JPH10186445A - Quantity-of-light adjusting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a quantity-of-light adjusting device held in such a state that a specified aperture formed by a quantity-of-light varying member may not be changed by the backlash of the bearing of the device and vibration and impact from the outside. SOLUTION: This quantity-of-light adjusting device is provided with a driving source where a driving coil 3 is arranged between a rotor magnet 1 and a stator yoke 2, quantity-of-light adjusting members 9 and 10 adjusting the diameter of opening of a diaphragm, and a transmitting means 8 transmitting the driving force of the driving source to the members 9 and 10; and the yoke 2 is provided with a notched part 2a forming the magnetic inflection point of a detent torque between the magnet 1 and the yoke 2 within the driving range of the driving source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light amount adjusting device mounted on an optical apparatus such as a video camera and a still camera.

[0002]

2. Description of the Related Art Conventionally, when this type of light amount adjusting device is mounted on, for example, a video camera, the light amount variable member is smoothly adjusted in order to perform automatic exposure control in response to a photographing condition and brightness which change every moment. The diaphragm opening diameter is changed by reciprocating drive. As a reciprocating drive device for reciprocatingly driving the light amount variable member, a driving method using only the electromagnetic action shown in FIG. A combined method has been proposed.

[0003] The reciprocating drive device of the light amount adjusting device shown in FIG. 7 is a magnet rotor 1 in which an output shaft is rotatably supported by bearings of a base plate 6 having a diaphragm opening 15 and a cap 7.
A yoke 2 fixed to a base plate 6 which is provided with an air gap around the outer periphery of the magnet rotor 1, and a magnet rotor 1
A drive unit is constituted by the drive coil 3 and the brake coil 4 disposed between the magnet rotor 1 and the yoke 20, and the magnet rotor 1
And an output lever 8 as a transmission member is fixed to the output shaft of FIG. A pair of light amount variable members 9 and 10 are provided between the base plate 6 and the case 12 having the aperture 16, and an engagement hole 9 a formed at an end of the pair of light amount variable members 9 and 10. The engagement pins 8a and 8b at both ends of the output lever 8 are engaged with the lever 10a.

[0004] In the system in which the spring action is used in combination with the electromagnetic action, the output lever 8 shown in FIG. 7 is biased in the closing direction by a spring member 14.

In the conventional light amount adjusting device shown in FIG.
As described in Japanese Utility Model Laid-Open Publication No. 58-97957, the yoke 20 is formed by rolling a band-shaped flat plate material to form a cylindrical body, and then seam welding a butt portion of a peripheral surface of the cylindrical body. It is constituted by cutting a cylindrical body, or is constituted as a cylindrical body having a butt portion or a joint portion of the yoke on the peripheral surface, and the butt portion or the joint portion is permanently fixed by bonding or welding. Regardless of the method, it is constituted by an engagement relationship such as mere mechanical engagement and mechanical fit and jigsaw fit.

[0006]

However, in the above-mentioned conventional light quantity adjusting device, the driving force is reduced in size and the power consumption is reduced, so that the magnetic force of the magnet rotor is reduced and the attraction force to the yoke is reduced and the shaft loss is reduced. Due to the reduction, the magnet rotor becomes magnetically neutral, and the following problem may occur.

That is, due to vibrations and shocks from the outside of the light amount adjusting device, the aperture held against the force from the light amount variable members 9 and 10 changes, and the light amount changes.

Further, the drive unit becomes magnetically neutral, the response of the light amount adjusting device becomes excessively sensitive to the circuit control, and an uncontrollable state such as oscillation occurs.

An object of a first invention according to the present application is to maintain a predetermined aperture formed by a light amount variable member of a light amount adjusting device so as not to change due to backlash of a bearing of the device, external vibration or impact. It is an object of the present invention to provide a light amount adjusting device capable of performing the above.

A second object of the present invention is to provide a light quantity adjusting device capable of increasing a margin for an uncontrollable state such as oscillation with respect to a control circuit of the light quantity adjusting device. It is in.

[0011] An object of a third invention according to the present application is to provide a system having a spring for urging a transmission member to a fixed position.
A predetermined aperture formed by the light amount variable member of the light amount adjusting device can be held so as not to change due to backlash of the bearing of the device, vibration or external impact, and further, to the control circuit of the light amount adjusting device. Another object of the present invention is to provide a light amount adjusting device capable of increasing a margin for an uncontrollable state such as oscillation.

A fourth object of the present invention, in addition to the first and second objects, is to prevent the yokes from being entangled with each other when the yokes are in a component state and to increase the mechanical strength. An object of the present invention is to provide a light amount adjusting device capable of causing the light amount to be adjusted.

The fifth object of the present invention relates to the first, second, third, fourth, and fifth objects of the present invention. Another object of the present invention is to provide a light amount adjusting device that can be applied to a small-sized device.

[0014]

Means for Solving the Problems An object of the first aspect of the present invention is to provide a rotor magnet comprising a permanent magnet and a ferromagnetic material forming a magnetic circuit by forming a gap with the rotor magnet. A drive source comprising a stator yoke, a drive coil, a light quantity adjusting member for adjusting the aperture opening diameter, and a transmitting means for transmitting the driving force of the drive source to the light quantity adjusting member. A magnetic inflection point of detent torque between the rotor magnet and the stator yoke is provided within a drive range of the drive source.

In the above configuration, when a magnetic inflection point is generated, the magnetic circuit of the driving source is disturbed and the magnetic neutrality of the magnet rotor is broken, and a magnetic inflection point is formed, for example, a groove or a notch of a yoke. And so on so that the rotor magnet is attracted to the opposite side.

For this reason, it is possible to stabilize the rotational movement by suppressing the backlash in the bearing hole of the rotor magnet and to stabilize the opening diameter formed by the light amount adjusting member engaged with the driving source. Becomes possible.

According to a second aspect of the present invention, the magnetic inflection point formed in the stator yoke is provided in a half area on the small throttle side in the operating range of the apex of the pole of the rotor magnet. It is a thing.

In the above configuration, the magnet rotor operates so that the force drawn to the yoke is at the time of a small aperture.

The third aspect of the present invention, which realizes the object of the present invention, has a spring member for urging the transmission means toward a predetermined position when the power supply to the drive coil is cut off. In the above configuration, the transmission means operates so as to be spring-biased to the fully open position or the fully closed position.

According to a fourth aspect of the present invention, the magnetic inflection point is formed by a hole provided in the yoke.

In the above configuration, even if the magnetic inflection point is formed by a hole, the magnet rotor operates so as to be drawn in a specific direction of the yoke. Further, unlike the notch portion, there is no possibility of entanglement with each other at the time of single article conveyance.

In a configuration for realizing the object of the fifth invention according to the present application, the total aperture diameter of the light amount adjusting member is set to 12 mm or less in diameter.

In the above configuration, when the diameter of the entire aperture is reduced, the influence of the fluctuation of the transmission member due to external vibration or impact on the change in the amount of light has a large effect.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is an exploded perspective view showing a first embodiment of a light quantity adjusting device according to the present invention.

In the drawing, reference numeral 1 denotes a rotor magnet rotatably disposed and magnetized with two poles in the radial direction, and 2 has a cutout 2a, and is provided with a rotor magnet 1 through an empty wall (gap). A yoke made of a ferromagnetic material, which is disposed opposite to and constitutes a magnetic circuit, 3 is a drive coil for driving the rotor magnet 1, and 4 is for detecting a back electromotive voltage proportional to the rotation speed of the rotor magnet 1. Brake coil.

Reference numeral 5 denotes a tape for fixing the drive coil 3 and the braking coil 4, and 6 denotes a base plate having a diaphragm opening 15.
Bearing (not shown) of rotor magnet 1 and transmission member 8
, And supports and locks each member. Reference numeral 7 denotes a cap for bearing the rotor magnet 1.

Reference numeral 8 denotes an output lever as a transmission member for transmitting the driving force of the rotor magnet 1 to the light amount variable members 9 and 10. The rotation range is regulated by a stopper (not shown) provided on the base plate 6. This also has the function of regulating the drive range of the rotor magnet 1.

Numerals 9 and 10 are driven by being fitted to the transmission member 8 to determine the aperture opening and vary the light amount, and 11 is fixed to one of the light amount variable members 9 and controls the excessive light amount. ND filter for softening, 12 is opening 16
And a case 13 for supporting the light amount variable members 9 and 10, and a printed wiring board 13 to which terminals of the drive coil 3 and the braking coil 4 are soldered to transmit and receive signals from outside. Reference numeral 17 denotes a Hall element for detecting the rotation of the rotor magnet 1.

In this embodiment, the yoke 2 is formed with a notch 2a for setting a magnetic inflection point at a position where the yoke 2 does not face the drive coil 3 and the braking coil 4.

Here, at the magnetic inflection point, a uniform magnetic force acts between the magnet and the stator. Therefore, the force for attracting the rotor magnet is also uniform.

However, by providing notches, holes, and the like in the stator yoke, the area and volume become non-uniform. A portion having a small area and a small volume also has a reduced magnetic force. The portion where the magnetic force is reduced is referred to as a magnetic inflection point in this specification.

The operation of the magnetic inflection point of the yoke 2 according to the present embodiment will be described below with reference to a model diagram of a driving section shown in FIG. 2. In the present embodiment, the magnetization of the rotor magnet 1 is performed. Transmission member 8 in accordance with the boundary position
Is fixed to the output shaft of the rotor magnet 1, and the positional relationship between the notch 2a of the yoke 2 and the rotor magnet 1 is as shown in FIG.

In the above configuration, the notch 2a of the yoke 2 causes the rotor magnet 1 to be magnetically bent due to the notch in the yoke, and a non-uniform force acts on the rotor magnet in the direction of the arrow.

Referring to FIG. 2 as an example, at the closed position shown in FIG. 2A, a notch is set at the vertex of one pole of the rotor magnet. In this state, the magnetic force is separated into t1 and t2 at the notch 2a, and the resultant force becomes T2. At the notch 2a, there is no attraction to the yoke 2, so that T1> T2. As a result, the rotor magnet 1 is drawn in the direction of the magnetic force T1, and the coercive force there is strong.

Next, when the coil is energized, a force is generated in the r direction, and the rotor magnet 1 and the output lever 8 as a transmission member rotate integrally. Although the magnitude of the magnetic force T1 does not change, the magnitude of the magnetic forces t1 and t2 changes with rotation. At the intermediate stop position shown in FIG. 2B, when rotating from the closing direction to the opening direction shown in FIG. 2A, the relationship changes to t1> t2. When the magnetic force T2 is closed, the peak of the magnetic force is in the notch, so that the magnitude of T2 is larger than that of the closed magnetic force.

The top of the rotor magnet 1 has the strongest magnetic force, and becomes weaker as the distance from the center increases.

[0037] In the range of closing to intermediate aperture to fully open,
Although the magnetic force T1 does not change, the magnetic force T2 is large, and the direction in which the force acts changes in the direction to cancel the magnetic force T1, and FIG.
The pulling effect is minimized by the open cut shown in FIG.

That is, when the notch 2a and the magnetic force peak (peak of the pole) coincide, the attraction effect is maximized.

By comparison, when the light amount adjusting member is fully opened and when the small aperture is almost fully closed, the rate of change of the aperture area becomes large with respect to the variation of the driving unit at the time of small aperture. Therefore, it is desirable to set the notch 2a of the yoke 2, that is, the magnetic inflection point, so as to obtain the effect on the light quantity change so that the drawing effect is maximized on the small stop side from the intermediate stop. In other words, the magnetic inflection point is set in a range closer to the small aperture than half the moving range of the pole apex.

The position of the notch 2a of this embodiment for forming the magnetic inflection point may be any position other than the range of 1/2 on the small aperture side in FIG.

Further, the brake coil 4 may not be provided, or the space of the brake coil 4 may be used for the drive coil 3.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
An embodiment will be described.

FIG. 3 shows a transmission member 8 according to the first embodiment shown in FIG. 1 to which a spring 14 for urging the transmission member 8 in a certain direction is attached. The other members are common, and are denoted by the same reference numerals. Description is omitted.

In the above configuration, when the spring is biased in the maximum direction in the biasing direction due to its characteristics, for example, in the closing direction,
The biasing force at the fully closed position is minimized within the operating range of the driving unit, and is maximized at the fully opened position.

At this minimum point, the force holding the rotor magnet 1 of the drive unit also becomes weak. In the present embodiment, the notch 2a of the yoke 2 is provided at a position where the holding force of the spring is weakened.

(Third Embodiment) FIGS. 4 and 5 show a third embodiment.

FIG. 4 differs from FIG. 3 only in the shape of the yoke 2 in the second embodiment, and the other members are common.

The yoke 2 in the present embodiment has a magnetic inflection point formed in a hole 2b formed on the side surface of the yoke 2, and the magnetic inflection point is formed in the hole 2b. 2 can be increased in mechanical strength, and since there is no cutout portion in single-piece conveyance or the like, the yokes do not become entangled with each other.

The hole for the magnetic inflection point formed in the yoke 2 may be not only a perfect circle but also a deformed hole. Further, the hole may have a shape as shown in FIGS. It may be something.

(Fourth Embodiment) FIG. 6 shows a fourth embodiment.

The yoke 2 in the first and second embodiments
The notch 2a may have various grooves as shown in FIGS. 6 (a) to 6 (h) as well as a simple slit shape. For example, the notch 2a of the yoke 2 may have a different shape. With such a groove, the mechanical strength of the yoke 2 can be increased, and the entanglement of the yokes in single-piece conveyance or the like is eliminated.

[0052]

According to the first and second aspects of the present invention, a magnetic inflection point is formed by the notch of the stator yoke, whereby the rotor magnet is attracted, and the play in the bearing hole of the rotor magnet is reduced. To stabilize the rotational movement, stabilize the aperture shape and area of the light amount adjusting member engaged with the drive source, and provide a highly reliable light amount adjusting device with stable light amount.

According to the third aspect of the present invention, by setting the position where the rotor magnet is drawn to the small aperture side,
It is possible to provide a highly reliable light amount adjusting device that stabilizes the aperture shape and area at the time of a small aperture, which is greatly affected by the fluctuation of the driving source, and stabilizes the light amount.

According to the fourth aspect of the present invention, the above-described effects can be obtained even in a light amount adjusting device having a spring in which the transmitting member is biased in a fixed direction when the power is cut off.

According to the fifth aspect of the present invention, an inflection point can be easily formed on the stator yoke.

According to the sixth aspect of the present invention, it is possible to provide a stator yoke which has a magnetic inflection point, can increase the mechanical strength of the stator yoke, and can prevent entanglement during transportation of a single component.

According to the seventh aspect of the present invention, the light amount is stable and the light amount is stable with a small light amount adjusting device having a large aperture diameter of 12 mm or less, in which the diameter of the stop is particularly small and the light amount change at the time of the small stop is large. An adjustment device can be provided.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a first embodiment of the present invention.

FIG. 2 is a diagram showing the operation of the light amount adjusting device of FIG. 1;

FIG. 3 is an exploded perspective view of a second embodiment of the present invention.

FIG. 4 is an exploded perspective view of a third embodiment of the present invention.

FIG. 5 is a plan view of various forms of holes of a yoke showing a fourth embodiment of the present invention.

FIG. 6 is a plan view of various forms of a groove of a yoke according to a fifth embodiment of the present invention.

FIG. 7 is an exploded perspective view of a conventional light amount adjusting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rotor magnet 2 ... Yoke 2a ... Notch 2b ... Hole 3 ... Drive coil 4 ... Braking coil 5 ... Tape 6 ... Ground plate 7 ... Cap 8 ... Transmission member 9 ... Light amount variable member 10 ... Light amount variable member 11 ... ND Filter 12 ... Case 13 ... Printed circuit board 14 ... Return spring 15 ... Opening diameter 17 ... Hall element

Claims (7)

[Claims] 1. A rotor magnet comprising a permanent magnet,
A driving source including a stator yoke made of a ferromagnetic material forming a magnetic circuit by forming a gap with the rotor magnet, a driving coil, a light amount adjusting member for adjusting an aperture opening diameter, and a driving force of the driving source And a transmitting means for transmitting the light amount to the light amount adjusting member, wherein a magnetic inflection point of detent torque between the rotor magnet and the stator yoke is provided within a drive range of the drive source. Light quantity control device. 2. The light quantity adjusting device according to claim 1, wherein the magnetic inflection point is formed on the stator yoke. 3. The method according to claim 2, wherein the magnetic inflection point formed in the stator yoke is provided in a half range on the small throttle side in an operating range of a pole apex of the rotor magnet. Light quantity control device. 4. The light amount adjusting device according to claim 1, further comprising a spring member for urging the transmission means toward a predetermined position when the power supply to the drive coil is cut off. 5. The light amount adjusting device according to claim 1, wherein the magnetic inflection point is formed by a cutout provided in the yoke. 6. The light amount adjusting device according to claim 1, wherein the magnetic inflection point is formed by a hole provided in the yoke. 7. The light quantity adjusting device according to claim 1, wherein the total aperture diameter of the light quantity adjusting member is 12 mm or less.