Patent Publication Number: US-6655332-B2

Title: Valve timing adjusting apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based upon, claims the benefit of priority of, and incorporates by reference the contents of prior Japanese Patent Application No. 2002-81540 filed on Mar. 22, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a valve timing adjusting apparatus of an internal combustion engine (hereinafter, referred to simply as the engine) for adjusting an opening and closing timing (hereinafter, referred to as the valve timing) of at least one of an exhaust valve and an intake valve of the engine. 
     2. Description of the Related Art 
     Conventionally, a valve timing adjusting apparatus for adjusting valve timing of valves is known. Such an apparatus is provided to a transmission system that transmits driving torque of a crankshaft to a camshaft, where the crankshaft serves as an engine driving shaft and the camshaft serves as a driven shaft that opens and closes the exhaust valve or the intake valve of the engine. The valve timing adjusting apparatus adjusts the valve timing by changing a relative rotational phase (hereinafter, referred to simply as the phase) of the camshaft with respect to the crankshaft, thereby enhancing engine output and improving fuel consumption. 
     An apparatus that changes the phase of the camshaft through the use of oil pressure is one type of valve timing adjusting apparatus. In the case of using oil pressure, however, it is difficult to control a phase change of the camshaft with accuracy when the oil-pressure control conditions are strict, for example, during an operation under low-temperature circumstances, in a period immediately after engine start-up, etc. 
     In order to eliminate such an inconvenience, Japanese Patent Laid-Open Publication No. Hei. 10-153104 discloses a valve timing adjusting apparatus that changes the phase of the camshaft by making use of an electromagnetic force of an electromagnetic solenoid instead of using oil pressure. This apparatus, however, changes a phase by converting an electromagnetic-induced displacement of a piston member in the axial direction into rotational motions of the camshaft through a helical mechanism. Hence, when a larger width is given to a phase change, a large displacement in the axial direction is experienced by the piston member. This undesirably increases the size of the apparatus. Further, although this apparatus uses an electromagnetic force of the electromagnetic solenoid during an advancing operation that causes a phase change of the camshaft to an advancing side, it uses a biasing force of a biasing member by switching OFF the electromagnetic solenoid during a retarding operation that causes a phase change of the camshaft to a retarding side. This gives rise to a noticeable change in elastic modulus of the biasing member under low-temperature circumstances or the like, and the accuracy of the phase-change control is reduced. Also, because the phase change during the retarding operation depends on a biasing force of the biasing member, there is a limit to improving a response of the phase change. Moreover, energy is lost during the advancing operation for extra work needed to wind a helical spring used as the biasing member. 
     SUMMARY OF THE INVENTION 
     The invention therefore has an object to provide a valve timing adjusting apparatus of a compact size, capable of ensuring a width of a phase change of the driven shaft with respect to the driving shaft. 
     The invention has another object to provide a valve timing adjusting apparatus having an excellent phase change response of the driven shaft with respect to the driving shaft. 
     The invention has yet another object to provide a valve timing adjusting apparatus capable of constantly and accurately controlling a phase change of the driven shaft with respect to the driving shaft. 
     According to a valve timing adjusting apparatus of a first aspect of the invention, a first brake portion transmits a first torque to a first eccentric shaft that is off-center from a driven axis. The first eccentric shaft rotates around the driven axis in a direction opposite to the rotational direction of the driven axis. The first eccentric shaft then starts to rotate in a retarding direction relative with respect to a rotating member. Accordingly, a first planetary gear, which is supported on an outside wall of the first eccentric shaft to enable a relative rotation and rotates around the driven axis through engagement with a first internal gear of the rotating member, starts to rotate in an advancing direction together with a first output shaft and the driven shaft engaged therewith relative to the rotating member while rotating in the advancing direction relative to the first eccentric shaft. It is thus possible to change, while the first torque is transmitted, the phase of the driven shaft with respect to the rotating member, that is, the phase of the driven shaft with respect to the driving shaft that rotates the rotating member with driving torque, to an advancing side. 
     Also, according to the valve timing adjusting apparatus of the first aspect of the invention, a second brake portion transmits a second torque to a second eccentric shaft off-center from the driven axis and rotating around the driving axis, in a direction opposite to the rotational direction thereof. The second eccentric shaft then starts to rotate in the retarding direction relative to the rotating member. Accordingly, a second planetary gear, which is supported on an outside wall of the second eccentric shaft to enable relative rotation and rotation around the driven axis through engagement with a second internal gear of the rotating member, starts to rotate in the advancing direction. The second planetary gear rotates together with a second output shaft and the first eccentric shaft engaged therewith relative to the rotating member while maintaining rotation in the advancing direction relative to the second eccentric shaft. The first planetary gear thus starts to rotate in the retarding direction together with the first output shaft and the driven shaft relative to the rotating member while maintaining rotation in the retarding direction relative to the first eccentric shaft. It is thus possible to change, while the second torque is transmitted, the phase of the driven shaft with respect to the rotating member, that is, the phase of the driven shaft with respect to the driving shaft, to a retarding side. 
     As has been described, according to the valve timing adjusting apparatus of the first aspect of the invention, a displacement of each of the first and second eccentric shafts, the first and second planetary gears, and the first and second output shafts needed for a phase change of the driven shaft with respect to the driving shaft is obtained from a relative rotation around the driven axis with respect to the rotating member. For this reason, a larger quantity can be secured around the driven axis for the displacement of the foregoing components needed for a phase change of the driven shaft. It is thus possible to reduce the apparatus in size while ensuring a width of a phase change of the driven shaft. 
     According to a valve timing adjusting apparatus of a second aspect of the invention, one of the rotating member and the first output shaft is provided with a stopper slot that extends arc-wise around the driven axis. Further, the other one of the rotating member and the first output shaft is provided with a stopper protrusion that protrudes into the stopper slot and is allowed to rotate around the driven axis relative to the stopper slot. Hence, by allowing the stopper protrusion to abut against one or the other end portion of the stopper slot, it is possible to limit relative rotations of the first output shaft and the driven shaft with respect to the rotating member. In short, a length of the arc of the stopper slot can limit a width of a phase change of the driven shaft. It is thus possible to set a wider width to a phase change of the driven shaft by forming the stopper slot longer around the driven axis. 
     According to a valve timing adjusting apparatus of a third aspect of the invention, a first cyclone deceleration mechanism composed of the first internal gear, the first eccentric shaft, the first planetary gear, and the first output shaft, and a second cyclone deceleration mechanism composed of the second internal gear, the second eccentric shaft, the second planetary gear, and the second output shaft are provided adjacently to each other on the driven axis. Hence, the first cyclone deceleration mechanism and the second cyclone deceleration mechanism can be provided so as to superimpose in at least one of a direction parallel to and a direction perpendicular to the driven axis. It is thus possible to reduce the apparatus in size. 
     According to a valve timing adjusting apparatus of a fourth aspect of the invention, the first torque and the second torque are obtained by making use of electromagnetic forces induced from the first brake portion and the second brake portion, respectively. Hence, because an electromagnetic force is used in either case of causing a phase change of the driven shaft with respect to the driving shaft to the advancing side or to the retarding side, a response of the phase change can be improved. Moreover, by making use of an electromagnetic force that is hardly influenced by operating conditions, such as a surrounding temperature and an elapsed time since the start of the operation, it is possible to constantly and accurately control a phase change of the driven shaft. 
     According to a valve timing adjusting apparatus of a fifth aspect of the invention, each of the first eccentric shaft and the second eccentric shaft is provided with a function portion fixed thereto so as to rotate together, and each of the first brake portion and the second brake portion includes a solenoid. Also, each of the first torque and the second torque is obtained from a magnetic attraction force induced between the function portion fixed to corresponding one of the first eccentric shaft and the second eccentric shaft, and the solenoid in a switched-ON state included in corresponding one of the first brake portion and the second brake portion. It is thus possible to transmit the first and second torque with a relatively simple arrangement in a reliable manner. 
     According to a valve timing adjusting apparatus of a sixth aspect of the invention, the solenoid in each of the first brake portion and the second brake portion is provided so as to enable a displacement toward the function portion by the magnetic attraction force and so as to be attracted to the function portion. Because the solenoid is magnetically attracted to the function portion that rotates together with the first or second eccentric shaft, the first or second torque in large magnitude can be readily obtained. Further, each of the first brake portion and the second brake portion is provided with a biasing means for pushing the solenoid in a direction to move apart from the corresponding function portion. This arrangement makes it possible to stop transmission of the first or second torque by releasing the solenoid from the function portion with a biasing force of the biasing means while a magnetic attraction force is lowered by switching OFF the solenoid. As has been described, according to the valve timing adjusting apparatus of the sixth aspect of the invention, it is possible to allow each of the first torque and the second torque to act on their respective function portions only when needed in a sufficiently large magnitude. 
     According to a valve timing adjusting apparatus of a seventh aspect of the invention, the solenoid in the first brake portion and the solenoid in the second brake portion are formed into cylindrical shapes having different diameters, one of which is provided at an inner radius of the other. It is thus possible to reduce the apparatus in size. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     FIG. 1 is a cross-sectional view showing one example of a valve timing adjusting apparatus of the invention; 
     FIG. 2 is a cross-sectional view taken along the line II—II of FIG. 1; 
     FIG. 3 is a cross-sectional view taken along the line III—III of FIG. 1; and 
     FIG. 4 is a cross-sectional view taken along the line IV—IV of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description will describe one example of a preferred embodiment of the invention with reference to the accompanying drawings. 
     FIG.  1  through FIG. 4 show an example of a valve timing adjusting apparatus for an engine of the invention. A valve timing adjusting apparatus  10  of this example controls the valve timing of an illustrated intake valve of an engine  2 . 
     The valve timing adjusting apparatus  10  is provided to a transmission system that transmits driving torque of an unillustrated crankshaft of the engine  2  to a camshaft  4  of the engine  2 . As shown in FIG.  2  through FIG. 4, the camshaft  4  opens and closes the intake valve of the engine  2  by rotating around its axis (hereinafter, referred to as the cam axis)  0 . The crankshaft and the camshaft  4  of the engine  2  form the driving shaft and the driven shaft, respectively. The valve timing adjusting apparatus  10  includes a housing  11 , and the housing  11  is fixed to the engine  2  through a stay  6 . 
     A sprocket  12  is supported on the outside walls of the camshaft  4  at one end portion  5  and of a first output shaft  22  at first end portion  23   a  to enable a relative rotation around the cam axis  0 . A chain belt (not shown) is pulled across the sprocket  12  and the crankshaft of the engine  2 . The sprocket  12  rotates around the cam axis  0  with driving torque of the crankshaft transmitted through the chain belt. 
     A first ring gear  14  and a second ring gear  15  are fixed to the inside wall of the sprocket  12 . Each of the first ring gear  14  and the second ring gear  15  is an internal gear whose top curved surface is present at the inner radius of the bottom curved surface. The first ring gear  14  and the second ring gear  15  are aligned on the cam axis  0  in such a manner that their respective rotational center lines coincide with the cam axis  0 . The first ring gear  14  and the second ring gear  15  are allowed to rotate around the cam axis  0  together with the sprocket  12 . The first ring gear  14  and the second ring gear  15  form a first internal gear and a second internal gear, respectively, and the ring gears  14  and  15  and the sprocket  12  together form a rotating member. 
     A first transmission shaft  16  is supported on the outside wall of the first output shaft  22  at the second end portion  23 b to enable a relative rotation around the cam axis  0 . A first eccentric shaft  18 , which is off-center with respect to the cam axis  0 , is fixed to the outside wall of the first transmission shaft  16  at one end. Herein, e 1  of FIG. 2 indicates an eccentric quantity of an axis (hereinafter, referred to as the first eccentric axis) P of the first eccentric shaft  18  with respect to the cam axis  0 . An annular plate of a first function portion  20  using the cam axis  0  as its rotational symmetry axis is provided at the other end of the first transmission shaft  16 . The first transmission shaft  16 , the first eccentric shaft  18 , and the first function portion  20  are all allowed to rotate together around the cam axis  0 . 
     The first end portion  23   a  of the first output shaft  22  has a lager diameter than the second end portion  23   b , and the end portion  5  of the camshaft  4  is fit therein concentrically at the inner radius. The first output shaft  22  and the camshaft  4  are fixedly coupled to each other through a fixing bolt  25  screwed from the second end portion  23   b  side of the first output shaft  22 . The first output shaft  22  is allowed to rotate around the cam axis  0  together with the camshaft  4 . 
     A first planetary gear  30  is provided so as to enable a planetary motion at the outer radius of the center portion of the first output shaft  22 . To be more specific, the first planetary gear  30  is an external gear whose top curved surface is present at the outer radius of the bottom curved surface. The radius of curvature of the top curved surface of the first planetary gear  30  is set smaller than the radius of curvature of the bottom curved surface of the first ring gear  14 , and the number of teeth of the first planetary gear  30  is one less than that of the first ring gear  14 . The first planetary gear  30  is provided with a fitting hole  32  having a circular cross section. The center line of the fitting hole  32  coincides with the rotational center line of the first planetary gear  30 . The first eccentric shaft  18  is fit into the fitting hole  32  through a bearing (not shown), and the first planetary gear  30  is supported on the outside wall of the first eccentric shaft  18  to enable relative rotation around the first eccentric axis P. Here, the first eccentric axis P coincides with the rotational center line of the first planetary gear  30 . When being supported in this manner, part of a plurality of teeth of the first planetary gear  30  engage with part of a plurality of teeth of the first ring gear  14 . 
     When the first planetary gear  30  is not rotating around the first eccentric axis P relative to the first eccentric shaft  18 , the first planetary gear  30 , together with the sprocket  12  and the first eccentric shaft  18 , rotates around the cam axis  0  while being engaged with the first ring gear  14  without changing the relative positional relationship. In a case where the first eccentric shaft  18  rotates around the cam axis  0  in a retarding direction Y relative to the sprocket  12  while the first planetary gear  30  is rotating as above, the first planetary gear  30 , pressed against by the outside wall of the first eccentric shaft  18 , is activated by the first ring gear  14  engaged with the first planetary gear  30 . Then, the first planetary gear  30  starts to rotate around the first eccentric axis P in an advancing direction X relative to the first eccentric shaft  18 . In this case, the first planetary gear  30  rotates around the cam axis  0  in the advancing direction X relative to the sprocket  12  while being engaged with part of the first ring gear  14 . On the other hand, in a case where the first eccentric shaft  18  rotates around the cam axis  0  in the advancing direction X relative to the sprocket  12 , the first planetary gear  30 , pressed against by the outside wall of the first eccentric shaft  18 , is activated by the first ring gear  14 . Then, the first planetary gear  30  starts to rotate around the first eccentric axis P in the retarding direction Y relative to the first eccentric shaft  18 . In this case, the first planetary gear  30  rotates around the cam axis  0  in the retarding direction Y relative to the sprocket  12  while being engaged with part of the first ring gear  14 . 
     An annular plate of a first engagement portion  24 , using the cam axis  0  as its rotational symmetry axis, is formed at the center portion of the first output shaft  22 . The first engagement portion  24  is provided with engagement concave portions  26  at more than one point (in this example, nine points). The plurality of engagement concave portions  26  are provided at regular intervals around the cam axis  0 . Each engagement concave portion  26  is a concave portion of the first engagement portion  24  recessed in the plate thickness direction and has a circular cross section, and its opening portion faces the first planetary gear  30 . Meanwhile, the first planetary gear  30  is provided with engagement protrusions  34  corresponding to the engagement concave portions  26  at more than one point on the outside wall that directly opposes the first engagement portion  24 . The plurality of engagement protrusions  34  are provided at regular intervals around the first eccentric axis P off-center from the cam axis  0  by an eccentric quantity e 1 . Each engagement protrusion  34  is shaped like a pin protruding toward the first engagement portion  24  and has a circular cross section, and is inserted into the corresponding engagement concave portion  26 . The outside diameter of each engagement protrusion  34  is set smaller than the inside diameter of the corresponding engagement concave portion  26 . 
     When the first planetary gear  30  and the sprocket  12  are rotating together, the respective engagement protrusions  34  of the first planetary gear  30  engage with the inner walls of the corresponding engagement concave portions  26  of the first engagement portion  24 , and press the inner walls in the rotational direction (herein, the advancing direction X). The first output shaft  22  and the camshaft  4  fixed thereto thus rotate around the cam axis  0  while maintaining a constant phase relation with respect to the sprocket  12 . In a case where the first planetary gear  30  rotates in the advancing direction X relative to the sprocket  12  while the first output shaft  22  and the camshaft  4  are rotating as above, the respective engagement protrusions  34  further press the inner walls of the engagement concave portions  26  they are engaging with in the rotational direction. This causes the first output shaft  22  and the camshaft  4  to rotate around the cam axis  0  in the advancing direction X relative to the sprocket  12 . On the other hand, in a case where the first planetary gear  30  rotates in the retarding direction Y relative to the sprocket  12 , the respective engagement protrusions  34  press the inner walls of the engagement concave portions  26  they are engaging with in a direction opposite to the rotational direction. This causes the first output shaft  22  and the camshaft  4  to rotate around the cam axis  0  in the retarding direction Y relative to the sprocket  12 . 
     As shown in FIG.  1  and FIG. 3, a stopper slot  35  is formed in the outer edge portion of the first engagement portion  24  of the first output shaft  22 . The stopper slot  35  extends arc-wise about the cam axis  0  in a certain length, and is opened toward the inner wall of the sprocket  12 . A stopper protrusion  37  is formed as an integral part of the inner wall of the sprocket  12  facing the opening portion of the stopper slot  35 . The stopper protrusion  37  protrudes into the stopper slot  35  and extends arc-wise about the cam axis  0  in a length shorter than that of the stopper slot  35 . 
     When the first output shaft  22  rotates relative to the sprocket  12 , the stopper protrusion  37  rotates relatively around the cam axis  0  within the stopper slot  35 . In this instance, an end portion  38   a  of the stopper protrusion  37  on the retarding direction side abuts against an end portion  36   a  of the stopper slot  35  on the retarding direction side, thereby limiting a relative rotation of the first output shaft  22  in the advancing direction X. The limited position is the maximum advancing position of the first output shaft  22 . Also, when an end portion  38   b  of the stopper protrusion  37  on the advancing direction side abuts against an end portion  36   b  of the stopper slot  35  on the advancing direction side, a relative rotation of the first output shaft  22  in the retarding direction Y is limited. The limited position is the maximum retarding position of the first output shaft  22 . As has been described, in this example, the range of a relative rotation for the first output shaft  22  and hence the camshaft  4  is limited by the length of the arc of each of the stopper slot  35  and the stopper protrusion  37 . For example, by giving a relatively long arc to the stopper slot  35  and a relatively short arc to the stopper protrusion  37 , it is possible to secure a wider range of a relative rotation for the camshaft  4 . 
     In this example, the first ring gear  14 , the first transmission shaft  16 , the first eccentric shaft  18 , the first function portion  20 , the first output shaft  22 , the first planetary gear  30 , etc. together form a first cyclone deceleration mechanism. A first brake portion  40  is provided in response to the first cyclone deceleration mechanism. The first brake portion  40  includes a first solenoid  42  and a first coil spring  48  as a biasing means. 
     The first solenoid  42  is formed into a cylindrical shape enclosing a wound coil  43 , and is provided concentrically with the cam axis  0 . The end surface at one end portion of the first solenoid  42  directly opposes a function surface  21  of the first function portion  20 , and a frictional member  45  is fixed thereto. A first supporting shaft  46  protrudes toward the opposite side of the first function portion  20  which is fixed to the second end portion of the first solenoid  42 . The first supporting shaft  46  is supported by the housing  11  to enable a displacement only in the axial direction. This arrangement inhibits the first solenoid  42  from rotating around the cam axis  0 . A first coil spring  48  is disposed between the first supporting shaft  46  and the housing  11 . The first coil spring  48  pushes the first supporting shaft  46  in a direction (direction a of FIG. 1) in which the first solenoid  42  moves apart from the first function portion  20 . 
     The first solenoid  42  is excited when a current passes through the coil  43 , and induces a magnetic attraction force across a space defined by the first solenoid  42  and the first function portion  20 . The magnetic attraction force thus induced causes the first solenoid  42  to be displaced toward the first function portion  20  against a biasing force of the first coil spring  48 , so that the first solenoid  42  is attracted to the first function portion  20  through the frictional member  45 . In a case where the first solenoid  42  is attracted to the first function portion  20  that is rotating, friction between the first function portion  20  and the frictional member  45  produces a first torque in a direction (herein, the retarding direction Y) opposite to the rotational direction of the first function portion  20 . Then, the first torque is transmitted to the first eccentric shaft  18  from the first function portion  20  through the first transmission shaft  16 . Upon transmission of the first torque, the first eccentric shaft  18  starts to rotate around the cam axis  0  in the retarding direction Y relative to the sprocket  12 . On the other hand, the first solenoid  42  in a switched-OFF state is pushed in the direction α of FIG. 1 by a biasing force of the first coil spring  48 , and is thereby released from the first function portion  20  in a reliable manner. 
     A second transmission shaft  50  is supported on the outside wall of the first transmission shaft  16  at the center portion to enable relative rotation around the cam axis  0 . A second eccentric shaft  52 , which is off-center with respect to the cam axis  0 , is formed at one end portion of the second transmission shaft  50 . Herein, e 2  of FIG. 4 indicates an eccentric quantity of an axis (hereinafter, referred to as the second eccentric axis) Q of the second eccentric shaft  52  with respect to the cam axis  0 . An annular plate of a second function portion  54  using the cam axis  0  as its rotational symmetry axis is provided to the center portion of the second transmission shaft  50 . The second transmission shaft  50 , the second eccentric shaft  52 , and the second function portion  54  are allowed to rotate together around the cam axis  0 . 
     A second output shaft  56  is fixedly coupled and concentric to the outside wall of the first transmission shaft  16  at the center portion. The second output shaft  56  is allowed to rotate around the cam axis  0  together with the first transmission shaft  16  and the first eccentric shaft  18 . 
     A second planetary gear  64  is provided so as to enable planetary motion at the outer radius of the center portion of the second output shaft  56 . To be more specific, the second planetary gear  64  is an external gear whose top curved surface is present at the outer radius of the bottom curved surface. The radius of curvature of the top curved surface of the second planetary gear  64  is set smaller than the radius of curvature of the bottom curved surface of the second ring gear  15 , and the number of teeth of the second planetary gear  64  is one less than that of the second ring gear  15 . The second planetary gear  64  is provided with a fitting hole  66  having a circular cross section. The center line of the fitting hole  66  coincides with the rotational center line of the second planetary gear  64 . The second eccentric shaft  52  fits into the fitting hole  66  through a bearing (not shown), and the second planetary gear  64  is supported on the outside wall of the second eccentric shaft  52  to enable a relative rotation around the second eccentric axis Q. Here, the second eccentric axis Q coincides with the rotational center line of the second planetary gear  64 . When being supported in this manner, part of a plurality of teeth of the second planetary gear  64  engages with part of a plurality of teeth of the second ring gear  15 . 
     When the second planetary gear  64  is not rotating around the second eccentric axis Q relative to the second eccentric shaft  52 , the second planetary gear  64 , together with the sprocket  12  and the second eccentric shaft  52 , rotates around the cam axis  0  while being engaged with the second ring gear  15  without changing the relative positional relationship. In a case where the second eccentric shaft  52  rotates around the cam axis  0  in the retarding direction Y relative to the sprocket  12  while the second planetary gear  64  is rotating as above, the second planetary gear  64 , pressed against by the outside wall of the second eccentric shaft  52 , is activated by the second ring gear  15  engaged with the second planetary gear  64 . Then, the second planetary gear  64  starts to rotate around the second eccentric axis Q in the advancing direction X relative to the second eccentric shaft  52 . In this case, the second planetary gear  64  rotates around the cam axis  0  in the advancing direction X relative to the sprocket  12  while being engaged with part of the second ring gear  15 . Herein, an explanation is omitted as to a case where the second eccentric shaft  52  rotates around the cam axis  0  in the advancing direction X relative to the sprocket  12 , because it is not necessary for the description of the invention. 
     An annular plate of a second engagement portion  60  using the cam axis  0  as its rotational symmetry axis is formed at one end portion of the second output shaft  56 . The second engagement portion  60  is provided with engagement holes  62  at more than one point (in this example, nine points). The plurality of engagement holes  62  are provided at regular intervals around the cam axis  0 . Each engagement hole  62  is a hole penetrating through the second engagement portion  60  in the plate thickness direction and having a circular cross section, and its one opening portion faces the second planetary gear  64 . Meanwhile, the second planetary gear  64  is provided with engagement protrusions  68  corresponding to the engagement holes  62  at more than one point on the outside wall that directly opposes the second engagement portion  60 . The plurality of engagement protrusions  68  are provided at regular intervals around the second eccentric axis Q off-center from the cam axis  0  by an eccentric quantity e 2 . Each engagement protrusion  68  is shaped like a pin protruding toward the second engagement portion  60  and has a circular cross section, and is inserted into the corresponding engagement hole  62 . The outside diameter of each engagement protrusion  68  is set smaller than the inside diameter of the corresponding engagement hole  62 . 
     When the second planetary gear  64  and the sprocket  12  are rotating together, the respective engagement protrusions  68  of the second planetary gear  64  engage with the inner walls of the corresponding engagement holes  62  of the second engagement portion  60 , and press the inner walls in the rotational direction (herein, the advancing direction X). The second output shaft  56  and the first eccentric shaft  18  coupled thereto through the first transmission shaft  16  thus rotate around the cam axis  0  while maintaining a constant phase relation with respect to the sprocket  12 . In a case where the second planetary gear  64  rotates in the advancing direction X relative to the sprocket  12  while the second output shaft  56  and the first eccentric shaft  18  are rotating as above, the respective engagement protrusions  68  further press the inner walls of the engagement holes  62  they are engaging with in the rotational direction. This causes the second output shaft  56  and the first eccentric shaft  18  to rotate around the cam axis  0  in the advancing direction X relative to the sprocket  12 . 
     In this example, the second ring gear  15 , the second transmission shaft  50 , the second eccentric shaft  52 , the second function portion  54 , the second output shaft  56 , the second planetary gear  64 , etc. together form a second cyclone deceleration mechanism. As shown in FIG. 1, the second cyclone deceleration mechanism and the first cyclone deceleration mechanism are provided adjacent to each other and superimposed in both a direction parallel to and a direction perpendicular to the cam axis  0 . This arrangement reduces the valve timing adjusting apparatus  10  in size. 
     A second brake portion  70  is provided in response to the second cyclone deceleration mechanism. The second brake portion  70  includes a second solenoid  72  and a second coil spring  78  as a biasing means. The second solenoid  72  is formed into a cylindrical shape enclosing a wound coil  73 , and is provided concentrically with the cam axis  0 . The second solenoid  72  of this example has a larger diameter than the first solenoid  42 , so that part of the first solenoid  42  is inserted at the inner radius of the second solenoid  72 . This arrangement makes it possible to utilize a space at the inner radius of the second solenoid  72  effectively, and the valve timing adjusting apparatus  10  can be thus reduced in size. 
     The end surface at one end portion of the second solenoid  72  directly opposes a function surface  55  of the second function portion  54 , and a frictional member  75  is fixed thereto. A second supporting shaft  76  protruding toward the opposite side of the second function portion  54  is fixed to the second end portion (far portion) of the second solenoid  72 . The second supporting shaft  76  is supported by the housing  11  to enable a displacement only in the axial direction. This arrangement inhibits the second solenoid  72  from rotating around the cam axis  0 . A second coil spring  78  is disposed between the second supporting shaft  76  and the housing  11 . The second coil spring  78  pushes the second supporting shaft  76  in a direction (direction β of FIG. 1) in which the second solenoid  72  is moved apart from the second function portion  54 . 
     The second solenoid  72  is excited when a current passes through the coil  73 , and induces a magnetic attraction force across a space defined by the second solenoid  72  and the second function portion  54 . The magnetic attraction force thus induced causes the second solenoid  72  to be displaced toward the second function portion  54  against a biasing force of the second coil spring  78  so that the second solenoid  72  is attracted to the second function portion  54  through the frictional member  75 . 
     In a case where the second solenoid  72  is attracted to the second function portion  54  that is rotating, friction between the second function portion  54  and the frictional member  75  produces a second torque in a direction (herein, the retarding direction Y) opposite to the rotational direction of the second function portion  54 . Then, the second torque is transmitted to the second eccentric shaft  52  from the second function portion  54  through the second transmission shaft  50 . Upon transmission of the second torque, the second eccentric shaft  52  starts to rotate around the cam axis  0  in the retarding direction Y relative to the sprocket  12 . On the other hand, the second solenoid  72  in a switched-OFF state is pushed in the direction β of FIG. 1 by a biasing force of the second coil spring  78 , and is thereby reliably released from the second function portion  54 . 
     An operation of the valve timing adjusting apparatus  10  will now be explained. When the crankshaft of the engine  2  is driven to rotate while the first solenoid  42  of the first brake portion  40  and the second solenoid  72  of the second brake portion  70  are both in a switched-OFF state, driving torque of the crankshaft is transmitted to the sprocket  12 . The sprocket  12  and the first and second ring gears  14  and  15 , fixed thereto, then start to rotate together. It should be noted that the phase of the sprocket  12  with respect to the crankshaft is maintained as a constant. In this instance, because the first solenoid  42  in the switched-OFF state is released from the first function portion  20 , the first torque is not transmitted to the first eccentric shaft  18 , and therefore, the first eccentric shaft  18  will not rotate relative to the sprocket  12 . Hence, the first planetary gear  30  and the first eccentric shaft  18  start to rotate together with the sprocket  12  in association with a rotation of the sprocket  12 . The first output shaft  22  and the camshaft  4  engaged with the first planetary gear  30  thus start to rotate at a certain phase with respect to the sprocket  12 . 
     Also, while the sprocket  12  is rotating, the second solenoid  72  in the switched-OFF state is released from the second function portion  54 , and the second torque is not transmitted to the second eccentric shaft  52 . The second eccentric shaft  52 , therefore, will not rotate relative to the sprocket  12 . Hence, in this instance, the second planetary gear  64  and the second eccentric shaft  52  start to rotate together with the sprocket  12 . The second output shaft  56  engaged with the second planetary gear  64  thus start to rotate together with the first transmission shaft  16  and the first eccentric shaft  18 . 
     When the first solenoid  42  alone is switched ON while the sprocket  12  is rotating, the first solenoid  42  is magnetic attracted to the first function portion  20  that is rotating Then, the first torque, produced by friction between the frictional member  45  at the end portion of the first solenoid  42  and the first function portion  20 , is transmitted to the first eccentric shaft  18 . Upon receipt of the first torque, the first eccentric shaft  18  starts to rotate in the retarding direction Y relative to the sprocket  12  to decelerate. The first planetary gear  30  is activated by this relative rotation of the first eccentric shaft  18  in the retarding direction Y, and starts to rotate in the advancing direction X relative to the sprocket  12  while maintaining rotation in the advancing direction X relative to the first eccentric shaft  18 . The first output shaft  22  and the camshaft  4 , engaged with the first planetary gear  30 , thus start to rotate in the advancing direction X relative to the sprocket  12  in order to accelerate. In other words, the phase of the camshaft  4  with respect to the sprocket  12  changes to the advancing side, and so does the phase of the camshaft  4  with respect to the crankshaft. The relative rotations of the first output shaft  22  and the camshaft  4  in the advancing direction X are limited by abutment of the stopper protrusion end portion  38   a  against the stopper slot end portion  36   a.    
     On the other hand, when the second solenoid  72  alone is switched ON while the sprocket  12  is rotating, the second solenoid  72  is magnetically attracted to the second function portion  54  that is rotating, and the second torque produced friction between the frictional member  75  at the end portion of the second solenoid  72  and the second function portion  54  is transmitted to the second eccentric shaft  52 . Upon receipt of the second torque, the second eccentric shaft  52  starts to rotate in the retarding direction Y relative to the sprocket  12  for deceleration. The second planetary gear  64  is activated by this relative rotation of the second eccentric shaft  52  in the retarding direction Y, and starts to rotate in the advancing direction X relative to the sprocket  12  while maintaining rotation in the advancing direction X relative to the second eccentric shaft  52 . The second output shaft  56  and the first eccentric shaft  18  engaged with the second planetary gear  64  thus start to rotate in the advancing direction X relative to the sprocket  12  in order to accelerate. 
     Continuing, the first planetary gear  30  is activated by this relative rotation of the first eccentric shaft  18  in the advancing direction X, and starts to rotate in the retarding direction Y relative to the sprocket  12  while maintaining rotation in the retarding direction Y relative to the first eccentric shaft  18 . The first output shaft  22  and the camshaft  4  engaged with the first planetary gear  30  thus start to rotate in the retarding direction Y relative to the sprocket  12  in order to decelerate. In other words, the phase of the camshaft  4  with respect to the sprocket  12  changes to the retarding side, and so does the phase of the camshaft  4  with respect to the crankshaft. It should be noted that the relative rotations of the first output shaft  22  and the camshaft  4  in the retarding direction Y are limited by abutment of the stopper protrusion end portion  38   b  against the stopper slot end portion  36   b.    
     As has been described, according to the valve timing adjusting apparatus  10 , a displacement of each component forming the first cyclone deceleration mechanism and the second cyclone deceleration mechanism is achieved by relative rotations around the cam axis  0  with respect to the sprocket  12 . This makes it possible to secure a wider range of relative rotations around the cam axis  0  for the components forming the first and second cyclone deceleration mechanisms that determine a width of a phase change of the camshaft  4 . It is thus possible to extend a width of a phase change of the camshaft  4  without increasing the apparatus in size. 
     Further, according to the valve timing adjusting apparatus  10 , in either case of causing a phase change of the camshaft  4  to the advancing side or to the retarding side, the first torque and the second torque that induce the phase change are produced by making use of electromagnetic forces of the first solenoid  42  and the second solenoid  72 , respectively. This improves a response of a phase change, that is, since the first and second solenoids  42  and  72  are switched ON until a phase change of the camshaft  4  takes place. Also, in general, the electromagnetic force is hardly influenced by operating conditions, such as the surrounding temperature of the apparatus and the elapsed time since the start of the operation. It is thus possible to control a phase change of the camshaft  4  with accuracy under low-temperature circumstances or during engine start-up. 
     Furthermore, according to the valve timing adjusting apparatus  10 , in order to obtain the first torque and the second torque, the first solenoid  42  and the second solenoid  72  are attracted to the first function portion  20  and the second function portion  54 , respectively, that are rotating. For this reason, torque in a large magnitude can be obtained from a small magnetic attraction force. It is thus possible not only to compactly form the first and second solenoid  42  and  72 , but also to reduce a quantity of electricity. 
     In the example above, both the first brake portion  40  and the second brake portion  70  are arranged to obtain the first torque and the second torque, respectively, by making use of an electromagnetic force. However, it may be arranged in such a manner that at least one of the first torque and the second torque is obtained by, for example, making use of an elastic force of an elastic member. Also, in the example above, the first solenoid  42  and the second solenoid  72  are attracted to the first function portion  20  and the second function portion  54 , respectively. However, they are not necessarily attracted to the corresponding function portions. 
     Moreover, the example above adopts an arrangement that the first eccentric shaft  18  is constantly coupled to the second output shaft  56  through the first transmission shaft  16 . However, a clutch mechanism or the like such that can release the coupling may be provided somewhere between the first eccentric shaft  18  and the second output shaft  56 . 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.