Patent Publication Number: US-2022220869-A1

Title: Valve timing adjustment device

Description:
TECHNICAL FIELD 
     The present invention relates to a valve timing adjustment device. 
     BACKGROUND ART 
     A hydraulic variable valve timing adjustment device, which controls opening and closing timing of an intake valve or an exhaust valve of an internal combustion engine for an automobile, is generally known. A hydraulic variable valve timing adjustment device includes a housing, which rotates in synchronization with a crankshaft, and a vane rotor, which rotates in synchronization with a camshaft. The vane of the vane rotor divides each of a plurality of hydraulic chambers inside the housing into either a retard chamber or an advance chamber. The hydraulic variable valve timing adjustment device controls the opening and closing timing of the intake valve or the exhaust valve by supplying the hydraulic oil to the retard chamber or the advance chamber to change the rotational phase of the vane rotor with respect to the housing to the retard side or the advance side. 
     In order to lock the rotational phase of the vane rotor with respect to the housing to a specific phase at the time of starting the internal combustion engine, the valve timing adjustment device as described above has a mechanism for applying an assist torque to the vane rotor so as to change the rotational phase to the specific phase when the internal combustion engine is stopped (hereinafter, the specific phase is referred to as a lock phase). An example of a valve timing adjustment device having such a mechanism is the valve timing adjustment device described in Patent Literature 1. The valve timing adjustment device includes: a front plate installed in a housing; a bush which is a holder installed on a rotating shaft of a vane rotor; and a spiral spring whose innermost peripheral portion is wound around the bush. 
     The front plate includes a first stopper that is a projection portion. In a case where the rotational phase described above changes to the retard side, the outermost peripheral portion of the spiral spring is caught by the first stopper and the spiral spring urges the vane rotor toward the advance side. As a result, the vane rotor rotates relative to the housing, and the rotational phase described above thus returns to the intermediate phase. Moreover, the bush includes an arm having a second stopper which is a projection portion. In a case where the rotational phase described above changes to the advance side, the spiral spring does not urge the vane rotor because the outermost peripheral portion thereof is caught by the second stopper and the spiral spring is separated from the first stopper. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2010-180862A 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the valve timing adjustment device described in Patent Literature 1 as described above, there is a problem that vibration of the engine during operation is transmitted to the spiral spring, and the spiral spring is damaged or dropped due to resonance. 
     The present invention has been made to solve the above problem, and an object of the present invention is to provide a technique for suppressing resonance of a spiral spring due to vibration of an engine during operation. 
     Solution to Problem 
     A valve timing adjustment device according to present invention includes: a first rotating body that rotates synchronously with a crankshaft; and a second rotating body that rotates synchronously with a camshaft. The first rotating body includes a plate having an opening portion around a rotation axis. The second rotating body includes: a main body portion that is disposed to pass through the opening portion of the plate and is disposed around the rotation axis; and a holder having a first arm and a second arm that each extends to an outer peripheral side from an end portion of a part of the main body portion projecting from a front surface of the plate. A spiral spring is installed between the front surface of the plate and the first and the second arms, in which the spiral spring is wound around the main body portion, an inner peripheral side end portion of the spiral spring is held by the plate, and a terminal hook portion of the spiral spring is formed by bending an outer peripheral side end portion toward an outer peripheral side. A first arm projection portion is caught by the terminal hook portion of the spiral spring, is urged toward a lock phase side by the spiral spring and is installed on a face opposite to the front surface of the plate in the first arm in a case where a rotational phase of the second rotating body with respect to the first rotating body is on a first rotational phase side. A second arm projection portion abuts on an outermost peripheral portion of the spiral spring and is installed on a face opposite to the front surface of the plate in the second arm in a case where the rotational phase is on the first rotational phase side. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to suppress resonance of the spiral spring due to vibration of the engine during operation. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view illustrating the configuration of a valve timing adjustment device according to a first embodiment. 
         FIG. 2  is a cross-sectional view illustrating a cross section of the valve timing adjustment device illustrated in  FIG. 1  taken along dotted line A. 
         FIG. 3  is a front view illustrating the configuration of the valve timing adjustment device in a case where a rotational phase of a second rotating body with respect to a first rotating body is a first rotational phase. 
         FIG. 4  is a front view illustrating the configuration of the valve timing adjustment device in a case where the rotational phase of the second rotating body with respect to the first rotating body is in the second rotational phase side. 
         FIG. 5  is a graph illustrating a change in assist torque in accordance with a change in the rotational phase of the second rotating body with respect to the first rotating body. 
         FIG. 6A  is a front view illustrating a holder included in the valve timing adjustment device according to a first modification.  FIG. 6B  is a cross-sectional view of the holder illustrated in  FIG. 6A  taken along line B. 
         FIG. 7  is a graph illustrating a change in a load applied to an unequal pitch spring in accordance with a change in the rotational phase of the second rotating body with respect to the first rotating body. 
         FIG. 8A  is a front view illustrating a plate included in the valve timing adjustment device according to a second modification.  FIG. 8B  is a cross-sectional view of the plate illustrated in  FIG. 8A  taken along line C. 
         FIG. 9A  is a front view illustrating the configuration of a valve timing adjustment device including a spiral spring according to a third modification.  FIG. 9B  is a diagram illustrating only a terminal hook portion, a terminal hook catching portion, and a first arm projection portion of the spiral spring in the valve timing adjustment device illustrated in  FIG. 9A . 
         FIG. 10A  illustrates the configuration of the valve timing adjustment device illustrated in  FIG. 9A  in which a rotational phase of the second rotating body with respect to the first rotating body is on a first rotational phase side.  FIG. 10B  is a diagram illustrating only the terminal hook portion, the terminal hook catching portion, and a first arm projection portion of the spiral spring in the valve timing adjustment device  100  illustrated in  FIG. 10A . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, in order to explain the present invention in more detail, an embodiment for carrying out the present invention will be described with reference to the accompanying drawings. 
     First Embodiment 
       FIG. 1  is a plan view illustrating the configuration of a valve timing adjustment device  100  according to a first embodiment.  FIG. 2  is a cross-sectional view illustrating a cross section of the valve timing adjustment device  100  illustrated in  FIG. 1  taken along dotted line A. As illustrated in  FIG. 1 or 2 , the valve timing adjustment device  100  includes: a plate  1  having an opening portion  1   a  around a rotation axis R; a case  2  fixed to the back surface of the plate  1 ; a rotor  3  installed inside the case  2 ; and a holder  4  having a main body portion  4   a  passing through the opening portion  1   a  of the plate  1  and disposed around the rotation axis R. Note that, hereinafter, a surface of the plate  1  to which the case  2  is fixed is referred to as a back surface, and a surface of the plate  1  opposite to the back surface is referred to as a front surface. 
     More specifically, the valve timing adjustment device  100  has a chain sprocket portion  2   a  on the outer peripheral surface of the case  2 . A chain (not illustrated) is attached to the chain sprocket portion  2   a , and a driving force of a crankshaft of the internal combustion engine is transmitted to the chain sprocket portion  2   a  via the chain. Thus, the case  2  and the plate  1  fixed to the case  2  constitute a first rotating body that rotates synchronously with the crankshaft. 
     The main body portion  4   a  of the holder  4  has a cylindrical shape with one bottom face opened, and the other bottom face of the cylinder is fixed to the holder  4  by a center bolt  5 . The rotor  3  is fastened to a camshaft of an internal combustion engine (not shown) by the center bolt  5  together with the main body portion  4   a  of the holder  4 . Thus, the rotor  3  and the holder  4  constitute a second rotating body that rotates synchronously with the camshaft. 
     Moreover, the case  2  forms a plurality of hydraulic chambers inside, and the rotor  3  functions as a vane rotor and divides each hydraulic chamber of the case  2  into an advance side hydraulic chamber and a retard side hydraulic chamber. The plate  1  seals each of the advance side hydraulic chamber and the retard side hydraulic chamber. 
     When the hydraulic oil is supplied to or discharged from the advance side hydraulic chamber or the retard side hydraulic chamber, the second rotating body rotates to the advance side or the retard side with respect to the first rotating body. As a result, the rotational phase of the camshaft with respect to the crankshaft changes to the advance side or the retard side, and the opening and closing timing of an intake valve or an exhaust valve change. Note that, hereinafter, a direction in which the second rotating body rotates clockwise with respect to the first rotating body is referred to as an advance side, and a direction in which the second rotating body rotates counterclockwise is referred to as a retard side. Moreover, the rotational phase of the second rotating body with respect to the first rotating body in the valve timing adjustment device  100  illustrated in  FIG. 1  is an intermediate phase between the advance side phase and the retard side phase, and in the first embodiment, the intermediate phase is set as a lock phase. 
     Next, a mechanism in which the valve timing adjustment device  100  according to the first embodiment applies an assist torque to the second rotating body when the internal combustion engine is stopping, will be described. As illustrated in  FIG. 1 or 2 , the holder  4  includes a first arm  4   b  and a second arm  4   c , which extend to the outer peripheral side from the end portion of the portion of the main body portion  4   a  projecting from the front surface of the plate  1 . Note that, hereinafter, the “outer periphery” of the “outer peripheral side” means the outer periphery of a circle when the shape of the valve timing adjustment device  100  is regarded as the circle in a case where the valve timing adjustment device  100  is viewed from the front as illustrated in  FIG. 1 . 
     A spiral spring  6  wound around the main body portion  4   a  is installed between the front surface of the plate  1  and the first arm  4   b  and the second arm  4   c . More specifically, the spiral spring  6  is wound around the main body portion  4   a  so as to be gradually apart from the rotation axis R from one end portion toward the other end portion. Hereinafter, the one end portion is referred to as an inner peripheral side end portion, and the other end portion is referred to as an outer peripheral side end portion. Furthermore, the spiral spring  6  is wound around the main body portion  4   a  so that the inner peripheral portion and the corresponding outer peripheral portion do not come into contact with each other at any position. As a result, the spiral spring  6  has a spiral structure in which friction hardly occurs. 
     The inner peripheral side end portion of the spiral spring  6  is held by the plate  1 . More specifically, the starting end hook portion  6   a  is formed by bending the inner peripheral side end portion of the spiral spring  6  toward the rotation axis R. A starting end hook catching portion  1   b  is installed on the front surface of the plate  1 . The starting end hook portion  6   a  is held by the plate  1  by being caught by the starting end hook catching portion  1   b.    
     The spiral spring  6  has a terminal hook portion  6   b  formed by bending the outer peripheral side end portion toward the outer peripheral side. On the front surface of the plate  1 , a terminal hook catching portion  1   c  is installed. As in the valve timing adjustment device  100  illustrated in  FIG. 1 , when the rotational phase of the second rotating body with respect to the first rotating body is the lock phase, the terminal hook portion  6   b  is held by the plate  1  by being caught by the terminal hook catching portion  1   c . Note that, at this time, no assist torque is applied to the second rotating body. 
     A first plate projection portion  1   d  is installed on the front surface of the plate  1 . As in the valve timing adjustment device  100  illustrated in  FIG. 1 , when the rotational phase of the second rotating body with respect to the first rotating body is the lock phase, the first plate projection portion  1   d  abuts on the outermost peripheral portion of the spiral spring. As a result, the vibration of the engine transmitted to the spiral spring  6  through the terminal hook catching portion  1   c  is transmitted from the portion in contact with the terminal hook catching portion  1   c  to the portion in contact with the first plate projection portion  1   d  on the outermost periphery of the spiral spring  6 , but is hardly transmitted beyond the latter portion. 
     On the front surface of the plate  1 , a second plate projection portion  1   e  that abuts on the innermost peripheral portion of the spiral spring  6  is installed. Accordingly, when the spiral spring  6  is wound around the main body portion  4   a  of the holder  4 , the second plate projection portion  1   e  serves as a guide. More specifically, the starting end hook portion  6   a  is hooked on the starting end hook catching portion  1   b , and a portion of the spiral spring  6  extending from the starting end hook portion  6   a  is brought into contact with the second plate projection portion  1   e  and wound around the main body portion  4   a  of the holder  4 . Furthermore, the vibration of the engine transmitted to the spiral spring  6  through the starting end hook catching portion  1   b  is transmitted from the portion in contact with the starting end hook catching portion  1   b  to the portion in contact with the second plate projection portion  1   e  on the innermost periphery of the spiral spring  6 , but is hardly transmitted beyond the latter portion. 
     More specifically, as for the arrangement of the second plate projection portion  1   e , the second plate projection portion  1   e  is installed on the front surface of the plate  1  in a region from the starting end hook catching portion  1   b  up to 180 degrees toward the direction in which the spiral spring  6  is wound with reference to the rotation axis R. Accordingly, in a case where the second plate projection portion  1   e  is used as a guide, the spiral spring  6  is easily wound around the main body portion  4   a  of the holder  4 . Furthermore, the spiral spring  6  can limit a region to which the vibration of the engine is transmitted. 
     As for the arrangement of the first plate projection portion  1   d , more specifically, the first plate projection portion  1   d  is installed on the front surface of the plate  1  on the side opposite to the second plate projection portion  1   e  with reference to the rotation axis R. Further more specifically, in a case where a line connecting the second plate projection portion  1   e  and the rotation axis R at the shortest distance is defined as a line α, a line perpendicular to the line α and orthogonal to the rotation axis R is defined as a line β, and the front surface of the plate  1  is divided into a region including the second plate projection portion  1   e  and a region not including the second plate projection portion  1   e  with the line β as a boundary, the first plate projection portion  1   d  is installed in the region not including the second plate projection portion  1   e.    
     As a result, the first plate projection portion  1   d  becomes an obstacle to the spiral spring  6 , and the center of the spiral structure is less likely to be eccentric to the side opposite to the second plate projection portion  1   e  side with reference to the rotation axis R. More specifically, when the spiral spring  6  moves to the side opposite to the second plate projection portion  1   e  with reference to the rotation axis R while the innermost circumference of the spiral spring  6  abuts on the second plate projection portion  1   e , a portion of the spiral spring  6  abuts on the second plate projection portion  1   e  and a portion on the outer circumferential side corresponding to the portion come into contact with each other, which causes a problem of friction. 
     Therefore, as described above, since the first plate projection portion  1   d  is installed in the region not including the second plate projection portion  1   e , the first plate projection portion  1   d  becomes an obstacle, the spiral spring  6  hardly moves to the side opposite to the second plate projection portion  1   e  side with reference to the rotation axis R, and the portion of the spiral spring  6  in contact with the second plate projection portion  1   e  and the portion on the outer peripheral side corresponding to the portion hardly come into contact with each other, so that friction is hardly generated. 
     Next, the valve timing adjustment device  100  in a case where the rotational phase of the second rotating body with respect to the first rotating body is on a first rotational phase side will be described with reference to the drawings.  FIG. 3  is a front view illustrating the configuration of the valve timing adjustment device  100  in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side. Note that, in the first embodiment, the first rotational phase side is a retard side with reference to the intermediate phase. 
     As illustrated in  FIG. 1 ,  FIG. 2  or  FIG. 3 , a first arm projection portion  4   d  is installed on a surface of the first arm  4   b  facing the front surface of the plate  1 . As in the valve timing adjustment device  100  illustrated in  FIG. 3 , in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, the first arm projection portion  4   d  is caught by the terminal hook portion  6   b  of the spiral spring  6  and urged toward the lock phase side by the spiral spring  6 . Note that, herein, the lock phase side is an advance side. 
     More specifically, in the process in which the rotational phase of the second rotating body with respect to the first rotating body changes from the intermediate phase which is the lock phase to the retard side which is the first rotational phase side, the first arm projection portion  4   d  is caught by the terminal hook portion  6   b  of the spiral spring  6 , thereby the terminal hook portion  6   b  is separated from the terminal hook catching portion  1   c . The spiral spring  6  is deformed when the first arm projection portion  4   d  is caught by the terminal hook portion  6   b . The deformed spiral spring  6  urges the first arm projection portion  4   d  toward the advance side which is the lock phase side by the restoring force. As a result, the assist torque is applied to the second rotating body, and the rotational phase of the second rotating body with respect to the first rotating body changes from the first rotational phase side to the intermediate phase that is the lock phase. 
     Moreover, a second arm projection portion  4   e  is installed on a surface of the second arm  4   c  facing the front surface of the plate  1 . As in the valve timing adjustment device  100  illustrated in  FIG. 3 , when the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, the second arm projection portion  4   e  abuts on the outermost peripheral portion of the spiral spring  6 . 
     More specifically, in the process in which the rotational phase of the second rotating body with respect to the first rotating body changes from the intermediate phase, which is the lock phase, to the retard side, which is the first rotational phase side, the second arm projection portion  4   e  gradually moves toward the spiral spring  6  side while moving toward the retard side along the locus T in a state of abutting on the outermost peripheral portion of the spiral spring  6 , and urges the portion toward the rotation axis R, thereby the outermost peripheral portion of the spiral spring  6  is deformed and separated from the first plate projection portion  1   d . This eliminates friction between the outermost peripheral portion of the spiral spring  6  and the first plate projection portion  1   d.    
     Moreover, in this process, the outermost peripheral portion of the spiral spring  6  is deformed by the terminal hook portion  6   b  being caught by the first arm projection portion  4   d , and moves rotationally to the retard side by the amount of movement of the first arm projection portion  4   d  to the retard side. That is, in the process, the second arm projection portion  4   e  and the outermost peripheral portion of the spiral spring  6  both move to the retard side while being in contact with each other. Therefore, friction hardly occurs between the second arm projection portion  4   e  and the outermost peripheral portion of the spiral spring  6 . Furthermore, when the second arm projection portion  4   e  and the outermost peripheral portion of the spiral spring  6  abut on each other, the vibration of the engine transmitted to the spiral spring  6  via the terminal hook catching portion  1   c  is transmitted from the portion in contact with the terminal hook catching portion  1   c  at the outermost periphery of the spiral spring  6  to the portion in contact with the second arm projection portion  4   e  but is hardly transmitted beyond the latter portion. 
     More specifically, as for the above-described arrangement of the second arm projection portion  4   e , in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, the second arm projection portion  4   e  is located on the side opposite to the second plate projection portion  1   e  side with reference to the rotation axis R. More specifically, in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, the second arm projection portion  4   e  is installed in the region of the front surface of the plate  1  that does not include the second plate projection portion  1   e  with the above-described line β as a boundary. 
     As a result, in the spiral spring  6 , the second arm projection portion  4   e  becomes an obstacle, and the center of the spiral structure is less likely to be eccentric to the side opposite to the second plate projection portion  1   e  side with reference to the rotation axis R. More specifically, the second arm projection portion  4   e  becomes an obstacle, the spiral spring  6  is less likely to move to the side opposite to the second plate projection portion  1   e  side with reference to the rotation axis R, a portion of the spiral spring  6  in contact with the second plate projection portion  1   e  and a portion on the outer peripheral side corresponding to the portion are less likely to come into contact, and friction is less likely to occur. 
     Next, the valve timing adjustment device  100  in a case where the rotational phase of the second rotating body with respect to the first rotating body is on a second rotational phase side will be described with reference to the drawings.  FIG. 4  is a front view illustrating the configuration of the valve timing adjustment device  100  in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the second rotational phase side. Note that, in the first embodiment, the second rotational phase side is an advance side with reference to the intermediate phase. 
     As in the valve timing adjustment device  100  illustrated in  FIG. 4 , in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the second rotational phase side, the terminal hook portion  6   b  is held by the plate  1  by being caught by the terminal hook catching portion  1   c . More specifically, when the rotational phase of the second rotating body with respect to the first rotating body changes from the retard side, which is the first rotational phase side, to the intermediate phase, which is the lock phase, the terminal hook portion  6   b  is caught by the terminal hook catching portion  1   c  to be separated from the first arm projection portion  4   d . Then, in the process in which the rotational phase of the second rotating body with respect to the first rotating body changes from the intermediate phase, which is the lock phase, to the advance side, which is the second rotational phase side, the terminal hook portion  6   b  is further separated from the first arm projection portion  4   d . As a result, the assist torque by the spiral spring  6 , which is described above, is not applied to the second rotating body. 
     Moreover, as in the valve timing adjustment device  100  illustrated in  FIG. 4 , in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the second rotational phase side, the first plate projection portion  1   d  abuts on the outermost peripheral portion of the spiral spring. More specifically, in the process in which the rotational phase of the second rotating body with respect to the first rotating body changes from the retard side, which is the first rotational phase side, to the intermediate phase, which is the lock phase, the second arm projection portion  4   e  moves so as to be gradually apart from the spiral spring  6  side while moving to the advance side along the locus T in a state of abutting on the outermost peripheral portion of the spiral spring  6 , thereby the outermost periphery of the spiral spring  6  gradually returns to the original shape by the restoring force. Then, when the rotational phase of the second rotating body with respect to the first rotating body reaches the intermediate phase that is the lock phase, the outermost periphery of the spiral spring  6  abuts on the first plate projection portion  1   d . When the rotational phase reaches the advance side which is the second rotational phase side, the second arm projection portion  4   e  is completely separated from the outermost periphery of the spiral spring  6 . 
     Furthermore, in the process in which the rotational phase of the second rotating body with respect to the first rotating body changes from the retard side, which is the first rotational phase side, to the intermediate phase, which is the lock phase, the outermost peripheral portion of the spiral spring  6  returns to the original shape by the restoring force and moves to the advance side as the terminal hook portion  6   b  is separated from the first arm projection portion  4   d . That is, in the process, the second arm projection portion  4   e  and the outermost peripheral portion of the spiral spring  6  are separated from each other while moving toward the advance side. As a result, friction is less likely to occur between the second arm projection portion  4   e  and the outermost peripheral portion of the spiral spring  6 . Moreover, since the outermost periphery of the spiral spring  6  abuts on the first plate projection portion  1   d , the vibration of the engine transmitted to the spiral spring  6  via the terminal hook catching portion  1   c  is transmitted from the portion in contact with the terminal hook catching portion  1   c  to the portion in contact with the first plate projection portion  1   d  on the outermost periphery of the spiral spring  6 , but is hardly transmitted beyond the latter portion. 
     As described above, the second arm projection portion  4   e  is configured to be separated from the outermost periphery of the spiral spring  6  in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the second rotational phase side. For example, in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the second rotational phase side, the arrangement of the second arm projection portion  4   e  and the second arm  4   c  is adjusted so as to be separated from the outermost periphery of the spiral spring  6 . Alternatively, for example, in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the second rotational phase side, the curvature of the spiral spring  6  wound around the main body portion  4   a  on the outermost periphery of the spiral spring  6  is adjusted so as to be separated from the outermost periphery of the spiral spring  6 . 
     As described above, the valve timing adjustment device  100  according to the first embodiment applies the assist torque to the second rotating body by the spiral spring  6  in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side. In a case where the rotational phase is on the second rotational phase side, the assist torque is not applied to the second rotating body.  FIG. 5  is a graph illustrating a change in assist torque in accordance with a change in the rotational phase of the second rotating body with respect to the first rotating body. The vertical axis in  FIG. 5  represents the assist torque to the second rotating body, and the horizontal axis in  FIG. 5  represents the rotational phase of the second rotating body with respect to the first rotating body. Note that the assist torque illustrated in  FIG. 5  is also in consideration of friction against the spiral spring  6  or the second rotating body. 
     As illustrated in  FIG. 5 , the assist torque applied to the second rotating body continues to increase in the course of the rotational phase of the second rotating body with respect to the first rotating body changing from the intermediate phase to the retard side, which is on the first rotational phase side, and reaching the maximum retarded phase. More specifically, in the process, the spiral spring  6  in which the terminal hook portion  6   b  is caught by the first arm projection portion  4   d  is gradually deformed, and the assist torque to the second rotating body increases as the restoring force increases. 
     Furthermore, on the other hand, in the course of the rotational phase of the second rotating body with respect to the first rotating body from the most retarded phase to the intermediate phase, the assist torque to the second rotating body continues to decrease. More specifically, in the process, the spiral spring  6  in which the terminal hook portion  6   b  is caught by the first arm projection portion  4   d  gradually returns to the original shape, and the restoring force decreases, so that the assist torque to the second rotating body decreases. 
     As described above, in the process in which the rotational phase of the second rotating body with respect to the first rotating body changes from the intermediate phase, which is the lock phase, to the retard side, which is on the first rotational phase side, the second arm projection portion  4   e  and the outermost peripheral portion of the spiral spring  6  both move to the retard side in a state of being in contact with each other. Moreover, in the process in which the rotational phase of the second rotating body with respect to the first rotating body changes from the retard side, which is the first rotational phase side, to the intermediate phase, which is the lock phase, the second arm projection portion  4   e  and the outermost peripheral portion of the spiral spring  6  are separated from each other while moving toward the advance side together. 
     As a result, friction hardly occurs between the second arm projection portion  4   e  and the outermost peripheral portion of the spiral spring  6 , so that it is possible to suppress hysteresis generated between a process, in which the rotational phase of the second rotating body with respect to the first rotating body changes from the intermediate phase that is the lock position, to the retard side that is the first rotational phase side, and a process in which that rotational phase changes from the retard side that is the first rotational phase side to the intermediate phase that is the lock position. 
     Further, when the rotational phase of the second rotating body with respect to the first rotating body reaches the intermediate phase from the most retarded phase, the terminal hook portion  6   b  is caught by the terminal hook catching portion  1   c , so that the assist torque to the second rotating body becomes substantially zero. Then, the assist torque to the second rotating body maintains substantially zero in a process in which the rotational phase of the second rotating body with respect to the first rotating body changes from the intermediate phase, which is the lock phase, to the advance side, which is the second rotational phase side, and reaches the most advanced phase, and in a process in which the rotational phase changes from the most advanced phase to the intermediate phase, which is the lock phase. 
     As described above, the second arm projection portion  4   e  is configured to be separated from the outermost periphery of the spiral spring  6  in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the second rotational phase side. Therefore, friction hardly occurs between the second arm projection portion  4   e  and the outermost peripheral portion of the spiral spring  6 . Therefore, it is possible to suppress hysteresis generated between a process, in which the rotational phase of the second rotating body with respect to the first rotating body changes from the intermediate phase that is the lock phase to the advance side that is the second rotational phase side, and a process in which the rotational phase changes from the advance side that is the second rotational phase side to the intermediate phase that is the lock position. 
     Next, a first modification example of the valve timing adjustment device  100  according to the first embodiment will be described with reference to the drawings.  FIG. 6A  is a front view illustrating a holder  10  included in the valve timing adjustment device  100  according to the first modification example.  FIG. 6B  is a cross-sectional view of holder  10  illustrated in  FIG. 6A  taken along line B. As illustrated in  FIGS. 6A and 6B , an unequal pitch spring  11  is installed in a second arm projection portion  10   a  of the holder  10 . 
     More specifically, the second arm  10   b  of the holder  10  has a through hole  10   c , and the second arm projection portion  10   a  is movably held between the inner wall on the outer peripheral side and the inner wall on the rotation axis R side of the through hole  10   c . Further, an unequal pitch spring  11  is installed between the inner wall of the through hole  10   c  on the outer peripheral side and the second arm projection portion  10   a . When the second arm projection portion  10   a  abuts on the outermost peripheral portion of the spiral spring  6  and is pressed toward the outer peripheral side, the unequal pitch spring  11  urges the second arm projection portion  10   a  toward the rotation axis R side. 
       FIG. 7  is a graph illustrating a change in the load applied to the unequal pitch spring  11 , that is, a change in the restoring force by the unequal pitch spring  11  according to a change in the rotational phase of the second rotating body with respect to the first rotating body. Note that, in the first modification example, for the sake of explanation, it is assumed that the second arm projection portion  10   a  is in contact with the outermost peripheral portion of the spiral spring  6  even when the rotational phase of the second rotating body with respect to the first rotating body is on the advance side which is the second rotational phase side. The vertical axis in  FIG. 7  indicates the restoring force by the unequal pitch spring  11 , and the horizontal axis in  FIG. 7  indicates the rotational phase of the second rotating body with respect to the first rotating body. 
     First, in the process in which the rotational phase of the second rotating body with respect to the first rotating body changes from the intermediate phase that is the lock phase to the retard side that is the first rotational phase side, the second arm projection portion  10   a  is pushed toward the outer peripheral side by the spiral spring  6  while moving toward the retard side in a state of being in contact with the outermost peripheral portion of the spiral spring  6 , and moves gradually away from the rotation axis R side. In the process, the unequal pitch spring  11  contracts, and as shown in  FIG. 7 , the force for urging the outermost peripheral portion of the spiral spring  6  toward the rotation axis R via the second arm projection portion  10   a  gradually increases. 
     In addition, in the process in which the rotational phase of the second rotating body with respect to the first rotating body changes from the retard side, which is the first rotational phase side, to the intermediate phase, which is the lock phase, the second arm projection portion  10   a  moves to the advance side in a state of being in contact with the outermost peripheral portion of the spiral spring  6 , and gradually moves closer to the rotation axis R side as the force of being pushed toward the outer peripheral side by the spiral spring  6  is weakened. In the process, the unequal pitch spring  11  extends, and as illustrated in  FIG. 7 , the force for urging the outermost peripheral portion of the spiral spring  6  toward the rotation axis R via the second arm projection portion  10   a  gradually decreases. Then, when the rotational phase of the second rotating body with respect to the first rotating body reaches the intermediate phase which is the lock phase or the advance side which is a second rotational phase, the force becomes substantially zero. 
     As described above, by using the unequal pitch spring  11 , it is possible to suitably implement a configuration in which the second arm projection portion  10   a  urges the outermost peripheral portion of the spiral spring  6  toward the rotation axis R side when the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, and a configuration in which the second arm projection portion  10   a  does not urge the outermost peripheral portion of the spiral spring  6  when the rotational phase is on the second rotational phase side. Therefore, when the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, the second arm projection portion  10   a  abuts on the outermost peripheral portion of the spiral spring, and it is possible to suppress resonance of the spiral spring due to vibration of the engine during operation. On the other hand, when the rotational phase is on the second rotational phase side, friction is less likely to occur between the second arm projection portion  10   a  and the outermost peripheral portion of the spiral spring  6 . 
     In addition, the unequal pitch spring  11  serves as a buffer between the second arm projection portion  10   a  and the outermost peripheral portion of the spiral spring  6 , and friction is less likely to occur between the second arm projection portion  10   a  and the outermost peripheral portion of the spiral spring  6 . Therefore, the hysteresis described above can be suppressed. In addition, since the second arm projection portion  10   a  is movable with respect to the second arm  4   c  by the unequal pitch spring  11 , the degree of freedom in designing the arrangement of the second arm projection portion  10   a  and the second arm  4   c  or the degree of freedom in designing the curvature wound around the main body portion  4   a  on the outermost periphery of the spiral spring  6  can be increased. 
     Note that each of the above effects can be implemented by using another type of spring such as an equal pitch spring, for example, as the spring installed in the second arm projection portion  10   a  instead of the unequal pitch spring  11 . On the other hand, as in the first modification example, the following effects are obtained by using the unequal pitch spring  11  as the spring installed in the second arm projection portion  10   a . That is, since the unequal pitch spring  11  has a non-linear relationship between the load and the deflection, in the graph of  FIG. 7 , the inclination when the rotational phase of the second rotating body with respect to the first rotating body is on the retard side which is the first rotational phase side is larger than the inclination when the rotational phase is on the advance side which is the second rotational phase side. That is, the spring constant of the unequal pitch spring  11  in the contracted state is larger than the spring constant in the state where substantially no load is applied. As a result, in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, the force by which the second arm projection portion  10   a  urges the outermost peripheral portion of the spiral spring  6  toward the rotation axis R side can be increased, and in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the second rotational phase side, the force by which the second arm projection portion  10   a  urges the outermost peripheral portion of the spiral spring  6  toward the rotation axis R side can be decreased. 
     Next, a second modification example of the valve timing adjustment device  100  according to the first embodiment will be described with reference to the drawings.  FIG. 8A  is a front view illustrating a plate  12  included in a valve timing adjustment device  100  according to the second modification example.  FIG. 8B  is a cross-sectional view of the plate  12  illustrated in  FIG. 8A  taken along line C. As illustrated in  FIGS. 8A and 8B , an unequal pitch spring  13  is installed in a first plate projection portion  12   a.    
     More specifically, the plate  12  has a recess portion  12   b , and the first plate projection portion  12   a  is movably held between the inner wall on the outer peripheral side and the inner wall on the rotation axis R side of the recess portion  12   b . Moreover, the unequal pitch spring  13  is installed between the inner wall of the recess portion  12   b  on the outer peripheral side and the first plate projection portion  12   a . When the first plate projection portion  12   a  abuts on the outermost peripheral portion of the spiral spring  6  and is pressed toward the outer peripheral side, the unequal pitch spring  13  urges the first plate projection portion  12   a  toward the rotation axis R side. 
     In the second modification example, for the sake of explanation, it is assumed that the first plate projection portion  12   a  is in contact with the outermost peripheral portion of the spiral spring  6  even when the rotational phase of the second rotating body with respect to the first rotating body is on the retard side which is the first rotational phase side. As described above, when the rotational phase of the second rotating body with respect to the first rotating body is on the advance side which is the second rotational phase side, the second arm projection portion  4   e  is completely separated from the outermost periphery of the spiral spring  6 . As a result, the restoring force due to the outermost periphery of the spiral spring  6  is directly applied to the first plate projection portion  12   a , and when the first plate projection portion  12   a  is pushed toward the outer peripheral side, the unequal pitch spring  13  contracts, and a force urging the outermost peripheral portion of the spiral spring  6  toward the rotation axis R side via the first plate projection portion  12   a  is generated. 
     Further, as described above, in the process in which the rotational phase of the second rotating body with respect to the first rotating body changes from the intermediate phase which is the lock phase to the retard side which is the first rotational phase side, the second arm projection portion  4   e  moves so as to gradually approach the spiral spring  6  side while moving toward the retard side along the locus T in a state of abutting on the outermost peripheral portion of the spiral spring  6 , and urges the outermost peripheral portion of the spiral spring  6  toward the rotation axis R side. As a result, when the outermost peripheral portion of the spiral spring  6  is deformed and the force with which the portion pushes the first plate projection portion  12   a  toward the outer peripheral side is weakened, the unequal pitch spring  13  extends, and the force with which the outermost peripheral portion of the spiral spring  6  is urged toward the rotation axis R side via the first plate projection portion  12   a  becomes substantially 0. 
     As described above, by using the unequal pitch spring  13 , it is possible to suitably implement a configuration in which the first plate projection portion  12   a  does not urge the outermost peripheral portion of the spiral spring  6  when the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, and a configuration in which the first plate projection portion  12   a  urges the outermost peripheral portion of the spiral spring  6  toward the rotation axis R side when the rotational phase is on the second rotational phase side. Therefore, when the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, friction is less likely to occur between the first plate projection portion  12   a  and the outermost peripheral portion of the spiral spring  6 . On the other hand, when the rotational phase is on the second rotational phase side, the first plate projection portion  12   a  abuts on the outermost peripheral portion of the spiral spring, and it is possible to suppress resonance of the spiral spring due to vibration of the engine during operation. 
     Moreover, the unequal pitch spring  13  serves as a buffer between the first plate projection portion  12   a  and the outermost peripheral portion of the spiral spring  6 , and friction is less likely to occur between the first plate projection portion  12   a  and the outermost peripheral portion of the spiral spring  6 . In addition, since the first plate projection portion  12   a  is movable with respect to the plate  1  by the unequal pitch spring  13 , the degree of freedom in designing the arrangement of the first plate projection portion  12   a  or the degree of freedom in designing the curvature wound around the main body portion  4   a  on the outermost periphery of the spiral spring  6  can be increased. 
     Note that each of the above effects can be implemented by using another type of spring such as an equal pitch spring, for example, as the spring installed in the first plate projection portion  12   a  instead of the unequal pitch spring  13 . On the other hand, as in the second modification example, the following effects are obtained by using the unequal pitch spring  13  as the spring installed in the first plate projection portion  12   a . That is, the spring constant of the unequal pitch spring  13  in the contracted state is larger than the spring constant in the state where substantially no load is applied. As a result, in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, the force by which the first plate projection portion  12   a  urges the outermost peripheral portion of the spiral spring  6  toward the rotation axis R side can be reduced, and in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the second rotational phase side, the force by which the first plate projection portion  12   a  urges the outermost peripheral portion of the spiral spring  6  toward the rotation axis R side can be increased. Accordingly, in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, friction is less likely to occur between the first plate projection portion  12   a  and the outermost peripheral portion of the spiral spring  6 , and in a case where the rotational phase is on the second rotational phase side, the first plate projection portion  12   a  can suppress resonance of the spiral spring due to vibration of the engine during operation. 
     Next, a third modification example of the valve timing adjustment device  100  according to the first embodiment will be described with reference to the drawings.  FIG. 9A  is a front view illustrating the configuration of a valve timing adjustment device  100  including a spiral spring  14  instead of the spiral spring  6 .  FIG. 9B  is a diagram illustrating only a terminal hook portion  14   a , a terminal hook catching portion  1   c , and a first arm projection portion  4   d  of the spiral spring  14  in the valve timing adjustment device  100  illustrated in  FIG. 9A . Note that the rotational phase of the second rotating body with respect to the first rotating body in the valve timing adjustment device  100  illustrated in  FIG. 9A  is an intermediate phase which is a lock phase. Moreover, in  FIGS. 9A and 9B , for the sake of explanation, the terminal hook catching portion  1   c  having a cylindrical shape is shown unlike the shape of the terminal hook catching portion  1   c  in  FIG. 1  and the like, but the function is not changed. 
     As illustrated in  FIGS. 9A and 9B , the terminal hook portion  14   a  of the spiral spring  14  according to the third modification example is formed by bending the outer peripheral side end portion of the spiral spring  14  toward the outer peripheral side by an angle larger than 90 degrees. In other words, an angle formed by the first portion  14   b  extending from the bent portion of the terminal hook portion  14   a  to the inner peripheral side end portion side and the second portion  14   c  extending to the outer peripheral side is an acute angle. 
       FIG. 10A  illustrates the configuration of the valve timing adjustment device  100  illustrated in  FIG. 9A  in which the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side.  FIG. 10B  is a diagram illustrating only the terminal hook portion  14   a , the terminal hook catching portion  1   c , and the first arm projection portion  4   d  of the spiral spring  14  in the valve timing adjustment device  100  illustrated in  FIG. 10A . As illustrated in  FIGS. 9A and 9B  and  FIGS. 10A and 10B , the first arm projection portion  4   d  is caught by the terminal hook portion  14   a  of the spiral spring  14  in the process of changing the rotational phase of the second rotating body with respect to the first rotating body from the intermediate phase, which is the lock phase, to the retard side, which is the first rotational phase side. At this time, since the normal direction of the surface of the second portion  14   c  of the terminal hook portion  14   a  in contact with the first arm projection portion  4   d  is different from the moving direction of the first arm projection portion  4   d , the second portion  14   c  of the terminal hook portion  14   a  is pushed toward the retard side by the first arm projection portion  4   d  and slides toward the outer peripheral side with respect to the first arm projection portion  4   d  at the same time. Then, the outermost peripheral portion of the spiral spring  14  is deformed by being pulled in the direction in which the terminal hook portion  14   a  slides toward the outer peripheral side, and is separated from the first plate projection portion  1   d . This eliminates friction between the outermost peripheral portion of the spiral spring  14  and the first plate projection portion  1   d.    
     The surface of the second portion  14   c  of the terminal hook portion  14   a  in contact with the first arm projection portion  4   d  and the surface of the first arm projection portion  4   d  in contact with the second portion  14   c  are preferably configured to be easily slidable against each other so that the second portion  14   c  of the terminal hook portion  14   a  slides toward the outer peripheral side with respect to the first arm projection portion  4   d . For example, the surface of the second portion  14   c  of the terminal hook portion  14   a  in contact with the first arm projection portion  4   d  and the surface of the first arm projection portion  4   d  in contact with the second portion  14   c  are configured to be in point contact with each other. 
     Furthermore, as illustrated in  FIGS. 9A and 9B  and  FIGS. 10A and 10B , in the terminal hook portion  14   a , when the rotational phase of the second rotating body with respect to the first rotating body is the intermediate phase that is the lock phase, the end portion of the second portion  14   c  may be further bent so as to partially surround the terminal hook catching portion  1   c  and the first arm projection portion  4   d . Accordingly, the terminal hook portion  14   a  is hardly detached from the terminal hook catching portion  1   c  or the first arm projection portion  4   d.    
     Note that, in the first embodiment, the lock phase in the valve timing adjustment device  100  is the intermediate phase between the advanced phase and the retarded phase, but the lock phase is not limited thereto. For example, the lock phase in the valve timing adjustment device  100  may be an advance side phase or a retard side phase. 
     Moreover, in the first embodiment, the example in which the first rotational phase side in the valve timing adjustment device  100  is the retard side and the second rotational phase side is the advance side has been described. Then, the configuration has been described in which the rotational phase of the second rotating body with respect to the first rotating body is on the retard side, the first arm projection portion  4   d  is caught by the terminal hook portion  6   b  of the spiral spring  6  and urged to the lock phase side by the spiral spring  6 , and the second arm projection portion  4   e  abuts on the outermost peripheral portion of the spiral spring  6 . 
     However, the first arm projection portion  4   d  and the second arm projection portion  4   e  are not limited to the above configuration. For example, the first rotational phase side in the valve timing adjustment device  100  may be the advance side, and the second rotational phase side may be the retard side. Then, in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the advance side, the first arm projection portion  4   d  may be caught by the terminal hook portion  6   b  of the spiral spring  6  and urged to the lock phase side by the spiral spring  6 , and the second arm projection portion  4   e  may abut on the outermost peripheral portion of the spiral spring  6 . In addition, the second arm projection portion  4   e  may be configured to be separated from the outermost periphery of the spiral spring  6  when the rotational phase is on the retard side. Further, when the rotational phase is on the retard side, the first plate projection portion  1   d  may abut on the outermost peripheral portion of the spiral spring  6 . 
     As described above, the valve timing adjustment device  100  according to the first embodiment is the valve timing adjustment device  100 , including: a first rotating body that rotates synchronously with a crankshaft; and a second rotating body that rotates synchronously with a camshaft, in which the first rotating body includes a plate  1  having an opening portion  1   a  around a rotation axis R, the second rotating body includes: a main body portion  4   a  that passes through the opening portion  1   a  of the plate  1  and is disposed around the rotation axis R; and a holder  4  having a first arm  4   b  and a second arm  4   c  that each extends to an outer peripheral side from an end portion of a portion of the main body portion  4   a  projecting from the front surface of the plate  1 , a spiral spring  6  is installed between the front surface of the plate  1  and the first arm  4   b  and the second arm  4   c , in which the spiral spring  6  is wound around the main body portion  4   a , an inner peripheral side end portion is held by the plate  1 , and a terminal hook portion  6   b  is formed by bending an outer peripheral side end portion toward an outer peripheral side, a first arm projection portion  4   d  is caught by the terminal hook portion  6   b  of the spiral spring  6 , is urged toward a lock phase side by the spiral spring  6  and is installed on a face opposite to the front surface of the plate  1  in the first arm  4   b  in a case where a rotational phase of the second rotating body with respect to the first rotating body is on a first rotational phase side, and a second arm projection portion  4   e  abuts on an outermost peripheral portion of the spiral spring  6  and is installed on a face opposite to the front surface of the plate  1  in the second arm  4   c  in a case where the rotational phase is on the first rotational phase side. 
     According to the above configuration, in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, the second rotating body is urged toward the lock phase side by the spiral spring  6  via the first arm projection portion  4   d , and the second arm projection portion  4   e  abuts on the outermost peripheral portion of the spiral spring. As a result, the vibration of the engine transmitted to the spiral spring  6  through the terminal hook catching portion  1   c  is transmitted from the portion in contact with the terminal hook catching portion  1   c  to the portion in contact with the second arm projection portion  4   e  on the outermost periphery of the spiral spring  6 , but is hardly transmitted beyond the latter portion. Therefore, resonance of the spiral spring due to vibration of the engine during operation can be suppressed. 
     Furthermore, according to the above configuration, in the process in which the rotational phase of the second rotating body with respect to the first rotating body changes from the lock phase to the first rotational phase side, the second arm projection portion  4   e  and the outermost peripheral portion of the spiral spring  6  both move to the first rotational phase side in a state of being in contact with each other. In addition, in the process in which the rotational phase of the second rotating body with respect to the first rotating body changes from the first rotational phase side to the lock phase, the second arm projection portion  4   e  and the outermost peripheral portion of the spiral spring  6  are separated from each other while both moving to the lock phase side. 
     Thus, friction hardly occurs between the second arm projection portion  4   e  and the outermost peripheral portion of the spiral spring  6 , so that it is possible to suppress hysteresis generated between a process in which the rotational phase of the second rotating body with respect to the first rotating body changes from the lock position to the first rotational phase side and a process in which the rotational phase changes from the first rotational phase side to the lock position. 
     Moreover, the second arm projection portion  4   e  in the valve timing adjustment device  100  according to the first embodiment is configured to be separated from the outermost periphery of the spiral spring  6  in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the second rotational phase side. 
     Therefore, according to the above configuration, in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the second rotational phase side, friction is less likely to occur between the second arm projection portion  4   e  and the outermost peripheral portion of the spiral spring  6 . 
     Furthermore, on the front surface of the plate  1  in the valve timing adjustment device  100  according to the first embodiment, the first plate projection portion  1   d  in contact with the outermost peripheral portion of the spiral spring  6  is installed in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the second rotational phase side. 
     According to the above configuration, in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the second rotational phase side, the outermost periphery of the spiral spring  6  abuts on the first plate projection portion  1   d , thereby the vibration of the engine transmitted to the spiral spring  6  via the terminal hook catching portion  1   c  is transmitted from the portion in contact with the terminal hook catching portion  1   c  at the outermost periphery of the spiral spring  6  to the portion in contact with the first plate projection portion  1   d , but is hardly transmitted beyond the latter portion. Therefore, resonance of the spiral spring due to vibration of the engine during operation can be further suppressed. 
     Furthermore, on the front surface of the plate  1  in the valve timing adjustment device  100  according to the first embodiment, the second plate projection portion  1   e  in contact with the innermost peripheral portion of the spiral spring  6  is installed. 
     According to the above configuration, when the spiral spring  6  is wound around the main body portion  4   a  of the holder  4 , the second plate projection portion  1   e  serves as a guide. Furthermore, the vibration of the engine transmitted to the spiral spring  6  through the starting end hook catching portion  1   b  is transmitted from the portion in contact with the starting end hook catching portion  1   b  to the portion in contact with the second plate projection portion  1   e  on the innermost periphery of the spiral spring  6 , but is hardly transmitted beyond the latter portion. 
     In a case where the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, the second arm projection portion  4   e  in the valve timing adjustment device  100  according to the first embodiment is located on the opposite side to the second plate projection portion  1   e  side with reference to the rotation axis R. 
     According to the above configuration, the second arm projection portion  4   e  becomes an obstacle, and the spiral spring  6  is less likely to move to the side opposite to the second plate projection portion  1   e  side with reference to the rotation axis R, the portion abutting on the second plate projection portion  1   e  and the portion on the outer peripheral side corresponding to the portion are less likely to come into contact with each other, and friction is less likely to occur. 
     On the front surface of the plate  1  in the valve timing adjustment device  100  according to the first embodiment, the second plate projection portion  1   e  in contact with the innermost peripheral portion of the spiral spring  6  is installed, and on the front surface of the plate  1  opposite to the second plate projection portion  1   e  with reference to the rotation axis R, the first plate projection portion  1   d  in contact with the outermost peripheral portion of the spiral spring  6  is installed when the rotational phase is on the second rotational phase side. 
     According to the above configuration, the first plate projection portion  1   d  becomes an obstacle, the spiral spring  6  is less likely to move to the side opposite to the second plate projection portion  1   e  side with respect to the rotation axis R, and the portion abutting on the second plate projection portion  1   e  and the portion on the outer peripheral side corresponding to the portion are less likely to come into contact with each other, so that friction is less likely to occur. 
     Moreover, the second arm projection portion  10   a  of the valve timing adjustment device  100  according to the first embodiment is provided with a spring that urges the second arm projection portion  10   a  toward the rotation axis R in a case where the second arm projection portion  10   a  abuts on the outermost peripheral portion of the spiral spring  6  and is pushed toward the outer peripheral side. 
     According to the above configuration, it is possible to suitably implement a configuration in which the second arm projection portion  10   a  urges the outermost peripheral portion of the spiral spring  6  toward the rotation axis R side when the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, and a configuration in which the second arm projection portion  10   a  does not urge the outermost peripheral portion of the spiral spring  6  when the rotational phase is on the second rotational phase side. In short, when the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, the second arm projection portion  10   a  abuts on the outermost peripheral portion of the spiral spring, and it is possible to suppress resonance of the spiral spring due to vibration of the engine during operation. On the other hand, when the rotational phase is on the second rotational phase side, friction is less likely to occur between the second arm projection portion  10   a  and the outermost peripheral portion of the spiral spring  6 . 
     In addition, the spring installed in the second arm projection portion  10   a  in the valve timing adjustment device  100  according to the first embodiment is the unequal pitch spring  11 . 
     According to above configuration, in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, the force by which the second arm projection portion  10   a  urges the outermost peripheral portion of the spiral spring  6  toward the rotation axis R side can be increased, and in a case where the rotational phase is on the second rotational phase side, the force by which the second arm projection portion  10   a  urges the outermost peripheral portion of the spiral spring  6  toward the rotation axis R side can be decreased. Therefore, in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, the second arm projection portion  10   a  can suppress resonance of the spiral spring due to vibration of the engine during operation, and in a case where the rotational phase is on the second rotational phase side, friction is less likely to occur between the second arm projection portion  10   a  and the outermost peripheral portion of the spiral spring  6 . 
     Moreover, the first plate projection portion  12   a  of the valve timing adjustment device  100  according to the first embodiment is provided with a spring that urges the first plate projection portion  12   a  toward the rotation axis R side when the first plate projection portion  12   a  abuts on the outermost peripheral portion of the spiral spring  6  and is pushed toward the outer peripheral side. 
     According to the above configuration, it is possible to suitably implement a configuration in which the first plate projection portion  12   a  does not urge the outermost peripheral portion of the spiral spring  6  when the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, and a configuration in which the first plate projection portion  12   a  urges the outermost peripheral portion of the spiral spring  6  toward the rotation axis R side in a case where the rotational phase is on the second rotational phase side. Therefore, when the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, friction is less likely to occur between the first plate projection portion  12   a  and the outermost peripheral portion of the spiral spring  6 . On the other hand, when the rotational phase is on the second rotational phase side, the first plate projection portion  12   a  abuts on the outermost peripheral portion of the spiral spring, and it is possible to suppress resonance of the spiral spring due to vibration of the engine during operation. 
     Furthermore, in the valve timing adjustment device  100  according to the first embodiment, the spring installed in the first plate projection portion  12   a  is the unequal pitch spring  13 . 
     According to above configuration, in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, the force by which the first plate projection portion  12   a  urges the outermost peripheral portion of the spiral spring  6  toward the rotation axis R side can be decreased, and in a case where the rotational phase is on the second rotational phase side, the force by which the first plate projection portion  12   a  urges the outermost peripheral portion of the spiral spring  6  toward the rotation axis R side can be increased. Accordingly, in a case where the rotational phase of the second rotating body with respect to the first rotating body is on the first rotational phase side, friction is less likely to occur between the first plate projection portion  12   a  and the outermost peripheral portion of the spiral spring  6 , and in a case where the rotational phase is on the second rotational phase side, the first plate projection portion  12   a  can suppress resonance of the spiral spring due to vibration of the engine during operation. 
     In addition, the outer peripheral side end portion of the terminal hook portion  14   a  of the spiral spring  14  in the valve timing adjustment device  100  according to the first embodiment is bent by an angle larger than 90 degrees toward the outer peripheral side. 
     According to the above configuration, the terminal hook portion  14   a  is pushed toward the first rotational phase side by the first arm projection portion  4   d , and at the same time, slides toward the outer peripheral side with respect to the first arm projection portion  4   d . As a result, the outermost peripheral portion of the spiral spring  14  is deformed by being pulled in the direction in which the terminal hook portion  6   b  slides toward the outer peripheral side, and is separated from first plate projection portion  1   d . This eliminates friction between the outermost peripheral portion of spiral spring  6  and first plate projection portion  1   d.    
     Note that, in the present invention, any component of the embodiment can be modified or any component of the embodiment can be omitted within the scope of the invention. 
     INDUSTRIAL APPLICABILITY 
     The valve timing adjustment device according to the present invention can suppress resonance of the spiral spring due to vibration of the engine during operation, and thus can be used for the valve timing adjustment device. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 : plate,  1   a : opening portion,  1   b : starting end hook catching portion,  1   c : terminal hook catching portion,  1   d : first plate projection portion,  1   e : second plate projection portion,  2 : case,  2   a : chain sprocket portion,  3 : rotor,  4 : holder,  4   a : main body portion,  4   b : first arm,  4   c : second arm,  4   d : first arm projection portion,  4   e : second arm projection portion,  5 : center bolt,  6 : spiral spring,  6   a : starting end hook portion,  6   b : terminal hook portion,  10 : holder,  10   a : second arm projection portion,  10   b : second arm,  10   c : through hole,  11 : unequal pitch spring,  12 : plate,  12   a : first plate projection portion,  12   b : recess portion,  13 : unequal pitch spring,  14 : spiral spring,  14   a : terminal hook portion,  14   b : first portion,  14   c : second portion,  100 : valve timing adjustment device