Small absolute photoelectric encoder

Abstract

The invention provides a small absolute photoelectric encoder, and belongs to the technical field of sensors. Comprising a shaft, an upper cover, a light source plate, a grating code disc, a slit code disc, a circuit board and a lower cover. The lower cover and the upper cover are fixedly connected to form a main body structure; the light source plate, the grating code disc, the slit code disc and the circuit board are sequentially arranged in an inner cavity formed by the upper cover and the lower cover from top to bottom; the shaft is supported in the center of the upper cover through a bearing, one end of the shaft extends out of the upper cover, the light source plate and the grating coded disc are sleeved on the shaft arranged in the upper cover, a center hole of the light source plate is sleeved with the shaft in a clearance mode, the light source plate is fixedly connected with the inner wall of the upper cover, the grating coded disc is fixedly connected with the shaft, and the slit coded disc and the circuit board are coaxially fixed in the lower cover. According to the invention, a unique slit code disc design is utilized to realize an angle measurement mode combining Gray code and chord tangent angle detection, and on the premise that the precision is not changed, the size of the Gray code disc is greatly reduced, so that the overall size of the encoder is reduced, and the application requirements of small instrument equipment are met.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors, and in particular relates to a small absolute photoelectric encoder suitable for angular position measurement of small instrument equipment with an angle function. Background Art

[0002] Photoelectric encoder is a kind of sensing device widely used in the field of industrial control and automation. Its main function is to convert physical quantities such as angle and position into electrical signals for output using the principle of photoelectric effect. According to different measurement methods, photoelectric encoders are divided into two types: rotary encoders for measuring rotation and ruler encoders for measuring linear position. Rotary photoelectric encoders can be divided into incremental encoders and absolute encoders. Incremental encoders are mainly used to measure the rotation speed of rotating mechanisms, and absolute encoders are mainly used to measure the angular position of rotating mechanisms. As for absolute photoelectric encoders, at present, the absolute photoelectric encoders on the market are large in size, which limits their application in small instrument equipment with angle functions. Therefore, it is necessary to design a small absolute photoelectric encoder with small size, high precision and strong environmental adaptability. Summary of the invention

[0003] The technical problem solved by the present invention is to provide a small absolute photoelectric encoder. The purpose of the present invention is to use a unique slit code disk design to realize an angle measurement method that combines Gray code and chord angle detection. Under the premise of unchanged accuracy, the volume of the Gray code disk is reduced, thereby reducing the overall volume of the encoder to meet the application requirements of small instrument equipment.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A small absolute photoelectric encoder comprises a shaft, an upper cover, a light source board, a grating code disk, a slit code disk, a circuit board and a lower cover; the lower cover is fixedly connected to the upper cover to form a main structure, and the light source board, the grating code disk, the slit code disk and the circuit board are arranged in sequence from top to bottom in an inner cavity formed by the upper cover and the lower cover; the shaft is supported at the center of the upper cover through a bearing, one end of the shaft extends out of the upper cover, the light source board and the grating code disk are sleeved on the shaft placed inside the upper cover, the center hole of the light source board is sleeved with the shaft gap, the light source board is fixedly connected to the inner wall of the upper cover, the grating code disk is fixedly connected to the shaft, and the slit code disk and the circuit board are coaxially fixed inside the lower cover.

[0006] To further define the above scheme, the outer shape of the main structure formed by the lower cover and the upper cover is Ф30mm×15mm, the axis extending out of the upper cover forms a Ф3mm×10mm connection interface, and there are 3 M3 installation interfaces evenly distributed on the outer circumference of the upper cover, and the outer diameter of the installation interface is Ф35mm.

[0007] As a further limitation of the above solution, the grating code disk adopts a Gray code glass grating code disk made of 7 glass stripes with a size of 22 mm×1 mm.

[0008] To further define the above scheme, the slit code disk adopts a stainless steel slit code disk of Ф25mm×0.5mm, and the slit code disk has a fan-shaped hole at the array position corresponding to the grating code disk on its radius and at a position (N+0.75)×α away from the array (where N is any odd number from 1 to 127, and α is 2.8125°, that is, this hole can be selected arbitrarily from the 64 positions where N takes the value), with a length (distance on the diameter) of 0.8mm and a width consistent with the minimum unit of the grating code disk, so that the infrared laser can pass through.

[0009] As a further limitation of the above solution, the light source board includes four 940nm infrared laser emitting diodes with an outer diameter of 2mm installed in the same straight line and one independently installed diode of the same specification.

[0010] To further limit the above scheme, the circuit board is provided with a signal acquisition and result output circuit, which includes 8 940nm infrared laser receiving transistors, 6 integration circuits, 2 signal amplification circuits, 2 analog / digital conversion chips and a signal transceiver circuit based on an ARM microcontroller.

[0011] The advantages of the present invention compared with the prior art are:

[0012] 1. This scheme is a small absolute photoelectric encoder. It uses a unique slit code disk design to realize the angle measurement method combining Gray code and chord angle detection. Under the premise of unchanged accuracy, it greatly reduces the volume of Gray code disk, thereby reducing the overall volume of encoder; at the same time, it reduces the cost and improves the anti-vibration performance, meeting the application requirements of small instrument equipment;

[0013] 2. The design principle of this scheme is concise and clear, the structure is simple, and all components can be domestically produced, thus getting rid of the restrictions on imported components. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is the appearance structure diagram of the present invention;

[0015] Figure 2 It is a structural exploded diagram of the present invention;

[0016] Figure 3 It is a schematic diagram of the structure of the grating code disk in the present invention;

[0017] Figure 4 It is a schematic diagram of the structure of the slit code disc in the present invention;

[0018] Figure 5 It is a structural cross-sectional view of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0021] See also Figure 1-5 , describe the embodiments of the present invention in detail.

[0022] Example: See Figure 2 and 5 As shown, a small absolute photoelectric encoder comprises a shaft 1, an upper cover 3, a light source board 4, a grating code disk 5, a slit code disk 6, a circuit board 7 and a lower cover 8; the lower cover 8 is fixedly connected to the upper cover 3 to form a main structure, and the light source board 4, the grating code disk 5, the slit code disk 6 and the circuit board 7 are arranged from top to bottom in the inner cavity formed by the upper cover 3 and the lower cover 8 in sequence; the shaft 1 is supported at the center of the upper cover 3 by a bearing 2, one end of the shaft 1 extends out of the upper cover 3, and the shaft 1 placed inside the upper cover 3 is sleeved with a light source board 4 and a grating code disk 5, the center hole of the light source board 4 is gap-fitted with the shaft 1, the light source board 4 is fixedly connected to the inner wall of the upper cover 3, the grating code disk 5 is fixedly connected to the shaft 1, and the slit code disk 6 and the circuit board 7 are coaxially fixed inside the lower cover 8.

[0023] The structure and appearance of this small absolute photoelectric encoder refer to Figure 1 As shown, the main structure formed by the lower cover 8 and the upper cover 3 has an outer shape of Ф30mm×15mm, and the shaft 1 extending out of the upper cover 3 forms a connection interface of Ф3mm×10mm. The outer circumference of the upper cover 3 is evenly distributed with three M3 installation interfaces, and the outer diameter of the installation interface is Ф35mm.

[0024] The above makes the main structure outer diameter only 30mm (minimum 25mm) and height 15mm, which is particularly suitable for small instrument equipment with corner function. Preferably, the main structure material of the photoelectric encoder is aluminum alloy 2A12, which has high strength, light weight and corrosion resistance.

[0025] Schematic diagram of the grating code disk and slit code disk of this small absolute photoelectric encoder, as shown in Figure 3 and 4 As shown:

[0026] The grating code disk 5 is a Gray code glass grating code disk made of 7 glass stripes with a size of 22 mm×1 mm, wherein the dark color is for shielding and the white color is for transmitting light.

[0027] The slit code disk 6 adopts a stainless steel slit code disk of Ф25mm×0.5mm. The slit code disk 6 has a fan-shaped hole at the array position corresponding to the grating code disk on its radius and at a position (N+0.75)×α from the array (where N is any odd number from 1 to 127, and α is 2.8125°, that is, this hole can be selected arbitrarily from the 64 positions where N takes the value), with a length (distance on the diameter) of 0.8mm and a width consistent with the minimum unit of the grating code disk, so that the infrared laser can pass through.

[0028] In the above structure, the grating code disk is designed as a 7-track glass Gray code disk with a diameter of 22 mm, and is equipped with a specially designed stainless steel slit code disk to realize an angle measurement method combining Gray code and chord angle detection.

[0029] In the small absolute photoelectric encoder, the light source board 4 includes four 940nm infrared laser emitting diodes with an outer diameter of 2mm installed in the same straight line and one independently installed diode with the same specification.

[0030] The circuit board 7 is provided with a signal acquisition and result output circuit, which includes 8 940nm infrared laser receiving transistors, 6 integration circuits, 2 signal amplification circuits, 2 analog / digital conversion chips and a signal transceiver circuit based on an ARM microcontroller.

[0031] In the above structure, the signal acquisition and result output circuit is composed of infrared laser receiving transistor, integration circuit, analog amplifier circuit, analog / digital conversion chip and embedded system based on ARM single chip microcomputer, which finally realizes angle detection and digital signal output with an accuracy of more than 10″.

[0032] The angle detection principle of this small absolute photoelectric encoder:

[0033] The light source board provides 940nm infrared laser at the corresponding positions of the 8 openings of the slit code disk. When the laser irradiates the inner 6 tracks of the Gray grating code disk, it will present different states of pass and resistance according to the Gray code values ​​at different positions.6 The state value can locate the angle of the code disk to an accuracy of 360÷64=5.625°. When the laser passes through the Gray code disk and the slit code disk to irradiate the infrared laser receiving transistor at the corresponding position of the circuit board, a photocurrent is formed on it, generating a DC voltage, which is then amplified by the integration circuit to form a logic "1" voltage that can be recognized by the single-chip microcomputer. The blocked position has no voltage and becomes a logic "0". The single-chip microcomputer reads the encoding state of the inner 6 channels and can determine the code disk position θ with an angle accuracy of 5.625°. 1 The two openings on the outermost track differ by 1 / 4 of an angle period. The DC voltage generated by the infrared laser receiving transistor at the corresponding position of the circuit board presents a sine-cosine relationship after differential amplification. The corresponding angle β (β is within the range of -180° to 180°) can be calculated based on the positive and negative states of the two and the inverse tangent / inverse cotangent. The relative angular position on the outer track is θ 2 =5.625·β / 360, and finally the grating code disk angle can be determined to be θ=θ 1 +θ 2 .

[0034] The shaft of the small absolute photoelectric encoder is fixedly connected to the grating code disk, and the rotating shaft of the external instrument equipment is fixedly connected to the shaft of the encoder. The angular position of the rotating shaft of the external instrument equipment can be detected by detecting the angle of the grating code disk.

[0035] In summary, this small absolute photoelectric encoder uses a unique slit code disk design to realize an angle measurement method that combines Gray code and chord angle detection. Under the premise of unchanged accuracy, it greatly reduces the volume of the Gray code disk, thereby reducing the overall volume of the encoder; at the same time, it reduces costs and improves vibration resistance to meet the application needs of small instrumentation equipment; the design principle is concise and clear, the structure is simple, and components can all be domestically produced, getting rid of the restrictions on imported components.

[0036] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0037] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A small absolute photoelectric encoder, characterized in that: The invention comprises a shaft (1), an upper cover (3), a light source board (4), a grating code disk (5), a slit code disk (6), a circuit board (7) and a lower cover (8); the lower cover (8) is fixedly connected to the upper cover (3) to form a main structure; the light source board (4), the grating code disk (5), the slit code disk (6) and the circuit board (7) are arranged in sequence from top to bottom in an inner cavity formed by the upper cover (3) and the lower cover (8); the shaft (1) is supported at the center of the upper cover (3) through a bearing (2); one end of the shaft (1) extends out of the upper cover (3); the shaft (1) disposed inside the upper cover (3) is sleeved with the light source board (4) and the grating code disk (5); the center hole of the light source board (4) is gap-fitted with the shaft (1); the light source board (4) is fixedly connected to the inner wall of the upper cover (3); the grating code disk (5) is fixedly connected to the shaft (1); and the slit code disk (6) and the circuit board (7) are coaxially fixed inside the lower cover (8).

2. A small absolute photoelectric encoder according to claim 1, characterized in that: The main structure formed by the lower cover (8) and the upper cover (3) has an outer shape of Φ30 mm×15 mm, and the shaft (1) extending out of the upper cover (3) forms a connection interface of Φ3 mm×10 mm. The outer circumference of the upper cover (3) is evenly distributed with three M3 installation interfaces, and the outer diameter of the installation interface is Φ35 mm.

3. A small absolute photoelectric encoder according to claim 1, characterized in that: The grating code disk (5) is a Gray code glass grating code disk made of 7 glass stripes and having a size of 22 mm x 1 mm.

4. A small absolute photoelectric encoder according to claim 1, characterized in that: The slit code disk (6) is a stainless steel slit code disk of Φ25mm×0.5mm. The slit code disk (6) has a fan-shaped hole at an array position corresponding to the grating code disk on its radius and at a position (N+0.75)×α from the array, wherein N is any odd number from 1 to 127, and α is 2.8125°, that is, the hole can be selected at any of the 64 positions where N takes the value, and the length, i.e., the distance on the diameter, is 0.8mm, and the width is consistent with the minimum unit of the grating code disk, so that the infrared laser can pass through.

5. The small absolute photoelectric encoder according to claim 1, characterized in that: The light source plate (4) comprises four 940nm infrared laser emitting diodes with an outer diameter of 2mm installed in the same straight line and one independently installed diode with the same specification.

6. A small absolute photoelectric encoder according to claim 1, characterized in that: The circuit board (7) is provided with a signal collection and result output circuit, which comprises 8 940nm infrared laser receiving transistors, 6-way integration circuits, 2-way signal amplification circuits, 2-way analog / digital conversion chips and a signal transceiver circuit based on an ARM single chip microcomputer.

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