Rotary magnetic encoder

Abstract

A rotary magnetic encoder of an embodiment comprises: a shaft which rotationally moves and has a first end portion on which a first screw thread is formed and a second end portion which is opposite to the first end portion and on which a second screw thread is formed; a ring magnet which is coupled to the shaft so as to move in the axial direction of the shaft while rotating along with the shaft; a case comprising a first female screw which is male-female coupled to the first screw thread and a second female screw which is male-female coupled to the second screw thread; a substrate comprising an outer surface coupled to the case and a through hole into which the shaft is inserted; and a sensor which is arranged on the substrate and senses a magnetic field that varies according to the rotation of the shaft.

Description

Rotary magnetic encoder

[0001] The embodiment relates to a rotary magnetic encoder.

[0002] Rotary encoders track the rotation and rotation of a motor shaft, generating digital information about its position and movement. Rotary encoders can be incremental, absolute, magnetic, or optical, and all perform the same function.

[0003] In particular, rotary magnetic encoders operate stably even in environments with severe shock or vibration or high temperatures, are resistant to external environments such as dust, and are small and inexpensive. Therefore, they are widely used in sophisticated and complex devices that require motion control, such as automobile anti-lock brake systems (ABS), industrial automation, medical equipment, and robots. In addition, types of rotary magnetic encoders include incremental, absolute, non-contact, bearing, and rotary types.

[0004] In these encoders, research is being conducted to increase the size to derive the absolute rotation angle rather than the relative rotation angle of the shaft.

[0005] The embodiment provides a rotary magnetic encoder that is compact and capable of detecting the absolute rotation angle of a shaft with excellent performance.

[0006] A rotary magnetic encoder according to an embodiment may include a shaft that rotates, has a first thread formed thereon and a first end, and a second thread formed thereon and a second end opposite the first end; a ring magnet coupled to the shaft so as to rotate together with the shaft and move vertically in an axial direction of the shaft; a case that includes a first female screw that is male-female coupled with the first thread and a second female screw that is male-female coupled with the second thread; a substrate that includes an outer surface coupled to the case and a through hole into which the shaft is inserted; and a sensor that is disposed on the substrate and senses a magnetic field that changes according to the rotation of the shaft.

[0007] For example, the shaft may include a first intermediate portion positioned between the first end and the second end and to which the ring magnet is coupled; and a second intermediate portion positioned between the first intermediate portion and the second end and inserted into the through hole.

[0008] For example, the case may include an upper plate having the first female screw formed thereon; a lower plate having the second female screw formed thereon; and a body that is coupled with the upper plate and the lower plate to define a receiving hole that receives the first and second intermediate portions of the shaft, the ring magnet, the substrate, and the sensor.

[0009] For example, the through hole of the substrate may be located at the center of the substrate.

[0010] For example, the through hole of the substrate may be positioned offset to one side from the center of the substrate.

[0011] For example, the inner diameter of the through hole and the outer diameter of the shaft may be the same.

[0012] For example, the inner diameter of the through hole may be larger than the outer diameter of the shaft.

[0013] For example, the outer surface of the second intermediate portion may include a third screw thread.

[0014] For example, the rotary magnetic encoder may further include a bearing disposed between the inner surface of the through hole and the outer surface of the second intermediate portion.

[0015] For example, the inner surface of the bearing may include a third female screw that is male-female coupled with the third screw thread.

[0016] For example, the through hole may have the shape of a fourth female screw that is male-female coupled with the third screw thread.

[0017] For example, the rotary magnetic encoder may further include a guide ring disposed between the inner surface of the through hole and the outer surface of the second intermediate portion, and including a fifth female screw that is male-female coupled with the third screw thread.

[0018] For example, the ring magnet may be a bipolar magnet or a multipolar magnet.

[0019] For example, the shaft may have an investment ratio of about 1. /

[0020] For example, the guide ring may have an investment ratio of about 1.

[0021] For example, the substrate may have an annular planar shape.

[0022] For example, the rotation angle of the shaft can be measured by converting the change in the magnetic field sensed by the sensor into Arctan.

[0023] For example, the absolute rotation angle of the shaft can be obtained by deriving a combination of the degree to which the shaft rotates and the distance moved in the axial direction from the vector and scalar changes of the magnetic field sensed by the sensor.

[0024] A rotary magnetic encoder according to an embodiment can increase the degree of freedom in component arrangement, is compact, can accurately derive the rotation angle of a shaft, and can obtain an absolute rotation angle, so that when the driving power of the encoder is turned off and then the driving power is supplied to the encoder again, there is no need to re-track the rotation angle of the shaft with respect to a reference point.

[0025] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention belongs from the description below.

[0026] Figures 1a, 1b and 1c illustrate a front perspective view, a plan view and a top perspective view, respectively, of a rotary magnetic encoder according to an embodiment.

[0027] Figure 2 shows a perspective view of the shaft illustrated in Figures 1a to 1c.

[0028] Figure 3 shows a perspective view of the ring magnet illustrated in Figure 1.

[0029] Figure 4 shows a plan view of the substrate illustrated in Figure 1.

[0030] Fig. 5 shows a perspective view of an embodiment of the case illustrated in Fig. 1.

[0031] Figure 6a shows a plan view of an encoder according to one embodiment.

[0032] Fig. 6b is a graph showing the strength of the magnetic field sensed by the encoder illustrated in Fig. 6a.

[0033] Fig. 7a shows a plan view of an encoder according to another embodiment.

[0034] Figure 7b is a graph showing the strength of the magnetic field sensed by the encoder illustrated in Figure 7a.

[0035] Figure 8 shows a local perspective view of an encoder according to another embodiment.

[0036] Figure 9 shows a perspective view of the shaft illustrated in Figure 8.

[0037] Figure 10 shows a perspective view of the substrate illustrated in Figure 8.

[0038] Figure 11 shows a local perspective view of an encoder according to another embodiment.

[0039] Fig. 12 shows a perspective view of one embodiment of the bearing illustrated in Fig. 11.

[0040] Fig. 13 shows a perspective view of another embodiment of the bearing illustrated in Fig. 11.

[0041] Figure 14 shows a local perspective view of an encoder according to another embodiment.

[0042] Fig. 15 shows a perspective view of the guide ring illustrated in Fig. 14.

[0043] Figures 16a and 16b each show a perspective view of a ring magnet according to another embodiment.

[0044] Figure 17 is a graph showing changes in the magnetic field sensed by the sensor.

[0045] Figures 18a and 18b are graphs of the sensed magnetic field converted into Arctan.

[0046] Figure 19 is a graph that actually simulates the performance of an encoder according to an embodiment.

[0047] Figure 20 is a diagram explaining the change in investment rate and magnetic field lines.

[0048] Figure 21a is a drawing explaining the change in magnetic field lines when the shaft is implemented with steel or the like having a high investment rate.

[0049] Figure 21b is a diagram explaining the change in magnetic field lines when the shaft has an investment rate approaching 1.

[0050] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated and described in the drawings. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0051] Terms including ordinal numbers, such as "second," "first," etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, a second component may be referred to as a "first component," and similarly, a first component may also be referred to as a "second component." The term "and / or" includes a combination of multiple related items described herein or any of multiple related items described herein.

[0052] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0053] In the description of the embodiments, the description that each layer (film), region, pattern or structure is formed "on" or "under" the substrate, each layer (film), region, pad or pattern includes both being formed directly or through the interposition of another layer. The reference to "on" or "under" each layer is explained based on the drawings. In addition, the thickness or size of each layer (film), region, pattern or structure in the drawings may be modified for clarity and convenience of explanation, and therefore does not entirely reflect the actual size.

[0054] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0055] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0056] Hereinafter, embodiments will be described in detail with reference to the attached drawings. Regardless of the drawing reference numerals, identical or corresponding components will be given the same reference numerals, and redundant descriptions thereof will be omitted. In addition, although the embodiments are described using the Cartesian coordinate system, it goes without saying that the embodiments may be described using other coordinate systems. In the Cartesian coordinate system, the x-axis, y-axis, and z-axis illustrated in each drawing are orthogonal to each other, but the embodiments are not limited thereto. The x-axis, y-axis, and z-axis may also intersect each other.

[0057] FIG. 1a, FIG. 1b and FIG. 1c respectively show a front perspective view, a plan view and a top perspective view of a rotary magnetic encoder (hereinafter referred to as “encoder”) (100A) according to an embodiment.

[0058] The encoder (100A) illustrated in FIGS. 1A to 1C may include a shaft (110A), a ring magnet (120A), a sensor (130), a printed circuit board (PCB) (140A), and a case (150).

[0059] Fig. 2 shows a perspective view of the shaft (110A) shown in Figs. 1a to 1c, Fig. 3 shows a perspective view of the ring magnet (120A) shown in Fig. 1, Fig. 4 shows a plan view of the substrate (140A) shown in Fig. 1, and Fig. 5 shows a perspective view of an embodiment of the case (150) shown in Fig. 1. To aid understanding, parts that are not visible in Fig. 5 are indicated with dotted lines.

[0060] Each part of the encoder (100A) according to the embodiment is described in detail as follows.

[0061] The shaft (110A) rotates in the direction of the arrow (A) and includes a first end (E1) and a second end (E2) opposite the first end (E1). A first screw thread (SW1) may be formed at the first end (E1), and a second screw thread (SW2) may be formed at the second end (E2). Each of the first and second screw threads (SW1, SW2) functions as a male screw.

[0062] In addition, the shaft (110A) may further include first and second intermediate portions (C1, C2). The first intermediate portion (C1) is defined as a portion positioned between the first end (E1) and the second end (E2) and to which the ring magnet (120A) is coupled. The ring magnet (120A) may be fixedly coupled to the first intermediate portion (C1) so as to rotate together with the shaft (110A). The second intermediate portion (C2) may be a portion positioned between the first intermediate portion (C1) and the second end (E2) and may be inserted into the second through hole (TH2) of the substrate (140A). With the second intermediate portion (C2) penetrating the second through hole (TH2), the shaft (110A) may be raised and lowered in the axial direction (i.e., the z-axis direction) while rotating together with the ring magnet (120A).

[0063] According to one embodiment, the second intermediate portion (C2) of the shaft (110A) illustrated in FIG. 2 may not have any screw thread.

[0064] The shaft (110A) may have an investment rate close to 1, that is, approximately 1. For example, the shaft (110A) may be made of a material having an investment rate close to 1, such as aluminum or plastic.

[0065] The length of each of the first end (E1) and the second end (E2) in the z-axis direction may be 16% to 28% of the total length of the shaft (110A). For example, when the total length of the shaft (110A) in the z-axis direction is 8 mm to 10 mm, the length of each of the first end (E1) and the second end (E2) in the z-axis direction may be 1.5 mm to 2.5 mm, but the embodiment is not limited thereto.

[0066] The ring magnet (120A) can be coupled to the shaft (110A) so as to rotate together with the shaft (110A) and move vertically in the axial direction (i.e., z-axis direction) of the shaft (110A). The ring magnet (120A) has a first through hole (TH1) into which the shaft (110A) is inserted. The first inner circumferential surface (IS1) of the ring magnet (120A) is fixedly coupled to the outer circumferential surface (110S) of the shaft (110A). That is, the first inner diameter (ID1) of the ring magnet (120A) can be the same as the first outer diameter (OD11) of the shaft (110A). The first outer surface (OS1) of the ring magnet (120A) is positioned apart from the inner surface of the case (150), so that when the ring magnet (120A) rotates, it does not collide with the inner surface of the case (150).

[0067] According to an embodiment, the ring magnet (120A) may be a bipolar magnet having a pair of N poles and S poles. For example, the ring magnet (120A) may be implemented with a neodymium (Nd) magnet (e.g., N35, N42, etc.) or ferrite (MnZn).

[0068] The sensor (130) is placed on the substrate (140A) and can sense a magnetic field that changes according to the rotation of the shaft (110A). For example, the sensor (130) may be a one-dimensional sensor or a two-dimensional sensor arranged in an array form, or may be a single three-dimensional sensor.

[0069] According to an embodiment, the ring magnet (120A) is arranged in the axial direction (i.e., z-axis direction) of the shaft (110A), while the sensor (130) may be arranged in an axis other than the z-axis.

[0070] The case (150) may include a first female screw (BW1) that is male-female coupled with a first screw thread (SW1) and a second female screw (BW2) that is male-female coupled with a second screw thread (SW2).

[0071] Referring to FIG. 5, the case (150) may include an upper plate (UP), a body (CP), and a lower plate (LP).

[0072] The upper part (UP) has a first female screw (BW1) that is connected to the first screw thread (SW1), and the lower part (LP) has a second female screw (BW2) that is connected to the second screw thread (SW2).

[0073] The body (CP) is combined with the upper plate (UP) and the lower plate (LP) to define a receiving hole that receives the first and second intermediate portions (C1, C2) of the shaft (110A), the ring magnet (120A), the sensor (130), and the substrate (140A).

[0074] To aid understanding, the illustration of the upper plate (UP) of the case (150) is omitted in each of FIG. 1b and FIG. 1c.

[0075] The substrate (140A) may include a second outer surface (OS2) coupled to the case (150) and a second through hole (TH2) into which the shaft (110A) is inserted. Even if the shaft (110A) rotates, the substrate (140A) may not rotate, so that the second outer surface (OS2) of the substrate (140A) may be fixedly coupled to the inner surface of the case (150).

[0076] According to an embodiment, the substrate (140A) may have a circular plane shape as shown in FIG. 4, but the embodiment is not limited thereto.

[0077] In the case of the substrate (140A) according to one embodiment, as shown in FIG. 4, no female screw is formed on the second inner surface (IS2) of the second through hole (TH2).

[0078] According to an embodiment, the substrate (140A) can be implemented with a general PCB material, for example, FR-4.

[0079] To aid understanding, the first outer diameter (OD11) illustrated in FIG. 2 is illustrated with a dotted line in FIG. 4. According to an embodiment, as illustrated in FIG. 4, the second inner diameter (ID21) of the second through hole (TH2) may be larger than the first outer diameter (OD11) of the shaft (110A) by a clearance distance (ΔD). In this way, when the second inner diameter (ID21) is larger than the first outer diameter (OD11) by a clearance distance (ΔD), even if no screw thread is formed in the second middle portion (C2) of the shaft (110A), the shaft (110A) inserted into the second through hole (TH2) can rotate smoothly while the substrate (140A) is fixed.

[0080] FIG. 6a shows a plan view of an encoder according to one embodiment, and FIG. 6b is a graph showing the intensity of a magnetic field sensed by the encoder shown in FIG. 6a, where the horizontal axis represents the rotation angle of the shaft and the vertical axis represents the magnetic field.

[0081] Fig. 7a shows a plan view of an encoder according to another embodiment, and Fig. 7b is a graph showing the intensity of a magnetic field sensed by the encoder shown in Fig. 7a, in which the horizontal axis represents the rotation angle of the shaft and the vertical axis represents the magnetic field.

[0082] For convenience of explanation, only the shaft (110A), ring magnet (120A), sensor (130), and substrate (140A) of the encoder are illustrated in FIGS. 6A and 7A, respectively. The shaft (110A), ring magnet (120A), sensor (130), and substrate (140A) illustrated in FIGS. 6A and 7A, respectively, correspond to the shaft (110A), ring magnet (120A), sensor (130), and substrate (140A) illustrated in FIGS. 1A to 1C, respectively, and therefore, the same reference numerals are used and redundant descriptions are omitted.

[0083] According to one embodiment, as illustrated in FIG. 6A, the second through hole (TH2) of the substrate (140A) may be positioned at the center of the substrate (140A). Since the shaft (110A) passes through the second through hole (TH2) and the ring magnet (120A) is coupled to the shaft (110A), it can be seen that the shaft (110A) and the ring magnet (120A) are also positioned at the center of the substrate (140A), as illustrated in FIG. 6A.

[0084] In another embodiment, as illustrated in FIG. 7A, the second through hole (TH2) of the substrate (140A) may be positioned offset from the center of the substrate (140A) to one side. Since the shaft (110A) passes through the second through hole (TH2) and the ring magnet (120A) is coupled to the shaft (110A), the shaft (110A) and the ring magnet (120A) may also be positioned offset from the center of the substrate (140A) to one side, as illustrated in FIG. 7A.

[0085] When the second through hole (TH2) is arranged as shown in FIG. 6a and the shaft (110A) rotates by a first predetermined angle (e.g., 360°), the change in the magnetic field sensed by the sensor (130) is as shown in FIG. 6b.

[0086] When the second through hole (TH2) is arranged as shown in Fig. 7a and the shaft (110A) rotates by a first predetermined angle, the change in the magnetic field sensed by the sensor (130) is as shown in Fig. 7b.

[0087] It can be seen that the amplitude (AM2) of the magnetic field illustrated in Fig. 7b is amplified more significantly than the amplitude (AM1) of the magnetic field illustrated in Fig. 6b. This is because the overall rotation radius of the encoder illustrated in Fig. 7a is longer than that of the encoder illustrated in Fig. 6a by the amount that the second through hole (TH2) is positioned in a deflected manner.

[0088] Unlike the encoder (100A) according to the above-described embodiment to allow the shaft to rotate while the substrate is fixed, the encoders (100B to 100D) according to other embodiments may have various configurations.

[0089] Hereinafter, the encoders (100B to 100D) according to the embodiment will be described with reference to the attached drawings. Parts of the configuration of the encoders (100B to 100D) not described below may be applied to the description of the encoder (100A) according to the embodiment described above.

[0090] FIG. 8 shows a local perspective view of an encoder (100B) according to another embodiment, FIG. 9 shows a perspective view of a shaft (110B) shown in FIG. 8, and FIG. 10 shows a perspective view of a substrate (140B) shown in FIG. 8.

[0091] The encoder (100B) illustrated in FIG. 8 may include a shaft (110B), a ring magnet (120A), a sensor (130), a substrate (140B), and a case (150). Except for the different shapes of the shaft (110B) and the substrate (140B), the encoder (100B) illustrated in FIG. 8 is identical to the encoder (100A) illustrated in FIGS. 1A to 1C, and therefore only the parts that are different from the encoder (100A) will be described. That is, the ring magnet (120A) and the sensor (130) are identical to the ring magnet (120A) and the sensor (130) illustrated in FIGS. 1A to 1C, respectively.

[0092] Unlike the shaft (110A) illustrated in FIG. 2, the second intermediate portion (C2) of the shaft (110B) illustrated in FIG. 9 may include a third screw thread (SW3) formed on the outer surface (110S). In this case, the length in the z-axis direction of the portion where the third screw thread (SW3) is formed may be the same as the length in the z-axis direction of the portion where the first or second screw thread (SW1, SW2) is formed.

[0093] Unlike the substrate (140A) illustrated in Fig. 4, in the substrate (140B) illustrated in Fig. 10, a fourth female screw (BW4) is formed on the second inner peripheral surface (IS2) of the second through hole (TH2). The fourth female screw (BW4) can be connected to the third screw line (SW3) formed on the outer peripheral surface (110S) of the second intermediate portion (C2).

[0094] In this case, the second inner diameter (ID22) of the second through hole (TH2) and the first outer diameter (OD12) of the shaft (110B) may be the same. That is, in the case of FIG. 8, the clearance distance (ΔD) illustrated in FIG. 4 is 0. Even if the clearance distance (ΔD) between the outer circumferential surface (110S) of the shaft (110B) and the second inner circumferential surface (IS2) of the second through hole (TH2) is 0, the second outer circumferential surface (OS2) of the substrate (140B) is fixed to the inner surface of the case (150), and the third screw thread (SW3) formed in the second middle portion (C2) of the shaft (110B) and the fourth female screw thread (BW4) formed in the second through hole (TH2) are male-female coupled, so that the substrate (140B) is fixed and only the shaft (110B) can rotate.

[0095] Fig. 11 shows a partial perspective view of an encoder (100C) according to another embodiment, and Fig. 12 shows a perspective view of an embodiment (160A) of a bearing (160) illustrated in Fig. 11. In Fig. 11, the illustration of the case (150) is omitted.

[0096] The encoder (100C) illustrated in FIG. 11 may include a shaft (110A), a ring magnet (120A), a sensor (130), a substrate (140A), a case (150), and a bearing (160). Except for further including the bearing (160), the encoder (100C) illustrated in FIG. 11 is identical to the encoder (100A) illustrated in FIGS. 1A to 1C, and therefore only the parts that are different from the encoder (100A) will be described. That is, the shaft (110A), the ring magnet (120A), the sensor (130), the substrate (140A), and the case (150) correspond to the shaft (110A), the ring magnet (120A), the sensor (130), the substrate (140A), and the case (150) illustrated in FIGS. 1A to 1C, respectively, and therefore, a duplicate description will be omitted.

[0097] The bearing (160) can be arranged between the second inner surface (IS2) of the second through hole (TH2) illustrated in FIG. 4 and the outer surface (110S) of the second intermediate portion (C2) illustrated in FIG. 2. The third outer surface (OS3) of the bearing (160A) illustrated in FIG. 12 is fixedly coupled to the second inner surface (IS2) of the second through hole (TH2), and the third inner surface (IS3) of the bearing (160A) is fixedly coupled to the outer surface (110S) of the shaft (110A) illustrated in FIG. 2.

[0098] At this time, the bearing (160A) may include a first part (P1), a second part (P2), and a ball (or bead) (not shown). When the shaft (110A) rotates, the ball may be placed between the first part (P1) and the second part (P2) so that the first part (P1) rotates together with the shaft (110A), while the second part (P2) does not rotate.

[0099] The bearing (160A) has a third through hole (TH31) through which the shaft (110A) passes.

[0100] The clearance (ΔD) illustrated in Fig. 4 may correspond to the thickness (T1) of the bearing (160A) illustrated in Fig. 12. In this way, when the bearing (160A) is arranged, friction between the outer surface (110S) of the shaft (110A) and the second inner surface (IS2) of the second through hole (TH2) of the substrate (140A) can be avoided when the shaft (110A) rotates.

[0101] Fig. 13 shows a perspective view of another embodiment (160B) of the bearing (160) illustrated in Fig. 11.

[0102] A third female screw (BW3) may be formed on the inner surface of the bearing (160B). In this case, the shaft (110A) in the encoder (100C) illustrated in FIG. 11 may be replaced with the shaft (110B) illustrated in FIG. 9. In this case, the third female screw (BW3) illustrated in FIG. 13 may be male-female coupled with the third screw thread (SW3) illustrated in FIG. 9. The bearing (160B) has a third through hole (TH32) through which the shaft (110B) passes.

[0103] Therefore, when the bearing (160B) is implemented as shown in FIG. 13, the first part (P1) can rotate not only by the ball of the bearing (160A) but also by the male-female coupling between the third screw thread (SW3) and the third female screw thread (BW3).

[0104] The clearance distance (ΔD) illustrated in FIG. 4 may correspond to the thickness (T2) of the bearing (160B) illustrated in FIG. 13.

[0105] Fig. 14 shows a local perspective view of an encoder (100D) according to another embodiment, and Fig. 15 shows a perspective view of a guide ring (170) illustrated in Fig. 14.

[0106] The encoder (100D) illustrated in FIG. 14 may include a shaft (110B), a ring magnet (120A), a sensor (130), a substrate (140A), a case (150), and a guide ring (170). Except for further including the guide ring (170) and including the substrate (140A) illustrated in FIG. 4 instead of the substrate (140B) illustrated in FIG. 10, the encoder (100D) illustrated in FIG. 14 is identical to the encoder (100B) illustrated in FIG. 8, and therefore only the parts that are different from the encoder (100B) will be described. That is, the shaft (110B), the ring magnet (120A), the sensor (130), and the case (150) correspond to the shaft (110B), the ring magnet (120A), the sensor (130), and the case (150) illustrated in FIG. 8, respectively, and therefore, the same reference numerals are used and redundant descriptions are omitted. In addition, the substrate (140A) illustrated in FIG. 14 corresponds to the substrate (140A) illustrated in FIG. 4.

[0107] The clearance distance (ΔD) illustrated in Fig. 4 corresponds to the thickness (T3) of the guide ring (170) illustrated in Fig. 15.

[0108] The guide ring (170) is arranged between the second inner circumference (IS2) of the second through-hole (TH2) illustrated in FIG. 4 and the outer circumference (110S) of the second intermediate portion (C2). At this time, as illustrated in FIG. 15, the guide ring (170) may include a fifth female screw (BW5) that is male-female coupled with the third screw thread (SW3). The fourth outer circumference (OS4) of the guide ring (170) is fixedly coupled with the second inner circumference (IS2) of the second through-hole (TH2) illustrated in FIG. 4, and since the third screw thread (SW3) and the fifth female screw thread (BW5) are male-female coupled, the substrate (140A) can be fixed without rotating while the shaft (110B) rotates. The guide ring (170) may include a fourth through-hole (TH4) into which the shaft (110B) is inserted.

[0109] According to an embodiment, the investment rate of the guide ring (170) may be approximately 1, and may be implemented with the same material as the shaft (110A, 110B) described above.

[0110] Meanwhile, a change in the magnetic field sensed by the sensor (130) can be transmitted to a control unit (not shown) disposed externally via a cable (not shown), and a driving current for driving the sensor (130) required for the sensor (130) to detect a change in the magnetic field can be provided to the sensor (130) via a cable from the outside of the encoder (100A to 100D). To this end, the case (150) may further include a connection opening (OP) as illustrated in FIGS. 1A and 1C. The connection opening (OP) serves to connect the inside and the outside of the case (150) and may have a shape into which a cable can be inserted. The connection opening (OP) may be disposed to face the sensor (130) or not to face it.

[0111] The control unit can derive (or measure) the rotation angle of the shaft (110A, 110B) by converting the change in the magnetic field sensed by the sensor (130) into Arctan.

[0112] Figures 16a and 16b each show perspective views of a ring magnet (120B, 120C) according to another embodiment.

[0113] The encoders (100A to 100D) according to the embodiments are not limited to a specific number of poles of the ring magnet. That is, the encoders (100A to 100D) may include a bipolar magnetizing ring magnet (120A) as illustrated in FIG. 3, which is composed of a pair of N and S poles, but may also include a multipolar magnetizing ring magnet. That is, the encoders (100A to 100D) may include a four-pole magnetizing ring magnet (120B) illustrated in FIG. 16A instead of the bipolar magnetizing ring magnet (120A) illustrated in FIG. 3, or may include a ten-pole magnetizing ring magnet (120C) illustrated in FIG. 16B.

[0114] Figure 17 is a graph showing changes in the magnetic field sensed by the sensor (130), where the horizontal axis represents the rotation angle of the shaft and the vertical axis represents the magnetic field.

[0115] Figures 18a and 18b are graphs of the sensed magnetic field converted into Arctan.

[0116] In Fig. 18a, the horizontal axis represents the angle at which the ring magnet (120A) illustrated in Fig. 3 rotates, in Fig. 18b, the horizontal axis represents the angle at which the ring magnet (120B) illustrated in Fig. 16a rotates, and in each of Figs. 18a and 18b, the vertical axis represents the angle finally derived by the control unit.

[0117] For example, the control unit receives a change in the magnetic field sensed from the sensor (130) as illustrated in FIG. 17. Thereafter, the control unit can derive the angle at which the shaft (110A, 110B) rotates by combining vectors of two of the three signals (Bx, By, Bz) illustrated in FIG. 17 and performing an Arctan transformation as illustrated in FIG. 18a. If the encoders (100A to 100D) include a four-pole magnetized ring magnet (120B) instead of a bipolar magnetized ring magnet (120A), the angle illustrated in FIG. 18b can be derived when the ring magnet (120B) rotates. In the case of FIG. 18b, only the result of performing an Arctan transformation by combining vectors of two signals (By, Bz) is illustrated.

[0118] When the ring magnet (120A) is a bipolar magnet, two inflection points occur as shown in Fig. 18a, whereas when the number of poles of the ring magnet (120B) is four, four inflection points occur as shown in Fig. 18b. In this way, the number of poles of the ring magnet and the number of inflection points are the same.

[0119] Fig. 19 is a graph that actually simulates the performance of an encoder according to an embodiment, in which the horizontal axis represents time and the vertical axis represents the rotation angle of the shaft (110A, 110B).

[0120] For example, in Fig. 18, Arctan(Z / Y) and Arctan(Y / X) have linearity, while Arctan(X / Z) has nonlinearity. Therefore, the control unit can select Arctan(Y / X), which is the result with the most linearity among the Arctan transformed results shown in Fig. 18a, and output it as the result shown in Fig. 12. This is because the greater the strength of the magnetic field and the higher the linearity of the magnetic field, the higher the resolution sensing is possible.

[0121] Hereinafter, encoders according to comparative examples and embodiments are compared and explained as follows.

[0122] The magnetic encoder according to the first comparative example combines two or more vectors of sensors to track the absolute rotation angle of the shaft. At this time, the encoder according to the first comparative example may include a single three-dimensional sensor or an array of one-dimensional / two-dimensional sensors.

[0123] The encoder according to the second comparative example adopts a method of continuously recognizing a specific magnetic force emanating from the edge by utilizing the rising edge and the falling edge. An example of this second comparative example is disclosed in U.S. Patent No. US5539293.

[0124] The magnetic encoder according to the third comparative example mainly used a form that utilizes the change in magnetic field between the poles by multi-pole magnetization. An example of this third comparative example is disclosed in Korean registered patent KR1325905.

[0125] In the case of the encoder according to the comparative example described above, a specific arrangement structure is required to sense the magnetic field, so there are design restrictions.

[0126] In addition, in the case of the encoder according to the third comparative example, it depends on the performance of the equipment, and the radius increases as the number of poles increases. In the case of an encoder using multi-pole magnetization like this, a magnet with at least 8 pole pairs is required to track the absolute rotation angle of the shaft. In order to manufacture 8 pole pairs, i.e. 16 poles, as a ring magnet, there is a problem that a ring magnet with a minimum diameter of 30 mm or more is required. In this way, in the case of the third comparative example, since a multi-pole magnetization magnet is necessarily required, the size of the encoder may increase.

[0127] Additionally, the encoder according to the fourth comparative example utilizes gear teeth. In this case, there is a problem of increased size, as the number of gear teeth and the corresponding increase in gear tooth size are required to increase resolution.

[0128] On the other hand, according to the embodiment, the sensor (130) is not arranged on the rotation axis of the shaft (110A, 110B) on which the ring magnets (120A, 120B, 120C) are arranged. Therefore, since the sensor (130) and the ring magnets (120A, 120B, 120C) are arranged on different axes, the degree of freedom in the arrangement of parts can be increased.

[0129] In addition, according to the embodiment, although a multi-pole magnet (e.g., 120B or 120C) can be used, a bi-pole magnet (120A) can be used, so that the encoder can be implemented in a smaller size than the third comparative example.

[0130] In addition, since the embodiment does not use gears, the encoder can be implemented in a smaller size than the fourth comparative example.

[0131] Meanwhile, according to the embodiment, the investment rate of each of the shafts (110A, 110B) and the guide ring (170) is close to 1.

[0132] Figure 20 is a diagram explaining the change in investment rate and magnetic field lines.

[0133] In general, as illustrated in Fig. 20, when a ferromagnetic material (iron) (330) having a material such as steel with a high permeability exists around the core (320), the magnetic field has a property of moving toward the object (330) with a high permeability.

[0134] FIG. 21a is a drawing explaining the change in the magnetic field lines when the shaft (110) is implemented with steel or the like having a high permeability, and FIG. 21b is a drawing explaining the change in the magnetic field lines when the shaft (110) has a permeability close to 1. Here, the shaft (110), the ring magnet (120), and the substrate (140) perform the same roles as the shafts (110A, 110B), the ring magnets (120A, 120B, 120C), and the substrates (140A, 140B) described above, respectively, and therefore, redundant descriptions are omitted. In the case of FIG. 21a and FIG. 21b, the change in the magnetic field lines depending on whether the permeability of the shaft (110) is high or low is explained, but this description also applies to whether the permeability of the guide ring (170) is high or low.

[0135] When the investment rate of the shaft (110) is high, as illustrated in FIG. 21a, the magnetic field may flow into the interior of the shaft (110) and move (400) before the sensor (130) senses the magnetic field. Therefore, the sensor (130) cannot properly collect the magnetic field, and thus cannot accurately sense the rotation angle of the shaft (110).

[0136] On the other hand, in the case of the encoder according to the embodiment, a shaft (110) having an investment rate close to 1 is used. Therefore, as shown in FIG. 21b, the magnetic field does not flow into the interior of the shaft (110) and move, so the magnetic field can be collected by the sensor (130) to accurately derive the rotation angle of the shaft (110).

[0137] In general, encoders can only track the relative rotation angle of the shaft relative to a reference point, i.e., the relative rotation angle of the shaft, and cannot track the absolute rotation angle. Therefore, when the encoder's driving power is turned off and then turned back on, the shaft's rotation angle must be tracked again relative to the reference point. This is because, unlike in FIG. 17, when the ring magnet does not move vertically along the z-axis, which is the shaft's rotational axis, when the shaft rotates, the amplitudes of the three signals (Bx, By, Bz) are sensed to be identical.

[0138] On the other hand, according to an embodiment, when the shaft (110A, 110B) rotates, the ring magnet (120A, 120B, 120C) moves in the direction of the rotation axis of the shaft (110A, 110B) along the rotation axis of the shaft (110A, 110B). In this case, as illustrated in FIG. 17, the amplitudes of the three sensed signals (Bx, By, Bz) can be obtained differently. Therefore, according to an embodiment, the absolute rotation angle of the shaft (110A, 110B) can be obtained by deriving a combination of the rotation degree of the ring magnet (120A, 120B, 120C) and the distance moved in the z-axis direction from the vector and scalar changes of the magnetic field sensed by the sensor (130). Therefore, when the driving power of the encoder (100A to 100D) is turned off and then the driving power is supplied to the encoder (100A to 100D) again, there is no need to re-track the rotation angle of the shaft with respect to the reference point.

[0139] Although the above has been described with reference to embodiments, these are merely examples and do not limit the present invention. Those skilled in the art to which the present invention pertains will appreciate that various modifications and applications not exemplified above are possible without departing from the essential characteristics of the present embodiment. For example, each component specifically shown in the embodiments can be modified and implemented. In addition, differences related to such modifications and applications should be interpreted as being included within the scope of the present invention defined in the appended claims.

[0140] The mode for carrying out the invention has been sufficiently described in the above-mentioned “Best mode for carrying out the invention.”

[0141] The rotary magnetic encoder according to the embodiment can be used in sophisticated and complex devices requiring motion control operations, such as anti-lock brake systems (ABS) in automobiles, industrial automation, medical equipment, and robots.

Claims

1. A shaft that rotates, has a first screw thread formed therein and a first end, and a second screw thread formed therein and a second end opposite the first end; A ring magnet coupled to the shaft so as to rotate with the shaft and move vertically in the axial direction of the shaft; A case including a first female screw that is male-female coupled with the first screw line and a second female screw that is male-female coupled with the second screw line; A substrate including an outer surface coupled to the case and a through hole into which the shaft is inserted; and A rotary magnetic encoder comprising a sensor disposed on the substrate and sensing a magnetic field that changes according to the rotation of the shaft.

2. In paragraph 1, The above shaft A first intermediate portion positioned between the first end and the second end and to which the ring magnet is coupled; A rotary magnetic encoder comprising a second intermediate portion positioned between the first intermediate portion and the second end portion and inserted into the through hole.

3. In paragraph 2, The above case is A top plate having the first female screw formed thereon; The lower plate on which the second female screw is formed; and A rotary magnetic encoder comprising a body coupled with the upper plate and the lower plate, the body defining a receiving hole for receiving the first and second intermediate portions of the shaft, the ring magnet, the substrate and the sensor.

4. In paragraph 1, The above through hole of the above substrate is a rotary magnetic encoder located at the center of the above substrate.

5. In paragraph 1, The above through hole of the above substrate is a rotary magnetic encoder arranged to be offset to one side from the center of the above substrate.

6. A rotary magnetic encoder in the first paragraph, wherein the inner diameter of the through hole and the outer diameter of the shaft are the same.

7. A rotary magnetic encoder in the first paragraph, wherein the inner diameter of the through hole is larger than the outer diameter of the shaft.

8. In paragraph 2, A rotary magnetic encoder having an outer surface of the second intermediate portion including a third screw thread.

9. In paragraph 2 or paragraph 8, A rotary magnetic encoder further comprising a bearing arranged between the inner surface of the through hole and the outer surface of the second intermediate portion.

10. In paragraph 9, A rotary magnetic encoder having an inner surface of the above bearing including a third female screw thread that is male-female coupled with the third screw thread.

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