Drive apparatus

Abstract

A profile radius change rate, which is an amount of change in a profile radius of a drive cam relative to a rotational angle of the drive cam in a pocket boundary section located between a progressively changing portion and a pocket portion, is set such that a boundary sound pressure, which is a sound pressure generated when a contact point between a roller and the drive cam passes through the pocket boundary section in response to the rotational movement of the drive cam, is included in a reference sound pressure range, which is a range of variation in a sound pressure generated when the contact point passes through the progressively changing portion.

What is claimed is: 
     
         1 . A drive apparatus that adjusts a control amount of a controlled subject in response to an axial position of a control shaft member, the drive apparatus comprising:
 a drive source;   a driving-side gear that is joined to an output shaft of the drive source;   a driven-side gear that receives a drive force of the drive source directly from the driving-side gear or indirectly from the driving-side gear through at least one intermediate gear;   a drive cam that is rotatable about a camshaft member, which is joined to the driven-side gear, wherein a profile radius of the drive cam, which is a distance from a rotational center of the drive cam to an outer peripheral surface of the drive cam, is not uniform in a circumferential direction of the drive cam;   a contact portion that is placed on one radial side of the drive cam in a radial direction of the rotational center of the drive cam, wherein the contact portion is urged by the controlled subject to contact the outer peripheral surface of the drive cam at a contact point;   a support member that supports the contact portion, wherein the support member makes linear reciprocating movement in a direction perpendicular to an axial direction of the camshaft member in response to a change in the profile radius at the contact point upon rotational movement of the drive cam; and   the control shaft member that is joined to the support member, wherein the control shaft member makes linear reciprocating movement in an axial direction of the control shaft member together with the support member, wherein:   the drive cam includes:
 a progressively changing portion, in which the profile radius progressively changes in response to the rotational movement of the drive cam; and 
   a pocket portion, which is placed adjacent to the progressively changing portion in the circumferential direction, wherein the profile radius increases in both of a forward rotational direction and a reverse rotational direction of the drive cam in the pocket portion; and   a profile radius change rate, which is an amount of change in the profile radius relative to a rotational angle of the drive cam in a pocket boundary section located between the progressively changing portion and the pocket portion, is set such that a boundary sound pressure, which is a sound pressure generated when the contact point passes through the pocket boundary section in response to the rotational movement of the drive cam, is included in a reference sound pressure range, which is a range of variation in a sound pressure generated when the contact point passes through the progressively changing portion.   
     
     
         2 . The drive apparatus according to  claim 1 , wherein the profile radius change rate at the pocket boundary section is defined as an inclination of a straight line, which connects between an apex of the pocket boundary section and an inflection point that is closest to the apex and is located in one of the progressively changing portion and the pocket portion. 
     
     
         3 . The drive apparatus according to  claim 2 , wherein:
 the progressively changing portion is formed such that the profile radius is changed at a constant gradient in response to the rotational movement of the drive cam; and   the profile radius change rate at the progressively changing portion side is defined as a gradient of the progressively changing portion.   
     
     
         4 . The drive apparatus according to  claim 1 , wherein the driven-side gear receives the drive force of the drive source indirectly from the driving-side gear through the at least one intermediate gear. 
     
     
         5 . The drive apparatus according to  claim 1 , wherein:
 the driving-side gear is a spur gear; and   the driven-side gear is a spur gear.