A method for establishing a three-coordinate detection reference system of a frame of a pedal electric motorcycle

Abstract

A kind of establishment method of pedal electric motorcycle frame three-coordinate detection reference system, comprising the following steps: step one: selecting the center point of three circular features as reference point on pedal electric motorcycle frame, the three circular features are front head tube lower end hole, front head tube upper end hole and rear fork left side mounting hole respectively;Step two: the actual coordinate value of the three reference points is measured using three-coordinate measuring machine respectively;Step three: the theoretical coordinate value of the first reference point is completely coincided with actual coordinate value in XYZ three directions;Compared with prior art, by selecting the center point of the center of front head tube lower end hole, the center of front head tube upper end hole and the center of rear fork left side mounting hole three circular features as reference point, the three features are all core geometric dimension related features of frame, can reflect the key position accuracy of frame in actual assembly, so that the reference system established is highly consistent with the actual assembly reference of frame.

Description

Technical Field

[0001] This invention relates to the field of electric motorcycle manufacturing technology, specifically to a method for establishing a three-coordinate measurement reference system for the frame of a scooter electric motorcycle. Background Technology

[0002] All components of a scooter electric motorcycle (referred to as an electric motorcycle) are mounted on the frame. The geometric accuracy of the frame directly affects the feasibility of component installation and the accessibility of the vehicle's functions. Therefore, controlling the geometric accuracy of the frame is of utmost importance.

[0003] The measurement results of the frame geometry depend on the establishment of the measurement reference. Currently, there are two main inspection methods: fixture inspection can only qualitatively determine whether the frame is qualified and cannot output specific deviation values; while coordinate measuring machine (CMM) can output clear deviation directions and values, and is suitable for accuracy analysis and process control.

[0004] In coordinate measuring machine (CMM) measurements, establishing a reference system is a crucial step. Currently, there are two main methods: the first is to establish a reference system by using four centers—the centers of the upper and lower holes of the front tube and the centers of the left and right mounting holes of the rear horizontal fork—through best-fitting; the second is to establish a reference system by using three centers—the center of the upper hole of the front tube, the centers of the left and right mounting holes of the rear horizontal fork, and the centers of the left and right shock-absorbing holes at the tail.

[0005] Chinese Patent Application No. 202320981140.6 discloses a three-coordinate measuring instrument for an electric vehicle frame. The disclosed three-coordinate measuring instrument includes a head tube detection unit, a rear swingarm detection unit, and a rear tail frame detection unit. The head tube detection unit is mounted on a support member via the three-coordinate measuring unit. The three-coordinate measuring unit includes an X-axis displacement adjustment mechanism, a Y-axis displacement adjustment mechanism, and a Z-axis displacement adjustment mechanism, wherein the X, Y, and Z directions are mutually perpendicular. The head tube detection unit can be adjusted relative to the support member in the X, Y, and Z directions via the X, Y, and Z coordinate displacement adjustment mechanisms. The three-coordinate measuring unit also includes coordinate scales for measuring the displacement of the head tube detection unit. Chinese Patent Application No. 202421548748.0 discloses a gauge for detecting the positional accuracy of the head tube portion of a two-wheeled vehicle frame. The disclosed gauge includes a swingarm fixing mechanism and a head tube fixing mechanism mounted on the base plate, as well as a slide rail mechanism and a scale mechanism. Currently, industry gauges can only detect the various mounting points of the head tube, but cannot check the offset of the head tube relative to the swingarm mounting axis. This invention introduces a method of horizontal and vertical guide rails to inspect and measure the head tube portion of the frame, ensuring the symmetry of the head tube portion and providing corresponding data reference for the debugging of frame welding fixtures.

[0006] The establishment of the reference system for existing electric scooter frames in coordinate measuring machine (CMM) measurements mainly suffers from the following technical problems:

[0007] Firstly, existing inspection methods can only qualitatively determine whether the frame is qualified, and cannot output specific deviation values, which makes it difficult to meet the needs of precision analysis and process control.

[0008] Secondly, the commonly used benchmark establishment methods in coordinate measuring machine (CMM) have shortcomings: The first method establishes a benchmark system by best fitting four centers: the center of the upper and lower holes of the front tube, the center of the left and right mounting holes of the rear swingarm, and the center of the top and bottom holes of the front tube. This method introduces four feature points, resulting in too many degree-of-freedom constraints. Furthermore, the best fitting method tends to average out key deviations that should not be averaged in actual assembly, leading to inconsistencies between the measurement benchmark and the actual assembly benchmark of the frame. The second method establishes a benchmark system by three centers: the center of the upper hole of the front tube, the center of the left and right mounting holes of the rear swingarm, and the center of the left and right shock absorber holes of the rear. The benchmark points selected by this method fail to fully reflect the core positioning relationships of the frame during the assembly process. In particular, the key assembly feature of the lower hole of the front tube is not included in the benchmark system, making it difficult for the measurement results to accurately reflect the actual state of the frame in the overall vehicle assembly.

[0009] Third, the existing methods for establishing a coordinate measuring system lack a hierarchical design for the constraints of degrees of freedom. They fail to constrain the degrees of freedom sequentially according to the positioning priority of the frame in actual assembly, resulting in deviations between the measurement datum and the assembly datum, which in turn affects the accuracy of the evaluation of the geometric dimensional deviations of the various measured features of the frame. Summary of the Invention

[0010] The present invention aims to overcome the deficiencies in the prior art and provide a method for establishing a three-coordinate measurement reference system for the frame of a scooter electric motorcycle that can both correlate the core features of the frame and clearly define the magnitude of deviations in each direction.

[0011] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a method for establishing a coordinate measuring machine (CMM) reference system for the frame of a scooter, comprising the following steps:

[0012] Step 1: Select the center points of three circular features on the frame of the electric scooter as reference points. The three circular features are the lower end hole of the front head tube, the upper end hole of the front head tube, and the left side mounting hole of the rear swingarm.

[0013] Step 2: Use a coordinate measuring machine to measure the actual coordinate values ​​of the three reference points respectively;

[0014] Step 3: Make sure the theoretical coordinates and actual coordinates of the first reference point are completely aligned in the X, Y, and Z directions;

[0015] Step 4: Align the theoretical coordinates and actual coordinates of the second reference point in both the X and Y directions;

[0016] Step 5: Align the theoretical coordinates and actual coordinates of the third reference point in the Y direction to complete the establishment of the reference system.

[0017] In a preferred embodiment of the present invention, the first reference point is the center of the lower end hole of the front tube, the second reference point is the center of the upper end hole of the front tube, and the third reference point is the center of the left side mounting hole of the rear horizontal fork.

[0018] As a preferred embodiment of the present invention, in step two, the frame is first fixed firmly before measuring the actual coordinate values ​​of each reference point.

[0019] As a preferred embodiment of the present invention, in step three, the theoretical coordinate value and the actual coordinate value of the first reference point are completely coincident in the three directions of XYZ by the coordinate measuring machine software, so that the deviation of the reference point in the three directions is zero.

[0020] In a preferred embodiment of the present invention, in step four, the theoretical coordinate value and the actual coordinate value of the second reference point are made to coincide in the XY directions by using the coordinate measuring machine software, while the reference point retains a deviation in the Z direction.

[0021] In a preferred embodiment of the present invention, in step five, the theoretical coordinate value and the actual coordinate value of the third reference point are made to coincide in the Y direction by using the coordinate measuring machine software, while the reference point retains deviations in the X and Z directions.

[0022] As a preferred embodiment of the present invention, after the reference system is established, the deviation values ​​of each reference point are displayed in the coordinate measuring machine software, wherein:

[0023] The deviations in all three directions of the first reference point are zero;

[0024] The deviation of the second reference point is (0, 0, △z), where △z is the deviation in the Z direction;

[0025] The deviation of the third reference point is (△x1, 0, △z2), where △x1 is the deviation in the X direction and △z2 is the deviation in the Z direction.

[0026] As a preferred embodiment of the present invention, the center point of the three circular features is a core geometric dimension related feature of the frame, which is used to reflect the critical positional accuracy of the frame in actual assembly.

[0027] As a preferred embodiment of the present invention, the reference system is used for coordinate measuring of the frame of a scooter to evaluate the geometric dimensional deviations of various measured features of the frame.

[0028] As a preferred embodiment of the present invention, the coordinate measuring machine software completes the coincidence operation of the reference point by gradually constraining the degrees of freedom, thereby sequentially realizing the coincidence of the XYZ direction, the XY direction, and the Y direction.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. By selecting the center points of three circular features—the center of the lower end hole of the front head tube, the center of the upper end hole of the front head tube, and the center of the left side mounting hole of the rear swingarm—as reference points, these three features are all core geometric dimension related features of the frame, which can reflect the critical positional accuracy of the frame in actual assembly, so that the established reference system is consistent with the actual assembly reference height of the frame.

[0031] 2. By adopting a stepwise constraint method for degrees of freedom, the first reference point is made to coincide completely in the three directions of XYZ, the second reference point is made to coincide in the two directions of XY, and the third reference point is made to coincide in the Y direction. This hierarchical constraint method matches the positioning sequence and degree of freedom restriction method of the frame in the actual assembly process, avoiding measurement deviations caused by over-constraint or improper constraint.

[0032] 3. After the reference system is established, the deviation values ​​of each reference point can be displayed intuitively: the first reference point has zero deviation in all three directions, the second reference point retains only the Z-direction deviation, and the third reference point retains the X-direction and Z-direction deviations. This deviation display method allows measurement personnel to clearly identify the actual offset state of the frame at key assembly positions, providing accurate data reference for the debugging of frame welding fixtures.

[0033] 4. Compared with the existing technology that uses the best fit of four circles or establishes a reference system by the center of the upper hole of the front tube, the center of the left and right mounting holes of the rear swingarm, and the center of the left and right shock absorber holes of the tail, this method is more in line with the actual assembly process of the electric scooter frame. It can effectively eliminate the deviation between the measurement reference and the assembly reference, improve the accuracy and reliability of the frame geometry measurement, and provide a guarantee for the precise assembly of the whole vehicle parts. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the frame reference point of the present invention;

[0035] Figure 2 This is a schematic diagram of the theoretical coordinate values ​​of the reference point of this invention;

[0036] Figure 3 This is a schematic diagram of the actual coordinate values ​​of the reference point in this invention;

[0037] Figure 4 This is a schematic diagram of the reference point deviation value of the present invention;

[0038] Reference numerals: 1 for the lower end of the front tube, 2 for the upper end of the front tube, and 3 for the left side mounting hole of the rear horizontal fork. Detailed Implementation

[0039] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0040] like Figures 1-4 As shown, a method for establishing a coordinate measuring machine (CMM) reference system for the frame of a scooter includes the following steps:

[0041] Step 1: Select the center points of three circular features on the frame of the electric scooter as reference points. The three circular features are the lower end hole 1 of the front head tube, the upper end hole 2 of the front head tube, and the left side mounting hole 3 of the rear swingarm.

[0042] Step 2: Use a coordinate measuring machine to measure the actual coordinate values ​​of the three reference points respectively;

[0043] Step 3: Make sure the theoretical coordinates and actual coordinates of the first reference point are completely aligned in the X, Y, and Z directions;

[0044] Step 4: Align the theoretical coordinates and actual coordinates of the second reference point in both the X and Y directions;

[0045] Step 5: Align the theoretical coordinates and actual coordinates of the third reference point in the Y direction to complete the establishment of the reference system.

[0046] The first reference point is the center of hole 1 at the lower end of the front tube, the second reference point is the center of hole 2 at the upper end of the front tube, and the third reference point is the center of mounting hole 3 on the left side of the rear swingarm.

[0047] In step two, before measuring the actual coordinates of each reference point, the frame must be securely fixed.

[0048] In step three, the theoretical coordinates and actual coordinates of the first reference point are made to coincide completely in the XYZ directions using the coordinate measuring machine software, so that the deviation of the reference point in the three directions is zero.

[0049] In step four, the theoretical coordinates and actual coordinates of the second reference point are aligned in the X and Y directions using coordinate measuring machine software, while the reference point retains a deviation in the Z direction.

[0050] In step five, the theoretical coordinates of the third reference point are made to coincide with the actual coordinates in the Y direction using the coordinate measuring machine software, while the reference point retains deviations in the X and Z directions.

[0051] After the datum system is established, the deviation values ​​of each datum point are displayed in the coordinate measuring machine software, including:

[0052] The deviations in all three directions of the first reference point are zero;

[0053] The deviation of the second reference point is (0, 0, △z), where △z is the deviation in the Z direction;

[0054] The deviation of the third reference point is (△x1, 0, △z2), where △x1 is the deviation in the X direction and △z2 is the deviation in the Z direction.

[0055] The center point of the three circular features is the core geometric dimension related feature of the frame, which is used to reflect the critical positional accuracy of the frame in actual assembly.

[0056] The reference system is used for coordinate measuring machine (CMM) measurements of the frame of a scooter to evaluate the geometric dimensional deviations of the measured features of the frame.

[0057] The coordinate measuring machine software completes the coincidence operation of the reference point by gradually constraining the degrees of freedom, and sequentially realizes the coincidence of the XYZ direction, XY direction and Y direction.

[0058] Specifically, this invention provides a method for establishing a coordinate measuring machine (CMM) reference system for the frame of a scooter, the method comprising the following steps:

[0059] Step 1: Select a reference point

[0060] Three circular features on the electric scooter frame are selected as reference points at their center points. These three features are: the lower end hole 1 of the head tube, the upper end hole 2 of the head tube, and the left side mounting hole 3 of the rear swingarm. These three features represent the key assembly positions at the front, middle, and rear of the frame, respectively. The center of the upper and lower end holes of the head tube determines the mounting angle and position of the front fork and steering column, serving as the core control point for the accuracy of the front of the frame. The center of the left side mounting hole 3 of the rear swingarm determines the mounting position of the rear swingarm and rear wheel system, serving as the core control point for the accuracy of the rear of the frame. Selecting these three features as reference points ensures a high degree of correlation between the reference system and the actual assembly state of the frame.

[0061] Specifically, the theoretical coordinate values ​​of the three reference points are as follows:

[0062] Center of hole 1 at the lower end of the front tube: A1 (X1, Y1, Z1);

[0063] Center of hole 2 at the upper end of the front tube: B1 (X2, Y2, Z2);

[0064] Center of mounting hole 3 on the left side of the rear swingarm: C1 (X3, Y3, Z3).

[0065] The above theoretical coordinate values ​​are derived from the three-dimensional design model (CAD model) of the chassis and serve as the benchmark reference values ​​for measurement and evaluation.

[0066] Step Two: Fixing and Measuring

[0067] Before performing coordinate measuring machine (CMM) measurements, the chassis to be measured must first be securely fixed. Specialized clamps or universal support devices can be used for fixing, ensuring that the chassis does not shift or vibrate during the measurement process to guarantee the stability and repeatability of the measurement results. Care should be taken to avoid applying additional stress to the chassis during fixing, so as not to affect the true geometry of the chassis.

[0068] After the chassis is fixed, a coordinate measuring machine (CMM) is used to measure the actual coordinate values ​​of the three reference points. The CMM can select either a contact or non-contact probe based on the actual structure of the chassis, fitting the center coordinates of the hole by measuring multiple points on the inner wall of the hole. During the measurement process, it is essential to ensure stable contact between the probe and the hole wall and uniform distribution of sampling points to guarantee fitting accuracy.

[0069] The actual coordinates of the three reference points obtained from the measurement are as follows:

[0070] Center of hole 1 at the lower end of the front tube: A1' (X1', Y1', Z1');

[0071] Center of hole 2 at the upper end of the front tube: B1' (X2', Y2', Z2');

[0072] Center of mounting hole 3 on the left side of the rear swingarm: C1' (X3', Y3', Z3').

[0073] The above actual coordinate values ​​reflect the actual spatial positions of these three key features of the chassis after manufacturing.

[0074] Step 3: Reference Coincidence Operation

[0075] The datum coincidence operation is completed in the coordinate measuring machine software. The goal of this step is to coincide the datum points in the theoretical model with the datum points obtained from actual measurements according to a specific constraint method, thereby establishing a datum system. This invention employs a step-by-step constraint of degrees of freedom method, and the specific operation is as follows:

[0076] Completely align the first reference point: Ensure the theoretical and actual coordinate values ​​of the first reference point are completely aligned in the X, Y, and Z directions. In this invention, the first reference point is the center A1 of the lower end hole 1 of the front tube. Using the "align" or "fit" function in the software, completely align the theoretical coordinates (X1, Y1, Z1) of A1 with the actual measured coordinates (X1', Y1', Z1') in the X, Y, and Z directions. After this operation, the deviation of point A1 in all three directions is zero, meaning this point serves as the first constraint point of the reference system and is completely fixed.

[0077] Partially aligning the second reference point: The theoretical and actual coordinate values ​​of the second reference point are aligned in both the X and Y directions. In this invention, the second reference point is the center B1 of hole 2 at the upper end of the front tube. With A1 fully fixed, software is used to align the theoretical coordinates (X2, Y2, Z2) of B1 with the actual measured coordinates (X2', Y2', Z2') in the X and Y directions, while retaining the deviation in the Z direction. After this operation, the deviation of point B1 is (0, 0, Δz), where Δz = Z2' - Z2, which is the difference between the actual measured value and the theoretical value of point B1 in the Z direction. This difference reflects the relative positional deviation of the centers of the upper and lower holes of the front tube in the Z direction (i.e., the vertical direction), and is of great significance for controlling the fork mounting angle.

[0078] Partially aligning the third reference point: The theoretical and actual coordinate values ​​of the third reference point are aligned in the Y-direction. In this invention, the third reference point is the center C1 of the left mounting hole 3 on the rear swingarm. Based on the first two steps, the theoretical coordinates (X3, Y3, Z3) of C1 are aligned with the actual measured coordinates (X3', Y3', Z3') in the Y-direction using software, while retaining deviations in the X and Z directions. After this operation, the deviation of point C1 is (△x1, 0, △z2), where △x1 = X3' - X3, △z2 = Z3' - Z3, which represents the difference between the actual measured value and the theoretical value of point C1 in the X and Z directions. This deviation reflects the positional deviation of the center of the left mounting hole 3 on the rear swingarm relative to the head tube reference system in the horizontal (X-direction) and vertical (Z-direction) directions, and is of great significance for the installation accuracy of the rear swingarm and rear wheel alignment.

[0079] After completing the above three steps, the three-coordinate measurement reference system of the frame is established. At this point, the theoretical model and actual measurement data in the coordinate measuring machine software have been aligned according to the constraint method of this invention, and all other measured features (such as the right side mounting hole of the rear swingarm, the rear shock absorber hole, the battery compartment mounting point, etc.) can be measured and their deviations evaluated under this reference system.

[0080] Deviation display after the benchmark system is established

[0081] After the datum system is established, the coordinate measuring machine software will display the deviation of each datum point, as follows:

[0082] Point A (center of hole 1 at the lower end of the front tube): The deviations in all three directions are (0, 0, 0), indicating that this point is completely fixed as the first reference.

[0083] Point B (center of hole 2 at the upper end of the front tube): The deviation in three directions is (0, 0, △z), where △z is the deviation in the Z direction, which represents the relative positional deviation of the centers of the upper and lower holes of the front tube in the vertical direction.

[0084] Point C (center of mounting hole 3 on the left side of the rear swingarm): The deviations in three directions are (△x1, 0, △z2), where △x1 is the deviation in the X direction and △z2 is the deviation in the Z direction, representing the deviations of the center of mounting hole 3 on the left side of the rear swingarm relative to the front tube reference system in the horizontal and vertical directions.

[0085] The above deviation values ​​are displayed in an intuitive and clear manner, directly reflecting the actual deviation of the core features of the frame, which facilitates analysis, judgment and improvement by engineering technicians.

[0086] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention; therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0087] Although this document frequently uses reference numerals such as "lower end hole 1 of the front head tube," "upper end hole 2 of the front head tube," and "left side mounting hole 3 of the rear swingarm," the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A method for establishing a coordinate measuring machine (CMM) reference system for the frame of a scooter, characterized in that, Includes the following steps: Step 1: Select the center point of three circular features on the frame of the electric scooter as reference points. The three circular features are the lower end hole (1) of the front tube, the upper end hole (2) of the front tube, and the left side mounting hole (3) of the rear swingarm. Step 2: Use a coordinate measuring machine to measure the actual coordinate values ​​of the three reference points respectively; Step 3: Make sure the theoretical coordinates and actual coordinates of the first reference point are completely aligned in the X, Y, and Z directions; Step 4: Align the theoretical coordinates and actual coordinates of the second reference point in both the X and Y directions; Step 5: Align the theoretical coordinates and actual coordinates of the third reference point in the Y direction to complete the establishment of the reference system.

2. The method for establishing a coordinate measuring machine reference system for the frame of a scooter electric motorcycle according to claim 1, characterized in that, The first reference point is the center of the lower end hole (1) of the front tube, the second reference point is the center of the upper end hole (2) of the front tube, and the third reference point is the center of the left side mounting hole (3) of the rear horizontal fork.

3. The method for establishing a coordinate measuring machine (CMM) reference system for the frame of a scooter according to claim 1, characterized in that, In step two, the frame is first secured before measuring the actual coordinates of each reference point.

4. The method for establishing a coordinate measuring machine reference system for the frame of a scooter electric motorcycle according to claim 1, characterized in that, In step three, the theoretical coordinates and actual coordinates of the first reference point are made to coincide completely in the XYZ directions using the coordinate measuring machine software, so that the deviation of the reference point in the three directions is zero.

5. The method for establishing a coordinate measuring machine reference system for the frame of a scooter electric motorcycle according to claim 1, characterized in that, In step four, the theoretical coordinates and actual coordinates of the second reference point are made to coincide in the XY directions using coordinate measuring machine software, while the reference point retains a deviation in the Z direction.

6. The method for establishing a coordinate measuring machine reference system for the frame of a scooter electric motorcycle according to claim 1, characterized in that, In step five, the theoretical coordinates of the third reference point are made to coincide with the actual coordinates in the Y direction using the coordinate measuring machine software, while the reference point retains deviations in the X and Z directions.

7. The method for establishing a coordinate measuring machine reference system for the frame of a scooter electric motorcycle according to claim 1, characterized in that, After the reference system is established, the deviation values ​​of each reference point are displayed in the coordinate measuring machine software, where: The deviations in all three directions of the first reference point are zero; The deviation of the second reference point is (0, 0, △z), where △z is the deviation in the Z direction; The deviation of the third reference point is (△x1, 0, △z2), where △x1 is the deviation in the X direction and △z2 is the deviation in the Z direction.

8. The method for establishing a coordinate measuring machine reference system for the frame of a scooter electric motorcycle according to claim 1, characterized in that, The center point of the three circular features is a core geometric dimension related feature of the frame, which is used to reflect the critical positional accuracy of the frame in actual assembly.

9. The method for establishing a coordinate measuring machine reference system for the frame of a scooter electric motorcycle according to claim 1, characterized in that, The reference system is used for coordinate measuring of the frame of the electric scooter to evaluate the geometric dimensional deviations of the measured features of the frame.

10. The method for establishing a coordinate measuring machine reference system for the frame of a scooter electric motorcycle according to claim 1, characterized in that, The coordinate measuring machine software completes the coincidence operation of the reference point by gradually constraining the degrees of freedom, and sequentially realizes the coincidence of the XYZ direction, XY direction and Y direction.

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