Cam Drive Mechanism Speed Control for Compact Camera Design
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Solution Overview
Problem
The existing camera designs face challenges in miniaturization due to the separate arrangement of the mirror drive mechanism and shutter control mechanism, leading to increased size and interference between components, as well as variations in rotational speed of the cam member causing inefficiencies in mirror operations and frame speed.
Innovation Solution
A compact camera design is achieved by integrating the mirror drive mechanism and shutter charge mechanism between the mirror box and battery chamber, with a slider system and end-face cam member that rotates to control the movable mirror's position, and a control apparatus that adjusts motor speed to stabilize cam member rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the mirror drive mechanism and shutter control mechanism are separately arranged on laterally opposite sides of the mirror box, then each mechanism can be independently controlled, but the camera size increases in the lateral direction
Solution Approach 1:
The patent combines the mirror drive mechanism and shutter control mechanism into a single integrated unit located on one side of the mirror box. The cam member serves dual functions: its first cam surface controls the movable mirror while its second cam surface controls the shutter curtains. This merging eliminates the need for separate mechanisms on opposite sides, reducing the camera's lateral width while maintaining independent control capabilities through the unified cam-driven system.
2Productivity
If the cam member rotates at high speed to increase frame speed, then photographing efficiency improves, but the cam follower may disengage from the cam surface causing operational failure
Solution Approach 1:
The patent applies a preliminary counteracting force through the spring member that constantly pushes the cam follower against the cam surface. This pre-applied force creates sufficient normal force between the cam follower and cam surface before high-speed rotation begins, preventing disengagement even during rapid acceleration and deceleration phases of the cam member rotation, thus maintaining reliable engagement at high frame speeds.
Solution Approach 2:
The patent modifies the cam surface geometry by creating an inclined cam surface that transitions from a horizontal first cam surface to an inclined second cam surface. This parameter change in the cam surface profile allows the cam follower to maintain contact through the inclined surface's geometric constraint, preventing disengagement during high-speed rotation while still enabling the required mirror and shutter operations.
3Speed
If the inclined cam area has a large projection amount to increase mirror operation speed, then frame speed improves, but shock increases causing mirror bouncing
Solution Approach 1:
The patent implements a two-stage cam surface design where the cam member rotates through a horizontal cam surface portion first, then transitions to an inclined cam surface portion. This dynamic, multi-stage approach allows the mirror to be raised smoothly during the horizontal phase and then quickly driven to the final position during the inclined phase, achieving high frame speed while controlling shock through the gradual transition rather than immediate inclined engagement.
Data Source
AI summary
A control apparatus for a cam drive mechanism comprising a motor, a driven member having a cam follower, a rotatable cam which is rotated by the motor, and a cam surface on the cam, the cam surface including a pressing area which is inclined so as to press the cam follower against a load when the cam is rotated by the motor and a recessed area which is inclined in a direction opposite to the inclination direction of said pressing area. A controller rotates the cam by the motor in a single direction, and changes a rotational speed of the motor between when the cam is positioned at a first rotational position at which the recessed area and the cam follower face each other, and when the cam is positioned at a second rotational position at which the pressing area and the cam follower face each other.