A rotational speed measuring device and a gear assembly

Abstract

The application discloses a rotating speed measuring device and a gear assembly, and belongs to the technical field of rotating speed measurement. The rotating speed measuring device comprises a speed measuring wheel and a sensor. The speed measuring wheel is fixed to a rotating speed component to be measured and is provided with a speed measuring hole in the circumferential direction. The sensor is fixed to a static base corresponding to the rotating speed component to be measured. The rotating speed of the rotating speed component to be measured is measured by the relative position change between the speed measuring hole and the sensor when the speed measuring wheel rotates. The rotating speed of the rotating speed component to be measured is measured by installing the speed measuring wheel on the rotating speed component to be measured and by the relative position change between the speed measuring hole and the sensor when the speed measuring wheel rotates. The device has a simple structure, can break through the limitation of the radial space, can avoid directly drilling holes on the rotating speed component to be measured, and improves the safety and the rotating speed measurement efficiency of the rotating speed measuring device.

Description

Technical Field

[0001] This application relates to the fields of speed measurement and gear assembly technology, and in particular, to a speed measuring device and a gear assembly. Background Technology

[0002] Currently, the existing technology for measuring gear speed involves mounting a speed sensor on the engine and directly measuring the gear speed using the sensor. The speed sensor and the gear, made of magnetically conductive material, form a magnetic flux circuit with a gap. When the gear rotates, the change in gap causes the speed sensor coil to sense a change in magnetic flux, thus measuring the gear speed. However, this technology uses radial speed measurement, which typically requires more than 15mm of installation space. Furthermore, if a hole is directly drilled in the gear, the speed sensor can directly measure the change in magnetic flux through the hole to obtain the speed. This can disrupt the original balance, leading to a critical speed resonance hazard in the engine. Moreover, at high speeds, drilling holes in the gear can cause significant tooth deformation, affecting the gear's strength and potentially causing it to break, thus impacting the efficiency of speed measurement. Summary of the Invention

[0003] This application provides a speed measuring device and gear assembly. By installing a speed measuring wheel on the component whose speed is to be measured, and the speed measuring wheel having a speed measuring hole in its circumference, and fixing a sensor on the stationary base corresponding to the component whose speed is to be measured, the speed of the component to be measured is measured by the change in the relative position between the speed measuring wheel and the speed measuring hole of the speed measuring wheel when the speed measuring wheel rotates. The device has a simple structure, can overcome the limitation of radial space, and can avoid directly drilling holes in the component whose speed is to be measured, thereby improving the safety and speed measurement efficiency of the speed measuring device.

[0004] According to one aspect of this application, an embodiment of this application provides a speed measuring device, including: a speed measuring wheel and a sensor; the speed measuring wheel is fixed to the component whose speed is to be measured, and a speed measuring hole is provided along the circumference; The sensor is fixed on the stationary base corresponding to the component whose rotational speed is to be measured, and measures the rotational speed of the component by the change in its relative position to the speed measuring hole when the speed measuring wheel rotates.

[0005] Optionally, the speed measuring wheel is fixed to the component whose rotational speed is to be measured in a non-removable manner.

[0006] Optionally, the non-removable method is a riveted connection.

[0007] Optionally, the number of speed measuring holes is even, and the speed measuring holes are evenly distributed along the circumference of the speed measuring wheel.

[0008] Optionally, the speed measuring hole is circular, and the maximum diameter of the speed measuring hole does not exceed 0.3 times the width of the speed measuring wheel hub.

[0009] Optionally, the speed measuring wheel includes an outer wheel portion and an inner wheel portion; the outer wheel portion and the inner wheel portion are distributed along the axial direction of the speed measuring wheel and have a preset height difference; the speed measuring hole is provided in the outer wheel portion, and there is a gap between the outer wheel portion and the component whose rotational speed is to be measured; the inner wheel portion is fixed to the component whose rotational speed is to be measured.

[0010] Optionally, the sensor is equipped with a coil, and the sensor measures the rotational speed of the component to be measured by changing the magnetic flux of the coil due to the change in the relative position of the speed measuring wheel and the speed measuring hole when the speed measuring wheel rotates.

[0011] Optionally, the speed measuring wheel is made of a magnetic material; when the speed measuring wheel rotates to bring the sensor and the speed measuring hole to their closest point, the speed measuring hole and the sensor are coaxial.

[0012] According to another aspect of this application, an embodiment of this application provides a gear assembly, including a gear section and a speed measuring device; the speed measuring wheel is fixed to the gear section; the sensor is fixed to a stationary base corresponding to the gear section, and measures the speed of the gear section by the change in relative position between the speed measuring wheel and the speed measuring hole when the speed measuring wheel rotates.

[0013] Optionally, the gear part includes a gear body and a bushing; the speed measuring wheel is axially sleeved on the bushing and fixed to the gear body, and the speed measuring wheel is coaxial with the bushing and the gear part.

[0014] This application discloses a speed measuring device, including a speed measuring wheel and a sensor. The speed measuring wheel is fixed to the component whose speed is to be measured and has a speed measuring hole arranged circumferentially. The sensor is fixed on the stationary base corresponding to the component whose speed is to be measured, and measures the speed of the component whose speed is to be measured by the change in the relative position between the speed measuring wheel and the speed measuring hole when the speed measuring wheel rotates. That is, by installing a speed measuring wheel on the component whose speed is to be measured, and measuring the speed of the component whose speed is to be measured by the change in the relative position between the speed measuring wheel and the speed measuring hole when the speed measuring wheel rotates, the device has a simple structure, can overcome the limitation of radial space, and can avoid directly drilling holes in the component whose speed is to be measured, thereby improving the safety and speed measurement efficiency of the speed measuring device.

[0015] Of course, any product implementing this application does not necessarily need to achieve all the advantages described above simultaneously. In addition to the purposes, features, and advantages described above, this application has other purposes, features, and advantages. The application will be further described in detail below with reference to figures. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a front view of an existing speed measuring device; Figure 2 This is a left sectional view of the measuring device according to a preferred embodiment of this application and a front view of the speed measuring wheel; Figure 3 This is a left cross-sectional view of the gear assembly according to a preferred embodiment of this application; Figure 4 This is a front view of the gear section and speed measuring wheel according to a preferred embodiment of this application.

[0017] Legend: 1. Speed ​​measuring wheel; 11. Speed ​​measuring hole; 12. Rivet hole; 13. Speed ​​measuring wheel through hole; 14. Inner wheel part; 15. Transition part; 16. Outer wheel part; 2. Sensor; 3. Gear part; 31. Gear body; 311. Tooth; 312. Spoke; 313. Stop; 314. Gear through hole; 32. Bushing; 4. Rivet. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this application.

[0019] Existing technologies include methods that directly drill holes in gears and measure the change in magnetic flux through the drilled holes to obtain the overall rotational speed of the gear. However, drilling holes directly in gears can disrupt the original balance, especially at high speeds, which can lead to significant gear deformation and breakage, and also results in low safety of the measuring device.

[0020] Furthermore, in conjunction with reference Figure 1 , Figure 1 Another existing speed measurement technology measures the speed of a gear by directly measuring the change in magnetic flux of the gear relative to the speed sensor. However, in this method, the speed sensor and the gear are mounted radially. Radial speed measurement usually requires more than 15mm of installation space, resulting in an excessively large gearbox volume. Furthermore, the large vibration amplitude during radial measurement leads to large signal fluctuations, affecting the accuracy of speed measurement.

[0021] See also Figure 2This application provides a speed measuring device, including a speed measuring wheel 1 and a sensor 2. The speed measuring wheel 1 is fixed to the component whose speed is to be measured and has a speed measuring hole 11 arranged in the circumferential direction. The sensor 2 is fixed on the stationary base corresponding to the component whose speed is to be measured, and measures the speed of the component whose speed is to be measured by the change in relative position between the speed measuring wheel 1 and the speed measuring hole 11 when the speed measuring wheel 1 rotates.

[0022] It should be noted that the speed measuring device of this application can be used to measure the speed of gears, that is, the component whose speed is to be measured is a gear. It can also be used for speed measurement needs of other similar structures, such as the component whose speed is to be measured can be a sprocket, pulley, etc. The following embodiments are described in detail for measuring the speed of gears.

[0023] In this embodiment, the speed measuring wheel 1 is fixed to the component whose rotational speed is to be measured, and the sensor 2 is fixed to the stationary base corresponding to the component whose rotational speed is to be measured. The stationary base can be a stationary base for mounting the component whose rotational speed is to be measured, or a specially designed stationary mounting component. The sensor 2 is fixed axially to the component whose rotational speed is to be measured, meaning that the measuring surface of the sensor 2 after axial mounting is parallel to the axial direction of the component whose rotational speed is to be measured. Axial mounting can overcome radial space limitations, effectively saving mounting box space under the premise of compact mounting box space. Furthermore, the vibration amplitude of axial vibration is only 1 / 5 to 1 / 3 of that of radial vibration, avoiding signal fluctuations caused by radial vibration of the component whose rotational speed is to be measured. Further, the speed measuring holes 11 are evenly distributed along the circumference of the speed measuring wheel 1, and the measuring surface of the speed sensor 2 is located directly in front of the speed measuring holes 11, i.e., the axially mounted sensor 2... The center of the measuring surface is aligned with the axis of one of the speed measuring holes 11. When the speed measuring wheel 1 rotates, the rotational speed of the component to be measured is measured by the relative position change between the measuring surface of the sensor 2 and the speed measuring hole 11. The rotational speed can be calculated by measuring the change in magnetic flux of the speed measuring hole 11 relative to the sensor 2, or by measuring the periodic position change of the speed measuring hole 11 relative to the sensor 2. This embodiment does not limit the method of calculating the rotational speed. In this embodiment, when the speed measuring wheel 1 rotates, the speed measuring hole 11 changes the magnetic flux of the speed measuring wheel 1 measured by the sensor 2. Therefore, the sensor 2 measures the change in magnetic flux of the speed measuring wheel 1 by measuring the relative position change of the speed measuring wheel 1 with the speed measuring hole 11, and the rotational speed of the speed measuring wheel 1 is obtained based on the change in magnetic flux. Since the speed measuring wheel 1 rotates coaxially with the component to be measured, the rotational speed of the speed measuring wheel 1 is the same as the rotational speed of the component to be measured.

[0024] Preferably, the speed measuring wheel 1 is fixed to the component whose rotational speed is to be measured in a non-removable manner. It should be noted that the speed measuring wheel 1 can also be fixed to the component whose rotational speed is to be measured by welding, bonding or other methods.

[0025] Preferably, the non-removable method is a riveted connection, as described in the reference. Figure 2 and Figure 3 In this embodiment, the speed measuring wheel 1 includes rivet holes 12. The rivet holes 12 are evenly distributed around the circumference of the speed measuring wheel 1. The distance between the rivet holes 12 and the axis of the speed measuring wheel 1 is smaller than that between the speed measuring hole 11 and the axis of the speed measuring wheel 1. In this embodiment, the speed measuring wheel 1 is fixed to the component whose rotational speed is to be measured by stamping and riveting the rivet 4 in the rivet holes 12.

[0026] Furthermore, the number of speed measuring holes is even, and the speed measuring holes are evenly distributed along the circumference of the speed measuring wheel. This avoids unbalanced forces induced by the asymmetry and uneven distribution of the number of speed measuring holes, which would affect the accuracy of the rotational speed measurement. Since the presence of the speed measuring wheel objectively increases the load on the component whose rotational speed is to be measured, in order to minimize this adverse effect, this embodiment reduces the thickness of the speed measuring wheel disc without affecting the strength of the speed measuring wheel. The number of speed measuring holes is optimized based on the material of the speed measuring wheel, the rotational speed of the speed measuring wheel, and the magnitude of the centrifugal force. This optimizes the number and structural design of the speed measuring holes to achieve both a reduction in the mass of the speed measuring wheel and no impact on its strength.

[0027] Preferably, the speed measuring hole 11 is circular, and the maximum diameter of the speed measuring hole 11 does not exceed 0.3 times the width of the hub of the speed measuring wheel 1. It should be noted that if the diameter of the speed measuring hole 11 is too large, it will weaken the strength of the hub, causing plastic deformation or even breakage under the centrifugal force generated by high-speed rotation. If the diameter is too small, it may not be possible to effectively reduce the weight of the speed measuring wheel 1 to achieve a lightweight design. Furthermore, if the speed measuring hole 11 is triangular or rectangular, it will reduce stress concentration and affect the safety of the device. Therefore, in this embodiment, the speed measuring hole 11 is circular, and the maximum diameter of the speed measuring hole 11 does not exceed 0.3 times the width of the hub of the speed measuring wheel 1, so as to ensure the lightweight and safety of the speed measuring device of this application.

[0028] Furthermore, the speed measuring wheel 1 includes an outer wheel portion 16 and an inner wheel portion 14. The outer wheel portion 16 and the inner wheel portion 14 are distributed along the axial direction of the speed measuring wheel 1 and have a preset height difference. The speed measuring hole 11 is provided in the outer wheel portion 16, and there is a gap between the outer wheel portion 16 and the component whose rotational speed is to be measured. The inner wheel portion 14 is fixed to the component whose rotational speed is to be measured.

[0029] See also Figure 2In this embodiment, the speed measuring wheel 1 includes a speed measuring wheel through hole 13, a rivet hole 12, an outer wheel portion 16, and an inner wheel portion 14. The outer wheel portion 16 is located at the outer edge of the speed measuring wheel 1, and the inner wheel portion 14 is located at the inner edge of the speed measuring wheel 1. The outer wheel portion 16 and the inner wheel portion 14 are coaxial. The distance between the outer wheel portion 16 and the axis of the speed measuring wheel 1 is greater than the distance between the inner wheel portion 14 and the axis of the speed measuring wheel 1 (that is, the distance between the outer wheel portion 16 and the center of the speed measuring wheel through hole 13 is greater than the distance between the inner wheel portion 14 and the center of the speed measuring wheel through hole 13). Furthermore, the test wheel has a cantilever structure, meaning that the outer wheel portion 16 and the inner wheel portion 14 are connected by a transition portion 15. Therefore, there is a preset height difference between the outer wheel portion 16 and the inner wheel portion 14, and the height between the upper surface of the outer wheel portion 16 and the bottom surface of the speed measuring wheel 1 is greater than the height between the inner wheel portion 14 and the bottom surface of the speed measuring wheel 1. After the speed measuring wheel 1 is installed, its inner wheel portion 14 is in close contact with the component whose rotational speed is to be measured, that is, the working surface of the inner wheel portion 14 is in contact with the working surface of the component whose rotational speed is to be measured, while the outer wheel portion 16 is separated from the component whose rotational speed is to be measured, that is, there is a gap between the outer wheel portion 16 and the component whose rotational speed is to be measured. This can effectively reduce aerodynamic interference during high-speed rotation, improve the signal-to-noise ratio of the signal generated by the sensor 2, and improve measurement accuracy. Moreover, in the aviation working environment, the working temperature of the component whose rotational speed is to be measured can reach more than 300 degrees Celsius. The cantilever structure of the speed measuring wheel 1 can effectively block heat transfer from the component whose rotational speed is to be measured to the speed measuring wheel 1. The speed measuring wheel 1 and the component whose rotational speed is to be measured can expand separately, thereby protecting the speed measuring wheel 1 and improving the safety of the measuring device. Furthermore, the speed measuring holes 11 are evenly distributed along the circumference of the outer wheel portion 16, and the rivet holes 12 are evenly distributed along the circumference of the inner portion. Therefore, the speed measuring wheel 1 is fixed to the component whose rotational speed is to be measured through the inner wheel portion 14, and there is no obstruction between the component whose rotational speed is to be measured and the outer wheel portion 16. There is also no obstruction between the measuring surface of the sensor 2 and the outer wheel portion 16, which facilitates the sensor 2 to accurately measure the rotational speed of the component whose rotational speed is to be measured.

[0030] Preferably, the sensor 2 is provided with a coil, and the sensor 2 measures the rotational speed of the component to be measured by changing the magnetic flux of the coil due to the change in the relative position between the speed measuring wheel 1 and the speed measuring hole 11 when the speed measuring wheel 1 rotates.

[0031] In this embodiment, a speed measuring wheel 1 replaces the component whose rotational speed is to be measured, forming a magnetic flux circuit with a sensor 2. The sensor 2 has a coil. When the speed measuring wheel 1 rotates, the coil of the sensor 2 senses a change in magnetic flux. When the speed measuring hole 11 on the speed measuring wheel rotates to the measuring surface of the sensor 2, because the speed measuring hole 11 is hollow, the air path becomes longer and the gap larger, resulting in higher magnetic reluctance. At this time, the magnetic flux sensed by the coil of the sensor 2 is small. When the speed measuring hole 11 is aligned with the measuring surface of the sensor 2, because the gap between the speed measuring holes 11 is solid, the gap is small, and the magnetic flux sensed by the coil of the sensor 2 is large, thus generating an induced electromotive force E based on the rate of change of magnetic flux. The frequency of this induced electromotive force is also equal to the magnitude of the rate of change of magnetic flux. The sensor 2 measures the periodic changes of the speed measuring wheel 1, converts them into an electrical signal, and the frequency of the signal is proportional to the rotational speed. The rotational speed value is then calculated through circuitry or algorithms. The calculation formula is n=60f / N, where n is the rotational speed, f is the frequency of the sine wave signal, and N is the number of speed measuring holes 11 on the speed measuring wheel 1.

[0032] Preferably, the speed measuring wheel 1 is made of magnetic material. When the speed measuring wheel 1 rotates so that the sensor 2 is closest to the speed measuring hole 11, the speed measuring hole 11 and the sensor 2 are coaxial. After the sensor 2 is installed, the sensor 2 and the speed measuring wheel 1 made of magnetic material form a magnetic flux circuit with a gap. When the speed measuring wheel 1 rotates, the change in gap causes the coil of the sensor 2 to sense a change in magnetic flux. The rotational speed of the speed measuring wheel 1 is obtained according to the rate of change of magnetic flux, and then the rotational speed of the component to be measured is obtained. Among them, sensor 2 has a circumferentially symmetrical structure. Therefore, when the speed measuring wheel 1 rotates to make the sensor 2 closest to the speed measuring hole 11, the speed measuring hole 11 and sensor 2 are coaxial. If the sensor 2 and speed measuring hole 11 are not coaxial at this time, the change of magnetic flux will gradually decrease to the minimum value, rather than decreasing to the minimum value instantaneously. When the subsequent circuit judges the precise moment of the rising or falling edge of the electrical signal, there will be time uncertainty, that is, signal jitter, which will affect the accuracy of the rotational speed value. The coaxial design ensures that when the change of magnetic flux reaches the extreme value, its rate of change is symmetrical and the polarity is instantly reversed. This makes the time point corresponding to each edge of the electrical signal (the jump point from high to low or from low to high) very accurate. The rotational speed value calculated based on this electrical signal is more stable and more accurate.

[0033] See also Figure 3 and Figure 4 This application also proposes a gear assembly, including a gear part 3 and the aforementioned speed measuring device. The speed measuring wheel 1 is fixed to the gear part 3, and the sensor 2 is fixed to the stationary base corresponding to the gear part 3. The speed of the gear part 3 is measured by the change in the relative position between the speed measuring wheel 1 and the speed measuring hole 11 when the speed measuring wheel 1 rotates. The gear part 3 includes a gear body 31 and a bushing 32.

[0034] It should be noted that the gear part 3 is composed of a gear body 31 and a bushing 32. The gear body 31 includes teeth 311, spokes 312, a stop 313, and a gear through hole 314. The teeth 311 are located on the outer edge of the gear body 31. The spokes 312 are close to the teeth 311 and have an annular structure. The distance between the outermost edge of the teeth 311 and the center of the gear through hole 314 is greater than the distance between the outermost edge of the spokes 312 and the center of the gear through hole 314. The stop 313 is an annular boss structure located between the spokes 312 and the gear through hole 314. The distance between the stop 313 and the center of the gear through hole 314 is less than the distance between the outermost edge of the spokes 312 and the center of the gear through hole 314. The stop 313 is used to position the speed measuring wheel 1. The inner wheel portion 14 of the speed measuring wheel 1 is fixed to the spoke plate 312 of the gear body 31 by rivets 4. The outer wheel portion 16 of the speed measuring wheel 1 is separated from the gear body 31, that is, there is a gap between the outer wheel portion 16 and the spoke plate 312, so as to effectively improve the signal-to-noise ratio of the electrical signal and block the heat transfer from the gear body 31 to the speed measuring wheel 1, thereby improving the safety of the speed measuring device. At the same time, the sensor 2 is fixed on the stationary base corresponding to the gear portion 3, and measures the speed of the speed measuring wheel 1 by the change in its relative position with the speed measuring hole 11 when the speed measuring wheel 1 rotates. The speed of the speed measuring wheel 1 is the same as the speed of the gear body 31. The stationary base can be a stationary base for mounting the gear portion 3, or a specially set stationary mounting component.

[0035] Furthermore, the speed measuring wheel 1 is axially sleeved on the bushing 32 and fixed to the gear body 31. The speed measuring wheel 1, bushing 32, and gear 3 are coaxial. That is, the sensor 2 is fixed on the axial direction of the gear body 31. The speed measuring wheel 1, bushing 32, and gear 3 are coaxial. The measuring surface of the sensor 2 is parallel to the axial direction of the gear 3. By axially installing, the radial space limitation is overcome, effectively saving gearbox space and avoiding strong signal fluctuations caused by strong radial vibration of the gear, thus improving the speed measurement accuracy.

[0036] The gear assembly of this application measures the rotational speed of the gear part 3 through a rotational speed measuring device. It has a simple structure and can overcome the limitation of radial space by axial installation, saving radial space of the gearbox, improving the lightweight nature of the gear assembly, and avoiding direct drilling of the gear body 31, thereby improving the safety and measurement efficiency of the rotational speed measuring device.

[0037] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0038] This document uses specific examples to illustrate the principles and implementation methods of this application. The examples are merely for the purpose of helping to understand the method and core ideas of this application. The above descriptions are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, and the existence of an infinite number of specific structures, those skilled in the art can make various improvements, modifications, or variations without departing from the principles of this application, and can also combine the above technical features in an appropriate manner. These improvements, modifications, variations, or combinations, or the direct application of the utility model concept and technical solution to other situations without modification, should all be considered as protected by this application.

Claims

1. A speed measuring device, characterized in that, Includes speed measuring wheel and sensor; The speed measuring wheel is fixed to the component whose rotational speed is to be measured, and a speed measuring hole is provided along the circumference; the speed measuring hole is circular. The speed measuring wheel has a cantilever structure and includes an outer wheel part and an inner wheel part; The outer wheel and the inner wheel are distributed along the axial direction of the speed measuring wheel and have a preset height difference; The height between the upper surface of the outer wheel and the bottom surface of the speed measuring wheel is greater than the height between the inner wheel and the bottom surface of the speed measuring wheel; The sensor is fixed on the stationary base corresponding to the component whose rotational speed is to be measured, and measures the rotational speed of the component by the change in its relative position with the speed measuring hole when the speed measuring wheel rotates.

2. The rotational speed measuring device according to claim 1, characterized in that, The speed measuring wheel is fixed to the component whose rotational speed is to be measured in a non-removable manner.

3. The rotational speed measuring device according to claim 2, characterized in that, The non-removable type is a riveted connection.

4. The measuring device according to claim 1, characterized in that, The number of speed measuring holes is even, and the speed measuring holes are evenly distributed along the circumference of the speed measuring wheel.

5. The measuring device according to claim 1, characterized in that, The maximum diameter of the speed measuring hole does not exceed 0.3 times the width of the speed measuring wheel hub.

6. The measuring device according to claim 1, characterized in that, The speed measuring hole is located on the outer wheel portion, and there is a gap between the outer wheel portion and the component whose rotational speed is to be measured; The inner wheel is fixed to the component whose rotational speed is to be measured.

7. The measuring device according to claim 1, characterized in that, The sensor is equipped with a coil, and the sensor measures the rotational speed of the component to be measured by changing the magnetic flux of the coil as the speed measuring wheel rotates and its relative position to the speed measuring hole changes.

8. The measuring device according to claim 7, characterized in that, The speed measuring wheel is made of magnetically conductive material; When the speed measuring wheel rotates to bring the sensor and the speed measuring hole closest, the speed measuring hole and the sensor are coaxial.

9. A gear assembly, characterized in that, Includes gears and a speed measuring device; The rotational speed measuring device is the measuring device as described in any one of claims 1-8; The speed measuring wheel is fixed to the gear section; The sensor is fixed on the stationary base corresponding to the gear section, and measures the rotational speed of the gear section by the change in its relative position with the speed measuring hole when the speed measuring wheel rotates.

10. The gear assembly according to claim 9, characterized in that, The gear section includes a gear body and a bushing; The speed measuring wheel is axially sleeved on the bushing and fixed to the gear body, and the speed measuring wheel is coaxial with the bushing and the gear body.

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