Motor for an electric spindle

Abstract

The application discloses a motor for an electric spindle, and relates to the field of electric spindles, comprising a stator and a permanent magnet rotor, a plurality of sensing members with electromagnetic induction capacity are fixed on the circumferential side surface outer ring of the permanent magnet rotor, each sensing member has an air gap with the circumferential side surface of the permanent magnet rotor, respectively, when the air gap spacing changes, the sensing member senses the magnetic flux change of the magnetic circuit and generates induced voltage. The application can realize real-time online detection of the rotation accuracy of the electric spindle, thereby improving the product quality stability and precision consistency of the spindle machining, and has the advantages of compact structure and small space occupation.

Description

Technical Field

[0001] The invention relates to the field of electric spindles, in particular to a motor for an electric spindle. Background Art

[0002] The electric spindle is one of the core components of high-end CNC equipment. It integrates the mechanical spindle of the machine tool and the spindle motor, giving the electric spindle advantages such as high speed and high precision. As the core performance indicator of the electric spindle, rotational accuracy directly affects many working capacity indicators such as the spindle's processing accuracy, lifespan, and processing energy consumption. Therefore, testing this indicator is one of the important tasks in evaluating and using the electric spindle. However, most domestic electric spindle manufacturers currently rely on test rods and mechanical meters to detect rotational accuracy, and are unable to evaluate the rotational accuracy of the electric spindle in actual load-bearing processing. The test results fail to evaluate the actual working accuracy, so that some low-rigidity electric spindles can be used as substitutes, which damages long-term interests.

[0003] Patent number CN108637793A discloses a rotary table indexing accuracy detection device and its detection and compensation method. This patent utilizes a magnetic scale and multiple reading heads to detect block breakpoints and process the interplay between these multiple reading heads, achieving high-precision indexing and identification of rotation center position changes. This solution can be used on equipment platforms or machine tool auxiliary equipment with unconstrained space to detect spindle rotation accuracy. However, it requires a large space, making it unsuitable for use within compact electric spindles. Furthermore, the high cost of the magnetic scale and multiple side heads makes this solution unsuitable for use with conventional CNC machining equipment. Finally, this type of detection requires the installation of auxiliary measuring tools such as gauge rods on the spindle, making online detection impossible. Therefore, this solution can be used on equipment platforms or auxiliary equipment, but not on electric spindles, let alone within them.

[0004] Patent number CN108637793A discloses a rotary table indexing accuracy detection device and its detection and compensation method. This patent utilizes a magnetic scale and multiple reading heads to detect block breakpoints and process the interplay between the multiple reading heads, achieving high-precision indexing and identification of rotation center position changes. This solution can be used on equipment platforms or machine tool auxiliary equipment where space is not restricted, and can achieve spindle rotation accuracy detection. However, it requires a large space, making it unsuitable for use within compact electric spindles. Furthermore, the magnetic scale and multiple side head solutions are extremely expensive, making them unsuitable for use with conventional CNC machining equipment. Finally, this type of detection requires the installation of auxiliary measuring tools such as gauge rods on the spindle, making online detection impossible. Therefore, this solution can be used on equipment platforms or auxiliary equipment, but not on electric spindles, let alone within them.

[0005] Therefore, the existing rotation detection device and method cannot meet the requirements of real-time online detection of the rotation accuracy of the electric spindle, and cannot meet the space, cost and other requirements of the electric spindle due to the large space occupied. Summary of the Invention

[0006] The present invention provides a motor for an electric spindle, so as to solve the problem that the rotation detection system in the prior art cannot realize real-time online detection of the rotation accuracy of the electric spindle.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A motor for an electric spindle includes a stator and a permanent magnet rotor for connecting to the spindle. A plurality of sensing elements with electromagnetic induction capability are fixedly provided on the circumferential side surface of the permanent magnet rotor. Each sensing element surrounds the permanent magnet rotor. An air gap is respectively provided between each sensing element and the circumferential side surface of the permanent magnet rotor. Each sensing element and the corresponding air gap are located on the magnetic circuit of the permanent magnet rotor. When the air gap spacing changes, the sensing element senses the change in magnetic flux in the magnetic circuit and generates an induced voltage.

[0009] Furthermore, the sensing elements are located in the same annular direction outside the circumferential side surface of the permanent magnet rotor and are distributed at equal intervals.

[0010] Furthermore, the air gap distances between each sensing element and the permanent magnet rotor are the same.

[0011] Furthermore, it also includes a signal acquisition and processing unit, and each sensing element is electrically connected to the signal acquisition and processing unit, and the signal acquisition and processing unit acquires and processes the induced voltage generated by each sensing element.

[0012] Furthermore, the signal acquisition and processing unit includes several voltage comparators and processors, the sensing elements are connected one-to-one with the signal input ends of the voltage comparators, the reference voltage ends of the respective voltage comparators are connected to the reference voltage, and the output ends of the respective voltage comparators are electrically connected with the input ends of the processors.

[0013] Furthermore, the sensing element is a coil winding.

[0014] Furthermore, it also includes a ring-shaped detection iron core, which is fixedly sleeved around the permanent magnet rotor, and the coil winding serving as the sensing element is installed on the detection iron core.

[0015] Furthermore, the detection core has a plurality of protrusions, each of which surrounds the permanent magnet rotor, and the coil windings are wound around the protrusions in a one-to-one correspondence.

[0016] Furthermore, each protrusion is a tooth portion provided on the detection core, and the teeth portions are distributed at equal intervals in the upward direction of the detection core ring, and the coil windings are wound around the teeth portions in a one-to-one correspondence.

[0017] Furthermore, the teeth are respectively located on the inner side surface of the detection core and extend in a direction perpendicular to the axial direction of the detection core.

[0018] Furthermore, the detection core is formed by stacking a plurality of core sheets, the inner side surface of each core sheet has a plurality of teeth extending in a direction perpendicular to the axial direction of the detection core, and each tooth portion is formed by stacking a plurality of teeth corresponding to the circumferential position.

[0019] Furthermore, it is assumed that the detection core has N teeth, each core has M teeth, N>M, M≥2, and the interval between adjacent teeth in the M teeth of each core is The teeth of adjacent layers of iron core pieces are displaced in the circumferential direction. Each tooth portion is formed by stacking M layers of tooth plates without any gaps and then NM layers of gaps.

[0020] Furthermore, each tooth portion includes a plurality of tooth extensions distributed side by side, each tooth extension is wound with a coil winding, and the coil windings on the plurality of tooth extensions of the same tooth portion are connected in series.

[0021] Furthermore, the spacing between adjacent tooth extensions in each tooth portion is the same.

[0022] The present invention relates to a motor for an electric spindle, wherein a permanent magnet rotor is coaxially connected to the spindle. The motor is equipped with multiple sensing elements with electromagnetic induction capabilities. Each sensing element surrounds the permanent magnet rotor, with an air gap between each sensing element and the permanent magnet rotor. The magnetic circuit of the permanent magnet rotor passes through the sensing elements and the air gap. When the spindle's rotation center shifts during rotation, the rotation center of the permanent magnet rotor also shifts, causing the air gap spacing to change and the magnetic resistance corresponding to the air gap to change. The sensing elements can sense the change in magnetic flux and generate an induced voltage. Whether the spindle's rotation center shifts can be determined by determining whether the sensing element generates an induced voltage. The direction of the spindle's rotation center shift can be determined based on the orientation of the sensing element generating the different induced voltages. The magnitude of the induced voltage can also be used to determine the amount of spindle rotation center shift. Therefore, the present invention can achieve real-time online detection of the spindle's rotation accuracy. Testing only requires extracting the induced voltage generated by the sensing element, without requiring other auxiliary detection tools or shutting down the spindle.

[0023] In this invention, the sensors are evenly spaced around the ring, facilitating rapid determination of the spindle's rotational center offset. A voltage comparator and processor form the sensor's signal acquisition and processing unit, comparing the output voltage of each sensor with a reference voltage to determine spindle center offset. This approach offers the advantages of simple structure and rapid detection.

[0024] In the present invention, a detection iron core is arranged in an annular ring around the permanent magnet rotor, and a coil winding is used as a sensing element. The coil winding is installed on the detection iron core. By utilizing the characteristic of low magnetic resistance of the iron core, the magnetic field strength passing through the coil winding is increased through the detection iron core, thereby improving the sensitivity of the coil winding as a sensing element.

[0025] The detection core of the present invention is formed by stacking multiple iron sheets, thereby reducing eddy current losses when the coil winding generates induced voltage, facilitating the acquisition and processing of the induced voltage by the signal acquisition and processing unit. The inner surface of the detection core is designed with teeth for mounting the coil winding, which minimizes the air gap between the coil winding (the sensor) and the permanent magnet rotor, resulting in a more compact structure.

[0026] Because the permanent magnet rotor is longer axially than the detection core, the end effect between the permanent magnet rotor and the detection core can cause differences in the axial magnetic field. To address this issue, the present invention utilizes a stack of teeth on the inner side of the core sheet, forming the teeth for mounting the coil windings. These teeth are stacked in a pattern where several layers are stacked before leaving several empty spaces. This ensures that the end effect affects all teeth equally, balancing the effect on the magnetic flux.

[0027] In the present invention, each tooth portion of the detection core is composed of several tooth extensions, each tooth extension is respectively installed with a coil winding, and the coil windings of the same tooth portion are connected in series, thereby increasing the back electromotive force (back electromotive force difference) of the turn chain, thereby improving the detection sensitivity.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. By adding a sensor to the electric spindle motor, the displacement signal of the spindle's rotation center eccentricity is converted into an electrical signal, enabling real-time online detection of the spindle's rotation accuracy. After signal processing, changes in the spindle's accuracy can be detected in real time, thereby improving the quality stability and precision consistency of spindle-processed products and increasing the added value of processing.

[0030] 2. By adding a sensor to the electric spindle motor, online monitoring of rotational accuracy is possible without increasing the spindle's power or size, taking up minimal space. By using changes in rotational accuracy as a guide, the spindle's lifespan can be monitored, assessed, and replaced or repaired in advance, reducing replacement or repair time. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is an exploded view of the structure of an embodiment of the present invention.

[0032] Figure 2 It is a cross-sectional view of the structure of an embodiment of the present invention.

[0033] Figure 3 It is a cross-sectional view of the partial assembly structure of the permanent magnet rotor, motor end cover, and detection component in an embodiment of the present invention.

[0034] Figure 4 It is a schematic diagram of the partial assembly structure of the permanent magnet rotor, motor end cover, and detection component in an embodiment of the present invention.

[0035] Figure 5 It is a cross-sectional view of the partial assembly structure of the motor end cover and the detection component in an embodiment of the present invention.

[0036] Figure 6 It is a schematic diagram of the partial assembly structure of the motor end cover and the detection component in an embodiment of the present invention.

[0037] Figure 7 Schematic diagram of the detection core structure in an embodiment of the present invention.

[0038] Figure 8 1 is a schematic diagram showing the principle of stacking the tooth plates to form the tooth portion in an embodiment of the present invention.

[0039] Figure 9 It is a schematic diagram of the signal acquisition and processing unit in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be further described below with reference to the accompanying drawings and examples.

[0041] like Figures 1-6As shown, this embodiment discloses a motor for an electric spindle. Existing electric spindle motors include a stator and a permanent magnet rotor. The stator includes a cylindrical stator core 1, with a power winding 2 wound around the inner wall of the stator core 1. A cylindrical power winding potting body 3 is provided inside the stator core 1, and the power winding 2 is sealed to the inner wall of the stator core 1 through the power winding potting body 3. The permanent magnet rotor includes a rotor sleeve 4, a rotor permanent magnet 5 coaxially sleeved on the circumferential outer wall of the rotor sleeve 4, a rotor sleeve 6 coaxially sleeved on the circumferential outer wall of the rotor permanent magnet 5, and a rotor end ring 7 coaxially sleeved on the circumferential outer wall of one end of the rotor sleeve 4 and pressed against the corresponding end of the rotor permanent magnet 5. The permanent magnet rotor is integrally mounted coaxially within the stator, with one end of the permanent magnet rotor protruding from the corresponding end of the stator. A motor end cap 8 made of a non-magnetic metal material is coaxially fixedly mounted on the end of the stator to protect the motor power winding. One end of the permanent magnet rotor that passes through the stator continues to pass through the motor end cover 8 to form a passing section. The passing section of the permanent magnet rotor is used to coaxially connect to the main shaft. When the power winding of the stator is energized, the permanent magnet rotor rotates and drives the main shaft to rotate.

[0042] In this embodiment, a detection assembly is added to the electric spindle motor. The detection assembly includes multiple sensing elements with electromagnetic induction capabilities. The multiple sensing elements surround the permanent magnet rotor. Each sensing element has an air gap with the circumferential side of the permanent magnet rotor, and the air gap spacing between each sensing element and the permanent magnet rotor is the same. As a result, the closed magnetic circuit of the permanent magnet rotor passes through each sensing element and the air gap corresponding to the sensing element, where the air gap forms a magnetic resistance. When the rotation center shifts during the spindle rotation, the rotation center of the permanent magnet rotor also shifts accordingly. The air gap spacing between the sensing element and the permanent magnet rotor changes at least in the direction of the shift and the direction opposite to the shift direction, and the magnetic resistance of the air gap changes. The sensing element senses the changing magnetic flux and generates an induced voltage. Based on the induced voltage, it is possible to determine whether the rotation center is shifted, the direction of the shift, and the amount of the shift.

[0043] In this embodiment, the installation position of the sensor in the electric spindle motor can be selected at a reasonable position according to design requirements. In one case, the sensor can be directly fixed to the end face of the motor end cover 8, in which case each sensor surrounds the permanent magnet rotor protrusion section; in another case, a number of installation grooves can be provided on the inner side of the motor end cover 8 for installing the sensor, in which case each sensor surrounds the corresponding position of the permanent magnet rotor inside the motor end cover 8. Therefore, the installation position of the sensor in this embodiment can be selected according to needs, as long as the selected installation position allows each sensor to surround the permanent magnet rotor, it is a reasonable installation position. This embodiment further illustrates the invention by taking the installation of the sensor on the end face of the motor end cover 8 as an example.

[0044] In this embodiment, each sensor is fixed to the end face of the motor end cover 8, so that each sensor surrounds the permanent magnet rotor protrusion section, and each sensor is evenly spaced in the annular direction. The evenly spaced distribution is conducive to quickly judging the offset direction of the main shaft rotation center.

[0045] In this embodiment, the sensor element uses the principle of electromagnetic induction to detect changes in magnetic flux caused by the offset of the permanent magnet rotor's rotation center. Therefore, the sensor element can be a conductor. This conductor can be any shape, such as a straight conductor or a curved conductor, or it can be a coil winding with multiple turns. Because coil windings have a high sensitivity in sensing changes in magnetic flux, coil winding 9 is used as the sensor element in this embodiment.

[0046] like Figure 7 As shown, in order to further improve the sensitivity of the coil winding 9 in sensing changes in magnetic flux, this embodiment further adds a circular detection core 10 as a detection component to the motor end cover 8. The motor end cover 8 is specifically designed to be a hollow disc, wherein the hollow portion is for the permanent magnet rotor to pass through. The detection core 10 is fixed to the circular annular protrusion on the upper circular annular protrusion of the motor end cover 8, thereby making the detection core 10 looped around the permanent magnet rotor passing through the section. The detection core 10 is also located in the closed magnetic circuit of the permanent magnet rotor. Each coil winding 9 is mounted on the detection core 10, and a potting body 11 is pressed into the space surrounded by the circular annular protrusion. The potting body 11 is formed by injection molding, and the detection core 10 and each coil winding 9 are fastened to the end face of the motor end cover 8 by the potting body 11, and the detection core 10 and the coil winding 9 are protected by the potting body 11. Thus, the motor end cover 8 not only protects the internal components of the motor, but also connects and mounts the detection assembly, isolating the motor power winding from the detection assembly. Because each coil winding 9 is mounted on the detection core 10, the detection core 10 can improve the sensitivity of the coil winding 9 in sensing changes in magnetic flux.

[0047] In this embodiment, each coil winding 9 can be directly mounted on different portions of the detection core 10. Alternatively, the detection core 10 may be formed with a plurality of protrusions extending around the section extending from the permanent magnet rotor, with each coil winding 9 being wound one-to-one around each protrusion. This embodiment further illustrates the invention using the detection core 10 having protrusions as an example.

[0048] In this embodiment, a plurality of teeth 12 are formed on the inner side surface of the detection core 10 as protrusions, and each tooth 12 extends radially along the detection core 10. The teeth 12 are evenly distributed at equal intervals along the circumferential direction of the detection core 10, and there is a gap between the end face of each tooth and the circumferential side of the permanent magnet rotor protrusion section, and the gap spacing is the same. The coil windings 9 are wound around the teeth 12 in a one-to-one correspondence, and there is an air gap between each coil winding 9 and the permanent magnet rotor protrusion section, and the air gap spacing is the same. The radially extending teeth 12 enable a smaller air gap to be formed between the coil winding 9 and the permanent magnet rotor protrusion section, thereby making the entire detection component and the motor structure more compact.

[0049] In this embodiment, to reduce eddy current losses when the coil winding 9 generates induced voltage, the detection core 10 is designed to be formed by stacking multiple core sheets. Each core sheet is a hollow, annular sheet made of electrical silicon steel, which has a magnetic permeability much greater than that of air, and its magnetic resistivity is roughly equal in all directions. The inner side of each core sheet has a plurality of teeth extending perpendicular to the axial direction of the detection core. When the core sheets are stacked, each tooth portion 12 is formed by stacking a plurality of corresponding teeth in the circumferential direction. By using a stacked structure of core sheets to form the detection core 10, excessive losses in the sensing voltage induced by the coil winding 9 can be avoided.

[0050] In this embodiment, in order to avoid the difference in axial magnetic field caused by the edge effect of the permanent magnet rotor and the detection core 10, the teeth used to form each tooth portion 12 are stacked in a manner that a plurality of layers of teeth are stacked and a plurality of layers are left empty. This can make the edge effect have the same effect on each tooth portion 12 and balance the effect of the edge effect on the magnetic flux. In order to form the stacking combination of the teeth in the tooth portion 12, for a detection core with N teeth, each core sheet has M teeth, M ≥ 2, N > M, then the interval between adjacent teeth in the M teeth of each core sheet is set to The teeth of adjacent layers of iron core pieces are displaced in the circumferential direction. Each tooth portion 12 is formed by stacking M layers of tooth plates without any gaps and then NM layers of tooth plates with gaps.

[0051] like Figure 8As shown, for example, when the number of teeth in each iron core sheet is M=2, and it is required to form a detection iron core 10 with N=3 teeth and the teeth are evenly spaced, the adjacent teeth are spaced 120 degrees apart, and the three teeth of the detection iron core 10 are positioned at A1, A3, and A3 in a counterclockwise direction. At this time, the two teeth in each iron core sheet are spaced 120 degrees apart. In terms of layers, the two teeth of the first layer (i.e., the bottom layer) of the iron core sheet X1 are positioned at A1 and A2 respectively; the two teeth of the second layer of the iron core sheet X2 are offset 120 degrees in the circumferential direction compared to the two teeth of the first layer of the iron core sheet X1, that is, the two teeth of the second layer of the iron core sheet X2 are positioned at A2 and A3 respectively; the two teeth of the third layer of the iron core sheet X3 are offset 120 degrees in the circumferential direction compared to the two teeth of the second layer of the iron core sheet X2, that is, the two teeth of the third layer of the iron core sheet X3 are offset 120 degrees in the circumferential direction compared to the two teeth of the second layer of the iron core sheet X2, that is, the two teeth of the third layer of the iron core sheet X3 are positioned at A3 and A1 respectively; the two teeth of the fourth layer of the iron core sheet X4 are offset 120 degrees in the circumferential direction compared to the two teeth of the second layer of the iron core sheet X1. The two teeth of the third-layer lamination X3 are offset by another 120 degrees in the circumferential direction, meaning the two teeth of the fourth-layer lamination X4 are positioned at A1 and A2, respectively. The two teeth of the fifth-layer lamination X5 are offset by another 120 degrees in the circumferential direction, meaning the two teeth of the fifth-layer lamination X5 are positioned at A2 and A3, respectively. The two teeth of the sixth-layer lamination X6 are offset by another 120 degrees in the circumferential direction, meaning the two teeth of the sixth-layer lamination X6 are positioned at A3 and A1, respectively. The offsets for the teeth of the subsequent laminations are similar.

[0052] When the first lamination X1 is stacked with the second lamination X2, the teeth at position A2 of the first lamination X1 and the second lamination X2 are stacked without any gaps. When the third lamination X3 is stacked with the second lamination X2, the teeth at position A3 of the second lamination X2 and the third lamination X3 are stacked without any gaps, while the teeth at position A1 of the third lamination X3 and the first lamination X1 are stacked without any gaps (i.e., the second lamination X2 is left empty). When the fourth layer of iron core sheet X4 is stacked on the third layer of iron core sheet X3, there is an empty layer between the tooth piece at position A2 of the fourth layer of iron core sheet X4 and the tooth piece at position A2 of the first layer of iron core sheet X1 and the second layer of iron core sheet X2 (i.e., the third layer of iron core sheet X3 is empty), and the tooth piece at position A1 of the fourth layer of iron core sheet X4 and the tooth piece at position A1 of the third layer of iron core sheet X3 are stacked without empty layers, and there is an empty layer between the tooth piece at position A1 of the third and fourth layers without empty layers and the tooth piece at position A1 of the first layer of iron core sheet X1 (i.e., the second layer of iron core sheet X2 is empty). When the fifth layer of iron core sheet X5 is stacked on the fourth layer of iron core sheet X4, the tooth piece at position A2 of the fifth layer of iron core sheet X5 and the tooth piece at position A2 of the fourth layer of iron core sheet A4 are stacked without empty layers, and the tooth piece at position A2 of the fourth and fifth layers of positions A2 stacked without empty layers and the tooth piece at position A2 of the first and second layers of positions A2 stacked without empty layers are empty one layer (i.e. the third layer of iron core sheet X3 is empty), and the tooth piece at position A3 of the fifth layer of iron core sheet X5 and the tooth piece at position A3 of the second layer of iron core sheet X2 and the tooth piece at position A3 of the third layer of iron core sheet X3 stacked without empty layers are empty one layer (i.e. the fourth layer of iron core sheet X4 is empty). When the sixth lamination X6 is stacked on the fifth lamination X5, a gap exists between the tooth at position A1 of the sixth lamination X6 and the third lamination X3 and the tooth at position A1 of the fourth lamination X4 (i.e., the fifth lamination X5 is empty). The tooth at position A3 of the sixth lamination X6 is stacked with the tooth at position A3 of the fifth lamination X5 without any gaps. Similarly, in the three tooth sections at positions A1, A3, and A3 of the final inspection core 10, each tooth section 12 is formed by stacking two teeth at the corresponding position, followed by one gap.

[0053] Similarly, for the case where M≥2, N>M, no matter what the values ​​of N and M are, the interval between adjacent teeth in the M teeth of each iron core is set to The teeth of adjacent layers of iron core pieces are displaced in the circumferential direction. The corresponding tooth portion 12 can be formed by stacking M layers of tooth plates without any gaps and then NM layers of tooth plates without any gaps.

[0054] Each tooth section 12 is composed of multiple tooth extensions 13 arranged side by side. In this embodiment, each tooth section 12 is composed of three tooth extensions 13, with adjacent tooth extensions 13 spaced uniformly apart. Each tooth extension 13 is wound with a coil winding 9, and the coil windings 9 on multiple tooth extensions of the same tooth section 12 are connected in series. By connecting multiple coil windings on the same tooth section in series, the back electromotive force (back electromotive force difference) of the turn chain on that tooth section is increased, thereby improving detection sensitivity.

[0055] In this embodiment, the detection component also includes a signal acquisition and processing unit, such as Figure 9 As shown, the signal acquisition and processing unit includes several voltage comparators V and a processor U. One end of the series-connected coil winding structure L of each tooth is connected to the signal input terminal of the voltage comparator V in a one-to-one correspondence, and the other end of the series-connected coil winding structure L of each tooth is connected to a common ground. The reference voltage terminal of each voltage comparator V is connected to the signal output terminal of the processor U. The processor U provides the same reference voltage to each voltage comparator V. The signal output terminal of each voltage comparator V is connected to the signal input terminal of the processor. As a result, each voltage comparator V compares the induced voltage generated by the coil winding on the corresponding tooth 12 with the reference voltage and outputs the comparison result to the processor.

[0056] In this embodiment, the detection core 10, coil winding 9, and the air gap between the coil winding 9 and the permanent magnet rotor in the detection assembly are all located within the permanent magnet rotor's closed magnetic circuit. Because the detection core 10 and coil winding 9 are fixed, the air gap spacing and the corresponding magnetic resistance are fixed. The magnitude of the magnetic flux sensed by the coil winding 9 is primarily determined by the change in the air gap between the coil winding 9 and the permanent magnet rotor.

[0057] When the spindle center of the electric spindle motor is at the theoretical rotation center, that is, when the rotation error is zero, the air gap between the motor's permanent magnet rotor and the coil winding 9 remains unchanged, and the magnetic flux in the magnetic circuit of the coil winding 9 remains unchanged. At this time, the coil winding 9 does not generate an induced voltage. When the spindle's rotation center shifts, and the motor's permanent magnet rotor's rotation center also shifts, the air gap between the permanent magnet rotor and the coil winding 9 in at least the direction of the shift and the direction opposite to the shift changes. This causes uneven magnetic resistance in the magnetic circuit of the coil winding 9 corresponding to the shifted air gap, and consequently, changes in the magnetic flux in the magnetic circuit of the coil winding 9 corresponding to the shifted air gap. At this time, the coil winding 9 corresponding to the shifted air gap generates an induced voltage. A voltage comparator collects and compares the induced voltage to obtain a voltage difference. Based on this voltage difference, whether the spindle's rotation center has shifted can be determined. Combined with the orientation of the coil winding 9 that generated the induced voltage, the direction of the spindle's rotation center shift can be determined.

[0058] Furthermore, in this embodiment, the relationship between spindle rotation error and voltage difference can be calibrated experimentally. During the experiment, the spindle is rotated with different rotation center offsets. The detection assembly of this embodiment measures a series of corresponding voltage differences, which are then calibrated to establish a corresponding relationship between the voltage differences and the offsets. During operation of this embodiment, once the voltage differences are obtained, the spindle rotation center offset can be determined based on the calibrated corresponding relationship.

[0059] In this embodiment, the detection assembly and permanent magnet rotor on the stator side of the electric spindle motor convert the displacement of the electric spindle's rotational accuracy into an electrical signal for the coil winding, thus enabling detection of the electric spindle's rotational error. Furthermore, there is no need to add measuring tools such as a check rod to the front end of the electric spindle, which would hinder actual machining, allowing for online inspection of rotational accuracy. This provides methodological support for testing and researching the lifespan and reliability of electric spindles.

[0060] The embodiments described in the present invention are merely descriptions of the preferred implementation methods of the present invention and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by those skilled in the art should fall within the scope of protection of the present invention. The technical contents for which protection is sought in the present invention have all been recorded in the claims.

Claims

1. A motor for an electric spindle, comprising a stator and a permanent magnet rotor for connecting to the spindle, characterized in that: A plurality of sensing elements with electromagnetic induction capability are fixedly provided on the circumferential side surface of the permanent magnet rotor. Each sensing element surrounds the permanent magnet rotor. An air gap is respectively formed between each sensing element and the circumferential side surface of the permanent magnet rotor. Each sensing element and the corresponding air gap are located on the magnetic circuit of the permanent magnet rotor. When the air gap spacing changes, the sensing element senses the change in magnetic flux in the magnetic circuit and generates an induced voltage. The sensing element is a coil winding; It also includes a ring-shaped detection iron core, which is fixedly sleeved around the permanent magnet rotor, and the coil winding serving as the sensing element is installed on the detection iron core; The detection core has a plurality of protrusions, each of which surrounds the permanent magnet rotor, and the coil windings are wound around the protrusions in a one-to-one correspondence; Each protrusion is a tooth portion provided on the detection core, and the teeth portions are distributed at equal intervals upwardly of the detection core ring, and the coil windings are wound around the teeth portion one by one; The teeth are respectively located on the inner side of the detection core and extend in a direction perpendicular to the axial direction of the detection core; The detection core is formed by stacking a plurality of core sheets. The inner side surface of each core sheet has a plurality of teeth extending in a direction perpendicular to the axial direction of the detection core. Each tooth portion is formed by stacking a plurality of teeth corresponding to the circumferential position. Assume that the detection core has N teeth, each core has M teeth, N>M, M≥2, and the interval between adjacent teeth in the M teeth of each core is The teeth of adjacent layers of iron core pieces are displaced in the circumferential direction. Each tooth portion is formed by stacking M layers of tooth plates without any gaps and then NM layers of gaps.

2. The motor for an electric spindle according to claim 1, characterized in that: The sensing elements are located in the same annular direction outside the circumferential side surface of the permanent magnet rotor and are distributed at equal intervals.

3. The motor for an electric spindle according to claim 1, characterized in that: The air gap distances between each sensing element and the permanent magnet rotor are the same.

4. The motor for an electric spindle according to claim 1, characterized in that: It also includes a signal acquisition and processing unit. Each sensing element is electrically connected to the signal acquisition and processing unit. The signal acquisition and processing unit acquires and processes the induced voltage generated by each sensing element.

5. The motor for an electric spindle according to claim 4, characterized in that: The signal acquisition and processing unit includes several voltage comparators and a processor. The sensing elements are connected to the signal input terminals of the voltage comparators in a one-to-one correspondence. The reference voltage terminals of the voltage comparators are connected to the reference voltage respectively. The output terminals of the voltage comparators are electrically connected to the input terminals of the processor respectively.

6. The motor for an electric spindle according to claim 1, characterized in that: Each tooth portion includes a plurality of tooth extensions distributed side by side, each tooth extension is wound with a coil winding, and the coil windings on the plurality of tooth extensions of the same tooth portion are connected in series.

7. The motor for an electric spindle according to claim 6, characterized in that: The spacing between adjacent tooth extensions in each tooth portion is the same.

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