JP2011034608A - Lens driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens driving device capable of suitably avoiding the occurrence of biting. <P>SOLUTION: The lens driving device 1 includes: a stepping motor 10; a lead screw 20; and a movable part 2 constituted of a screw member 30 screwed movably in an axial direction by rotation of the lead screw 20, a holding means 50 holding a lens and movably engaged by movement of the screw member 30 and an elastic member 40 provided at an engaging part of the holding part 50 and the screw member 30 and biasing the screw member 30. Thus, biting of the screw member 30 in the lead screw 20 can be suitably avoided when the movable part 2 abuts against an end of a movable range. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technical field of a lens driving device that is used in, for example, an optical pickup of an optical disk device and drives a lens in an optical axis direction.

  In recent years, in order to increase the recording capacity of an optical disc, a multi-layer disc configuration having a plurality of recording layers in one disc has been used. According to such a multilayer disc configuration, a plurality of recording layers are arranged at a predetermined interval in the thickness direction of the disc. For this reason, spherical aberration occurs when the data recording or reproducing position moves from one recording layer to another recording layer.

  For the purpose of correcting this spherical aberration, some optical pickups in the optical disc apparatus are provided with a lens driving device capable of driving a lens for correcting spherical aberration in the optical axis direction. Such a lens driving device is generally configured to include a lead screw and a nut that are rotated by a stepping motor capable of changing a rotation speed. According to this configuration, the spherical aberration can be corrected by mechanically adjusting the lens position for correcting the spherical aberration. Examples of the configuration of the lens driving device include those shown in Patent Documents 1 and 2, for example.

  In such a lens driving device, the nut and the holding frame of the lens movably connected to the nut move together with the rotation of the lead screw installed so that the rotation axis is parallel to the optical axis direction. It is configured.

Japanese Patent Laid-Open No. 2004-170753 JP 2007-265597 A

  By the way, in the lens driving device including the lead screw and the nut described above, even if the movable portion constituted by the nut and the lens holding frame and the lens movably connected together with the nut reaches the end of the movable range. When the driving of the stepping motor is continued, the nut hits a stopper at the end of the movable range and the nut is screwed into the lead screw.

  At this time, the lens driving device is driven by changing the rotation direction of the stepping motor in the reverse direction so that it returns from the abutment (that is, the movable portion moves in the opposite direction to the end of the movable range). However, when the frictional force between the nut and the lead screw is larger than the rotational force of the stepping motor, the movable part cannot be moved and cannot be restored. There is a technical problem that so-called biting occurs.

  For the technical problem of such biting, for example, in Patent Document 1 described above, a protrusion is provided on the surface of the nut that contacts the stopper, and the area of the contact surface is reduced so that the frictional force at the time of abutment is reduced. Has been disclosed to effectively reduce the occurrence of the bite and to avoid the occurrence of biting.

  Further, in Patent Document 2, a state in which a nut is caught is detected by an operation sensor, and when the biting is released, the stepping motor is driven with a relatively low driving frequency and is relatively high. A configuration for releasing the biting by torque is disclosed.

  However, if the movable part hits while the stepping motor is driven at a relatively high torque, the nut will be screwed into the lead screw at a higher torque, and the torque required for recovery There is a technical problem that increases and makes it difficult to release the bite.

  In addition, due to the structure of the stepping motor, even when the stepping motor is driven at a higher torque to release the biting, there is a possibility that the tightening of the nut may occur and the nut bites deeper. There is a risk of getting in.

As described in Patent Document 2, a lens driving device is usually provided with a position sensor for detecting at least the position of a nut relative to the end of the movable range or the position of a lens frame, and the occurrence of biting occurs. It is preventing. However, even with such a configuration, it is impossible to completely deny the possibility of biting due to the malfunction of the position sensor and the control circuit of the lens driving device.
Originally, in stepping motors where the nut position should be able to be grasped by the number of drive pulses, if application of drive pulses that are normally aware of the movable range, biting at the end should not occur, but for this purpose, It is necessary to know where the nut is when the power is turned on. When there is a position sensor as in Patent Document 2, the nut position can be grasped by the position sensor at the time of initialization, and therefore it is usually possible to prevent biting at the end of the movable range.

  On the other hand, in a configuration that does not include such a position sensor, for the initial positioning, the stepping motor is continuously driven in a certain direction, and the movable part is abutted against a stopper or the like at the end of the movable range, thereby allowing the stepping motor to A technique is used in which step-out is caused and the nut is at the end of the movable range at the end of driving.

In this case, there is a possibility that the nut is caught at the end of the movable range every time during initialization.
Since there is no way to determine which excitation state caused the contact to step out, even if the stepping motor is driven in reverse to return from the contact, it initially acts in the tightening direction. there is a possibility.

  In Patent Document 2, it is described that the drive is performed with a higher torque at the time of return from the butting, but since there is no way to specify the state to be excited at the time of the return, additional tightening occurs at a high torque at the beginning of the return. It may become impossible to return.

  The present invention has been made in view of, for example, the conventional problems described above, and even when there is no position sensor, it is relatively easy to avoid the occurrence of nut biting with a relatively simple configuration. It is an object to provide a lens driving device that can be implemented.

  In order to solve the above-described problems, a lens driving device according to the present invention includes a lead screw, a stepping motor that rotates the lead screw, and a screw that is screwed into the lead screw. A screw member that is movable in the axial direction, a holding unit that holds the lens and is movably engaged with the movement of the screw member, and an engaging portion between the holding unit and the screw member. And an elastic member that urges the screw member.

  The operation and other advantages of the present invention will become apparent from the embodiments described below.

It is a schematic diagram which shows the basic composition of the lens drive device of a present Example. It is a schematic diagram which shows the aspect of the excitation of the stepping motor at the time of abutting. It is a schematic diagram which shows the aspect of the excitation of the stepping motor at the time of abutting. It is a schematic diagram which shows the basic composition of the lens drive device of a present Example. It is a graph which shows the drive torque and nut rotation amount of the stepping motor of a present Example. It is a graph which shows the drive torque and nut rotation amount of a stepping motor based on the modification structural example of the lens drive device of a present Example. It is a schematic diagram which shows the modification structural example of the lens drive device of a present Example.

  An embodiment of the lens driving device according to the present invention includes a lead screw, a stepping motor that rotates the lead screw, and a screw that engages with the lead screw, and moves in the axial direction of the lead screw as the lead screw rotates. A holding member that holds the lens and is movably engaged with the movement of the screw member, and an engaging portion between the holding unit and the screw member. And a movable part configured to include an elastic member that biases the moving member.

  According to the embodiment of the lens driving device of the present invention, the lead screws are joined to each other so as to be rotatable by the rotational drive of the stepping motor. For example, a screw member such as a nut is screwed onto the lead screw, and the screw member is engaged with a holding means such as a lens frame that holds the lens. Here, the screw member is engaged so as not to rotate, for example, at the engaging portion with the holding means, and therefore, when the lead screw rotates, it can move in the axial direction of the lead screw according to the rotation. It is configured. The holding means is configured to be movable in accordance with the movement of the screw member. Therefore, in accordance with the driving of the stepping motor, the movable part configured to include the screw member, the elastic member, and the holding means and the lens held by the holding means are configured to be movable in the axial direction of the lead screw.

  Typically, the lens held by the holding unit is a spherical aberration correction lens, and the lens driving device including the spherical aberration correction lens is provided in an optical pickup of the optical disc apparatus. For example, when the recording layer is switched in recording data on a multilayer optical disc, the spherical aberration correction lens is moved on the optical axis in accordance with the change of the focal position, thereby suppressing the influence of the spherical aberration in the optical pickup. It becomes possible.

  By the way, in the lens driving device having such a configuration, when the movable portion moves, the lens drive device hits the end of the movable range, and technically occurs in the screwed portion between the screw member and the lead screw constituting the movable portion. Problems have been pointed out.

  Normally, the lens driving device is provided with a position sensor, and the movement is controlled while appropriately detecting the position of the movable part so that the movable part moves beyond the movable range and does not hit. However, the possibility that the movable part hits the end of the movable range due to an unexpected situation such as a failure of the position sensor or an error in movement control cannot be completely denied.

  Further, when the movable portion hits the end of the movable range with a relatively high torque, the screwed portion between the lead screw and the screw member is tightened more strongly, and higher torque is required at the time of return. In addition, when the torque necessary for returning from the abutting exceeds the upper limit of the driving torque of the stepping motor, there is a possibility that the abutting cannot be restored and the subsequent lens driving operation cannot be performed.

  In the embodiment of the lens driving device of the present invention, an elastic member that urges the screw member is provided particularly at the engaging portion between the screw member and the holding means. The elastic member is, for example, a leaf spring joined to the holding means, and is configured to engage with the screw member and urge the elastic member in the opposite direction to the rotation of the screw member. .

  In general, when the screw member moves in accordance with the rotation of the stepping motor, the screw member is engaged with the holding means so as not to rotate on the lead screw in accordance with the rotation. However, if the movable part hits the end of the movable range, the screw member cannot move any more, but if the stepping motor continues to drive in the direction in which the screw member hits the end of the movable range, the lead Try to start rotating on the screw. Usually, the holding means has a structure that restrains a protrusion provided on the screw member so that the screw member does not rotate at an engaging portion with the screw member. In the present embodiment, the engaging portion of the holding means with the screw member may be an elastic member such as a leaf spring that biases the elastic member in the direction opposite to the rotation of the screw member.

  The elastic member is deformed by the rotational force of the screw member when it abuts the end of the movable range of the movable part. For example, in an elastic member using a leaf spring as described above, deflection occurs due to the rotational force of the screw member when the movable part hits. In the lens driving device of this embodiment configured as described above, preferably, the stepping motor steps out and the rotation of the lead screw stops in a state where the rotational force of the screw member and the elastic force of the elastic member are balanced. The rotation of the screw member stops. It is preferable that the driving torque of the stepping motor, the spring constant of the elastic member, and the like are adjusted so as to satisfy such a condition.

  In addition, since the elastic member is structured to urge in the direction opposite to the rotation of the screw member at the end of contact, the stepping motor is driven to rotate in the direction opposite to that at the end of the movable part in order to return from the contact. A force due to the bias is applied to the rotation. For this reason, it is possible to perform the return from the abutment with a torque relatively higher than the driving torque of the stepping motor.

  As described above, according to the lens driving device of the present embodiment, the urging force of the elastic member is added to the driving torque of the stepping motor when returning from the state in which the nut is screwed into the lead screw due to the contact. The screw member moves with a relatively high torque. Thus, since the driving torque at the time of return can be increased compared to the driving torque at the time of abutment, it is easy to avoid the occurrence of biting.

  Further, by utilizing the fact that the return from abutment can be realized with a relatively high torque, for example, the positioning of the screw member at the start of the lens driving device is abutted against one movable end. It is also possible to carry out with. With this setting, for example, the initial position at the time of startup can be determined without using a configuration such as a position detection sensor for detecting the position of the screw member, and hence the lens frame and the lens. . For this reason, it becomes possible to make the structure of an apparatus simpler, and it is useful from a cost aspect.

  One aspect of the embodiment of the lens driving device according to the present invention is that when the movable portion hits an end of a predetermined movable range, the rotational force of the screw member due to the driving torque of the stepping motor is elastic of the elastic member. The screw member stops rotating at a position that balances the force.

  According to this aspect, when the movable portion hits the end of the movable range and rotation of the screw member is started, the rotational force of the screw member and the elastic force of the elastic member biased against the screw member are generated. At the balanced position, the stepping motor steps out and the rotation of the lead screw stops, so that the rotation of the screw member stops. In other words, elements that define the elastic force such as the driving torque of the stepping motor of this aspect and the spring constant of the elastic member are designed to satisfy the above-described conditions.

  According to another aspect of the embodiment of the lens driving device of the present invention, the lens driving device further includes a control unit that controls a driving signal of the stepping motor, and the control unit is configured so that the movable unit hits an end of a predetermined movable range. And the driving signal of the stepping motor is controlled so as to change the driving torque of the stepping motor at least one of when the movable portion returns from the end portion.

  According to this aspect, the driving torque of the stepping motor when the movable portion abuts against the end of the movable range and the driving torque of the stepping motor when the movable portion returns from abutment are different from each other. The signal is controlled.

  For example, as will be described later, by reducing the driving torque of the stepping motor relatively when the movable portion hits, the amount of rotation of the screw member when the stepping motor steps out can be reduced. For this reason, when returning from the butting, even if the stepping motor is further excited in the direction of rotating the screw member, the screw member can be rotated (that is, the elastic member can be deformed), and then in the return direction. As the driving continues, normal recovery is possible, and the occurrence of biting can be avoided relatively easily. On the other hand, by making the driving torque at the time of return from the butting relatively high, it is possible to avoid the occurrence of biting in a relatively easy manner.

  As for the control of these drive torques, if at least one of the control to lower the torque at the time of abutment and the control to increase the torque at the time of return from the abutment is performed, as described above, A relatively easy return can be performed. Moreover, it becomes possible to enjoy an effect more notably by carrying out both at the time of butting and at the time of return.

  In another aspect of the embodiment of the lens driving device of the present invention, the control means controls the driving torque of the stepping motor by changing the current or voltage of the driving signal supplied to the stepping motor.

  According to this aspect, the intensity of excitation of each of the plurality of electromagnets provided in the stepping motor typically changes as the current flowing through the stepping motor changes. For this reason, the torque of the rotor changes.

  According to such a configuration, for example, a plurality of current sources having different current values are prepared, and the control unit is configured to be able to appropriately select a current source that supplies current to the stepping motor among these current sources. Thus, the driving torque of the stepping motor can be controlled.

  As described above, according to this aspect, the driving torque of the stepping motor can be controlled relatively easily.

  In general, since the resistance value of the electromagnet inside the stepping motor is generally constant, it is clear that the drive current can be changed by changing the drive voltage. For this reason, the control means can suitably control the driving torque of the stepping motor even by changing the driving voltage.

  As described above, according to this aspect, the driving torque of the stepping motor can be controlled relatively easily.

  In another aspect of the embodiment of the lens driving device of the present invention, the control means controls the driving torque of the stepping motor by changing the excitation method of the stepping motor.

  According to this mode, the mode of excitation of the plurality of electromagnets provided in the stepping motor by, for example, the operation of the control means is, for example, one-phase excitation, two-phase excitation, and one-phase two-phase excitation alternately performed 1-2. Changed to either phase excitation.

  For example, compared to single-phase excitation, the stepping motor's torque is higher because the rotor of the stepping motor receives a relatively strong force in driving with two-phase excitation in which twice as many electromagnets are excited at a time. Become.

  According to such a configuration, for example, the stepping motor is normally driven by one-phase excitation, and the stepping motor excitation mode at the time of return from abutment is changed to two-phase excitation, so that at the time of abutment It is possible to return from the abutment with a torque equal to or greater than the driving torque. For this reason, it becomes possible to avoid generation | occurrence | production of biting more suitably.

  As described above, according to this aspect, the driving torque of the stepping motor can be controlled relatively easily. For this reason, it is possible to enjoy the various advantages described above.

  In another aspect of the embodiment of the lens driving device of the present invention, the control means controls the driving torque of the stepping motor by changing the driving frequency of the stepping motor.

  According to this aspect, the driving frequency of the stepping motor is configured to be controllable by the operation of the control means, and the driving torque is configured to change in accordance with the change in the driving frequency. For example, the driving torque is increased by lowering the driving frequency of the stepping motor, and the driving torque is lowered when the driving frequency is relatively increased.

  By the way, in a lens driving device using a feeding device using a stepping motor as in this embodiment, a so-called trapezoidal control driving profile is generally employed. In other words, the driving frequency gradually increases (in other words, the driving speed increases) at the start of driving the stepping motor, and when the predetermined driving frequency is reached, the driving frequency is switched to constant frequency driving, and the frequency gradually decreases (in other words, when stopped). For example, the driving mode is controlled so that the driving speed is decelerated).

  In such trapezoidal control, when the movable part hits the end of the movable range during the period of driving while gradually decreasing the frequency, the screw member is screwed into the lead screw with a relatively high torque.

  In particular, as described above, when the position detection means for the movable part such as a sensor is not mounted and the movable part is abutted against the end of the movable range and the initial positioning is performed, the end of the movable range When it is abutted against the part, the driving frequency for stopping is reduced, so that a high torque is generated and the screw member is screwed into the lead screw more deeply.

  In this aspect, the drive frequency may be changed by temporarily changing a part of the drive profile related to the drive frequency of the stepping motor such as trapezoidal control. For example, at the time of initial position setting, when the movable part hits the end of the movable range and stops, it may be controlled to stop from a high drive frequency and low torque state so as not to decrease the drive frequency. good.

  As described above, according to this aspect, the driving torque of the stepping motor can be controlled relatively easily. For this reason, it is possible to enjoy the various advantages described above.

  As described above, in the aspect in which the control means controls the driving frequency of the stepping motor, the control means places the movable part in a direction opposite to one end of a predetermined movable range when driving the stepping motor. After the fixed amount of movement, the position of the movable part may be detected by moving the movable part to the end of the movable range.

  With such a configuration, it is preferable that the movable portion hits the end of the movable range during acceleration when the stepping motor is activated, even in a configuration including a stepping motor that is driven based on a so-called trapezoidal control drive profile. Can be avoided. For this reason, it is possible to suitably prevent the screw member from being screwed into the lead screw in a state where the drive frequency is increasing, the drive frequency is relatively low, and the torque is high.

  It should be noted that the amount of movement when moving the movable part in the direction opposite to the end of the abutting movable range is preferably a distance corresponding to a period required for increasing the drive frequency in the trapezoidal control of the stepping motor.

  In another aspect of the embodiment of the lens driving device of the present invention, the control means changes the driving mode of the stepping motor to that based on PWM (Pulse Width Modulation) control, thereby driving the driving torque of the stepping motor. To control.

  According to this aspect, in the typical system, the control means changes the driving mode of the stepping motor at the timing at which the movable portion hits the end of the movable range to that based on PWM control. Generally, in PWM control, it is possible to artificially lower the drive voltage by changing the duty ratio of the pulse wave that controls the driving of the stepping motor. However, in this aspect, by adjusting the duty ratio in the PWM control under the control of the control means, the driving voltage of the stepping motor can be changed in a pseudo manner and the driving torque can be changed.

  As described above, according to this aspect, the driving torque of the stepping motor can be controlled relatively easily. For this reason, it is possible to enjoy the various advantages described above.

  In another aspect of the embodiment of the lens driving device of the present invention, the elastic member is configured such that the movable portion is at the end of the movable range as compared to before the movable portion contacts the end of the predetermined movable range. The spring constant of the site | part biased with respect to the said screw member after contacting a part is comprised so that it may become small.

  In the present embodiment, when the screw member moves in accordance with the rotation of the stepping motor, the elastic member biases the screw member so as not to rotate with a relatively large spring constant.

  On the other hand, if the stepping motor continues to rotate in the direction in which the screw member abuts against the end of the movable range after the movable portion hits the end of the movable range, the spring constant of the portion urged by the elastic member Becomes relatively small.

  The spring constant of the elastic member at this time is preferably set according to the driving torque of the stepping motor. Further, the rotation of the screw member at this time stops at a position where the rotational force generated by the driving torque of the stepping motor and the elastic force of the elastic member are balanced.

  That is, when the spring constant of the elastic member is small, the difference in the rotation amount of the screw member due to the difference in driving torque is large. Thus, when the movable part returns from the end of the movable range, the driving torque of the stepping motor is controlled so as to be relatively higher than when the movable part hits the end. Even if the stepping motor is excited in the direction in which the screw member rotates, the screw member can be easily rotated because the increase in the elastic force of the elastic member is small, and then the normal return can be achieved by continuing the drive in the return direction. It becomes possible to avoid the occurrence of biting relatively easily.

  Various configurations for changing the spring constant of the elastic member before and after the movable portion contacts the end of the movable range will be described below.

  As described above, in a mode in which the spring constant of the elastic member is reduced before and after the movable portion hits the end of the movable range, the elastic member includes a plurality of spring members that urge the screw member. By changing the number of spring members biased against the screw member, the spring constant of the portion biased against the screw member after the movable portion contacts the end of the movable range is changed. You may be comprised so that it may become small.

  If comprised in this way, when a movable part collides with the edge part of a movable range, some will not contact a screw member among elastic members, such as a several leaf | plate spring etc. which are urged | biased to this screw member, for example For example, the biasing is not performed.

  For example, when the screw member is moved in accordance with the rotation of the stepping motor, the movable portion is end of the movable range in the configuration in which the screw member is urged not to rotate by the two leaf springs. The spring constant of the part to be urged is reduced by detaching one leaf spring from the screw member when it abuts the portion.

  For this reason, it is possible to suitably change the spring constant of the elastic member before and after the movable portion contacts the end of the movable range.

  Further, in a mode in which the spring constant of the elastic member becomes small before and after the movable portion hits the end of the movable range, the elastic member is used to rotate the spring member and the lead screw that urge the screw member. A stopper member that suppresses the rotation of the screw member is provided, and the stopper member does not suppress the rotation of the screw member after the movable portion contacts the end of the movable range.

  According to this aspect, when the screw member is moved according to the rotation of the stepping motor, the elastic member is supported by the stopper member so as not to be deformed or moved according to the rotation of the screw member. Yes. On the other hand, after the screw member hits the end of the movable range, the support by the stopper member is released, and the elastic member is deformed or moved according to the rotation of the screw member.

  If comprised in this way, it will become possible to change the spring constant of an elastic member suitably before and after a movable part contacts the edge part of a movable range.

  In another aspect of the embodiment of the lens driving device of the present invention, the screw member is configured such that a contact portion with the elastic member changes before and after the movable portion hits an end of the movable range. The spring constant of the portion where the elastic member urges against the screw member decreases with the change of the contact portion.

  According to this aspect, for example, the contact portion between an elastic member such as a leaf spring and a screw member such as a nut is configured to change before and after the movable portion hits the end of the movable range.

  For example, when the stepping motor further rotates in a direction in which the movable portion abuts against the end of the movable range after the movable portion comes into contact with the end of the movable range, the screw member of this aspect is The shape is such that the contact position changes. Specifically, among the plurality of protrusions provided on the contact surface of the screw member with the elastic member, the one protrusion that is in contact with the elastic member is typically compared to the one protrusion. Is designed so as to come into contact with the elastic member at the other projection part which is far from the fulcrum of the elastic member which is a leaf spring.

  According to such a screw member, the lever ratio of the elastic member changes before and after contact with the end of the movable range of the movable portion, and the spring constant of the elastic member becomes small.

  If comprised in this way, it will become possible to change the spring constant of an elastic member suitably before and after a movable part contacts the edge part of a movable range.

  As described above, the embodiment according to the lens driving device of the present invention includes the lead screw, the stepping motor, the screw member, the holding means, and the elastic member.

  Accordingly, it is possible to relatively increase the torque of the screw member when the movable portion returns from the abutment, and it is possible to relatively easily and reliably avoid the occurrence of biting.

  Embodiments of the present invention will be described below with reference to the drawings.

(1) Basic Configuration Example First, a basic configuration example of the lens driving device of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram showing the basic configuration of the lens driving device of the present invention.

  In the lens driving device 1 of this embodiment, for example, a nut 30 engaged with a lens frame 50 that holds a lens 70 for correcting spherical aberration moves as the lead screw 20 rotates as the stepping motor 10 is driven. Thus, the lens 70 is moved.

  The stepping motor 10 is configured to be able to rotate the lead screw 20 connected to the rotation shaft of the stepping motor 10 by driving.

  The lead screw 20 is installed so that the optical axis direction of the laser beam emitted from the laser diode (not shown) is parallel to the axial direction when the lens driving device is mounted on the optical disc apparatus. Further, the lead screw 20 is coupled to be able to rotate together with the rotation shaft of the stepping motor 10 and is urged so that the other end is pressed against the bearing 80 by an elastic member (not shown) provided in the stepping motor 10. Has been. The bearing 80 is provided on a base that holds the stepping motor 10 and has a function as a bearing of the lead screw 20.

  The nut 30 is a specific example of the screw member of the present invention that has a female screw structure inside the opening and is screwed to the lead screw 20 in the female screw structure. Moreover, the nut 30 is provided with a convex structure on the outer peripheral portion, as will be described in detail later with reference to FIG. The convex structure regulates the rotation of the nut 30 due to the rotation of the lead screw 20 by engaging with a leaf spring 40 described later.

  Specifically, as the lead screw 20 rotates, typically, the nut 30 may rotate together due to friction between the lead screw 20 and the female screw structure of the nut 30. According to the above-described configuration, since the convex structure of the nut 30 and the leaf spring 40 are engaged so as to restrict the rotation of the nut 30, the nut 30 rotates the lead screw 20 instead of rotating together. Accordingly, the lead screw 20 moves in the axial direction.

  In addition, the movable portion 2 including the nut 30, the leaf spring 40, the lens frame 50, and the lens 70 has a predetermined movable range in the axial direction of the lead screw 20. The movable range may be set, for example, within a range where the nut 30 hits the stepping motor 10 or the bearing 80, or may be set by some means such as based on a necessary moving range of the lens 70. A stopper or the like for restricting the movement of the movable part 2 may be provided at the end of the movable range.

  By the way, when the stepping motor 10 is further driven when the movable unit 2 hits the end of the movable range, so-called biting may occur. This is typically caused by the female screw structure being screwed into the lead screw when the nut 30 cannot be moved and torque for further movement is supplied. Such biting will be described in detail later.

  Further, the nut 30 is configured by providing a protruding portion 31 at a portion in contact with the leaf spring 40, and the leaf spring 40 comes into contact with each other via the protruding portion 31.

  The leaf spring 40 is a specific example of the elastic member of the present invention. One end of the leaf spring 40 is fixed to the lens frame 50 and the other end is engaged with the nut 30. When the movable portion 2 hits the end of the movable range when the nut 30 tries to rotate further, the leaf spring 40 applies an elastic force in the opposite direction to the rotation, thereby suppressing the rotation. Do.

  In this embodiment, in particular, the spring constant of the leaf spring 40 is such that the stepping motor 10 steps out of the nut 30 at a position where the elastic force and the rotational force of the nut 30 due to the driving torque of the stepping motor 10 are balanced. The rotation is set to stop.

  The lens frame 50 is a specific example of the holding means of the present invention, and holds the lens 70 and is engaged with the nut 30 via the leaf spring 40, and in the optical axis direction according to the movement of the nut 30. It is configured to be movable. In general, the lens frame 50 is supported for movement in the optical axis direction by a guide bar 51 provided in the optical axis direction.

  Further, as shown in FIG. 1, the lens frame 50 is in contact with the nut 30 from one side of the moving direction via the leaf spring 40, and is attached to the direction in which the leaf spring 40 is pressed against the nut 30 by the coil spring 60 from this direction. It is energized. For this reason, the lens frame 50 and the leaf spring 40 move while being pushed in accordance with the movement of the nut 30 when moving in one direction (that is, in the direction of the stepping motor 10 in FIG. 1), As the nut 30 moves, the coil spring 60 is urged. Due to such a structure, the lens frame 50 of the present embodiment can move in the optical axis direction together with the nut 30.

  The lens 70 is held by the lens frame 50 on the optical axis of light passing through an objective lens (not shown) provided in the optical pickup. The lens 70 is typically arranged on the optical axis according to the driving of the stepping motor 10 so as to appropriately correct the spherical aberration caused by the change of the recording layer when data is recorded or reproduced on the optical disk having a multilayer structure. To move.

  Further, the stepping motor 10 according to the present embodiment is driven by receiving a driving current from the current source 110 by the drive control circuit 100. The drive control circuit 100 is a specific example of the control means of the present invention. For example, the drive control circuit 100 controls the drive torque by appropriately changing the current or voltage of the drive signal of the stepping motor 10, the drive frequency, and the excitation method. It is configured to be possible.

(2) Biting Next, biting according to a general lens driving device will be described with reference to FIGS. 2 and 3. 2 and 3 are schematic diagrams showing the excitation state of the electromagnet inside the stepping motor and the rotation of the rotor when the movable part hits the end of the movable range.

  As described above, the biting occurs when the female screw structure is screwed into the lead screw when the movable portion hits the end of the movable range. In general, when the movable part hits the end of the movable range, the stepping motor is driven to rotate in the direction opposite to that at the time of hitting as shown in FIG. . Specifically, as shown in FIG. 2 (a), the rotor of the stepping motor that has rotated clockwise is moved to the end of the movable range as shown in FIG. 2 (b). When it hits, as shown in Drawing 2 (c), rotation of a rotor stops.

  At this time, when the driving direction of the stepping motor is reversed so as to rotate the rotor in the direction opposite to that at the end of contact, the rotational force of the nut due to the driving torque of the stepping motor is such as the frictional force between the nut and the lead screw. If it is larger than the comparison, as shown in FIG. 2 (d), it is possible to return from the abutment with a sufficient torque.

  On the other hand, for example, when the torque when the movable part hits the end of the movable range is relatively high and exceeds the driving torque of the stepping motor at the start of driving (ie, so-called pull-in torque), FIG. As shown, there is a possibility that recovery from the butting cannot be performed due to insufficient torque (that is, biting occurs).

  In addition, when starting the stepping motor for returning from the butting, even if the nut rotational force due to the driving torque of the stepping motor is larger than the frictional force between the nut and the lead screw, etc., the electromagnet excitation Depending on the position, the nut will be tightened on the contrary, and the degree of screwing of the lead screw into the nut may be deepened.

  Specifically, for example, as shown in FIG. 3D, when the electromagnet excited in the stepping motor at the start of reverse rotation is an electromagnet adjacent in the tightening direction from the stop position of the rotor, The rotor is attracted in the tightening direction by the magnetic force of the excited electromagnet. For this reason, the degree of screwing of the lead screw into the nut is further deepened, and in some cases, the return from the abutment cannot be performed and the biting may occur. The stepping motor shown in FIG. 3 includes eight electromagnets and is driven by the one-phase excitation method. However, even when more electromagnets are provided or when the two-phase excitation method is used, Such tightening occurs probabilistically. In the case of a general claw pole type stepping motor, the amount of rotation of the stepping motor by retightening is a maximum of two steps.

  As will be described later, since the driving profile of trapezoidal control is used in the driving of a general stepping motor, the driving frequency when starting the motor is relatively low and the torque is relatively high. Yes. For this reason, if tightening is performed with such high torque, the degree of screwing of the lead screw into the nut is further deepened, and there is a possibility that recovery from the abutting cannot be performed.

(3) Basic Operation Example Next, with reference to FIG. 4, a basic operation of the lens driving device of the present embodiment will be described. FIG. 4 is a cross-sectional view orthogonal to the optical axis direction of the lens driving device of the present embodiment shown in FIG. The nut 30 shown in FIG. 4 moves as the stepping motor 10 (and the lead screw 20) rotates. FIG. 4 shows a state in which the nut 30 is rotating clockwise with the lead screw 20 as a rotation axis, and the movable portion 2 is in contact with the end of the movable range.

  In the present embodiment, when the stepping motor 10 is further driven in this state, the nut 30 starts to rotate clockwise by the driving torque of the stepping motor 10, and the nut 30 is energized by the rotation of the nut 30. The spring 40 is deformed and the elastic force is increased.

  In the lens driving device of this embodiment, the stepping motor 10 is stopped so that the rotation of the nut 30 stops at a position where the rotational force of the nut 30 generated by the driving torque of the stepping motor 10 and the elastic force of the leaf spring 40 are balanced. The drive torque and the leaf spring 40 are designed.

  At the time of return from the butting, the rotating nut 30 is urged by elastic force from the leaf spring 40 in the same direction as the rotation, so that the torque is higher than that of the configuration without the leaf spring 40. It is possible to return from the abutment. For this reason, for example, when the stepping motor 10 operates with the same drive torque, the torque at the time of return from abutment is increased by the amount corresponding to the urging by the leaf spring 40. Therefore, it is possible to enjoy the advantage that it is possible to preferably avoid the occurrence of biting.

  Thus, since the nut 30 can be restored relatively easily from the abutment, for example, a configuration in which the movable part 2 is intentionally abutted against the end of the movable range may be employed. For example, in a general lens driving device, a position detection sensor is mounted to detect positional information of a lens frame and, as a result, a nut, and whether the nut has been bitten. On the other hand, in the lens driving device 1 of the present embodiment, for example, when the stepping motor 10 is activated, the initial position may be determined by abutting the movable part 2 against one movable range end. With this configuration, position detection can be performed with a relatively simple configuration without using a configuration such as a position detection sensor. This is advantageous in terms of simplification of the configuration of the apparatus and cost.

(4) Operation of Drive Control Circuit In the lens drive device 1 of this embodiment, the drive control circuit 100 is configured to be able to control the drive signal of the stepping motor 10. In particular, in the present embodiment, the drive control circuit 100 operates when the stepping motor 10 is driven during the driving of the stepping motor 10 and when the movable portion 2 hits the end portion of the movable range and when the stepping motor 10 is activated to return from the contact. The driving torque is controlled.

  Typically, when the movable portion 2 hits the end of the movable range, the driving torque of the stepping motor 10 is controlled so that the torque is relatively low. The driving torque of the stepping motor 10 is controlled so that the torque becomes high.

  Consider a state in which the movable portion 2 hits the end of the movable range for each of such a relatively low torque and a relatively high torque. Since the amount of rotation of the nut 30 is determined according to the torque, for example, as shown in the graph of FIG. FIG. 5A is a graph showing the relationship between the torque when the movable portion 2 hits the end of the movable range and the amount of rotation of the nut 30. In addition, from the abutting with the low torque shown in FIG. 5A, the return can be performed by performing the reverse rotation with the torque relatively higher than the low torque. On the other hand, if the nut 30 rotates beyond the amount of rotation at a relatively high torque due to some factor, if the torque equal to or greater than the torque at the time of the abutting cannot be output by any means, Cannot be restored and bite occurs.

  Here, if the possibility of additional tightening at the time of return from the abutment described above is taken into consideration, a general rotation between a nut rotation amount at a relatively low torque and a nut rotation amount at a relatively high torque is generally used. In the case of a claw pole type stepping motor, if there is at least a rotation amount corresponding to two-step rotation, the butting can be restored without any problem. Therefore, the low torque at the time of butting and the high torque at the time of returning from the butting are set so as to satisfy such a condition.

  A specific method for controlling the drive torque of the stepping motor 10 by the drive control circuit 100 will be described below.

  The drive control circuit 100 may control the drive torque of the stepping motor 10 by changing the current or voltage of the drive signal supplied to the stepping motor 10. At this time, the drive control circuit 100 appropriately changes the current value supplied to the stepping motor 10 using, for example, the current source 110 that can supply a plurality of currents having different current values. For this reason, it is possible to relatively easily abut the nut 30 against the end of the movable range with a low torque, and to drive the stepping motor 10 with a high torque when returning from the abutment.

  Further, the drive control circuit 100 may control the drive torque by changing the excitation method of the electromagnet in the stepping motor 10. At this time, the drive control circuit 100 sets the excitation method of the electromagnet in the stepping motor 10 to one-phase excitation that provides a relatively low torque when the movable portion 2 hits the end of the movable range. At the time of recovery, two-phase excitation is used that provides a relatively high torque. For this reason, it is possible to relatively easily abut the movable portion 2 against the end of the movable range with a low torque, and to drive the stepping motor 10 with a high torque when returning from the abutment.

  Further, the drive control circuit 100 may control the drive torque by changing the drive frequency of the stepping motor 10. Generally, when the conditions of the drive current supplied to the stepping motor 10 are the same, the drive frequency and the drive torque are in a trade-off relationship. However, it is possible to obtain a relatively high torque by lowering the driving frequency, and driving at a relatively low torque by raising the driving frequency on the other hand. For this reason, it is possible to relatively easily abut the movable portion 2 against the end of the movable range with a low torque, and to drive the stepping motor 10 with a high torque when returning from the abutment.

  In general, in the driving mode of the stepping motor, as shown in FIG. 5 (b), it starts at a low frequency, gradually increases the driving frequency, and reaches a predetermined driving frequency at a constant frequency. A driving profile called trapezoidal control is used in which the frequency is gradually decreased when the operation is stopped.

  As a background of the driving profile of the trapezoidal control, it is known that the torque obtained at the start of driving of the stepping motor is different from that during driving. Generally, the torque obtained at the start of driving of the stepping motor is called pull-in torque, and the torque obtained during driving is called pull-out torque, which is the same as shown in FIG. The pull-in torque obtained with respect to the driving frequency is lower than the pull-out torque. For this reason, at the start of driving, in order to obtain the torque necessary for the rotation of the stepping motor, control is performed at a low frequency, but there is also a problem that it takes a long time to move the lens if it is always driven at a low frequency. Therefore, the problem can be solved by using trapezoidal control as the driving profile of the stepping motor.

  However, when the stepping motor 10 is driven based on the trapezoidal control as described above, the movable unit 2 is reduced in a state where the frequency at the time of stopping is reduced, such as when the movable unit 2 is positioned against the end of the movable range. Will hit the end, and for this reason, the movable part 2 will hit the end with a relatively high torque.

  In the present embodiment, for example, the frequency at the time of stopping in the trapezoidal control is not reduced, and the stopping is performed at a time from the state of constant frequency driving with a relatively high frequency. Accordingly, the movable part 2 can be abutted against the end of the movable range with a relatively low torque.

  Further, when the stepping motor 10 starts to start, if the end of the movable range exists in a relatively close position in the moving direction of the movable portion 2, the movable portion is in a state where the frequency at the time of activation in the trapezoidal control is relatively low. 2 may hit the end, and the movable part 2 may hit the end with a relatively high torque. In consideration of such a situation, the drive control circuit 100 rotates the stepping motor 10 in the reverse direction so that the movable unit 2 moves a predetermined amount in the direction opposite to the traveling direction when starting the stepping motor 10, and then the stepping motor 10. Start driving.

  Further, the drive control circuit 100 may control the driving torque of the stepping motor 10 by changing the driving mode of the stepping motor 10 to that based on PWM control, for example. The PWM control is a control method that artificially lowers the drive voltage of each electromagnet by modulating the pulse width of a pulse signal that excites the electromagnet of the stepping motor 10. According to such PWM control, the driving torque of the stepping motor 10 can be suitably controlled.

  The drive control circuit 100 of the present embodiment controls the drive torque of the stepping motor 10 by appropriately combining one or more of the various methods described above. Further, if the driving torque of the stepping motor 10 can be adjusted by some other method, this method can also be adopted as appropriate.

  As described above, the movable part 2 is abutted against the end of the movable range with a relatively low torque, and the stepping motor 10 is driven with a relatively high torque when returning from the abutting. Occurrence of biting can be avoided.

(5) Modified Configuration Example Next, a modified configuration example of the lens driving device of the present embodiment will be described with reference to FIGS. 6 and 7. FIG. 6 is a graph showing the relationship between the torque of the stepping motor 10 and the amount of rotation of the nut 30 when the movable part 2 hits the end of the movable range. On the other hand, FIGS. 7A to 7C are schematic views showing the structures of the first to third modified examples 1 of the lens driving device. According to various modifications of the lens driving device in the present embodiment, the spring constant of the portion where the leaf spring 40 biases against the nut 30 when the movable portion 2 hits the end of the movable range is reduced.

  Here, the rotation amount of the nut 30 when the spring constant for biasing the nut 30 by the leaf spring 40 or the like is relatively large will be described with reference to FIG. Under the control of the drive control circuit 100 described above, when the movable part 2 hits the end of the movable range with a relatively low torque and the nut 30 rotates, the amount of rotation of the nut 30 is relatively small A. . That is, when the nut 30 is rotated by A at the time of abutment, the elastic force of the leaf spring 40 is balanced with the rotational force of the nut 30. On the other hand, the amount of rotation of the nut 30 when the movable portion 2 hits the end of the movable range with a relatively high torque is B, which is relatively large. Here, when the stepping motor 10 is a general claw pole type stepping motor, if there is a rotation amount corresponding to two steps in the rotation of the stepping motor 10 between A and B, the stepping motor 10 abuts as described above. The possibility that it will not be possible to return from the above can be suitably suppressed.

  On the other hand, if for some reason the amount of rotation corresponding to the two steps cannot be secured between A and B, there remains a technical problem that makes it impossible to return from the abutment. Therefore, in this modification, when the movable part 2 hits the end part of the movable range, the spring constant of the urging force by the leaf spring 40 or the like is reduced. As shown in the graph of FIG. 6, when the spring constant of the urging force by the leaf spring 40 or the like becomes relatively small, the gradient of the torque with respect to the rotation amount of the nut 30 becomes loose, and even with the same torque, the spring constant Compared with the case where is large, the nut 30 will rotate more largely.

  As shown in the example of FIG. 6, in such a gentle gradient, the nut 30 that rotates at a relatively low torque described above rotates to C deeper than A. On the other hand, the nut 30 that rotates at a relatively high torque rotates to D deeper than B. When the spring constant is small, the torque gradient with respect to the rotation amount of the nut 30 is gentle, so the rotation amount from C to D is relatively larger than the rotation amount from A to B. For this reason, even if it is a case where required rotation amount cannot be ensured between rotation amount A of the nut 30 in the case of relatively low torque, and rotation amount B of the nut 30 in the case of relatively high torque. The amount of rotation can be relatively increased by setting the spring constant of the urging force by the leaf spring 40 or the like smaller. For this reason, the structure which can implement suitably avoiding generation | occurrence | production of biting is realizable.

  Various modifications of the lens driving device that realizes such a configuration will be described below with reference to FIG.

  A first modification of the lens driving device 1 of the present embodiment will be described with reference to FIG. As illustrated in FIG. 7A, the leaf spring 40 according to the first modification is configured to overlap with the second leaf spring 41. According to such double leaf springs 40 and 41, while the nut 30 is moving in accordance with the driving of the stepping motor 10, the biasing with a relatively large spring constant is performed. Rotation can be suitably suppressed.

  On the other hand, the 2nd leaf | plate spring 41 is comprised so that the urging | biasing to the nut 30 may be cancelled | released while the movable part 2a is contacting the edge part of a movable range. For example, the second leaf spring 41 is configured to deviate from a position where the nut 30 is biased when the movable portion 2a abuts against an end of the movable range. That is, according to the second leaf spring 41, the nut 30 is biased only by the leaf spring 40 while the movable portion 2a is in contact with the end of the movable range.

  For this reason, according to the leaf | plate spring 40, since it biases with a comparatively small spring constant with respect to rotation of the nut 30, the structure mentioned above is realizable.

  Next, a second modification will be described with reference to FIG. As shown in FIG. 7B, the leaf spring 40 according to the second modification is configured to include a stopper 42 for restricting the deformation of the leaf spring 40. For example, the stopper 42 is an inelastic member or the like that is formed to overlap the leaf spring 40. According to the stopper 42, the rotation of the nut 30 can be suitably suppressed while the nut 30 is moving according to the driving of the stepping motor 10.

  On the other hand, the stopper 42 is configured to release the deformation restriction of the leaf spring while the movable portion 2b is in contact with the end of the movable range. For example, the stopper 42 is configured to deviate from a position where the deformation of the leaf spring 40 is restricted when the movable portion 2b is in contact with the end of the movable range. That is, according to the stopper 42, the leaf spring 40 is allowed to be deformed according to the rotation of the nut 30 while the movable portion 2b is in contact with the end of the movable range.

  For this reason, according to the leaf | plate spring 40, since it biases with a comparatively small spring constant with respect to rotation of the nut 30, the structure mentioned above is realizable.

  Next, a third modification will be described with reference to FIG. As shown in FIG. 7C, the nut 30 according to the third modified example has a second protrusion 32 on an extension line between the fulcrum of the leaf spring 40 and the protrusion 31 in addition to the protrusion 31. It is configured with. The second projecting portion 32 is provided at a position farther from the fulcrum of the leaf spring 40 than the projecting portion 31, and while the nut 30 is moving according to the driving of the stepping motor 10, the second projecting portion 32 is not in contact with the leaf spring 40. It is configured not to touch. Further, the second protrusion 32 is configured to contact the leaf spring 40 instead of the protrusion 31 in accordance with the rotation of the nut 30 after the movable portion 2c hits the end of the movable range. That is, the nut 30 is in contact with the leaf spring 40 through the protrusion 31 while not rotating, and is in contact with the leaf spring 40 through the second protrusion 32 when rotated. Yes.

  According to the second projecting portion 32, since the second projecting portion 32 exists at a position farther from the projecting portion 31 than the fulcrum of the plate spring 40, when the second projecting portion 32 comes into contact with the leaf spring 40 via the second projecting portion 32, The lever ratio of the leaf spring 40 changes compared to the case where the leaf spring 40 abuts, and the spring constant for biasing the nut 30 of the leaf spring 40 becomes relatively small.

  For this reason, by adjusting the spring constant of the leaf spring 40, etc., while the nut 30 is moving, the rotation of the nut 30 is suppressed by biasing with a relatively large spring constant, and the movable portion 2c is movable. After abutting against the end portion, the above-described configuration can be realized by biasing with a relatively small spring constant.

  The present invention is not limited to the above-described embodiments, and can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification. Is also included in the technical scope of the present invention.

1 Lens drive device,
2 moving parts,
10 Stepping motor,
20 lead screw,
30 nuts,
40 leaf spring,
50 lens frame,
60 coil spring,
70 lenses.

Claims (12)

A lead screw;
A stepping motor for rotating the lead screw;
A screw member that engages with the lead screw and is movable in the axial direction of the lead screw as the lead screw rotates, and a lens are held, and are also movably engaged with the movement of the screw member. A lens driving device comprising: a holding unit; and a movable unit that includes an elastic member that is provided at an engaging portion between the holding unit and the screw member and biases the screw member. .   When the movable part hits an end of a predetermined movable range, the screw member stops rotating at a position where the rotational force of the screw member due to the driving torque of the stepping motor balances with the elastic force of the elastic member. The lens driving device according to claim 1. A control means for controlling a drive signal of the stepping motor;
The control means is configured to change the driving torque of the stepping motor at least one of when the movable part hits an end of a predetermined movable range and when the movable part returns from the end. The lens driving device according to claim 1, wherein the driving signal is controlled.   4. The lens driving apparatus according to claim 3, wherein the control unit controls the driving torque of the stepping motor by changing a current or voltage of a driving signal supplied to the stepping motor.   The lens driving apparatus according to claim 3, wherein the control unit controls a driving torque of the stepping motor by changing an excitation method of the stepping motor.   The lens driving device according to claim 3, wherein the control unit controls a driving torque of the stepping motor by changing a driving frequency of the stepping motor.   The control means moves the movable part to the end of the movable range after moving the movable part by a predetermined amount in the direction opposite to one end of the predetermined movable range when driving the stepping motor. The lens driving device according to claim 6, wherein the position of the movable portion is detected.   The said control means controls the drive torque of the said stepping motor by changing the aspect of the drive of the said stepping motor to the thing by PWM (Pulse Width Modulation) control. Lens drive device.   The elastic member biases the screw member after the movable portion contacts the end of the movable range, compared to before the movable portion contacts the end of the predetermined movable range. The lens driving device according to any one of claims 1 to 8, wherein the spring constant of the part is configured to be small.   The elastic member includes a plurality of spring members that urge against the screw member, and the number of the spring members that urge against the screw member is changed, so that the movable portion becomes an end of the movable range. The lens driving device according to claim 9, wherein a spring constant of a portion to be urged against the screw member after contacting the portion is configured to be small. The elastic member includes a spring member that urges the screw member and a stopper member that suppresses rotation of the screw member accompanying rotation of the lead screw,
The lens driving device according to claim 9, wherein the stopper member does not suppress the rotation of the screw member after the movable portion comes into contact with an end portion of the movable range.   The screw member is configured such that a contact portion with the elastic member changes before and after the movable portion hits an end portion of the movable range, and the elastic member is changed to the screw according to the change of the contact portion. The lens driving device according to claim 9, wherein a spring constant of a portion biased against the member is configured to be small.

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