A three-dimensional contact force measuring device

Abstract

This invention relates to a three-dimensional contact force measuring device, belonging to the field of electronic measuring instrument manufacturing technology, and solves the problem that the contact force level has a significant impact on the contact force measurement error in existing technologies. The invention includes a mounting base, a friction block base, a friction block, three force transmission structures, and three force sensor bases. The mounting base has a mounting plane. The friction block base includes a platform portion and three support rod portions. The platform portion is parallel to the mounting plane and spaced apart. The central axes of the three support rod portions are orthogonal to each other and are fixedly connected to the mounting plane of the mounting base through the force transmission structures and force sensor bases. The friction block is disposed on the platform portion of the friction block base. The force transmission structure includes a force transmission shaft, and the transverse bending stiffness K of the force transmission shaft is... b Less than or equal to axial tensile / compressive stiffness K p 1%. This invention avoids the influence of contact force level on contact force measurement error by using a specific arrangement of friction blocks and force transmission structures.

Description

Technical Field

[0001] This invention belongs to the field of electronic measuring instrument manufacturing technology, specifically relating to a three-dimensional contact force measuring device. Background Art

[0002] For the crown or shoulder structure of aero-engine turbine blades employing friction damping, contact force measurements are needed to obtain contact surface parameters and reveal mechanical properties. Contact force measurements are often two-dimensional or three-dimensional, leading to inter-dimensional coupling effects between different force directions, making the measurement of high-dimensional contact forces difficult and prone to large deviations. Resonance of the force-measuring structure has a significant impact on the measurement results. In frictional contact force measurements, the contact surfaces are a pair of friction pairs, where the measured contact surface is the moving part of the friction pair, while the stationary part of the friction pair is connected to the force-measuring device. Therefore, the force-measuring device must provide sufficient system stiffness for the stationary part of the friction pair.

[0003] Resonance in the force-measuring structure will increase structural deformation, distorting the force sensor's measurement results. Contact force measurement is often accompanied by the determination of hysteresis loops. Measuring the hysteresis loops of the contact surface requires accurate measurement of both contact force and relative displacement. Resonance in the force-measuring structure will affect the measurement of relative displacement.

[0004] Current measurement solutions typically employ commercially available multidimensional force measuring elements or mechanically decoupled force measuring structures. Commercial force measuring elements often prioritize versatility, thus lacking applicability to specific application scenarios. For mechanical force measuring structures, due to the coupling between the force transmission structures in the three directions, when a contact force transmits a load in a certain direction, in addition to the axial load borne by the force transmission structure in that direction, the lateral load in the other two orthogonal directions also bears a portion of the load. This results in the axial load of the force transmission structure in that direction being lower than the actual load, and this inter-dimensional coupling effect leads to measurement errors. To address this issue, existing mechanical force measuring structure solutions employ mechanical decoupling, relaxing the degrees of freedom in the force measuring direction other than the axial direction to reduce the coupling effect between different directions. However, this solution is currently often used in large-scale structures such as aircraft landing gear and does not consider structural stiffness, resulting in low structural stiffness and susceptibility to resonance.

[0005] For contact force measurements on small-sized contact surfaces, the force measuring structure needs to have a small size to ensure accessibility for measuring the contact surfaces of dry friction damping structures such as blade crowns or shoulders. The force measuring structure also needs to have high system stiffness. High stiffness can increase the natural frequency to avoid measurement errors caused by resonance, while ensuring that the structural response is much smaller than that of the object being measured, reducing measurement errors related to the relative displacement between the contact surfaces. Summary of the Invention

[0006] Based on the above analysis, the present invention aims to provide a three-dimensional contact force measuring device to solve the problems of inter-dimensional coupling of force and the large influence of contact force level on contact force measurement error in existing multi-dimensional contact force measurement schemes.

[0007] The present invention adopts the following technical solution:

[0008] A three-dimensional contact force measuring device includes a mounting base, a friction block base, a friction block, three force transmission structures, and three force sensor bases. The mounting base has a mounting plane. The friction block base includes a platform portion and three support rod portions. The platform portion is parallel to the mounting plane and spaced apart. The three support rod portions extend outward from the edge of the platform portion. The central axes of the three support rod portions are orthogonal to each other, and their intersection point is located at the center of the platform portion. One end of each of the three force transmission structures is fixedly connected to one of the three support rod portions of the friction block base and extends along the direction of the corresponding central axis of the support rod portion. The other end of each of the three force transmission structures is fixedly connected to one of the three force sensor bases. Each of the three force sensor bases is independently fixedly mounted on the mounting plane of the mounting base. The friction block is disposed on the platform portion of the friction block base on the side away from the mounting base. Each force transmission structure includes a force transmission shaft with a lateral bending stiffness K. b Less than or equal to axial tensile / compressive stiffness K p 1%.

[0009] Furthermore, the three force transmission structures are arranged according to a first rectangular coordinate system (x1-y1-z1), and the three force transmission structures extend along the x1, y1, and z1 directions respectively; the first rectangular coordinate system (x1-y1-z1) and the second rectangular coordinate system (x2-y2-z2) with the mounting plane as the y2-z2 plane and the mounting plane normal as the x2 direction have the following linear transformation relationship:

[0010]

[0011]

[0012] Furthermore, the force transmission shaft is a hollow shaft structure, and the force transmission shaft is divided into a first part, a second part and a third part along the axial direction; the first end of the first part is fixedly connected to one of the three support rods of the friction block base, the first end of the second part is fixedly connected to the second end of the first part, and the second end of the second part is fixedly connected to the first end of the third part.

[0013] Furthermore, each of the force transmission structures also includes a force sensor adapter disk and a force sensor. The second end of the third part of the force transmission shaft is fixedly connected to the force sensor adapter disk, the force sensor adapter disk is fixedly connected to the force sensor, and the force sensor is fixedly connected to the force sensor base.

[0014] Furthermore, the outer diameter of the first part is the same as that of the second part and smaller than that of the third part, and the inner diameter of the second part is the same as that of the third part and larger than that of the first part.

[0015] Furthermore, the second part of the force transmission shaft consists of multiple circumferentially distributed ribs.

[0016] Furthermore, the cross-section of the rib is fan-shaped, trapezoidal, rectangular, or circular.

[0017] Furthermore, the mounting base is an irregularly shaped flat plate, on which multiple bolt holes and three first flat keyways are provided. The multiple bolt holes are evenly arranged at the periphery of the mounting base, and the three first flat keyways are arranged in the middle of the upper surface of the mounting base. The central axes of the three first flat keyways intersect at a point, and the three central axes form a 120° angle with each other.

[0018] Furthermore, the force sensor base is a block shape with an inclined mounting surface, the end of the force sensor is fixedly connected to the inclined mounting surface, and the force sensor is perpendicular to the inclined mounting surface.

[0019] On the other hand, the present invention also relates to a method for measuring the three-dimensional contact force of an aero-engine turbine blade, using a three-dimensional contact force measuring device as described above.

[0020] This invention has at least one of the following beneficial effects:

[0021] (1) The present invention uses a force transmission shaft as a flexible hinge, which effectively reduces the force-dimensional coupling effect of contact force measurement.

[0022] (2) The present invention measures the contact force by using a force transmission structure arranged orthogonally in three directions according to the first rectangular coordinate system, and defines the working coordinate system of the friction block using the second rectangular coordinate system. By utilizing the transformation relationship between the coordinate systems, the measurement result of the contact force in the second rectangular coordinate system is obtained, which effectively avoids the influence of the contact force level on the contact force measurement error, and makes the force measurement error only related to the decoupling degree of the force transmission axis.

[0023] (3) The present invention controls the decoupling degree and structural stiffness of the force transmission shaft by controlling the design parameters of the force transmission shaft ribs, so as to ensure that the structure has sufficient stiffness to avoid resonance.

[0024] (4) This invention reduces the force-dimensional coupling effect of the contact force measuring device and improves the system stiffness from the aspects of force transmission shaft design, coordinate system transformation and force measuring structure scheme, thereby improving the contact force measurement accuracy and providing stiffness guarantee for the measurement of relative displacement of hysteresis loop.

[0025] (5) The present invention provides a three-dimensional contact force measuring device, which uses a force transmission shaft as a flexible hinge and combines coordinate system transformation to ensure measurement accuracy and reduce the coupling effect between force dimensions. The friction block base is extended through three orthogonal force transmission structures, and the system stiffness is ensured through the parameter design of the force transmission shaft.

[0026] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0027] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0028] Figure 1 This is a schematic diagram of the structure of a three-dimensional contact force measuring device according to the present invention;

[0029] Figure 2 This is a top view of a three-dimensional contact force measuring device according to the present invention;

[0030] Figure 3 For along Figure 2 The cross-sectional view of line AA is a cross-sectional view of a three-dimensional contact force measuring device.

[0031] Figure 4 This is a top view of the friction block base;

[0032] Figure 5 For along Figure 4 The cross-sectional view along line BB is a cross-sectional view of the friction block base;

[0033] Figure 6 Top view of the mounting base;

[0034] Figure 7 This is a structural diagram of the force sensor base;

[0035] Figure 8 This is a schematic diagram of the force transmission shaft in Embodiment 1 of the present invention;

[0036] Figure 9 for Figure 8 Front view of the central force transmission shaft;

[0037] Figure 10 For along Figure 9 The cross-sectional view of the CC line is a cross-sectional view of the force transmission shaft;

[0038] Figure 11 For along Figure 9 The sectional view of the DD line is a sectional view of the force transmission shaft;

[0039] Figure 12 This is a structural diagram of the force transmission shaft in Embodiment 2 of the present invention;

[0040] Figure 13 This is a side view of the force transmission shaft in Embodiment 2 of the present invention;

[0041] Figure 14 For along Figure 13 Sectional view of the middle EE line;

[0042] Figure 15 For along Figure 13 A cross-sectional view of the FF line.

[0043] In the diagram: 1-Mounting base; 11-Mounting plane; 111-First keyway; 112-Bolt hole; 2-Friction block base; 21-Platform section; 211-Friction block mounting groove; 212-Central through hole; 22-Support rod section; 221-First screw hole; 3-Friction block; 4-Force transmission structure; 41, 41'-Force transmission shaft; 411, 411'-First part; 412, 412'-Second part; 4121, 4121'-Rib; 413, 413'-Third part; 4131, 4131'-Mounting through hole; 42-Force sensor adapter plate; 43-Force sensor; 5-Force sensor base; 51-Mounting inclined surface; 52-Inclined threaded hole; 53-Second keyway; 54-Counterhead hole; 6-Front key; 7-Double-ended screw. Detailed Implementation

[0044] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0045] Example 1

[0046] A specific embodiment of the present invention, such as Figure 1 , Figure 2 and Figure 3 As shown, a three-dimensional contact force measuring device includes a mounting base 1, a friction block base 2, a friction block 3, three force transmission structures 4, and three force sensor bases 5.

[0047] Among them, such as Figure 1 , Figure 2 and Figure 6 As shown, the mounting base 1 is preferably a flat plate structure with a mounting plane 11 for mounting three force sensor bases 5. The mounting base 1 can be a simple rectangle or, as shown, a flat plate structure with a mounting surface 11 for mounting three force sensor bases 5. Figure 1 , Figure 2 and Figure 6 The irregular shape shown can also be other shapes that fit the required installation location. Three first flat keyways 111 and multiple bolt holes 112 are provided on the mounting plane 11 of the mounting base 1.

[0048] Multiple bolt holes 112 are through holes, evenly distributed around the periphery of the mounting base 1, for easy placement of the mounting base 1 in the desired position. A sliding groove is also provided on the bottom surface of the mounting base 1 to facilitate adjustment of its position.

[0049] Three first flat keyways 111 are arranged in the middle of the upper surface of the mounting base 1, and the central axes of the three first flat keyways 111 intersect at a single point, with the three central axes forming a 120° angle with each other. The three first flat keyways 111 are equal in size and identical in shape, and the line connecting their endpoints near the center forms an equilateral triangle. The three first flat keyways 111 are suitable for positioning three force sensor bases 5 in a one-to-one correspondence.

[0050] Preferably, a plurality of threaded holes are arranged around each first flat keyway 111, and the force sensor base 5 is fixed at these threaded holes by countersunk screws.

[0051] like Figures 1-5 As shown, the friction block base 2 includes a platform portion 21 and three support rod portions 22.

[0052] The platform section 21 is a hexagonal or equilateral triangular flat plate structure. A rectangular friction block mounting groove 211 is provided in the center of its upper surface, and a central through hole 212 is provided at the bottom center of the friction block mounting groove 211. The platform section 21 is parallel to and spaced apart from the mounting plane 11.

[0053] Three support rods 22 extend outward from three spaced edges of the hexagonal platform 21, or from the three vertices of the equilateral triangular platform 21, respectively. The extension directions of all three support rods 22 are towards the mounting plane 11 of the mounting base 1. Each of the three support rods 22 forms an angle with the platform 21. The central axes of the three support rods 22 are orthogonal to each other, extending along the x1, y1, and z1 directions, with their intersection point located at the center of the platform 21. One end of each support rod 22 is fixedly connected to the platform 21; in some embodiments, the three support rods 22 and the platform 21 are integrally formed.

[0054] See Figure 3 and Figure 5 A first screw hole 221 extends inward on the end face of the free end of each support rod 22. The first screw hole 221 extends along the axial direction of the support rod 22 and is used to engage the force transmission structure 4.

[0055] See Figure 1 and Figure 3 The friction block 3 is mounted on a rectangular friction block mounting base, the shape and size of which are adapted to the friction block mounting groove 211. A threaded hole is provided at the bottom of the friction block mounting base. A screw passes through the central through hole 212 of the friction block base 2 from the bottom and is screwed into the threaded hole of the friction block mounting base, thus fixing the friction block 3 on the platform part of the friction block base 2 away from the mounting base 1.

[0056] In this invention, a screw passes through the friction block base 2 to connect the friction block 3. Tightening the screw secures the friction block 3 to the friction block base 2. The friction block 3, as the stationary component of the friction pair, bears the contact force of the relative motion between the friction pairs and transmits the contact force to the friction block base 2. The friction contact surface of the friction block 3 coincides with the intersection point of the central axes of the three support rods 22.

[0057] See Figures 1-3 One end of each of the three force transmission structures 4 is fixedly connected to one of the three support rods 22 of the friction block base 2 by a double-ended screw 7 and extends along the central axis of the corresponding support rod 22. The other end of each of the three force transmission structures 4 is fixedly connected to one of the three force sensor bases 5.

[0058] like Figure 1 , Figure 2 and Figure 7 As shown, the force sensor base 5 is a block shape, including a top surface, a bottom surface, four side surfaces, and a mounting ramp 51. It can be understood that the force sensor base 5 is a block shape obtained by cutting off one edge of a quadrangular prism. The ramp created by cutting off one edge is the mounting ramp 51. After assembly, the mounting ramp 51 is perpendicular to the central axis of the support rod 22. The mounting ramp 51 extends between the top surface and one side surface.

[0059] See Figure 7 The force sensor base 5 has two vertically downward extending countersunk holes 54 on its top surface and mounting inclined surface 51, and the countersunk screws can be used to fix the force sensor base 5 on the mounting base 1 through the countersunk holes 54.

[0060] See Figure 3 and Figure 7The force sensor base 5 has an inclined threaded hole 52 perpendicular to the inclined surface 51. The other end of the three force transmission structures 4 is threadedly connected to the inclined surface 51 of one of the three force sensor bases 5 through the inclined threaded hole 52 and a screw.

[0061] See Figure 3 and Figure 7 The bottom surface of the force sensor base 5 is also provided with a second flat keyway 53. The flat key 6 is engaged within the first flat keyway 111 and the second flat keyway 53 to achieve the positioning of the force sensor base 5 on the mounting base 1.

[0062] See Figure 1-3 Each force transmission structure 4 includes a force transmission shaft 41, and the lateral bending stiffness K of the force transmission shaft 41 is... b Less than or equal to axial tensile / compressive stiffness K p 1%.

[0063] Among them, K b and K p The results can be obtained using the following formulas:

[0064]

[0065]

[0066]

[0067] γ represents the degree of decoupling;

[0068] L represents the length of the rib 4121 of the force transmission shaft 41;

[0069] A n This represents the cross-sectional area of ​​a single rib 4121;

[0070] n represents the number of ribs;

[0071] E represents the elastic modulus of the material of the force transmission shaft 41.

[0072] According to a triaxial contact force measuring device of the present invention, when the friction block 3 is subjected to a triaxial contact force load, the force load is transmitted to the force sensor base 5 through the force transmission structure 4. The three orthogonally arranged force transmission structures 4 transmit forces in different directions respectively, and the magnitude of the transmitted axial force load is measured by the force sensor 43. Since the friction block base 2 connects the three orthogonal force transmission structures 4 together, in order to avoid the influence of force-dimensional coupling on the force measurement results, a specific force transmission shaft 41 of the present invention is used as the core component of the force transmission structure 4. The two ends of the force transmission shaft 41 are respectively connected to the friction block base 2 and the force sensor 43, and the connection method can be a conventional fixed connection method. The second part 412 of the force transmission shaft 41 adopts a special structural design, with ribs 4121 as flexible hinge structures. The axial dimension of the ribs 4121 is larger than the cross-sectional dimension, thereby ensuring the transverse bending stiffness K of the ribs 4121. b Much lower than the axial tensile and compressive stiffness K p This ensures the axial tensile and compressive stiffness K of the force transmission shaft 41 composed of ribs 4121. p Much higher than the lateral bending stiffness K b .

[0073] The mechanical property testing device for the blade crown contact interface of aero-engine turbine blades of the present invention reduces the ratio of lateral bending stiffness to axial tensile and compressive stiffness, thereby reducing the proportion of lateral deformation load in the non-measured force direction to load transmitted in the measured force direction, and thus achieving control of measurement accuracy by changing the decoupling degree through changing structural parameters.

[0074] Based on this, in a conventional rectangular coordinate system, since the force load level varies in each direction, the direction with a smaller force load level is affected by the direction with a larger force load level, resulting in a larger relative error in the direction with the smaller force load level. To reduce the influence of the contact force level between different directions on the relative error, this invention uses a special first rectangular coordinate system to arrange the force transmission structure. This first rectangular coordinate system has a linear transformation relationship with a second rectangular coordinate system with the mounting plane 11 (horizontal plane) as the y2-z2 plane and the normal direction of the mounting plane 11 (vertical direction) as the x2 direction. By using the second rectangular coordinate system as the working coordinate system for the friction block 3 and using the first rectangular coordinate system to arrange the force transmission structure and measure the contact force, the coupling effect between force dimensions in different directions is only related to the decoupling degree of the force transmission axis 41, and is independent of the magnitude of the contact force, thereby reducing the influence of the contact force level between different directions on the relative error.

[0075] The linear transformation relationship between the first and second rectangular coordinate systems depends on how the coordinate systems are defined. Differences in this definition include variations in the defined direction and naming, as well as differences in the positive direction. These variations will therefore change the linear transformation relationship, including transformations between rows and columns, and transformations between positive and negative signs. The linear transformation relationship between these two coordinate systems satisfies the following formula:

[0076]

[0077]

[0078] According to the test device for the mechanical properties of the blade crown contact interface of the aero-engine turbine blade of the present invention, the three force transmission structures 4 are arranged in the direction of the first rectangular coordinate system x1-y1-z1. If a load f1 is applied in the first rectangular coordinate system x1-y1-z1, then:

[0079]

[0080] Apply a load f in the x1 direction x1 For example, when friction block 3 deforms in the x1 direction, the force transmission structure 4 in the x1 direction undergoes axial deformation, while the other two force transmission structures 4 undergo transverse bending deformation. According to the deformation compatibility condition, the deformation of friction block 3 under load along the first rectangular coordinate system x1-y1-z1 can be expressed as follows:

[0081]

[0082]

[0083]

[0084] Defined in the first rectangular coordinate system x1-y1-z1, the support reaction force provided by the force transmission structure 4 along the x1 direction to the friction block 3 can be expressed as F. x,x1 F x,y1 and F x,z1 Similarly, the support reaction force provided by the force transmission structure 4 in other directions to the friction block 3 can be obtained, and according to the force balance condition, the relationship between the support reaction force F1 and the load f1 can be obtained as follows:

[0085]

[0086] Calculate the support reactions separately when only load f1 is applied, and then add them together to obtain the support reaction matrix F1:

[0087]

[0088] Among them, the force sensors 43 of the three force transmission structures 4 measure the loads f in different directions. 1tfor:

[0089]

[0090] At this point, the relative error can be expressed as:

[0091]

[0092]

[0093]

[0094] Clearly, the error level is related to the load level, which can lead to uncontrollable and extremely large relative errors, for example, when f z1 When the relative error e is much smaller than that in the other two directions, z1 It will be magnified infinitely.

[0095] When a load f2 is applied according to the second rectangular coordinate system x2-y2-z2, the load can be equivalent to f in the first rectangular coordinate system x1-y1-z1. 1,2 for:

[0096]

[0097]

[0098] that is

[0099]

[0100] The load f in the first rectangular coordinate system is obtained by measuring the loads in the first rectangular coordinate system from the three force transmission structures 4 arranged according to the first rectangular coordinate system. 1t,2 for

[0101]

[0102] Load f 1t,2 The actual measurement result f is obtained by transforming back to the second rectangular coordinate system. 2t,2 ,

[0103]

[0104] At this point, the actual measurement result f 2t,2 The relative error between the load f2 and the load f2 can be expressed as:

[0105]

[0106]

[0107]

[0108] At this point, the relative error is only related to the decoupling degree γ and is independent of the contact force level. That is, by applying the load according to the second rectangular coordinate system and measuring the load level according to the first rectangular coordinate system, the relative error of the contact force measurement result can be decoupled from the contact force level, so that the accuracy of the force measuring device is only related to the decoupling degree of the force transmission shaft 41.

[0109] Furthermore, such as Figures 1-3 As shown, each force transmission structure 4 includes a force transmission shaft 41, a force sensor adapter disk 42, and a force sensor 43. One end of the force transmission shaft 41 is fixedly connected to the support rod portion 22 of the friction block base 2 by a double-ended screw 7, and the central axis of the force transmission shaft 41 coincides with the central axis of the first screw hole 221. The other end of the force transmission shaft 41 is fixedly connected to the force sensor adapter disk 42, the force sensor adapter disk 42 is fixedly connected to the force sensor 43, and the force sensor 43 is fixedly connected to the force sensor base 5.

[0110] See Figures 8-11 In this embodiment 1, the force transmission shaft 41 is a hollow shaft structure, divided axially into a first part 411, a second part 412, and a third part 413. The first end of the first part 411 is fixedly connected to the end furthest from the friction block base 2 by a double-ended screw 7. The first end of the second part 412 is fixedly connected to the second end of the first part 411, and the second end of the second part 412 is fixedly connected to the first end of the third part 413. The second end of the third part 413 of the force transmission shaft 41 is fixedly connected to the force sensor adapter plate 42.

[0111] The outer diameters of the first part 411 and the second part 412 are the same and smaller than the outer diameter of the third part 413. The inner diameters of the second part 412 and the third part 413 are the same and larger than the inner diameter of the first part 411.

[0112] The second part 412 of the force transmission shaft 41 consists of multiple circumferentially distributed ribs 4121. The ribs 4121 of the force transmission shaft 41 are evenly distributed along the circumference, thereby ensuring that the stiffness of the force transmission shaft 41 is uniform in all directions.

[0113] See Figure 10 The cross-section of rib 4121 is fan-shaped, and the gap between ribs 4121 is taken as the minimum value allowed by the manufacturing process, for example, 1 to 3 mm. In a three-way contact force measuring device of the present invention, the size of the rib 4121 of the force transmission shaft 41 determines the transverse bending stiffness K of the force transmission shaft 41. b and axial tensile and compressive stiffness K p And decoupling degree, the dimensions of rib 4121 can be determined according to the required transverse bending stiffness K. b and axial tensile and compressive stiffness K p Adjust the degree of decoupling.

[0114] The decoupling degree can be calculated using theoretical formulas. Based on these formulas, the required transverse bending stiffness K can be determined. b and axial tensile and compressive stiffness K p The dimensions of the decoupling design rib 4121 are related to the decoupling degree. With a fixed decoupling degree γ, a greater number of ribs 4121 results in a higher lateral bending stiffness K of the force transmission shaft 41. b and axial tensile and compressive stiffness K p The larger the rib 4121, the greater the number of ribs 4121. Given a fixed size for the rib 4121, the number of ribs 4121 depends on the diameter of the force transmission shaft 41 and the gap between different ribs 4121. The gap size depends on the manufacturing process; where the manufacturing process allows, the smaller the gap between ribs 4121 and the greater the number of ribs 4121, the greater the transverse bending stiffness K. b and axial tensile and compressive stiffness K p The larger the value, the higher the structural stiffness of the measuring device.

[0115] Furthermore, the cross-sectional area A of rib 4121 n The relationship between the length L and the length L satisfies the following equation:

[0116]

[0117] When the shape and dimensions of the rib 4121 satisfy the above formula, the transverse bending stiffness K of the force transmission shaft 41 b Less than or equal to axial tensile / compressive stiffness K p 1%.

[0118] See Figure 8 , Figure 10 as well as Figure 11 The third part 413 is provided with multiple mounting through holes 4131, which extend axially along the force transmission shaft 41 and are evenly distributed circumferentially. The mounting through holes 4131 are used for connection with the force sensor adapter plate 42.

[0119] The force transmission shaft 41 can be made of bar or tube. First, the outer circumferential surfaces of the first part 411 and the second part 412 are machined. Then, a central through hole is made by drilling and / or reaming the hole. The inner surfaces of the second part 412 and the third part 413 are obtained by reaming or milling. Next, multiple axially extending, circumferentially distributed opening slots are cut into the second part 412 by wire cutting, milling or other cutting processes, so that the second part 412 becomes a structure surrounded by multiple circumferentially distributed ribs 4121. Finally, multiple mounting through holes 4131 are drilled in the third part 413.

[0120] See Figure 3One side of the double-ended screw 7 engages with the first screw hole 221 of the friction block base 2, and the other side passes through the central through hole 212 of the first part 411 of the force transmission shaft 41 and is connected to the nut for installation and fastening. The force transmission shaft 41 is connected to the force sensor adapter plate 42 by screws, and the force sensor adapter plate 42 is connected to the top of the force sensor 43 by screws. The bottom of the force sensor 43 is mounted on the force sensor base 5 by screws.

[0121] The end of the force sensor 43 is fixedly connected to the mounting inclined surface 51 of the force sensor base 5, and the force sensor 43 is perpendicular to the mounting inclined surface 51. The three force sensor bases 5 are each independently fixed on the mounting plane 11 of the mounting base 1.

[0122] The number, length, and cross-sectional dimensions of the ribs 4121 in the accompanying drawings of this invention can be designed according to actual needs. The rib dimensions of the force transmission shaft 41 disclosed in this invention are primarily for ease of processing, and the gaps between the ribs are through grooves; therefore, the rib cross-section is a fan-shaped annulus. Figure 10 As shown, it is preferably equipped with 16 ribs.

[0123] The three-way contact force measuring device of the present invention is installed on the corresponding test bench according to the requirements of the application scenario. The friction block 3 is the stationary part of the friction pair and contacts the moving part of the friction pair. The friction block 3 is the test piece, and the material is determined according to the test requirements. The bottom of the friction block 3 is square to facilitate matching the friction block mounting groove 211 on the friction block base 2, and it has a threaded hole.

[0124] When the three-directional contact force measuring device of the present invention is applied to contact force measurement, the friction pair moving part contacts the friction block 3 to transmit the contact force, and the force sensors 43 in three orthogonal directions measure the force along the three coordinate axes in the first rectangular coordinate system, as shown in the schematic diagram of the coordinate system. Figures 2 to 5 As shown. Using the transformation relationships between coordinate systems, the measurement results of the contact force in the second rectangular coordinate system can be obtained. A schematic diagram of this coordinate system is shown below. Figures 1 to 3 As shown.

[0125] Compared with the prior art, the three-dimensional contact force measuring device provided in this embodiment effectively reduces the coupling effect between force dimensions in the three-dimensional contact force measurement by adopting a force transmission shaft 41 with a flexible hinge structure, thereby improving the measurement accuracy; by using a force transmission structure 4 arranged orthogonally in three directions according to the first rectangular coordinate system to measure the contact force, and by using a second rectangular coordinate system to define the working coordinate system of the friction block 3, the influence of the contact force level on the relative error of the three-dimensional contact force measurement is effectively eliminated; the three-dimensional force transmission structure 4 is connected together by the friction block base 2 to provide stiffness for the friction block 3, thereby achieving sufficient structural stiffness for the friction block 3 while ensuring that the size of the friction block 3 is small.

[0126] Example 2

[0127] Based on Embodiment 1, Embodiment 2 of the present invention employs a different force transmission shaft 41', such as... Figures 12-15 As shown.

[0128] The force transmission shaft 41' includes a first part 411', a second part 412', and a third part 413'. The first part 411' is a disk with a first through hole at its center and multiple second through holes evenly distributed circumferentially near its outer circumference. The first through holes are used for fixed connection with the friction block base 2, and the second through holes are used for mounting ribs 4121'.

[0129] The second part 412' includes multiple ribs 4121', each rib 4121' having a circular cross-section. The two ends of the ribs 4121' are respectively inserted into the second through hole of the first part 411' and the fourth through hole of the third part 413'. Both ends of the ribs 4121' are fixedly connected, which can be by threaded connection, interference fit connection, or other conventional fixed connection methods.

[0130] The third part 413' is a disk larger than the first part 411', with a third through hole at its center. Multiple fourth through holes are arranged around the outer circumference of the third through hole, and multiple mounting through holes 4131' are arranged around the outer circumference of the fourth through holes. The fourth through holes are used to connect the rib 4121', and the mounting through holes 4131' are used for fixed connection with the force sensor adapter disk 42.

[0131] In some embodiments, the cross-section of rib 4121' can also be trapezoidal, rectangular, or other suitable shapes. The cross-sectional area A of rib 4121' is... n The formula should also be satisfied with the length L.

[0132]

[0133] The technical solution of this embodiment 2 has a simple structure for the force transmission shaft 41', which is easy to process and assemble, and reduces production costs while ensuring measurement accuracy.

[0134] Example 3

[0135] The present invention also relates to a method for measuring three-dimensional contact force, wherein the method employs a three-dimensional contact force measuring device as described in Embodiment 1 or 2.

[0136] The method includes the following steps:

[0137] S1: Install one of the three-dimensional contact force measuring devices from Example 1 or 2 onto the corresponding test bench;

[0138] S2: Install the workpiece to be tested onto the test bench so that the part to be tested abuts against the friction block 3;

[0139] S3: Apply excitation to the workpiece to be tested, and force sensor 43 measures and feeds back the value of the three-dimensional contact force in the first rectangular coordinate system;

[0140] S4: The control system calculates the value of the three-dimensional contact force in the second rectangular coordinate system based on the pre-stored linear transformation relationship.

[0141] According to the above-described three-dimensional contact force measurement method of the present invention, since a special first rectangular coordinate system is used to arrange the force transmission structure and measure the contact force, and a second rectangular coordinate system is used as the coordinate system for the friction block 3 to work, the measurement result of the contact force in the second rectangular coordinate system is obtained by utilizing the transformation relationship between the coordinate systems. This makes the coupling effect between force dimensions in different directions only related to the decoupling degree of the force transmission axis 41, and independent of the magnitude of the contact force, thereby reducing the influence of the contact force level in different directions on the relative error.

[0142] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A three-dimensional contact force measuring device, characterized in that, The system includes a mounting base, a friction block base, a friction block, three force transmission structures, and three force sensor bases. The mounting base has a mounting plane. The friction block base includes a platform portion and three support rod portions. The platform portion is parallel to the mounting plane and spaced apart. The three support rod portions extend outward from the edge of the platform portion. The central axes of the three support rod portions are orthogonal to each other, and their intersection point is located at the center of the platform portion. One end of each of the three force transmission structures is fixedly connected to one of the three support rod portions of the friction block base and extends along the central axis of the corresponding support rod portion. The other end of each of the three force transmission structures is fixedly connected to one of the three force sensor bases. Each of the three force sensor bases is independent. The system is fixedly mounted on the mounting plane of the mounting base; the friction block is located on the platform portion of the friction block base on the side away from the mounting base, and the friction contact surface of the friction block coincides with the intersection of the central axes of the three support rods; the three force transmission structures are arranged according to a first rectangular coordinate system (x1-y1-z1), and the three force transmission structures extend along the x1, y1, and z1 directions respectively; the intersection of the central axes of the three support rods is the origin of the first rectangular coordinate system; each force transmission structure includes a force transmission shaft, which is a hollow shaft structure, and is divided into a first part, a second part, and a third part along the axial direction; the second part of the force transmission shaft consists of multiple circumferentially distributed ribs; the transverse bending stiffness K of the force transmission shaft is... b Less than or equal to axial tensile / compressive stiffness K p 1%; The first end of the first part is fixedly connected to one of the three support rods of the friction block base; the first end of the second part is fixedly connected to the second end of the first part; and the second end of the second part is fixedly connected to the first end of the third part. Each of the force transmission structures further includes a force sensor adapter disk and a force sensor. The second end of the third part of the force transmission shaft is fixedly connected to the force sensor adapter disk, the force sensor adapter disk is fixedly connected to the force sensor, and the force sensor is fixedly connected to the force sensor base.

2. The three-dimensional contact force measuring device according to claim 1, characterized in that, The first rectangular coordinate system (x1-y1-z1) and the second rectangular coordinate system (x2-y2-z2) with the mounting plane as the y2-z2 plane and the mounting plane normal as the x2 direction have the following linear transformation relationship:

3. The three-dimensional contact force measuring device according to claim 2, characterized in that, The outer diameter of the first part is the same as that of the second part and smaller than that of the third part, and the inner diameter of the second part is the same as that of the third part and larger than that of the first part.

4. The three-dimensional contact force measuring device according to claim 3, characterized in that, The cross-section of the rib is fan-shaped, trapezoidal, rectangular, or circular.

5. A three-dimensional contact force measuring device according to claim 4, characterized in that, The mounting base is an irregularly shaped flat plate. Multiple bolt holes and three first flat keyways are provided on the mounting base. The multiple bolt holes are evenly arranged on the periphery of the mounting base. The three first flat keyways are arranged in the middle of the upper surface of the mounting base, and the central axes of the three first flat keyways intersect at a point. The three central axes are at an angle of 120° to each other.

6. A three-dimensional contact force measuring device according to any one of claims 3-5, characterized in that, The force sensor base is a block shape with an inclined mounting surface. The end of the force sensor is fixedly connected to the inclined mounting surface, and the force sensor is perpendicular to the inclined mounting surface.

7. A method for measuring the three-dimensional contact force of an aero-engine turbine blade, characterized in that, Use a three-dimensional contact force measuring device according to any one of claims 1-6.

Images