Mirror drive device capable of high-speed forward and backward driving of mirror

Patent metadata

Field	Value
Publication number	US-9964753-B2
Application number	US-201514743201-A
Country	US
Kind code	B2
Filing date	Jun 18, 2015
Priority date	Jun 25, 2014
Publication date	May 8, 2018
Grant date	May 8, 2018

Abstract

A mirror drive device in which the speed of forward and backward movement of a mirror is increased while reducing a power amount required therefor without affecting a finder image and a focus distance of an image viewed through a finder. A mirror-down cam is cam-engaged with a drive shaft provided in a mirror holder, and causes the mirror holder to enter a finder observation position of a photographing optical path. A mirror-up cam is cam-engaged with the drive shaft, and causes the mirror holder to retract from the photographing optical path. A down spring urges the mirror holder toward the finder observation position with low necessary and sufficient pressure. A motor transmits rotation to the mirror-down cam and the mirror-up cam via a shift gear train. The rotation axes of the mirror-down cam and the mirror-up cam are arranged in positions different from each other.

First claim

What is claimed is:

1. A mirror drive device that drives a mirror between a first state in which the mirror enters a photographing optical path and a second state in which the mirror retracts from the photographing optical path, the mirror drive device comprising:
a mirror holder having a shaft and configured to hold the mirror;
a first cam member configured to be cam-engageable with the shaft;
a second cam member configured to be cam-engageable with the shaft; and
a drive source configured to drive the first cam member and the second cam member,
wherein the mirror drive device is configured such that when the mirror is placed in the second state, the shaft and the first cam member are brought into cam engagement with each other, and
wherein the mirror drive device is configured such that when the mirror is placed in the first state, the shaft is not brought into cam engagement with either of the first cam member and the second cam member.

2. The mirror drive device according to claim 1 , further comprising an urging member configured to urge the mirror holder so as to place the mirror in the first state,
wherein an urging force of the urging member for urging the mirror holder is decomposed into a first component force acting toward a rotational center of the mirror holder and a second component force acting in a direction in which the mirror holder is caused to be rotated so as to place the mirror in the first state,
wherein the mirror drive device is configured such that a magnitude relationship between the first component force and the second component force is changed in response to a position of the mirror.

3. The mirror drive device according to claim 2 , wherein the mirror drive device is configured such that when the second component force becomes smaller than the first component force, the drive source reduces the speed at which the first cam member and the second cam member are driven.

4. The mirror drive device according to claim 1 , further comprising an positioning member configured to be brought into contact with the mirror holder when the mirror is placed in the first state,
wherein the positioning member is provided such that a position of contact thereof with the mirror holder can be adjusted.

5. The mirror drive device according to claim 1 , wherein the mirror drive device is configured such that when the mirror is changed from the first state into the second state without driving by the drive source, the shaft and the second cam member are not brought into cam engagement with each other.

Assignees

• Canon Kk

Inventors

• Imaizumi Takuya

Classifications

• G02B26/0816 Primary

  by means of one or more reflecting elements · CPC title

• G03B19/12

  Reflex cameras with single objective and a movable reflector or a partly-transmitting mirror · CPC title

• G03B13/02

  Viewfinders · CPC title