JPH04136906A - Photographing lens driving device for camera - Google Patents

Abstract

PURPOSE:To prevent an optical hysteresis on a photographing lens which advances/retreats while linking with a member to be moved from occurring by pressing an engaging means constituted of a wire rod to the thread groove of a male screw part formed on a main shaft and attaching this engaging means to the member to be moved. CONSTITUTION:Since the straight line part 24a of a pressing spring 24 is engaged to the thread groove of the male screw part 22a of the driving shaft 22 of a stepping motor 20, by the rotation of the driving shaft 22, the surface of one side of the thread groove pushes and advances the straight line part 24a written above, a lens extending member 18 to support the pressing spring 24 is led and moved in the shaft direction of the driving shaft 22 by a specified distance by a guiding hole 18j. The straight line part 24a written above is fixed by a hooking part 18g, a projecting part 18d and two spring pressers 18f with respect to the shaft direction of the driving shaft 22. Consequently, when the stepping motor is driven at the same angle both in the case of a normal rotation and a reverse rotation, the lens extending member 18 is returned to an origin position, the optical hysteresis is prevented from occurring at the advancing time of the focusing lens 16 and at the retreating time of it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a zoom device that continuously changes the focal length of a camera, or an autofocus device that automatically focuses (hereinafter referred to as rAF device). ) relates to a photographic lens driving device for transmitting power of a motor to a lens holding member to move a photographic lens in an optical axis direction.

[Prior Art] In order to easily take photographs, there are zoom devices that move the photographing lens forward and backward in the optical axis direction to continuously change the focal length, and that automatically focus on the film according to this focal length. Cameras, especially compact cameras, are becoming popular, especially compact cameras equipped with AF devices that adjust the distance.

For example, an AF device is a device that focuses by moving a focus lens in the optical axis direction, and power from a motor or the like is used to drive the lens.

A conventional photographic lens driving device of this type is shown in FIG.

As shown in FIG. 4, several guide rods 2 are arranged inside the lens barrel 1 of the camera in parallel to the optical axis P, and a lens frame 3 is attached to the guide rods 2 in the optical axis direction. Supported to move. A focus lens 4 is held in this lens frame 3.

Further, a stepping motor 5 is disposed outside the lens barrel 1 with its drive shaft 6 substantially parallel to the optical axis P.
A male threaded portion 6a is provided on the outer periphery of the drive shaft 6.

A female screw portion 7b formed inside the engaging portion 7a of the lens feed member 7 is screwed into the male screw portion 6a, and the lens feed member 7 is attached to the drive shaft 6.

A distal end portion 7d of an arm 7c provided to protrude to the side of the engaging portion 7a of the lens feeding member 7 is linked to the lens frame 3. Further, a compression coil spring 8 is interposed between the stepping motor 5 and the lens feeding member 7, with the drive shaft 6 of the stepping motor 5 as the core, and its restoring force is applied to the stepping motor 5 and the lens feeding member 7. is biased in a direction that separates them from each other.

When the stepping motor 5 is driven, the drive shaft 6
The lens feeding member 7 is moved by the male screw portion 6a provided in the lens frame 2, and the lens frame 3 is also guided by the guide rod 2 and moved along the optical axis P accordingly. Therefore, the focus lens 4 held in this lens frame 3 also moves on the optical axis P.

[Problems to be Solved by the Invention] However, in the lens feeding member 7 described above, when the lens frame 3 is being fed, it is difficult to forcibly stop the lens feeding member 7 or the lens frame 3 by some external force. In this case, since the stepping motor 5 continues to be driven, an extra load is placed on the male screw portion 6a, and there is a risk that the screw thread may collapse.

Furthermore, since the mechanism is such that the male threaded portion 6a and the female threaded portion 7b are screwed together and the focus lens 4 is advanced or retreated according to the rotational direction of the male threaded portion 6a, the focus lens 4 may be stopped at a predetermined position. Even so, optical hysteresis occurs when moving forward and stopping and when moving backward and stopping. That is, since there is backlash in the screwing relationship between the male threaded portion 6a and the female threaded portion 7b, when the male threaded portion 6a is rotated at a certain number of rotations to advance the focus lens 4 to a predetermined position, The focus lens 4 does not stop at the original position even if it is retreated from the position at the same number of rotations. In order to eliminate this optical hysteresis, for example, when reversing, the number of rotations is increased to position the motor 5 further backward than the original position, and then the motor 5 is rotated in the opposite direction to move the focus lens 4 forward slightly. , the control of the motor 5 is complicated.

Therefore, the present invention makes it possible to safely operate the motor even when some external force is applied to the lens frame or the lens feeding member and cause them to stop. It is an object of the present invention to provide a photographic lens driving device for a camera that does not cause hysteresis.

[Means for Solving the Problems] In order to achieve the above object, a photographing lens driving device for a camera according to the present invention links the photographing lens to the drive shaft of the lens driving motor by rotation of the lens driving motor. A photographing lens drive device for a camera that moves forward and backward along a main shaft, the driven member having a male thread formed on the main shaft rotated by the lens drive motor, a driven member having a guide hole into which the main shaft is loosely inserted, and the driven member. attached to
an engaging means made of a wire that extends in a direction intersecting the main shaft and engages with a thread groove of the male threaded portion formed on the main shaft, and presses the engaging means into the thread groove of the male threaded portion. It is characterized in that it comprises a biasing means, and the photographing lens is linked to the driven member.

[Function] When the main shaft rotates due to the rotation of the lens drive motor, the side surface of the thread groove of the male threaded portion formed on the main shaft is pressed against the engaging means that engages with the thread groove. This engaging means is attached to the driven member, and since the photographing lens is linked to this driven member, the wave member does not rotate with respect to the main axis, and therefore the engaging means is attached to the threaded groove. It will move along the main axis due to the force from the side. Therefore, the driven member supporting the engagement means moves in the direction of the main axis, and the photographing lens linked to the wave member moves on the optical axis.

Moreover, since the engaging means is in close contact with both side surfaces of the thread groove under the pressing force of the urging means, it moves forward and backward according to the rotational direction of the main shaft, and there is a gap between the engaging means and the thread groove. teeth,
There is no backlash like in normal male and female screw threads.

In addition, if the main shaft continues to rotate even though the driven member has stopped due to some external force, the side surface of the thread groove is strongly pressed against the engagement means, and the side surface of the thread groove is formed into an inclined surface. Therefore, the force J is applied in the direction of pushing the engaging means out of the thread groove. If this pushing force is greater than the pushing force of the urging means, the engaging means will be pushed out of the thread groove, and even if the driven member is stopped, the main shaft, that is, the lens driving motor It can keep spinning.

[Embodiment] Hereinafter, a photographic lens driving device for a camera according to the present invention will be specifically described based on the illustrated embodiment.

As shown in FIG. 1, an appropriate number of guide rods 12 are provided on the lens barrel lO of the camera substantially parallel to the optical axis P. These guide rods 12 are inserted into the through holes 1 formed in the lens frame 14.
4a and the guide hole 1 provided in the lens frame guide member 15
5a, and the lens frame guide member 15 is linked to the lens frame 14, so that the lens frame 14 is slidably provided on these guide rods 12. A focus lens 16 is held in this lens frame 14.

On the other hand, on the outer periphery of the lens barrel 10, a stepping motor 20 as a lens driving motor is connected to its driving shaft 2, which is a main shaft.
The driving shaft 22 of the stepping motor 20 has a male threaded portion 22a formed on its outer periphery. This male screw part 22
As shown in FIG. 3, a has a shape in which the top of the screw thread is flattened, and its outer diameter is slightly smaller than the inner diameter of a guide hole, which will be described later.

The drive shaft 22 has a guide hole 18 formed in the guide portion 18b of the lens feeding member 18 on the driven portion side.
j is loosely fitted.

As shown in FIG. 2, this lens feeding member 18 has a mounting portion 18 that is provided at one end of the guide portion 18b into which the drive shaft 22 is loosely inserted, protruding in a direction substantially perpendicular to the drive shaft 22.
It has a. The distal end of the mounting portion 18a is formed into a bifurcated shape and provided with a groove 18c, and the distal end passes through the lens barrel 10, and as shown in FIG. Some of them are connected. A protrusion 1 protruding laterally is provided on one side of the base of the mounting portion 18a.
8d, and a spring core 18e is formed on the projection 18d substantially parallel to the guide portion 18b.

Further, an engaging protrusion 18 is provided on the other side of the base of the mounting portion 18a.
A spring hooking portion 18g having a diameter h is formed, and a drive shaft 22 inserted through the guide portion 18b is positioned between the spring hooking portion 18g and the spring core 18e.

A presser spring 24 made of a torsion coil spring is wound around the spring core 18e as a biasing means, and one end of the presser spring 24 is engaged with a spring support portion 18i formed in a part of the guide portion 18b. , the other end engages with the engagement protrusion 18h, and a straight portion 24a serving as engagement means is formed between the engagement protrusion 18h and the spring core 18e. In addition,
This straight portion 24a is connected to two spring retainers 18f formed on the end surface of the bipedal guide portion 18b and the projection portion 18d.
By being positioned in contact with the inner surface of the spring hooking part 18g, the drive shaft 22 is prevented from being bent in the axial direction. That is, the straight portion 24a is connected to the drive shaft 22 loosely inserted into the guide hole 18j of the guide portion 18b.
The hook is placed in a position that overlaps a part of the

As shown in FIG. 3, the straight portion 24a is connected to the male screw portion 2 of the drive shaft 22 loosely inserted into the guide hole 18j.
2a, and is pressed against both sides of the thread groove by the restoring force of the presser spring 24.

The operation of the camera lens driving device configured as above will be described below.

As shown in FIG. 1, when a signal of an appropriate number of steps is input to the stepping motor 20, the stepping motor 2
0 rotates by a predetermined angle in one direction.

This direction of rotation is defined as forward rotation. As shown in FIG. 3, since the straight portion 24a of the presser spring 24 is engaged with the thread groove of the male threaded portion 22a of the drive shaft 22, the rotation of the drive shaft 22 causes the screw One side of the groove pushes the linear portion 24a forward, and the lens feeding member 18 holding the presser spring 24 is guided by the guide hole 18j and moves a predetermined distance in the axial direction of the drive shaft 22.

Note that the direction in which the lens feeding member 18 moves due to the forward rotation of the stepping motor 20 is defined as the forward direction.

Since the lens frame 14 is linked to the mounting portion 18a of the lens feeding member 18, the lens frame 14 is guided by the guide rod 12 and moves along the optical axis P. Along with this, the focus lens 16 held by the lens frame 14 also moves parallel to the optical axis P.

Next, when the signal input to the stepping motor 20 is stopped, the rotation of the drive shaft 22 is stopped, and the movement of the focus lens 16 is stopped.

Furthermore, when the input signal to the stepping motor 20 is reversed, the drive shaft 22 rotates in the opposite direction. When the drive shaft 22 is rotated in the reverse direction, the linear portion 24a is pushed forward by the surface of the thread groove on the opposite side to that in the above case. Then, the lens feeding member 18 moves in the opposite direction along the drive shaft 22, and together with this, the lens frame 14 and focus lens 16 move parallel to the optical axis.

By the way, as shown in FIG. 2, the linear portion 24a is fixed in the axial direction of the drive shaft 22 by the hooking portion 18g, the protruding portion 18d, and two spring retainers 18f. Therefore, the linear portion 24a does not shift with respect to the lens feeding member 18 when it is pushed in either the forward direction or the reverse direction.

Moreover, the straight portion 24a is pressed against the thread groove of the male threaded portion 22a by the restoring force of the presser spring 24, and is always in contact with both surfaces of the thread groove. Therefore, no backlash occurs between the straight portion 24a and the male threaded portion 22a, unlike in the case of screw connection.

Further, since the drive shaft 22 is pressed against the inner surface of the guide hole 18j by the straight portion 24a, no play occurs between the drive shaft 22 and the lens feeding member 18.

Therefore, when the stepping motor 20 is driven by the same angle in forward and reverse rotations, the lens feeding member 18 returns to its original position, so that optical hysteresis does not occur when the focus lens 16 moves forward and backward.

Furthermore, if the focus lens 16 is forcibly stopped during movement due to some external force, or if the focus lens 16 reaches the limit of its movement range and comes into contact with a stopper or the like, even though the lens feeding member 18 has stopped. First, there is a possibility that the stepping motor 20 may continue to be driven. In such a case, a force acts on the straight portion 24a from the side surface of the thread groove of the male threaded portion 22a, and this pushing force is greater than the restoring force of the presser spring 24 acting on the straight portion 24a. If it becomes larger, this straight portion 24a will curve, come off the thread groove, and engage with the adjacent thread groove. In other words, the lens feeding member 18
As the drive shaft 22 idles without moving,
Since the stepping motor 20 can continue to rotate, there is no risk of the screws getting stuck.

In addition, when assembling a camera, if the drive shaft 6 and lens feed member 7 are engaged in a screw relationship as in the past, the lens feed member 7 should be rotated and engaged with respect to the drive shaft 6. I had to let it happen.

However, as shown in FIG. 2, if the tip of the straight portion 24a is pressed with a fingertip or the like against the restoring force of the pressing spring 24,
The straight portion 24a is retracted from the range where the drive shaft 22 is located, so that the guide portion 18b can be easily inserted into and removed from the drive shaft 22. This saves the effort of attaching and detaching, and simplifies the assembly process.

In this embodiment, the lens feeding member 18 was used as a mechanism for moving the focus lens 16 of the AF device.
It can also be used with other moving lenses, such as zoom lenses.

Furthermore, in this embodiment, the motor is a stepping motor 20.
However, other motors, such as DC motors, may be used.

Incidentally, if it is necessary to change the rotation speed of the motor, the male threaded portion 22a is threaded on a main shaft provided separately from the drive shaft of the motor.

Further, in this embodiment, the presser spring 24 made of a torsion coil spring is used as the biasing means, and the straight portion 24a of the presser spring 24 is used as the engagement means. The wire may be pressed against the thread groove of the male threaded portion 22a by applying a restoring force such as a tension coil spring to the end.

Further, in this embodiment, the drive shaft 2 of the stepping motor 20
2, the lens feeding member 18 is loosely fitted as a driven member, but the driven member is a lens frame holding a photographing lens, and the main shaft is loosely inserted into a part of the lens frame.
The lens frame may be provided with an engaging means and an urging means. With such a configuration, the lens frame can be directly driven and a lens feeding member is not required, so that the number of parts can be reduced.

[Effects of the Invention] As explained above, according to the photographic lens driving device according to the present invention, the engaging means made of a wire is pressed against the thread groove of the male threaded portion formed on the main shaft, and the engaging means is connected to the driven member. Since the structure is such that the engaging means is pushed forward by the rotation of the main shaft, the driven member moves along the main shaft. Moreover, since the engaging means is pressed against both sides of the thread groove, it can move forward and backward according to the rotational direction of the main shaft.
There is no backlash or looseness between the engagement means and the male threaded portion. Therefore, optical hysteresis does not occur in the photographing lens that moves forward and backward in conjunction with the driven member.

Therefore, when the photographic lens is positioned at a predetermined position, the photographic lens is accurately positioned without being driven in a predetermined direction and then in the opposite direction, and a photograph in focus can be reliably taken.

When the engaging means is acted upon from the side surface of the thread groove (when the pressing force exceeds a predetermined value), the engaging means is pushed out of the thread groove, causing the main shaft to idle, and thus the driven member Even if the lens drive motor stops inadvertently and the lens drive motor continues to rotate, the male threaded portion and other parts will not be damaged.

Also, if the engaging means is retracted from the passage area of the main shaft,
Since the main shaft can be easily inserted into the guide hole,
The assembly process can be simplified, and manufacturing costs can also be reduced.

[Brief explanation of the drawing]

The drawings illustrate a preferred embodiment of the invention. FIG. 1 is a sectional view schematically showing a photographic lens driving device for a camera according to the present invention. FIG. 2 is a perspective view showing a driven member that is a part of this photographic lens driving device. Third
The figure is an enlarged sectional view showing a state in which the driven member and the main shaft are engaged. FIG. 4 is a sectional view corresponding to FIG. 1, schematically showing a conventional camera lens driving device. 14... Lens frame 16... Focus lens (photographing lens) 18...
Lens feeding member (driven member) 18b...guide portion
18j... Guide hole 20... Stepping motor (lens drive motor) 22... Drive shaft (main shaft) 2
2a... Male screw part 24... Presser spring (biasing means) 24a... Straight line part (engaging means) P... Optical axis

Claims (1)

[Scope of Claims] A photographic lens drive device for a camera that moves a photographic lens forward and backward along a main axis linked to a drive shaft of the lens drive motor by the rotation of a lens drive motor, comprising: a male thread formed on the main shaft; a driven member formed with a guide hole into which the main shaft is loosely inserted; and the male thread attached to the driven member and extending in a direction intersecting the main shaft, and formed on the main shaft. an engaging means made of a wire that engages with a thread groove of the external thread; and an urging means that presses the engaging means against the thread groove of the male thread, and the photographing lens is linked to the driven member. A photographing lens drive device for a camera, which is characterized by: