JPH1079131A - Objective lens driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent horizontal backlashing of a lens holder on a slide shaft in an objective lens holder of a type that prevents the backlashing of the lens holder by applying a side pressure. SOLUTION: A shaft hole 11 of a lens holder in an objective lens driver is formed with a square cross section so as to have first and second slant walls 111 and 112 forming a V-shaped cross section. A round bar-shaped slide shaft 7 is inserted into the shaft hole. A side pressure F is applied to the lens holder 1 by a side pressure application means to press the outer circumferential surface 71 of the slide shaft 7 onto the first and second slant walls 111 and 112 on the inner circumferential surface 110 of the shaft hole 11. This allows the outer circumferential surface 71 of the slide shaft 7 to contact the inner circumferential surface 110 of the shaft hole at a first contact part 111a and a second contact part 112a at two points on both sides sandwiching a pressing application line 13 by the side pressure application means. This restricts the positional deviation of the lens holder 1 in the direction orthogonal to the application line 13 of the side pressure F by the first and second contact parts 111a and 112a thereby eliminating horizontal backlashing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaft-sliding type objective lens driving device for an optical pickup used in an optical disk device or the like. More specifically, the present invention relates to a structure for preventing rattling of a lens holder holding an objective lens in an objective lens driving device of this type.

[0002]

2. Description of the Related Art A shaft-sliding type objective lens driving device for an optical pickup such as an optical disk device inserts a sliding shaft formed on a fixed side into a shaft hole formed in a movable lens holder. The lens holder is held on the sliding shaft.

Here, both the sliding shaft and the shaft hole have a circular cross section so that the lens holder can slide or rotate around the axial direction with respect to the sliding shaft to perform focusing or tracking of the objective lens. And a gap of about 10 μm is provided between the sliding shaft and the shaft hole.

[0004]

However, the gap formed between the sliding shaft and the shaft hole causes rattling when the lens holder slides or rotates. For this reason,
Applies a side pressure that presses the lens holder with a certain amount of force from a direction substantially perpendicular to the sliding shaft, stabilizes the contact between the shaft hole and the sliding shaft, and creates a play between the lens holder and the sliding shaft. There are ways to prevent this. However, even when a lateral pressure is applied to the lens holder in a state where there is a gap between the sliding shaft having a circular cross section and the shaft hole, the sliding shaft comes into contact with the inner peripheral surface of the shaft hole of the lens holder. Is only one position located on the line of action of the lateral pressure, so that displacement in the direction orthogonal to this line of action is not regulated at all. Therefore, even if a lateral pressure is applied to the lens holder with the conventional structure, the rattling will not be sufficiently resolved, and if vibrations are applied from the outside while playing a CD etc., the playability will deteriorate and sound skip will occur. There is a problem that. In addition, there is also a problem that an error is likely to occur when performing a minute tracking by giving a kick pulse such as a one-track kick to the lens holder. On the other hand, if the lateral pressure is increased and the lens holder is pressed strongly against the sliding shaft, the friction between the sliding shaft and the shaft hole increases, resulting in a new hysteresis in the sliding and rotating characteristics of the lens holder. Problems arise.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems. In an objective lens driving device of a type that applies a lateral pressure to a lens holder, the lens holder rattles left and right with respect to a sliding shaft. It is to propose a configuration for preventing such a situation.

[0006]

According to the present invention, there is provided a lens holder holding an objective lens and having a shaft hole, a sliding shaft inserted into the shaft hole, and In an objective lens driving device having a driving coil and a magnet for performing a focusing drive for sliding the lens holder in the axial direction of the sliding shaft and a tracking drive for rotating the lens holder about the axis, the lens holder is provided with the sliding shaft. Having side pressure applying means for generating a side pressure for pressing from a direction substantially orthogonal to
One of an outer peripheral surface of the sliding shaft and an inner peripheral surface of the shaft hole is formed in a circular cross-section, and the other is an outer periphery of the sliding shaft at two places on both sides sandwiching a line of action of pressing by the side pressure applying means. A surface and an inner peripheral surface of the shaft hole are configured to have a first contact portion and a second contact portion.

According to the present invention, when a lateral pressure is applied to the lens holder, the outer peripheral surface of the sliding shaft and the inner peripheral surface of the shaft hole sandwich the line of action of the lateral pressure at two places on both sides (the first contact portion and the second contact portion). Contact portion). Therefore, when the lens holder receives the lateral pressure, the first and second contact portions restrict the displacement in the direction orthogonal to the line of action of the lateral pressure, so that the lens holder does not rattle left and right. For this reason, even if an excessive side pressure is not applied to the lens holder, it is possible to prevent an error caused by an external vibration or a kick pulse such as a one-track kick.

In the present invention, the side pressure applying means is constituted by the magnet and a magnetic piece disposed opposite to the magnet, and the side pressure is applied by a magnetic attraction generated between the magnetic piece and the magnet. Preferably, it is configured to generate.

In this case, the magnetic piece can also be used as a means for holding the lens holder at a predetermined neutral position using the magnetic attraction when the drive coil is not excited.

In the present invention, when the sliding shaft is formed in a round bar shape, the first and second contact holes are provided at two places on both sides of the line of action of the pressing by the lateral pressure applying means. In order to form a part, the inner peripheral surface of the shaft hole is provided with first and second inclined walls having a V-shaped cross section.

In this case, it is preferable that the angle formed by the first and second slope walls is 90 ° or less. Such a configuration is preferable because the force for regulating the position of the lens holder acts greatly.

In the present invention, it is preferable that the line of action of the pressing by the lateral pressure applying means is on a line bisecting the angle formed by the first and second slope walls. With this configuration, the lens holder receives balanced and uniform forces from the first and second slope walls, so that the lens holder slides and rotates smoothly.

In the present invention, it is preferable that the side pressure applying means is configured to press the lens holder in a direction orthogonal to a tracking direction.

[0014]

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

(Overall Configuration) FIG. 1 is a plan view of an objective lens driving device to which the present invention is applied, and FIG. 2 is a schematic sectional view taken along line AA 'of FIG.

As shown in these figures, the objective lens driving device 20 includes a lens holder 1 holding an objective lens 2.
Focusing drive coil 4 and tracking drive coil 3 formed on the outer peripheral surface of lens holder 1
And a sliding shaft 7 supporting the lens holder 1 and an outer yoke 9 fixing the base end 73 of the sliding shaft 7 and holding a focusing magnet 6a and a tracking magnet 6b.

The lens holder 1 is formed in a cylindrical shape as a whole, and holds the objective lens 2 on the outer peripheral edge. A balancer 8 is mounted on the outer peripheral surface of the lens holder 1 on the side opposite to the objective lens 2. A pair of focusing drive coils 4 and tracking drive coils 3 are fixed to the outer peripheral surface of the lens holder 1 symmetrically with respect to the center of the lens holder 1.

A cylindrical support portion 12 is formed at the center of the lens holder 1, and a shaft hole 11 is formed therein. The lens holder 1 is slidable in the axial direction with respect to the sliding shaft 7 and rotatable around the axis by inserting the sliding shaft 7 into the shaft hole 11. In the present invention, as will be described later, a side pressure that presses the lens holder 1 from a direction substantially orthogonal to the sliding shaft 7 is generated so that the lens holder 1 does not rattle against the sliding shaft 7. The shapes of the shaft hole 11 and the sliding shaft 7 are optimized.

The outer yoke 9 to which the base end 73 of the sliding shaft 7 is fixed has an arc shape on both sides with the sliding shaft 7 interposed therebetween, and these arc-shaped peripheral wall portions stand up at right angles. On the inner peripheral surface of the outer wall of the outer yoke 9, a focusing magnet 6 is provided at a position facing the focusing drive coil 4.
a is fixed, and a tracking magnet 6b is fixed at a position facing the tracking drive coil 3. The inner yoke 5 is disposed on the sliding shaft 7 side of the focusing drive coil 4. The inner yoke 5 extends through the window 1a of the lens holder 1 from the lower side to the upper side.

As described above, the inner yoke 5, the drive coils 3, 4, the magnets 6a and 6b, and the outer yoke 9 are arranged in this order from the side of the sliding shaft 7 to the outside. A substantially closed magnetic circuit is formed therethrough. The peripheral wall of the outer yoke 9 may be cylindrical instead of arc-shaped. Further, in the above embodiment, the example in which the inner yoke 5 is provided inside the outer yoke 9 is shown, but the inner yoke 5 may not be provided.

FIG. 3A is an explanatory view for explaining an example of the magnetized state of the magnet, and FIG. 3B is an explanatory view showing the shape of the drive coil.

As shown in FIG. 3A, the focusing magnet 6a and the tracking magnet 6b are arranged at intervals around the sliding shaft 7 in the circumferential direction. The focusing magnet 6a is polarized and magnetized so that the N and S poles are arranged in the axial direction of the sliding shaft 7. On the other hand, the tracking magnet 6b
Are polarized and magnetized such that the N pole and the S pole are arranged in a direction perpendicular to the magnetizing direction of the focusing magnet 6a (circumferential direction around the sliding shaft 7). The focusing magnet 6a and the tracking magnet 6
b may be formed integrally. In this case, a groove extending in a direction parallel to the sliding shaft 7 is formed in the middle part of one magnet, and the focusing magnet 6a and the tracking magnet 6b are magnetized separately from the groove. I do.

Next, as shown in FIG. 3 (b), the focusing drive coil 4 has a horizontally long rectangular shape, and its long side is arranged so as to face each magnetic pole of the focusing magnet 6a. . The tracking drive coil 3 has a vertically long rectangular shape, and is disposed such that a long side thereof faces each magnetic pole of the tracking magnet 6b. When a drive current is applied to the focusing drive coil 4, the lens holder 1 slides in the axial direction with respect to the slide shaft 7, and the focusing operation of the objective lens 2 mounted thereon is performed. When a drive current is applied to the tracking drive coil 3, the lens holder 1 rotates around the axis with respect to the slide shaft 7, and the tracking operation of the objective lens 2 mounted thereon is performed.

(Side Pressure Applying Means) When the lens holder 1 performs such an operation with respect to the slide shaft 7, rattling may occur between the shaft hole 11 and the slide shaft 7. In order to prevent such rattling, the objective lens driving device 20 of the present embodiment is provided with a side pressure applying means for generating a side pressure for pressing the lens holder 1 from a direction substantially perpendicular to the sliding shaft 7. I have.

As shown in FIG. 1, a pair of magnetic pieces 10A and 10B are used in the lateral pressure applying means incorporated in the objective lens driving device 20 of the present embodiment. These magnetic pieces 10A, 10B are provided at the outer peripheral portion of the lens holder 1 at the magnetic pole centers 6A, 6A of the focusing magnet 6a.
B is fixed at a position shifted from the position facing B by an angle a in the opposite direction.

FIG. 4 shows an attached portion of one magnetic piece 10A taken out. As shown in FIGS. 1 and 4, the magnetic piece 10 </ b> A is a plate-shaped member that is long in the axial direction of the sliding shaft 7, and the circumferential width x around the sliding shaft 7 is equal to the focusing magnet 6 a. The length in the axial direction of the sliding shaft 7 is set to be shorter than the length in the direction of the axis 7a of the focusing magnet 6a, which is considerably smaller than the size in the circumferential direction. The other magnetic piece 10B is also the magnetic piece 1
It is a part common to 0A, has the same shape and the same magnetic characteristics.

The magnetic pieces 10A, 10B thus configured
A magnetic attractive force acts between the focusing magnet 6a and the focusing magnet 6a. At this time, since the magnetic pieces 10A and 10B are arranged at a position shifted by an angle a from the position facing the magnetic pole centers 6A and 6B of the focusing magnet 6a, the magnetic piece 10A and the focusing magnet facing the magnetic piece 10A and 10B. 6a and the magnetic piece 10B
And the magnetic attraction force between the focusing magnets 6a facing each other, and a side pressure F for pressing the lens holder 1 laterally against the sliding shaft 7 is generated as shown by an arrow in FIG. Here, tracking with respect to the objective lens 2 is actually performed by the rotational movement of the lens holder 1, but since its angular range is small, if its tangential direction (represented by an arrow X) is regarded as the tracking direction, It can be said that the lateral pressure F is generated in a direction orthogonal to the tracking direction. Therefore, the lateral pressure F does not hinder the tracking operation of the lens holder 1.

As described above, in the present embodiment, the magnetic pieces 10A and 10B are opposed to the focusing magnet 6a, and the focusing magnet 6a and the magnetic pieces 10A,
The lateral pressure F is generated by a magnetic attraction force generated between the pressure F and the pressure 10B.

When the tracking drive coil 3 is not excited, the focusing magnet 6a balances the magnetic attraction of each of the magnetic pieces 10A and 10B in the circumferential direction, so that the lens holder 1 is moved to the position shown in FIG. At the neutral position shown in the tracking direction. On the other hand, as shown in FIG. 4, in the cross section of the sliding shaft 7 of the focusing magnet 6a in the direction of the axis 7a, the focusing magnet 6a is polarized and magnetized in the direction of the axis 7a. The gradient of the magnetic flux in the air gap where 10B is arranged is reversed at the middle part in the vertical direction. Here, the magnetic pieces 10A and 10B act as a part of a magnetic path, and the magnetic pieces 10A and 10B are magnetically attracted to the central part of the polarization magnetization. Since this suction force acts as a return force, the focusing drive coil 4
Is not excited, the lens holder 1 is held at a predetermined high position in the axial direction of the sliding shaft 7.

As described above, the magnetic pieces 10A and 10B are also used as means for generating the lateral pressure F and holding the lens holder 1 at a predetermined neutral position.

(Structure for preventing rattling of the lens holder) However, even when the lens holder 1 is pressed from the direction substantially perpendicular to the sliding shaft 7 as described above, both the shaft hole 11 and the sliding shaft 7 are not pressed. If the lens holder 1 is formed in a circular cross section, it is not possible to reliably prevent the lens holder 1 from rattling. Therefore, in the present invention, by optimizing the shapes of the shaft hole 11 and the sliding shaft 7, the lens holder 1 is prevented from rattling in the direction (left and right) orthogonal to the line of action of the lateral pressure F.

FIG. 5A is an enlarged plan view showing the sliding shaft 7 and the shaft hole 11. FIG. 5 (b) is the same as FIG.
3 is a schematic vertical sectional view taken along line BB ′ of FIG. FIG.
7A, the state in which the sliding shaft 2 presses the lens holder 1 as a result of the lens holder 1 receiving the side pressure F is represented as a side pressure F '.

As shown in these figures, the sliding shaft 7 is formed in a round bar shape, and the outer peripheral surface 71 has a circular cross section.
On the other hand, the inner peripheral surface 110 of the shaft hole 11 is formed to have a square cross section, and the portion of the inner peripheral surface 110 that receives the sliding shaft 2 is a first slope wall 111 and a second slope wall 112.
(First contact portion and second contact portion)
It is configured in a character shape.

Therefore, when the lateral pressure F is applied to the lens holder 1, the first inclined wall 111 and the second inclined wall 112 of the shaft hole 11 are located at two places on both sides of the line of action 13 of the pressing by the lateral pressure applying means. The sliding shaft 7 is received as the first contact portion 111a and the second contact portion 112a. The action line 13 of the lateral pressure F is the first and second sloped wall 11.
1, 112 are on a line that bisects the angle θ. In this state, the lens holder 1 holds the first and second contact portions 11.
Since the positional deviation of the lateral pressure F in the direction orthogonal to the action line 13 is restricted at two places 1a and 112a, there is no rattling on the left and right. For this reason, even if an excessive side pressure is not applied to the lens holder 1, it is possible to prevent an error caused by an external vibration or a kick pulse such as a one-track kick. Further, since the action line 13 of the lateral pressure F is on a line that bisects the angle between the first slope wall 111 and the second slope wall 112, the first and second slope walls 111 and 112 are balanced. Lens holder 1
Sliding and rotating smoothly.

Here, when the angle θ between the first slope wall 111 and the second slope wall 112 is changed, the relationship between the forces applied to the sliding shaft 7 and the shaft hole 11 changes. That is, as can be seen from FIG. 6, the angle θ between the first slope wall 111 and the second slope wall 112, the side pressure F applied to the lens holder 1 (side pressure F ′), the first and second contact portions 111 , 11
The following equation Fs = F / 2sin (θ / 2) holds between the vertical force Fs received by the second element 2.

When the above-mentioned lateral pressure F is applied to the lens holder 1, a force Fn that can withstand rattling in a direction perpendicular to this direction, a first slope wall 111 and a second slope. The angle θ formed between the wall 112 and the wall 112 has the following relationship: Fn = F / tan (θ / 2) (2)

For this reason, when the relationship shown by the equation (1) is shown by a solid line B1 in FIG. 7 and the relationship shown by the equation (2) is shown by a solid line B2 in FIG. 7, the first contact portion 111 and the second contact The smaller the angle θ formed between the first and second contact portions 11
Each of the vertical force Fs received by the first and second members 112 and the force Fn that can withstand the backlash in the direction perpendicular to the lateral pressure F are large. FIG. 7 shows the first and second contact portions 111, 1
The solid line B3 represents the ratio of the force Fn that can withstand the backlash in the direction perpendicular to the lateral pressure F to the perpendicular force Fs received by 12.

As described above, the smaller the angle θ between the first contact portion 111 and the second contact portion 112 is, the larger the force for regulating the lens holder 1 acts.
It is difficult for the left and right rattling to occur.
With the following settings, rattling due to external vibration and kick pulses such as a one-track kick to the lens holder 1 can be appropriately suppressed.

[Another Embodiment] In this embodiment, as a side pressure applying means, the magnetic piece 10 is shifted from the magnetic pole center 6A, 6B of the focusing magnet 6a by an angle a.
Although A and 10B face each other, a method using a leaf spring or a method using a damper made of an elastic material may be used in addition to the method of magnetically generating the lateral pressure F.

Even if the shape of the shaft hole 11 is not a square cross section,
Other shapes may be formed as long as the first slope wall 111 and the second slope wall 112 having the inner peripheral surface 110 of the shaft hole 11 having a V-shaped cross section are provided.

In the above embodiment, the sliding shaft 7 has a round bar shape, and the inner peripheral surface 110 of the shaft hole 11 has a V-shaped section. However, as shown in FIG. The peripheral surface 150 may be formed on a surface 151 having a circular cross section, and the sliding shaft 14 may be formed into, for example, a square cross section. In this case, the corners 141 and 142 of the sliding shaft 14 are the first and second contact portions 1.
11a, the contact portion 112a contacts the inner peripheral surface 150 of the shaft hole 15 at two places on both sides of the action line 13 of the lateral pressure F. Therefore, since the lens holder 1 is restricted from being displaced in two directions of the first and second contact portions 111a and 112a in the direction orthogonal to the action line 13 of the lateral pressure F, the lens holder 1 does not rattle left and right.

[0042]

As described above, according to the present invention, one of the outer peripheral surface of the sliding shaft and the inner peripheral surface of the shaft hole is formed in a circular cross section, and the other is a line of action of pressing by the line of action of lateral pressure. The outer peripheral surface of the sliding shaft and the inner peripheral surface of the shaft hole are configured to have a first contact portion and a second contact portion at two places on both sides of the sliding shaft. Therefore, the lens holder does not rattle left and right because the first and second contact portions restrict the displacement of the lens holder in the direction orthogonal to the line of action of the lateral pressure without applying excessive lateral pressure.

[Brief description of the drawings]

FIG. 1 is a plan view showing an objective lens driving device to which the present invention is applied.

FIG. 2 is a schematic sectional view taken along the line A-A 'of FIG.

3A is an explanatory diagram illustrating a magnetized state of a magnet, and FIG. 3B is an explanatory diagram illustrating a shape of a driving coil.

FIG. 4 is an explanatory diagram showing a state of a magnetic flux in a magnetic piece portion.

FIG. 5A is an enlarged plan view showing a sliding shaft and a shaft hole, and FIG. 5B is a schematic longitudinal sectional view taken along line BB ′ of FIG.

FIG. 6 is an explanatory diagram showing a relationship between forces applied to a sliding shaft and a shaft hole.

FIG. 7 is a graph showing a relationship between forces applied to a sliding shaft and a shaft hole.

FIG. 8 is an enlarged plan view showing a sliding shaft and a shaft hole according to another embodiment of the present invention.

[Description of Signs] 1 Lens holder 2 Objective lens 3, 4 Drive coil 6a, 6b Magnet 7, 14 Sliding axis 10A, 10B Magnetic piece 11, 15 Shaft hole 13 Side pressure acting line 20 Objective lens driving apparatus 71 Sliding axis Outer peripheral surface 110, 150 Inner peripheral surface of shaft hole 111 First slope wall 111a First contact portion 112 Second slope wall 112a Second contact portion

Continued on the front page (72) Inventor Moto Kinoshita 14-888 Ako, Komagane-shi, Nagano Pref.

Claims (7)

[Claims] 1. A lens holder holding an objective lens and having a shaft hole, a sliding shaft inserted into the shaft hole, and focusing for sliding the lens holder in the axial direction of the sliding shaft. In an objective lens driving device having a driving coil and a magnet for performing driving and tracking driving for rotating around an axis, a side pressure applying means for generating a side pressure for pressing the lens holder from a direction substantially orthogonal to the sliding axis. One of an outer peripheral surface of the sliding shaft and an inner peripheral surface of the shaft hole is formed in a circular cross section, and the other is provided with the sliding member at two positions on both sides sandwiching a line of action of the pressing by the lateral pressure applying means. An objective lens, wherein an outer peripheral surface of a moving shaft and an inner peripheral surface of the shaft hole have a first contact portion and a second contact portion. Operated device. 2. The apparatus according to claim 1, wherein the side pressure applying means is constituted by the magnet and a magnetic piece disposed opposite to the magnet, and is provided by a magnetic attraction force generated between the magnetic piece and the magnet. An objective lens driving device configured to generate the lateral pressure. 3. The magnetic piece according to claim 2, wherein the magnetic piece is configured to hold the lens holder at a predetermined neutral position using the magnetic attraction when the drive coil is not excited. An objective lens driving device, characterized in that: 4. The method according to claim 1, wherein
The sliding shaft is formed in a round bar shape, and the shaft hole is formed with the shaft hole for forming the first and second contact portions at two places on both sides of the line of action of the pressing by the lateral pressure applying means. First and second inner peripheral surfaces of which have a V-shaped cross section.
An objective lens driving device, comprising: 5. The method according to claim 4, wherein
The angle formed by the inclined wall is 90 ° or less. 6. The line of action according to claim 4, wherein the line of action of the pressing by the lateral pressure applying means is the first and second lines.
An objective lens driving device, which is on a line bisecting an angle formed by the inclined wall of the objective lens. 7. The method according to claim 1, wherein
The objective lens driving device, wherein the side pressure applying unit is configured to press the lens holder in a direction orthogonal to a tracking direction.