JP2000180690A - Lens driving method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the chattering phenomenon with a simple structure without impairing the degree of freedom in design by driving a moving lens frame by acting a viscous member in the sliding direction of a bush part. SOLUTION: As a result of the review of an analytic model for analyzing 'chattering phenomenon' in a lens driving device, the factor generating the self-exciting vibration depends on a frictional coefficient between a guide rod and a bush part, but the lens driving device itself also includes some factor, besides the frictional coefficient. The constant of viscosity between the lens part and the bush part, and that between a nut and the bush part can be arbitrarily varied by checking the minimum frictional coefficient generating the self-exciting vibration by changing each analytic parameter. Actually, a viscous member 62a such as rubber, an elastomer resin and the like is fitted and fixed between two springs 61a, 61b of a nut 72f. Whereby the constant of viscosity between the nut and the bush part can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a still camera,
Video camera, a lens driving method and a device for driving a lens used in a digital camera and the like, particularly,
The present invention relates to prevention of chattering phenomena occurring in driving a lens.

[0002]

2. Description of the Related Art Heretofore, there has been known a lens driving method and apparatus for driving a moving lens frame having a bush portion which is guided and slid by a guide rod via a driving force transmitting member by a driving force of a driving source. ing.

Here, as an example of a conventional lens driving device, a lens driving device used in a general video camera will be described. FIG. 11 is a perspective view of the configuration of a conventional lens driving device, FIG. 12A is a front view of a driving force transmitting member, and FIG. 12B is a side view of the driving force transmitting member.

[0004] As shown in FIG.
Is fixed to the support 73. A lead screw 71, which is an output shaft, is formed in the motor M. When the lead screw 71 rotates, a nut 72f engaged with the lead screw 71 linearly moves in the axial direction of the lead screw.

The nut 72f has two plate-like springs 6
5a and a spring 65b are provided, and a spring 65a and a spring 65b are provided.
Is a bush portion 21 which is a part of a movable lens frame 21 described later.
a is engaged with the receiving portions 21c and 21d provided in the a.

When the lead screw 71 is rotated and the nut 72f is moved to the left, the spring 65a and the receiving portion 21 are moved.
The bush part 21a moves leftward by c.
When the motor M is rotated in the reverse direction, the nut 72f moves rightward, and the spring 65b and the receiving portion 21d move the nut 72f.
a moves rightward.

On the other hand, the moving lens frame 21 is
b, a bush 21a, a U-groove 21e, and the like. The lens 31 is attached to the lens portion 21b, the bush portion 21a is engaged with the guide rod 51, and the U groove 21e is engaged with the guide rod 41. When the bush portion 21a moves, the movable lens frame 21 moves to the guide rod 41 and the guide rod 51.
, And is driven in the same direction as the optical axis X _1, and the lens 31 moves along the lens optical axis X ₁ .

Next, the driving force transmitting member will be further described. FIG. 12A is a front view of the driving force transmitting member.
As shown in the side view of the driving force transmitting member of FIG.
The front ends of the springs 65a and 65b provided on the bush 21a and the receiving portions 21c and 21 provided on the bush 21a are provided.
d between the bush 21a and the nut 72.
f is engaged. Here, A> B, where A is the free interval between the distal ends of the two springs 65a and 65b, B is the interval between the receiving portions 21c and 21d, and the bush portion 2
1a and the nut 72f are engaged without play in the X-axis direction.

Further, the spring 65a, the width of 65b and a length of C, and the length D of the guide rod center axis X ₂ direction length between the receiving portion 21c and the receiving portion 21d, the length C and a length By making D substantially the same, the receiving portions 21c and 21d
It works as a 2f rotation stop.

In the above-described lens driving device, when the lens is driven, a "chatter phenomenon" may occur. This "chatter phenomenon" is self-excited vibration in which energy from a driving source is converted into a vibration phenomenon by a stick-slip phenomenon. However, this self-excited vibration is caused not only by the frictional force between the guide rod 51 and the bush part 21a, but also by the physical properties such as the rigidity determined by the geometric shape and the material of the driven part of the movable lens frame 21. In the above-described conventional example, since a frictional force acts between the bush portion 21a and the guide rod 51, a stick-slip phenomenon occurs between the bush portion 21a and the guide rod 51 under a certain condition. The lens portion 21b of the moving lens frame 21 including the bush portion 21a may cause self-excited vibration.

Since the "chatter phenomenon" generally occurs when the frictional force increases, a lubricant such as grease is applied to minimize the frictional force between the guide rod 51 and the bush portion 21a. At present, the "chatter phenomenon" has not been well investigated.

[0012]

However, as described above, it is difficult to maintain a low friction coefficient by relying on a lubricant, and when the friction coefficient increases, the "chatter phenomenon" tends to occur.

Therefore, even if the friction coefficient between the guide rod and the bush is large, the "chatter phenomenon" can be achieved with a simple anti-chatter structure.
It is desired that the occurrence of blemishes hardly occurs. Further, it is also desired that anti-chatter measures can be easily taken by improving the existing lens driving device later.

The present applicant has clarified the relationship between the frictional force, which is the main cause of the "chatter phenomenon" in the lens driving device, the moving lens frame, the driving force transmitting member, and the like, and particularly, the critical friction coefficient at which self-excited vibration occurs. As a result of repeated analysis and research using an analytical model for a structure capable of making the maximum possible, it was clarified that the "chatter phenomenon" could be easily and reliably prevented, and the present invention was reached.

An object of the present invention is to reduce chattering phenomena occurring in a lens driving device without impairing the degree of freedom in design.
It is an object of the present invention to provide a lens driving method and a device which can be prevented with a simple structure.

[0016]

The above object can be achieved by any of the following constitutions.

(1) A movable lens frame having a bush portion guided and guided by a guide rod and having a lens portion holding a lens is provided, and is driven by a driving force of a driving source via a driving force transmitting member. In the lens driving method for driving the moving lens frame, a viscous member having a viscosity constant is provided in the driving force transmitting member, and the moving lens frame is driven by causing the viscous member to act in a sliding direction of the bush portion. A lens driving method characterized by the above-mentioned.

(2) A moving lens frame having a driving source, a bush portion guided by a guide rod and sliding, and having a lens portion holding a lens, and a driving force of the driving source for the moving lens frame. A driving force transmitting member that transmits the moving lens frame through the driving force transmitting member by the driving force of the driving source, wherein the driving force transmitting member has a viscosity constant. Provide members,
A lens driving device, wherein the moving lens frame is driven by causing the viscous member to act in a sliding direction of the bush portion.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A lens driving method and apparatus according to an embodiment of the present invention will be described with reference to the drawings. At first,
A method for preventing the chatter phenomenon in the lens driving device will be described, and a lens driving device to which the above-described chatter phenomenon preventing method is applied will be described.

FIG. 1 is a schematic view of an analytical model relating to a lens driving device, FIGS. 2 and 3 are diagrams showing the change of the moving distance and moving time and moving speed and moving time of the moving lens frame, and FIG. FIG. 5 is a diagram illustrating a change state of the moving speed and the moving time of the bush portion.

(Analysis Model) FIG. 1 shows an analysis model for analyzing the "chatter phenomenon" in the lens driving device. The symbols used in the description are as follows. The analysis parameters used in the analysis model are indicated by (*).

[0022] m ₁ [kg]: the mass of the lens portion of the movable lens frame _{(*) m 2 [kg]} : weight of the bush _{(*) k 1 [N /} m]: lens portion of the movable lens frame and the bush portion Stiffness constant (*) c ₁ [Ns / m]: viscous constant (*) between the lens portion and the bush portion of the moving lens frame k ₂ [N / m]: stiffness constant (*) between the nut and the bush portion c ₂ [Ns / m]: Viscosity constant between nut and bush part (*) L ₁ [m]: Distance between lens optical axis and guide rod center axis of bush part (*) L ₂ [m]: Drive shaft 2h [m]: Guide length of bush part (*) μ: Friction coefficient of bush part against guide rod μ ₀ : Absolute value of friction coefficient g: Gravity of gravity acceleration Q _1: frictional resistance at one end of the bush section Q _2: frictional resistance x of the other end of the bush section _1: the lens optical axis of the X-axis coordinate x _2: Warped X axis coordinate x _{0 of} nut part: X axis coordinate of nut (Equation of motion) Next, the equation of motion of the analytical model shown in FIG. The method of deriving the equation of motion is omitted.

[0023]

(Equation 1)

(Specifications and Numerical Calculation Results) Since this equation of motion cannot be opened analytically, numerical calculations were performed by a computer. The following "Table 1" was used as a typical specification value. Hereinafter, this data is treated as an initial value. Further, in “Equation 1”, μ = μ ₀ · sign (dx ₂ / d
The sign of μ shown in t) is the same as the sign of the moving speed (dx ₂ / dt).

[0025]

[Table 1]

The following "Equation 2" was used as an input condition.

[0027]

(Equation 2)

The following is the result of calculating the equation of motion using the above specification values and input conditions.

FIG. 2 shows the moving distance and moving time of the moving lens frame.
(A), moving speed and moving time of the moving lens frame
(B) of FIG. First, FIG.
Is the coefficient of friction μ₀= 0.58 change state
I have. The vertical axis indicates the moving distance of the lens portion of the moving lens frame.
x₁[M], and the horizontal axis indicates the movement time t [sec]
I have. From the figure, you can see a slight vibration at the beginning of movement.
Quickly attenuates, and then the same as the conditions given as input
Perform fast linear motion. X of nut given as input ₀Axial direction
Direction speed is 0.01 [m / sec].
For example, at time t = 0.1 [sec], the moving distance of the lens unit
Is x₁= 0.001 [m].

Next, FIG. 2B also shows a friction coefficient μ ₀ =
The change state at the time of 0.58 is shown. The vertical axis represents the moving speed dx ₁ / dt [m / of the lens portion of the moving lens frame.
sec], and the horizontal axis indicates the movement time t [sec]. From the figure, the moving speed is 0.01 [m / sec] at the beginning of movement.
c], it rapidly changes up and down, but is attenuated immediately and is moving at a constant velocity of 0.01 [m / sec].

Similarly, FIG. 3 shows the changing state (a) of the moving distance and moving time of the lens unit of the moving lens frame, and the changing state of the moving speed and moving time of the lens unit of the moving lens frame. First, FIG. 3A shows a changed state when the friction coefficient slightly increases and the friction coefficient μ ₀ = 0.59. The vertical axis indicates the movement distance x ₁ [m] of the lens unit, and the horizontal axis indicates the movement time t [sec]. As shown in the figure, the amplitude of the micro-vibration generated at the beginning of the movement grows with time without attenuating, and stops growing at a certain time.

Next, FIG. 3 (b) shows a change state when the friction coefficient slightly increases and the friction coefficient μ ₀ = 0.59. The vertical axis represents the moving speed dx ₁ / d of the lens unit.
t [m / sec], and the horizontal axis indicates the movement time t [sec]. From the figure, it can be seen that the amplitude of the micro-vibration generated at the beginning of movement does not attenuate, the moving speed grows with time centering on 0.01 [m / sec], the growth stops at a certain time, and the vibration of the same amplitude continues A typical self-excited vibration movement is seen.

Next, FIG. 4 shows a change state of the moving distance x ₂ [m] of the bush portion and the moving time t [sec] when the self-excited vibration occurs. From the figure,
The typical stick-slip phenomenon, in which the state of not moving at all called a stick (stick shown in the figure) and the state of large movement called slip (slip) shown in the figure alternately differ from the vibration of the lens portion, are described. Is shown.

Further, FIG. 5 shows this phenomenon as the moving speed dx ₂ / dt [m / sec] of the bush portion and the moving time t.
[Sec] shows a change state. From the figure, it can be seen that the vibration generated at the beginning of the movement gradually grows and the amplitude gradually increases, but there is a period in which the speed does not reach 0 and does not reach minus, and stops at 0. A period during which the other speed is in the vibration shape is a slip (sick shown in FIG. 4).
p).

(Evaluation and Prevention Method) From the above calculation results, the micro vibration generated at the beginning of the movement when the friction coefficient is less than a certain value is immediately attenuated. The micro-vibration generated gradually grows, and the amplitude gradually increases, but does not increase forever.At a certain time, the vibration shifts to the stick-slip phenomenon of the sliding part, and the vibration remains at a certain amplitude Is the self-excited vibration that lasts.

That is, the self-excited vibration means that the stick-slip phenomenon acts to maintain the vibration by limiting the vibration amplitude later, and is not a direct cause of the self-excited vibration. That is, referring to FIGS. 4 and 5, it can be understood from the fact that the vibration is generated and grows before the stick-slip phenomenon occurs.

Therefore, although the factors causing the self-excited vibration depend on the friction coefficient between the guide rod and the bush portion, some factors are included in the entire lens driving device in addition to the friction coefficient. become. To prevent this self-excited vibration from occurring, it means that self-excited vibration does not occur even with a large friction coefficient.Therefore, the minimum friction coefficient at which self-excited vibration occurs can be examined by changing each analysis parameter. As a result of the investigation, it was found that the following method can be used to increase the minimum friction coefficient at which self-excited vibration occurs.

That is, the mass m ₁ [kg] of the lens portion of the moving lens frame is reduced. Mass of bush part m ₂ [k
g] is reduced. Rigidity k ₁ between lens and bush
[N / m] is reduced. The viscosity constant c ₁ [Ns / m] between the lens portion and the bush portion is increased. The rigidity k ₂ [N / m] between the nut and the bush is increased. The viscosity constant c ₂ [Ns / m] between the nut and the bush is increased.
Distance L between the center axis of the guide rod of the lens part and the bush part
₁ [m] is reduced. The length L ₂ [m] between the drive shaft and the center axis of the guide rod of the bush portion is reduced. Further, the length 2h [m] of the bush portion is increased.

Here, to explain an example, constants of all analysis parameters are changed as shown in Table 2 from the above initial values.

[0040]

[Table 2]

Then, the minimum friction coefficient at which the self-excited vibration occurs increases from the aforementioned μ ₀ = 0.59 to μ ₀ = 0.88. This is because when the friction coefficient between the guide rod and the bush portion was reduced to 0.59 by lubricating oil or the like, the "chatter phenomenon" occurred. Has a coefficient of friction of 0.8
The "chatter phenomenon" does not occur until the value reaches 8, which is a great improvement. However, as a practical matter, it is difficult to implement all such structural changes from other design requirements, and this structural change may degrade completely different performance. For example, the mass of the lens portion of m ₁ [kg], the distance between the lens optical axis of L ₁ [m] and the bush portion, and the length of the bush portion of 2h [m] are almost determined by the optical system used. . Further, the mass of the bush portion of m ₂ [kg] is small and does not significantly affect the result. Also,
On the contrary, the rigidity between the lens portion and the bush portion of k ₁ [N / m] is desired to be increased due to the configuration as a component. Also, k ₂ [N /
If the rigidity between the nut and the bush portion of [m] is increased, so-called "image shaking" occurs in which the bending of the lead screw affects the image surface. Further, reducing the distance between the nut of L ₂ [m] and the bushing portion makes the entire motor closer to the guide rod, so there is a limit from the size of the motor.

Then, it is c that the value can be freely changed.
₁ [Ns / m] viscosity constant between lens part and bush, c ₂
It means the viscosity constant between the nut and the bush portion of [Ns / m]. However, of these two, c ₁ [Ns /
Since the operation of the viscosity constant between the lens unit and the bush of [m] relies on the material for forming the moving lens frame, other problems may occur depending on the material, or molding problems may occur. Issues such as increased costs also remain.

Therefore, it is only the viscosity constant of the nut and the bush part of c ₂ [Ns / m]. However, the operation of this damping is very simple, the optimum value can be used, and the cost is increased. Hateful. For example, as shown in FIG. 6 described later, two springs 61a and
b, c ₂ [Ns /
m] can increase the viscosity between the nut and the bush portion.

According to this configuration, various viscous members can be selected, and c ₂ can be set according to the situation. Also, this effect is large, and in this case, c ₂ [N
The parameters other than viscosity constant of s / m] Leave the default value, only the c ₂ 1 [Ns / m] from 10 [Ns /
By the m], it is possible to increase the coefficient of friction of critical to which the self-excited vibration occurs from mu ₀ = 0.59 to μ ₀ = 0.65.

If rubber or the like is used for the viscous member, c ₂ is 1 [N
[s / m] to 10 [Ns / m] is a level that can be easily realized, and can be further increased by selecting a material.

Next, an embodiment to which the method for preventing the above-mentioned "chatter phenomenon" is applied will be described with reference to the drawings. Note that members that are mechanically the same as those in FIGS. 11 and 12 of the conventional example are denoted by the same reference numerals, and a description thereof is partially omitted.

FIG. 6 is a perspective view showing the structure of a lens driving device according to the present invention. As shown in FIG. 6, a viscous member 62a such as rubber or elastomer resin is sandwiched and fixed between two springs 61a and 61b of a nut 72a. This allows c ₂
It is possible to increase the viscosity constant between the nut and the bush portion. Even if c ₂ is increased, c ₂ can be changed only by considering the self-excited vibration without affecting other performances.

Here, still another embodiment will be described with reference to the drawings. FIG. 7 is a side view of another driving force transmission unit. The material of the viscous member 62b is a synthetic resin material,
A nut 72b is insert-molded into the viscous member 62b to be integrated.

FIG. 8 is a side view of another driving force transmitting section. The material of the nut 72c and the material of the viscous member 62c are respectively different synthetic resin materials, and are integrally formed by two-color molding.

FIG. 9 is a side view of another driving force transmitting section. The material of the viscous member 62d is a synthetic resin material, and rigid members 63a and 63b are insert-molded and integrally formed with the viscous member 62d.

FIG. 10 is a side view of another driving force transmitting section. The rigid members 64a and 64b and the viscous member 62e
Are made of different synthetic resin materials, and are integrally formed by two-color molding.

[0052]

According to the above configuration, the following effects can be obtained.

According to the first and second aspects of the present invention, since the driving force transmitting member is provided with the viscous member having a viscous constant,
The chatter phenomenon that occurs in the lens driving device can be prevented with a simple structure without impairing the degree of freedom of design.

According to the third aspect of the present invention, the driving force transmitting member has a first rigid member having a rigidity constant in the forward direction;
A rigid member having a second rigid member having a rigidity constant in the backward direction is formed, and the viscous member is sandwiched between the first rigid member and the second rigid member. A viscous member, which is a member for preventing chattering, can be easily provided in the force transmitting portion.

According to the fourth aspect of the invention, the chattering phenomenon can be prevented with a simple structure having good durability.

According to the invention as set forth in claims 5 to 8, the chatter phenomenon can be prevented with an inexpensive, simple structure.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an analysis model related to a lens driving mechanism.

FIG. 2 is a diagram illustrating a change state of a moving distance and a moving time and a moving speed and a time of a lens unit.

FIG. 3 is a change state diagram of a moving distance, a moving time, and a speed and a time of a lens unit.

FIG. 4 is a change state diagram of a moving distance and a moving time of a bush portion.

FIG. 5 is a change state diagram of a moving speed and a moving time of a bush portion.

FIG. 6 is a configuration perspective view of a lens driving device of the present invention.

FIG. 7 is a side view of another main configuration of the present invention.

FIG. 8 is a side view of another main configuration of the present invention.

FIG. 9 is a side view of another main configuration of the present invention.

FIG. 10 is a side view of another main configuration of the present invention.

FIG. 11 is a configuration perspective view of a conventional lens driving device.

FIG. 12 is a front view and a side view of a main part configuration of FIG. 11;

[Explanation of symbols]

21 Moving lens frame 21a Bush part 51 Guide rod 62a, 62b, 62c, 62d, 62e Viscous member 72a, 72b, 72c, 72d, 72e, 72f Nut M Drive source (motor)

Claims (8)

[Claims] A moving lens frame having a bush portion guided by a guide rod and sliding, and having a lens portion holding a lens, wherein the moving lens frame is driven by a driving force of a driving source via a driving force transmitting member. In a lens driving method for driving a moving lens frame, a viscous member having a viscosity constant is provided in the driving force transmitting member, and the moving lens frame is driven by causing the viscous member to act in a sliding direction of the bush portion. Characteristic lens driving method. 2. A moving lens frame having a driving source, a bush portion guided by a guide rod and sliding, and having a lens portion holding a lens, and a driving force of the driving source being applied to the moving lens frame. A driving force transmitting member for transmitting the moving lens frame via the driving force transmitting member by the driving force of the driving source, wherein the driving force transmitting member has a viscous constant. Wherein the viscous member acts in the sliding direction of the bush portion to drive the movable lens frame. 3. The driving force transmitting member includes a first rigid member having a rigidity constant in a forward sliding direction of the bush portion, and a second rigid member having a rigidity constant in a backward sliding direction of the bush portion. A rigid member is provided, and the first rigid member and the second rigid member are provided.
The lens driving device according to claim 2, wherein the viscous member is held between the rigid members. 4. The lens driving device according to claim 2, wherein the material of the viscous member is a synthetic rubber, a natural rubber, or a synthetic resin material. 5. The material of the viscous member is a synthetic resin,
4. The lens driving device according to claim 2, wherein the viscous member is formed by integral resin molding by inserting the driving force transmitting member. 5. 6. The viscous member and the driving force transmitting member are made of different synthetic resin materials, and the viscous member and the driving force transmitting member are formed by two-color resin molding. Or the lens driving device according to 3. 7. The lens driving device according to claim 3, wherein the material of the viscous member is a synthetic resin material, and the viscous member is formed by integral resin molding by inserting the rigid member. 8. The rigid member and the viscous member are made of different synthetic resin materials, and the rigid member and the viscous member are formed by two-color resin molding.
3. The lens driving device according to claim 1.