Ball disc type dragging force test test disc contact track radius calibration method

Abstract

The invention discloses a method for calibrating a contact track radius of a test disc in a ball disc type dragging force test. The method comprises the following steps: measuring and determining a radius rb of a test ball; acquiring the rotating speed nbo of the ball when the sliding-rolling ratio s is equal to 0; a lubricating system is started to enable lubricating oil to be sprayed to a ball-disc contact area for lubrication, then servo loading is carried out to enable the ball to make contact with the disc, and the contact stress can be any value in the design range of the contact force of the ball-disc testing machine; when the stress of the load sensor 2 jumps to the stress of the load sensor 1, the rotating speed of the ball driving motor at the moment is obtained to be a critical rotating speed nb '; when the stress of the load sensor 1 jumps to the stress of the load sensor 2, the rotating speed of the ball driving motor is the critical rotating speed nb ''; average value of two critical rotating speeds nb'and nb '' is taken as rotating speed # imgabs0 # imgabs1 # of ball during rolling contact of ball disc, and contact track radius # imgabs2 # of disc

Description

Technical Field

[0001] The invention relates to the field of lubricating grease drag force test under sliding / rolling motion contact conditions, and in particular to a contact track radius calibration method for a ball-disc type lubricating medium drag force test disc. Background Art

[0002] In the existing ball-on-disk lubrication medium drag force test process, the sliding and rolling motion parameters of the ball-on-disk are determined by the ball speed n d , disk speed n b , the radius of the sphere r b (the distance from the ball's rotation axis to the ball-disk contact point) and the disk contact track radius r d The rotation speed of the ball and the disk can be monitored by the encoder or other speed sensors that come with the electric spindle, and the radius of the ball can also be measured with a 0.0001mm micrometer. The contact track radius r of the disk is d It is difficult to measure accurately directly, and usually the sliding / rolling motion parameters of the test are calculated by substituting the theoretical values ​​of the test bench design into the formula. However, due to the influence of the machining accuracy and assembly position accuracy of the bench parts, the actual contact track radius r of the disk is usually d There may be a large deviation from the theoretical value of the test bench design, which leads to a large deviation between the ball / disk sliding / rolling motion speed and the sliding-rolling ratio calculated according to the design theoretical value and the actual value. This deviation is the main reason for the abnormal situation that the direction of the drag force is opposite to the theoretical direction during the low sliding-rolling ratio test.

[0003] The deviation between the contact radius of the disc contact track and the actual radius will lead to large errors in the calculation model of the lubricating medium drag force established by fitting the test data, especially in the small sliding-rolling ratio range. Therefore, calibrating the contact track radius of the disc by technical means is the key to solving this problem. In response to this problem, the present invention is based on the basic principle that the direction of the drag force will change with the change of the relative sliding-rolling direction, and provides a calibration method for the contact track radius of the ball-disk type lubricating medium drag force test disc, which can effectively overcome the deviation problem caused by the existing method. Summary of the invention

[0004] The purpose of the present invention is to provide a method for calibrating the contact track radius of a ball-disc drag force test disc. To achieve this purpose, the present invention adopts the following technical solutions:

[0005] A method for calibrating the contact track radius of a ball-disc drag force test disc, the steps comprising:

[0006] (1) Use a micrometer to measure the diameter of the test ball several times, and then determine the radius of the ball according to formula (1):

[0007]

[0008] Where: N is the number of measurements;

[0009] d i is the diameter of the ball measured for the i-th time, in meters.

[0010] (2) First, select a speed n within the allowable speed range of the disk drive servo motor. d Then, the contact radius of the disk track is substituted into formula (2) according to the design value of the test bench to calculate the ball speed n in pure rolling contact (i.e., the sliding-rolling ratio s = 0). bo .

[0011]

[0012] Where: r d ' is the design value of the test bench for the radius of the pan-joined track, in m;

[0013] n d is the rotation speed of the disk, in r / min;

[0014] r b is the radius of the sphere determined by multiple measurements, in meters;

[0015] (3) Turn on the lubrication system to spray lubricating oil to the ball-disc contact area for lubrication, and then perform servo loading to make the ball and disc contact. The contact stress can be any value within the design range of the contact force of the ball-disc testing machine.

[0016] (4) Use the disk drive servo motor servo controller to control the motor at a speed n d The servo controller controls the rotation of the ball and then drives the servo motor to press n bo +Δn b Rotation, Δn b is the large increment of speed, generally a positive integer, such as 5; according to the force values ​​measured by the two pressure sensors, it is judged whether load sensor 2 is under pressure and load sensor 1 is not under pressure. If not, the ball drive motor controller is used to control the ball drive motor speed to increase by Δn b , until load sensor 2 is under pressure and load sensor 1 is not under pressure. Then use the ball drive motor controller to control the ball drive motor speed to decrease by 1r / min, and observe the force values ​​measured by the two load sensors at the same time. When the force jumps from load sensor 2 to load sensor 1, the ball drive motor speed is the critical speed n b ′.

[0017] (5) Then use the disk drive servo motor servo controller to control the motor to rotate at a speed n d The servo controller controls the rotation of the ball and then drives the servo motor to press nbo -Δn b Rotation, Δn b is the speed reduction, which is generally a positive integer, such as 5. According to the force values ​​measured by the two pressure sensors, it is determined whether load sensor 1 is under pressure and load sensor 2 is not under pressure. If not, the ball drive servo motor controller is used to control the ball drive motor speed to reduce Δn. b , until load sensor 1 is under pressure and load sensor 2 is not under pressure. Then use the ball drive motor controller to increase the speed of the ball drive motor by 1r / min, and observe the force values ​​measured by the two load sensors at the same time. When the force jumps from load sensor 1 to load sensor 2, the speed of the ball drive motor is the critical speed n b ″.

[0018] (6) As in formula (3), take two critical speeds n b ′ and n b The average value of ″ is the ball speed when the ball and the disc are rolling in contact.

[0019]

[0020] (7) The contact track radius of the disk is:

[0021]

[0022] In the prior art, due to the contact track radius r of the disk d It is difficult to measure accurately directly, and usually the sliding / rolling motion parameters of the test are calculated by substituting the theoretical values ​​of the test bench design into the formula. However, due to the influence of the machining accuracy and assembly position accuracy of the bench parts, the actual contact track radius r of the disk is usually d There may be a large deviation from the theoretical value of the test bench design, resulting in a large deviation between the ball disc sliding / rolling motion speed and sliding-rolling ratio calculated by substituting the design value of the ball disc drag force test bench into the actual value.

[0023] The present invention proposes a new calibration method based on the following principles:

[0024] like Figure 1 As shown in the figure, under the action of the servo loading force, the ball and the disk make point contact. At the contact point, the linear velocities of the ball and the disk at the contact point are:

[0025]

[0026] Where: r b is the radius of the sphere, in m;

[0027] r d is the disk contact track radius, in m;

[0028] n b is the ball's rotation speed, in r / min;

[0029] n d is the rotation speed of the disk, in r / min;

[0030] v b is the linear velocity of the ball at the contact point, in m / s;

[0031] v d is the linear velocity of the disk at the contact point, in m / s;

[0032] The sliding-rolling ratio of the ball-disk contact is:

[0033]

[0034] Where: v s is the relative sliding speed of the ball relative to the disk, in m / s;

[0035] v r is the rolling speed of the ball-disk contact, in m / s;

[0036] s is the slide-roll ratio of the ball-disk contact.

[0037] When the sliding-rolling ratio s>0, that is, n b >n d r d / r b , the drag force on the ball at the contact point is in direction 1 (such as Figure 1 As shown), at this time, under the action of the drag force, the ball and its driving motor components rotate around the radial air bearing main axis, causing the load sensor 2 to be under pressure, while the load sensor 1 is not under pressure; when the sliding-rolling ratio s is less than 0, that is, n b <n d r d / r b , the drag force on the ball at the contact point is in direction 2 (such as Figure 1 As shown), under the action of the drag force, the ball and its driving motor components rotate around the radial air bearing main axis, causing the load sensor 1 to be subjected to pressure, while the sensor 2 is not subjected to pressure.

[0038] By using the above relationship, the critical speed n at which the force on load sensor 2 changes to the force on load sensor 1 can be measured by controlling the speed of the ball-driven servo motor. b ′ and the critical speed n from the load sensor 1 to the load sensor 2 b ", the difference between these two speeds is not big, and they are very close to the speed of the ball when the ball-disk contact is rolling contact. Considering the influence of the friction torque of the air bearing, the critical speed n of the load sensor 2 jumping to the load sensor 1 is b The rotation speed of ' is slightly less than the rotation speed of the ball when the ball-disk contact is rolling contact The critical speed n is the speed at which the load sensor 1 is subjected to a force jump to the load sensor 2. b The rotation speed of ' is slightly greater than the ball speed when the ball-disk contact is rolling contact Therefore, the ball speed is when the ball-disk contact is rolling contact You can take n b ′ and n b The average value of ″, that is

[0039]

[0040] Where: n b ' is the critical speed when the load sensor 2 is subjected to force and then changes to the load sensor 1, in units of r / min; n b ″ is the critical speed when the force on load sensor 2 changes to the force on load sensor 1, in r / min; It is the speed of the ball when the ball-disk contact is rolling, in r / min.

[0041] The radius of the disk contact track is therefore:

[0042]

[0043] Where: r b is the radius of the sphere, in m;

[0044] n d n d is the rotation speed of the disk, in r / min.

[0045] The technical solution of the present invention is proposed based on the basic principle that the direction of the drag force will change with the change of the relative sliding and rolling direction. The ball-disc lubricant drag force test bench itself is directly used to test the rotation speed of the ball corresponding to the direction of the drag force jump, so as to determine the contact track radius of the disc. A calibration method is provided for the contact track radius of the test disc of the ball-disc lubricating medium drag force test. This method can effectively overcome the deviation problem caused by the existing method. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a structural schematic diagram of a ball-disc type drag force test disc. DETAILED DESCRIPTION

[0047] Example 1

[0048] A method for calibrating the contact track radius of a ball-disc drag force test disc, the steps comprising:

[0049] (1) Use a micrometer to measure the diameter of the test ball several times, and then determine the radius of the ball according to formula (1):

[0050]

[0051] Where: N is the number of measurements;

[0052] d i is the diameter of the ball measured for the i-th time, in meters.

[0053] (2) First, select a speed n within the allowable speed range of the disk drive servo motor. d Then, the contact radius of the disk track is substituted into formula (2) according to the design value of the test bench to calculate the ball speed n in pure rolling contact (i.e., the sliding-rolling ratio s = 0). bo .

[0054]

[0055] Where: r d ' is the design value of the test bench for the radius of the pan-joined track, in m;

[0056] n d is the rotation speed of the disk, in r / min;

[0057] r b is the radius of the sphere determined by multiple measurements, in meters;

[0058] (3) Turn on the lubrication system to spray lubricating oil to the ball-disc contact area for lubrication, and then perform servo loading to make the ball and disc contact. The contact stress can be any value within the design range of the contact force of the ball-disc testing machine.

[0059] (4) Use the disk drive servo motor servo controller to control the motor at a speed n d The servo controller controls the rotation of the ball and then drives the servo motor to press n bo +Δn b Rotation, Δn b is the large increment of speed, generally a positive integer, such as 5; according to the force values ​​measured by the two pressure sensors, it is judged whether load sensor 2 is under pressure and load sensor 1 is not under pressure. If not, the ball drive motor controller is used to control the ball drive motor speed to increase by Δn b , until load sensor 2 is under pressure and load sensor 1 is not under pressure. Then use the ball drive motor controller to control the ball drive motor speed to decrease by 1r / min, and observe the force values ​​measured by the two load sensors at the same time. When the force jumps from load sensor 2 to load sensor 1, the ball drive motor speed is the critical speed n b ′.

[0060] (5) Then use the disk drive servo motor servo controller to control the motor to rotate at a speed n d The servo controller controls the rotation of the ball and then drives the servo motor to press n bo -Δn b Rotation, Δn b is the speed reduction, which is generally a positive integer, such as 5. According to the force values ​​measured by the two pressure sensors, it is determined whether load sensor 1 is under pressure and load sensor 2 is not under pressure. If not, the ball drive servo motor controller is used to control the ball drive motor speed to reduce Δn. b , until load sensor 1 is under pressure and load sensor 2 is not under pressure. Then use the ball drive motor controller to increase the speed of the ball drive motor by 1r / min, and observe the force values ​​measured by the two load sensors at the same time. When the force jumps from load sensor 1 to load sensor 2, the speed of the ball drive motor is the critical speed n b ″.

[0061] (6) As in formula (3), take two critical speeds n b ′ and n b The average value of ″ is the ball speed when the ball and the disc are rolling in contact.

[0062] (7) The contact track radius of the disk is:

[0063]

Claims

1. A method for calibrating the contact track radius of a ball-disc drag force test disc, characterized in that the steps include: (1) Use a micrometer to measure the diameter of the test ball several times, and then determine the radius of the ball according to formula (1): Where: N is the number of measurements; d i is the diameter of the ball measured for the i-th time, in m; (2) First, select a speed n within the allowable speed range of the disk drive servo motor. d Then, the contact radius of the disk track is substituted into formula (2) according to the design value of the test bench to calculate the ball speed n in pure rolling contact (i.e., the sliding-rolling ratio s = 0). bo : Where: r d ' is the design value of the test bench for the radius of the coiled track, in m; n d is the rotation speed of the disk, in r / min; r b is the radius of the sphere determined by multiple measurements, in meters; (3) Turn on the lubrication system to spray lubricating oil to the ball-disc contact area for lubrication, and then perform servo loading to make the ball and the disc contact. The contact stress can be any value within the design range of the contact force of the ball-disc testing machine. (4) Use the disk drive servo motor servo controller to control the motor at a speed n d The servo controller controls the rotation of the ball and then drives the servo motor to press n bo +Δn b Rotation, Δn b is the large increment of speed, generally a positive integer, such as 5; according to the force values ​​measured by the two pressure sensors, it is judged whether load sensor 2 is under pressure and load sensor 1 is not under pressure. If not, the ball drive motor controller is used to control the ball drive motor speed to increase by Δn b , until load sensor 2 is under pressure and load sensor 1 is not under pressure; then the ball drive motor controller controls the ball drive motor speed to decrease by 1r / min, and observes the measured force values ​​of the two load sensors at the same time. When the force jumps from load sensor 2 to load sensor 1, the ball drive motor speed is the critical speed n b ′; (5) Then use the disk drive servo motor servo controller to control the motor to rotate at a speed n d The servo controller controls the rotation of the ball and then drives the servo motor to press n bo -Δn b Rotation, Δn b is the speed reduction, which is generally a positive integer, such as 5. According to the force values ​​measured by the two pressure sensors, it is determined whether load sensor 1 is under pressure and load sensor 2 is not under pressure. If not, the ball drive servo motor controller is used to control the ball drive motor speed to reduce Δn. b , until load sensor 1 is under pressure and load sensor 2 is not under pressure; then the ball drive motor controller controls the ball drive motor speed to increase by 1r / min, and observes the measured force values ​​of the two load sensors at the same time. When there is a jump from load sensor 1 to load sensor 2, the ball drive motor speed is the critical speed n b ″; (6) As in formula (3), take two critical speeds n b ′ and n b The average value of ″ is the ball speed when the ball and the disc are rolling in contact. (7) The contact track radius of the disk is:

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