Patent Publication Number: US-8109245-B2

Title: Variable valve apparatus

Description:
TECHNICAL FIELD 
     The present invention relates generally to variable valve apparatus well adapted for use in internal combustion engines and the like. More particularly, the present invention relates to a variable valve apparatus that allows a lift amount of a valve body to be variably set. 
     BACKGROUND ART 
     A known variable valve apparatus, as that disclosed, for example, in Patent Document 1 (JP-A-2004-100555), is capable of variably setting a lift amount of a valve body. The variable valve apparatus of the known art includes a linkage mechanism having a plurality of link parts connected with each other. The linkage mechanism includes an input arm and a rocking arm. Specifically, the input arm receives an input from a drive cam. The rocking arm rocks a rocker arm on a side of the valve body. The input arm is held at all times in a position in contact with the drive cam by an urging force of a spring. The rocking arm is fixed to a rotatable control shaft, so that the rocking arm changes a position thereof (an inclined angle) in accordance with a rotating angle of the control shaft. 
     The linkage mechanism having arrangements as described above translates the input from the drive cam to a corresponding rocking motion of the rocking arm and further transmits the rocking motion to the rocker arm, so that the valve body is opened or closed. At this time, the linkage mechanism varies the inclined angle of the rocking arm according to the rotating angle of the control shaft and the inclined angle is reflected in amplitude of the rocker arm. As a result, the variable valve apparatus can continuously vary the lift amount of the valve body according to the rotating angle of the control shaft. 
     Including the above-mentioned document, the applicant is aware of the following document as a related art of the present invention. 
     [Patent Document 1] JP-A-2004-100555 
     DISCLOSURE OF INVENTION 
     There is a need, during operation of an internal combustion engine, for temporarily stopping an open/close operation of the valve body by setting the lift amount of the valve body to zero. In this case, in accordance with the variable valve apparatus of the known art, the valve body can be made to pause in a closed position by rotating the control shaft to a position, at which the lift amount is zero. 
     In the known variable valve apparatus, however, a process of a gradual decrease in the lift amount in accordance with the rotating angle of the control shaft occurs during a period of time that begins when rotation of the control shaft is started for making the valve body pause and ends when the actual lift amount becomes zero. Specifically, there is in the known art a problem in that the valve body cannot be brought to a stop quickly from any given lift amount. Similarly, it is difficult with the known art to return the valve body in a pause state quickly to any given lift amount. 
     The present invention has been made to solve the foregoing problems of the known art and it is an object of the present invention to provide a variable valve apparatus capable of bringing a valve body to a pause state, and canceling the pause state, quickly at any given lift amount, while continuously varying the lift amount of the valve body. 
     The above object is achieved by a variable valve apparatus which comprise a control shaft rotated for controlling a lift amount of a valve body. The variable valve apparatus comprise a variable mechanism disposed displaceably near a drive cam, the variable mechanism following a profile of the drive cam at a position corresponding to a rotating angle of the control shaft to make a reciprocating motion. 
     The variable valve apparatus comprise a split-type rocking mechanism including an input member receiving the reciprocating motion of the variable mechanism to make a rocking motion and an output member outputting the rocking motion of the input member, the input member and the output member being mutually connectable or disconnectable. 
     The variable valve apparatus comprise a connection selection mechanism selecting a connected or disconnected state between the input member and the output member of the split-type rocking mechanism. And the variable valve apparatus comprise a valve actuating mechanism translating the rocking motion outputted from the output member of the split-type rocking mechanism to a corresponding open or close operation of the valve body. 
     In a second aspect of the present invention, the input member and the output member of the split-type rocking mechanism according to the first aspect of the present invention may be rockably mounted on an outer peripheral side of the control shaft. 
     In a third aspect of the present invention, the split-type rocking mechanism may be formed symmetrically on both sides about a plane perpendicular to the control shaft. 
     In a fourth aspect of the present invention, the input member may include an input side abutment portion, against which the variable mechanism abuts. And the input member may also include two outer support portions rockably supported by the control shaft on both sides of the input side abutment portion. On the other hand, the output member may include an output side abutment portion abutting against the valve actuating mechanism at a position overlapping the input side abutment portion. And the output member may also include an inner support portion rockably supported by the control shaft between the outer support portions of the input member. 
     In a fifth aspect of the present invention, the valve body, the split-type rocking mechanism, the connection selection mechanism, and the valve actuating mechanism may be each disposed on a first side and a second side of the control shaft in an axial direction of the control shaft. And, the variable mechanism may include an arm portion disposed on the outer peripheral side of the control shaft between the split-type rocking mechanism on the first side and the split-type rocking mechanism on the second side, a cam roller disposed at a leading end side of the arm portion, the drive cam abutting against the cam roller, and two intermediate rollers disposed at the leading end side of the arm portion on both sides of the cam roller, each of the two intermediate rollers abutting against the split-type rocking mechanism on the first side and the split-type rocking mechanism on the second side, respectively. 
     In a sixth aspect of the present invention, the valve body, the split-type rocking mechanism, the connection selection mechanism, and the valve actuating mechanism may be disposed on a first side of the control shaft in an axial direction of the control shaft. 
     The valve body and the valve actuating mechanism, together with a non-split-type rocking mechanism may be disposed on a second side of the control shaft in the axial direction of the control shaft. 
     The variable mechanism may include an arm portion disposed on the outer peripheral side of the control shaft between the split-type rocking mechanism on the first side and the non-split-type rocking mechanism on the second side, a cam roller disposed at a leading end side of the arm portion, the drive cam abutting against the cam roller, and two intermediate rollers disposed at the leading end side of the arm portion on both sides of the cam roller, each of the two intermediate rollers abutting against the split-type rocking mechanism on the first side and the non-split-type rocking mechanism on the second side, respectively. 
     In a seventh aspect of the present invention, the connection selection mechanism normally retains a connected state between the input member and the output member and cancels the connected state when driven externally. 
     In an eighth aspect of the present invention, the valve body may be mounted in an internal combustion engine. The connection selection mechanism may be driven by a hydraulic pressure generated when the internal combustion engine operates. 
     In a ninth aspect of the present invention, the connection selection mechanism may include an engagement hole disposed in either one of the input member and the output member. The connection selection mechanism may also include a movable pin displaceably disposed in the other one of the input member and the output member, the movable pin being engaged with or disengaged from the engagement hole. At this time, the retention means normally retaining the movable pin in a state of being engaged with the engagement hole. Also, the disengagement means disengaging the movable pin from the engagement hole against the retention means when a hydraulic pressure is supplied. 
     In a tenth aspect of the present invention, the engagement hole and the movable pin are disposed at positions, at which each opposes each other, when the input member and the output member make a rocking motion relative to each other, within a range of the rocking motion. 
     In an eleventh aspect of the present invention, the connection selection mechanism may be a hydraulically-operated mechanism disposed between the input member and the output member. The control shaft includes a first oil path, to which a hydraulic pressure is supplied from a hydraulic pressure source may also be provided. The split-type rocking mechanism may include a second oil path connected with the first oil path, the second oil path supplying the connection selection mechanism with the hydraulic pressure. 
     In a twelfth aspect of the present invention, the split-type rocking mechanism may include an input side urge means urging the input member toward the variable mechanism and an output side urge means urging the output member toward the valve actuating mechanism. 
     In accordance with the first aspect of the present invention, when the input member and the output member of the split-type rocking mechanism are in a connected state, the input of the drive cam is transmitted to the valve body via the variable mechanism, the split-type rocking mechanism, and the valve actuating mechanism, which allows the valve body to be opened or closed. At this time, the variable mechanism can vary an amplitude of the rocking motion of the split-type rocking mechanism corresponding to the rotating angle of the control shaft, so that a lift amount of the valve body can be variably set. The connection selection mechanism can cancel the connected state between the input member and the output member as necessary. In a condition, in which the connected state is canceled, the input of the drive cam is absorbed between the input member and the output member, so that the input is not transmitted to the valve body side. The valve body can therefore be brought to a pause. 
     In this case, the connection selection mechanism can connect, or disconnect, the input member and the output member regardless of the variable mechanism varying the lift amount of the valve body. Accordingly, the connection selection mechanism can quickly bring the valve body operating with any given lift amount to a pause state. The connection selection mechanism can also quickly return the valve body in the pause state to any given lift amount. Specifically, the connection selection mechanism can smoothly effect pause and return operations of the valve body regardless of whether the lift amount is large or small. There is therefore no need to go through unnecessary lift amounts as in the known art when bringing the valve body to a pause or returning the valve body therefrom. This permits smooth control of the lift amount and improves control response. 
     In accordance with the second aspect of the present invention, the input member and the output member can be integrally or individually rocked about the control shaft. By using the control shaft as a pivot, therefore, the rocking mechanism capable of being connected and disconnected can be compactly disposed on the outer peripheral side of the control shaft. The foregoing arrangement eliminates the need for complicated link parts or the like for selecting power drive transmission between the drive cam and the valve actuating mechanism. This helps simplify the structure, and promote reduction in size, of the entire system. Further, the aspect of the present invention may be applicable to the variable valve apparatus incorporating the known rocking cam arm by simply changing the rocking cam arm to the split type. The aspect of the present invention can therefore be applied easily by making only small-scale changes. 
     In accordance with the third aspect of the present invention, the split-type rocking mechanism can be formed symmetrically about the specific plane perpendicular to the control shaft. A transmission path, along which a force on the side of the variable mechanism is transmitted to the valve actuating mechanism via the split-type rocking mechanism, may be disposed on the plane. Specifically, various parts of the split-type rocking mechanism can be disposed symmetrically about this transmission path. As a result, when the input of the drive cam is applied to the split-type rocking mechanism, the foregoing arrangement prevents, for example, any torsional force or moment from acting on the split-type rocking mechanism. Accordingly, play in parts constituting the split-type rocking mechanism or reduction in durability of those parts can be suppressed, thus enhancing rigidity. Force by the split-type rocking mechanism can therefore be stably and efficiently transmitted. 
     In accordance with the fourth aspect of the present invention, the input side abutment portion receiving the force from the side of the variable mechanism and the output side abutment portion outputting the force to the valve actuating mechanism can be disposed linearly in a condition of not being inclined (deviated) relative to the control shaft. Then, the outer support portions and the inner support portions can respectively be disposed symmetrically about above portions. This helps prevent, for example, any torsional force or moment from acting on the split-type rocking mechanism and the force by the split-type rocking mechanism can be stably and efficiently transmitted. 
     In accordance with the fifth aspect of the present invention, when a valve mechanism having the valve body, the split-type rocking mechanism, the connection selection mechanism, and the valve actuating mechanism is disposed on each of the first and second sides, the variable mechanism can be disposed between the valve mechanism on the first side and the valve mechanism on the second side. In this condition, the variable mechanism can transmit, while receiving the input of the drive cam with the center cam roller, the input to the split-type rocking mechanism on the first side and the split-type rocking mechanism on the second side, respectively, using the intermediate rollers on both sides. This allows the variable mechanism to perform power drive transmission from the drive cam to the split-type rocking mechanisms on both sides in a well-balanced manner through the symmetrical path. Not being subject to torsional force or moment as a whole, the variable mechanism can therefore perform power transmission in a stable manner. In addition, the lift amount of the two valve mechanisms can be varied using the single variable mechanism, which helps build the variable valve apparatus having the plurality of valve bodies compactly. 
     In accordance with the sixth aspect of the present invention, the non-split-type rocking mechanism can be formed as an integral rocking mechanism having no input or output members, or the like. The valve mechanism having the split-type rocking mechanism can be disposed on the first side of the control shaft, while the valve mechanism having the non-split-type rocking mechanism can be disposed on the second side of the control shaft. The variable mechanism can be disposed between these valve mechanisms. Substantially in the same manner as in the fifth aspect of the present invention, therefore, power drive transmission from the drive cam to the valve mechanisms on both sides can be performed in a well-balanced manner. 
     The non-split-type rocking mechanism on the second side can transmit the input of the drive cam to the valve actuating mechanism on the second side at all times. Accordingly, if the connected state of the split-type rocking mechanism on the first side is canceled by the connection selection mechanism, the valve body on the second side can perform ordinary open/close operations with the valve body on the first side set in a closed pause state. If the variable valve apparatus is applied to an intake valve of an internal combustion engine, only an intake port on a first side of two intake ports disposed in a combustion chamber of the internal combustion engine can be held in a closed position by the intake valve. At an intake port on a second side, air can be drawn into the combustion chamber as the intake valve opens and closes. Consequently, swirl control or the like that generates a swirl flow of an intake air in the combustion chamber can be easily performed. 
     In accordance with the seventh aspect of the present invention, when the variable valve apparatus is stationary (that is, is not being driven), the connection selection mechanism can retain the connected state between the input member and the output member. A setting can therefore be made to let the valve body perform the ordinary open/close operations in an initial condition such as when the mechanism is started. Accordingly, the variable valve apparatus or an apparatus mounted with the same can start operating in an ordinary condition at any time. 
     In accordance with the eighth aspect of the present invention, the input member and the output member can be retained in the connected state when the internal combustion engine is stationary, in which no hydraulic pressure is supplied to the connection selection mechanism. When the internal combustion engine is started, therefore, the valve body can be opened or closed in the ordinary condition at all times, ensuring smooth operation control upon starting. 
     In accordance with the ninth aspect of the present invention, when supply of the hydraulic pressure to the disengagement means is suspended, the movable pin can be engaged with the engagement hole by the retention means. Accordingly, the input member and the output member can be connected together and the valve body can be opened or closed. When the hydraulic pressure is supplied to the disengagement means, the movable pin can be disengaged from the engagement hole. Accordingly, the input member and the output member can be disconnected from each other and the valve body can be brought to a pause state. A connection selection mechanism of a simple structure of engaging and disengaging the movable pin with/from the engagement hole can therefore be achieved and the connection selection mechanism can be disposed compactly in the split-type rocking mechanism. 
     In accordance with the tenth aspect of the present invention, when the movable pin of the connection selection mechanism is disengaged from the engagement hole, the input member can make a rocking motion relative to the output member. In this case, the input member makes a rocking motion relative to the output member for every revolution of the drive cam and the engagement hole and the movable pin can be made to oppose each other at least at one location within the rocking range. When the valve body is to be returned from the pause state, therefore, the movable pin can be engaged with the engagement hole within such a short period of time that the drive cam makes about one revolution after the selection operation is performed for return. 
     In accordance with the eleventh aspect of the present invention, the hydraulically-operated connection selection mechanism can be disposed compactly between the input member and the output member of the split-type rocking mechanism. The hydraulic pressure can be supplied to the connection selection mechanism through the first oil path disposed in the control shaft and the second oil path disposed in the input member or the output member. This eliminates the need, for example, for disposing the connection selection mechanism in the variable mechanism having a relatively complicated structure, or disposing the oil path in the variable mechanism. Accordingly, a space for disposing the connection selection mechanism and the oil path can be easily found, helping simplify the structure of the variable valve apparatus. 
     In accordance with the twelfth aspect of the present invention, the input side urge means can urge the input member of the split-type rocking mechanism toward the variable mechanism. This allows the input member and the variable mechanism to be pressed toward the side of the drive cam, making these members follow the profile of the drive cam to operate smoothly. Further, the output side urge means can urge the output member toward the valve actuating mechanism. Then, any play or the like can be prevented from occurring in the output member that is placed in a free state when connection between the input member and the output member is canceled. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view showing a general arrangement of a variable valve apparatus according to the first embodiment of the present invention. 
         FIG. 2  is a cross-sectional view showing a condition, in which the variable valve apparatus is assembled in an internal combustion engine. 
         FIG. 3  is an exploded perspective view showing the control shaft of the variable valve apparatus, variable mechanism and the split-type rocking cam arms. 
         FIG. 4  is a perspective view showing a condition, in which the split-type rocking cam arms are assembled/re-assembled together. 
         FIG. 5  is a transverse section view showing a condition, in which the split-type rocking cam arms break off along the plane perpendicular to the control shaft. 
         FIG. 6  is a view where the split-type rocking cam arms is seen from the left side in  FIG. 5 . 
         FIG. 7  is a longitudinal-sectional view showing the control shaft, the split-type rocking cam arms and the connection selection mechanism break with a plane along the axis of the control shaft. 
         FIG. 8  is a longitudinal-sectional view showing a condition, in which the connection between the input arm and the output arm shown in  FIG. 7  is canceled. 
         FIG. 9  is an essential part enlarged view of  FIG. 2 , showing the around split-type rocking cam arms. 
         FIG. 10  is a view showing the function of a lost motion spring and an auxiliary spring in  FIG. 9 . 
         FIG. 11  is a view showing a condition, in which the variable valve apparatus set to have a large lift amount are closed. 
         FIG. 12  is a view showing a condition, in which the variable valve apparatus shown in  FIG. 11 , are open. 
         FIG. 13  is a view showing a condition, in which the variable valve apparatus are brought into a pause state. 
         FIG. 14  is a view showing a condition, in which the connection selection mechanism with the valve pause state as in the case of the large lift amount. 
         FIG. 15  shows a condition, in which the variable valve apparatus set to have a small lift amount are closed. 
         FIG. 16  shows a condition, in which the variable valve apparatus shown in  FIG. 15 , are opened. 
         FIG. 17  is a view showing a condition, in which the variable valve apparatus shown in  FIG. 15 , are brought into a pause state. 
         FIG. 18  is a perspective view showing a general arrangement of a variable valve apparatus according to the second embodiment of the present invention. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     First Embodiment 
     Arrangement of the Variable Valve Apparatus According to the First Embodiment 
     A variable valve apparatus according to a first embodiment of the present invention will be described below with reference to  FIGS. 1 through 10 . 
       FIG. 1  is a perspective view showing a general arrangement of a variable valve apparatus  10  according to the first embodiment of the present invention.  FIG. 2  is a cross-sectional view showing a condition, in which the variable valve apparatus  10  is assembled in a cylinder head H (only part thereof is shown) of an internal combustion engine. For the first embodiment of the present invention, the internal combustion engine mounted with the variable valve apparatus  10  will be described as a four-valve type internal combustion engine having two each intake valves and exhaust valves for each cylinder. Further, the first embodiment of the present invention exemplifies the variable valve apparatus  10  as applied to two intake valves  12 ,  14  disposed in a single cylinder. In  FIG. 1 , reference numerals shown in parentheses denote those elements that are hidden behind other visible elements. 
     Referring to  FIGS. 1 and 2 , the intake valves  12 ,  14  open or close two corresponding intake ports (not shown) disposed in a single cylinder of the internal combustion engine. It is to be noted herein that the cylinder head H has valve springs (not shown) urging the intake valves  12 ,  14  toward a valve closing direction (upward in  FIGS. 1 and 2 ) at all times. 
     When the internal combustion engine is operated, a driving force (an input) of a drive cam  22  to be described later is transmitted to the intake valves  12 ,  14  via a variable mechanism  26 , split-type rocking cam arms  38 ,  40 , and valve actuating mechanisms  68 ,  70 . The intake valves  12 ,  14  are thereby opened or closed. In  FIG. 1 , the intake valve  12 , the split-type rocking cam arm  38 , and the valve actuating mechanism  68 , which are disposed on the right-hand side constitute a first set of valve mechanism. Further, the intake valve  14 , the split-type rocking cam arm  40 , and the valve actuating mechanism  70 , which are disposed on the left-hand side of the  FIG. 1 , constitute a second set of valve mechanism. These two sets of valve mechanisms are disposed apart from each other axially along a control shaft  24  to be described later, one being disposed on a first side and the other being disposed on a second side. The variable mechanism  26  is disposed between the valve mechanism on the first side and the valve mechanism on the second side. 
     A power drive transmission flow of the first embodiment of the present invention will be described below. The cylinder head H of the internal combustion engine includes a camshaft  20 . The camshaft  20  is directly connected to an output shaft of the internal combustion engine, rotatably driven in time with an engine speed. The drive cam  22  is fixed on an outer periphery of the camshaft  20 . The drive cam  22  has a profile setting open/close timing of the intake valves  12 ,  14 . 
     The control shaft  24  is rotatably mounted in the cylinder head H at a position near the camshaft  20 . The control shaft  24  is rotatably driven by a lift amount control actuator (not shown), controlling the lift amount of the intake valves  12 ,  14  according to the rotating angle thereof. The control shaft  24  is mounted with the variable mechanism  26  that is displaceable relative to the drive cam  22 . 
     (Arrangement of the Variable Mechanism) 
     The variable mechanism  26  will be described below with reference to  FIG. 3 . The variable mechanism  26  includes a fixing portion  28 , an arm portion  30 , a cam roller  32 , and intermediate rollers  34 ,  36 . The fixing portion  28  is formed annularly and fitted by insertion to an outer peripheral side of the control shaft  24  between the split-type rocking cam arms  38 ,  40 . The fixing portion  28  includes a lock pin  28   a  which, in turn, is fitted by insertion into amounting hole  24   a  made in an outer peripheral surface of the control shaft  24 . This results in the fixing portion  28  being fixed to the outer peripheral side of the control shaft  24  with relative rotation thereof being restricted. 
     The arm portion  30  is curved into a substantially C shape. The arm portion  30  has a proximal end thereof rotatably connected to the fixing portion  28 . The arm portion  30  has a distal end thereof protruding in a diametrical direction of the control shaft  24 . The three rollers  32 ,  34 ,  36  are rotatably mounted coaxially side by side on the protruding distal end. 
     In this case, the cam roller  32  disposed at an axial center abuts against the drive cam  22 . The state of the abutment is retained by a spring force of a lost motion spring  64  (see  FIG. 2 ) to be described later. Accordingly, when the drive cam  22  rotates, the cam roller  32  follows a profile of the drive cam  22  to make a reciprocating motion. 
     The intermediate rollers  34 ,  36  are disposed on both sides axially of the cam roller  32 . The intermediate roller  34  on a first side abuts against an input arm  42  of the split-type rocking cam arm  38 . The intermediate roller  36  on a second side abuts against an input, arm  44  of the split-type rocking cam arm  40 . The state of the abutment between the intermediate rollers  34 ,  36  and the input arms  42 ,  44  is retained by the spring force of the lost motion spring  64 . The intermediate rollers  34 ,  36  make a reciprocating motion with the cam roller  32  that receives the input of the drive cam  22 , so that the reciprocating motion is transmitted to the input arms  42 ,  44 , respectively. 
     When the control shaft  24  is rotated, the arm portion  30  is pulled or moved so as to apply pressure according to a rotating angle of the control shaft  24 . As a result, each of the rollers  32 ,  34 ,  36  is displaced close to, or away from, the control shaft  24  (in a substantially diametrical direction of the control shaft  24 ) and retained in a position corresponding to the rotating angle of the control shaft  24 . As a result, the split-type rocking cam arms  38 ,  40  make a rocking motion with amplitude corresponding to the position of the intermediate rollers  34 ,  36 , so that a lift amount of the intake valves  12 ,  14  is variable corresponding to the amplitude. 
     (Arrangement of the Split-Type Rocking Cam Arm) 
     The split-type rocking cam arms  38 ,  40  (hereinafter referred to simply as rocking cam arms  38 ,  40 ) will be described below. The rocking cam arms  38 ,  40  are disposed on first and second axial ends of the variable mechanism  26 , respectively. The rocking cam arms  38 ,  40  are rockably mounted on the outer peripheral side of the control shaft  24 . In addition, the rocking cam arms  38 ,  40  include the input arms  42 ,  44  and output arms  46 ,  48 , respectively. 
       FIGS. 4 to 6  are views showing the input arm  42  and the output arm  46  constituting the split-type rocking cam arm  38  on the first side. The input arm  42  includes a plate-like intermediate roller abutment portion  42   a , two outer support portions  42   b ,  42   b , and a spring retainer portion  42   c . The two outer support portions  42   b ,  42   b  are substantially annularly shaped. The intermediate roller abutment portion  42   a  has a proximal end thereof fixed to each of the outer support portions  42   b ,  42   b  and a distal end thereof protruding diametrically from the outer support portions  42   b ,  42   b . The intermediate roller abutment portion  42   a  has a front surface, on which a roller surface  42   d  receiving the input from the intermediate roller  34  on the first side is formed. 
     The two outer support portions  42   b ,  42   b  are disposed on both sides of the intermediate roller abutment portion  42   a , being axially spaced apart from each other. The outer support portions  42   b ,  42   b  are slidably fitted by insertion on the outer peripheral side of, and rockably supported by, the control shaft  24 . The intermediate roller abutment portion  42   a  and the spring retainer portion  42   c  are fixed between the two outer support portions  42   b ,  42   b . The spring retainer portion  42   c  is disposed on a side diametrically opposite the intermediate roller abutment portion  42   a  across the outer support portions  42   b ,  42   b . The spring retainer portion  42   c  protrudes diametrically from the outer support portions  42   b ,  42   b . The spring retainer portion  42   c  receives the spring force of the lost motion spring  64  (see  FIG. 2 ) to be described later. 
     The output arm  46  includes a plate-like rocker roller abutment portion  46   a , a tubular inner support portion  46   b , and a spring retainer portion  46   c . The rocker roller abutment portion  46   a  protrudes diametrically from the inner support portion  46   b . The rocker roller abutment portion  46   a  has a front surface, on which a cam surface  46   d  outputting rocking motion to a rocker roller  74  to be described later is formed. The inner support portion  46   b  is slidably fitted by insertion on the outer peripheral side of, and rockably supported by, the control shaft  24 . Further, the spring retainer portion  46   c  protrudes diametrically from the inner support portion  46   b  to receive the spring force of an auxiliary spring  66  (see  FIG. 2 ) to be described later. 
     Referring to  FIGS. 5 and 6 , in a condition, in which the input arm  42  and the output arm  46  are assembled together, the inner support portion  46   b  of the output arm  46  is disposed between the outer support portions  42   b  of the input arm  42 . In this condition, the intermediate roller abutment portion  42   a  and the rocker roller abutment portion  46   a  overlap each other at the same axial position. 
     Specifically, the abutment portions  42   a ,  46   a  and the support portions  42   b ,  46   b  are formed substantially symmetrically on both axial sides about a plane P shown in  FIG. 6 . The plane P passes through an axial middle position of the intermediate roller  34  and the rocker roller  74  and is perpendicular to the control shaft  24 . To state it another way, the intermediate roller  34  receiving the input from the drive cam  22 , the abutment portions  42   a ,  46   a , and the rocker roller  74  are disposed linearly not being inclined (deviated) relative to the control shaft  24 , while the support portions  42   b ,  46   b  support the abutment portions  42   a ,  46   a  at positions symmetrical about the above-referenced members on both sides thereof. 
     A connection selection mechanism  50  to be described later is disposed between the input arm  42  and the output arm  46 . The input arm  42  and the output arm  46 , when connected with each other by the connection selection mechanism  50 , make a rocking motion integrally about the control shaft  24 . When the connected state between the arms  42  and  46  is canceled, the input arm  42  and the output arm  46  become individually rockable. As a result, the rocking motion of the input arm  42  is no longer transmitted to the output arm  46 , bringing the intake valve  12  to a pause state. 
     (Arrangement of the Split-Type Rocking Cam Arm on the Second Side) 
     Referring to  FIGS. 1 and 3 , the input arm  44  and the output arm  48 , which constitute the rocking cam arm  40  on the second side, have substantially the same arrangement as the rocking cam arm  38  on the first side. Specifically, the input arm  44  includes an intermediate roller abutment portion  44   a , an outer support portion  44   b , a spring retainer portion  44   c , and a roller surface  44   d . The output arm  48  includes a rocker roller abutment portion  48   a , an inner support portion  48   b , a spring retainer portion  48   c , and a cam surface  48   d . The rocking cam arm  40  also includes the connection selection mechanism  50 , the auxiliary spring  66 , and the lost motion spring  64 . These elements are not shown. 
     (Arrangement of the Connection Selection Mechanism) 
     Referring to  FIGS. 7 and 8 , the connection selection mechanism  50  of a hydraulically operated type disposed in the rocking cam arms  38 ,  40  will be described below. The connection selection mechanism  50  on the side of the rocking cam arm  38  will be described as an example. 
     The connection selection mechanism  50  includes an engagement hole  52 , a movable pin  54 , a retention spring  56 , a piston  58 , and oil paths  60 ,  62 . In accordance with the first embodiment of the present invention, the input arm  42  of the two arms  42 ,  46  constituting the rocking cam arm  38  includes the engagement hole  52 , while the output arm  46  includes the movable pin  54 . 
     A first one of the two outer support portions  42   b ,  42   b  constituting the input arm  42  includes the engagement hole  52  formed as a blind hole opening to an inner end face thereof. Further, a shoulder portion  52   a  for setting the maximum advance position of the movable pin  54  is formed in a protruding condition diametrically inwardly on a bottom side of the engagement hole  52 . A second one of the two outer support portions  42   b ,  42   b  includes a machined hole  52   b  used for drilling the engagement hole  52 . 
     The movable pin  54  is slidably fitted by insertion in a pin hole  54   a  formed in the inner support portion  46   b  of the output arm  46 . In this case, the pin hole  54   a  is formed as a blind hole opening to an end face of the inner support portion  46   b . A shoulder portion  54   b  for setting the maximum advance position of the movable pin  54  and a vent hole  54   c  permitting entry and exit of air in and out of the pin hole  54   a  are formed on a bottom side of the pin hole  54   a.    
     Referring to  FIGS. 7 and 8 , the movable pin  54  engages with or disengages from the engagement hole  52  according to a hydraulic pressure supplied to the engagement hole  52 , so that the input arm  42  is connected with or disconnected from the output arm  46 . 
     The retention spring  56  is disposed in a compressed state between the movable pin  54  and the bottom side of the pin hole  54   a . The retention spring  56  urges the movable pin  54  at all times toward the engagement hole  52 . This results in the movable pin  54  being retained in an engaged state in the engagement hole  52  when the hydraulic pressure does not act on the piston  58 . The piston  58 , on the other hand, is slidably fitted in an open side of the engagement hole  52 . 
     The piston  58  moves the movable pin  54  so as to apply pressure thereto against a spring force of the retention spring  56  when the hydraulic pressure is supplied into the engagement hole  52  from the oil path  60  to be described later, so that the movable pin  54  is disengaged from the engagement hole  52 . As such, the connection selection mechanism  50  keeps the input arm  42  and the output arm  46  in a connected state at all times (when no hydraulic pressure is supplied into the engagement hole  52 ). When the hydraulic pressure generated when the internal combustion engine operates is supplied, the connection selection mechanism  50  is driven by the hydraulic pressure, disconnecting the above-referenced connection. 
     The two oil paths  60 ,  62  provided as an adjunct for the connection selection mechanism  50  will be described below. A first oil path  60  is connected to a hydraulic control circuit (not shown) or the like serving as a hydraulic pressure source for cylinder pause control. The first oil path  60  is drilled axially in the control shaft  24 . Part of the oil path  60  branches diametrically at a position corresponding to the outer support portion  42   b  of the input arm  42  and is opened in an outer peripheral surface of the control shaft  24 . The opening includes a slot  60   a  (see  FIG. 3 ) extending in a circumferential direction to have a length corresponding to a rotation range of the control shaft  24 . 
     A second oil path  62  is drilled diametrically in the outer support portion  42   b  of the input arm  42  at a position opposing the slot  60   a . Accordingly, the two oil paths  60 ,  62  are held in a connected state through the slot  60   a  even when the control shaft  24  rotates. The oil path  62  is open to the engagement hole  52 . Further, the oil path  60  is also connected to the connection selection mechanism  50  of the rocking cam arm  40  on the second side through an oil path  62  on the second side (not shown) formed in the same manner as the oil path  62  on the first side. Accordingly, when a hydraulic pressure is outputted from the hydraulic control circuit, the hydraulic pressure is supplied to the engagement hole  52  of the connection selection mechanism  50  on each of the first and second sides through the oil paths  60 ,  62 . An operating state of these connection selection mechanisms  50  is together selected. 
     The first embodiment of the present invention is thus arranged such that, when the hydraulic pressure is outputted to the oil path  60  from the hydraulic control circuit, the hydraulic pressure is supplied to the valve mechanisms on the first and second sides through the two oil paths  62 , thereby bringing both intake valves  12 ,  14  to a pause at the same time. The present invention is not limited to the foregoing arrangement; rather, for example, only either one of the intake valves  12 ,  14  may be adapted to be brought to a pause state. In this arrangement, the oil path  60  according to the first embodiment of the present invention is, for example, is split in a midway point, so that an oil path  60  connected to an oil path  62  on the first side and an oil path  60  connected to an oil path  62  on the second side are formed independently of each other. The hydraulic pressure is then supplied to each of the two oil paths  60  independently of each other. 
     (Arrangement of the Spring) 
     The lost motion spring  64  and the auxiliary spring  66  provided as adjuncts in the rocking cam arm  38  on the first side will be described with reference to  FIGS. 9 and 10 . The lost motion spring  64  is disposed between the spring retainer portion  42   c  of the input arm  42  and the cylinder head H in a compressed state. The lost motion spring  64  urges the input arm  42  in a clockwise direction (in a direction of an arrow F 1  in  FIG. 10 ) about the control shaft  24 . As a result, the lost motion spring  64  presses the intermediate roller abutment portion  42   a  of the input arm  42  up against the intermediate roller  34  and the cam roller  32  up against the drive cam  22  via the intermediate roller  34 . 
     The auxiliary spring  66  is disposed between the spring retainer portion  46   c  of the output arm  46  and the cylinder head H in a compressed state. The auxiliary spring  66  urges the output arm  46  in a counterclockwise direction (in a direction of an arrow F 2  in  FIG. 10 ). As a result, the auxiliary spring  66  presses the rocker roller abutment portion  46   a  of the output arm  46  up against the rocker roller  74 , thus preventing any play from occurring in the foregoing elements. 
     (Arrangement of the Valve Actuating Mechanism) 
     The valve actuating mechanisms  68 ,  70  that translate the rocking motion of the output arms  46 ,  48  to a corresponding open/close operation of the intake valves  12 ,  14  will be described below. Referring to  FIG. 1 , the valve actuating mechanism  68  on a first side includes a rocker arm  72 , the rocker roller  74 , and a lash adjuster  76 . A valve stem  16  of the intake valve  12  is rockably connected to a first end side of the rocker arm  72 . The rocker arm  72  has a second end side rockably supported by the lash adjuster  76 . The rocker roller  74  is rotatably disposed at an intermediate portion of the rocker arm  72 . 
     When the output arm  46  moves the rocker roller  74  so as to apply pressure thereto, the rocker arm  72  makes a rocking motion about a leading end portion of the lash adjuster  76 . The intake valve  12  is thereby opened or closed. The valve actuating mechanism  70  on a second side also includes, as in the valve actuating mechanism  68  on the first side, a rocker arm  78 , and a rocker roller and a lash adjuster (shown only partly). The valve actuating mechanism  70  transmits a rocking motion of the output arm  48  to a valve stem  18  of the intake valve  14 , so that the intake valve  14  is opened or closed. 
     [Operation of the First Embodiment] 
     Referring to  FIGS. 11 through 17 , operation of the variable valve apparatus  10  according to the first embodiment of the present invention will be described below. The two valve mechanisms (intake valves  12 ,  14 ) perform the same open/close operations.  FIGS. 11 through 17  therefore illustrate operations of the valve mechanism on the first side (intake valve  12 ). 
     (Open/Close Operation Involving a Large Lift Amount) 
       FIGS. 11 and 12  are views showing a condition, in which a large lift amount of the intake valves  12 ,  14  is set. Specifically,  FIG. 11  shows a condition, in which the intake valves  12 ,  14  set to have a large lift amount are closed, while  FIG. 12  shows a condition, in which the intake valves  12 ,  14  are open. 
     To increase the lift amount, the control shaft  24  is rotated in a predetermined direction (counterclockwise according to the first embodiment of the present invention) by the lift amount control actuator. As a result, the rollers  32 ,  34 ,  36  of the variable mechanism  26  are pulled in a direction of approaching the control shaft  24  by way of the arm portion  30 , and are retained at a position resulting in a large lift amount. At this position, the intermediate rollers  34 ,  36  abut against the proximal end sides of the intermediate roller abutment portions  42   a ,  44   a  of the input arms  42 ,  44 . 
     Supply of hydraulic pressure to the oil path  60  shown in  FIG. 7  is suspended in order to open or close the intake valves  12 ,  14 . Accordingly, the movable pin  54  of the connection selection mechanism  50  is retained in the engaged state in the engagement hole  52  by the spring force of the retention spring  56 . Accordingly, the input arm  42  and the output arm  46 , and the input arm  44  and the output arm  48 , are respectively connected together by the connection selection mechanism  50 . 
     If the internal combustion engine operates in this condition, the drive cam  22  is rotatably driven and the cam roller  32  follows the profile of the drive cam  22  to make a reciprocating motion as shown in  FIGS. 11 and 12 . At this time, the intermediate rollers  34 ,  36  make a reciprocating motion on the proximal end side of the intermediate roller abutment portions  42   a ,  44   a  with the cam roller  32 , thereby rocking the input arms  42 ,  44  with a large amplitude. The rocking motion is transmitted to the rocker arms  72 ,  78  by the output arms  46 ,  48  making a rocking motion with the input arms  42 ,  44 . As a result, the rocker arms  72 ,  78  make a rocking motion with a large amplitude, causing the intake valves  12 ,  14  to open/close with a large lift amount. 
     (Valve Pause Operation Involving a Large Lift Amount) 
       FIG. 13  is a view showing a condition, in which the intake valves  12 ,  14  being opened or closed with a large lift amount are brought into a pause state. To let the intake valves  12 ,  14  pause, a hydraulic pressure is applied to the oil path  60  (see  FIG. 7 ) from the hydraulic control circuit for cylinder pause control. The hydraulic pressure is supplied to the engagement hole  52  of the connection selection mechanism  50  on each of the first and second sides via the oil paths  60 ,  62 , and the like. As a result, in each connection selection mechanism  50 , the piston  58  moves the movable pin  54  so as to apply pressure thereto against the spring force of the retention spring  56 , so that the movable pin  54  is disengaged from the engagement hole  52 . This disconnects the connection between the input arm  42  and the output arm  46 , and between the input arm  44  and the output arm  48 , respectively. 
     In this connection disengaged state, referring to  FIGS. 11 and 13 , the input arms  42 ,  44  only make a rocking motion even if the reciprocating motion of the intermediate rollers  34 ,  36  is transmitted to the input arms  42 ,  44 . At this time, the output arms  46 ,  48  are in a free state on the periphery of the control shaft  24 ; however, the spring force of the auxiliary spring  66  presses the output arms  46 ,  48  up against the rocker roller  74 , so that the output arms  46 ,  48  are held in a stationary state. As such, the input arms  42 ,  44  make a rocking motion relative to the output arms  46 ,  48 , so that the input of the drive cam  22  is absorbed. As a result, the input of the drive cam  22  is not transmitted to the rocker arms  72 ,  78 , thus making the intake valves  12 ,  14  in a closed pause state. 
     (Return from the Valve Pause State) 
     To return the intake valves  12 ,  14  in a temporary pause state to a normal operating condition, the hydraulic pressure supply to the oil path  60  is suspended in  FIG. 7 . When the supply of the hydraulic pressure is halted, the movable pin  54  is made to abut against the end face of the input arms  42 ,  44  (the outer support portions  42   b ,  44   b ) by the spring force of the retention spring  56 . As the input arms  42 ,  44  make a rocking motion to cause the movable pin  54  to be disposed opposing the engagement hole  52 , the movable pin  54  is pushed into engagement with the engagement hole  52 . As a result, the input arms  42 ,  44  and the output arms  46 ,  48 , are respectively connected together by the movable pin  54 , so as to make a rocking motion integrally. The intake valves  12 ,  14  then resume the ordinary open/close operations. 
     (Positional Relationship Between the Engagement Hole  52  and the Movable Pin  54 ) 
     In the abovementioned valve pause state, the input arms  42 ,  44  make a rocking motion within a rocking range θ corresponding to the lift amount setting for each revolution of the drive cam  22  as shown in  FIG. 14 . The rocking range θ has a reference point at a center O of the control shaft  24 . When the input arms  42 ,  44  make a rocking motion, the engagement hole  52  of the connection selection mechanism  50  also makes a rocking motion within the rocking range θ relative to the movable pin  54 . The engagement hole  52  and the movable pin  54  are, however, disposed so as to oppose each other at least one position within the rocking range θ. 
     Accordingly, when the intake valves  12 ,  14  are to be returned from the pause state, the engagement hole  52  and the movable pin  54  reaches the mutually opposing position during a period of one revolution of the drive cam  22  at a maximum after the halt of the hydraulic pressure supply to the oil path  60 . At this mutually opposing position, the movable pin  54  can be engaged in the engagement hole  52 . 
     (Open/Close Operation Involving a Small Lift Amount) 
       FIGS. 15 and 16  are views showing a condition, in which the lift amount of the intake valves  12 ,  14  is set small. Specifically,  FIG. 15  shows a condition, in which the intake valves  12 ,  14  set to have a small lift amount are closed, while  FIG. 16  shows a condition, in which the intake valves  12 ,  14  are opened. 
     To decrease the lift amount, the control shaft  24  is rotated in a direction opposite that for increasing the lift amount (clockwise). As a result, the rollers  32 ,  34 ,  36  of the variable mechanism  26  are pushed in a direction of moving away from the control shaft  24  by way of the arm portion  30  and retained at a position resulting in a small lift amount. At this position, the intermediate rollers  34 ,  36  abut against the distal end sides of the intermediate roller abutment portions  42   a ,  44   a  of the input arms  42 ,  44 . In addition, the input arms  42 ,  44  and the output arms  46 ,  48  are in a connected state. 
     If the input of the drive cam  22  is transmitted to the intermediate rollers  34 ,  36  in this condition, the intermediate rollers  34 ,  36  make a reciprocating motion on the distal end side of the intermediate roller abutment portions  42   a ,  44   a , thus rocking the input arms  42 ,  44  with a small amplitude. The rocking motion is transmitted to the intake valves  12 ,  14  via the valve actuating mechanisms  68 ,  70 , so that the intake valves  12 ,  14  can be opened or closed with a small lift amount. 
     (Valve Pause Operation Involving a Small Lift Amount) 
       FIG. 17  is a view showing a condition, in which the intake valves  12 ,  14  being opened or closed with a small lift amount are brought into a pause state. To let the intake valves  12 ,  14  pause, a hydraulic pressure is applied to the oil path  60  as in the case of the large lift amount. As a result, the connection selection mechanism  50  performs the same connection disengagement operation as in the case of the large lift amount. This disconnects the connection between the input arm  42  and the output arm  46 , and between the input arm  44  and the output arm  48 , respectively, bringing the intake valves  12 ,  14  to a pause state. 
     A narrower rocking range θ of the input arms  42 ,  44  results in the valve pause state involving the small lift amount as compared with the valve pause state involving the large lift amount described earlier ( FIG. 14 ). Consequently, even in this condition, the engagement hole  52  and the movable pin  54  of the connection selection mechanism  50  oppose each other at least at one place within the rocking range θ, substantially in the same manner as in the case of  FIG. 14 . Accordingly, even in the case of the small lift amount, the movable pin  54  can be engaged with the engagement hole  52  while the drive cam  22  makes one revolution. 
     [Characteristics of the First Embodiment] 
     The first embodiment of the present invention provides the arrangement, in which the rocking cam arm disposed between the variable mechanism  26  and the valve actuating mechanisms  68 ,  70  is formed as the split-type rocking cam arms  38 ,  40  that achieve a pause state of the intake valves  12 ,  14 . In this case, the connection selection mechanism  50  can connect, or disconnect, the input arms  42 ,  44  and the output arms  46 ,  48  regardless of the variable mechanism  26  varying the lift amount of the intake valves  12 ,  14 . 
     Accordingly, the connection selection mechanism  50  can quickly bring the intake valves  12 ,  14  operating with any given lift amount to a pause state. The connection selection mechanism  50  can also quickly return the intake valves  12 ,  14  in the pause state to any given lift amount. Specifically, the connection selection mechanism  50  can smoothly effect pause and return operations of the intake valves  12 ,  14  regardless of whether the lift amount is large or small. There is therefore no need to go through unnecessary lift amounts as in the known art when bringing the intake valves  12 ,  14  to a pause or returning the intake valves  12 ,  14  therefrom. This permits smooth control of the lift amount and improves control response. 
     In the first embodiment of the present invention, the input arms  42 ,  44  and the output arms  46 ,  48  are rockably mounted on the outer peripheral side of the control shaft  24 . This allows the input arms  42 ,  44  and the output arms  46 ,  48  to be integrally or individually rocked about the control shaft  24 . By using the control shaft  24  as a pivot, therefore, the rocking cam arms  38 ,  40  capable of being connected and disconnected can be compactly disposed on the outer peripheral side of the control shaft  24 . 
     The foregoing arrangement eliminates the need for complicated link parts or the like for selecting power drive transmission between the drive cam  22  and the valve actuating mechanisms  68 ,  70 . This helps simplify the structure, and promote reduction in size, of the entire system. Further, the embodiment of the present invention may be applicable to the variable valve apparatus incorporating the known rocking cam arm by simply changing the rocking cam arm may to the split type. The embodiment of the present invention can therefore be applied by making only small-scale changes. 
     The input arm  42  and the output arm  46 , which constitute the rocking cam arm  38  on the first side, are shaped symmetrically on both axial sides about the plane P extending perpendicularly to the control shaft  24 . Accordingly, the intermediate roller  34 , the abutment portions  42   a ,  46   a , and the rocker roller  74  can be disposed linearly not being inclined (deviated) relative to the control shaft  24 . This also allows the support portions  42   b ,  46   b  to support the abutment portions  42   a ,  46   a  at positions symmetrical about the above-referenced members on both sides thereof. 
     When the input of the drive cam  22  is applied to the rocking cam arm  38 , the foregoing arrangement prevents, for example, any torsional force or moment from acting on the rocking cam arm  38 . Accordingly, play in parts constituting the rocking cam arm  38  or reduction in durability of those parts can be suppressed, thus enhancing rigidity. Force by the rocking cam arm  38  can therefore be stably and efficiently transmitted. The foregoing effects can likewise be achieved by the rocking cam arm  40  on the second side having the identical arrangements as the rocking cam arm  38  on the first side. 
     In accordance with the first embodiment of the present invention, the variable mechanism  26  is disposed between the valve mechanism on the first side (the intake valve  12 , the rocking cam arm  38 , valve actuating mechanism  68 , and the like) and the valve mechanism on the second side (the intake valve  14 , the rocking cam arm  40 , valve actuating mechanism  70 , and the like). This arrangement allows the variable mechanism  26  to receive the input of the drive cam  22  with the center cam roller  32  and to transmit the input to the rocking cam arms  38 ,  40  on the first and the second sides, respectively, with the intermediate rollers  34 ,  36  on both sides. 
     This allows the variable mechanism  26  to perform power drive transmission from the drive cam  22  to the rocking cam arms  38 ,  40  on both sides in a well-balanced manner through a symmetrical path. Not being subject to torsional force or moment as a whole, the variable mechanism  26  can therefore perform power transmission in a stable manner. In addition, the lift amount of the two valve mechanisms can be varied using the single variable mechanism  26 , which helps build the variable valve apparatus  10  having the plurality of intake valves  12 ,  14  compactly. 
     An arrangement is also made, in which the movable pin  54  of the connection selection mechanism  50  is normally engaged with the engagement hole  52  by the spring force of the retention spring  56  and, when the hydraulic pressure is supplied to the engagement hole  52 , the engagement is canceled. This arrangement permits the following. Specifically, when the internal combustion engine is started, the input arms  42 ,  44  and the output arms  46 ,  48  can be held in the connected state, allowing the intake valves  12 ,  14  to perform the ordinary open/close operations. Accordingly, the internal combustion engine can be normally started even if the preceding operation thereof has been terminated with the valves in the pause state, so that operation control upon starting can be smoothly performed. 
     The connection selection mechanism  50  is formed to include the engagement hole  52 , the movable pin  54 , the retention spring  56 , the piston  58 , and the like. This achieves the connection selection mechanism  50  of a simple structure of engaging and disengaging the movable pin  54  with/from the engagement hole  52 . The connection selection mechanism  50  can thereby be compactly disposed in the split-type rocking cam arms  38 ,  40 . 
     An arrangement is further made, in which the engagement hole  52  and the movable pin  54  of the connection selection mechanism  50  oppose each other at least at one place within the rocking range θ of the input arms  42 ,  44 . This arrangement permits the following. Specifically, when the intake valves  12 ,  14  are to be returned from the pause state, the movable pin  54  can be engaged with the engagement hole  52  within such a short period of time that the drive cam  22  makes about one revolution after the selection operation is performed for return. Accordingly, the intake valves  12 ,  14  can be quickly returned to any given lift amount from the pause state. 
     Further, the connection selection mechanism  50  is disposed between the input arms  42 ,  44  and the output arms  46 ,  48 , and the outer support portions  42   b ,  44   b  of the input arms  42 ,  44  include the oil path  62  supplying the connection selection mechanism  50  with the hydraulic pressure. This eliminates the need, for example, for disposing the connection selection mechanism  50  in the variable mechanism  26  having a relatively complicated structure, or disposing the oil path  62  in the variable mechanism  26 . Accordingly, a space for disposing the connection selection mechanism  50  and the oil path  62  can be easily found, helping simplify the structure of the variable valve apparatus  10 . 
     The variable valve apparatus  10  according to the first embodiment of the present invention is adapted to include the lost motion spring  64  and the auxiliary spring  66 . The lost motion spring  64  can therefore make the input arms  42 ,  44  press the intermediate rollers  34 ,  36 , and can make the cam roller  32  press the drive cam  22 . This makes the rollers  32 ,  34 ,  36  and the input arms  42 ,  44  follow the profile of the drive cam  22  to operate smoothly. 
     The auxiliary spring  66 , on the other hand, can urge the output arms  46 ,  48  toward the valve actuating mechanisms  68 ,  70 . Accordingly, the auxiliary spring  66  can prevent any play or the like in the output arms  46 ,  48  that are placed in a free state on the periphery of the control shaft  24  when connection between the input arms  42 ,  44  and the output arms  46 ,  48  is canceled. 
     Second Embodiment 
     A variable valve apparatus according to a second embodiment of the present invention will be described below with reference to  FIG. 18 . In the second embodiment, like reference numerals are assigned to like elements of the first embodiment and descriptions for the same are omitted. 
     [Characteristics of the Second Embodiment] 
     A variable valve apparatus  80  according to the second embodiment of the present invention is constructed substantially in the same manner as the first embodiment. The variable valve apparatus  80  includes intake valves  12 ,  14 , a drive cam  22 , a control shaft  24 , a variable mechanism  26 , a split-type rocking cam arm  38  on a first side, a connection selection mechanism on a first side (not shown), valve actuating mechanisms  68 ,  70 , and the like. The variable valve apparatus  80  differs in arrangements from the first embodiment of the present invention in that the variable valve apparatus  80  has a non-split-type rocking cam arm  82 , instead of the split-type rocking cam arm  40  on the second side incorporated in the first embodiment. 
     The non-split-type rocking cam arm  82  is integrally formed from, for example, a metal material, rockably disposed on an outer peripheral side of the control shaft  24 . When the non-split-type rocking cam arm  82  operates, therefore, the entire cam arm  82  makes a rocking motion integrally about the control shaft  24 . Accordingly, the non-split-type rocking cam arm  82  can transmit, at all times, an input of the drive cam  22  to the valve actuating mechanism  70  on the second side. 
     In the second embodiment of the present invention having the arrangements as described above, too, substantially the same effect can be achieved as in the first embodiment for the split-type rocking cam arm  38 . The rocking cam arms  38 ,  82 , being disposed on both sides of the variable mechanism  26 , permit power drive transmission from the drive cam  22  to the valve actuating mechanisms  68 ,  70  on both sides in a well-balanced manner. 
     Particularly noteworthy about the second embodiment of the present invention is that the rocking cam arm on the second side is formed as the non-split-type rocking cam arm  82 . Accordingly, if a connected state of the split-type rocking cam arm  38  on the first side is canceled, the intake valve  14  on the second side can perform ordinary open/close operations with the intake valve  12  on the first side set in a closed pause state. 
     As a result, in accordance with the second embodiment of the present invention, only an intake port on a first side of two intake ports disposed in a combustion chamber of an internal combustion engine can be held in a closed position by the intake valve  12 . At an intake port on a second side, air can be drawn into the combustion chamber as the intake valve  14  opens and closes. Consequently, swirl control or the like that generates a swirl flow of an intake air in the combustion chamber can be easily performed and the variable valve apparatus  80  to be applicable to the swirl control can be achieved. 
     In the first and second embodiments of the present invention described heretofore, the intake valves  12 ,  14  represent specific examples of the valve body and the split-type rocking cam arms  38 ,  40  represent specific examples of the split-type rocking mechanism. The non-split-type rocking cam arm  82  represents a specific example of the non-split-type rocking mechanism. The input arms  42 ,  44  and the output arms  46 ,  48  represent specific examples of the input member and the output member, respectively. The intermediate roller abutment portions  42   a ,  44   a  and the rocker roller abutment portions  46   a ,  48   a  represent specific examples of the input side abutment portion and the output side abutment portion according to the fourth aspect of the present invention, respectively. The retention spring  56  represents a specific example of the retention means according to the eighth aspect of the present invention and the piston  58  represents a specific example of the disengagement means, respectively. Further, the lost motion spring  64  and the auxiliary spring  66  represent specific examples of the input side urge means and the output side urge means, respectively, according to the eleventh aspect of the present invention. 
     In accordance with the first embodiment of the present invention, the input arms  42 ,  44  each include the engagement hole  52  of the connection selection mechanism  50  and the movable pin  54  is disposed in the output arms  46 ,  48 . The present invention is not limited to this arrangement and the output arms  46 ,  48  may include the engagement hole  52  and the movable pin  54  may be disposed in the input arms  42 ,  44 . In this case, the output arms  46 ,  48  may include oil paths for supplying the connection selection mechanism  50  with the hydraulic pressure as may be necessary. 
     The first embodiment of the present invention has been described using, as an example, the connection selection mechanism  50  that is a hydraulically operated type performing the selection operation according to the status of the hydraulic pressure supply. The present invention is not limited to this arrangement; rather, the connection selection mechanism may be of an electrically operated type performing the selection operation according to, for example, the status of energization. 
     In accordance with the first and second embodiments of the present invention, the variable valve apparatus  10 ,  80  are adapted to open and close the intake valves  12 ,  14 . The present invention is not limited to the disclosed embodiments; rather, an arrangement may be made, for example, to have the variable valve apparatus open or close a single valve body, or three or more valve bodies. 
     In accordance with the first and second embodiments of the present invention, the variable valve apparatus  10 ,  80  are applied to the intake valves  12 ,  14  of the internal combustion engine. The present invention is not limited to the disclosed embodiments; rather, the variable valve apparatus  10 ,  80  may still be applied to an exhaust valve of the internal combustion engine. Further, the present invention may be applicable to a wide range of valve bodies mounted in machines of various kinds, not limited only to the internal combustion engine.