Patent Publication Number: US-7213551-B2

Title: Variable valve operating device

Description:
TECHNICAL FIELD 
   The present invention relates to a variable valve operating device for an internal combustion engine, and more particularly to a variable valve operating device that is capable of mechanically changing the operating characteristic of a valve. 
   BACKGROUND ART 
   A conventionally known variable valve operating device that is disclosed, for instance, by Japanese Patent Laid-open No. 2003-239712 mechanically changes the valve lift amount and valve timing in accordance with the operating state of an engine. For the variable valve operating device described in Japanese Patent Laid-open No. 2003-239712, a control arm is fastened to a control shaft that is positioned in parallel with a camshaft, and one end of a follower is mounted on the control arm and allowed to swing freely. Further, a swing cam is mounted on the control shaft and allowed to swing freely. A rocker arm is pressed against the surface of the swing cam. A first roller and a second roller are concentrically mounted on the follower so that these rollers can rotate independently of each other. The first roller is in contact with a valve cam on the camshaft, and the second roller is in contact with a contact surface that is formed on the side away from the cam surface of the swing cam. 
   When the control arm rotation position changes due to control shaft rotation while the above configuration is employed, the follower becomes displaced so as to change the distance between the control shaft and the contact between the swing cam and second roller. Consequently, the valve lift amount changes. Further, the circumferential position of the valve cam, which comes into contact with the first roller, changes in the same rotation position of the camshaft. This causes the valve timing to change also. In other words, the variable valve operating device described in Japanese Patent Laid-open No. 2003-239712 can simultaneously change the valve lift amount and valve timing when the rotation position of the control shaft is controlled by a motor. 
   Including the above-mentioned document, the applicant is aware of the following documents as a related art of the present invention. 
   [Patent Document 1] 
   Japanese Patent Laid-open No. 2003-239712 
   [Patent Document 2] 
   Japanese Patent Laid-open No. Hei7-63023 
   [Patent Document 3] 
   Japanese Patent Laid-open No. Hei6-74011 
   [Patent Document 4] 
   Japanese Patent Laid-open No. Hei6-17628 
   [Patent Document 5] 
   Japanese Patent Laid-open No. Hei11-36833 
   DISCLOSURE OF THE INVENTION 
   In marked contrast to a normal valve apparatus that uses a cam to drive a rocker arm, the variable valve operating device described in Japanese Patent Laid-open No. 2003-239712 makes it necessary to install a mechanism comprising a plurality of members such as the control shaft, swing cam, control arm, follower, and roller within a cylinder head. In reality, however, the cylinder head has a limited amount of extra space. Therefore, when the complicated mechanism described above is to be installed in the cylinder head, it is necessary to change the positional relationship among existing members or enlarge the cylinder head. 
   The present invention has been made to solve the above problem. It is an object of the present invention to provide a variable valve operating device that is compact and capable of mechanically changing the operating characteristic of a valve. 
   The above object is achieved by a variable valve operating device according to a first aspect of the present invention. The variable valve operating device mechanically changes the operating characteristic of a valve in relation to the rotation of a camshaft. The variable valve operating device includes a drive cam installed over the camshaft and a control shaft positioned in parallel with the camshaft. The control shaft is capable of changing the rotation position continuously or stepwise. The variable valve operating device also includes a swing member that is installed over the control shaft and allowed to swing around the control shaft. A swing cam surface is formed on the swing member, comes into contact with a valve support member, which supports the valve, and presses the valve in a lifting direction. A slide surface is also formed on the swing member so as to face the drive cam. An intermediate member is positioned between the drive cam and the swing member and comes into contact with both the slide surface and a cam surface of the drive cam. A control member is installed over the camshaft and allowed to rotate. A support member is mounted on the control member to support the intermediate member so that the intermediate member can be moved along a predetermined path in relation to the control member. Further, the variable valve operating device includes a rotation interlock mechanism. The rotation interlock mechanism interlocks the rotation of the control member around the camshaft with the rotation of the control shaft. 
   According to the first aspect of the present invention, the rotation motion of the camshaft is transmitted from the cam surface of the drive cam to the slide surface of the swing member via the intermediate member and then converted to the swing motion of the swing member. The swing motion of the swing member is transmitted from the swing cam surface to the valve support member and then converted to the lift motion of the valve. In other words, the rotation motion of the camshaft is converted to the lift motion of the valve via the intermediate member and the swing member. 
   When the rotation position of the control shaft is changed, the rotation of the control shaft is transmitted to the control member via the rotation interlock mechanism so that the control member rotates around the camshaft. The intermediate member is supported by the control member via the support member. Therefore, when the control member rotates around the camshaft, the intermediate member also turns around the camshaft so as to change the intermediate member position on the drive cam surface and the intermediate member position on the slide surface. When the intermediate member position on the slide surface changes, the swing angle and initial swing position of the swing member change, thereby causing a change in the valve lift amount. Further, when the intermediate member position on the drive cam surface changes, the swing timing of the swing member changes in relation to the phase of the camshaft, thereby causing a change in the valve timing. 
   As described above, the first aspect of the present invention can mechanically change the operating characteristic by controlling the rotation position of the control shaft. Further, the first aspect of the present invention ensures that the support member, which supports the intermediate member, and the control member are positioned around the existing camshaft. Therefore, the resulting apparatus is compact. 
   According to a second aspect of the present invention, in the variable valve operating device according to the first aspect of the present invention, the support member may be formed as a guide that is integral with the control member. 
   According to the second aspect of the present invention, the support member and control member are integrated into the guide. Therefore, only the swing member and intermediate member move to lift the valve. This makes it possible to avoid an increase in the inertial mass of the entire movable section. 
   According to a third aspect of the present invention, in the variable valve operating device according to the second aspect of the present invention, the guide may be formed outward from the center of the camshaft. 
   According to the third aspect of the present invention, the guide is formulated outward from the center of the camshaft. This causes the intermediate member to reciprocate substantially in the radial direction of the camshaft in accordance with the rotation of the drive cam. Consequently, the intermediate member is inhibited from making an unnecessary move on the slide surface. This makes it possible to minimize the loss in the driving force transmission from the drive cam to the swing member. 
   According to a fourth aspect of the present invention, in the variable valve operating device according to the first aspect of the present invention, the support member may be configured as a link member for linking the control member to the intermediate member, mounted on the control member, and allowed to swing around a position away from the center of the camshaft. 
   According to the fourth aspect of the present invention, the link member couples the intermediate member to the control member. Therefore, the intermediate member can be properly positioned in relation to the control member. 
   According to a fifth aspect of the present invention, in the variable valve operating device according to any one of the first to fourth aspects of the present invention, the rotation interlock mechanism may comprise a first gear, which is installed over the control shaft to rotate together with the control shaft, and a second gear, which is installed over the control member to mesh with the first gear. 
   According to the fifth aspect of the present invention, a gear mechanism, which comprises the first and second gears, is used as the rotation interlock mechanism so that the rotation of the control member is accurately interlocked with the rotation of the control shaft. As a result, the rotation position of the control member can be accurately controlled. 
   According to a sixth aspect of the present invention, in the variable valve operating device according to any one of the first to fifth aspects of the present invention, the rotation interlock mechanism may be a speed reducing mechanism for decelerating the rotation of the control shaft with gears and transmitting the decelerated rotation to the control member. 
   According to the sixth aspect of the present invention, the gear-based speed reducing mechanism is used as the rotation interlock mechanism to inhibit an inverse torque input from the control member to the control shaft. Due to reactive force that the intermediate member receives from the slide surface, the torque for rotation around the camshaft is exerted on the control member. This torque varies in accordance with the rotation of the drive cam. When a torque change is input to the control shaft, the rotation position of the control shaft changes. However, the sixth aspect of the present invention uses the speed reducing mechanism to inhibit an inverse torque input from the control member to the control shaft as mentioned above, thereby avoiding a change in the rotation position of the control shaft. 
   According to a seventh aspect of the present invention, in the variable valve operating device according to any one of the first to sixth aspects of the present invention, the swing cam surface may include a nonoperating surface, which is formed at a fixed distance from the swing center of the swing member, and an operating surface, which is contiguous with the nonoperating surface and whose distance to the swing center gradually increases with an increase in the distance to the nonoperating surface. The valve is lifted when the swing member swings so that the contact position at which the swing cam surface contacts the valve support member moves from the nonoperating surface to the operating surface. 
   According to the seventh aspect of the present invention, the valve lift amount is determined by the position reached on the operating surface of the valve support member, and the valve working angle is determined by the period during which the valve support member is positioned on the operating surface. When the swing angle and initial swing position of the swing member change as mentioned earlier, the position reached on the operating surface of the valve support member changes. This also changes the period during which the valve support member is positioned on the operating surface. Consequently, the seventh aspect of the present invention makes it possible to change the working angle and lift amount in a coordinated manner. 
   According to a eighth aspect of the present invention, in the variable valve operating device according to any one of the first to seventh aspects of the present invention, the intermediate member may include a first roller, which comes into contact with the cam surface of the drive cam; a second roller, which is concentric with the first roller and comes into contact with the slide surface; and a connecting shaft, which connects the first roller to the second roller so as to permit the first and second rollers to rotate independently of each other. 
   According to the eighth aspect of the present invention, the intermediate member includes two rollers, first and second rollers, that can rotate independently of each other. The first roller comes into contact with the surface of the drive cam, and the second roller comes into contact with the slide surface. Therefore, it is possible to reduce the friction loss in the driving force transmission from the camshaft to the valve and prevent the fuel efficiency from deteriorating. Further, the two rollers are installed over the same axis. This makes it possible to render the intermediate member compact and minimize the distance between the cam surface and slide surface of the drive cam. As a result, the variable valve operating device can be rendered compact. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevational view showing the configuration of a variable valve operating device according to the first embodiment of the present invention; 
       FIG. 2  illustrates a great lift operation performed by the variable valve operating device according to the first embodiment of the present invention, in the figure, (A) shows a valve open condition and (B) shows valve closed condition; 
       FIG. 3  illustrates a small lift operation performed by the variable valve operating device according to the first embodiment of the present invention, in the figure, (A) shows a valve open condition and (B) shows valve closed condition; 
       FIG. 4  is a graph showing the relationship between the contact position of the rocker roller onto the swing cam surface and the valve lift amount in the variable valve operating device according to the first embodiment of the present invention; 
       FIG. 5  is a graph showing the relationship between the valve lift amount and valve timing of the valve achieved by the variable valve operating device according to the first embodiment of the present invention; 
       FIG. 6  is a side elevational view showing the configuration of a variable valve operating device according to the second embodiment of the present invention; 
       FIG. 7  illustrates a great lift operation performed by the variable valve operating device according to the second embodiment of the present invention, in the figure, (A) shows a valve open condition and (B) shows valve closed condition; and 
       FIG. 8  illustrates a small lift operation performed by the variable valve operating device according to the second embodiment of the present invention, in the figure, (A) shows a valve open condition and (B) shows valve closed condition. 
   

   BEST MODE FOR CARRYING OUT THE INVENTION 
   First Embodiment 
   A first embodiment of the present invention will now be described with reference to  FIGS. 1 to 5 . 
   [Configuration of a Variable Valve Operating Device According to the First Embodiment] 
     FIG. 1  is a side view illustrating the configuration of a variable valve operating device  100  according to the first embodiment of the present invention. The variable valve operating device  100  includes a rocker arm type mechanical valve mechanism. A drive cam  122 , which is installed over a cam shaft  120 , coverts the rotation motion of the camshaft  120  to the swing motion of a rocker arm (valve support member)  110  and to the vertical lift motion of a valve  104 , which is supported by the rocker arm  110 . The drive cam  122  has two cam surfaces  124   a ,  124   b , which have different profiles. One cam surface, nonoperating surface  124   a , is formed so that the distance from the center of the camshaft  120  is fixed in the rotation direction. The other cam surface, operating surface  124   b , is formed so that the distance from the center of the camshaft  120  gradually increases and then gradually decreases after the apex in the rotation direction. In this document, the term “drive cam surface  124 ” is used when the nonoperating surface  124   a  and operating surface  124   b  are not distinguished from each other. 
   In the variable valve operating device  100 , the drive cam  122  does not directly drive the rocker arm  110 . An adjustment mechanism  130  is positioned between the drive cam  122  and rocker arm  110  to interlock the swing motion of the rocker arm  110  with the rotation motion of the drive cam  122 . The variable valve operating device  100  can continuously change the coordination between the rotation motion of the drive cam  122  and the swing motion of the rocker arm  110  by exercising variable control over the adjustment mechanism  130 . This makes it possible to continuously change the lift amount and valve timing of the valve  104  by changing the swing amount and swing timing of the rocker arm  110 . 
   As described below, the adjustment mechanism  130  mainly comprises a control shaft  132 , a swing cam arm (swing member)  150 , a control arm (control member)  160 , a first roller  170 , a second roller  172 , and a connecting shaft  174 , which connects the first roller  170  to the second roller  172 . The control shaft  132  is parallel to the camshaft  120 . The position of the control shaft  132  relative to the camshaft  120  is set downstream in the rotation direction of the camshaft  120  from the rocker arm  110 . A first gear  134 , which is concentric with the control shaft  132 , is positioned on the outer circumferential surface of the control shaft  132  and fastened to the control shaft  132 . Further, an actuator (e.g., motor), which is not shown, is connected to the control shaft  132 . An ECU for an internal combustion engine can control the actuator to adjust the rotation position of the control shaft  132 . 
   The swing cam arm  150  is supported by the control shaft  132  and allowed to swing. The leading end of the swing cam arm  150  is positioned upstream in the rotation direction of the drive cam  122 . A slide surface  156  is formed on the side opposite the drive cam  122  for the swing cam arm  150 . The slide surface  156  comes into contact with the second roller  172 , which will be described later. The slide surface  156  is curved leniently toward the drive cam  122  and formed so that the distance to the cam base circle (nonoperating surface  124   a ) for the drive cam  122  increases with an increase in the distance from the center of the control shaft  132 , which is the center of swinging. 
   Meanwhile, a swing cam surface  152  ( 152   a ,  152   b ) is formed on the side opposite the slide surface  156  of the swing cam arm  150 . The swing cam surface  152  is a cam surface whose cam center coincides with the swing center of the swing cam arm  150 , and composed of a nonoperating surface  152   a  and an operating surface  152   b , which have different profiles. The nonoperating surface  152   a  is a circumferential surface of the cam base circle and formed at a fixed distance from the center of the control shaft  132 . The other surface, which is the operating surface  152   b , is positioned toward the leading end of the swing cam arm  150  as viewed from the nonoperating surface  152   a , connected smoothly and contiguously to the nonoperating surface  152   a , and formed so that the distance from the center of the control shaft  132  (that is, the cam height) gradually increases with a decrease in the distance to the leading end of the swing cam arm  150 . In this document, the term “swing cam surface  152 ” is used when the nonoperating surface  152   a  and operating surface  152   b  are not distinguished from each other. 
   The variable valve operating device  100  employs a one-cam, two-valve drive structure in which one drive cam  122  drives two valves  104 . Therefore, the swing cam arm  150  is positioned on both sides of the drive cam  122  ( FIG. 1  shows only the front swing cam arm  150 ). The rocker arm  110  is provided for each swing cam arm  150 . The swing cam surface  152  is in contact with a rocker roller  112  for the rocker arm  110 . The rocker roller  112  is mounted on the middle of the rocker arm  110  and allowed to rotate freely. One end of the rocker arm  110  is provided with a valve shaft  102 , which supports the valve  104 . The other end of the rocker arm  110  is supported by a hydraulic lash adjuster  106  and allowed to turn freely. A valve spring (not shown) presses the valve shaft  102  in the closing direction, that is, in the direction of pushing up the rocker arm  110 . The rocker arm  110  is supported by the valve shaft  102 , which is pressed by the valve spring. The hydraulic lash adjuster  106  presses the rocker roller  112  against the swing cam surface  152 . 
   The swing cam arm  150  is provided with a spring seat  158  for engagement with a lost motion spring  190 . The spring seat  158  is positioned behind the nonoperating surface  152   a  and extended in a direction opposite the extension direction of the swing cam arm  150 . The lost motion spring  190  is a compression spring. Its remaining end is secured by a stationary member (not shown). The spring force that the lost motion spring  190  applies to the spring seat  158  presses the swing cam arm  150  to rotate it toward the slide surface  156 . 
   The control arm  160  is supported by the camshaft  120  and allowed to rotate. The control arm  160  is provided with a second gear  162 , which is wedge-shaped and formed around the rotation center of the control arm  160 , that is, along an arc concentric with the camshaft  120 . The position of the control arm  160  on the camshaft  120  is adjusted so that the second gear  162  is in the same plane as the first gear  134 . Further, the rotation phase of the control arm  160  is adjusted so that the second gear  162  faces the first gear  134 . The second gear  162  meshes with the first gear  134 , and the rotation of the control shaft  132  is input to the control arm  160  via the first gear  134  and second gear  162 . In other words, the first gear  134  and second gear  162  constitute an interlock mechanism that interlocks the rotation of the control arm  160  with that of the control shaft  132 . Further, the second gear  162  has a larger diameter than the first gear  134  has. Therefore, the first gear  134  and second gear  162  also constitute a speed reducing mechanism that decelerates the rotation of the control shaft  132  and transmits the decelerated rotation to the control arm  160 . 
   The control arm  160  is provided on both sides of the drive cam  122  ( FIG. 1  shows only the front control arm  160 ). As is the case with the control arm  160 , the first gear  134  is provided on the outside of both the right- and left-hand swing cam arms  150 , and engaged with the second gear  162  of the associated control arm  160 . 
   The control arm  160  is provided with a guide  166 , which is integral with the control arm  160 . This guide  166  is extended outward from the center of the camshaft  120 , that is, extended substantially in the radial direction of the camshaft  120 . The approximate rotation position of the control arm  160  is adjusted in relation to the camshaft  120  so that the guide  166  is substantially perpendicular to the slide surface  156  of the swing cam arm  150 . As mentioned earlier, the control arm  160  is provided on both sides of the drive cam  122 . The guide  166  is formed for each of the right- and left-hand control arms  160 . The connecting shaft  174  is passed through the right- and left-hand guides  166 . The connecting shaft  174  can move along the guides  166 . The connecting shaft  174  supports one first roller  170  and two second rollers  172  in such a manner that the rollers can freely rotate. The two second rollers  172  are positioned on both sides of the first roller  170  ( FIG. 1  shows only the front second roller  172 ). The first and second rollers  170 ,  172  are positioned between the drive cam surface  124  and slide surface  156 . The first roller  170  is in contact with the drive cam surface  124 . The second rollers  172  are in contact with the slide surface  156  of each swing cam arm  150 . Due to the force that the swing cam arm  150  receives from the lost motion spring  190 , the slide surface  156  pushes up the second rollers  172 . The first roller  170 , which is concentric and integral with the second rollers  172 , is pressed against the drive cam surface  124 . 
   [Operations Performed by the Variable Valve Operating Device According to the First Embodiment] 
   The operations performed by the variable valve operating device  100  will now be described with reference to  FIGS. 2 to 4 . To clarify the motions of the rollers  170 ,  172 ,  FIGS. 2 and 3  exclude the front control arm  160  and first gear  134 . 
   (1) Valve Lift Operation Performed by the Variable Valve Operating Device 
   First of all, the lift operation performed by the variable valve operating device  100  will be described with reference to  FIG. 2 .  FIG. 2(A)  shows the status of the variable valve operating device  100  that prevails when the valve  104  is closed in a valve lift operation sequence.  FIG. 2(B)  shows the status of the variable valve operating device  100  that prevails when the valve  104  is open in the valve lift operation sequence. 
   In the variable valve operating device  100 , the rotation motion of the drive cam  122  is first input to the first roller  170 , which comes into contact with the drive cam surface  124 . The first roller  170  and the second rollers  172 , which are concentric and integral with the first roller  170 , reciprocate along the guide  166 . In this instance, the control arm  160  can freely rotate with respect to the camshaft  120 , and the control shaft  132  inhibits the rotation of the control arm  160  via the first gear  134  (see  FIG. 1 ) and second gear  162 . Therefore, the control arm  160  remains stationary in a fixed posture without regard to the rotation of the drive cam  122 . The reciprocating motions of the rollers  170 ,  172  along the guide  166  are input to the slide surface  156  of the swing cam arm  150 , which supports the second rollers  172 . Since the force of the lost motion spring (not shown) constantly presses the slide surface  156  against the second rollers  172 , the swing cam arm  150  swings around the control shaft  132  in accordance with the rotation of the drive cam  122 . 
   More specifically, when the camshaft  120  rotates in the state shown in  FIG. 2(A) , the contact position P 1  at which the first roller  170  contacts the drive cam surface  124  changes from the nonoperating surface  124   a  to the operating surface  124   b  as indicated in  FIG. 2(B) . Relatively, the first roller  170  is pushed downward by the drive cam  122 . Then, the first roller  170  moves together with the second rollers  172 , which are concentric and integral with the first roller  170 , along the locus defined by the guide  166 . The second rollers  172  then push down the slide surface  156  of the swing cam arm  150 . Consequently, the swing cam arm  150  turns clockwise around the control shaft  132  as indicated in  FIG. 2 . When the camshaft  120  further rotates until the contact position P 1  at which the first roller  170  contacts the drive cam surface  124  passes the apex of the operating surface  124   b , the force generated by the lost motion spring and valve spring causes the swing cam arm  150  to turn counterclockwise around the control shaft  132  as indicated in  FIG. 2 . 
   When the swing cam arm  150  turns around the control shaft  132  as described above, the contact position P 3  at which the rocker roller  112  contacts the swing cam surface  152  changes. In  FIG. 2 , the contact positions at which the rocker roller  112  contacts the swing cam surface  152  are designated P 3   i  and P 3   f . This is to distinguish between an initial contact position P 3   i  and a final contact position P 3   f , which will be described later. In this document, the term “contact position P 3 ” is simply used to represent the contact position at which the rocker roller  112  contacts the swing cam surface  152 . 
   When the rocker roller  112  is in contact with the nonoperating surface  152   a  as indicated in  FIG. 2(A) , the distance between the nonoperating surface  152   a  and the center of the control shaft  132  is fixed. Therefore, the position of the rocker roller  112  within the space remains unchanged without regard to the contact position. Consequently, the rocker arm  110  does not swing so that the valve  104  is maintained at a fixed position. The positional relationship among the components of the variable valve operating device  100  is adjusted so as to close the valve  104  when the rocker roller  112  is in contact with the nonoperating surface  152   a.    
   When the contact position P 3  at which the rocker roller  112  contacts the swing cam surface  152  changes from the nonoperating surface  152   a  to the operating surface  152   b  as indicated in  FIG. 2(B) , the rocker arm  110  is pushed downward in accordance with the distance between the operating surface  152   b  and the center of the control shaft  132 . This causes the rocker arm  110  to swing clockwise around a point that is supported by the hydraulic lash adjuster  106 . The valve  104  is then pushed downward and opened by the rocker arm  110 . 
   (2) Valve Lift Amount Change Operation Performed by the Variable Valve Operating Device 
   The valve lift amount change operation performed by the variable valve operating device  100  will now be described with reference to  FIGS. 2 to 5 .  FIG. 3  illustrates an operation in which the variable valve operating device  100  gives a small lift to the valve  104 . Meanwhile,  FIG. 2  illustrates an operation in which the variable valve operating device  100  gives a great lift to the valve  104 .  FIGS. 2(A) and 3(A)  show the status of the variable valve operating device  100  that prevails when the valve  104  is closed in a lift operation sequence.  FIGS. 2(B) and 3(B)  show the status of the variable valve operating device  100  that prevails when the valve  104  is open in the valve lift operation sequence. 
   When the valve lift amount is to be changed from the valve lift amount shown in  FIG. 2(B)  to the valve lift amount shown in  FIG. 3(B) , the control shaft  132 , which is in the state shown in  FIG. 2(A) , is rotated in the same direction as that of the rotation of the camshaft  120  (rotated clockwise as viewed in the figures), and the control arm  160  is rotated to the rotation position shown in  FIG. 3(A) . The rotation amount of the control arm  160  is determined by the rotation amount of the control shaft  132  and the gear ratio between the first gear  134  (see  FIG. 1 ) and second gear  162 . Both rollers  170 ,  172  are connected to the control arm  160  by means of a control link  164 . Therefore, when the control arm  160  rotates, the first roller  170  moves in a direction opposite the rotation direction of the camshaft  120  along the drive cam surface  124 , whereas the second rollers  172  move away from the control shaft  132  along the slide surface  156 . 
   When the second rollers  172  move away from the control shaft  132 , the distance between the swing center CO of the swing cam arm  150  and the contact position P 2  at which the second rollers  172  contact the slide surface  156  increases, thereby decreasing the swing angle of the swing cam arm  150 . The reason is that the swing angle of the swing cam arm  150  is in inverse proportion to the distance between the swing center CO and the contact position P 2 , which is an oscillation input point. As indicated in  FIGS. 2(B) and 3(B) , the lift of the valve  104  is maximized when the contact position P 1  at which the first roller  170  contacts the drive cam surface  124  is at the apex of the operating surface  124   b , and the valve lift amount of the valve  104  is determined by the contact position P 3   f  at which the rocker roller  112  contacts the swing cam surface  152  when the valve lift is maximized (hereinafter referred to as the final contact position).  FIG. 4  illustrates the relationship between the valve lift and the position of the rocker roller  112  on the swing cam surface  152 . As indicated in  FIG. 4 , the final contact position P 3   f  is determined by the aforementioned swing angle of the swing cam arm  150  and the contact position P 3   i  at which the rocker roller  112  contacts the swing cam surface  152  as indicated in  FIGS. 2(A) and 3(A)  (hereinafter referred to as the initial contact position). 
   In the variable valve operating device  100  according to the present embodiment, the slide surface  156  is formed so that the distance to the cam base circle (nonoperating surface  124   a ) of the drive cam  122  increases with an increase in the distance to the swing center. Therefore, when the aforementioned contact position P 2  moves away from the swing center CO of the swing cam arm  150 , the swing cam arm  150  inclines in such a direction that the slide surface  156  approaches the drive cam surface  124 . The swing cam arm  150  then turns counterclockwise around the control shaft  132  as viewed in the figures. This causes the initial contact position P 3   i  of the rocker roller  112  on the swing cam surface  152  to move away from the operating surface  152   b  as indicated in  FIG. 3(A) . 
   When the control shaft  132  rotates in the same direction as that of the camshaft  120 , the swing angle of the swing cam arm  150  decreases and the initial contact position P 3   i  moves away from the operating surface  152   b . Consequently, the final contact position P 3   f  that the rocker roller  112  can reach moves toward the nonoperating surface  152   a  as indicated in  FIG. 4 , thereby decreasing the lift amount of the valve  104 . The working angle of the valve  104  corresponds to a period (crank angle) during which the rocker roller  112  is positioned on the operating surface  152   a . However, when the final contact position P 3   f  moves toward the nonoperating surface  152   a , the working angle of the valve  104  also decreases. Further, the first roller  170  moves in a direction opposite the rotation direction of the camshaft  120 . Therefore, the contact position P 1  at which the first roller  170  contacts the drive cam surface  124  when the camshaft  120  is at the same rotation position moves toward the advance side of the drive cam  122 . This advances the swing timing of the swing cam arm  150  in relation to the phase of the camshaft  120 . As a result, the valve timing (maximum lift timing) advances. 
     FIG. 5  is a graph illustrating the relationship between the lift amount and valve timing of the valve  104 , which are provided by the variable valve operating device  100 . As shown in this figure, the variable valve operating device  100  increases the working angle and retards the valve timing when the lift amount of the valve  104  increases. Conversely, the variable valve operating device  100  decreases the working angle and advances the valve timing when the lift amount of the valve  104  decreases. Therefore, if the valve  104  is an intake valve, it is possible to vary the operating characteristic without using a VVT or other valve timing control mechanism so that the opening timing of the valve  104  remains virtually fixed. 
   [Advantages of the Variable Valve Operating Device According to the First Embodiment] 
   As described above, the variable valve operating device  100  according to the present embodiment rotates the control shaft  132  to change the rotation position of the first gear  134 , thereby changing the contact position P 2  at which the second rollers  164  contact the slide surface and the contact position P 1  at which the first roller  162  contacts the drive cam surface  124 . As a result, the variable valve operating device  100  according to the present embodiment can change the lift amount, working angle, and valve timing of the valve  104  in a coordinated manner. 
   Further, the control arm  160  is installed over the existing camshaft  120 , and the control arm  160  supports the rollers  170 ,  172 . Therefore, in marked contrast to a conventional structure in which the rollers are supported by the arm installed over the control shaft, the entire apparatus can be rendered compact. Furthermore, the influence upon the other members and apparatuses mounted inside the cylinder head can be minimized. In addition, since the rollers  170 ,  172  are concentrically positioned, the distance between the drive cam surface  124  and slide surface  156  is reduced. This also makes the entire apparatus compact. 
   Within the adjustment mechanism  130 , which changes the aforementioned operating characteristic, only the intermediate members, such as the rollers  170 ,  172  and connecting member  174 , and the swing cam arm  150  move to lift the valve  104 . Therefore, when compared to a conventional valve apparatus that does not have the adjustment mechanism  130 , the increase in the inertial mass of the entire movable section is suppressed. Therefore, the variable valve operating device  100  according to the present embodiment does not obstruct an increase in the internal combustion engine speed and suppresses the decrease in fuel efficiency. 
   Further, the guide  166  that supports the rollers  170 ,  172  is formed outward from the center of the camshaft  120 . Therefore, the rollers  170 ,  172  reciprocate substantially in the radial direction of the camshaft  120  in accordance with the rotation of the drive cam  122 . Unnecessary motions of the rollers  170 ,  172  on the slide surface  156  are then suppressed so as to minimize the loss in the driving force transmission from the drive cam  122  to the swing cam arm  150 . This also suppresses the decrease in internal combustion engine fuel efficiency. 
   When the drive cam  122  rotates to lift the valve  104 , the reactive force of the lost motion spring  190  and valve spring, not shown, is input from the slide surface  156  to the rollers  170 ,  172  so that the torque around the camshaft  120  works on the control arm  160 , which supports the rollers  170 ,  172 . Since the above-mentioned reactive force varies with the swing of the swing cam arm  150 , the torque working on the control arm  160  also varies. When such torque variation is conversely input from the control arm  160  to the control shaft  132 , the rotation position of the control shaft  132  changes unexpectedly. When the rotation position of the control shaft  132  changes unexpectedly, the contact positions P 1 , P 2  at which the rollers  170 ,  172  contact the drive cam surface  124  or slide surface  156  also change unexpectedly. Consequently, a desired operating characteristic cannot be obtained. 
   In regard to the above matter, the gears  134 ,  162  in the variable valve operating device  100  according to the present embodiment, which interlocks the rotation of the control shaft  132  with that of the control arm  160 , constitute a speed reducing mechanism. It is therefore possible to inhibit an inverse torque variation input from the control arm  160  to the control shaft  132  and avoid an unexpected change in the rotation position of the control shaft. It means that control can be exercised to vary the operating characteristic of the valve  104  with high accuracy. 
   Second Embodiment 
   A second embodiment of the present invention will now be described with reference to  FIGS. 6 to 8 . 
   [Configuration of a Variable Valve Operating Device According to the Second Embodiment] 
     FIG. 6  is a side view illustrating the configuration of a variable valve operating device  200  according to the second embodiment of the present invention. The variable valve operating device  200  includes a rocker arm type mechanical valve mechanism. A drive cam  222 , which is installed over a cam shaft  220 , coverts the rotation motion of a camshaft  220  to the swing motion of a rocker arm (valve support member)  210  and to the vertical lift motion of a valve  204 , which is supported by the rocker arm  210 . The drive cam  222  has two cam surfaces  224   a ,  224   b , which have different profiles. One cam surface, nonoperating surface  224   a , is formed so that the distance from the center of the camshaft  220  is fixed in the rotation direction. The other cam surface, operating surface  224   b , is formed so that the distance from the center of the camshaft  220  gradually increases and then gradually decreases after the apex in the rotation direction. In this document, the term “drive cam surface  224 ” is used when the nonoperating surface  224   a  and operating surface  224   b  are not distinguished from each other. 
   As is the case with the variable valve operating device according to the first embodiment, the variable valve operating device  200  according to the second embodiment includes an adjustment mechanism  230 , which is positioned between the drive cam  222  and rocker arm  210  to interlock the swing motion of the rocker arm  210  with the rotation motion of the drive cam  222 . As described below, the adjustment mechanism  230  mainly comprises a control shaft  232 , a swing cam arm (swing member)  250 , a control arm (control member)  260 , a control link (link member)  264 , a first roller  270 , a second roller  272 , and a connecting shaft  274 , which connects the first roller  270  to the second roller  272 . The control shaft  232  is parallel to the camshaft  220 . The position of the control shaft  232  relative to the camshaft  220  is set downstream in the rotation direction of the camshaft  220  from the rocker arm  210 . A first gear  234 , which is concentric with the control shaft  232 , is positioned on the outer circumferential surface of the control shaft  232  and fastened to the control shaft  232 . Further, an actuator (e.g., motor), which is not shown, is connected to the control shaft  232 . An ECU for an internal combustion engine can control the actuator to adjust the rotation position of the control shaft  232 . 
   The swing cam arm  250  is supported by the control shaft  232  and allowed to swing. The leading end of the swing cam arm  250  is positioned upstream in the rotation direction of the drive cam  222 . A slide surface  256  is formed on the side opposite the drive cam  222  for the swing cam arm  250 . The slide surface  256  comes into contact with the second roller  272 , which will be described later. The slide surface  256  is curved leniently toward the drive cam  222  and formed so that the distance to the cam base circle (nonoperating surface  224   a ) for the drive cam  222  increases with an increase in the distance from the center of the control shaft  232 , which is the center of swinging. 
   Meanwhile, a swing cam surface  252  ( 252   a ,  252   b ) is formed on the side opposite the slide surface  256  of the swing cam arm  250 . The swing cam surface  252  is a cam surface whose cam center coincides with the swing center of the swing cam arm  250 , and composed of a nonoperating surface  252   a  and an operating surface  252   b , which have different profiles. The nonoperating surface  252   a  is a circumferential surface of the cam base circle and formed at a fixed distance from the center of the control shaft  232 . The other surface, which is the operating surface  252   b , is positioned toward the leading end of the swing cam arm  250  as viewed from the nonoperating surface  252   a , connected smoothly and contiguously to the nonoperating surface  252   a , and formed so that the distance from the center of the control shaft  232  (that is, the cam height) gradually increases with a decrease in the distance to the leading end of the swing cam arm  250 . In this document, the term “swing cam surface  252 ” is used when the nonoperating surface  252   a  and operating surface  252   b  are not distinguished from each other. 
   The variable valve operating device  200  employs a one-cam, two-valve drive structure in which one drive cam  222  drives two valves  204 . Therefore, the swing cam arm  250  is positioned on both sides of the drive cam  222  ( FIG. 6  shows only the front swing cam arm  250 ). The rocker arm  210  is provided for each swing cam arm  250 . The swing cam surface  252  of the swing cam arm  250  is in contact with a rocker roller  212  for the rocker arm  210 . The rocker roller  212  is mounted on the middle of the rocker arm  210  and allowed to rotate freely. One end of the rocker arm  210  is provided with a valve shaft  202 , which supports the valve  204 . The other end of the rocker arm  210  is supported by a hydraulic lash adjuster  206  and allowed to turn freely. A valve spring (not shown) presses the valve shaft  202  in the closing direction, that is, in the direction of pushing up the rocker arm  210 . The rocker arm  210  is supported by the valve shaft  202 , which is pressed by the valve spring. The hydraulic lash adjuster  206  presses the rocker roller  212  against the swing cam surface  252 . 
   The swing cam arm  250  is provided with a spring seat  258  for engagement with a lost motion spring (not shown). The spring seat  258  is formed on the side opposite the operating surface  256   b  with respect to the nonoperating surface  252   a . The lost motion spring is a compression spring. Its remaining end is secured by a stationary member (not shown). The spring force that the lost motion spring applies to the spring seat  258  presses the swing cam arm  250  to rotate it toward the slide surface  256 . 
   The control arm  260  is supported by the camshaft  220  and allowed to rotate. The control arm  260  is provided with a second gear  262 , which is wedge-shaped and formed around the rotation center of the control arm  260 , that is, along an arc concentric with the camshaft  220 . The position of the control arm  260  on the camshaft  220  is adjusted so that the second gear  262  is in the same plane as the first gear  234 . Further, the rotation phase of the control arm  260  is adjusted so that the second gear  262  faces the first gear  234 . The second gear  262  meshes with the first gear  234 , and the rotation of the control shaft  232  is input to the control arm  260  via the first gear  234  and second gear  262 . In other words, the first gear  234  and second gear  262  constitute a rotation interlock mechanism that interlocks the rotation of the control arm  260  with that of the control shaft  232 . Further, the second gear  262  has a larger diameter than the first gear  234 . Therefore, the first gear  234  and second gear  262  also constitute a speed reducing mechanism that decelerates the rotation of the control shaft  232  and transmits the decelerated rotation to the control arm  260 . 
   The control arm  260  is provided with the control link  264 . The control link  264  is mounted at a position away from the center of the camshaft  220 , around which the control arm  260  turns, and is allowed to rotate freely. The end of the fulcrum side of the control link  264  is provided with a connection pin  266 . The connection pin  266  is supported by the control arm  260  and allowed to rotate freely. The position of the connection pin  266  on the control arm  260  is virtually opposite the second gear  262  with respect to the turning center of the control arm  260 . The leading end of the control link  264  is oriented toward the control shaft  232  while the connection pin  266  serves as a fulcrum. Each side of the drive cam  222  is provided with the control arm  260 . The control link  264  is supported by the right- and left-hand control arms  160  ( FIG. 6  excludes the front control arm  260 ). 
   The control link  264  has a pair of arms  268  (right- and left-hand arms). The right- and left-hand arms  268  support a connecting shaft  274  ( FIG. 6  shows only the front arm  268 ). The connecting shaft  274  supports one first roller  270  and two second rollers  272 , which are positioned on both sides of the first roller  270 . The first and second rollers are allowed to rotate freely ( FIG. 6  shows only the front second roller  272 ). The leading end of the control link  264  is oriented toward the control shaft  232  and in a direction opposite the extension direction of the swing cam arm  250 . Both rollers  270 ,  272  are positioned between the drive cam surface  224  and slide surface  256 . The first roller  270  is in contact with the drive cam surface  224 . The second rollers  272  are in contact with the slide surface  256  of each swing cam arm  250 . The force that the swing cam arm  250  receives from the lost motion spring causes the slide surface  256  to push up the second rollers  272 . The first roller  270 , which is concentric and integral with the second rollers  272 , is pressed against the drive cam surface  224 . 
   [Operations Performed by the Variable Valve Operating Device According to the Second Embodiment] 
   The operations performed by the variable valve operating device  200  will now be described with reference to  FIGS. 7 and 8 . 
   (1) Valve Lift Operation Performed by the Variable Valve Operating Device 
   First of all, the lift operation performed by the variable valve operating device  200  will be described with reference to  FIG. 7 .  FIG. 7(A)  shows the status of the variable valve operating device  200  that prevails when the valve  204  is closed in a valve lift operation sequence.  FIG. 7(B)  shows the status of the variable valve operating device  200  that prevails when the valve  204  is open in the valve lift operation sequence. 
   In the variable valve operating device  200 , the rotation motion of the drive cam  222  is first input to the first roller  270 , which comes into contact with the drive cam surface  224 . The first roller  270  and the second rollers  272 , which are concentric and integral with the first roller  270 , swing around the pin  266 . This swing motion is input to the slide surface  256  of the swing cam arm  250 , which supports the second rollers  272 . Since the force of the lost motion spring (not shown) constantly presses the slide surface  256  against the second rollers  272 , the swing cam arm  250  swings around the control shaft  232  in accordance with the rotation of the drive cam  222 . 
   More specifically, when the camshaft  220  rotates in the state shown in  FIG. 7(A) , the contact position P 1  at which the first roller  270  contacts the drive cam surface  224  changes from the nonoperating surface  224   a  to the operating surface  224   b  as indicated in  FIG. 7(B) . Relatively, the first roller  270  is pushed downward by the drive cam  222 . Then, the first roller  270  moves together with the second rollers  272 , which are concentric and integral with the first roller  270 , along the locus defined by the control link  264 . The second rollers  272  then push down the slide surface  256  of the swing cam arm  250 . Consequently, the swing cam arm  250  turns clockwise around the control shaft  232  as indicated in  FIG. 7 . When the camshaft  220  further rotates until the contact position P 1  at which the first roller  270  contacts the drive cam surface  224  passes the apex of the operating surface  224   b , the force generated by the lost motion spring and valve spring causes the swing cam arm  250  to turn counterclockwise around the control shaft  232  as indicated in  FIG. 7 . 
   When the swing cam arm  250  turns around the control shaft  232  as described above, the contact position P 3  at which the rocker roller  212  contacts the swing cam surface  252  changes. In  FIG. 7 , the contact positions at which the rocker roller  212  contacts the swing cam surface  252  are designated P 3   i  and P 3   f . This is to distinguish between an initial contact position P 3   i  and a final contact position P 3   f , which will be described later. In this document, the term “contact position P 3 ” is simply used to represent the contact position at which the rocker roller  212  contacts the swing cam surface  252 . 
   When the rocker roller  212  is in contact with the nonoperating surface  252   a  as indicated in  FIG. 7(A) , the distance between the nonoperating surface  252   a  and the center of the control shaft  232  is fixed. Therefore, the position of the rocker roller  212  within the space remains unchanged without regard to the contact position. Consequently, the rocker arm  210  does not swing so that the valve  204  is maintained at a fixed position. The positional relationship among the components of the variable valve operating device  200  is adjusted so as to close the valve  204  when the rocker roller  212  is in contact with the nonoperating surface  252   a.    
   When the contact position P 3  at which the rocker roller  212  contacts the swing cam surface  252  changes from the nonoperating surface  252   a  to the operating surface  252   b  as indicated in  FIG. 7(B) , the rocker arm  210  is pushed downward in accordance with the distance between the operating surface  252   b  and the center of the control shaft  232 . This causes the rocker arm  210  to swing clockwise around a point that is supported by the hydraulic lash adjuster  106 . The valve  204  is then pushed downward and opened by the rocker arm  210 . 
   (2) Valve Lift Amount Change Operation Performed by the Variable Valve Operating Device 
   The valve lift amount change operation performed by the variable valve operating device  200  will now be described with reference to  FIGS. 7 and 8 .  FIG. 8  illustrates an operation in which the variable valve operating device  200  gives a small lift to the valve  204 . Meanwhile,  FIG. 7  illustrates an operation in which the variable valve operating device  200  gives a great lift to the valve  204 .  FIGS. 7(A) and 8(A)  show the status of the variable valve operating device  200  that prevails when the valve  204  is closed in a valve lift operation sequence.  FIGS. 7(B) and 8(B)  show the status of the variable valve operating device  200  that prevails when the valve  204  is open in the valve lift operation sequence. 
   When the valve lift amount is to be changed from the valve lift amount shown in  FIG. 7(B)  to the valve lift amount shown in  FIG. 8(B) , the control shaft  232 , which is in the state shown in  FIG. 7(A) , is rotated in the same direction as that of the rotation of the camshaft  220  (rotated clockwise as viewed in the figures), and the control arm  260  is rotated to the rotation position shown in  FIG. 8(A) . The rotation amount of the control arm  260  is determined by the rotation amount of the control shaft  232  and the gear ratio between the first gear  234  (see  FIG. 1 ) and second gear  262 . Both rollers  270 ,  272  are connected to the control arm  260  by means of the control link  264 . Therefore, when the control arm  260  rotates, the first roller  270  moves in a direction opposite the rotation direction of the camshaft  220  along the drive cam surface  224 , whereas the second rollers  272  move away from the control shaft  232  along the slide surface  256 . 
   When the second rollers  272  move away from the control shaft  232 , the distance between the swing center CO of the swing cam arm  250  and the contact position P 2  at which the second rollers  272  contact the slide surface  256  increases, thereby decreasing the swing angle of the swing cam arm  250 . The reason is that the swing angle of the swing cam arm  250  is in inverse proportion to the distance between the swing center CO and the contact position P 2 , which is an oscillation input point. As indicated in  FIGS. 7(B) and 8(B) , the lift of the valve  204  is maximized when the contact position P 1  at which the first roller  270  contacts the drive cam surface  224  is at the apex of the operating surface  224   b , and the lift amount of the valve  204  is determined by the contact position P 3   f  at which the rocker roller  212  contacts the swing cam surface  252  when the valve lift is maximized (hereinafter referred to as the final contact position). As is the case with the first embodiment (see  FIG. 4 ), the final contact position P 3   f  is determined by the aforementioned swing angle of the swing cam arm  250  and the contact position P 3   i  at which the rocker roller  212  contacts the swing cam surface  252  as indicated in  FIGS. 7(A) and 8(A)  (hereinafter referred to as the initial contact position). 
   In the variable valve operating device  200  according to the present embodiment, the slide surface  256  is formed so that the distance to the cam base circle (nonoperating surface  224   a ) of the drive cam  222  increases with an increase in the distance to the swing center. Therefore, when the aforementioned contact position P 2  moves away from the swing center CO of the swing cam arm  250 , the swing cam arm  250  inclines in such a direction that the slide surface  256  approaches the drive cam surface  224 . The swing cam arm  250  then turns counterclockwise around the control shaft  232  as viewed in the figures. This causes the initial contact position P 3   i  of the rocker roller  212  on the swing cam surface  252  to move away from the operating surface  252   b  as indicated in  FIG. 8(A) . 
   When the control shaft  232  rotates in the same direction as that of the camshaft  220 , the swing angle of the swing cam arm  250  decreases and the initial contact position P 3   i  moves away from the operating surface  252   b . Consequently, the final contact position P 3   f  that the rocker roller  212  can reach moves toward the nonoperating surface  252   a , thereby decreasing the lift amount of the valve  204 . The working angle of the valve  204  corresponds to a period (crank angle) during which the rocker roller  212  is positioned on the operating surface  252   a . However, when the final contact position P 3   f  moves toward the nonoperating surface  252   a , the working angle of the valve  204  also decreases. Further, the first roller  270  moves in a direction opposite the rotation direction of the camshaft  220 . Therefore, the contact position P 1  at which the first roller  270  contacts the drive cam surface  224  when the camshaft  220  is at the same rotation position moves toward the advance side of the drive cam  222 . This advances the swing timing of the swing cam arm  250  in relation to the phase of the camshaft  220 . As a result, the valve timing (maximum lift timing) advances. 
   [Advantages of the Variable Valve Operating Device According to the Second Embodiment] 
   As described above, the variable valve operating device  200  according to the present embodiment changes the rotation position of the control shaft  232  to change the contact position P 2  at which the second rollers  272  contact the slide surface  256  and the contact position P 1  at which the first roller  270  contacts the drive cam surface  224 , thereby changing the lift amount, working angle, and valve timing of the valve  204  in a coordinated manner. As is the case with the variable valve operating device  100  according to the first embodiment, the variable valve operating device  200  according to the present embodiment also provides a valve timing-lift characteristic shown in  FIG. 5 . 
   In the variable valve operating device  200  according to the present embodiment, the control arm  260  is installed over the existing camshaft  220  as is the case with the variable valve operating device according to the first embodiment. The control link  264  mounted on the control arm  260  supports the rollers  270 ,  272 . Therefore, the entire apparatus can be rendered compact. Further, the influence upon the other members and apparatuses mounted inside the cylinder head can be minimized. Furthermore, since the rollers  270 ,  272  are concentrically positioned, the distance between the drive cam surface  224  and slide surface  256  is reduced as is the case with the first embodiment. 
   In the variable valve operating device  200  according to the present embodiment, the rollers  270 ,  272  are supported by the control link  264 . However, when compared to a conventional structure that supports the rollers with an arm installed over the control shaft, the control link  264  for supporting the rollers  270 ,  272  near the camshaft  220  is shorter. Therefore, the variable valve operating device  200  according to the present embodiment can also avoid an increase in the inertial mass of the entire movable section when compared to the conventional structure. 
   In the variable valve operating device  200  according to the present embodiment, the gears  234 ,  264  for interlocking the rotation of the control shaft  232  with that of the control arm  260  constitute a speed reducing mechanism as is the case with the variable valve operating device according to the first embodiment. It is therefore possible to inhibit an inverse torque variation input from the control arm  260  to the control shaft  232  and avoid an unexpected change in the rotation position of the control shaft. 
   OTHER 
   While the present invention has been described in terms of preferred embodiments, it should be understood that the invention is not limited to the preferred embodiments, and that variations may be made without departure from the scope and spirit of the invention. For example, the following modifications may be made to the preferred embodiments of the present invention. 
   In the embodiments described above, the first gear  134 ,  234 , which is fastened to the control shaft  132 ,  232  meshes with the second gear  162 ,  262 , which is provided for the control arm  160 ,  260 , to constitute the “rotation interlock mechanism” according to the first aspect of the present invention. However, one or a plurality of intermediate gears may alternatively be positioned between the first gear  134 ,  234  and second gear  162 ,  262 . Another alternative is to use a worm gear as a gear mechanism. Still another alternative is to use a chain mechanism or belt mechanism as an interlock mechanism in addition to the gear mechanism. 
   In the embodiments described above, the present invention is applied to a rocker arm type valve apparatus. However, the present invention can also be applied to a direct acting or other valve apparatus.