Patent Publication Number: US-9429976-B2

Title: Vehicle operation pedal device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national phase application of International Application No. PCT/JP2012/067236, filed Jul. 5, 2012, and claims the priority of Japanese Application No. 2011-288790, filed Dec. 28, 2011, the content of both of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The invention relates generally to a vehicle operation pedal apparatus, and more specifically to a technique for preventing abnormal noise from being generated by a return spring held under tension in order to return an operation pedal in the vehicle operation pedal apparatus. 
     BACKGROUND ART 
     As one kind of vehicle operation pedal apparatus such as a brake pedal or a clutch pedal, there has been known an apparatus including (a) an operation pedal supported by a pedal support member so as to be pivotable about one axis, and (b) a return spring having one end portion engaged with a bracket plate member disposed on the operation pedal and the other end portion engaged with a position fixing member, in which (c) the operation pedal is returned to an original position in accordance with an urging force of the return spring upon cancellation of a depressing operation of the operation pedal. Such an apparatus is described in, for example, Patent Document 1. 
     RELATED ART DOCUMENT 
     Patent Document 
     Patent Document 1: WO2010/073347A1 
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     In the above-described vehicle pedal apparatus, abnormal noise may be generated, in response to a pivoting operation of the operation pedal, from the return spring held under tension between the bracket plate member disposed on the operation pedal and the position fixing member, the return spring being disposed to urge the operation pedal toward the original position. 
     The invention is made in the light of the above-described circumstances, and an object of the invention is to provide a vehicle operation pedal apparatus configured to prevent abnormal noise from being generated by a return spring during a pivoting operation of an operation pedal. 
     Means for Solving the Problem 
     The present inventor has repeated various analyses and investigations in consideration of the above-described circumstances, and has eventually reached a fact described below. That is, in the conventional vehicle operation pedal apparatus described in, for example, Patent Document 1, as illustrated in  FIG. 9 , one end portion of a return spring  100  has an engagement hook  100   a  formed by bending an end portion of a wire rod constituting the return spring  100 , an engagement hole  102   a  into which the engagement hook  100   a  is hooked is formed in a bracket plate member  102  disposed on the operation pedal so as to pass through the bracket plate member  102 , and the engagement hole  102   a  is formed so as to pass through the bracket plate member  102  in a direction perpendicular to one surface  102   b  and the other surface  102   c  of the bracket plate member  102 . Further, one of a pair of edges ED 1 , ED 2  that are ridgelines between an inner wall surface of the engagement hole  102   a  and the one surface  102   b  and the other surface  102   c  of the bracket plate member  102  is brought into contact with the engagement hook  100   a.    
     In this type of vehicle operation pedal apparatus, states of the return spring  100  from when the operation pedal is depressed and a pedal stroke becomes maximum until when the depression of the operation pedal is cancelled and the pedal stroke becomes zero are as sequentially illustrated in  FIG. 9 . As illustrated in  FIG. 9 , when the pedal stroke is maximum, an angle θ between the direction of the one surface  102   b  of the bracket plate member  102  and a line L of action of the return spring  100 , which passes through a contact point P 1  at which the engagement hook  100   a  is in contact with the edge ED 1 , that is, a contact angle θ takes a positive value. Further, when the pedal stroke is minimum, that is, zero, a contact angle θ between the direction of the other surface  102   c  of the bracket plate member  102  and the line L of action of the return spring  100 , which passes through a contact point P 2  at which the engagement hook  100   a  is in contact with the edge ED 2 , takes a negative value. With regard to the contact angle θ, the above-mentioned positive value indicates that the line L of action of the return spring  100  tilts in the counterclockwise direction about the contact point P 1 , P 2  with respect to the one surface  102   b  or the other surface  102   c  of the bracket plate member  102 , and the above-mentioned negative value indicates that the line of action tilts in the clockwise direction about the contact point P 1 , P 2 . Further, the line L of action is a line indicating the direction in which the urging force of the return spring  100  acts. 
     In the conventional vehicle operation pedal apparatus configured as described above, as illustrated in  FIG. 9  and  FIG. 10 , in the returning direction of the above operation pedal, a friction force which has acted between the edge ED 1  of the engagement hole  102   a  formed in the bracket plate member  102  and the hook  100   a  of the return spring  100  is reduced as the contact angle θ decreases, and slip is generated at the hook  100   a  that is in contact with the edge ED 1  due to a reaction force of the return spring  100 . Subsequently, the contact angle θ is inverted from a positive value to a negative value, and the hook  100   a  may be brought into contact with the edge ED 2 . As described above, in the course of a pivoting operation of the operation pedal, discontinuous slip is generated at the hook  100   a  that is in contact with the edge ED 1 , so that contact noise may be generated by abrupt slip, or the hook  100   a  may be dragged along the edge ED 1  and vibrate. Then, there has been found the fact that the return spring  100  excited by the vibration resonates at a vibration frequency close to a natural vibration frequency thereof, so that abnormal noise is generated from the return spring  100 . The invention is made on the basis of this finding. 
     That is, the invention provides a vehicle operation pedal apparatus comprising (a) an operation pedal supported by a pedal support member so as to be pivotable about one axis, and (b) a return spring having one end portion engaged with a bracket plate member disposed on the operation pedal and the other end portion engaged with a position fixing member, wherein (c) the operation pedal is returned by pivoting in accordance with an urging force of the return spring upon cancellation of a depressing operation of the operation pedal, the vehicle operation pedal apparatus characterized in that: (d) an engagement hook is formed in the one end portion of the return spring by bending an end portion of a wire rod that constitutes the return spring; (e) an engagement hole or cutout into which the engagement hook is hooked is formed in the bracket plate member disposed on the operation pedal so as to pass through the bracket plate member; and (f) a surface direction of a portion of the bracket plate member, in which the engagement hole or cutout is formed, is set such that a contact point at which the engagement hook contacts one of a pair of edges that are ridgelines between an inner wall surface of the engagement hole or cutout and one surface and the other surface of the bracket plate member is a relative pivot point of the return spring that pivots relative to the operation pedal in accordance with a pivoting operation of the operation pedal in an entire operation angle range of the operation pedal. 
     Effect of the Invention 
     In the vehicle operation pedal apparatus according to the invention, the surface direction of the portion of the bracket plate member, in which the engagement hole or cutout is formed, is set such that the contact point at which the engagement hook contacts the one edge in the pair of the edges, which are the ridgelines between the inner wall surface of the engagement hole or cutout and the one surface and the other surface of the bracket plate member, is the relative pivot point of the return spring that pivots relative to the operation pedal in accordance with the pivoting operation of the operation pedal in the entire operation angle range of the operation pedal. Thus, during the pivoting operation of the operation pedal, the contact point at which the engagement hook of the return spring contacts the bracket plate member does not shift from the one edge to the other edge in the pair of the edges in the engagement hole or cutout, and hence discontinuous slip is not generated between the engagement hook and the bracket plate member. Thus, it is possible to reliably prevent generation of contact noise that is generated due to abrupt slip, or generation of abnormal noise from the return spring. 
     Preferably, the engagement hole or cutout is formed so as to pass through the bracket plate member in a direction perpendicular to the one surface of the bracket plate member; and an angle between the surface direction of the portion of the bracket plate member, in which the engagement hole or cutout is formed, and a line of action of the return spring, which passes through the contact point, takes a positive value in the entire operation angle range of the operation pedal, or takes a negative value in the entire operation angle range of the operation pedal. Thus, the angle does not shift from one angle to the other angle, which has a positive value or a negative value across zero, and the contact point is maintained. Therefore, an angle change of the line of action of the return spring along with discontinuous slip of the engagement hook is prevented from being inverted from a positive value to a negative value or from a negative value to a positive value, and thus generation of abnormal noise from the return spring during the pivoting operation of the operation pedal is reliably prevented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of a brake pedal apparatus (vehicle operation pedal apparatus), to which the invention is applied. 
         FIG. 2  is a view of a return spring held under tension in the brake pedal apparatus of  FIG. 1 . 
         FIG. 3  illustrates views sequentially illustrating the state of the return spring when the operation pedal is depressed so that the pedal stroke becomes maximum, and the state of the return spring when the depression of the operation pedal is cancelled so that the pedal stroke becomes zero, in the brake pedal apparatus of  FIG. 1 . 
         FIG. 4  is a diagram illustrating a movement state of the return spring, which changes in accordance with the depressing operation of the operation pedal in the brake pedal apparatus of  FIG. 1 . 
         FIG. 5  is a view of an influence of variation of an attachment position of the bracket plate member fixed with the operation pedal, and variation of a position and dimension of the engagement hole of the bracket plate member, on the contact angle. 
         FIG. 6  is a view illustrating a method of tuning the contact angle without exerting the influence on a pedal operation feeling in the case where the dimensions and the attachment positions of the components of the brake pedal apparatus of  FIG. 1 , such as the operation pedal, the bracket plate member, and the position fixing member vary. 
         FIG. 7  is a front view of a brake pedal apparatus that is another embodiment of the invention, the view corresponding to  FIG. 1 . 
         FIG. 8  is a view of a return spring held under tension in the brake pedal apparatus of  FIG. 7 . 
         FIG. 9  illustrates view sequentially illustrating the state of the return spring from when the operation pedal is depressed and the pedal stroke becomes maximum until when the depression of the operation pedal is cancelled and the pedal stroke becomes zero, in the conventional brake pedal apparatus. 
         FIG. 10  is a diagram explaining the state where, in the brake pedal apparatus of  FIG. 9 , a contact angle between the direction of one surface of a bracket plate member and a line of action of the return spring changes in association with a depressing operation of the operation pedal, and a hook slips to hit an upper end-side inner peripheral edge. 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
     Hereinafter, an embodiment of the invention will be described in detail with reference to the drawings. Note that, in the following embodiments, the drawings will be simplified or deformed as needed to facilitate understanding of the drawings, and the dimensional ratio, the shape and the like of each portion will not be always drawn accurately. 
     Embodiment 1 
       FIG. 1  is a front view of a brake pedal apparatus (vehicle operation pedal apparatus)  10  for a service brake, to which the invention is applied. The brake pedal apparatus  10  includes: a position fixing pedal support (pedal support member)  11  fixedly fitted to a vehicle body; an elongate operation pedal  14  supported by the pedal support  11  so as to be pivotable about an axis (one axis) O 1  of a horizontal first support shaft  12 ; an elongate pivot member  18  supported by the pedal support  11  so as to be pivotable about an axis O 2  of a second support shaft  16 , the axis O 2  being parallel to the axis O 1 ; and a pair of connection links  20   a ,  20   b  provided between the operation pedal  14  and the pivot member  18  such that the operation pedal  14  and the pivot member  18  are interposed between the connection links  20   a ,  20   b  disposed on both sides (front and back sides of  FIG. 1 ) of the operation pedal  14  and the pivot member  18 , thereby connecting the operation pedal  14  and the pivot member  18  to each other.  FIG. 1  is a view in which a front-side side plate of the pedal support  11  is partially cut out so that portions connected by the connection links  20   a ,  20   b  are visible. 
     When a pedal sheet  24  disposed at a lower end portion of the operation pedal  14  is depressed by a driver, the operation pedal  14  is operated to pivot clockwise about the first support shaft  12  in  FIG. 1 , thereby pivoting the pivot member  18  counterclockwise about the second support shaft  16  via the connection links  20   a ,  20   b  connected to an upper end portion of the operation pedal  14 . A pushrod  28  is connected via a clevis  30  to an upper end portion of the pivot member  18  so as to be pivotable relative to the pivot member  18  about an axis of a connection pin  26  that is substantially parallel to the second support shaft  16 . With the pivot motion of the pivot member  18 , the pushrod  28  is mechanically pushed leftward in  FIG. 1 , so that a brake hydraulic pressure corresponding to a depressing operation force applied to the operation pedal  14  is generated. The pushrod  28  is urged to project rearward from a brake master cylinder (not illustrated) or a brake booster disposed on the brake master cylinder, and a return spring  32 , which is a coil spring, is held under tension between the operation pedal  14  and the pedal support  11 . Thus, when the depressing operation of the pedal sheet  24  is cancelled, the pivot member  18  is returned by pivoting clockwise about the axis O 2  of the second support shaft  16  by an urging force of the pushrod  28  and the return spring  32 , and the operation pedal  14  is returned by pivoting counterclockwise about the axis O 1  of the first support shaft  12  to be returned to an original position illustrated in  FIG. 1 . 
     As illustrated in  FIG. 1  and  FIG. 2 , the return spring  32  is obtained by winding one spring wire rod having, for example, a circular cross-section into a coil form, and opposite end portions of the wire rod respectively have a pair of engagement hooks  32   a ,  32   b  formed by bending the end portions of the wire rod into a circular-arc shape. A bracket plate member  34  formed by pressing, for example, a flat metal plate into an L-shape is fixed integrally with an intermediate portion of the operation pedal  14  by spot welding or the like, and a circular engagement hole (hole for engagement)  34   b  into which the engagement hook  32   a  is hooked is formed in a flat first plate portion  34   a  of the bracket plate member  34 , the first plate portion  34   a  being located on the return spring  32  side, so as to pass through the first plate portion  34   a  in a direction perpendicular to the plate surface. A cushion material that is brought into contact with a position fixing stopper (not illustrated) during returning pivot motion of the operation pedal  14  may be fixed to a flat second plate portion  34   c  which is located on the opposite side of the bracket plate member  34  from the first plate portion  34   a . Further, the pedal support  11  is provided with a spring engagement member  36 , which is a position fixing member fixed integrally with the pedal support  11  by, for example, spot welding, and the spring engagement member  36  is provided integrally with a flat engagement plate portion  36   a  extended toward the return spring  32 , which is formed by bending a flat metal plate by press working. A circular engagement hole  36   b  into which the engagement hook  32   b  is hooked is formed in the engagement plate portion  36   a  so as to pass through the engagement plate portion  36   a.    
     As illustrated in  FIG. 2  in detail, the first plate portion  34   a  is in the form of a flat plate having one surface  34   d  on the first support shaft  12  side and the other surface  34   e  on the pedal sheet  24  side, which are parallel to each other, and the engagement hole  34   b  of the bracket plate member  34  is formed so as to pass through the first plate portion  34   a  in a direction perpendicular to the one surface  34   d  and the other surface  34   e . Further, the engagement plate portion  36   a  of the spring engagement member  36  is in the form of a flat plate having one surface  36   c  on the second support shaft  16  side and the other surface  36   d  on the pedal sheet  24  side, which are parallel to each other, and the engagement hole  36   b  formed in the engagement plate portion  36   a  passes through the engagement plate portion  36   a  in a direction perpendicular to the one surface  36   c  and the other surface  36   d.    
     Out of the pair of engagement hooks  32   a ,  32   b  respectively formed at the opposite ends of the return spring  32 , the engagement hook  32   b  on the spring engagement member  36  side is closed, and attached in advance so that the engagement hook  32   b  is not removed from the engagement hole  36   b  of the spring engagement member  36 . Out of the pair of engagement hooks  32   a ,  32   b , the engagement hook  32   a  on the bracket plate member  34  side is open, and is hooked into the engagement hole  34   b  during the assembly. A portion of the engagement hook  32   b , which includes a contact point A 2  with respect to the engagement hole  36   b , is bent in an arc-shape having a curvature radius larger than that of a portion of the engagement hook  32   a , which includes a contact point A 1  with respect to the engagement hole  34   b . As described above, in the engagement hook  32   b , the portion including the contact point A 2  with respect to the engagement hole  36   b  has the arc-shape having a large curvature radius, and hence the contact point A 2  with respect to the engagement hole  36   b  is not moved in the entire range of pivot motion of the operation pedal  14  and discontinuous slip is not generated between the engagement hook  32   b  and the spring engagement member  36 . 
     The engagement hook  32   a  of the return spring  32  is in contact with one edge E 1  in a pair of edges E 1 , E 2  that are ridgelines between an inner wall surface of the engagement hole  34   b  and the one surface  34   d  and the other surface  34   e  of the first plate portion  34   a  in the bracket plate member  34 . Further, the engagement hook  32   b  is in contact with one edge E 4  in a pair of edges E 3 , E 4  of ridgelines between an inner wall surface of the engagement hole  36   b  and the one surface  36   c  and the other surface  36   d  of the engagement plate portion  36   a  in the spring engagement member  36 . 
     Further, an angle θ 1  between the direction of the other surface  34   e  of the first plate portion  34   a  of the bracket plate member  34  and a line L 1  of action of the return spring  32 , which passes through the contact point A 1  at which the edge E 1  and the engagement hook  32   a  contact each other, that is, a contact angle θ 1  takes a positive value, that is, θ 1 &gt;0°. Note that a positive value of the contact angle θ 1  indicates that the line L 1  of action of the return spring  32  tilts about the contact point A 1  in the counterclockwise direction with respect to the other surface  34   e  of the first plate portion  34   a  of the bracket plate member  34 . Further, the line L 1  of action is a line that connects engagement points of both end portions of the return spring  32  to each other, that is, connects the contact point A 1  to the contact point A 2  at which the edge E 4  and the engagement hook  32   b  contact each other. That is, the line L 1  of action indicates a direction in which an urging force of the return spring  32  acts. Further, in  FIG. 2 , the surface direction of the other surface  34   e  of the first plate portion  34   a  is indicated by a two-dot chain line L 2 . 
       FIG. 3  illustrates views sequentially illustrating the state of the return spring  32  when the operation pedal  14  is depressed so that the pedal stroke becomes maximum, and the state of the return spring  32  when the depression of the operation pedal  14  is cancelled so that the pedal stroke becomes zero.  FIG. 4  is a diagram illustrating a movement state of the return spring  32 , which changes in accordance with the depressing operation of the operation pedal. The return spring  32  pivots relative to the operation pedal  14  in accordance with the operation of the operation pedal  14 , and pivots about the edge E 1  of the engagement hole  34   b  of the bracket plate member  34 . That is, the line L 1  of action of the return spring  32  pivots relative to the operation pedal  14  about the contact point A 1 , which is a pivot point, in accordance with the depression of the operation pedal  14  or the cancellation of the operation. Further, as illustrated in  FIG. 3 , when the pedal stroke is maximum, the contact angle θ 1  takes a positive value, and then the contact angle θ 1  decreases as the pedal stroke decreases. However, even when the pedal stroke is zero, the contact angle θ 1  takes a positive value. That is, the contact angle θ 1  takes a positive value in the entire operation angle range of the operation pedal  14 . Note that, R/Sp described in  FIG. 4  means the return spring  32 . 
     In the state where the pedal stroke is zero at which the operation pedal  14  is at the original position, the contact angle θ 1  needs to be larger than zero (θ 1 &gt;0°) (nominal). However, in consideration of, for example, a dimensional error of each portion of each member of the brake pedal apparatus  10 , the contact angle θ 1  is preferably larger than five degrees (θ 1 &gt;5°), and the contact angle θ 1  is further preferably larger than ten degrees (θ 1 &gt;10°). Thus, the direction of the other surface  34   e  of the first plate portion  34   a  of the bracket plate member  34  is set such that the contact angle θ 1  has the above-described degree. Further, the contact angle θ 1  at the maximum pedal stroke is determined as appropriate in such a range that the engagement hook  32   a  of the return spring  32  is not hooked to the bracket plate member  34 . 
     Next, an influence of variations of dimensions and attachment positions of the components of the brake pedal apparatus  10 , such as the operation pedal  14 , the bracket plate member  34  and the spring engagement member  36 , on the contact angle θ 1  will be described with reference to  FIG. 1  and  FIG. 5 . 
     As illustrated in  FIG. 5 , when a position of the other surface  34   e  of the first plate portion  34   a  is moved in such a direction as to approach the first support shaft  12  in the thickness direction of the first plate portion  34   a  of the bracket plate member  34 , the contact angle θ 1  decreases, whereas when the position of the other surface  34   e  is moved in such a direction as to move away from the first support shaft  12 , the contact angle θ 1  increases. Note that, in  FIG. 1 ,  FIG. 5  and  FIG. 6 , a direction indicated by an arrow with (+) is a direction in which the contact angle θ 1  decreases, that is, a direction in which a possibility that abnormal noise will be generated from the return spring  32  during returning pivot motion of the operation pedal  14  increases. Further, a direction indicated by an arrow with (−) is a direction in which the contact angle θ 1  increases. 
     Further, as illustrated in  FIG. 5 , when a position of an axis C 1  of the engagement hole  34   b  of the first plate portion  34   a  is moved in such a direction as to approach the second plate portion  34   c  in a direction perpendicular to the thickness direction of the first plate portion  34   a , the contact angle θ 1  increases, whereas when the position of the axis C 1  is moved in such a direction as to move away from the second plate portion  34   c , the contact angle θ 1  decreases. Further, when a hole diameter D of the engagement hole  34   b  increases, the contact angle θ 1  increases, whereas when the hole diameter D of the engagement hole  34   b  decreases, the contact angle θ 1  decreases. 
     As illustrated in  FIG. 1 , when a position of the pedal sheet  24  at the maximum pedal stroke is moved in the depression direction in the thickness direction of the pedal sheet  24  of the operation pedal  14 , the contact angle θ 1  increases, whereas when the position of the pedal sheet  24  is moved in the direction opposite to the depression direction, the contact angle θ 1  decreases. Further, when the other surface  36   d  of the engagement plate portion  36   a  is moved in such a direction as to approach the second support shaft  16  in the thickness direction of the engagement plate portion  36   a  of the spring engagement member  36 , the contact angle θ 1  increases, whereas when a position of the side surface  36   d  is moved in such a direction as to move away from the second support shaft  16 , the contact angle θ 1  decreases. 
       FIG. 6  is an explanatory view of a method of tuning the contact angle θ 1  without exerting the influence on a pedal operation feeling in the case where the dimensions and the attachment positions of the operation pedal  14 , the bracket plate member  34 , and the spring engagement member  36  vary as described above. As illustrated in  FIG. 6 , even if such variations occur, it is possible to tune the contact angle θ 1  without exerting the influence on the pedal operation feeling, only by pivoting an attaching angle of the bracket plate member  34  using the contact point A 1  as pivot point. 
     As described above, in the brake pedal apparatus  10  according to the present embodiment, the surface direction of the other surface  34   e  of the first plate portion  34   a  of the bracket plate member  34 , in which the engagement hole  34   b  is formed, is set such that the contact point A 1  at which the engagement hook  32   a  contacts the one edge E 1  in the pair of the edges E 1 , E 2 , which are the ridgelines between the inner wall surface of the engagement hole  34   b  and the other surface  34   e  and the one surface  34   d  of the bracket plate member  34 , is the pivot point of the return spring  32  that pivots in accordance with the operation of the operation pedal  14  in the entire operation angle range of the operation pedal  14 . Thus, during the returning pivot motion of the operation pedal  14 , the contact point A 1  at which the engagement hook  32   a  of the return spring  32  contacts the bracket plate member  34  does not shift from the one edge E 1  to the other edge E 2  in the pair of the edges E 1 , E 2  in the engagement hole  34   b , and hence discontinuous slip is not generated between the engagement hook  32   a  and the bracket plate member  34 . Thus, it is possible to reliably prevent generation of abnormal noise from the return spring  32 . Alternatively, during the returning pivot motion of the operation pedal  14 , the contact point A 1  at which the engagement hook  32   a  of the return spring  32  contacts the bracket plate member  34  does not shift from the one edge E 1  to the other edge E 2  in the pair of the edges E 1 , E 2  in the engagement hole  34   b , and hence slip is not generated between the engagement hook  32   a  and the bracket plate member  34 . Thus, it is possible to prevent generation of contact noise (knocking noise) that is generated when the engagement hook  32   a  hits the other edge E 2  due to abrupt slip. 
     Further, in the brake pedal apparatus  10  according to the present embodiment, the engagement hole  34   b  is formed so as to pass through the first plate portion  34   a  of the bracket plate member  34  in a direction perpendicular to the other surface  34   e  of the first plate portion  34   a , and the contact angle θ 1  between the surface direction of the other surface  34   e  of the first plate portion  34   a  of the bracket plate member  34 , in which the engagement hole  34   b  is formed, and the line L 1  of action of the return spring  32 , which passes through the contact point A 1 , takes a positive value in the entire operation angle range of the operation pedal  14 . Thus, the contact angle θ 1  does not shift from a positive value to a negative value across zero, and a friction force at the contact point A 1  is maintained. Therefore, an angle change of the line L 1  of action of the return spring  32  along with discontinuous slip of the engagement hook  32   a  is prevented from being inverted from a positive value to a negative value, and thus generation of abnormal noise from the return spring  32  during the returning pivot motion of the operation pedal  14  is reliably prevented. Further, an angle change of the line L 1  of action of the return spring  32  along with slip of the engagement hook  32   a  is prevented from being inverted from a positive value to a negative value, and thus the engagement hook  32   a  is prevented from hitting the edge E 2 . Further, according to the present embodiment, a component for preventing slip between the engagement hook  32   a  and the bracket plate member  34 , which becomes a cause for generation of abnormal noise, for example, a component such as a tube or a ring made of a plastic material or rubber need not be attached to the engagement hook  32   a  or the inside of the engagement hole  34   b  of the bracket plate member  34 . Therefore, it is not necessary to increase the number of components. As a result, cost reduction is achieved. 
     Embodiment 2 
     Next, another embodiment of the invention will be described. Note that in the following description, common portions between the embodiments will be denoted by the same reference symbols and the description thereof will be omitted. 
     A brake pedal apparatus  38  according to the present embodiment has substantially the same configuration as that of the brake pedal apparatus  10  in the embodiment 1 described above, except that attachment positions of the bracket plate member  34  and the spring engagement member  36 , with which the opposite end portions of the return spring  32  are respectively engaged, are different from those in the brake pedal apparatus  10 . 
     As illustrated in  FIG. 7  and  FIG. 8 , the spring engagement member  36  is fixed to a position fixing member (not illustrated) such that the contact point A 2  at which the engagement hook  32   b  and the edge E 4  of the engagement hole  36   b  contact each other is located below the contact point A 1 , that is, located closer to the pedal sheet  24  than the contact point A 1  is. Further, the surface direction of the other surface  34   e  of the first plate portion  34   a  of the bracket plate member  34  is set such that the degree of the contact angle θ 1  takes the same positive value as that of the contact angle θ 1  in Embodiment 1 when the pedal stroke is zero, and the bracket plate member  34  is fixed integrally with an intermediate portion of the operation pedal  14 . 
     Thus, in the brake pedal apparatus  38  as well as in the brake pedal apparatus  10  in Embodiment 1, when the pedal stroke is maximum, the contact angle θ 1  takes a positive value, and then the contact angle θ 1  decreases as the pedal stroke decreases. However, even when the pedal stroke is zero, the contact angle θ 1  takes a positive value. That is, the contact angle θ 1  takes a positive value in the entire operation angle range of the operation pedal  14 . Therefore, the brake pedal apparatus  38  produces effects similar to those of the brake pedal apparatus  10  in Embodiment 1. 
     In the above, the embodiments of the invention have been described with reference to the drawings, but the invention may be implemented in other modes. 
     For example, in the brake pedal apparatuses  10 ,  38  in the above-described embodiments, the circular engagement holes  34   b ,  36   b  are formed respectively in the first plate portion  34   a  of the bracket plate member  34  and the engagement plate portion  36   a  of the spring engagement member  36 . However, for example, semicircular cutouts may be formed. 
     Further, in the brake pedal apparatuses  10 ,  38  in the above-described embodiments, the surface direction of the other surface  34   e  of the first plate portion  34   a  of the bracket plate member  34  is set such that the contact angle θ 1  takes a positive value in the entire operation angle range of the operation pedal  14 . However, for example, the surface direction of the other surface  34   e  of the first plate portion  34   a  may be set such that the contact angle θ 1  takes a negative value in the entire operation angle range of the operation pedal  14 . With this configuration as well, it is possible to produce effects similar to those described above. 
     Further, in the above-described embodiments, the operation and effect produced in association with a returning operation of the operation pedal  14  has been described, but it is possible to produce similar operation and effect in association with a depressing operation of the operation pedal  14 . 
     Further, in the above-described embodiments, when the engagement hook  32   b  of the return spring  32 , which is located on the spring engagement member  36  side, is bent at a curvature radius similar to that of the engagement hook  32   a  located on the bracket plate member  34  side and the contact point A 2  at which the engagement hook  32   b  and the spring engagement member  36  contact each other moves in an entire pivot range of the operation pedal  14  to generate discontinuous slip, there is a possibility that the return spring  32  will be vibrated by the discontinuous slip to generate abnormal noise or a possibility that the engagement hook  32   b  will hit the edge E 3  to generate contact noise. Therefore, the configuration of the spring engagement member  36  may be similar to that of the bracket plate member  34  located on the engagement hook  32   a  side. That is, the surface direction of the one surface  36   c  or the other surface  36   d  of the portion of the spring engagement member  36 , in which the engagement hole  36   b  is formed, may be set such that the contact point A 2  at which the spring engagement member  36  contacts the one edge E 4  in the pair of the edges E 3 , E 4 , which are the ridgelines between the inner wall surface of the engagement hole  36   b  and the one surface  36   c  and the other surface  36   d  of the spring engagement member  36 , is the pivot point of the return spring  32  that pivots in accordance with an operation of the operation pedal  14  in the entire operation angle range of the operation pedal  14 . In this case as well, during the returning pivot motion of the operation pedal  14 , a contact state of the engagement hook  32   b  of the return spring  32  does not shift from the one edge E 4  to the other edge E 3  in the pair of the edges E 3 , E 4  in the engagement hole  36   b , and hence discontinuous slip is not generated at the engagement hook  32   a . Thus, it is possible to reliably prevent generation of abnormal noise from the return spring  32  and to reliably prevent generation of contact noise that is generated when the engagement hook  32   b  hits the other edge E 3 . 
     The invention may be implemented in various modes achieved by making various changes and improvements based on the knowledge of a person skilled in the art, although examples of the various modes will not be described. 
     NOMENCLATURE OF ELEMENTS 
     
         
         
           
               10 : brake pedal apparatus (vehicle operation pedal apparatus) 
               11 : pedal support (pedal support member) 
               14 : operation pedal 
               32 : return spring 
               32   a : engagement hooks 
               34 : bracket plate member 
               34   b : engagement hole (hole for engagement) 
               34   d : one surface 
               34   e : other surface 
               36 : spring engagement member (position fixing member) 
               36   a : engagement plate portion 
               38 : brake pedal apparatus (vehicle operation pedal apparatus) 
             A 1 : contact point 
             E 1 , E 2 : a pair of edges 
             L 1 : line of action of the return spring 
             O 1 : axis (one axis)