A special fixture for measuring the moment of inertia of a rotating body

Abstract

The invention discloses a special clamp for measuring the moment of inertia of a rotating body, comprising a clamp body and a clamping device, wherein the clamping device is arranged on the clamp body, the rotating body to be measured is clamped by the clamping device, and the clamp body is provided with a vertical contact surface, a 45° contact surface and a horizontal contact surface; the clamp body is fixedly connected to a measuring table through the vertical contact surface, the 45° contact surface and the horizontal contact surface respectively, so that the axis of the rotating body to be measured is respectively 90°, 45° and 0° with the measuring table, so that the rotating body to be measured can be placed in six postures; the operator can fix the rotating body to be measured on the upper end of the measuring table at a certain angle through the clamp, and the clamp has the advantages of safe operation, short placement cycle, accurate placement angle of the object to be measured, reliable positioning and clamping, and stable overall hoisting.

Description

Technical Field

[0001] The invention relates to the technical field of fixtures, in particular to a special fixture used for measuring the moment of inertia of a rotating body. Background Art

[0002] The moment of inertia can directly reflect the difficulty of changing the rotation state of a rigid body. It has important physical significance in scientific experiments, engineering technology, aerospace, machinery and other industrial fields. The MPC inertia tester is a universal center of mass and moment of inertia comprehensive test bench. It measures the coordinates of the center of mass, mass, moment of inertia and product of inertia through any axis of the object to be tested by placing the object in six postures. The moment of inertia measurement method used by the instrument is the swing method, which indirectly obtains the moment of inertia by measuring the swing period of the rigid body.

[0003] According to the basic principle of moment of inertia measurement, the moment of inertia through any axis can be expressed by the following formula:

[0004] I H =I XX cos2α+I YY cos 2 β+I ZZ cos 2 Delta-2I XY cosαcosβ-2I YZ cosβcosδ-2I XZ cosαcosδ (1)

[0005] I H is the moment of inertia about its center of mass; I XX is the moment of inertia through its center of mass parallel to the X-axis; I YY is the moment of inertia through its center of mass and parallel to the Y axis; ZZ - the moment of inertia through its center of mass parallel to the Z axis; I XY ,I XZ ,I YZ are the inertia products in three directions respectively; α is the angle between the torsion bar axis H and the X-axis of the coordinate system on the object to be measured; β is the angle between the torsion bar axis H and the Y-axis of the coordinate system on the object to be measured; δ is the angle between the torsion bar axis H and the Z-axis of the coordinate system on the object to be measured; in order to obtain I XX ,I YY ,I ZZ ,I XY ,I XZ ,I YZ , six equations need to be established, that is, the object to be measured needs to be placed on the measuring platform six times. It is not difficult to see from formula (1) whether I can be measured with high accuracy. XX ,I YY ,I ZZ ,IXY ,I XZ ,I YZ The key is how to accurately measure α, β, and δ; in the process of using the MPC inertial tester to measure, the object to be measured is placed in six postures, and the object to be measured and the measuring platform must not have relative motion. The six postures are achieved by placing the object to be measured on the measuring platform in different ways so that the angles between its three coordinate axes and the rotation axis (the virtual straight line perpendicular to the measuring platform is called the rotation axis) are different. The six postures are defined as posture 1, posture 2, posture 3, posture 4, posture 5, and posture 6. According to the requirements of the MPC inertial tester, the angles between the three coordinate axes X, Y, and Z of the object to be tested and the rotation axis in posture 1 are 0°, 90°, and 90° respectively; the angles between the three coordinate axes X, Y, and Z of the object to be tested and the rotation axis in posture 2 are 90°, 0°, and 90° respectively; the angles between the three coordinate axes X, Y, and Z of the object to be tested and the rotation axis in posture 3 are 45°, 45°, and 90° respectively; the angles between the three coordinate axes X, Y, and Z of the object to be tested and the rotation axis in posture 4 are 90°, 90°, and 0° respectively; the angles between the three coordinate axes X, Y, and Z of the object to be tested and the rotation axis in posture 5 are 45°, 90°, and 45° respectively; the angles between the three coordinate axes X, Y, and Z of the object to be tested and the rotation axis in posture 6 are 90°, 45°, and 45° respectively. Each posture requires measuring the moment of inertia of the loaded instrument and the moment of inertia of the unloaded instrument (including the fixture). The moment of inertia of the object to be measured is calculated by subtracting the moment of inertia of the unloaded instrument from the moment of inertia of the loaded instrument.

[0006] Since the accuracy of the placement angle of the object to be measured and whether the object to be measured can be fixed on the top of the test bench directly affect the accuracy of the measurement results, the placement angle and fixation of the object to be measured become the key steps in the measurement of moment of inertia. Whether in the military or civilian fields, there are a large number of rotating body products with complex internal structures, such as rockets, guided missiles, etc. The moment of inertia parameter is a very important parameter for such products, and it is often necessary to measure the moment of inertia of them. During the test process, in order to enable the rotating body to be accurately placed in six postures on the measuring bench, reduce the placement time, position and clamp reliably, hoist the whole body steadily, place the operation safely, and prevent some assembly parts from interfering with the fixture, it is very necessary to design a special fixture for measuring the moment of inertia of the rotating body. Summary of the invention

[0007] The purpose of the present invention is to overcome the problems of difficult to control the placement angle error of the existing rotating body to be measured, long placement period and poor placement safety, and to provide a special fixture for measuring the rotational inertia of the rotating body.

[0008] The technical solution for achieving the purpose of the present invention is:

[0009] A special fixture for measuring the moment of inertia of a rotating body comprises a fixture body and a clamping device. The clamping device is arranged on the fixture body, and the rotating body to be measured is clamped by the clamping device. The fixture body is provided with a vertical contact surface, a 45° contact surface and a horizontal contact surface. The fixture body is fixedly connected to a measuring table through the vertical contact surface, the 45° contact surface and the horizontal contact surface, respectively, so that the axis of the rotating body to be measured is respectively 90°, 45° and 0° with the measuring table, so that the rotating body to be measured can be placed in six postures.

[0010] The clamping device comprises a pair of clamping mechanisms symmetrically arranged with each other, each clamping mechanism comprises a to-be-tested object supporting component and an to-be-tested object clamping component, the to-be-tested object supporting component is arranged on a position adjustment plate of the fixture body and can move on the position adjustment plate, and the two ends of the to-be-tested object supporting component are respectively connected to the to-be-tested object clamping component through a clamping screw; the rotating body to-be-tested object is clamped between the to-be-tested object supporting component and the to-be-tested object clamping component.

[0011] The object to be measured support component includes a slide rail base plate, a guide rail is arranged on the slide rail base plate, sliders are arranged at both ends of the guide rail, each slider is provided with an object to be measured support block, the two object to be measured support blocks are symmetrical to each other to form a V-shaped support block, a movable first screw rod is arranged in the object to be measured support block, one end of the first screw rod is movably connected to the bearing seat through a bearing, and the other end of the first screw rod is provided with a screw rod sleeve, which is connected to a hand wheel through a bearing arranged on the bearing seat, and the first screw rod is driven by shaking the hand wheel to move the object to be measured support block, thereby adjusting the distance between the two object to be measured support blocks to adapt to rotating objects to be measured of different sizes.

[0012] The object clamping component to be tested includes a pressing plate, a second screw rod is provided in the middle of the pressing plate, the pressing plate is threadedly connected to the second screw rod, and the end of one end of the second screw rod is connected to the handwheel; the other end of the second screw rod is gap connected to the clamping block, and the end passes through the clamping block and is connected to the bolt through a gasket.

[0013] The top end of the clamping screw rod is respectively connected to the two ends of the pressure plate with threads, and the top end passes through the pressure plate to be connected to the hand wheel, and the bottom end of the clamping screw rod is fixedly connected to the slide rail bottom plate of the support component of the object to be tested.

[0014] A buffer block is provided on the support block for the object to be tested.

[0015] The buffer block is made of urethane foam and is provided with a countersunk hole.

[0016] The clamping block is a clamping block with V-shaped groove and rectangular groove features.

[0017] The first screw rod has positioning surfaces at both ends.

[0018] The rotating body to be tested is cylindrical, conical, or a rotating body with cylindrical and conical features, and a rotating body accessory with side strip wing features mounted on the surface; the rotating body to be tested has a diameter of 50-300mm and a length of 700-2500mm.

[0019] The present invention provides a special fixture for measuring the moment of inertia of a rotating body. The fixture body of the fixture has three contact planes with the measuring table. The angle between the axis direction of the rotating body to be measured and the measuring table can be adjusted by contacting different planes with the measuring table. The angles are 0°, 45° and 90° respectively, and it is also convenient to take out the rotating body to be measured. The fixture can be placed in all six postures required for measurement. A hand wheel is installed on one side of the support component of the object to be measured, the clamping component of the object to be measured and the clamping screw rod. The hand wheel can be adjusted to better fix the rotating body to be measured on the fixture. At the same time, rotating bodies to be measured with different diameters can be measured. Rotating bodies to be measured with different lengths can be measured in combination with a position adjustment plate. The fixture can measure the diameter of the rotating object to be measured in the range of about 50mm~300mm and the length range of about 700mm~2500mm; the overall design of the fixture is convenient for fixing on the workbench, with safe operation, short placement cycle, stable overall hoisting, reliable positioning and clamping, accurate placement angle of the rotating object to be measured, and also avoids the interference problem of accessories such as side wings on the surface of the rotating object to be measured. The operator can use this fixture to fix the rotating object to be measured at a certain angle on the upper end of the measuring table, which has the advantages of safe operation, short placement cycle, accurate placement angle of the object to be measured, reliable positioning and clamping, and stable overall hoisting. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is an axonometric diagram of the overall structure of a special fixture used for measuring the moment of inertia of a rotating body;

[0021] Figure 2 is a schematic diagram of the structure of the fixture body;

[0022] Figure 3 is a schematic diagram of the structure of the clamping device;

[0023] Figure 4 It is a schematic diagram of the exploded structure of the support component of the object to be tested;

[0024] Figure 5 It is a schematic diagram of the exploded structure of the clamping part of the object to be tested;

[0025] Figure 6 is a structural schematic diagram of the first screw rod;

[0026] Figure 7 Schematic diagram of posture 4, posture 6 and posture 2 when the rotating object to be tested is clamped;

[0027] Figure 8Schematic diagram of posture three and posture five when the rotating object to be tested is clamped;

[0028] Fig. 9 It is a schematic diagram of the first posture of the rotating object to be tested when it is clamped;

[0029] In the figure: 1. fixture body 2. rotating object to be measured 3. clamping device 4. position adjustment plate 5. support part of the object to be measured 6. clamping part of the object to be measured 7. vertical contact surface of the fixture body 8. 45° contact surface of the fixture body 9. horizontal contact surface of the fixture body 10. clamping screw 11. handwheel 5-1. bearing seat 5-2. bearing 5-3. screw sleeve 5-4. buffer block 5-5. support block of the object to be measured 5-6. first screw 5-7. slider 5-8. slide rail bottom plate 5-9. guide rail 5-10. positioning surface 6-1. gasket 6-2. second screw 6-3. pressure plate 6-4. bolt 6-5. clamping block. DETAILED DESCRIPTION

[0030] The present invention is further described below with reference to the accompanying drawings and embodiments, but the present invention is not limited thereto.

[0031] Example:

[0032] like Figure 1 , Figure 2 As shown, a special fixture for measuring the rotational inertia of a rotating body comprises a fixture body 1 and a clamping device 3. The clamping device 3 is arranged on the fixture body 1. The rotating object 2 to be measured is clamped by the clamping device 3. The fixture body 1 is provided with a vertical contact surface 7, a 45° contact surface 8 and a horizontal contact surface 9. The fixture body 1 is fixedly connected to the measuring platform through the vertical contact surface 7, the 45° contact surface 8 and the horizontal contact surface 9, respectively, so that the axis of the rotating object 2 to be measured is respectively 90°, 45° and 0° with the measuring platform, so that the rotating object 2 to be measured can be placed in six postures.

[0033] The rotating object to be tested 2 is cylindrical, conical, or a rotating object with cylindrical and conical features, and a rotating object accessory with edge strip wing features installed on the surface; the diameter of the rotating object to be tested is 50-300mm, and the length is 700-2500mm.

[0034] like Figure 3As shown, the clamping device 3 comprises a pair of clamping mechanisms symmetrically arranged with each other, each clamping mechanism comprises a test object supporting component 5 and a test object clamping component 6, the test object supporting component 5 is arranged on the position adjustment plate 4 of the fixture body 1, and can move on the position adjustment plate 4, and the two ends of the test object supporting component 5 are respectively connected with the test object clamping component 6 through the clamping screw 10; the rotating body test object 2 is clamped between the test object supporting component 5 and the test object clamping component 6; by adjusting the relative position of the test object supporting component 5 on the position adjustment plate 4, the clamping position of the rotating body test object 2 along the axial direction can be adjusted, thereby realizing the clamping and measurement of rotating bodies of different lengths.

[0035] like Figure 4 As shown, the object under test support component 5 includes a slide rail base plate 5-8, a guide rail 5-9 is provided on the slide rail base plate 5-8, sliders 5-7 are provided at both ends of the guide rail 5-9, each slider 5-7 is provided with an object under test support block 5-5, and the two object under test support blocks 5-5 are symmetrical to form a V-shaped support block, and a movable first screw rod 5-6 is provided in the object under test support block 5-5, one end of the first screw rod 5-6 is movably connected to the bearing seat 5-1 through a bearing 5-2, and the other end of the first screw rod 5-6 is provided with a screw rod sleeve 5-3, and the screw rod sleeve 5-3 is connected to the hand wheel 11 through the bearing 5-2 provided on the bearing seat 5-1, and the first screw rod 5-6 is driven by shaking the hand wheel 11 to move the object under test support block 5-5, thereby adjusting the distance between the two object under test support blocks 5-5 to adapt to the rotating body of the object under test 2 of different sizes.

[0036] like Figure 5 As shown, the object-to-be-tested clamping component 6 comprises a pressure plate 6-3, a second screw rod 6-2 is provided in the middle part 6-3 of the pressure plate, the pressure plate 6-3 is threadedly connected to the second screw rod 6-2, and the end of one end of the second screw rod 6-1 is connected to the handwheel 11; the other end of the second screw rod 6-2 is gap-connected to the clamping block 6-5, and the end passes through the clamping block 6-5 and is connected to the bolt 6-4 through the gasket 6-1.

[0037] The top end of the clamping screw 10 is respectively connected to the two ends of the pressure plate 6-3 with threads, and the top end passes through the pressure plate 6-3 to be connected to the hand wheel 11, and the bottom end of the clamping screw 10 is fixedly connected to the slide rail bottom plate 5-8 of the test object support component 5.

[0038] A buffer block 5 - 4 is provided on the object-to-be-tested supporting block 5 - 5 .

[0039] The buffer block 5 - 4 is made of eucalyptus material, and a countersunk hole is provided on the buffer block 5 - 4 . The buffer block and the countersunk hole have the function of protecting the rotating body to be tested.

[0040] The clamping block 6 - 5 is a clamping block with V-shaped groove and rectangular groove features, which is convenient for clamping the rotating object 1 to be tested with different diameters, while avoiding interference with its side strip wing feature accessories.

[0041] like Figure 6 As shown, the first screw rod 5-6 is provided with positioning surfaces 5-10 at both ends.

[0042] The process of using the fixture is:

[0043] When using the present invention, a Cartesian coordinate system is first established based on the rotating object to be measured. For example, the direction of the axis of the rotating object to be measured can be set as the x-axis, and the upward direction can be set as the y-axis. The coordinate origin can be selected as the intersection of the axis of the rotating object to be measured and the surface. In order to reduce the redundant workload when placing the posture, the order of placing the posture is defined as: posture 4 → posture 6 → posture 2 → posture 3 → posture 5 → posture 1;

[0044] Clamping steps: the staff fixes the horizontal contact surface 9 of the fixture body 1 on the measuring table, places the support component 5 of the object to be measured on the fixture body 1, selects the placement position through the position adjustment plate 4 and fixes it through bolts and nuts, rotates the first screw rod 5-6 by turning the hand wheel 11, and the thread on the first screw rod 5-6 drives the screw rod sleeve 5-3 to rotate, the screw rod sleeve 5-3 drives the support block 5-5 of the object to be measured to move, the support block 5-5 of the object to be measured drives the slider 5-6 to move, and the slider 5-6 moves on the guide rail 5-8, so that the rotating body to be measured 2 has a better placement environment;

[0045] The rotating body 2 of the object to be tested is hoisted and placed on the supporting part 5 of the object to be tested, and the handwheels 11 at both ends of the clamping part 6 of the object to be tested are rotated, and the handwheels 11 drive the pressing screw 10 to move, and the pressing screw 10 drives the pressing plate 6-3 to move, and the pressing plate 6-3 drives the second screw 6-2 to move, and the second screw 6-3 drives the clamping block 6-5 to move, and the handwheel 11 at the top of the second screw 6-2 drives the second screw 6-3 to move, and the second screw 6-3 drives the clamping block 6-5 to move, and the handwheel 11 at the top of the pressing screw 10 can be used to more conveniently and quickly fix the rotating body 2 to the fixture body 1;

[0046] Steps for changing postures: Turn the hand wheel 11 at the top of the pressing screw 10, take out the clamping part 6 of the object to be tested, rotate the rotating object to be tested 2 to a certain angle, and repeat the clamping steps to place the object to be tested 2 in posture 6 and posture 2 in sequence. Make the vertical contact surface 7 and the 45° contact surface 8 on the fixture body 1 fixedly contact with the measuring table, and then you can place the rotating object to be tested 2 in all other postures. Figure 7 , Figure 8 and Fig. 9 , the schematic diagrams of each posture are shown as follows: The schematic diagrams of posture four, posture six and posture two are shown as Figure 7As shown; the schematic diagrams of posture three and posture five are as shown Figure 8 As shown; the schematic diagram of posture one is as follows Fig. 9 shown.

[0047] If the moment of inertia of the rotating object 2 passing through an arbitrary axis at the center of mass of the rotating object 2 to be measured is to be measured, the moment of inertia data of the measurement result can be converted into Euler angles.

Claims

1. A special fixture for measuring the moment of inertia of a rotating body, characterized in that: The fixture comprises a fixture body and a clamping device, wherein the clamping device is arranged on the fixture body, the rotating object to be measured is clamped by the clamping device, and the fixture body is provided with a vertical contact surface, a 45° contact surface and a horizontal contact surface; the fixture body is fixedly connected to the measuring table through the vertical contact surface, the 45° contact surface and the horizontal contact surface, respectively, so that the axis of the rotating object to be measured is respectively 90°, 45° and 0° with the measuring table, so that the rotating object to be measured can be placed in six postures; The clamping device comprises a pair of clamping mechanisms symmetrically arranged with each other, each clamping mechanism comprises a support component for the object to be tested and a clamping component for the object to be tested, the support component for the object to be tested is arranged on a position adjustment plate of the fixture body and can move on the position adjustment plate, and both ends of the support component for the object to be tested are respectively connected to the clamping component for the object to be tested by a pressing screw; the rotating object to be tested is clamped between the support component for the object to be tested and the clamping component for the object to be tested; The object-to-be-tested support component comprises a slide rail bottom plate, a guide rail is arranged on the slide rail bottom plate, sliders are arranged at both ends of the guide rails, each slider is provided with an object-to-be-tested support block, the two object-to-be-tested support blocks are symmetrical to form a V-shaped support block, a movable first screw rod is arranged in the object-to-be-tested support block, one end of the first screw rod is movably connected to the bearing seat through a bearing, a screw rod sleeve is arranged at the other end of the first screw rod, the screw rod sleeve is connected to the hand wheel through the bearing arranged on the bearing seat, the first screw rod is driven by shaking the hand wheel to move the object-to-be-tested support block, thereby adjusting the distance between the two object-to-be-tested support blocks to adapt to rotating objects to be tested of different sizes; The object clamping component to be tested includes a pressing plate, a second screw rod is provided in the middle of the pressing plate, the pressing plate is threadedly connected to the second screw rod, and the end of one end of the second screw rod is connected to the handwheel; the other end of the second screw rod is gap connected to the clamping block, and the end passes through the clamping block and is connected to the bolt through a gasket.

2. A special fixture for measuring the moment of inertia of a rotating body according to claim 1, characterized in that: The top end of the clamping screw rod is respectively connected to the two ends of the pressure plate with threads, and the top end passes through the pressure plate to be connected to the hand wheel, and the bottom end of the clamping screw rod is fixedly connected to the slide rail bottom plate of the support component of the object to be tested.

3. A special fixture for measuring the moment of inertia of a rotating body according to claim 1, characterized in that: A buffer block is provided on the support block for the object to be tested.

4. A special fixture for measuring the moment of inertia of a rotating body according to claim 3, characterized in that: The buffer block is made of urethane foam and is provided with a countersunk hole.

5. The special fixture for measuring the moment of inertia of a rotating body according to claim 1, characterized in that: The clamping block is a clamping block with V-shaped groove and rectangular groove features.

6. A special fixture for measuring the moment of inertia of a rotating body according to claim 1, characterized in that: The first screw rod has positioning surfaces at both ends.

7. A special fixture for measuring the moment of inertia of a rotating body according to claim 1, characterized in that: The rotating body to be tested is cylindrical, conical, or a rotating body with cylindrical and conical features, and a rotating body accessory with side strip wing features mounted on the surface; the rotating body to be tested has a diameter of 50-300mm and a length of 700-2500mm.

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