CN112525227A

CN112525227A - Gear type encoder

Info

Publication number: CN112525227A
Application number: CN202011540585.8A
Authority: CN
Inventors: 刘俊亨; 杨尚; 郑伟光; 马春玲; 徐大圣; 车奔
Original assignee: CHANGCHUN YUHENG OPTICS CO LTD
Current assignee: CHANGCHUN YUHENG OPTICS CO LTD
Priority date: 2020-12-23
Filing date: 2020-12-23
Publication date: 2021-03-19

Abstract

The invention provides a gear encoder, comprising: a reading head and a gear, the reading head includes a first magnetic sensor corresponding to the Z area of the gear, and the inside of the first magnetic sensor respectively includes four groups arranged in two rows up and down. Magnetic induction element, every two magnetic induction elements form a half bridge, the modulus of the first magnetic sensor is 1.5 to 2.5 times the modulus of the gear, and the four groups of magnetic induction elements inside the first magnetic sensor are at a distance of P/2 They are arranged at equal intervals, so that the phases of the two magnetic induction elements that make up the half-bridge are 180° out of phase, and P is the tooth pitch of the gears. The invention can filter out background noise, improve the signal-to-noise ratio of the Z signal, and facilitate the extraction of useful signals.

Description

Gear type encoder

Technical Field

The invention relates to the technical field of encoders, in particular to a gear type encoder.

Background

The gear type encoder consists of a gear made of magnetic conductive materials and a reading head, wherein the reading head comprises a magnetic sensor and a magnetic block corresponding to the gear modulus. In order to obtain a space magnetic field with uniform intensity and uniform direction, a magnetic sensor needs to be installed at the surface center position of a magnetic block to the maximum extent, the magnetic sensor receives the magnetic field generated by the magnetic block, the center of the magnetic sensor is opposite to a position on the radial side of a gear, the magnetic field direction of the position of the magnetic sensor is changed when the gear rotates according to the reluctance effect, the magnetic sensor outputs regularly changed electric signals, the gear serves as a modulation disc of signals, the magnetic line of force of the space magnetic field of the magnetic block is changed when the gear rotates, the direction of the magnetic field received by the magnetic sensor is changed, the output signals are changed, and electric signals corresponding to the tooth tops and the tooth bottoms of the gears are generated.

The structure of the gear type encoder is shown in fig. 1, a gear is divided into an AB area and a Z area, the two magnetic sensors respectively correspond to the AB area and the Z area, the two magnetic sensors both output two paths of differential signals, the two paths of differential signals output by the magnetic sensors corresponding to the AB area are an a signal and a B signal respectively, and only one path of differential signal output by the magnetic sensors corresponding to the Z area is taken as a Z signal.

The internal structure of the magnetic sensor is shown in fig. 2, eight magnetic sensing elements R1-R8 are arranged in the magnetic sensor, R1-R8 are arranged in two rows, one upper magnetic sensing element and one lower magnetic sensing element, four magnetic sensing elements are arranged at equal intervals with the distance of P/4 of the tooth space, and the resistance values of R1-R8 change along with the change of an external magnetic field. Two longitudinal magnetic induction elements are in a group, namely R1 and R3, R2 and R4, R5 and R7, and R6 and R8 are at the same position and sense the same magnetic field. 3. The 4 pins are respectively connected with a power supply and a ground wire, 1, 2, 5 and 6 respectively output V1+, V2+, V1 and V2 signals, V1+ and V1-are differentiated to form one path of differential signal, and V2+ and V2-are differentiated to form the other path of differential signal.

R1-R4 and R5-R8 are respectively arranged in a Wheatstone bridge, as shown in FIG. 3, R1 and R3 sense the same magnetic field at the same position, R1 and R4 form a half bridge, when R1 increases Δ R, R4 decreases Δ R, and when R2 increases Δ R, R3 decreases Δ R. R5-R8 are obtained by the same method. Δ R satisfies a sinusoidal variation over a tooth period, then:

ΔR＝RKsinα；

V₊-V_-＝KsinαV_CC。

the Z signal is shown in fig. 4, and since there are too many clutter in the Z signal, the background noise is too large, the signal-to-noise ratio is low, and it is difficult to extract a useful signal. Therefore, there is a need for a gear-type encoder that can improve the signal-to-noise ratio of the Z signal.

Disclosure of Invention

In view of the above problems, it is an object of the present invention to provide a gear-type encoder that is more advantageous for extracting a useful signal by removing background noise of a Z-phase signal to improve a signal-to-noise ratio.

In order to achieve the purpose, the invention adopts the following specific technical scheme:

the invention provides a gear type encoder which comprises a reading head and a gear, wherein the reading head comprises a first magnetic sensor corresponding to a Z area of the gear, four groups of magnetic sensing elements which are arranged in two rows in an up-down alignment mode are arranged inside the first magnetic sensor, each two magnetic sensing elements form a half bridge, the modulus of the first magnetic sensor is 1.5-2.5 times of the modulus of the gear, the four groups of magnetic sensing elements inside the first magnetic sensor are arranged at equal intervals in a P/2 distance mode, the phase difference of the two magnetic sensing elements forming the half bridge is 180 degrees, and P is the tooth pitch of the gear.

Preferably, the reading head further comprises a second magnetic sensor corresponding to the AB region of the gear, the module of the second magnetic sensor being the same as the module of the gear.

Preferably, the central lines of the sensing areas of the first magnetic sensor and the second magnetic sensor respectively face the radial extension lines of the gear, and the first magnetic sensor is offset from the second magnetic sensor by a distance of m pi/4 in the horizontal direction, wherein m is the module of the gear.

Preferably, a line of the gear along the tooth width direction is used as a dividing line to divide the gear into two parts, one part is a full-tooth spur gear, and the other part is removed from a tooth crest to a tooth root on a straight tooth of the full-tooth spur gear to form a single-missing tooth.

Preferably, the distance from the second magnetic sensor to the boundary line is greater than or equal to 2.5mm, and the distance from the first magnetic sensor to the boundary line is greater than or equal to 2 mm.

Preferably, the side surfaces and the front surfaces of the first magnetic sensor and the second magnetic sensor are perpendicular to the mounting surface of the gear.

Preferably, the diameter of the top circle of the gear is more than or equal to 20 mm.

Preferably, the tooth top roughness of the gear is better than 1.6, the tooth flank roughness is better than 3.2, and the tooth root surface roughness is better than 3.2.

The invention can obtain the following technical effects:

1. in the process of machining the single-missing teeth, generally, after straight teeth are machined by hobbing, a part of teeth are milled to form the single-missing teeth. The processing cost of the single-missing tooth is lower than that of the currently generally adopted single-convex tooth and single-concave tooth gears, the processing is easier compared with the single-convex tooth gears, and the assembly cost can be saved compared with the single-concave tooth gears.

2. The modulus of the second magnetic sensor corresponding to the AB area is the same as that of the gear, the modulus of the first magnetic sensor corresponding to the Z area is 1.5-2.5 times of that of the gear, the tooth pitch of the first magnetic sensor is P when the first magnetic sensor meets a full-tooth part, a direct current signal is generated, and when the first magnetic sensor meets a single missing tooth part, the tooth pitch is 2P, a sine wave signal is generated, so that background noise is filtered, the signal to noise ratio is improved, and extraction of useful signals is facilitated.

3. The first magnetic sensor and the second magnetic sensor are shifted by a distance of m pi/4 in the horizontal direction, so that the equal amplitude point of the A, B signal and the maximum amplitude point of the Z signal can be superposed, and the phase relation between the A, B signal and the Z signal is met.

Drawings

Fig. 1 is a schematic structural view of a conventional gear-type encoder;

fig. 2 is a schematic structural view of a conventional magnetic sensor;

FIG. 3 is a schematic diagram of a conventional magnetic sensor in positional relationship with a gear;

FIG. 4 is a diagram of a conventional Z signal;

FIG. 5 is a schematic view of a conventional single lobe gear;

FIG. 6 is a schematic structural view of a conventional single-indented gear;

FIG. 7 is a front elevational view of a geared encoder according to one embodiment of the present invention;

FIG. 8 is a top plan view of a geared encoder according to one embodiment of the present invention;

FIG. 9 is a schematic view showing the internal arrangement of a geared encoder according to an embodiment of the present invention;

FIG. 10 is a schematic illustration of a first magnetic sensor in positional relationship to a gear according to one embodiment of the present invention;

FIG. 11 is a schematic diagram of the internal structural arrangement of a first magnetic sensor in accordance with one embodiment of the present invention;

FIG. 12 is a schematic diagram of a Z signal according to one embodiment of the invention;

FIG. 13 is a schematic diagram of the phase relationship of the A, B signal and the Z signal, according to one embodiment of the invention.

Wherein the reference numerals include: the reading head 1, the first magnetic sensor 11, the second magnetic sensor 12, the magnetic sensing elements R1-R8, the sensing area central line 13, the gear 2, the full-tooth spur gear 21, the single-missing tooth 22, the boundary line 23 and the radius extension line 24.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention.

The gear type encoder provided by the embodiment of the present invention will be described in detail below.

As shown in fig. 7 to 9, the gear-type encoder according to the embodiment of the present invention includes: the reading head 1 comprises a first magnetic sensor 11 and a second magnetic sensor 12, the first magnetic sensor 11 corresponds to the Z area and is used for generating a Z signal, and the second magnetic sensor 12 corresponds to the AB area and is used for generating an A signal and a B signal.

With a certain line in the tooth width direction of the gear 2 as a dividing line 23, the gear 2 is divided into a full-tooth part and a tooth-missing part, the full-tooth part is a full-tooth straight gear 21, that is, an AB region is the full-tooth straight gear 21, corresponding to the second magnetic sensor 12, the full-tooth in the AB region is demodulated with the second magnetic sensor 12 to obtain a signal a and a signal B, the tooth-missing part is fed from the tooth top to the tooth bottom on a straight tooth of the full-tooth straight gear 21 to form a single tooth-missing 22, that is, a Z region is the full-tooth straight gear 21 with the single tooth-missing 22, corresponding to the first sensor magnetic sensor 11, and the single tooth-missing 22 in the Z region is demodulated with the first magnetic sensor 11 to obtain a Z signal. The modulus of the full-tooth part and the missing-tooth part are the same and are both m.

When the gear 2 is machined, the full-tooth spur gear 21 is machined by hobbing, and then a part of teeth are milled from the tooth crest to the tooth root on one straight tooth, so that a single missing tooth 22 is formed.

Conventional gears typically employ single male and single female teeth in the Z-region, as shown in fig. 5 and 6, respectively. The structures of the single lobe and single concave lobe, respectively, are described below to clarify the reason that the present invention employs the single missing lobe 22 instead of the single lobe and single concave lobe.

1. Single convex tooth

The single convex tooth is a convex tooth which is the same as a tooth on the standard tooth in the AB area. The gear encoder has high requirements on the precision of the gear, so cast machining cannot be adopted. The standard gear is usually machined, redundant teeth are milled on the standard gear in a numerical control mode, and only one single-degree convex tooth is left.

2. Single concave tooth

The single concave tooth is a cylindrical surface with a single groove, the diameter of the cylindrical surface is equal to the diameter of an addendum circle, and the groove corresponds to a certain tooth valley on the standard gear in the AB area. Gears with single concave teeth are usually assemblies consisting of more than two parts assembled. Such gear processing costs are high, and the cost of the gear encoder also increases.

Based on the problem of high processing cost of single convex teeth and single concave teeth, the invention develops a new method, after the full-tooth straight gear is processed by hobbing, a part of teeth are milled on one straight tooth of the full-tooth straight gear to form single missing teeth 22. Compared with a single convex tooth, only half of the tooth needs to be milled, so that the processing is easier, and the processing cost is lower. Compared with the single concave tooth, the whole body is a part, so that the assembly cost can be reduced. Therefore, the single missing tooth 22 adopted in the present invention can reduce the cost of the gear encoder.

In one example of the present invention, the addendum circle diameter of the gear 2 is equal to or greater than 20mm, the distance from the second magnetic sensor 12 to the boundary of the gear 2 is equal to or greater than 2.5mm, and the distance from the first magnetic sensor 11 to the boundary of the gear 2 is equal to or greater than 2 mm.

If the distance from the second magnetic sensor 12 to the boundary of the gear 2 is less than 2.5mm, the single missing tooth 22 affects the A, B signal and deteriorates the signal quality, and if the distance from the first magnetic sensor 11 to the boundary of the gear 2 is less than 2mm, the full tooth affects the Z signal and lowers the signal amplitude.

In one specific example of the present invention, the side surface (L surface in fig. 9) of the first magnetic sensor 11 and the side surface (M surface in fig. 9) of the second magnetic sensor 12 are perpendicular to the mounting surface of the gear 2, respectively. The front surfaces (N-surface in fig. 9, i.e., the surface facing the gear) of the first magnetic sensor 11 and the second magnetic sensor 12 are also perpendicular to the mounting surface (o-surface in fig. 9) of the gear 2.

The purpose of this arrangement is to ensure that the module of the gear corresponds to the modules of the first and second

magnetic sensors

11, 12, the resulting signal has good sine and cosine properties, and conversely, deteriorates. If there is a deviation between the positions of the first magnetic sensor 11 and the second magnetic sensor 12, the modulus represented by the deviation becomes small, and the signal quality is affected.

The modulus of a magnetic sensor is characterized by the spacing between internal magneto-sensitive elements. When the modulus of the magnetic sensor is the same as that of the gear, the four groups of magnetic sensing elements are arranged at equal intervals with the pitch P/4, and P is the pitch of the gear. When the module of the magnetic sensor is 2 times of the module of the gear, the four groups of magnetic sensing elements are arranged at equal intervals with the pitch P/2 distance.

In one embodiment of the invention, the tooth top surface roughness of the gear is better than 1.6, the tooth flank roughness is better than 3.2, and the tooth root surface roughness is better than 3.2.

The first magnetic sensor 11 and the second magnetic sensor 12 each include eight magnetic sensing elements, eight magnetic sensing elements are arranged in two rows and aligned up and down, the two magnetic sensing elements aligned up and down are in one group, two groups of magnetic sensing elements are arranged in a wheatstone bridge, two magnetic sensing elements at opposite angles form a half bridge, and four groups of magnetic sensing elements are arranged at equal intervals with a distance of P/4 between teeth.

In the present invention, the module of the second magnetic sensor 12 is the same as the module of the gear 2, i.e. no change is made to the second magnetic sensor 12, the second magnetic sensor 12 works on the same principle as a conventional magnetic sensor corresponding to the AB region, the phases of the two magnetic sensing elements constituting the bridge differ by 90 °, and the output differential signal is a sinusoidal signal.

The innovation point of the invention is that on the basis of not changing the internal structure of the second magnetic sensor 12, the modulus of the second magnetic sensor 12 is set to be 1.5-2.5 times of the modulus of the gear 2, so that the differential signal output by the second magnetic sensor 12 when encountering full teeth is a direct current signal, and when encountering single missing teeth 22, the differential signal output by the second magnetic sensor is a sinusoidal signal, thereby improving the signal-to-noise ratio of the Z signal.

Fig. 10 shows a positional relationship of the first magnetic sensor and the gear according to one embodiment of the present invention.

As shown in fig. 10, the first magnetic sensor 11 includes eight magneto-sensitive elements R1-R8, R1-R4, R5-R8 respectively arranged in a row, and R1 and R3, R2 and R4, R5 and R7, R4 and R8 respectively aligned up and down, R1-R4, R5-R8 respectively arranged in a wheatstone bridge, R1 and R3, R2 and R4, R5 and R7, and R4 and R8 respectively sense the same magnetic field.

When the module of the second magnetic sensor 12 is set to be 1.5-2.5 times of the module of the gear 2, the distances between R1 and R2, between R2 and R5, between R5 and R6, between R3 and R4, between R4 and R7 and between R7 and R8 are arranged at equal intervals of P/2, and P is the pitch of the gear 2.

FIG. 11 illustrates the internal structural arrangement of a first magnetic sensor, according to one embodiment of the present invention.

Since only one differential signal of the first magnetic sensor 11 is taken as an output signal, only four magnetic sensing elements R1-R4 are shown in fig. 11, where R1 and R4 form a half bridge, R2 and R3 form a half bridge, and V + and V-form a differential signal.

R1 and R4 form a half bridge, and the phase difference between R1 and R4 is changed from 90 degrees to 180 degrees. When R1 increases Δ R, R4 also increases Δ R. Similarly, when R2 increases Δ R, R3 also increases Δ R. Δ R satisfies the sinusoidal variation over one tooth period, and V + and V-are calculated by the following equations:

then V₊-V_-＝0。

When the first magnetic sensor 11 encounters full teeth, the pitch of two adjacent straight teeth is P, and the phase difference between R1 and R4 is 180 °, V₊-V_-When the differential signal is equal to 0, the output differential signal is a direct current signal.

When the first magnetic sensor 11 encounters a single missing tooth 22, the pitch of two adjacent straight teeth becomes 2P due to the lack of one straight tooth, and the phase difference between R1 and R4 is 90 °, V₊-V_-＝KsinαV_CCAnd the output differential signal is a sinusoidal signal.

As shown in fig. 12, after the first magnetic sensor 11 selects a 2-time gear modulus, the background noise of the Z signal is reduced, the signal-to-noise ratio is high, and the signal extraction is facilitated.

The differential signals outputted from R5-R8 have the same structure as R1-R4, and are not described herein again.

The invention is characterized in that a single notch is arranged in the full tooth of the Z area of the gear 2The modulus of the teeth 22 and the second magnetic sensor 12 is 1.5-2.5 times of the modulus of the gear 2, and the two designs are combined, so that when the first magnetic sensor 11 meets full teeth, the tooth pitch of two adjacent straight teeth is P, the pitch of four groups of magnetic sensing elements in the first magnetic sensor 11 is P/2, the phase difference between R1 and R4 is 180 degrees, and V is an angle₊-V_-Outputting a direct current signal when the signal is 0; when the first magnetic sensor 11 encounters a single missing tooth 22, the pitch of two adjacent straight teeth is 2P, the pitch of four sets of magnetic sensing elements in the first magnetic sensor 11 is P/4, the phase difference between R1 and R4 is 90 °, and V is₊-V_-＝KsinαV_CCAnd a sinusoidal signal is output so as to filter background noise, improve the signal-to-noise ratio and facilitate the extraction of a useful signal.

If the single missing tooth 22 is not arranged in the full teeth in the Z area, the tooth pitch of a certain position in the full teeth cannot be changed, and the phase relation between R1 and R4 cannot be changed; if the module of the first magnetic sensor 11 is not set to 2 times the module of the gear 2, the pitch of the magnetic sensor elements cannot be made P/4. Therefore, the filtering of the background noise, the setting of the single missing tooth 22 and the change of the modulus of the first magnetic sensor 11 are both not possible.

In order to satisfy the phase relationship between the encoder A, B signal and the Z signal, it is common practice to delay the Z signal to adjust the phase of the Z signal. The present invention employs a physical method to shift the first magnetic sensor 11 relative to the second magnetic sensor 12 in the horizontal direction by a certain distance to satisfy the phase relationship. When the center line 13 of the sensing area of each of the first magnetic sensor 11 and the second magnetic sensor 12 is located on the extended radius line 24 of the gear 2, the phase relationship is as shown in fig. 13, and the phase difference is T/4. The arc length of the tooth top of the corresponding gear 2 is mP/4, the first magnetic sensor 11 is moved by the distance mP/4, the equal amplitude point of the A, B signal is overlapped with the maximum amplitude point of the Z signal, and the phase relation between the A, B signal and the Z signal is met.

In the description herein, references to the description of the term "one embodiment," "another embodiment," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

The above embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A gear type encoder comprises a reading head and a gear, wherein the reading head comprises a first magnetic sensor corresponding to a Z area of the gear, four groups of magnetic sensing elements which are arranged in two rows in an up-down alignment mode are arranged inside the first magnetic sensor, and each two magnetic sensing elements form a half bridge.

2. The gear-type encoder of claim 1, wherein the read head further comprises a second magnetic sensor corresponding to the AB region of the gear, the modulus of the second magnetic sensor being the same as the modulus of the gear.

3. The gear-type encoder of claim 2, wherein the central lines of the sensing regions of the first magnetic sensor and the second magnetic sensor respectively face the radial extension lines of the gear, and the first magnetic sensor is offset from the second magnetic sensor by a distance of m pi/4 in the horizontal direction, m being the module of the gear.

4. The geared encoder according to claim 1, wherein a line of the gear in the tooth width direction is used as a boundary line to divide the gear into two parts, one part is a full-tooth spur gear, and the other part is a single missing tooth formed by blanking from a tooth crest to a tooth root of a spur tooth of the full-tooth spur gear.

5. The geared encoder of claim 4, wherein the second magnetic sensor is located at a distance of 2.5mm or more from the dividing line, and the first magnetic sensor is located at a distance of 2mm or more from the dividing line.

6. The gear type encoder according to any one of claims 1 to 5, wherein the side faces and the front faces of the first magnetic sensor and the second magnetic sensor are perpendicular to the mounting face of the gear, respectively.

7. The gear-type encoder according to any one of claims 1 to 5, wherein the diameter of the addendum circle of the gear is more than or equal to 20 mm.

8. The geared encoder of any one of claims 1 to 5, wherein the gear has a tooth tip roughness of better than 1.6, a tooth face roughness of better than 3.2 and a tooth root surface roughness of better than 3.2.