter portion  42   b , and a stepped or shouldered portion  42   c  between the large-diameter portion  42   a  and the small-diameter portion  42   b . Under preload, coil spring  43  is elastically installed in a cylindrical-hollow spring housing portion  42   d , bored in the rear end of large-diameter portion  42   a . An annular groove  44  is formed or cut around the entire circumference of an axial intermediate section of large-diameter portion  42   a . The groove width of annular groove  44  is dimensioned to be identical to the inside diameter of communication hole  40 . Under a specific condition in which communication pin  42  has moved to its maximum advanced axial position, the annular groove  44  is brought into proper alignment with the communication groove  40  (see  FIGS. 6B and 7B ). In concert with an increase in retreating-movement of communication pin  42  retreated from the maximum advanced axial position, the opening area of the annular groove opened into the communication hole, in other words, the flow-path cross-sectional area of the communication hole tends to narrow or reduce. Immediately when communication pin  42  has retreated to an axial position greater than a given position, fluid-communication between the communication hole  40  and the annular groove is shut off (blocked) by the outer periphery of large-diameter portion  42   a  of communication pin  42  (see  FIG. 8B ). As set out above, depending on the flow-path cross-sectional area of communication hole  40  (corresponding to the opening area of the annular groove  44  opened into the communication hole  40 ), determined depending on the axial position of annular groove, switching between a communicated state and a shut-off state (a fluid-communication restricted state) of the second phase-retard chamber Re 2  and the second phase-advance chamber Ad 2  and switching between a communicated state and a shut-off state (a fluid-communication restricted state) of the fourth phase-retard chamber Re 4  and the fourth phase-advance chamber Ad 4  can be controlled. 
     By virtue of the stepped portion  42   c  of communication pin  42 , a pressure-receiving chamber  45  is defined between the outer periphery of small-diameter portion  42   b  and the inner periphery of pin housing hole  41 . The aforementioned pressure-receiving chambers  45 , defined around these small-diameter portions, are configured to be communicated with a fluid-communication mechanism passage  54  through respective communication grooves  46  cut in the rear end faces of large-diameter portions  26   b , facing the rear plate  17 . Each of fluid-communication control mechanisms  5  is configured such that communication pin  42  retreats against the spring force of coil spring  43  by applying hydraulic pressure, serving as an unlock pressure (i.e., lock-to-unlock switching pressure), introduced from the fluid-communication mechanism passage  54  to the stepped portion  42   c  of communication pin  42 . 
     By the way, communication pin  42  is configured or structured to retreat at an earlier time than retreating-movement of lock pin  32 . Concretely, in the shown embodiment, the spring constant (spring stiffness) of coil spring  33  and the spring constant (spring stiffness) of coil spring  43  are set to be identical to each other. Also, the set spring load (in other words, a depth of spring housing portion  32   d  of lock pin  32 ) of coil spring  33  and the set spring load (in other words, a depth of spring housing portion  42   d  of communication pin  42 ) of coil spring  43  are set to be identical to each other. In contrast, the pressure-receiving surface area “St” (see  FIG. 5 ) of the stepped portion  42   c  of communication pin  42  is set or dimensioned to be greater than the pressure-receiving surface area “Sr” (see  FIG. 4 ) of the stepped portion  32   c  of lock pin  32 . 
     Returning to  FIG. 2 , hydraulic-pressure supply-discharge mechanism  6  is mainly constructed by an oil pump  50  serving as a hydraulic pressure source, the phase-retard side oil passage  51 , the phase-advance side oil passage  52 , the lock mechanism passage  53 , the fluid-communication mechanism passage  54 , a supply passage  56 , and a drain passage  57 . Hydraulic-pressure supply-discharge mechanism  6  is provided for selectively switching between working-fluid supply and working-fluid discharge to and from the phase-retard chambers Re 1 -Re 4  and working-fluid supply and working-fluid discharge to and from the phase-advance chambers Ad 1 -Ad 4 . Phase-retard side oil passage  51  is provided for pressure-supply and pressure-discharge to and from phase-retard chambers Re 1 -Re 4  through respective phase-retard side communication holes  25   c . Phase-advance side oil passage  52  is provided for pressure-supply and pressure-discharge to and from phase-advance chambers Ad 1 -Ad 4  through respective phase-advance side communication holes  25   d . Lock mechanism passage  53  is provided for pressure-supply and pressure-discharge to and from pin housing holes  31  through respective communication grooves  36 . Fluid-communication mechanism passage  54  is provided for pressure-supply and pressure-discharge to and from pin housing holes  41  through respective communication grooves  46 . Supply passage  56  is provided for selectively supplying hydraulic pressure from oil pump  50  to each of oil passages  51 - 52  and mechanism passages  53 - 54  via a generally-known electromagnetic directional control valve  55 . Drain passage  57  is provided for draining working fluid (hydraulic pressure) from any one of the phase-retard side oil passage  51 , the phase-advance side oil passage  52 , and the lock mechanism passage  53  (in other words, the fluid-communication mechanism passage  54  branched from the lock mechanism passage) not connected to oil pump  50  via the electromagnetic directional control valve  55 . By the way, the previously-discussed electromagnetic directional control valve  55  is configured to control switching between fluid-communication between oil pump  50  (supply passage  56 ) and each of oil passages  51 - 52  and mechanism passages  53 - 54  and fluid-communication between drain passage  57  and each of oil passages  51 - 52  and mechanism passages  53 - 54 , responsively to a control current from an electronic control unit ECU (not shown). 
     The operation and effects of the valve timing control device of the shown embodiment are hereunder described in detail in reference to  FIGS. 6A-6B, 7A-7B, and 8A-8B .  FIGS. 6A-6B  explain a communicated state of each of fluid-communication control mechanisms  5  employed in the second vane  22  and the fourth vane  24  under the maximum phase-retard state of vane rotor  20 .  FIGS. 7A-7B  explain a communicated state of each of fluid-communication control mechanisms  5  employed in the second vane  22  and the fourth vane  24  under the lock state of vane rotor  20  locked at the predetermined intermediate angular position.  FIGS. 8A-8B  explain a non-communicated state of each of fluid-communication control mechanisms  5  employed in the second vane  22  and the fourth vane  24  under the maximum phase-advance state of vane rotor  20 . 
     For instance, suppose that, during engine running, the engine has stalled unintendedly and thus the engine has stopped running without turning the ignition switch OFF, and thus the relative angular phase of vane rotor  20  has stopped or retained undesirably at a phase angle deviated from the predetermined intermediate angular position (as shown in  FIG. 7A ), corresponding to the lock position of vane rotor  20 . In such a situation, with the oil pump  50  stopped operating, there is no supply of working fluid into each of pin housing holes  41 ,  41  of fluid-communication control mechanisms  5 , and hence each of communication pins  42 ,  42  becomes held at its maximum advanced state. Thus, the annular groove  44  becomes brought into proper alignment (fluid-communication) with the communication groove  40  (see  FIG. 6B ). Accordingly, fluid-communication between the second phase-retard chamber Re 2  and the second phase-advance chamber Ad 2  partitioned by the second vane  22  and circumferentially adjacent to each other and fluid-communication between the fourth phase-retard chamber Re 4  and the fourth phase-advance chamber Ad 4  partitioned by the fourth vane  24  and circumferentially adjacent to each other become established. As a result of this, regarding the vane rotor  20 , working fluid pressures act only on both the first vane  21  and the third vane  23 . 
     Regarding the first vane  21  and the third vane  23 , on which working fluid pressures act, the pressure-receiving surface area of the side face  21   a  of the first vane  21 , facing the phase-advance chamber Ad 1 , and the pressure-receiving surface area of the side face  23   a  of the third vane  23 , facing the phase-advance chamber Ad 3 , are dimensioned to be relatively greater than the pressure-receiving surface area of the side face  21   b  of the first vane  21 , facing the phase-retard chamber Re 1 , and the pressure-receiving surface area of the side face  23   b  of the third vane  23 , facing the phase-retard chamber Re 3 . By working fluid pressure acting on each of the side faces, both facing the phase-advance chamber side and having the relatively greater pressure-receiving surface area, the vane rotor  20  tends to rotate toward the phase-advance side. Thereafter, immediately when the predetermined intermediate angular position has been reached, lock pins  32  are brought into engagement with respective engagement holes  18 , and hence relative rotation of vane rotor  20  is restricted. 
     Subsequently to the above, when restarting the engine, the ignition switch is turned ON and thus oil pump  50  is driven. Therefore, working fluid (hydraulic pressure) is supplied to all the phase-retard chambers Re 1 -Re 4 , the phase-advance chambers Ad 1 -Ad 4 , the pressure-receiving chambers  35 ,  35  (exactly, the stepped portions  32   c ,  32   c  of lock pins  32 ,  32 ) of lock mechanisms  4 , and the pressure-receiving chambers  45 ,  45  (exactly, the stepped portions  42   c ,  42   c  of communication pins  42 ,  42 ) of fluid-communication control mechanisms  5 . After this, immediately when the engine speed exceeds a given engine revolution speed and hence a given engine operating condition has been reached, by virtue of the difference between the pressure-receiving surface area “Sr” (see  FIG. 4 ) of the stepped portion  32   c  of lock pin  32  and the pressure-receiving surface area “St” (see  FIG. 5 ) of the stepped portion  42   c  of communication pin  42 , first, communication pin  42  begins to retreat. Immediately after the given axial position of the retreating communication pin  42  has been reached, fluid-communication between the communication hole  40  and the annular groove  44  becomes blocked by the outer periphery of large-diameter portion  42   a  of communication pin  42  (see  FIG. 8B ). 
     Thereafter, lock pin  32  begins to retreat with a proper time lag from the time when a transition to a non-communicated state (a blocked state) of communication hole  40  by the communication pin  42  has occurred. In concert with an increase in retreating-movement of the lock pin, lock pin  32  moves out of engagement with the engagement hole  18 . The restriction on rotary motion of vane rotor  20  relative to housing  10  becomes released. That is, fluid-communication between the communication hole  40  and the annular groove has already been blocked prior to the lock-pin release. Hence, vane rotor  20  can be controlled to a given relative angular phase determined based on the engine operating condition with hydraulic pressures (working fluid pressures) supplied to either phase-retard chambers Re 1 -Re 4  or phase-advance chambers Ad 1 -Ad 4 . 
     As set out above, the valve timing control device of the embodiment is configured such that, immediately after the engine has been restarted, a transition to a blocked state (a shut-off state) of communication hole  40  by the fluid-communication control mechanisms  5  occurs prior to the release of restriction on rotary motion of vane rotor  20  relative to housing  10 , restricted by means of the lock mechanisms  4 . Therefore, it is possible to ensure or permit a more rapid rotary motion of vane rotor  20  towards the predetermined intermediate angular position by virtue of the pressure-receiving surface area difference of side faces of the first vane  21  and the pressure-receiving surface area difference of side faces of the third vane  23 , in other words, due to the unbalanced pressure-receiving surface area configuration of the first vane and the third vane, when restarting the engine. Additionally, after the engine has been restarted, with communication holes  40 ,  40  blocked in advance and lock pins  32  disengaged (released) with a proper time lag from a transition to a blocked state of each of communication holes  40 ,  40 , it is possible to apply an appropriately controlled hydraulic pressure to not merely some specified vanes (i.e., the first vane  21  and the third vane  23 ), but also to all of the vanes  21 - 24  with hydraulic pressures (working fluid pressures) supplied to either phase-retard chambers Re 1 -Re 4  or phase-advance chambers Ad 1 -Ad 4 , thus ensuring a good control responsiveness of vane rotor  20 . 
     Second Embodiment 
     Referring now to  FIG. 9 , there is shown the internal combustion engine valve timing control device of the second embodiment according to the invention. The second embodiment differs from the first embodiment, in that the fluid-communication control mechanism of the second embodiment is somewhat modified from the configuration of fluid-communication control mechanism  5  of the first embodiment. By the way, the other configuration of the valve timing control device of the second embodiment is similar to that of the first embodiment. In explaining the second embodiment, for the purpose of simplification of the disclosure, the same reference signs used to designate elements in the first embodiment will be applied to the corresponding elements used in the second embodiment, while detailed description of the same reference signs will be omitted because the above description seems to be self-explanatory. 
     That is, in the second embodiment, the axial dimension “Lt” of the spring housing portion  42   d  of fluid-communication control mechanism  5  is set or dimensioned to be greater than the axial dimension “Lr” of the spring housing portion  32   d  of lock mechanism  4 . Hence, the set spring load of coil spring  43  of fluid-communication control mechanism  5  is set to be less than the set spring load of coil spring  33  of lock mechanism  4 . This enables communication pin  42  to retreat at an earlier time than retreating-movement of lock pin  32 . 
     Accordingly, with the previously-discussed configuration of the second embodiment, it is possible to shut off the communication hole  40  by the fluid-communication control mechanisms  5  prior to unlocking (releasing) lock mechanism  4 . Therefore, the device of the second embodiment can provide the same operation and effects as the first embodiment. 
     As discussed above, the device of the second embodiment is configured such that the set spring load of coil spring  43  of fluid-communication control mechanism  5  is set to be less than that of coil spring  33  of lock mechanism  4 . In lieu thereof, the spring constant (spring stiffness) itself of coil spring  43  of fluid-communication control mechanism  5  may be set to be less than the spring constant (spring stiffness) of coil spring  33  of lock mechanism  4 , for the purpose of enabling communication pin  42  to retreat at an earlier time than retreating-movement of lock pin  32 . 
     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. For instance, regarding both the lock mechanism  4  and the hydraulic-pressure supply-discharge mechanism  6 , not directly concerned with essential features of the invention, concrete configurations of these two mechanisms  4  and  6  may be properly changed or altered freely depending on the type, specification and/or manufacturing costs of an internal combustion engine to which the valve timing control device of the invention can be applied. 
     In particular, regarding the lock mechanism  4 , in addition to the lock mechanism as disclosed by reference to each of the first and second embodiments, in which the lock pin  32 , which is inserted into the pin housing hole  31  formed in the rotor main body  25  as a through hole, is brought into engagement with the engagement hole  18  recessed in the inside surface of rear plate  17 . In lieu thereof, another type of lock mechanism, as disclosed in Japanese patent provisional publication No. 2004-116410, for example, in which a platy lock member, which is slidably accommodated in a housing groove cut in a housing, is brought into engagement with an engagement groove cut or formed in the rotor outer periphery of a vane rotor. 
     Also, regarding the fluid-communication control mechanism  5 , it will be appreciated that the invention is not limited to the particular embodiments shown and described herein, that is, the exemplified configurations such as the difference between the pressure-receiving surface area of lock pin  32  and the pressure-receiving surface area of communication pin  42  and the difference between the set spring load of coil spring  33  and the set spring load of coil spring  43 . In other words, the device may be structured or configured such that the hydraulic pressure required for shutting off (blocking) the communication hole  40  is relatively less than the hydraulic pressure required for restriction release (unlocking) of the lock mechanism  4 . Concrete configurations may be properly changed or altered freely depending on the specification of the device and the like. 
     Furthermore, regarding the fluid-communication control mechanism (FCCM)  5 , in the first embodiment a plurality of fluid-communication control mechanisms  5 ,  5  are exemplified, but a plurality of fluid-communication control mechanisms are not always provided. That is, under a specified condition where at least one FCCM-equipped vane and at least one non-FCCM equipped vane, which is the same number as the at least one FCCM-equipped vane and has an unbalanced pressure-receiving surface area configuration, are provided, the same operation and effects as the first embodiment can be provided. 
     The other technical ideas grasped from the embodiments shown and described are enumerated and explained, as follows: 
     (a) The valve timing control device for the internal combustion engine as recited previously, is characterized in that 
     the lock member and the communication pin are accommodated and arranged in a large-diameter portion formed between a prescribed pair of vanes of the plurality of vanes. 
     (b) The valve timing control device for the internal combustion engine as recited in the item (a), is characterized in that 
     the lock member and the communication pin are accommodated in the large-diameter portion and arranged adjacent to each other.