Voice coil motor based on asymmetric Halbach permanent magnet array and photographic lens

Abstract

The application relates to the technical field of voice coil motors, and provides a voice coil motor based on an asymmetric Halbach permanent magnet array and a photographic lens, which are used for cooperating with a locking mechanism to control the focusing movement of a focusing group component. The voice coil motor comprises a coil, a yoke and a permanent magnet array. The coil is movably arranged in the yoke, and the permanent magnet array is arranged on the inner side of the yoke. The coil and the permanent magnet array are oppositely arranged, and a working air gap is formed between the coil and the permanent magnet array. The permanent magnet array is in an asymmetric Halbach structure. The permanent magnet array comprises a first permanent magnet, a second permanent magnet and a third permanent magnet which are arranged in sequence along the moving direction of the coil. The length of the first permanent magnet in the moving direction of the coil is greater than the length of the third permanent magnet. The first permanent magnet is arranged on the side close to the locking mechanism, so that the thrust constant of the focusing section is effectively improved, the effective stroke of the focusing section is prolonged, the stroke resource of the locking section is released, the magnetic energy utilization efficiency is further improved, and the motor power consumption is reduced.

Description

Technical Field

[0001] This invention relates to the field of voice coil motor technology, and in particular to a voice coil motor and a camera lens based on an asymmetric Heilbeck permanent magnet array. Background Technology

[0002] In the voice coil motor (VCM) drive system of a camera lens, the stator of the VCM is fixed to the lens structure, and the coil acts as the mover. When energized, the coil is driven by the Lorentz force in the magnetic field generated by the permanent magnet, which in turn moves the lens movement group bound to it, thereby realizing the lens's autofocus or zoom function. However, when the device is powered off or in sleep mode, the mover lacks fixed constraint, which can easily cause noise due to shaking when carried around, and may cause damage to internal components if dropped or bumped. Therefore, a locking mechanism is usually required to assist in fixing the mover. Specifically, the stator of the locking mechanism is fixed to the lens structure, and the mover is fixedly connected to the coil and the lens movement group. When the power is off, the locking mechanism uses the permanent magnet attraction to lock the movement group in a fixed position. When the power is on, the locking mechanism generates a repulsive force or eliminates the attraction force by passing current, pushing the mover away to release the movement group and allow it to resume free movement.

[0003] In existing technologies, the permanent magnets of conventional voice coil motors mostly employ uniform magnetization or symmetrical Heilbeck arrays, with their magnetic fields symmetrically distributed along the travel direction. However, the aforementioned traditional voice coil motor structures have the following inherent drawbacks within the limited space of a camera: First, the locking segment ineffectively occupies the effective travel. The locking travel corresponding to the engagement and unlocking of the locking mechanism occupies a portion of the axial physical space that could originally be used for focusing. However, due to the symmetrical distribution of the magnetic field, the locking travel range still maintains a thrust constant comparable to that of the focusing segment. In reality, the release of the locking mechanism mainly relies on its own electric repulsive force or mechanical spring force. The voice coil motor only needs to provide a very small electromagnetic force or even no force at all in this segment, and does not need to output a large thrust. The symmetrical magnetic field cannot achieve the on-demand distribution of thrust in space, resulting in the ineffective consumption of magnetic potential energy and axial travel resources in the locking travel range, causing a substantial reduction in the available travel of the focusing segment.

[0004] Secondly, the magnetic saturation characteristics of the yoke further deteriorate the stroke utilization efficiency of the motor. In conventional voice coil motors, the yoke is prone to magnetic saturation at both ends of the axial stroke, resulting in a decrease in magnetic field utilization. In the middle of the stroke, the magnetic circuit of the yoke is not saturated, and there is also the problem of insufficient air gap magnetic field strength. Whether the locking stroke range falls in the magnetic saturation area at the end of the yoke or the weak magnetic field area in the middle, the thrust constant in the locking stroke range is constrained by the magnetic field of the symmetrical permanent magnet array and cannot be specifically reduced, further wasting the limited axial space. This severely restricts the thrust improvement and effective stroke extension of the focusing section.

[0005] Third, excessive design is forced to compensate for the loss of focus travel. Because the locking mechanism encroaches on the effective focusing travel, existing solutions typically increase the overall size of the motor or use higher-performance permanent magnet materials to meet the lens's focusing travel requirements, attempting to shorten focusing time and compensate for the performance loss caused by insufficient travel by increasing thrust. However, this approach increases the cost of permanent magnets, structural components, and other materials, increases the power consumption of the motor, and also increases the size of the camera lens module, thus running counter to the design trend of miniaturization and low power consumption in consumer electronics lenses. Summary of the Invention

[0006] The purpose of this invention is to provide a voice coil motor and camera lens based on an asymmetric Heilbeck permanent magnet array, aiming to solve the technical problems of ineffective use of magnetic potential energy and stroke resources in the locking section of existing voice coil motors, insufficient effective focusing stroke, and difficulty in balancing module miniaturization and low power consumption requirements.

[0007] In a first aspect, the present invention provides a voice coil motor based on an asymmetric Heilbeck permanent magnet array for use in conjunction with a locking mechanism to control the focusing motion of a moving group assembly. The voice coil motor includes: a coil, a yoke, and a permanent magnet array. The coil is movably disposed within the yoke, and the permanent magnet array is disposed on the inner side of the yoke. The coil and the permanent magnet array are disposed opposite each other, and a working air gap is formed between the coil and the permanent magnet array. The permanent magnet array is an asymmetric Helbeck structure. The permanent magnet array includes a first permanent magnet, a second permanent magnet, and a third permanent magnet arranged sequentially along the coil movement direction. The length of the first permanent magnet in the coil movement direction is greater than the length of the third permanent magnet. The first permanent magnet is disposed on the side close to the locking mechanism. The lengths of the first permanent magnet and the third permanent magnet satisfy the following condition: 2.5 ≤ H01 / H02 ≤ 3.5; Wherein, H01 represents the length of the first permanent magnet, and H02 represents the length of the third permanent magnet.

[0008] In some embodiments, the yoke includes a bottom wall, a top wall disposed opposite to the bottom wall, and a first side wall and a second side wall connecting the bottom wall and the top wall, wherein the permanent magnet array is fitted onto the inner surface of the bottom wall facing the top wall.

[0009] In some embodiments, the coil is a straight plate type coil, the coil is movably disposed between the first sidewall and the second sidewall, and a movement gap is provided between the coil and the top wall of the yoke.

[0010] In some embodiments, a supplementary permanent magnet is further included, which is embedded in the yoke and is located below the second permanent magnet, with the supplementary permanent magnet offset from the geometric center of the coil movement direction toward the third permanent magnet.

[0011] In some embodiments, a first air gap is formed between the side of the first permanent magnet away from the second permanent magnet and the first sidewall, and a second air gap is formed between the side of the third permanent magnet away from the second permanent magnet and the second sidewall.

[0012] In some embodiments, the length of the first air gap is equal to the length of the second air gap.

[0013] In some embodiments, the first air gap and the total stroke of the voice coil motor satisfy the following conditions: 5.8% ≤ T01 / Ht ≤ 15.6%; Wherein, T01 represents the length of the first air gap, and Ht represents the total stroke of the voice coil motor.

[0014] In some embodiments, the length of the first permanent magnet, the length of the third permanent magnet, and the total stroke of the voice coil motor satisfy the following conditions: 10% ≤ (H01 + H02) / Ht ≤ 22.5%; Wherein, H01 represents the length of the first permanent magnet, H02 represents the length of the third permanent magnet, and Ht represents the total stroke of the voice coil motor.

[0015] Secondly, the present invention provides a photographic lens, including a moving group assembly, a locking mechanism, and a voice coil motor based on an asymmetric Heilbeck permanent magnet array as described above. The voice coil motor is fixedly connected to the moving group assembly and is used to drive the moving group assembly to move along the coil movement direction when energized. The locking mechanism is used to lock the moving group assembly when de-energized and release the moving group assembly when energized.

[0016] This invention, through an embodiment of the permanent magnet array configured as an asymmetric Heilbeck structure and a first permanent magnet with a length greater than that of a third permanent magnet, results in an asymmetric distribution of the synthetic magnetic field along the coil's movement direction. The main lobe of the magnetic flux density shifts away from the locking mechanism, concentrating the high magnetic flux density region of the air gap magnetic field towards the focusing section. This effectively increases the thrust constant of the focusing section and extends its effective travel. By placing the first permanent magnet closer to the locking mechanism, the thrust constant is actively reduced within the corresponding travel range of the locking mechanism. This eliminates the need for the voice coil motor to output additional thrust when the locking mechanism is released, thus releasing the travel resources of the locking section, further improving magnetic energy utilization efficiency, and reducing motor power consumption. By placing the coil above the permanent magnet array and forming a working air gap between them, the coil remains in the enhanced region corresponding to the main lobe of the magnetic flux density during reciprocating motion in the synthetic magnetic field, ensuring the stability of the driving force output throughout the entire focusing travel range. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the voice coil motor 1 based on an asymmetric Heilbeck permanent magnet array provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the magnetization direction structure of a voice coil motor based on an asymmetric Heilbeck permanent magnet array provided in an embodiment of the present invention; Figure 3 This is a cross-sectional view of a voice coil motor based on an asymmetric Heilbeck permanent magnet array provided in an embodiment of the present invention; Figure 4 This is a graph showing the relationship between stroke and thrust for different voice coil motor structures provided in the embodiments of the present invention; Figure 5 This is a graph showing the relationship between stroke and magnetic flux density for different voice coil motor structures provided in the embodiments of the present invention; Figure 6 This is a schematic diagram of the structure of the voice coil motor 1a based on an asymmetric Heilbeck permanent magnet array provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of the voice coil motor 1b based on an asymmetric Heilbeck permanent magnet array provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of the structure of the voice coil motor 1c based on an asymmetric Heilbeck permanent magnet array provided in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] It should be understood that, when used in this specification and the appended claims, the term "comprising" indicates the presence of the described feature, integral, step, operation, element, and / or component, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof. Furthermore, the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise. The terms "first," "second," and similar words do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Words such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Above," "below," "left," "right," etc., are used only to indicate relative positional relationships, which may change accordingly when the absolute position of the described object changes.

[0020] To keep the following description of the embodiments of the present invention clear and concise, detailed descriptions of some known functions and known components are omitted in this specification.

[0021] Please refer to the following: Figure 1 This invention provides a voice coil motor 1 based on an asymmetric Helbeck permanent magnet array, used to cooperate with a locking mechanism (not shown) to control the focusing motion of a moving group assembly (not shown). The coil 10 is movably disposed within a yoke 20, and a permanent magnet array 30 is disposed inside the yoke 20. The coil 10 and the permanent magnet array 30 are arranged opposite each other, and a working air gap is formed between them. The permanent magnet array 30 has an asymmetric Helbeck structure and includes a first permanent magnet 31, a second permanent magnet 32, and a third permanent magnet 33 arranged sequentially along the moving direction of the coil 10. The length of the first permanent magnet 31 in the coil moving direction is greater than the length of the third permanent magnet 33. The first permanent magnet 31 is disposed on the side closest to the locking mechanism.

[0022] This invention, through setting the permanent magnet array as an asymmetric Heilbeck structure and setting the length of the first permanent magnet to be greater than the length of the third permanent magnet, places the first permanent magnet on the side closer to the locking mechanism, so that the synthesized magnetic field is asymmetrically distributed along the coil movement direction, and the main lobe of the magnetic flux density is shifted away from the locking mechanism. This concentrates the high magnetic flux density region of the air gap magnetic field towards the focusing section, effectively increasing the thrust constant of the focusing section and extending the effective stroke of the focusing section, thereby releasing the stroke resources of the locking section and further improving the magnetic energy utilization efficiency.

[0023] In some embodiments, the yoke 20 includes a bottom wall 21, a top wall 22 disposed opposite to the bottom wall 21, and a first side wall 23 and a second side wall 24 connecting the bottom wall 21 and the top wall 22, and a permanent magnet array 30 is attached to the inner surface of the bottom wall 21 facing the top wall 22. Specifically, the yoke 20 is integrally formed or spliced ​​from magnetically conductive material to form a gate-shaped magnetic circuit frame. The bottom wall 21 extends along the moving direction of the coil 10. The first side wall 23 and the second side wall 24 extend vertically upward from the two sides of the bottom wall 21 in the width direction, respectively. The top wall 22 is connected to the top of the first side wall 23 and the second side wall 24. The bottom wall 21, the first side wall 23, the second side wall 24 and the top wall 22 together form a cavity that runs through the front and back. The permanent magnet array 30 is attached to the inner surface of the bottom wall 21 and located in the cavity. The length of the permanent magnet array 30 along the moving direction of the coil 10 is less than the length of the bottom wall 21 along the moving direction of the coil 10. The permanent magnet array 30 and the inner surface of the top wall 22 maintain a parallel and fixed distance, thereby forming a uniform working air gap above the permanent magnet array 30 that runs through the entire coil movement stroke.

[0024] In some embodiments, the coil 10 is a straight plate type coil, which is movably disposed between the first sidewall 23 and the second sidewall 24, and a movement gap is provided between the coil 10 and the top wall 22 of the yoke 20. Specifically, a movement gap is formed between the inner surface of the coil 10 and the lower surface of the top wall 22 to prevent the coil 10 from interfering with the top wall 22 during movement. A working air gap is formed between the outer surface of the coil 10 and the upper surface of the permanent magnet array 30. After being energized, the coil 10 is driven by the Lorentz force and reciprocates within the working air gap.

[0025] In some embodiments, the voice coil motor 1 further includes a supplementary permanent magnet 40, which is embedded in the yoke 20. The supplementary permanent magnet 40 is positioned below the second permanent magnet 32, and its geometric center along the moving direction of the coil 10 is offset towards the third permanent magnet 33. Specifically, the supplementary permanent magnet 40 is made of the same or different permanent magnet material as the first permanent magnet 31, the second permanent magnet 32, and the third permanent magnet 33. The length of the supplementary permanent magnet 40 along the moving direction of the coil 10 is less than or equal to the length of the second permanent magnet 32 ​​along the moving direction of the coil 10. An embedding groove is provided on the bottom wall 21, and the supplementary permanent magnet 40 is embedded in the embedding groove and fits against the magnetic conductive material of the bottom wall 21. The height of the supplementary permanent magnet 40 along the direction perpendicular to the moving direction of the coil 10 is equal to or less than the thickness of the bottom wall 21. In conventional symmetrical Hellbeck arrays, due to the symmetrical distribution of the magnetic field along the coil movement direction, the middle section corresponding to the second permanent magnet 32 ​​often suffers from insufficient magnetic flux density due to the unsaturated yoke, forming a weak thrust area. In this embodiment of the invention, by embedding the supplementary permanent magnet 40 in the bottom wall 21 and arranging it below the second permanent magnet 32, the excitation source of this weak thrust area can be directly increased. At the same time, due to the asymmetrical Hellbeck structure causing the main lobe of the magnetic field to shift away from the locking mechanism, the weak magnetic field area in the middle section will also shift slightly towards the third permanent magnet 33. Therefore, by setting the geometric center of the supplementary permanent magnet 40 along the coil 10 movement direction to be offset towards the third permanent magnet 33, the magnetic flux of the supplementary permanent magnet 40 can be superimposed on the weak position after the actual magnetic field shift, thereby increasing the air gap magnetic flux density in the middle unsaturated area, that is, enhancing the air gap magnetic flux density in the focusing stroke range, filling the local magnetic flux depression caused by asymmetrical magnetization, and further improving the stability and accuracy of autofocus.

[0026] Please refer to the following: Figure 2 The magnetization directions of the first permanent magnet 31, the second permanent magnet 32, and the third permanent magnet 33 are different. The magnetization direction of the first permanent magnet 31 is set along the side away from the locking mechanism, the magnetization direction of the second permanent magnet 32 ​​is set along the direction perpendicular to the movement of the coil 10, and the magnetization direction of the third permanent magnet 33 is set along the side towards the locking mechanism. The length of the first permanent magnet 31 is greater than the length of the third permanent magnet 33, causing the main lobe of the magnetic flux density in the air gap to shift away from the locking mechanism. Therefore, the Lorentz forces on the left and right sides of the coil 10 along the direction perpendicular to the movement of the coil 10 cancel each other out, and the Lorentz forces on the front and rear sides along the direction of the movement of the coil 10 are superimposed to form the driving force along the direction of the movement of the coil 10. Note that the arrows in the diagram are only used to indicate the magnetization direction of each permanent magnet and do not represent the specific N / S magnetic polarity. The N / S magnetic polarity of each permanent magnet is determined according to the current direction in the coil 10, so that the direction of the Lorentz force on the coil 10 after energization is set as the direction of the movement of the coil 10.

[0027] Please refer to the following: Figure 3 In some embodiments, the lengths of the first permanent magnet 31 and the third permanent magnet 33 satisfy the following condition: 2.5 ≤ H01 / H02 ≤ 3.5; Wherein, H01 represents the length of the first permanent magnet 31, and H02 represents the length of the third permanent magnet 33.

[0028] In this embodiment of the invention, the ratio of the length H01 of the first permanent magnet 31 to the length H02 of the third permanent magnet 33 is used to characterize the degree of magnetic field offset of the asymmetric Heilbeck array. When this ratio is between 2.5 and 3.5, the magnetomotive force amplitudes of the first permanent magnet 31 and the third permanent magnet 33 exhibit a significant asymmetric distribution, and the main lobe of the magnetic field shifts directionally away from the locking mechanism, causing the air gap magnetic flux density in the locking stroke range to be actively weakened while the air gap magnetic flux density in the focusing stroke range is concentrated and enhanced. If the ratio is less than 2.5, it indicates that the magnetic field offset is insufficient, and a high thrust constant remains in the stroke range corresponding to the locking mechanism, preventing the magnetic potential energy of the locking section from being fully released. If the ratio is greater than 3.5, it indicates that the magnetic field offset is excessive, which will cause the magnetic field at the end of the focusing section to decay rapidly, reducing the effective stroke of the voice coil motor and the linearity of the thrust output.

[0029] In some embodiments, a first air gap is formed between the side of the first permanent magnet 31 away from the second permanent magnet 32 ​​and the first sidewall 23, and a second air gap is formed between the side of the third permanent magnet 33 away from the second permanent magnet 32 ​​and the second sidewall 24. Specifically, the first air gap T01 and the second air gap T02 serve as air gap sections in the magnetic circuit, used to adjust the magnetic reluctance distribution of the magnetic circuit and avoid direct contact between the permanent magnet array 30 and the sidewall of the yoke 20, which could lead to increased leakage flux or local magnetic saturation.

[0030] In some embodiments, the length of the first air gap is equal to the length of the second air gap. By configuring the air gaps on both sides to have equal widths, the magnetic reluctance distribution of the magnetic circuit in the direction of coil movement can be made symmetrical, reducing the additional leakage magnetic flux caused by magnetic reluctance asymmetry, improving the utilization rate of the permanent magnet, and at the same time alleviating the saturation phenomenon caused by local magnetic flux accumulation in the yoke 20, making the air gap magnetic flux density more uniformly distributed along the focusing stroke interval.

[0031] In some embodiments, the first air gap and the total stroke of the voice coil motor 1 satisfy the following conditions: 5.8% ≤ T01 / Ht ≤ 15.6%; Where T01 represents the length of the first air gap, and Ht represents the total stroke of the voice coil motor 1.

[0032] In this embodiment of the invention, the ratio of the sum of the lengths T01 of the first air gap and T02 of the second air gap to the total stroke Ht of the voice coil motor is used to characterize the length ratio between the leakage magnetic reluctance section and the excitation section inside the magnetic circuit. When the ratio of the length T01 of the first air gap to the total stroke Ht of the voice coil motor is between 5.8% and 15.6%, the air gap magnetic flux density is dominant, and the voice coil motor can obtain better effective magnetic field performance at this ratio. If the ratio of the length T01 of the first air gap to the total stroke Ht of the voice coil motor is less than 5.8%, it indicates that the gap is set too small, the distance between the permanent magnet array and the side wall of the yoke is reduced, the leakage magnetic reluctance is reduced, the leakage magnetic flux is increased, and it is easy to cause local magnetic saturation of the yoke, which leads to a decrease in the air gap magnetic flux density. At the same time, the narrow gap is extremely sensitive to assembly tolerance and temperature deformation, thus imposing strict requirements on the processing and assembly accuracy. If the ratio of the length T01 of the first air gap to the total stroke Ht of the voice coil motor is greater than 15.6%, it indicates that the gap is set too large, the space for the permanent magnet array is squeezed, the excitation section length is insufficient, which will cause a significant decrease in the air gap magnetic flux density.

[0033] In some embodiments, the length of the first permanent magnet 31, the length of the third permanent magnet 33, and the total stroke of the voice coil motor 1 satisfy the following conditions: 10% ≤ (H01 + H02) / Ht ≤ 22.5%; Wherein, H01 represents the length of the first permanent magnet 31, H02 represents the length of the third permanent magnet 33, and Ht represents the total stroke of the voice coil motor 1.

[0034] In this embodiment of the invention, the ratio of the sum of the length H01 of the first permanent magnet 31 and the length H02 of the third permanent magnet 33 to the total stroke Ht is used to characterize the volume ratio of the two side-by-side magnetizing permanent magnets in the asymmetric Heilbeck permanent magnet array 30. The first permanent magnet 31 and the third permanent magnet 33 perform magnetizing and orientation functions in the magnetic circuit, while the second permanent magnet 32 ​​performs the basic magnetic function. When this ratio is between 10% and 22.5%, the volumes of the three reach optimal balance. This allows for the asymmetric magnetizing effect to be achieved by relying on the first permanent magnet 31 and the third permanent magnet 33, while also providing sufficient basic magnetic flux with the help of the second permanent magnet 32, enabling the air gap magnetic flux density of the motor to reach the globally optimal level. If the ratio is less than 10%, the length of the permanent magnets on both sides is insufficient, the transition of magnetization direction is abrupt, and an effective magnetic mirror effect cannot be formed. The asymmetry of the synthesized magnetic field and the magnetic field gain are limited, making it difficult to give full play to the design advantages of the asymmetric Heilbeck structure. If the ratio is greater than 22.5%, the first permanent magnet 31 and the third permanent magnet 33 will occupy too much axial space, and the volume of the second permanent magnet 32 ​​in the middle will be excessively compressed. Its insufficient volume will directly cause the overall magnetic potential to drop. Even if the magnetic focusing effect is fully utilized, the problem of the overall reduction of air gap magnetic flux density will still occur.

[0035] Please refer to the following: Figures 4 to 5 To verify the effectiveness of the above-mentioned parameter optimization range of the present invention, this application embodiment compares and tests the following four different voice coil motor structures: a non-offset small Hellbeck array scheme, a non-offset large Hellbeck array scheme, an offset Hellbeck array scheme without supplementary permanent magnets, and an offset Hellbeck array scheme with supplementary permanent magnets. Among them, the non-offset small Hellbeck array and the non-offset large Hellbeck array are both symmetrical Hellbeck structures with equal lengths of permanent magnets on both sides. The difference between the two lies in the different proportions of permanent magnet volume, which are below the lower limit of 10% and above the upper limit of 22.5%, respectively. Specifically, as... Figure 4 As shown, in terms of stroke and thrust characteristics, the effective stroke ratio of the un-offset small Helbeck array is 25.38%, the effective stroke ratio of the un-offset large Helbeck array is 32.23%, and the effective stroke ratio of the offset Helbeck array without supplementary permanent magnets is 29.45%. The effective stroke ratio of the offset Helbeck array with supplementary permanent magnets is significantly better than the above three schemes. Figure 5 As shown, in terms of stroke and magnetic flux density characteristics, the locking and focusing sections of the non-offset small Helbeck array and the non-offset large Helbeck array have uniform magnetic flux density distributions, making it impossible to achieve spatial on-demand allocation. The offset Helbeck array, without supplementary permanent magnets, causes the main lobe of magnetic flux density to shift away from the locking mechanism, resulting in a decrease in magnetic flux density in the locking section and an increase in magnetic flux density in the focusing section, but the increase is limited. In this embodiment of the invention, the offset Helbeck array with supplementary permanent magnets, based on the asymmetric magnetic focusing effect, achieves a further increase in magnetic flux density in the focusing section through precise reinforcement by the supplementary permanent magnets, while maintaining a low magnetic flux density in the locking section. Therefore, when all the above parameter relationships are simultaneously satisfied, the thrust of the voice coil motor is in a globally optimal state, and the thrust constant in the focusing section obtains multiple superimposed gains, resulting in a significant increase in the air gap magnetic flux density in the focusing section.

[0036] In some embodiments, after completing the arrangement of the asymmetric Heilbeck permanent magnet array and the offset setting of the supplementary permanent magnets, if the measured values ​​of the actual thrust and effective stroke of the voice coil motor within the focusing stroke range exceed the design specifications, further cost reduction or power consumption reduction design of the voice coil motor can be achieved through parameter optimization. Specifically, keeping the coil operating current constant, the length of the permanent magnet array can be appropriately reduced or the axial length of the voice coil motor can be shortened to reduce the thrust of the voice coil motor back to the target required value, thereby reducing the amount of rare earth permanent magnet material used, achieving a reduction in the overall cost of the motor or a reduction in the overall size of the machine. Furthermore, keeping the permanent magnet structure dimensions constant, the setting value of the maximum drive current can be lowered. With the help of the higher thrust constant obtained after optimization, the voice coil motor can still meet the performance requirements of focusing acceleration and locking release force under a smaller operating current condition, thereby reducing the power consumption and operating temperature rise of the voice coil motor and extending the continuous working time of the camera lens in video recording mode.

[0037] The above embodiments illustrate the present invention using a straight-plate asymmetric Helbeck permanent magnet array combined with a straight-plate coil and a single air gap structure as an example, but the present invention is not limited thereto. In addition to the above embodiments, the present invention can also be implemented using the following alternative structures.

[0038] Please refer to the following: Figure 6 In some embodiments, the voice coil motor 1a adopts a double air gap structure with a straight-plate asymmetric Heilbeck permanent magnet and a straight-plate coil. Specifically, the voice coil motor 1a includes a coil 10a, a yoke 20a, a permanent magnet array 30a, and a supplementary permanent magnet 40a. The yoke 20a includes a bottom wall 21a extending along the moving direction of the coil 10a, a top wall 22a disposed opposite to the bottom wall 21a, a first side wall 23a and a second side wall 24a connecting the bottom wall 21a and the top wall 22a, and an intermediate wall 25a disposed between the bottom wall 21a and the top wall 22a. The intermediate wall 25a is connected to the first side wall 23a and the second side wall 24a respectively. Supplementary permanent magnets 40a are respectively embedded in the bottom wall 21a and top wall 22a of the yoke 20a. The permanent magnet array 30a includes a first permanent magnet array attached to the inner side of the bottom wall 21a and a second permanent magnet array attached to the inner side of the top wall 22a. The first and second permanent magnet arrays include a first permanent magnet 31a, a second permanent magnet 32a, and a third permanent magnet 33a sequentially along the moving direction of the coil 10a. The length of the first permanent magnet 31a is greater than the length of the third permanent magnet 33a, and the first permanent magnet 31a is located on the side closer to the locking mechanism. The coil 10a is a straight plate type coil, movably disposed between the first side wall and the second side wall, and the coil 10a is spaced apart from the bottom wall 21a, the top wall 22a, and the middle wall 25a. The coil 10a forms working air gaps with the permanent magnet arrays 30a on both sides, respectively. Specifically, one side of the coil 10a forms a first working air gap with the first permanent magnet array, and the other side forms a second working air gap with the second permanent magnet array, thus forming a double-air-gap structure. When the coil 10a is energized, it is simultaneously driven by Lorentz forces in both working air gaps. The driving force is the sum of the Lorentz forces generated in both air gaps, resulting in greater thrust output under the same current conditions. Compared to a single-air-gap structure, the double-air-gap structure allows both sides of the coil 10a to participate in electromagnetic drive, resulting in higher utilization of the permanent magnets and greater thrust density. This makes it suitable for focusing scenarios in photographic lenses that require high thrust and response speed.

[0039] Please refer to the following: Figure 7In some embodiments, the voice coil motor 1b adopts a double air gap structure with a straight-plate asymmetric Heilbeck permanent magnet and a cylindrical coil. Specifically, the voice coil motor 1b includes a coil 10b, a yoke 20b, a permanent magnet array 30b, and a supplementary permanent magnet 40b. The yoke 20b includes a bottom wall 21b extending along the moving direction of the coil 10b, a top wall 22b opposite to the bottom wall 21b, a first side wall 23b and a second side wall 24b connecting the bottom wall 21b and the top wall 22b, and an intermediate wall 25b disposed between the bottom wall 21b and the top wall 22b. The intermediate wall 25b is connected to the first side wall 23b and the second side wall 24b respectively. Supplementary permanent magnets 40b are respectively embedded in the bottom wall 21b and top wall 22b of the yoke 20b. The permanent magnet array 30b includes a first permanent magnet array fitted to the inner side of the bottom wall 21b and a second permanent magnet array fitted to the inner side of the top wall 22b. The first and second permanent magnet arrays sequentially include a first permanent magnet 31b, a second permanent magnet 32b, and a third permanent magnet 33b along the moving direction of the coil 10b. The length of the first permanent magnet 31b is greater than the length of the third permanent magnet 33b, and the first permanent magnet 31b is located on the side closer to the locking mechanism. The coil 10b is a cylindrical coil, movably disposed between the first side wall and the second side wall, and the coil 10b is spaced apart from the bottom wall 21b, the top wall 22b, and the middle wall 25b. Working air gaps are formed between the two sides of the coil 10b and the permanent magnet arrays 30b on both sides, respectively. That is, a first working air gap is formed between the outer periphery of the coil 10b and the first permanent magnet array, and a second working air gap is formed between the outer periphery of the coil 10b and the second permanent magnet array, thus constituting a double air gap structure. In this embodiment, the cylindrical coil has a longer effective stroke in the magnetic field, which can obtain a larger Lorentz force. At the same time, the double air gap structure allows both the left and right sides of the coil 10b to participate in the drive, combining the advantages of the long effective side of the cylindrical coil and the high thrust density of the double air gap, further improving the thrust output capability of the motor.

[0040] Please refer to the following: Figure 8In some embodiments, the voice coil motor 1c employs an arc-shaped air gap structure with an arc-shaped asymmetric Helbeck permanent magnet and a cylindrical coil. Specifically, the voice coil motor 1c includes a coil 10c, a yoke 20c, a permanent magnet array 30c, and a supplementary permanent magnet 40c. The yoke 20c has a semi-cylindrical structure, and the permanent magnet array 30c is attached to the inner wall of the yoke 20c. The supplementary permanent magnet 40c is embedded within the yoke 20c. The permanent magnet array 30c is an arc-shaped Helbeck permanent magnet array, and its shape and size match the yoke 20c. The permanent magnet array 30c has a first permanent magnet 31c, a second permanent magnet 32c, and a third permanent magnet 33c arranged sequentially along the coil movement direction. The length of the first permanent magnet 31c is greater than the length of the third permanent magnet 33c, and the first permanent magnet 31c is located on the side closer to the locking mechanism. The coil 10c is a cylindrical coil, movably disposed within the yoke 20c, and an annular working air gap is formed between the outer circumferential surface of the coil 10c and the inner circumferential surface of the permanent magnet array 30c. In this embodiment, the arc-shaped structure is beneficial for making full use of the limited radial space inside the camera lens, resulting in a smaller cross-sectional area of ​​the voice coil motor, making it suitable for camera lenses with limited radial dimensions but relatively ample axial space.

[0041] Secondly, the present invention provides a photographic lens, which includes a moving group assembly, a locking mechanism, and a voice coil motor based on an asymmetric Heilbeck permanent magnet array as described above. The voice coil motor is fixedly connected to the moving group assembly and is used to drive the moving group assembly to move along the coil movement direction when energized. The locking mechanism is used to lock the moving group assembly when de-energized and to release the moving group assembly when energized.

[0042] In this embodiment of the invention, the voice coil motor coil and the moving part assembly are integrated. When the voice coil motor is energized, it generates a driving force, which drives the moving part assembly to complete the focusing motion. When the camera lens is powered off and stopped, the locking mechanism locks the moving part assembly in the locked position using permanent magnet attraction, thereby limiting the movement of the moving part assembly and preventing lens displacement due to vibration or drops. When the camera lens needs to perform a focusing action, the locking mechanism releases the moving part assembly by applying current to generate a repulsive force or eliminate the attraction. The voice coil motor then drives the moving part assembly to reciprocate along the coil movement direction to complete the focus adjustment. This camera lens, through the voice coil motor, allows the magnetic flux density and thrust of the locking mechanism to be reduced in the corresponding stroke segment, while maintaining a higher air gap magnetic flux density in the focusing segment. This allows for a larger effective focusing stroke without increasing the lens size, facilitating miniaturization and low-power design of the camera lens.

[0043] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the scope of disclosure involved in the above embodiments is not limited to technical solutions formed by specific combinations of the above technical features, but should also cover other technical solutions formed by arbitrary combinations of the above technical features or their equivalent features without departing from the above-disclosed concept. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0044] Furthermore, while the operations are described in a specific order, this should not be construed as requiring these operations to be performed in the specific order shown or in sequential order. In certain circumstances, multitasking and parallel processing may be advantageous. Similarly, while several specific implementation details are included in the above discussion, these should not be construed as limiting the scope of the invention. Certain features described in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments.

Claims

1. A voice coil motor based on an asymmetric Heilbeck permanent magnet array, used in conjunction with a locking mechanism to control the focusing motion of a moving group assembly, characterized in that, The voice coil motor includes: a coil, a yoke, and an array of permanent magnets; The coil is movably disposed within the yoke, and the permanent magnet array is disposed on the inner side of the yoke. The coil and the permanent magnet array are disposed opposite each other, and a working air gap is formed between the coil and the permanent magnet array. The permanent magnet array is an asymmetric Helbeck structure. The permanent magnet array includes a first permanent magnet, a second permanent magnet, and a third permanent magnet arranged sequentially along the coil movement direction. The length of the first permanent magnet in the coil movement direction is greater than the length of the third permanent magnet. The first permanent magnet is disposed on the side close to the locking mechanism. The lengths of the first permanent magnet and the third permanent magnet satisfy the following condition: 2.5 ≤ H01 / H02 ≤ 3.5; Wherein, H01 represents the length of the first permanent magnet and H02 represents the length of the third permanent magnet.

2. The voice coil motor based on an asymmetric Heilbeck permanent magnet array as described in claim 1, characterized in that, The yoke includes a bottom wall, a top wall opposite to the bottom wall, and a first side wall and a second side wall connecting the bottom wall and the top wall. The permanent magnet array is attached to the inner surface of the bottom wall facing the top wall.

3. The voice coil motor based on an asymmetric Heilbeck permanent magnet array as described in claim 2, characterized in that, The coil is a straight plate type coil, which is movably disposed between the first side wall and the second side wall, and a movement gap is provided between the coil and the top wall of the yoke.

4. The voice coil motor based on an asymmetric Heilbeck permanent magnet array as described in claim 2, characterized in that, It also includes a supplementary permanent magnet, which is embedded in the yoke and is located below the second permanent magnet, with the supplementary permanent magnet offset from the geometric center of the coil movement direction toward the third permanent magnet.

5. The voice coil motor based on an asymmetric Heilbeck permanent magnet array as described in claim 2, characterized in that, A first air gap is formed between the side of the first permanent magnet away from the second permanent magnet and the first sidewall, and a second air gap is formed between the side of the third permanent magnet away from the second permanent magnet and the second sidewall.

6. The voice coil motor based on an asymmetric Heilbeck permanent magnet array as described in claim 5, characterized in that, The length of the first air gap is equal to the length of the second air gap.

7. The voice coil motor based on an asymmetric Heilbeck permanent magnet array as described in claim 6, characterized in that, The first air gap and the total stroke of the voice coil motor satisfy the following conditions: 5.8% ≤ T01 / Ht ≤ 15.6%; Wherein, T01 represents the length of the first air gap, and Ht represents the total stroke of the voice coil motor.

8. The voice coil motor based on an asymmetric Heilbeck permanent magnet array as described in claim 1, characterized in that, The lengths of the first permanent magnet, the third permanent magnet, and the total stroke of the voice coil motor satisfy the following conditions: 10% ≤ (H01 + H02) / Ht ≤ 22.5%; Wherein, H01 represents the length of the first permanent magnet, H02 represents the length of the third permanent magnet, and Ht represents the total stroke of the voice coil motor.

9. A photographic lens, characterized in that, The device includes a moving group assembly, a locking mechanism, and a voice coil motor based on an asymmetric Heilbeck permanent magnet array as described in any one of claims 1 to 8. The voice coil motor is fixedly connected to the moving group assembly and is used to drive the moving group assembly to move along the coil movement direction when energized. The locking mechanism is used to lock the moving group assembly when de-energized and to release the moving group assembly when energized.

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