Modular optical angle encoder

TECHNICAL FIELD

The invention relates to precision angle measuring devices. It can be applied to measuring the angle of rotation and/or absolute angular position of rotating shafts in various technological and metrological devices.

STATE OF THE ART

Optical rotary I angle encoders are devices designed to measure angular displacement (rotation) or absolute angular position. They are used in various industrial and scientific devices where accurate angle measurement is required. These encoders are an important part of many applications. They are integrated into robotic systems, CNC machine tools, medical equipment, aerospace equipment, etc.

Modular, open-type, angle transducers do not have an axis and bearing system, therefore they are characterized by small dimensions and mass, do not have wearing components, and are therefore more resistant to mechanical and temperature stress or vibrations. Such transducers consist of two main parts: a statohaus and a rotor. The rotor is mounted directly on the axis of the measured object and rotates with it during operation of the device. Depending on the operating principle of the angular transducer (optical, magnetic, inductive, etc.), the rotor consists of a metal sleeve with a concentrically mounted angular position indicator, such as a circular glass limb with a raster structure or a correspondingly magnetized precision scale. Meanwhile, the stator is mounted on the device body and remains in a stationary position during its operation. In turn, it consists of a printed circuit board (PCB) mounted in its own housing or separately mounted, on which a semiconductor sensor is mounted. As for optical transducers, such a sensor detects the light flux generated by the luminaire and modulated by the rotating raster structure and generates periodic electrical signals proportional to it. Various forms of statohaus and methods of its installation are known. In patent US 6,960,758 B2 the printed circuit board of the transducer is stationary, as a separate component, in relation to the glass limb. In patent US 11,316,418 B2 the transducer has a circular electrical board with a hole in the middle through which the measuring axis is concentrically fixed to a stationary housing.

Since modular optical angle transducers do not have their own bearing system to maintain the appropriate position between the angle gauge and the sensor (as is ensured in closed-type angle transducers), the mechanical positioning of these components during installation and maintaining this position during operation of the device is their biggest drawback. Incorrect mutual position affects the quality of the electrical signals formed and has a direct impact on the accuracy of angle measurement or even the operation of the entire device. Optimal alignment of the rotor and stator requires significant time expenditure, strict tolerances of the base surfaces of the device whose angular position is measured, or special tools. Additional equipment is often required to monitor the quality of the electrical converter signals and perform stator positioning based on it. In order to eliminate these shortcomings, the design of closed-type stators with modular converters began, and the appropriate rotor position was ensured by additional centering and support elements.

Patent US 8,181,353 B2 describes an inductive modular converter in which the rotor is supported in a closed stator housing. During installation, the device is placed on the measuring axis (with respect to the inner rotor hole) and pushed along its surface until the supporting surface of the stator housing contacts the device housing. In this static position, the rotor is fixed by tightening its sleeve on the axis accordingly. The stator housing is then rotated relative to the rotor until the shaped elements on its base surface align with the corresponding cavities made in the device housing. The stator is gently pressed until it is finally positioned on the device and tightened with the locking screws. This axial displacement of the converter stator is precisely defined by the height of the elements on its base surface. In its final position, a nominal gap of the same size appears (and is thus ensured) between the angle gauge of the converter and the sensor. However, this method of mounting the converter does not ensure radial positioning of the stator, therefore it requires the appropriate preparation of the device housing, forming in it recesses for stator centering and defined height elements.

Patent US 8,360,554 B2 describes a modular angle converter having a specially configured rotor sleeve with a groove concentric with the diameter of its inner hole and a stator housing with a mounting ring formed correspondingly at the diameter of its inner hole. During installation, the rotor sleeve is pressed into the housing so that the mounting ring is located in the rotor groove. To facilitate this, notches of the appropriate size are made along the rotor sleeve, due to which it can be elastically compressed and pressed into the stator. The dimensions of the groove and the mounting ring are selected so as to ensure the necessary mutual position tolerances. Although such a design ensures the required position of the stator and rotor, the mounting ring slides along the surface of the groove during operation of the converter. Such contact causes friction, which can eventually affect the durability of the device and requires the use of materials with appropriate frictional properties.

ESSENCE OF THE INVENTION

The aim of the invention is to create a modular optical angle transducer, the mounting method of which would ensure the appropriate mutual position of the angle gauge and the optical sensor, thus achieving high measurement accuracy.

In order to ensure a reliable and efficient installation procedure for an optical modular transducer, a method for positioning the relative position of the stator and rotor is presented, which allows ensuring the correct relative position of the transducer angle gauge and sensor with respect to the measured axis. A modular optical angle transducer has been developed, consisting of a closed-type stator, a rotor located inside it, and a specially shaped flexible guide for axial and radial positioning of the rotor relative to the stator. The specialized shape of the positioning guide has an external thread, a concentrically formed thin-walled ring with an external parabolic-shaped and internal cylindrical surfaces. The thin-walled ring has several notches of appropriate size in the longitudinal direction, which form several spring segments. When the guide is screwed into the corresponding threaded surface of the stator housing, the outer surface of the parabolic thin-walled ring comes into contact with the supporting conical surface of the housing. As the guide continues to rotate, the resulting axial force causes the outer surface of the thin-walled ring to slide along the inclined support surface, thereby elastically deforming the spring-loaded guide segments. The compressing segments contact the cylindrical surface of the rotor sleeve with the inner surface of the thin-walled ring, thus centering and locking the concentric position of the rotor relative to the stator. During this process, the axial position of the rotor is ensured by aligning the lower surface of the sleeve and the base surface of the stator on a solid flat base.

The installation method of the presented optical modular angle transducer is simple, quick and does not require additional tools or specialized equipment. Precise positioning of the components ensures measurement accuracy, as the sensor is positioned within the operating tolerances with respect to the angle measurement. The requirements for preparing the device in which the transducer is installed are minimal. Additional machining of the supporting surfaces of the device body or boring of the step on the axis is not required, therefore integration of such a converter into many technological devices is easily realized. The presented example of a modular optical angle converter should not be considered limiting with regard to the principle of operation of modular converters, the design of the constituent parts, the relative size of each other and 1.1., but should be considered only as a possible example of the implementation of the invention.

DESCRIPTION OF DRAWINGS

Fig. 1 Exploded isometric view of an optical modular angle transducer;

Fig. 2 Isometric cross-sectional view of an optical modular angle transducer;

Fig. 3 (a) - enlarged projection of the detailed image A from Fig. 2 ;

(b) - enlarged detailed view B

Fig. 4 Isometric cross-sectional view of a flexible positioning guide;

Drawings - Description of marked objects

- stator;

- stator flange;

11.1- base surface;

11.2- mounting cavities;

- stator housing;

12.1 - internal threaded surface;

12.2 - inclined support surface;

- printed electronics board;

13.1 - optical sensors;

- positioning guide;

14.1 - grooved surface;

14.2 - threaded surface;

14.3 - thin-walled ring;

14.4 - outer surface of a parabola;

14.5 - inner cylindrical surface;

14.6 - thin-walled ring notches;

14.7 - spring segments;

- guide fixing screws;

​ - rotor;

- rotor bushing;

21.1 - bushing alignment surface;

21.2 - outer cylindrical surface of the bushing;

21.3 - inner cylindrical surface of the bushing;

21.4 - outer conical surface of the bushing;

- glass limb;

22.1 - raster scale structure;

- sleeve clamping ring;

- bushing tightening screws;

- bushing release bolts;

Z - central axis;

S - nominal axial gap (between optical sensor and glass disc);

O - contact point (between the positioning guide and the stator housing);

X- radial displacement (in the direction indicated in the drawing);

Y - axial displacement (in the direction indicated in the drawing);

H - initial nominal gap (between the positioning guide and the rotor sleeve).

DETAILED DESCRIPTION OF THE INVENTION

Description of the modular optical angle converter.

The presented modular optical angle transducer consists of two groups of elements: a stator (10), the components of which are fixed in a stationary position on the device, and a rotor (20), which is mounted on the measuring axis and rotates with it. During operation of the mounted transducer, the rotor (20) and stator (10) are arranged so that they can rotate freely relative to each other about the axis (Z).

The stator (10) of the converter consists of: a flange (11), a housing (12), in which a printed circuit board (13) with several semiconductor optical sensors (13.1) located thereon is permanently installed, and a positioning guide (14) with several fixing screws (15). The housing (12) is attached to the flange (11) with screws (16).

The rotor (20) consists of: a sleeve (21) with a glass limb (22) glued to it, on the surface of which a raster scale structure (22.1) is formed by photolithography, which is used as a precise angle measure, and a clamping ring (23) of the sleeve (21) with tightening (24) and loosening (25) screws.

During measurement, the light flux emitted by the light-emitting diodes integrated in the optical sensors (13.1) falls at a corresponding angle onto the raster scale structure (22.1) of the glass disk (22). The modulated light flux reflected from its surface returns to the sensors (13.1), where it is converted into corresponding electrical signals that determine the absolute angular position. For the converter to function properly and to maintain measurement accuracy, the optical sensors (13.1) must be in their nominal position with respect to the raster scale (22.1). Therefore, during installation, centering and axial alignment of the stator (10) and rotor (20) must be performed.

Detailed description of the inverter installation method.

In the assembled converter, the rotor (20) is located in the inner part of the stator (10) (i.e. it is enclosed by the housing (12) and the flange (11)) and can move freely. The nominal axial gap (S) between the optical sensors (13.1) and the glass limb (22) is ensured by aligning the alignment surfaces of the sleeve (21.1) and the flange base (11.1). The alignment is performed by pressing the aforementioned surfaces against a flat and solid base (P). Then the rotor (20) is centered with the help of the positioning guide (14). When the guide is rotated by the grooved surface (14.1), its threaded surface (14.2) engages the threaded surface of the housing (12.1). A concentric thin-walled ring (14.3) is formed on the positioning guide (14) with an external parabolic (14.4) and an internal cylindrical (14.5) surface. The thin-walled ring (14.3) has several notches (14.6) of appropriate size in the longitudinal direction, which form several spring-loaded segments (14.7). Under the action of the axial force (F) arising during rotation, the parabolic surface (14.4) starts to slide along the conical support surface of the housing (12.2), and the spring segments (14.7) are elastically deformed. During deformation, the spring segments compress, and the contact point (O) of the parts sliding along the inclined support surface shifts in the radial (X) and axial (Y) directions (as shown in Fig. 3 (b)). In this way, the initial nominal gap (H) between the cylindrical surfaces of the inner thin-walled ring (14.5) and the outer rotor sleeve (21.2) begins to decrease evenly until the sleeve (21) is fully centered and clamped.

After positioning and securing the rotor (20) in relation to the stator (10), the installation of the converter on the device begins. The converter is mounted on the measuring axis of the device with the inner cylindrical surface of the rotor sleeve (21.3) until the base surface of the stator flange (11.1) touches the device housing. The stator flange (11) is screwed to the device housing through the mounting holes (11.2). When tightening the clamping screws (24), the clamping ring (23) slides along the conical surface of the rotor sleeve (21.4) thus tightening the sleeve (21) on the axis of the device. The positioning guide (14) is unscrewed and the outer surface of the sleeve (21.2) is released so that the rotor (20) can rotate freely. The position of the loosened positioning guide is secured with the locking screws (15).