JP4590310B2 - Optical equipment - Google Patents

Description

The present invention relates to an optical apparatus that includes a moving device configured by using a rotating feed screw and a screw rack that meshes with the screw, and moves an optical system such as a lens in a straight line .

  An optical apparatus including a moving device using a feed screw and a screw rack is disclosed in Patent Document 1. This type of optical apparatus is configured to move the lens group in the optical axis direction by meshing between a female screw or a screw rack attached to the lens barrel frame and a feed screw driven by a driving source such as a motor.

  The important functions in this configuration are mainly the following three points. First, the rotational torque of the motor is efficiently converted into the propulsive force of the screw rack during normal feeding, or second, the screw rack when the optical equipment is shaken or when it receives an impact such as dropping. Doesn't “tooth jump” occur when the screw rack comes off from the feed screw, or thirdly, when the screw rack comes into contact with the end of movement, does not cause so-called “biting” that cannot be restored even if the feed screw is reversed? .

  Here, FIG. 4 shows the moving device disclosed in Patent Document 1. In FIG. 4, 11 is an actuator such as a stepping motor, 12 is a feed screw that is rotationally driven by the actuator 11, and 13 is a screw rack that meshes with the feed screw 12 and moves straight in the direction of arrow A or B as the feed screw 12 rotates. is there. Reference numeral 15 denotes a support, and a feed screw 12 is rotatably supported via a bearing member 16 between vertical support walls 15a and 15b at both ends. The actuator 11 is attached to one vertical support wall 15b with a screw 17.

  As shown in FIGS. 5 to 7 when viewed from the Z direction in FIG. 4, the screw rack 13 presses the feed dog 13a against the feed screw 12 by the spring force of the feed dog 13a contacting the feed screw 12 and a spring member (not shown). As a countermeasure against a drop impact when an impact in the pressing portion 13b and the screw rack moving direction is applied, a counter tooth 13c is provided so that the feed dog 13a does not get over the thread. Reference numeral 14 denotes a stopper (machine end) for limiting the movable range of the screw rack 13. Although only the left end stopper is shown in FIGS. 5 to 7, there is also a right end stopper (not shown).

  Next, the operation will be described. At the time of normal feeding, as shown in FIG. 5, since the thread of the feed screw 12 is stably meshed with the feed teeth of the screw rack 13, the pressing portion 13b sandwiches the feed screw 12 with a minimum force. When the optical device receives axial acceleration, the pinching force easily exceeds its pinching force, and the teeth 13c try to receive the acceleration at that time, thereby preventing tooth skipping. . Therefore, the opposing tooth 13c has a predetermined rigidity with respect to the feed dog 13a.

FIG. 6 shows the moment when the feed screw 12 rotates in the direction of arrow a and the screw rack 13 moves to the left in the figure and comes into contact with the stopper 14. When the feed screw 12 further rotates in the direction of arrow a from this state, as shown in FIG. 6, the thread of the feed screw 12 advances to the left, but the screw rack 13 does not move against the stopper 14, so the feed screw 12 Ride along the slope of the thread. At this time, the opposing tooth 13c also contacts the thread of the feed screw 2 and rides along the slope of the thread, and the distance between the feeding tooth 13a and the opposing tooth 13c of the screw rack 13 is elastically deformed and finally expanded. As shown in FIG. 7, the screw rack 13 reaches the point where the apex of the feed screw 12 and the apex of the feed tooth 13a of the screw rack 13 are in contact, and the screw apex of the feed screw 12 and the apex of the counter tooth 3c are in contact. The distance between the feed teeth 13a and the counter teeth 13c increases.
Japanese Patent Laid-Open No. 9-258087

  In the above conventional example, since the screw rack 13 is elastically deformed beyond the rigidity between the opposing teeth 13c and the feed teeth 13a, the pinching force of the feed screw 12 becomes an unexpected magnitude and a large frictional force is generated. . Therefore, if the rotation of the feed screw 12 once stops in the state of FIG. 7, a biting phenomenon has occurred in which it cannot be moved only by the force of the actuator 11 at the time of restart.

  Here, the problems of the moving device using the conventional feed screw will be described in detail from the viewpoint of the thread shape of the feed screw.

  First, normal feeding will be described. A mechanism in which the rotational torque of the feed screw efficiently provides a driving force is preferable. During normal operation, the thread of the screw rack and the feed screw mesh with each other, and the advance force of the feed screw is divided on the slope of the screw thread. If this is a screw thread with a small apex angle, it is divided in the axial direction as the propulsive force. The force applied is large, and the force applied in the radial direction is small. Therefore, the pinching force with respect to the feed screw for assuring a stable engagement may be small, and there is little unnecessary friction loss, and the efficiency is high. On the other hand, threads with a large apex angle have the opposite characteristics.

  Next, a drop impact countermeasure (tooth skip countermeasure) will be described. When a drop or impact is applied to the apparatus, axial acceleration is generated, which is transmitted to the thread of the screw rack, and the thread having a large apex angle is easily disengaged, so-called tooth skipping is likely to occur. In order to prevent this, the pinching force is increased so as to withstand a predetermined acceleration, or opposed teeth that engage with the screw thread only when dropped on the opposite side of the screw rack feed screw are provided.

  However, when the pinching force is increased, the mechanical loss during feeding increases and the efficiency decreases. In addition, providing opposing teeth on the screw rack has led to an increase in the size of the screw rack.

  Lastly, we will discuss countermeasures against bite. At the end of the movement of the screw rack, the gap between the feed dog and the counter teeth is widened when the stopper collides, and biting occurs. In other words, since there is an opposing tooth originally added as a countermeasure against the drop impact described above, biting occurs as a side effect at the end of movement. Therefore, for example, a portion having no thread is provided at the end of the feed screw to prevent this. However, as a side effect, an extra machining step may be added to the feed screw, which may raise costs.

  As described above, the conventional moving device using the feed screw does not consider the improvement of the thread of the feed screw, so that a side effect due to a certain measure occurs and a measure is added.

(Object of invention)
An object of the present invention is to provide an optical apparatus capable of realizing an increase in efficiency during feeding, tooth skipping during a drop impact, and prevention of biting at the end of movement while achieving downsizing.

In order to achieve the above-mentioned object, the present invention engages with a screw-shaped first member rotatably supported and a thread of the first member, and the first member is rotated by the rotation of the first member. An optical device that includes a moving device configured by a screw-shaped second member that moves in the axial direction of the member, and that moves the optical system in the optical axis direction in conjunction with the movement of the second member ; The thread shape of the thread appearing in the axial cross section of the first member has two different apex angles: a first slope on the root side of the thread and a second slope on the tip side of the thread. The first slope is smaller than the second slope, and the second means is provided with stopper means provided to limit the axial movement of the second member. an optical device having a guide portion for moving the member to the outer diameter direction of said first member Is shall.

According to the present invention, it is possible to provide an optical apparatus capable of realizing an increase in efficiency at the time of feeding, tooth skipping at the time of a drop impact, and prevention of biting at a moving end while achieving downsizing.

  The best mode for carrying out the present invention is as shown in the following examples.

  1 to 3 are views showing a moving device according to an embodiment of the present invention. Specifically, FIG. 1 is a sectional view in the axial direction of a feed screw in a normal feeding state, and FIG. FIG. 3 is a cross-sectional view showing a state at the end of movement.

  In these figures, 2 is driven by a motor (not shown) (corresponding to the actuator 11 shown in FIG. 4) which is given a predetermined pulse by a control circuit (not shown) and rotates in the forward or reverse direction by a corresponding rotation angle. Each screw thread, which is a so-called male screw, is composed of two different apex angle ridges, and the root side of the thread (close to the valley) The first slope 2a is a so-called trapezoidal mountain having an apex angle θ1 of about 30 degrees. Further, the slope on the tip side (the side closer to the outer diameter side) of the screw thread is the second slope 2b, and here, the apex angle θ2 is a triangular mountain shape of about 70 degrees. 2c is the apex of one thread.

  Reference numeral 3 denotes a screw rack which is a screw-like second member, which is made of a lubricated metal or a resin material having a good sliding property and meshes with the first inclined surface 2a of the feed screw 2 at an appropriate inclined surface. As the teeth 3a mesh with each other and the feed screw 2 rotates, the screw rack 3 is moved in the axial direction. When the rotation direction of the feed screw 2 is in the direction of the arrow a, the screw rack 3 is fed leftward in FIG. An optical device (not shown) is configured such that a lens frame (not shown) moves in conjunction with the linear movement of the screw rack 3. Reference numeral 3b denotes a pressing portion sandwiched by the feed screw 2 and pressed by a spring or the like, and stably feeds the feed dog 3a to the thread of the feed screw 2.

  4 is a stopper which is a stopper means for determining the limit of the axial movement of the screw rack 3, and 4a is a cam portion which is a guide portion. 3c is a follower part, and is in a position where it abuts on the cam part 4a at the end of the movement of the screw rack 3, and has a shape that can smoothly ride on the slope of the cam part 4a. In FIG. 1, the screw rack 3 has four feed dogs, but the number thereof is not limited and may be, for example, one tooth. Here, the feed dog 3a is an example of a rack in which the screw engagement pitch is not a circle but a straight line, but may be a part of a so-called female screw having a normal engagement pitch circle. Further, in the example, the stopper means for determining the limit of the axial movement of the screw rack is shown only in the left end portion in the figure, but a stopper having the same shape may be provided in the right end portion.

  Next, the operation of the mobile device having the above configuration will be described. In the case of normal movement, the screw rack 3 moves from right to left or from left to right in the figure while the feed dog 3a meshes with the first slope 2a of the trapezoidal mountain shape by forward and reverse rotation of a motor (not shown). At this time, assuming that the screw thread of the feed screw 2 has a force F to advance, F ′ which is divided by the first inclined surface 2a of the screw thread and becomes Fcos θ1 is transmitted to the screw rack 3. The When this F ′ is divided into an axial force and a radial force, a force for pushing the screw rack 3 in the outer radial direction is generated. The clamping force of the pressing portion 3b to the feed screw 2 is set so as to resist the force in the outer diameter direction of the feed screw 2 generated by the inclination angle of the first slope 2a of the thread of the feed screw 2. Accordingly, since the force generated on the mountain-shaped slope having a small apex angle such as the first slope 2a is small, the clamping force can be small.

  On the other hand, when the apparatus is dropped or swung around rapidly in this state, when acceleration in the direction coaxial with the feed screw 2 is applied to a lens frame (not shown) or the like, the first inclined surface 2a has a trapezoidal mountain shape and the apex angle is about 30. Even if an excessive force is applied, the screw rack 3 has a small component force in the outer diameter direction of the feed screw 2, so that the engagement between the feed screw 2 and the screw rack 3 is difficult to come off.

  Next, even if the follower portion 3c comes into contact with the cam portion 4a of the left stopper 4, which is one end of the moving range, as shown in FIG. 3 further proceeds from the state of FIG. 1 to the left in the figure.

  Then, as shown in FIG. 2, the follower portion 3c of the screw rack 3 rides on the cam portion 4a and moves the entire screw rack 3 to the outer diameter side of the feed screw 2 against the pinching force of the pressing portion 3b. Therefore, the mesh between the feed dog 3a and the first inclined surface 2a is released, and the thread of the feed dog 3a moves onto the second inclined surface 2b. Here, since the apex angle of the second inclined surface 2b is about 70 degrees, the component force in the outer diameter direction of the feed screw 2 is larger than that of the first inclined surface 2a, and the rotational load due to riding is not large.

  Eventually, as shown in FIG. 3, when the follower portion 3c comes into contact with the vertical surface of the stopper 4 and the movement of the screw rack 3 in the left-right direction stops, this is detected by a stop position detection signal by a sensor means (not shown) It is detected by a timer means or the like, and is controlled so that the rotation of a motor (not shown) is stopped by this detection signal.

  However, in the unlikely event that the feed screw 2 continues to rotate due to troubles such as the control circuit and sensor means described above, the feed dog 3a of the screw rack 3 moves over the second slope 2b of the thread of the feed screw 2. The screw rack 3 moves upward in FIG. 3 due to the component force in the outer diameter direction of the feed screw 2, and eventually, when the feed dog 3a passes the apex 2c, again to the second inclined surface 2a of the next thread. Repeat the vertical movement of moving. At that time, the follower portion 3c that has been in contact with the vertical surface of the stopper 4 smoothly moves up and down. That is, no biting phenomenon occurs.

  Thereafter, when the control circuit or the like returns to a normal state and the feed screw 2 rotates in the reverse direction, the screw rack 3 starts to move in the right direction by the returning operation in the order shown in FIGS.

  It will be described that the moving device having such a configuration is highly efficient and small in size and can cope with a drop impact.

  First, it is a chevron having two different apex angles θ 1, θ 2 appearing in the axial cross section of the thread of the feed screw 2, and second, the screw rack 3 and the feed at the end of the movement of the screw rack 3. It has a mechanism for disengaging the screw 2 (in other words, a cam portion 4a that moves the screw rack 3 in the outer diameter direction of the feed screw 2), and thirdly, the screw rack 3 has no opposing teeth. is there.

  According to the above configuration, it is possible to assign a function suitable for the feed characteristics coming from each angle due to the difference in the inclination of the top angle of the screw thread. That is, in normal feeding, feeding is performed with a trapezoidal chevron that allows stable feeding even if the axial pinching force is weak, so that the rotational force transmitted from the feed screw 2 is not impaired and mechanical feeding is reduced and efficient. I can do it.

  In addition, since the trapezoidal mountain shape is used, the screw rack 3 is unlikely to be detached from the feed screw 2 at the time of a drop impact that generates acceleration in the axial direction. Since it is not necessary to provide teeth, the screw rack 3 can be reduced in size.

  Further, at the end of the movement of the screw rack 3, it has a mechanism (cam portion 4a) for releasing the engagement between the screw rack 3 and the feed screw 2 and has no fixed opposing teeth, so that it can be fed in a trapezoidal chevron. It is possible to disengage smoothly even during the operation.

  Further, if the thread is formed only with the trapezoidal tooth profile, the top of the thread cannot be formed, and a cylindrical shape with the maximum outer diameter is formed. However, when the screw rack 3 rides on this portion, a frictional force is generated. Since the radius becomes the maximum, it is difficult to return, but since it has a triangular mountain shape (second apex angle θ2) in the middle of the slope of the screw thread, the return after riding is immediately performed.

  As described above, in the moving device of the present embodiment constituted by the rotating feed screw 2 and the screw rack 3 meshing with the screw, the thread of the feed screw 2 is determined from two types of apex angles θ1, θ2 (> θ1). Since it is fed using a slope with a small apex angle (first slope 2a), it is possible to reduce the pinching force of the feed screw 2 and achieve highly efficient feeding. Since the screw rack 3 is not easily detached from the feed screw 2 even during a drop impact, a small screw rack 3 having no opposing teeth can be obtained. Further, since the screw rack 3 has a mechanism (a stopper 4 having a cam portion 4a) that pushes the screw rack 3 toward the outer diameter side of the feed screw 2 at the terminal end of the movement of the screw rack 3, the bite does not occur. And so on.

  As described above, a moving device capable of increasing efficiency during feeding, measures against tooth skipping during a drop impact, preventing biting at the end of movement, and miniaturizing a screw rack, and an optical apparatus equipped with the moving device. be able to.

  In the above embodiment, the apex angle θ1 of the first inclined surface 2a on the base side of the screw thread is about 30 °, and the apex angle of the second inclined surface 2b on the tip side is about 70 °. If the apex angle θ1 of the first inclined surface 2a is smaller than the apex angle θ2 of the second inclined surface 2b on the tip side, the present invention is not limited to this.

It is a block diagram which shows the moving apparatus concerning one Example of this invention. It is sectional drawing which shows the terminal vicinity of a movement in the moving apparatus shown in FIG. It is sectional drawing which shows the mode in the terminal of movement in the moving apparatus shown in FIG. It is a perspective view of the conventional moving apparatus. It is sectional drawing which shows the axial direction of the moving apparatus of FIG. FIG. 5 is a cross-sectional view showing the axial direction of the moving device of FIG. 4. FIG. 5 is a cross-sectional view showing the axial direction of the moving device of FIG. 4.

Explanation of symbols

2 Lead screw (screw-shaped first member)
2a 1st slope of a thread 2b 2nd slope of a thread 3 Screw rack (screw-like 2nd member)
3a Feed dog 3b Pressing part 3c Followers part 4 Stopper (stopper means)
4a Cam part (guide part)

Claims (1)

A screw-shaped first member rotatably supported, and a screw-shaped second member that meshes with the thread of the first member and moves in the axial direction of the first member by the rotation of the first member. In an optical device that includes a moving device configured to move the optical system in the optical axis direction in conjunction with the movement of the second member ,
The thread shape of the thread appearing in the axial cross section of the first member has two different apex angles: a first slope on the root side of the thread and a second slope on the tip side of the thread. The apex angle of the first bevel is smaller than the apex angle of the second bevel,
An optical device characterized in that a guide means for moving the second member in the outer diameter direction of the first member is provided in stopper means provided to determine the limit of the axial movement of the second member. Equipment .

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