A pin-type radial force sensor

Abstract

The invention discloses a pin-type radial force sensor for mechanical equipment, which is used to measure the magnitude and action direction of the radial force at the rotating joint of the mechanical equipment. The invention comprises a pin, 8 strain gauges pasted on the pin, and two groups of bridge measurement circuits connected by the strain gauges. The invention is characterized in that: two grooves are opened on the pin, 4 strain gauges are evenly laid and pasted on each groove at an interval of 90 degrees, the strain gauges are parallel to the pin axis or at an angle of ±45 degrees, every 4 strain gauges are connected to form a bridge circuit in a certain order, the two groups of bridge circuits are used to measure the radial force in the X and Y directions, and the magnitude and direction of the radial force at the joint can be measured according to the force synthesis principle; one end of the sensor is provided with axial and circumferential limit structures to prevent the pin from axial stringing and circumferential rotation during measurement, thereby improving sensitivity and measurement accuracy.

Description

Technical Field

[0001] The present invention relates to a force sensor, in particular to a pin-type radial force sensor. Background Art

[0002] Radial force measurement is widely needed in the fields of industrial and agricultural machinery and equipment, testing and inspection, etc. Due to the limitations of structure and spatial size, general tensile, compressive, shear or bending force sensors are difficult to use for radial force measurement due to size and structure. At present, pin-type force sensors are mostly used for radial force measurement at home and abroad. Existing pin-type radial force sensor products are all unidirectional radial force sensors. For example, pin-type radial force sensors used for hooks and pulleys require clear knowledge of the direction of the radial force during installation and use in order to determine the installation direction of the sensor. For unpredictable and uncertain radial forces, this unidirectional radial force sensor cannot meet the needs. Therefore, it is necessary to develop a new type of radial force sensor to meet production and test and inspection needs. Summary of the invention

[0003] In view of the above problems, the present invention proposes a pin-type bidirectional radial force sensor solution, which is improved and enhanced in structure, cloth piece and bridge assembly, and can detect radial component forces in X and Y directions respectively, and can accurately measure the magnitude and direction of radial force of unknown direction based on the principle of force synthesis.

[0004] The technical solution of the present invention is as follows: the sensor is composed of a pin shaft, a strain gauge pasted on the pin shaft, and two groups of bridge measurement circuits connected by the strain gauges. The strain gauges of the two groups of bridges respectively sense the deformation caused by the radial component forces in the X direction and the Y direction on the pin shaft, and output corresponding voltage values. The radial resultant force and the direction angle of the resultant force can be measured based on the force synthesis principle.

[0005] A circumferential groove is formed near both ends of the pin shaft, and four strain gauges are evenly distributed at 90 degrees on each groove, arranged opposite to each other in pairs, to sense radial forces in the X and Y directions respectively. A total of eight strain gauges are affixed to the two grooves, and the longitudinal axes of the eight strain gauges affixed to the grooves are parallel to the axis of the pin shaft or form an angle of ±45 degrees.

[0006] The eight uniaxial strain gauges are divided into two groups, the four strain gauges for sensing the radial force in the X direction are one group, and the four strain gauges for sensing the radial force in the Y direction are another group. The two groups of strain gauges are sequentially connected into two full-bridge measurement circuits to measure the radial component forces in the X direction and the Y direction respectively. The outputs of the two groups of bridges can measure the magnitude and direction angle of the radial resultant force on the pin shaft according to the principle of force synthesis. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A radial force measuring pin structure and strain gauge arrangement diagram, radial lead through hole;

[0008] Figure 2 A cross section of the left and right grooves of a force measuring pin and a layout diagram of strain gauges;

[0009] Figure 3 A circuit diagram of strain gauges connected to form a bridge measurement, indicating the connection sequence of the strain gauges;

[0010] Figure 4 Another radial force measuring pin structure and strain gauge arrangement diagram;

[0011] Figure 5 Another measurement circuit diagram of strain gauges connected into a bridge, indicating the connection order of the strain gauges;

[0012] Figure 1 to Figure 5 Chinese symbols: 1-pin shaft, 101-pin shaft head, 102-positioning notch, 103-locking pin hole, 104-thread, 110, 112-left groove, 111, 113-right groove, 120-radial lead through hole, 130-axial lead groove, 140-threading hole, R1~R4-strain gauges on the left groove, R5~R8-strain gauges on the right groove, 801 and 804-the first and fourth full-bridge measurement circuits of the radial component force in the Y direction, 802 and 803-the second and third full-bridge measurement circuits of the radial component force in the X direction. DETAILED DESCRIPTION

[0013] The specific implementation scheme and description of the present invention are given below in conjunction with the accompanying drawings

[0014] The pin-type radial force sensor of the present invention comprises a pin 1, eight strain gauges R1 to R8 attached to the pin, and two groups of bridge measurement circuits formed by connecting the strain gauges;

[0015] like Figure 1 , Figure 2 and Figure 4 The pin 1 can be a solid or hollow round pin, one end of which is provided with a pin head 101 for limiting the axial movement of the pin; the pin head can be integrated with the pin or separated from the pin, and connected to the pin through threads and a retaining spring. Figure 1 The example is that the pin shaft head and the pin shaft are integrated. Two positioning notches 102 are symmetrically opened at an interval of 180 degrees on the outer edge of the pin shaft head, and two bosses or screw holes can be set at an interval of 180 degrees on the pin shaft seat sleeve. During installation, the positioning notches 102 on the outer edge of the pin shaft head are clamped on the corresponding bosses on the pin shaft sleeve to limit the circumferential rotation of the pin shaft, or are fixed to the pin shaft seat sleeve with bolts to further limit the axial movement of the pin shaft; a thread 104 and a locking pin hole 103 are provided at the other end of the pin shaft, such as Figure 1 For example, the axial clearance of the pin shaft can be easily adjusted or the axial preload can be applied by the locking nut, and the locking pin hole 103 further locks the nut to prevent the nut from loosening; another optional solution is as follows Figure 4 As shown, only a locking pin hole 103 is provided at the other end of the pin shaft, which will be used in situations where it is not necessary to adjust the axial clearance and apply the axial preload.

[0016] like Figure 1 As shown, a left groove 110 and a right groove 111 are opened along the circumferential direction near the two ends of the pin shaft, and the groove section is arc-shaped, which can help reduce the stress concentration at the groove and reduce the measurement error groove; the two groove sections can also be rectangular for easy processing, such as Figure 4 The left groove 112 and the right groove 113 are provided.

[0017] like Figure 1 and Figure 2 As shown, two radial lead through holes 120 are opened on the circumferential surface of each groove at an interval of 90 degrees, and a total of four radial lead through holes are opened on the two groove surfaces. The through hole axis and the two notches on the outer edge of the pin shaft head are staggered at an angle of 45 degrees to the left and right. The two radial lead through holes are cross-shaped, and the four radial lead through holes are connected to the center hole of the pin shaft, so that the lead wires of the measuring bridge composed of the strain gauges laid on the grooves are inserted into the center hole of the pin shaft and are connected to the pin shaft 1 from the pin shaft head 101; another preferred solution is as follows Figure 4 As shown, four axial lead grooves 130 are opened axially at intervals of 90 degrees on the circumferential surface of the pin shaft, and four threading holes 140 are opened on the end surface of the pin shaft head to lead out the lead wires of the measuring bridge. The circumferential angle position of the axial lead grooves 130 is the same as that of the radial lead holes;

[0018] Four uniaxial strain gauges are laid and glued on each groove surface of the pin shaft, such as Figure 1 and Figure 2 As shown, 8 strain gauges are laid and pasted on the two grooves, among which R1~R4 are pasted on the left groove 110, and R5~R8 are pasted on the right groove 111. The 4 strain gauges on each groove surface are evenly distributed on the circumferential surface at intervals of 90 degrees, and are symmetrical to the central axis of the pin shaft in pairs. Among them, R1 and R3, R5 and R7 are symmetrical up and down, R2 and R4, R6 and R8 are symmetrical left and right or front and back, and R1 and R3 as well as R5 and R7 correspond to the circumferential positions of the two notches on the outer edge of the pin shaft head. The preferred layout scheme is that the longitudinal axes of the 8 strain gauges pasted on the grooves are parallel to the axis of the pin shaft to obtain greater sensitivity.

[0019] like Figure 3As shown, 8 uniaxial strain gauges are divided into 2 groups, each with 4 in each group, and are sequentially connected into 2 full-bridge measurement circuits, wherein the four strain gauges R1, R3 on the left groove and R5, R7 on the right groove are connected in the order of R1-R3-R5-R7 to form the first full-bridge measurement circuit 801 of the radial component force in the Y direction, and the four strain gauges R2, R4 on the left groove and R6, R8 on the right groove are connected in the order of R2-R4-R6-R8 to form the second full-bridge measurement circuit 802 of the radial component force in the X direction. The outputs of the two groups of X and Y bridges can obtain the magnitude and direction angle of the radial resultant force on the pin shaft according to the force synthesis principle.

[0020] Another preferred cloth scheme is as follows Figure 4 As shown in the figure, the longitudinal axes of the eight strain gauges are at an angle of ±45 degrees to the axis of the pin, that is, R1-R2, R2-R3, R3-R4, and R4-R1 are arranged at 90 degrees to each other. Similarly, R5, R6, R7, and R8 are arranged at 90 degrees to each other in sequence. Such a pattern can reduce the error caused by the change of the radial force application point of the pin; the bridging method for this pattern is as follows Figure 5 As shown, 8 uniaxial strain gauges are divided into 2 groups, each with 4 in each group, and are sequentially connected into 2 full-bridge measurement circuits, wherein the four strain gauges R1, R3 on the left groove and R5, R7 on the right groove are connected in the order of R1-R3-R7-R5 to form a third full-bridge measurement circuit 803 for radial force in the X direction, and the four strain gauges R2, R4 on the left groove and R6, R8 on the right groove are connected in the order of R2-R4-R8-R6 to form a fourth full-bridge measurement circuit 804 for radial force in the Y direction. The outputs of the two groups of X and Y bridges can obtain the magnitude and direction angle of the radial resultant force on the pin shaft according to the force synthesis principle.

Claims

1. A pin-type radial force sensor, comprising a pin (1), eight strain gauges (R1 to R8) attached to the pin, and two sets of bridge measurement circuits connected by the strain gauges; characterized in that: The pin (1) is a solid or hollow round pin; A pin head (101) is provided at one end of the pin shaft (1) for limiting the axial movement of the pin shaft. Two positioning notches (102) are symmetrically provided at an interval of 180 degrees on the outer edge of the pin head. Correspondingly, two bosses or screw holes are provided at an interval of 180 degrees on the pin shaft seat sleeve. During installation, the positioning notches (102) on the outer edge of the pin head are clamped onto the corresponding bosses on the pin shaft sleeve or fixed to the pin shaft seat sleeve by bolts to limit the circumferential rotation and axial movement of the pin shaft. The other end of the pin shaft has a thread (104) and an axially limited locking pin hole (103), which can adjust the axial clearance of the pin shaft or apply a preload. A left groove (110 or 112) and a right groove (111 or 113) are provided along the circumferential surface near the two ends of the pin shaft (1), wherein the groove has an arc-shaped cross section to reduce stress concentration and measurement error, or a rectangular cross section to facilitate processing and patching; Two cross-shaped radial lead through holes (120) are respectively opened on the surface of each groove of the pin shaft (1), and there are a total of four radial lead through holes on the two grooves. The radial lead through holes and the two positioning notches on the outer edge of the pin shaft head are spaced 45 degrees apart from each other. The pin shaft is a hollow cylinder, and the four radial lead through holes are connected to the center hole of the pin shaft so that the lead wires of the measuring bridge composed of the strain gauges can be inserted into the center hole of the pin shaft and lead out of the pin shaft (1) from the end of the pin shaft head (101); The eight strain gauges are uniaxial strain gauges, four of which are laid and pasted in each groove, and eight in total are pasted in two grooves, of which R1 to R4 are pasted on the left groove (110 or 112), and R5 to R8 are pasted on the right groove (111 or 113). The four strain gauges on each groove are evenly distributed at intervals of 90 degrees on the circumference, and are symmetrical to the central axis of the pin shaft in pairs, of which R1 and R3, R5 and R7 are symmetrical up and down, R2 and R4, R6 and R8 are symmetrical front and back, and R1 and R3 as well as R5 and R7 correspond to the circumferential angular positions of the two notches on the outer edge of the pin shaft head, and the longitudinal axes of the eight strain gauges pasted on the grooves are all parallel to the axis of the pin shaft; The layout of strain gauges is as follows: The eight strain gauges are uniaxial strain gauges, which are divided into two groups, each with four gauges, and are sequentially connected to form two full-bridge measurement circuits, wherein the four strain gauges R1 and R3 on the left groove and the four strain gauges R5 and R7 on the right groove are connected in the order of R1-R3-R5-R7 to form a first full-bridge measurement circuit (801) for radial force component in the Y direction, and the four strain gauges R2 and R4 on the left groove and the four strain gauges R6 and R8 on the right groove are connected in the order of R2-R4-R6-R8 to form a second full-bridge measurement circuit (802) for radial force component in the X direction, and the outputs of the two groups of X and Y bridges can obtain the magnitude and direction angle of the radial resultant force on the pin shaft according to the principle of force synthesis; or, The eight strain gauges are uniaxial strain gauges, and the longitudinal axes of the uniaxial strain gauges are arranged at an angle of ±45 degrees to the axis of the pin shaft; correspondingly, the eight uniaxial strain gauges are divided into two groups, each with four gauges, and are sequentially connected to form two full-bridge measurement circuits, wherein the four strain gauges R1 and R3 on the left groove and the four strain gauges R5 and R7 on the right groove are connected in the order of R1-R3-R7-R5 to form a third full-bridge measurement circuit (803) for radial force component in the X direction, and the four strain gauges R2 and R4 on the left groove and the four strain gauges R6 and R8 on the right groove are connected in the order of R2-R4-R8-R6 to form a fourth full-bridge measurement circuit (804) for radial force component in the Y direction. The outputs of the two groups of X and Y bridges can obtain the magnitude and direction angle of the radial resultant force on the pin shaft according to the force synthesis principle.

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