A reducer end vehicle speed detection mechanism

Abstract

The utility model discloses a kind of reducer end vehicle speed detection mechanisms, it is related to the technical field of automobile driving system, including reduction gear and the circumferentially distributed connecting bolt of being fixed to the reduction gear, the connecting bolt is equipped with multiple and evenly distributed, the protrusion of the connecting bolt is extended along the axial direction of the reduction gear, the protrusion is equipped with gear speed sensor, the gear speed sensor is fixed, the probe of the gear speed sensor is aligned with the rotating plane of the protrusion. The technical problem to be solved by the utility model is to provide a kind of reducer end vehicle speed detection mechanism, significantly improve the compactness of structure, effectively reduce the number of parts, reduce cost and simplify assembly process.

Description

Technical Field

[0001] This utility model relates to the field of automotive drive system technology, specifically to a speed detection mechanism at the reducer end. Background Technology

[0002] In the drive system of new energy vehicles, accurately acquiring vehicle speed signals is crucial for vehicle control (such as energy recovery, cruise control, and instrument display). Traditional vehicle speed sensors typically rely on a dedicated pulse gear (or signal gear ring) to work with the sensor. This pulse gear requires independent machining and installation, occupying additional axial or radial space. This independent structure not only increases the number of parts, manufacturing costs, and assembly complexity, but also faces layout challenges within the increasingly compact electric vehicle axle or gearbox. Utility Model Content

[0003] Technical problem to be solved by the utility model

[0004] The technical problem to be solved by this utility model is to provide a speed detection mechanism at the reducer end, which significantly improves the compactness of the structure, effectively reduces the number of parts, lowers the cost and simplifies the assembly process.

[0005] Technical solution

[0006] To solve the above problems, the technical solution provided by this utility model is as follows:

[0007] A speed detection mechanism for a speed reducer includes a reduction gear and circumferentially distributed connecting bolts fixed to the reduction gear. The connecting bolts are provided in multiple and evenly distributed. Each connecting bolt has a protrusion extending along the axial direction of the reduction gear. A gear speed sensor is provided for each protrusion. The gear speed sensor is fixed, and the probe of the gear speed sensor is aligned with the rotation plane of the protrusion.

[0008] The primary function of the connecting bolt remains mechanical connection, reliably securing the reduction gear to the differential and transmitting power. The protruding structures extending axially from the connecting bolt along the reduction gear are designed to generate pulse signals. These protrusions essentially replace the traditional independent pulse gear (signal gear ring). As the reduction gear (along with the bolt and protrusions) rotates with the differential, these protrusions periodically sweep across the sensor probe, cutting magnetic lines of force and generating pulse signals. The sensor is fixedly mounted on the gearbox housing or drive axle housing, its probe precisely aligned with the plane of rotation of the bolt protrusions. Its function is to non-contactly detect changes in the magnetic field (such as the Hall effect or magnetoresistive effect) generated by the rotation of the bolt protrusions and convert these changes into electrical pulse signals for calculating vehicle speed. By utilizing the existing necessary connecting bolt as the signal source, the independent pulse gear, its mounting base, and fasteners required in traditional solutions are completely eliminated. The signal generation structure (bolt protrusions) is directly integrated into the power transmission path (reduction gear), without occupying additional axial or radial space, significantly improving the space utilization of the entire drive axle / reduction gear area and perfectly addressing the challenge of compact space in electric axles. Reduced components: The pulse gear and related accessories are eliminated entirely, requiring only modification of existing bolts (adding protrusions) or the use of special bolts. Reduced costs: The reduced number of parts eliminates the costs of machining, heat treatment, and separate assembly of independent pulse gears. Simplified assembly: The "installation" of the signal generation structure (bolt protrusion) is completed simultaneously with the fixing of the reduction gear, eliminating the need for separate pulse gear installation steps and accuracy adjustment. The sensor only needs to be fixed and aligned with the rotating plane of the bolt protrusion according to design requirements, greatly simplifying the assembly process.

[0009] Optionally, the gap between the probe of the gear speed sensor and the protruding high point is less than or equal to 4 mm.

[0010] By precisely controlling the distance between the sensor and the signal source, the vehicle speed pulse signal can be detected stably, reliably, and effectively, thus supporting the feasibility, reliability, and signal accuracy of the entire technical solution. The gap (air gap) between the probe and the protruding point is a key parameter determining the rate of change of magnetic field strength (signal strength) and signal stability. An excessively large gap will result in a weak magnetic field change, making reliable detection by the sensor or leading to a low signal-to-noise ratio, making it susceptible to interference and causing vehicle speed signal loss or inaccuracy (such as signal jumps or lost pulses). Conversely, an excessively small gap poses a risk of mechanical interference. The specific value of "less than or equal to 4mm" defines the maximum permissible range of the gap and represents the optimal value range that has been designed and verified.

[0011] Alternatively, the protruding head can be widened or extended into a separate protrusion as a pulse tooth structure.

[0012] The fundamental purpose of both the "widened head" and "extension of a separate protrusion" design methods is to actively create a feature with a significant geometric abrupt change on the bolt. This feature (the widened head or the extended protrusion) is the actual "pulse tooth." When these specially modified bolts rotate at high speed with the reduction gear, their "teeth" (widened head or protrusion) periodically and closely (meeting the ≤4mm gap requirement) pass over the probe of the fixed sensor. Each "teeth" passing the probe causes a significant and repeatable change in the magnetic field (such as a sudden change in magnetic flux), which is detected by the sensor and converted into a clear and stable electrical pulse signal. Multiple evenly distributed bolts form an equivalent pulse gear.

[0013] Optionally, the reduction gear is provided with a reduction gearbox housing, the gear speed sensor is fixed to the reduction gearbox housing, and the reduction gearbox housing is provided with a groove for passing cables.

[0014] As the main structure of the entire reducer, the gearbox housing exhibits significantly higher rigidity and stability than non-main components (such as covers or brackets). Directly and rigidly fixing the sensor to the housing (e.g., with bolts) ensures that the sensor remains firmly in place during vehicle operation (vibration, impact), preventing loosening or displacement. A precise gap of ≤4mm must be maintained between the sensor probe and the highest point of the bolt protrusion. Fixing the sensor to the rigid housing and relating it to machined reference surfaces on the housing (such as mounting holes or locating surfaces) is a prerequisite for achieving and maintaining this critical gap long-term. The machining accuracy of the housing directly determines the accuracy of the sensor's mounting position.

[0015] Optionally, the reduction gear is fixed to the differential by the connecting bolt.

[0016] By tightening the connecting bolts, the reduction gear is rigidly and securely mounted on the differential housing (or related components). This ensures that the power output from the engine / motor, after being reduced and amplified by the reduction gear set, can be efficiently and smoothly transmitted to the differential, and then distributed to the drive wheels on both sides. Without this fundamental structure of bolts securing the reduction gear to the differential, the subsequent function of giving the bolts "pulse gears" would be impossible. The rotational movement and position of the bolt depend entirely on this basic connection task it undertakes as a "fastener." The signal generating device (bolt protrusion) is directly integrated into the existing, necessary transmission path, occupying almost no additional valuable axial or radial space, perfectly meeting the stringent space-constrained requirements of new energy vehicle drive systems. Eliminating the independent pulse gear and its related components directly reduces the number of parts, processing costs, and assembly complexity. The "installation" of the bolt is completed simultaneously with the tightening of the reduction gear.

[0017] Optionally, both ends of the differential are rotatably connected to the gearbox housing via axial limit bearings.

[0018] By mounting these bearings at both ends of the differential housing and securing their outer rings (press-fitted or pre-tightened via end caps) to the gearbox housing, a high-precision, high-rigidity rotational support is provided for the differential assembly (including its internal gears, fixed reduction gears, and connecting bolts serving as pulse teeth). This ensures that the differential can rotate smoothly and with low resistance around its designed axis, efficiently transmitting power to the half-shafts. Axial runout can disrupt the meshing, leading to noise, increased wear, and even failure. Axial limit bearings effectively prevent this harmful axial movement. A precise clearance of ≤4mm must be maintained between the probe of the gear speed sensor and the protruding point of the connecting bolt. If axial runout occurs in the differential (along with its reduction gears and bolts), this critical clearance will change, potentially leading to signal loss (too large clearance) or friction and collision (too small clearance). Axial limit bearings firmly lock the axial position of the differential, providing the fundamental mechanical guarantee for the long-term stability and reliability of this critical clearance.

[0019] Alternatively, the protrusion may be a hexagonal bolt head or a cylindrical structure.

[0020] The rotation creates sufficiently significant geometric abrupt changes. When these protrusions with specific shapes (hexagonal heads or cylinders) sweep past a fixed sensor probe at high speed with the high-speed rotation of the reduction gear: Hexagonal heads: their six edges and planes periodically induce strong, directional magnetic field disturbances (for magnetoelectric sensors) or changes in magnetic flux (for Hall effect sensors), producing clear pulse signal edges. Cylindrical structures: provide a smooth but regular profile. When the sensor probe is fixed, the rotation of the outer edge of the cylinder can also produce periodic, repeatable magnetic field changes (especially when matched with the shape of the sensor probe), similarly generating effective pulse signals. Both forms effectively replace the tooth profile of traditional pulse gears, providing the physical basis for bolts to reliably serve as signal sources.

[0021] Alternatively, the number of connecting bolts may be 5 to 20.

[0022] Too few bolts will result in sparse pulses. At low speeds, the number of pulses per unit time is too small, leading to low vehicle speed signal resolution and slow updates, which may not meet the needs of precise low-speed control (such as creeping and starting) or low-speed energy recovery. Five bolts are equivalent to 5 PPR, providing an acceptable minimum resolution baseline. The sensor and its subsequent processing circuitry have an upper limit on the maximum recognizable pulse frequency. Too many bolts (far exceeding 20) will result in excessively high pulse frequencies at high rotation speeds (corresponding to high vehicle speeds), potentially exceeding the sensor's response limit or the bandwidth of the signal processing circuitry, leading to signal loss or distortion. Bolts need to be evenly distributed along the circumference of the reduction gear. Too many bolts (e.g., more than 20) may result in excessively small bolt spacing within a limited circumferential space. This presents two problems: firstly, it significantly increases manufacturing and assembly difficulty (drilling accuracy, bolt interference); secondly, the sensor probe size is limited, and excessively small bolt spacing may make it difficult for the sensor to clearly distinguish adjacent pulses, especially in the presence of vibration or manufacturing tolerances, easily leading to signal crosstalk or misjudgment.

[0023] Beneficial effects

[0024] Compared with the prior art, the technical solution provided by this utility model has the following advantages:

[0025] The technical solution provided by this utility model cleverly designs the connecting bolt (by adding an axial protrusion) and makes it cooperate with the fixedly installed sensor, thereby realizing the dual functions of fixing and signal generation using existing structural elements (connecting bolts). This highly integrated design fundamentally solves the problems pointed out in the background art, achieving the technical effects of extremely compact structure, significantly reduced number of parts, effective reduction of manufacturing costs, and greatly simplified assembly process. It is an innovative solution to improve the efficiency and integration of vehicle speed detection mechanisms in new energy vehicle drive systems. Attached Figure Description

[0026] Figure 1 A schematic diagram of the structure of a speed detection mechanism at the reducer end, as proposed in an embodiment of this utility model;

[0027] Figure 2 A schematic diagram of the internal structure of a speed detection mechanism at the reducer end, as proposed in an embodiment of this utility model;

[0028] Figure 3 A cross-sectional view of a speed detection mechanism at the reducer end, as proposed in an embodiment of this utility model;

[0029] Figure 4 A partial cross-sectional view of a speed detection mechanism at the reducer end, as proposed in an embodiment of this utility model;

[0030] 1. Input gear; 2. Input shaft; 3. Transmission gear; 4. Transmission shaft; 5. Reduction gear; 6. Differential; 7. Connecting bolt; 701. Protrusion; 8. Gearbox housing; 9. Drive axle housing; 10. Gear speed sensor; 11. Output end; 12. Gearbox bracket; 13. Axial limit bearing. Detailed Implementation

[0031] To further understand the content of this utility model, a detailed description of this utility model will be provided in conjunction with the accompanying drawings and embodiments.

[0032] Example 1

[0033] Combined with appendix Figure 1 A speed detection mechanism for a reducer includes a reduction gear 5 and circumferentially distributed connecting bolts 7 fixed to the reduction gear 5. Multiple connecting bolts 7 are evenly distributed, with the teeth of the reduction gear 5 located on the outermost edge and the connecting bolts 7 positioned inside the teeth. By utilizing the existing connecting bolts 7 as the signal source, the independent pulse gear, its mounting base, and fasteners required in traditional solutions are completely eliminated. The signal generation structure (bolt protrusion 701) is directly integrated into the power transmission path (reduction gear 5), without occupying additional axial or radial space, significantly improving the space utilization of the entire drive axle / reducer area and perfectly addressing the challenge of compact space in electric vehicle axles. Reduced components: The pulse gear and related accessories are directly eliminated, requiring only modification of existing bolts (adding protrusion 701) or the use of special bolts. Reduced costs: The number of parts is reduced, eliminating the costs of machining, heat treatment, and separate assembly of the independent pulse gear. Simplified assembly: The "installation" of the signal generation structure (bolt protrusion 701) is completed simultaneously when fixing the reduction gear 5, eliminating the need for separate pulse gear installation steps and precision adjustment. The sensor only needs to be fixed and aligned with the rotating plane of the bolt protruding 701 according to the design requirements, which greatly simplifies the assembly process.

[0034] Combined with appendix Figure 1 , 2 The gearbox is connected to the transmission gear 3 and the transmission shaft 4. The transmission gear 3 is fixed to the transmission shaft 4 and meshes with the input gear 1. The input gear 1 is fixed to the input shaft 2. The transmission gear 3 meshes with the reduction gear 5. The reduction gear 5 is fixed to the differential 6.

[0035] The reduction gear 5 is surrounded by a reduction gearbox housing 8, and the gear speed sensor 10 is fixed to the reduction gearbox housing 8. The reduction gearbox housing 8 has a slot for cable routing. The reduction gearbox housing 8 is the basic structure that houses and protects the core transmission components, including the reduction gear 5. Its core function is to provide rigid support and precise alignment for the internal gears, bearings, and shafts, forming a relatively sealed space. This sealed space is crucial; it prevents external contaminants (dust, water, oil) from entering, avoiding contamination of the gear meshing surfaces and sensor probes, ensuring transmission efficiency and signal detection accuracy; it also contains lubricating oil, ensuring adequate lubrication of the gears and bearings, reducing wear and noise; and it provides structural rigidity and strength to withstand the forces and torques generated by gear transmission, ensuring stable system operation.

[0036] The reduction gear 5 is fixed to the differential 6 via connecting bolts 7. The differential 6 is used in various vehicles to ensure the vehicle can turn at different angular velocities. Existing differentials 6 mainly consist of a housing, cover, casing, planetary gears, and half-shaft gears. The housing is filled with lubricating oil, and the half-shaft gears are connected to the drive wheels via the output shaft. The reduction gear 5 is typically located in the core area of ​​the drive axle, its position is relatively fixed, and it facilitates the installation of sensors on nearby casings (reduction gearbox casing 8 or drive axle casing 9). The bolts fixed here are naturally positioned where sensors can easily and stably detect the load.

[0037] The number of connecting bolts 7 is 5 to 20. The number of connecting bolts 7 is 5, 15, or 20.

[0038] Combined with appendix Figure 3 , 4 The connecting bolt 7 extends along the axial direction of the reduction gear 5 with a protrusion 701. The protrusion 701 is equipped with a gear speed sensor 10. The gear speed sensor 10 is fixed, and the probe of the gear speed sensor 10 is aligned with the rotation plane of the protrusion 701.

[0039] The gap between the probe of the gear speed sensor 10 and the high point of the protrusion 701 is less than or equal to 4 mm. In this embodiment, the gap can be 1 mm to 3 mm. The working principle of the gear speed sensor 10 (usually a magnetoelectric or Hall effect type) relies on the probe detecting the change in magnetic field (cutting magnetic lines of force) caused by the rotation of the protrusion 701 to generate a pulse signal. The gap (air gap) between the probe and the high point of the protrusion 701 is a key parameter that determines the rate of change of magnetic field strength (signal strength) and signal stability. If the gap is too large, the change in magnetic field will be too weak, the sensor will not be able to detect reliably or the signal-to-noise ratio will be too low, making it susceptible to interference, resulting in loss or inaccuracy of the vehicle speed signal (such as signal jumps or lost pulses). Conversely, if the gap is too small, there is a risk of mechanical interference. The specific value of "less than or equal to 4 mm" limits the maximum allowable range of the gap and is the optimal value range that has been designed and verified. It ensures that as the bolt protrusion 701 rotates at high speed, the sensor probe can stably and clearly capture each change in the magnetic field generated by the protrusion 701 passing by, generating a sufficiently strong and reliable electrical pulse signal to provide high-quality, high-fidelity raw data for subsequent vehicle speed calculations. The clearance requirement (≤4mm) is an important design input and acceptance criterion. At the manufacturing level, it guides the tolerance design of related components (such as the height tolerance of the bolt protrusion 701 and the positional tolerance of the sensor mounting surface). At the assembly level, it requires precise sensor positioning during assembly to ensure that the final position of the probe meets the clearance requirement between it and the highest point of the bolt protrusion 701. This is typically ensured through a well-designed sensor mounting structure (such as locating pins and stops) and assembly processes.

[0040] The 701 bolt head can be widened or extended into a separate protrusion as a pulse tooth structure. "Widened head": This method is relatively simple and can be understood as using a specially made bolt with a larger head diameter (such as a variant of a flange bolt or a custom bolt) to replace the standard bolt. The manufacturing process is relatively mature (forging, machining) and easy to implement. "Extended separate protrusion": This method offers greater design freedom. The protrusion can be a small metal block welded to the bolt head, or it can be a specific shape machined into the bolt head (such as a small cylinder or square).

[0041] The two ends of the differential 6 are rotatably connected to the gearbox housing 8 via axial limit bearings 13. The axial limit bearings 13 are tapered roller bearings. The axial limit bearings 13 form the mechanical spine and precision foundation of the entire drive system (including the innovative vehicle speed detection mechanism). They provide high-precision, high-rigidity rotational support and strict axial positioning for the differential 6; directly ensuring the correct meshing and long-term reliable operation of the gear system; serving as the ultimate mechanical constraint to ensure a constant ≤4mm gap between the vehicle speed sensor probe and the bolt pulse teeth, guaranteeing stable and reliable signal transmission; establishing a stable, low-vibration foundation platform for power transmission and signal detection; supporting the overall high compactness, integration, and modular design of the drive system; and, in conjunction with the sealing structure, maintaining a good lubrication and clean environment within the system.

[0042] The 701 protrusion is a hexagonal head or cylindrical bolt structure. It directly utilizes standard or slightly modified bolt heads as pulse teeth. This is the most direct, lowest-cost, and technologically mature implementation method. Standard hexagonal head bolts are widely used, and their head dimensions are standardized. It maximizes the use of existing parts, eliminating the need for complex bolt modifications; only ensuring that the height of the 701 protrusion meets the requirements after installation (above the gear end face, clearance ≤4mm). This significantly reduces the additional costs and manufacturing complexity of implementing innovative functions, reflecting the simplicity and practicality of the design.

[0043] "Cylindrical Structure": Function: Refers to a cylindrical protrusion specifically extending from the bolt (which can be integrally machined with the hexagonal head or welded / assembled as an additional part). It offers greater design freedom and potentially superior signal performance: the diameter and height of the cylinder can be independently optimized to match the sensitivity and working distance (≤4mm gap) of a specific sensor, potentially resulting in a more stable signal with a higher signal-to-noise ratio. The cylindrical surface can be smoother and more regular, reducing signal fluctuations caused by geometric irregularities (such as wear on the edges of the hexagonal head). It provides an alternative solution for scenarios with limited space or requiring specific signal characteristics.

[0044] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the inventive spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A speed detection mechanism at the reducer end, characterized in that, The device includes a reduction gear and circumferentially distributed connecting bolts fixed to the reduction gear. Multiple connecting bolts are provided and evenly distributed. Each connecting bolt has a protrusion extending along the axial direction of the reduction gear. A gear speed sensor is provided for each protrusion. The gear speed sensor is fixed, and the probe of the gear speed sensor is aligned with the rotation plane of the protrusion.

2. The speed detection mechanism at the reducer end according to claim 1, characterized in that, The gap between the probe of the gear speed sensor and the protruding high point is less than or equal to 4mm.

3. A speed detection mechanism at the reducer end according to claim 1 or 2, characterized in that, The protruding head is widened or extended into a separate protrusion as a pulse tooth structure.

4. The speed detection mechanism at the reducer end according to claim 1, characterized in that, The reduction gear is provided with a reduction gearbox housing, the gear speed sensor is fixed to the reduction gearbox housing, and the reduction gearbox housing is provided with a groove for passing cables.

5. The speed detection mechanism at the reducer end according to claim 1, characterized in that, The reduction gear is fixed to the differential by the connecting bolt.

6. The speed detection mechanism at the reducer end according to claim 5, characterized in that, The two ends of the differential are rotatably connected to the gearbox housing via axial limit bearings.

7. The speed detection mechanism at the reducer end according to claim 1, characterized in that, The protrusion is a hexagonal bolt head or a cylindrical structure.

8. A speed detection mechanism for a reducer end according to any one of claims 1 to 7, characterized in that, The number of connecting bolts is 5 to 20.

Images