CN112888923A

CN112888923A - Electric motor with thermochromic member

Info

Publication number: CN112888923A
Application number: CN201980069712.XA
Authority: CN
Inventors: R·维斯塔普
Original assignee: Ebien Peter Mulfingen GmbH
Current assignee: Ebien Peter Mulfingen GmbH; Ebm Papst Mulfingen GmbH and Co KG
Priority date: 2018-12-18
Filing date: 2019-11-06
Publication date: 2021-06-01
Also published as: DE102018132743A1; WO2020126190A1; CN210093061U; EP3833948A1

Abstract

The invention relates to an electric motor having a component, wherein the component is at least partially formed from a thermochromic material or a surface (14, 15, 16) thereof is provided with a coating made of the thermochromic material, and wherein the electric motor has a camera (21) which is configured to capture the surface (14, 15, 16) of the component by means of an imaging technique, and an evaluation unit which is configured to determine a two-dimensional temperature field along the surface (14, 15, 16) from an image captured by the camera (21).

Description

Electric motor with thermochromic member

Technical Field

The invention relates to an electric motor having components for temperature detection and temperature monitoring and a method for temperature detection and temperature monitoring.

Background

Temperature monitoring of electric motors is known in the prior art. For this purpose, sensors such as thermal switches or thermal sensor elements are usually used, which measure the temperature, in particular, at the windings of the electric motor. However, such sensors can only detect temperature point by point. In order to be able to perform planar temperature monitoring, it is known to calculate a temperature distribution from point-by-point detected temperature values by means of a thermal model. However, this sometimes requires a high computational power, so that the hardware necessary for the calculation is expensive and takes up a lot of space, and furthermore, the thermal model for the calculation based on the temperature distribution may be erroneous, often unable to adapt to the condition changes, and in some cases unable to adapt. For example, the calculated temperature distribution may deviate from the actual temperature distribution due to wear or due to maintenance measures performed. By using a large number of sensors, a more accurate temperature distribution can be calculated, but there is still the problem that the model used for this purpose is often not in accordance with the actual situation.

Alternative methods for planar temperature detection or electric motors that detect temperature by methods such as thermal imaging cameras are often cost prohibitive and therefore not economically efficient for long term temperature monitoring.

Disclosure of Invention

In view of the above, it is an object of the present invention to overcome the above-mentioned drawbacks and to provide an electric motor and a method with which a planar temperature distribution on a component can be detected cost-effectively and economically.

The solution of the invention to achieve the object is the combination of features according to claim 1.

According to the invention, an electric motor is proposed having a component which is at least partially formed from a thermochromic material or is provided on its surface with a coating made of a thermochromic material. The electric motor also has a camera and an evaluation unit. The camera is configured to capture the surface of the component by imaging techniques and preferably in color. The evaluation unit is configured to determine a two-dimensional temperature field along the surface from the images captured by the camera. In addition to using a color camera to capture color images and determine temperature from color, a black and white camera may be used, where instead of assigning color to temperature, a grayscale is assigned.

By means of the thermochromic material, the component is configured to change color with the component temperature, such that the color change or a resulting color gradient on the surface can be captured by the camera.

Thermochromic color is the property of a particular substance to change color when the temperature changes. The process is reversible such that the substance or component returns to its original color after cooling. The color change is caused by a change in molecular structure or crystal structure.

Thus, the component may for example be made of a mixture of a backing material, such as plastic, and a thermochromic substance. As an alternative to being processed into a mixture of parts, for example by an injection molding process, the surface of the parts can also be coated with a thermochromic material, such as a pigment or lacquer. Such thermometric pigments (also known as thermochromic pigments or thermochromic pigments) are coating materials that indicate a change in temperature by a color transition or color change.

Depending on the thermochromic substance used, a temperature change leads, for example, to a change from white to green or from black to cyan-green.

In order to be able to detect the temperature inside the electric motor or in the dark, an advantageous development provides that the electric motor further comprises an illumination means which is configured to illuminate the surface captured by the camera. For this reason, LEDs are particularly advantageous as illumination means, which do not generate temperature or only slight temperature themselves and do not additionally heat up the surface illuminated by them or the room illuminated by them. Another embodiment is advantageous in that the component defines a cavity and the surface captured by the camera is an inner surface of the component facing the cavity. So that the camera can capture a larger area.

In a variant of the invention, it is also particularly advantageous if the electric motor comprises a stator with a plurality of stator windings, and a gap is defined between two immediately adjacent stator windings of the plurality of stator windings, in which gap a component is arranged.

The stator preferably comprises a plurality of stator teeth arranged in a star shape, wherein the stator teeth can be in a T-shaped configuration and the stator windings are each arranged or wound on a stator tooth. The distance between the stator windings or between the stator teeth corresponds to a gap, wherein the component can be arranged in at least one gap. The components are preferably in close proximity to one or more stator windings in direct abutment or are separated only by a narrow air gap so that heat from the stator windings is transferred to the components in direct abutment or in direct proximity. In this case, heat is transferred to the outer surface facing the stator windings, thereby warming the component and discoloration of the thermochromic material on the surface, preferably the inner surface opposite the outer surface on the component, can be captured by the camera. Between two immediately adjacent stator teeth, a stator winding or turns of a stator winding, or alternatively two stator windings or turns of two stator windings, may be arranged.

If the temperature or the temperature distribution of a particular electric motor component or stator winding is to be detected, a variant of the invention is advantageous if the component is configured as a cladding which defines a cavity and adjoins directly or closely adjacent to the adjacent stator winding with an outer surface facing away from the cavity. Here, immediately adjacent means that the outer surface of the one or more parts is only spaced from the stator winding by a narrow air gap of preferably at most 1 mm. It is further provided that the envelope is formed from a thermochromic material or is coated with a thermochromic material on its inner surface facing the cavity. The illumination mechanism is further configured to illuminate the cavity and an inner surface of the enclosure facing the cavity. The camera is further configured to capture, via imaging techniques, the cavity and an inner surface of the envelope facing the cavity. In addition, an embodiment of the electric motor is advantageous in that the electric motor has a rotor which can be rotated about a stator.

The cavity defined by the enclosure is further open in a radial direction toward the rotor, and the camera is configured to capture the rotor by imaging techniques. By capturing the rotor by imaging techniques or camera techniques, the position of the rotor relative to the stator can be determined and this can be used to control the electric motor for the rotor position.

In order to detect the position of the rotor in a precise manner relative to the stator, an advantageous development further provides that the inner surface of the rotor facing the stator is provided with a corner mark which surrounds the stator and can be captured by a camera. By means of the angle marking, points or segments of the rotor are assigned or can be assigned a relative rotational angular position relative to the stator.

In order to be able to determine the temperature distribution or the temperature field from the image captured by the camera, a further advantageous variant of the invention provides that the camera is configured to capture the surface of the component by means of imaging techniques and color, and the evaluation unit is configured to assign temperature values to the colors in the image of the surface captured by the camera and to determine the two-dimensional temperature field along the surface of the component from the temperature values assigned to the surface.

In a further embodiment, it is advantageous if the two-dimensional temperature field determined by the evaluation unit is a scalar field in which a temperature value is assigned to each point on the surface of the component captured by the camera.

In addition to the temperature distribution or the temperature field, further characteristic values can also be captured by the camera and determined by the evaluation unit. To this end, a further development of the invention provides that the evaluation unit is further configured to determine the degree of surface contamination and/or the state of the surface or component from the images captured by the camera. In addition to surfaces, the space captured by the camera (e.g., the cavity defined by the components) may also be used to monitor and detect measurements. If smoke is trapped in the cavity, for example by a camera, the smoke can be determined by an evaluation unit, so that overheating or defects can be inferred and measures can be taken in terms of control technology. Depending on the camera used, the intensity or exact color of the color in the image taken by the camera may be slightly different. This may also occur for cameras of the same model. In order to avoid having to adjust the cameras individually or else to evaluate evaluation units of the images from a plurality of cameras, an advantageous variant provides that a high-temperature-resistant color scale is provided on the surface, which can be captured by the cameras and assigns a specific temperature to a specific color, wherein a temperature or a temperature limit is assigned to each color. The evaluation unit is preferably configured to assign specific temperatures to the colors in the color patch from the captured color patch and to determine a temperature distribution of the surface of the component captured in the image from these temperatures. This eliminates the need for manual adjustment or calibration of the evaluation unit or camera. Here, the color scale may for example only preset two values, such that for example a first color represents a temperature of at most 50 ℃ and a second color represents a temperature above 100 ℃. Alternatively, the color scale can also reproduce different color intensities, colors or color gradients, so that different colors or color gradations can be assigned temperature values. Since the surface area covered by the patches is extremely small, the temperature actually present in the patch area can be calculated from the temperature of the surface area adjacent to the patches, for example by interpolation.

It should be possible to determine the surface temperature distribution on the components of the electric motor, so that an advantageous embodiment of the electric motor provides that a position marker is arranged on the surface, which can be captured by the camera and which assigns a specific position value to a point or segment on the surface, respectively. The evaluation unit can thus assign a specific position to the temperature values detected by means of color. The index can also be configured as a grid or mesh which preferably extends over the surface.

The component can also be designed as a closed or longitudinally open hollow cylinder which defines a cavity in its interior and accommodates the camera and the illumination means. In this case, the hollow cylinder may be arranged completely in the stator winding.

Another aspect of the invention relates to a method for detecting a two-dimensional temperature field along a surface of a component. The component is at least partially formed of a thermochromic material or is provided with a coating made of a thermochromic material on its surface. In addition, the surface is formed of a thermochromic material and changes color depending on the temperature of the component on the surface. In addition, for the method, a camera is provided which captures the surface of the component by means of imaging technology, wherein the image captured by the camera is transmitted to the evaluation unit. The evaluation unit assigns a temperature value for the color according to the surface image captured by the camera. The evaluation unit preferably assigns a temperature value to a specific point on the surface. From the temperature values assigned to the surface, a two-dimensional temperature field along the component surface is determined by the evaluation unit.

According to a further aspect of the invention, a method for detecting a two-dimensional temperature field on a stator winding of an electric motor is also proposed. A component is arranged on the stator winding, wherein the component is at least partially formed of a thermochromic material or is provided with a coating made of a thermochromic material on a surface thereof. The surface is formed of a thermochromic material and changes color depending on the temperature of the component on the surface. For this method, a camera is likewise provided, which captures the surface of the component, wherein the image captured by the camera is transmitted to the evaluation unit. From the image of the surface, preferably of a specific point on the surface, the evaluation unit assigns a temperature value to the color and determines a two-dimensional temperature field along the surface of the component from the temperature values assigned to the surface. The two-dimensional temperature field of the stator winding or the component-facing surface of the stator winding is determined from the assigned temperature values for the surface.

An advantageous development of the method also provides that the electric motor comprises a stator with a plurality of stator windings and that the component is arranged as a jacket in a gap between two stator windings juxtaposed to one another and directly adjoins the juxtaposed stator windings or is adjacent thereto. The evaluation unit assigns temperature values to the colors in the image of the surface and determines a two-dimensional temperature field along the component surface from the temperature values assigned to the surface and thereby a two-dimensional temperature field of the respective stator winding for each of the two stator windings juxtaposed to one another.

Drawings

Further advantageous developments of the invention are specified with reference to the features of the dependent claims or in the following with reference to the drawings in conjunction with the description of preferred embodiments of the invention. In the figure:

FIG. 1 illustrates a stator of an electric motor;

FIG. 2 shows components for determining a temperature field on a stator;

FIG. 3 shows a stator and a rotor of an electric motor;

FIG. 4 shows a stator of an electric motor;

fig. 5a to 5d show the discoloration of a component due to thermochromic discoloration;

these drawings are illustrative. Like reference numerals in the figures refer to like functional and/or structural features.

Detailed Description

Fig. 1 shows a cross-sectional detail of a stator 10 of an electric motor in the form of an outer rotor. The stator 10 has an annular stator back 11 ', from which stator back 11' the stator teeth 11 extend in a star shape in the radial direction R and are distributed uniformly in the circumferential direction U. The stator teeth 11 are each of a T-shaped configuration, such that the outer tooth segments of the stator teeth 11 in the radial direction each adjoin a tooth segment extending in the circumferential direction U, which tooth segment is substantially orthogonal to the tooth segment of the respective stator tooth 11 extending in the radial direction R. A gap for accommodating the stator winding 12 is formed between each two adjacent stator teeth 11.

In the embodiment of the invention shown in fig. 1, this component is designed as an envelope 13, wherein the envelope 13 is arranged in each case in the gap between two adjacent stator teeth 11. The cladding 13 is placed directly on the two stator windings 12 and the stator back 11', wherein the cladding 13 each defines a cavity 17, in which cavity 17 a camera 21 and an illumination means 22 designed as LEDs are arranged. As shown in fig. 2, the camera 21 and the illumination means 22 are preferably arranged at the end of the cavity 17 in the longitudinal direction, so that the component or enclosure 13 can be illuminated over its entire length by the illumination means 22 and captured by the camera 21 by means of imaging technology. The cladding 13 bears against the two stator windings 12 and the stator back 11', so that the surface of the component is essentially divided into three sections. The first section of the cladding lies against the first stator winding 12 'so that the first section 14 of the surface is substantially warmed by the first stator winding 12' and can change color due to the temperature of the first stator winding 12 ', so that the temperature field at the first stator winding 12' can be determined on the first section 14 by the camera 21. The second section of the cladding lies against the stator back 11 ' so that the second section 15 of the surface is substantially warmed by the stator back 11 ' and can change color as a result of the temperature of the stator back 11 ', so that the temperature field of the section of the stator back 11 ' between the first stator winding 12 ' and the second stator winding 12 ″ can be determined on the second section 15 by the camera 21. The third section of the cladding lies against the second stator winding 12 "so that the third section 16 of the surface is substantially warmed by the second stator winding 12" and can change colour due to the temperature of the second stator winding 12 ", so that the temperature field at the second stator winding 12" can be determined on the third section 16 by means of the camera 21.

Fig. 2 shows the cladding 17 of the stator 10 shown in fig. 1 from the viewing direction marked a in fig. 1. On the second section 15 of the surface is arranged an index 18 by means of which the discoloration captured by means of imaging techniques can be assigned to a position on the envelope 17. Alternatively, the landmarks 18 may also be virtually included by the evaluation unit into the image captured by the camera 21. In addition, the index 18 may also be provided on the first section 14 and the third section 16. In addition to the coordinates 18, coordinates 19 are also provided, whereby the color evaluation unit that assigns the temperature has a comparison value directly in the image captured by the camera 21. In fig. 2, the color scale 19 has, for example, only two values. For example, a first temperature limit of 100 ℃ may be assigned to "color" black and a second temperature limit of 60 ℃ may be assigned to "color" white. The second or lowest temperature limit value may preferably correspond to a nominal operating temperature. If the regions in the image captured by the camera have a color equivalent to black, the evaluation unit may determine that the temperature of these regions is at least 100 ℃, and similarly, the temperature of the white regions is at most 60 ℃. If the color gradient of the thermochromic material is linear, there is a color gradation or, in the case of a black-and-white display, a gray scale with temperature, from which gray scale or color gradation the exact temperature and the exact color gradient can be deduced and this can be determined by the evaluation unit.

In addition to the stator 10 as shown in fig. 1, fig. 3 also shows a rotor 30 surrounding the stator 10 in the circumferential direction, which rotor 30 comprises a plurality of magnets 31 and a surrounding sheath 32. The inner surface 33 of the sheath 32 facing the stator is provided with a corner mark which can be captured by imaging techniques through the gaps between the stator teeth 11. The evaluation unit can determine the rotational angle position of the rotor 30 relative to the stator 10 by means of the angle markings captured by the camera 21, wherein this rotational angle position is used, for example, for reducing the starting current, in particular for correctly controlling the electric motor during starting. Additionally, the sheath 32 may also be formed from or coated with a thermochromic material so that the temperature or temperature profile may be determined at the various sections of the rotor 30 captured by the imaging technique.

If, for example, smoke is emitted on the stator 10 or the rotor 30 as a result of overheating, the camera 21 can also capture the smoke by means of imaging technology, so that the evaluation unit can report the smoke to the electric motor controller and, for example, trigger an emergency shutdown. The determined temperature field or the contamination level can also be transmitted to the motor controller and used by it for controlling the motor.

Fig. 4 shows an alternative embodiment of the stator 10 of fig. 1. The gaps between the stator teeth 11 are substantially completely filled by the stator windings 12. The components designed as the cladding 13 are each arranged together with the respective associated camera 21 and the respective associated illumination means 22 between the tooth segments of the stator teeth 11 extending in the circumferential direction U. In this case, the stator windings 12 immediately adjacent in the gap between two stator teeth 11 can directly adjoin one another and can be separated from one another, for example, only by a thin separating layer.

Fig. 5a to 5d show, for example, images 40 of a component captured by a camera at different times. In the image plane below the component, individual heating wires extend along a line 42 for illustrating the thermochromic effect and determining the temperature field. First, in FIG. 5a, the entire surface 41 captured by the imaging technique is free of discoloration. Depending on the temperature limit assigned, the surface has, for example, a temperature of less than 60 ℃. After the heating wire is energized, the evaluation unit evaluates three further images as shown in fig. 5b to 5d at time intervals. The heat emanating from the heating wire heats the component and causes the camera to catch a color change on its surface 41, which color change spreads more and more in the component as can be seen from fig. 5b to 5 d. By means of the color change and the index 45 provided on the surface, the evaluation unit can determine a temperature profile extending from the center of the image (line 42) outwards.

Claims

1. An electric motor comprising components, wherein,

said part being at least partially formed of a thermochromic material or having a surface (14, 15, 16) thereof provided with a coating made of said thermochromic material, and wherein,

the electric motor has a camera (21) configured to capture a surface (14, 15, 16) of the component by an imaging technique, and

the electric motor has an evaluation unit configured to determine a two-dimensional temperature field along the surface (14, 15, 16) from images captured by the camera (21).

2. Electric motor according to the preceding claim, further comprising an illumination means (22) configured to illuminate said surface.

3. The electric motor according to any one of the preceding claims,

the component defines a cavity (17) and the surface (14, 15, 16) captured by the camera is an inner surface of the component facing the cavity.

4. The electric motor of the preceding claim, further comprising

A stator (10) having a plurality of stator windings (12), wherein,

a gap is defined between two immediately adjacent stator windings (12) of the plurality of stator windings (12),

the component is disposed in the gap.

5. The electric motor according to the preceding claim,

the components are configured as a jacket (13) which delimits a cavity (17) and which directly adjoins or is immediately adjacent to the adjacent stator winding (12) with its outer surface facing away from the cavity,

the envelope (13) is formed of the thermochromic material or is coated with the thermochromic material on its inner surface facing the cavity (17),

the illumination means (22) being configured to illuminate the cavity (17) and an inner surface of the envelope (13) facing the cavity (17),

the camera (21) is configured to capture the cavity (17) and an inner surface of the envelope facing the cavity (17) by means of imaging techniques.

6. Electric motor according to the preceding claim, further comprising

A rotor (30) rotatable about the stator (10), wherein,

a cavity (17) defined by the envelope (13) is open in a radial direction (R) towards the rotor (30), and the camera (21) is configured to capture the rotor (30) by means of an imaging technique.

7. The electric motor according to the preceding claim,

an inner surface (33) of the rotor (30) facing the stator (10) is provided with a corner mark surrounding the stator (10) in the circumferential direction (U), which can be captured by the camera (21) and which assigns a relative angular position of a point or segment of the rotor (30) relative to the stator (10).

8. The electric motor according to any one of the preceding claims,

the camera (21) is configured to capture the surface (14, 15, 16) of the component by means of imaging techniques and color, and

the evaluation unit is configured to assign temperature values for the colors in the images of the surfaces (14, 15, 16) captured by the camera (21) and to determine a two-dimensional temperature field along the surfaces (14, 15, 16) of the component from the temperature values assigned to the surfaces (14, 15, 16).

9. The electric motor according to any one of the preceding claims,

the two-dimensional temperature field determined by the evaluation unit is a scalar field in which a temperature value is assigned to each point on the surface (14, 15, 16) of the component captured by the camera (21).

10. The electric motor according to any one of the preceding claims,

the evaluation unit is further configured to determine a surface contamination level and/or a state of the surface (14, 15, 16) or the component from images captured by the camera (21).

11. The electric motor according to any one of the preceding claims,

on said surfaces (14, 15, 16) there are provided color patches (19) resistant to high temperatures, which can be captured by said camera (21) and which assign a specific temperature to a specific color, wherein,

a temperature or temperature limit is assigned to each color.

12. The electric motor according to any one of the preceding claims,

the surfaces (14, 15, 16) are provided with position markers (18) which can be captured by a camera (21) and which assign a specific position value to each point or segment on the surface.

13. A method for detecting a two-dimensional temperature field along a surface (14, 15, 16) of a component, wherein,

said part being at least partially formed of a thermochromic material or having a coating made of said thermochromic material provided on its surface,

said surface (14, 15, 16) being formed of a thermochromic material and changing colour depending on the temperature of a component on said surface (14, 15, 16),

providing a camera (21) which captures a surface (21) of the component and wherein images captured by the camera (14, 15, 16) are transmitted to an evaluation unit,

the evaluation unit assigns temperature values to the colors in the image of the surface (14, 15, 16) and determines a two-dimensional temperature field along the surface (14, 15, 16) of the component from the temperature values assigned to the curved surface (14, 15, 16).

14. A method for detecting a two-dimensional temperature field at a stator winding (12) of an electric motor, wherein components are arranged on the stator winding (12), and wherein,

said element being at least partially formed of a thermochromic material or having a surface (14, 15, 16) thereof provided with a coating made of said thermochromic material,

-providing a camera (21) which captures the surface (14, 15, 16) of the component, and wherein the image captured by the camera (21) is transmitted to an evaluation unit,

the evaluation unit assigns temperature values to the colors in the image of the surface (14, 15, 16) and determines a two-dimensional temperature field along the surface (14, 15, 16) of the component and thus of the stator winding (12) from the temperature values assigned to the curved surface (14, 15, 16).

15. The method according to the preceding claim,

the electric motor comprises a stator (10) having a plurality of stator windings (12), and the component is arranged as a cladding (13) in a gap between two stator windings (12) juxtaposed to each other and directly adjoining or adjoining the juxtaposed stator windings (12), and

the evaluation unit assigns temperature values to the colors in the image of the surface (14, 15, 16) and determines a two-dimensional temperature field along the surface (14, 15, 16) of the component from the temperature values assigned to the surface (14, 15, 16) and thereby determines a two-dimensional temperature field of the respective stator winding (12) for each of two stator windings (12) juxtaposed to one another.