JP2011221566A - Driving mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving mechanism for the optical device, in which noise emitted from meshing portions of the gears is reduced.SOLUTION: In the driving mechanism for the optical device, which transmits the power of a driving source to an object to a driven, by use of a plurality of the gears, the plurality of gears are made of at least polyester, polyamide, or polyacetal, and include: a first gear 12 having a bend elastic modulus equal to or higher than 10 kgf/mmbut equal to or lower than 100 kgf/mm, and a second gear 13 engaged with the first gear and having a bend elastic modulus equal to or hither than 50 kgf/mmbut equal to or lower than 1000 kgf/mm.

Description

  The present invention relates to a drive mechanism used in an optical apparatus such as a still camera or a video camera, and more particularly to a drive mechanism that transmits power of a drive source to a driven object using a plurality of gears.

  Still cameras and video cameras have various driving mechanisms such as a lens driving mechanism, a film feeding mechanism, and a tape feeding mechanism. This type of drive mechanism has a motor as a drive source, and generally transmits the power of the motor to a driven object (lens, film, video tape, etc.) via a reduction gear train composed of a plurality of gears. It is.

For this reason, when the drive mechanism is activated, not only the driving sound of the motor but also the gear meshing part and the shaft rotation support part are emitted, which sometimes feels annoying. Among them, a problem that is particularly problematic is a sound emitted from the meshing portion of the gear, specifically, a striking sound generated when the gear tooth surfaces collide with each other and a sliding sound generated by rubbing the tooth surfaces. This kind of sound can be heard as a louder sound than usual in a quiet environment, so when using a camera etc. in a place where quietness is required, it affects not only the photographer but also the surrounding people. .
An object of the present invention is to provide a drive mechanism for an optical device that reduces noise generated from a gear meshing portion.

The present invention is applied to a drive mechanism of an optical device that uses a plurality of gears to transmit the power of a drive source to a driven object. The plurality of gears are made of at least one of polyester, polyamide, and polyacetal, and the first gear has a bending elastic modulus of 10 kgf / mm ² or more and 100 kgf / mm ² or less, and meshes with the first gear 50 kgf. second gear having a flexural modulus of not less than / mm ² and not more than 1000 kgf / mm ² , thereby solving the above problems.
The invention of claim 2 is characterized in that the second gear is a gear having a flexural modulus of not less than 50 kgf / mm ^{2 and not} more than 700 kgf / mm ² .
The invention of claim 3, in which the second gear is characterized in that it is a gear with 50 kgf / mm ² or more and 300 kgf / mm ² or less of flexural modulus.
The invention of claim 4 is characterized in that either one of the first gear and the second gear is a gear that rotates at the highest speed among a plurality of gears.
The invention according to claim 5 is characterized in that the first gear and the second gear that rotate at a high speed have a higher flexural modulus than the other gear.
The invention of claim 6 is characterized in that at least one of the first gear and the second gear is a gear having a durometer hardness (type D) of 40 or more and 60 or less.
The invention of claim 7 is a gear in which the first gear has a durometer hardness (type D) of 40 or more and 55 or less, and the second gear has a durometer hardness (type D) of 45 or more and 60 or less. It is the gear which has.

According to the present invention, in the drive mechanism of the optical device that transmits the power of the drive source to the driven object using a plurality of gears, the plurality of gears are made of at least one of a polyester system, a polyamide system, and a polyacetal system. One of the gears has a flexural modulus of 10 kgf / mm ² or more and 100 kgf / mm ² or less, and the other gear meshing with this has a flexural modulus of 50 kgf / m 2.
Since m ² or more and 1000 kgf / mm ² or less are used, the noise generated from the meshing portion of the gear can be reduced without sacrificing the durability of the gear. In particular, if either one of the two gears is the fastest gear, the sound reduction effect is the highest.
If the bending elastic modulus of the gear rotating at a high speed is higher than that of the other gear, the durability can be further improved. Even if at least one of the gears is a gear having a durometer hardness (type D) of 40 or more and 60 or less, a high sound reduction effect can be obtained.

Schematic which shows the drive mechanism of the camera in embodiment of this invention. The side view which shows the experimental method in embodiment. The top view which similarly shows the experiment method. The figure which shows the experimental result in 1st Embodiment. The figure which shows the experimental result in 2nd Embodiment. The figure which similarly shows the experimental result in 2nd Embodiment.

-First embodiment-
A first embodiment in which the present invention is applied to a lens driving mechanism of a single-lens reflex camera will be described with reference to FIGS.
FIG. 1 is a schematic view showing a lens driving mechanism (focusing mechanism) of a camera. The rotation of the AF motor 11 provided in the camera body 10 is transmitted to the photographing lens 20 side through a reduction gear train composed of a plurality of resin gears 12 to 15. The gear 12 is attached to the output shaft of the motor 11, and the gear 12 meshes with the gear 13 of the next stage, and the rotation of the motor 11 is decelerated via these gears 12, 13 and the gears 14, 15 of the subsequent stage. The shaft 16 integrated with 15 is rotated. The shaft 16 is connected to the photographing lens side shaft 21 via a coupling, and a gear 22 integral with the shaft 21 is engaged with the gear 23. The rotation of the shaft 16 rotates the gear 23 via the shaft 21 and the gear 22, and accordingly, the focusing optical system L of the photographing lens 20 moves in the optical axis direction (arrow direction), and focus adjustment is performed.
The gear 12 attached to the output shaft of the motor 11 is a gear that rotates at the highest speed among the gears 12 to 15, 22, and 23 (hereinafter referred to as the highest speed gear), and the rotation speed is about 15000 rpm. . Since the highest speed gear 12 is the highest speed, it makes the loudest noise in the drive mechanism at the meshing portion with the gear 13 in the next stage, and reducing the sound is most effective for reducing the sound of the entire drive mechanism. . Therefore, the present inventors pay attention to two gears (one of which is the first gear and the other is the second gear) of the highest speed gear 12 and the gear 13 meshing therewith, and various materials are used as the gears 12 and 13. Experiments on sound reduction and durability were conducted using gears molded into various bending elastic moduli. 2 and 3, the camera 100 is installed in a soundproof room, and the microphone 41 is placed at an angle of about 45 degrees with respect to the optical axis of the photographing lens 20 and 20 cm from the front of the camera body. The sound level meter 42 measures the sound when the drive mechanism is activated. Note that gears other than the gears 12 and 13 are gears made of conventionally used materials.

The table of FIG. 4 shows the experimental results. Here, as a comparative example, using a bent gear 12 Modulus 1000 kgf / mm ² of PBT (Polybutylene Terephthalate), an elastic modulus 500 kgf / mm ² approximately polyacetal-based material bent to the gear 13. This is a combination generally used in the past. The “sound reduction amount” in the table indicates how many dB of sound reduction can be achieved at the A characteristic sound pressure level with respect to this comparative example (hereinafter, “dB” represents the A characteristic sound pressure level). From the table, it can be seen that when either one of the gears 12 and 13 has a flexural modulus of 1200 kgf / mm ² or more, no sound reduction effect is obtained.

Further, when the flexural modulus of one gear of 1000 kgf / mm ² is the flexural modulus of the other gear is a slight sound reduction effect as compared with the comparative example when the 10~100kgf / mm ² is obtained The numerical value is not so high as about 1 to 3 dB. Further, when the bending elastic modulus of one gear is 700 kgf / mm ² , the sound reduction effect is obtained when the bending elastic modulus of the other gear is 10 to 100 kgf / mm ² , and the value is about 2 to 4 dB. And higher than the previous case. Furthermore, when the flexural modulus of the one gear is 300 kgf / mm ² is flexural modulus of the other gear sound reducing effect when the 10~50kgf / mm ² is even higher and 3 to 5 dB. And the sound reduction effect increases as the flexural modulus of both gears decreases.

Here, the sound generated at the meshing portion of the gear includes a striking sound generated when the gear tooth surfaces collide with each other and a sliding sound generated when the tooth surfaces are rubbed with each other. It is thought that it contributes to the reduction of the hitting sound. That is, by constituting at least one of the two gears with a material having a small bending elastic modulus, the impact at the time of the tooth surface collision is absorbed, and the generation of sound is suppressed.
As a result of studying various materials, the present inventors have found that polyester-based, polyamide-based, and polyacetal-based materials have good molding accuracy as a gear even when molded with low bending elasticity, and have a high sound reduction effect. I found. Normally, materials with low flexural modulus are limited to JIS grades 6 to 7, but polyester, polyamide, and polyacetal materials have JIS grade 3 to 4 grade flexural elasticity. It was also found that polyurethane-based materials can be molded with low bending elasticity, but good molding accuracy cannot be obtained and the sound reduction effect is low.

  Also, in this experiment, several subjects were asked to listen to the sound, and sensory evaluation (evaluation of listening comfort) was also performed. As a result, as can be seen from the table, it can be seen that the sound quality changes as the sound reduction amount increases. “Good” indicates that 80% or more of the subjects evaluated that the sound was clearly better than that of the comparative example.

As described above, it has been found that the sound reduction effect increases as the bending elastic modulus of the gear decreases. However, since the strength decreases as the bending elastic modulus decreases, durability as a product becomes a problem. The driving durability performance in the table indicates the presence or absence of abnormalities when driven 10,000 times or more. In this experiment, abnormalities were observed when the bending elastic moduli of both gears 12 and 13 were both 10 kgf / mm ^2. It was found that the properties and part accuracy of molded products do not satisfy the product standards. Although not shown in the table, it was also found that when the flexural modulus of one gear was 5 kgf / mm ² or less, there was a problem in durability regardless of the flexural modulus of the other gear. However, even if the bending elastic modulus of one gear was 10 kgf / mm ² , no abnormality was observed in the durability if the bending elastic modulus of the other gear was 50 kgf / mm ² or more. Moreover, the direction where durability was improved when the material with a high bending elastic modulus was used for the gear 12 of the high speed side among the gears 12 and 13 was seen.

From the above, considering both sound reduction and durability, the bending elastic modulus of one of the gears 12 and 13 is set to 10 kgf / mm ² or more and 100 kgf / mm ² or less, and the bending of the other gear meshing with it is set. it is understood that it is sufficient modulus 50 kgf / mm ² or more and 1000 kgf / mm ² or less and. Further, in addition to this, the bending elastic modulus of the gear 12 rotating at a high speed is made higher than that of the gear 13, so that the durability can be further improved.

As an example, using a polyacetal (POM) material modulus of elasticity 300 kgf / mm ² bending to the gear 12, the case of using a polyester material modulus of elasticity 50 kgf / mm ² bending to the gear 13, as compared with that of the comparative example The total sound pressure was reduced by 5 dB. The gear 12 uses the above and an elastic modulus 300 kgf / mm ² of polyacetal (POM) material bent similarly, even in the case of using the polyamide material of elastic modulus 20 kgf / mm ² bending to the gear 13, that of the comparative example As a result, the total sound pressure was reduced by 5 dB. Furthermore, although only the data for the total sound pressure is shown in the table, as a result of experiments conducted only in the high frequency band of 1 KHz or more, which is the most detrimental, sound reduction of 10 dB or more was achieved in any case. Furthermore, in the sensory evaluation, 80% or more of the subjects evaluated that the sound was better than the comparative example. This is considered due to sound reduction in the high frequency band. In addition, the camera's operating standards were sufficiently cleared for durability.

As another example, when the gear 12 is a polyacetal material, the flexural modulus is 50 kgf / mm ² , and the gear 13 is replaced with a polyester material, and a polyamide material with a flexural modulus of 10 kgf / mm ² is used, The total sound pressure was further reduced by 1 dB, that is, 6 dB compared with the comparative example. Further, in the high frequency band of 1 KHz or higher, sound reduction of 10 dB or higher was achieved as described above.

  By the way, the degree of sound reduction at the meshing portion of the gear is slightly different depending on the material itself. The polyacetal and polyester materials mentioned above are materials with a high sound reduction effect, but especially polyacetal materials have high lubricity and contribute to the reduction of sliding noise between tooth surfaces and sliding noise at the shaft rotation support. it seems to do. Therefore, by configuring the gear with a polyacetal-based material having a low flexural modulus, both the striking sound and the sliding sound can be reduced. In addition, polyester materials and polyamide materials are thought to contribute particularly to the reduction of impact sound. By using highly lubricated polyester and polyamide materials, it is possible to reduce impact noise and sliding noise. Can be planned.

-Second Embodiment-
The second embodiment focuses on the bending elastic modulus, but also focuses on the hardness of the material in addition to this.
Generally, the hardness of a gear may vary depending on the molding conditions. If the allowable range of the hardness is narrowed, the yield is inevitably lowered. Therefore, the present inventors changed various molding conditions such as molding temperature and molding pressure for the highest speed gear 12 having a flexural modulus of 10 kgf / mm ² , which has obtained good results in the above-described flexural modulus experiment. The gears of the hardness of were made, and the amount of sound reduction was measured for each gear.

FIG. 5 shows the experimental results. The gear hardness is durometer hardness (type D: JIS K 6253). From this table, it can be seen that if the flexural modulus is about 10 kgf / mm ² , the same sound reduction effect can be obtained regardless of the hardness. However, a gear having a durometer hardness of less than 40 has a problem with durability. Note that it was impossible to create a gear having a durometer hardness of 55 or more even if the molding conditions were changed.
From the above, regarding the gear 12 having a flexural modulus of 10 kgf / mm ² , the allowable range of durometer hardness is 40 or more and 55 or less in consideration of sound reduction and durability.

Next, the present inventors similarly obtained a gear 13 having a flexural modulus of 700 kgf / mm ² with good results.
Also, the sound reduction amount was measured with various hardnesses, and experimental results as shown in FIG. 6 were obtained.
As can be seen from the table, when the flexural modulus is about 700 kgf / mm ² , the sound reduction effect tends to increase as the durometer hardness decreases. Note that it was impossible to create a gear having a durometer hardness of less than 45 even when the molding conditions were changed.
From the above, it has been found that the gear 13 having a flexural modulus of 700 kgf / mm ² can achieve a relatively high sound reduction effect if a gear having a durometer hardness of 45 to 60 is used.

In the above, attention is paid only to the highest speed gear and the gear meshing therewith, but other gears constituting the gear train are used with a flexural modulus of 10 kgf / mm ² or more and 100 kgf / mm ² or less and meshed with this gear. flexural modulus as gear 50 kgf / mm ² or more and 1000 kgf / mm ² or less of the sound reducing effect can be used as can be expected. The driving mechanism for AF driving has been described, but the present invention can also be applied to a driving mechanism for zoom driving or film feeding. Furthermore, the present invention is not limited to a single-lens reflex camera, and various drive mechanisms for a lens shutter camera, a digital still camera, or a video camera may be used. In the case of a video camera, in addition to the AF and zoom drive mechanisms described above, the present invention can also be applied to a video tape feed drive mechanism.

DESCRIPTION OF SYMBOLS 10 Camera body 11 AF drive motor 12 Highest speed gear 13-15, 22, 23 Gear 20 Shooting lens L Focusing optical system

Claims (7)

In the driving mechanism of the optical device that transmits the power of the driving source to the driven object using a plurality of gears, the plurality of gears are made of at least one of polyester, polyamide, and polyacetal, and are 10 kgf / mm ² or more. and a first gear having a 100 kgf / mm ² or less of flexural modulus, and characterized in that it comprises a second gear having 50 kgf / mm ² or more and 1000 kgf / mm ² or less flexural modulus of meshing with the first gear A driving mechanism for the optical device. 2. The optical device drive mechanism according to claim 1, wherein the second gear is a gear having a flexural modulus of 50 kgf / mm ² or more and 700 kgf / mm ² or less. Said second gear, the drive mechanism of the optical device according to claim 2, characterized in that a gear having 50 kgf / mm ² or more and 300 kgf / mm ² or less of flexural modulus.   4. The optical device drive mechanism according to claim 1, wherein one of the first gear and the second gear is a gear that rotates at a highest speed among the plurality of gears. 5.   The drive mechanism for an optical device according to claim 1, wherein a gear rotating at a high speed of the first and second gears has a higher bending elastic modulus than the other gear.   2. The optical device drive mechanism according to claim 1, wherein at least one of the first gear and the second gear is a gear having a durometer hardness (type D) of 40 or more and 60 or less. . The first gear is a gear having a durometer hardness (type D) of 40 or more and 55 or less, and the second gear is a gear having a durometer hardness (type D) of 45 or more and 60 or less. The drive mechanism for an optical device according to claim 6.

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