A ball bearing grease life testing machine

Abstract

A ball bearing grease life testing machine includes a loading system, a driving system and a control system. The loading system is connected to a fixture body, and the upper ball is clamped by the chuck of the fixture body. The loading system is used to move the fixture body in space and axially load the lower ball set in the oil box. The driving system is connected to the oil box to drive the oil box to rotate at a set speed. The oil box contains grease and the lower ball set immersed in the grease. The lower ball set includes three lower balls closely adjacent to each other in a triangular pattern and is fixed in the oil box by a pressing and positioning device. The control system includes a controller and a temperature sensor, a load sensor, a rotation speed sensor and a contact friction force sensor that are signal-connected to the controller. The loading system and the driving system are controlled by the controller to operate. The present invention adopts the method of keeping the upper ball stationary and rotating the oil box, reducing the influence of other factors on the measurement of friction force, so that the ultimate life of the grease can be directly obtained according to the change of the friction force.

Description

Technical Field

[0001] The present invention belongs to the field of bearing grease testing, and particularly relates to a ball bearing grease life testing machine. Background Art

[0002] The three main components of grease are base oil, additives, and thickeners. The component with the highest content in grease is the base oil, generally about 75% - 90%. The content of thickeners generally does not exceed one - quarter of the content of the base oil, and the content of additives is the least, almost not exceeding 5% of the total amount or lower. Compared with other components, the selection of the base oil can most significantly affect various properties of the grease. The selection of the thickener directly affects the high - temperature resistance performance of the grease, the stability of the colloid, the water - proof and water - resistance performance, and the stability of the mechanical structure, etc., which is also very important. Generally, adding a small amount of additives and fillers to the grease can improve some properties of the grease.

[0003] Whether the grease can maintain its original volume during operation depends crucially on temperature. If under high - temperature working conditions, the loss and leakage of the grease will be much greater than under normal - temperature working conditions. The reasons for this are as follows: 1. High temperature increases the possibility of oxidation deterioration and condensation of the grease. 2. On the other hand, when the temperature rises, high temperature softens the grease, thereby reducing the adhesion performance of the grease and leading to increased loss and leakage. The evaporation loss of the base oil and the shrinkage of the gel are the two main reasons for the failure of the grease, which shows that the working temperature of the grease is the key factor affecting its failure speed. The adhesion performance of high - temperature - resistant grease will not easily fail even under high - temperature working conditions, which will also slow down the deterioration and failure speed of the grease.

[0004] Currently, the performance of grease is mostly evaluated by the Timken test method and the four - ball machine method. In the four - ball machine method, the upper ball axially loads the three lower balls in the oil box under the action of the main shaft. At the same time, the upper ball rotates, generating friction with the three lower balls below. Then, the three lower balls, together with the oil box as a whole, are affected by the frictional force. The frictional force of the oil box is measured by a tension sensor, and thus the performance of the grease is evaluated through calculation. However, this method has the following problems: 1. One of the key points and difficulties of this method is how to ensure that the center of the upper ball is aligned with the center between the three lower balls during the test process. Since the upper ball needs to axially load the lower balls while rotating, extremely high requirements are imposed on the loading device and the driving and rotating device of the upper ball; 2. During the process of the upper ball rotating and rubbing the lower balls, the frictional force distribution may be uneven, and the frictional force received by the three balls may not necessarily be the frictional force under the loading of the upper ball, but may also be the frictional force of the three lower balls colliding with each other, resulting in the static friction between the lower balls and the oil box becoming dynamic friction, leading to inaccurate measured frictional force in the end.

[0005] In addition, when measuring the service life of ball bearing grease using a four-ball tester, it is also judged based on temperature changes or the tester getting jammed and stopping. However, this method has a response delay, resulting in inaccurate records. Summary of the Invention

[0006] The object of the present invention is to provide a ball bearing grease life tester, which adjusts the transmission layout and loading method of the existing four-ball tester to ensure that the center of the upper ball can be aligned with the center between the three lower balls, and ensure that the friction between the upper ball and the lower ball is only the frictional force generated under loading, reducing the influence of other factors on the measurement of the frictional force. Thus, the ultimate life of the grease can be directly obtained based on the change of the frictional force, providing a reliable basis for improving the high-temperature lubrication performance of the grease, maintaining long-term lubrication work to extend the replacement period, improve productivity and reduce costs, and being beneficial to improving the quality and operating life of ball bearings and meeting the technical requirements of the user unit for the lubrication performance of ball bearings.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a ball bearing grease life tester, including a loading system, a driving system and a control system. The loading system is connected to the fixture body, and the upper ball is clamped by the chuck of the fixture body. The loading system is used to move the fixture body in space and axially load the lower ball group in the oil box. The driving system is connected to the oil box to drive the oil box to rotate at a set speed. The oil box contains grease and the lower ball group immersed in the grease. The lower ball group includes three lower balls closely arranged in a triangular shape, and the lower ball group is fixed in the oil box by a pressing and positioning device. The control system includes a controller and a temperature sensor, a load sensor, a rotation speed sensor and a contact friction sensor signal-connected to the controller. The temperature sensor is used to measure the temperature of the grease, the load sensor is used to measure the axial loading force received by the lower ball group, the rotation speed sensor is used to measure the rotation speed of the oil box, and the contact friction sensor is used to measure the static friction of the upper ball. The loading system and the driving system are controlled by the controller to work.

[0008] The contact friction sensor is arranged between the chuck and the upper ball.

[0009] The load sensor is fixed on the lower surface inside the oil box, and the lower ball group is supported on the load sensor.

[0010] The rotation speed sensor is installed on the fixture body, and the infrared light of the sensor irradiates on the pressing and positioning device of the oil box.

[0011] A heating device is also covered outside the oil box.

[0012] The fixture body and the chuck are threadedly connected. A locking threaded pin for pressing the upper ball against the lower opening of the chuck is arranged inside the chuck. The upper ball exposes from the lower opening of the chuck to contact the lower ball group.

[0013] The pressing and positioning device is a lock nut and a steel ball pressing ring. The steel ball pressing ring is located inside the oil box, and the inner hole of the steel ball pressing ring is a tapered hole that can press on the lower ball set. The lock nut is threadedly connected to the upper opening of the oil box and presses on the upper end face of the steel ball pressing ring. A through hole concentric with the tapered hole is provided on the upper end face of the lock nut, and the diameters of the through hole and the small end of the tapered hole are both larger than the outer diameter of the chuck.

[0014] A oil retaining ring surrounding the through hole is provided on the upper end face of the lock nut.

[0015] The loading system includes a vertical sliding mechanism, a front-back sliding mechanism, and a left-right sliding mechanism. The left-right sliding mechanism is connected to the fixture to drive the fixture to move horizontally left and right. The left-right sliding mechanism is installed on the secondary slider, and the secondary slider moves horizontally forward and backward under the drive of the front-back sliding mechanism. The secondary slider is slidably arranged on the primary slider, and the front-back sliding mechanism is arranged on the primary slider. The primary slider is slidably arranged in the vertical guide groove of the testing machine and is driven to move up and down by the vertical sliding mechanism. The vertical sliding mechanism is arranged on the testing machine body.

[0016] A transverse guide groove is provided on the primary slider, and both the transverse guide groove and the vertical guide groove are dovetail grooves.

[0017] The beneficial effects of the present invention are as follows: 1. Different from the prior art where the oil box remains stationary and the upper ball rotates, in this invention, the upper ball remains stationary and the oil box rotates for the test. By measuring the change in the frictional force on the upper ball, the ultimate life time of the grease under preset temperature, rotation speed, and load can be directly measured. Compared with the indirect calculation in the prior art, it is easier to operate and has fewer interference factors. And compared with directly observing the change in grease temperature or observing the testing machine getting jammed and stopping due to grease failure, this invention has higher accuracy and will not damage the testing machine.

[0018] 2. The six-degree-of-freedom loading device of the present invention can ensure that the fixture can feed with high precision, has good centering and stability with the lower ball set, and can relatively simply achieve the adaptability test of bearing steel balls within a certain size range and the test under temperature, rotation speed, and load conditions within a certain range.

[0019] 3. In the present invention, tests can be carried out on bearing steel balls of different diameters by replacing the chuck, steel ball pressing ring, etc. Also, any kind of grease or lubricating oil can be added to the oil box as the research object, realizing the applicability of grease working condition tests in the full range, which also increases the practicality of the present invention. Description of the Drawings

[0020] Figure 1 It is an overall axonometric view of the testing machine described in the present invention;

[0021] Figure 2Schematic diagram of the overall structure of the testing machine described in the present invention;

[0022] Figure 3 Schematic diagram of the drive system of the testing machine described in the present invention;

[0023] Figure 4 Schematic diagram of the loading system of the testing machine described in the present invention;

[0024] Figure 5 Schematic diagram of the main test part of the testing machine described in the present invention;

[0025] Figure 6 Horizontal sectional view of the structure of the first - stage slider in the testing machine described in the present invention;

[0026] Markings in the figure: 1 - machine housing; 2 - rolling bearing; 3 - base; 4 - vertical guide groove; 5 - lead screw a; 6 - chuck; 7 - locking threaded pin; 8 - fixture body; 9 - lead screw c; 10 - second - stage slider; 11 - lead screw b; 12 - first - stage slider; 13 - coupling a; 14 - motor frame; 15 - stepper motor a; 16 - rotational speed sensor; 17 - stepper motor c; 18 - oil baffle ring; 19 - upper ball; 20 - contact friction force sensor; 21 - locking nut; 22 - steel ball pressing ring; 23 - lower ball set; 24 - heating device; 25 - platinum resistance temperature sensor; 26 - load cell; 27 - oil box; 28 - turntable; 29 - turntable bracket; 30 - servo motor; 31 - driven wheel; 32 - synchronous belt; 33 - driving wheel; 34 - motor base plate; 100 - clearance adjusting ring; 101 - coupling b; 102 - stepper motor b; 103 - tapered roller bearing. Detailed implementation manners

[0027] The present invention will be further described in detail below in conjunction with the drawings and embodiments, but it shall not be used as a basis for any limitation to the invention.

[0028] Refer to the attached Figure 1 As shown, a ball - bearing grease life testing machine mainly consists of three major parts: a drive system, a loading system, and a PLC control system. The three major parts are arranged inside the testing machine body composed of a machine housing 1 and a base 3.

[0029] As Figure 2 、 3 shown, the drive system mainly includes a turntable 28, a turntable bracket 29, a servo motor 30, a driven wheel 31, a synchronous belt 32, a driving wheel 33, a motor base plate 34, and a tapered roller bearing 103.

[0030] The servo motor 30 is connected to the driving wheel 33. The driving wheel 33 is connected to the driven wheel 31 through a synchronous belt 32. The driven wheel 31 is connected to the turntable 28 by bolts. An oil box 27 is fixedly installed on the turntable 28. The oil box 27 contains the grease for the test and the lower ball set 23 in the grease. To ensure the stable rotation of the turntable 28, a turntable bracket 29 and a tapered roller bearing 103 are provided to support the rotation of the turntable 28, so that it does not generate radial vibration and has good rotational centering. The servo motor 30 and the turntable bracket 29 are both supported by columns on the motor base plate 34, and the motor base plate 34 is fixed on the base 3 of the machine body. This part mainly drives the oil box 27 to rotate, so that the lower ball set 23 and the upper ball 19 in the oil box 27 can generate contact friction with the grease between them.

[0031] The servo motor 30 can control the rotation speed and direction of the turntable 28, and the rotation speed range is 200 rpm to 8000 rpm.

[0032] As Figure 5 shown, a steel ball pressing ring 22 is arranged in the oil box 27 and presses on the outer sides of the three lower balls of the lower ball set 23. The locking nut 21 is connected to the oil box 27 by threads and presses down on the steel ball pressing ring 22, and the lower ball set 23 is pressed by the steel ball pressing ring 22. At the same time, an annular groove is provided on the upper end surface of the locking nut 21, and the oil retaining ring 18 is press-fitted in the annular groove to prevent the lubricant in the oil box 27 from splashing.

[0033] The oil box 27 is filled with grease, and the amount of the grease should just immerse the three steel balls of the lower ball set 23, so that there is grease between the upper ball and the three steel balls, so as to achieve the test purpose.

[0034] As Figure 2 、 4 shown, the shown loading system mainly includes: a vertical guide groove 4, a lead screw a5, a stepping motor a15, a chuck 6, a locking threaded pin 7, a chuck body 8, an upper ball 19, a lead screw c9, a secondary slider 10, a stepping motor c17, a lead screw b11, a primary slider 12, and a stepping motor b102.

[0035] As Figure 2 、 4As shown in , 5 and 6, the vertical guide groove 4 is provided on the inner wall of the casing 1, and the vertical guide groove 4 is a dovetail groove. The first-level slider 12 is provided with a dovetail tenon that slides with the vertical guide groove 4. The first-level slider 12 moves up and down along the vertical guide groove 4 under the drive of the corresponding driving device; a transverse guide groove is provided on the lower surface of the first-level slider 12, and the transverse guide groove is also a dovetail groove. The second-level slider 10 is slidably connected to the transverse guide groove through the provided dovetail tenon. The direction of the transverse guide groove is the front-to-back direction, and the second-level slider 10 moves horizontally along the transverse guide groove Move back and forth; a left and right driving device is set at the lower part of the secondary slider 10, which is used to drive the clamp body 8 to move horizontally left and right. The chuck 6 is installed on the clamp body 8, and the upper ball 19 is installed in the chuck 6. Therefore, driven by the first slider 12, the secondary slider 10 and the clamp body 8, the chuck 6 and the upper ball 19 can move in six degrees of freedom, up and down, front and back, left and right, to achieve alignment with the centers of the three steel balls of the lower ball group 23 in the oil box 27, axial loading of the lower ball group 23, and adjustment and maintenance of the loading force. The loading load range of the loading system is 0.5N~1000N.

[0036] Specifically, the up and down movement of the primary slider 12 is achieved by a lead screw a5, which passes through the primary slider 12 and is threadedly connected thereto. The upper end of the lead screw a5 is connected to a stepper motor a15 via a coupling a13, and the lower end is connected to a rolling bearing 2 within the base 3. The stepper motor a15 is mounted on a motor frame 14, which is fixed to the upper end of the inner wall of the housing 1. To reduce frictional resistance between the slider and the guide rail groove, lubricating oil is applied to the mating surfaces of the primary slider 12 and the vertical guide rail groove 5.

[0037] Specifically, support plates are fixed at both ends of the transverse guide groove in the first-level slider 12, and a stepper motor b102 and a lead screw b11 are installed on the support plates. The stepper motor b102 is connected to the lead screw b11 through a coupling b101. The lead screw b11 passes through the secondary slider 10 and is threadedly connected to the secondary slider 10. The stepper motor b102 drives the lead screw b11 to rotate, driving the secondary slider 10 to slide along the transverse guide groove. Lubricating oil is set on the mating surface of the secondary slider 10 and the transverse guide groove to reduce sliding friction resistance.

[0038] Specifically, a stepper motor c17 and a lead screw c9 connected thereto are installed at the lower part of the secondary slider 10. The lead screw c9 passes through the clamp body 8 and is threadedly connected to the clamp body 8. In the space, the lead screw c9 is perpendicular to the transverse guide groove, so that the lead screw c9 can drive the clamp body 8 to move horizontally left and right.

[0039] The fixture 8 is threadedly connected to the positioning sleeve on the upper part of the chuck 6. The chuck 6 is mainly used to clamp the upper ball 19 so that it will not displace during frictional movement. A locking threaded pin 7 is also provided inside the chuck 6. The locking threaded pin 7 presses the upper ball 19 against the opening at the front end of the chuck 6, thereby further clamping the upper ball 19. After the upper ball 19 is clamped in the chuck 6, the lower part of the upper ball 19 exposes the opening at the front end of the chuck 6 for contact and friction with the lower ball set 23. In order to buffer the influence of the friction force of the steel ball, a clearance adjustment collar 100 is installed on the locking threaded pin 7, and the clearance between the locking threaded pin 7 and the inner wall of the chuck 6 can also be filled.

[0040] Through the loading system, the chuck 6 and the upper ball 19 can be moved up and down, back and forth, and left and right, so as to align with the centers of the three steel balls of the lower ball set 23 in the oil box 27, axially load the lower ball set 23, and adjust and maintain the loading force.

[0041] The PLC control system of the testing machine of the present invention includes a PLC, a temperature control system, a sensing system, a timing system, and a human-machine interaction control interface.

[0042] As Figure 5 shown, the sensing system includes a platinum thermal resistance temperature sensor 25, a rotational speed sensor 16, a contact friction force sensor 20, and a load cell 26. The platinum thermal resistance sensor 25 is connected to the oil box 27, and the probe of the platinum thermal resistance sensor 25 extends into the interior of the oil box 27 to sense the temperature of the grease in the box; the rotational speed sensor 16 is placed on the outer wall side of the fixture 8, and the infrared light of the sensor is aligned with the upper end face of the locking nut 21 to measure the rotational speed of the oil box 27; the contact friction force sensor 20 is placed at the contact position between the chuck 6 and the upper ball 19, that is, any change in the frictional load received by the upper ball 19 can be sensed and measured by the contact friction force sensor 20; the load cell 26 is threadedly connected to the inner lower surface of the oil box 27 and contacts the three steel balls of the lower ball set 23. While the stepping motor a15 of the loading system loads the lower ball set 23 through the upper ball 19 clamped by the fixture 8, it also loads the load cell 26. At this time, the load cell 26 senses the load change to measure the loading pressure, and then feeds back to the control system to precisely control the stepping motor a15.

[0043] The temperature control system mainly includes a heating device 24 for heating the oil box 27. The heating device uses a heating plate and a stainless steel sleeve heating coil. The heating plate is padded under the bottom of the oil box 27, and the stainless steel sleeve heating coil is wrapped around the outer wall of the oil box 27. The temperature of the grease in the oil box 27 can be controlled by controlling the heating of the two. The rated voltage of the heating plate and the stainless steel sleeve heating coil is 220V, and their rated power during normal operation is 400W, and the temperature control range is 15°C to 250°C.

[0044] The timing system is used to control the running time of the servo motor 30, the heating time of the temperature control system, and to time, so as to obtain the relationship between time and temperature rise, rotational speed, and load strain force, and further obtain the analysis of the life parameters of the lubricant.

[0045] The human-machine interaction control interface is the visual operation control of each system on the software platform, and the operator can perform quantitative operation control on the above systems here.

[0046] Example 2: When using the testing machine of the present invention to test the life of ball bearing grease, first, after the grease is filled in the upper ball 19, the lower ball set 23, and the oil box 27, the three stepping motors of the loading system of the testing machine are started simultaneously, and the clamping body 8 is driven to move through the screw drive, so that the upper ball 19 clamped by the chuck 6 is accurately located directly above the lower ball set 23, and the center of the connection line between the center of the upper ball 19 and the centers of the three lower balls is aligned. The stepping motor a15 starts to load and feed downward, and the upper ball 19 contacts and rubs against the lower ball set 23 until the load data transmitted by the load sensor 26 reaches the preset value, and then the motor loading is stopped; secondly, the servo motor 30 of the driving system of the testing machine is started, and the turntable 28 and the oil box 27 are driven to rotate to the preset rotational speed through the transmission of the synchronous belt. At this time, the oil box 27 drives the lower ball set 23 and the upper ball 19 to have sliding friction, and the time node at this time is recorded as the initial time point; during the sliding friction process of the upper ball 19 and the lower ball set 23, each sensor of the testing machine runs simultaneously. The platinum resistance temperature sensor 25 measures the real-time value of the temperature of the grease in the oil box 27 to monitor and feedback to the temperature control system; the rotational speed sensor 16 measures the rotational speed of the locking nut 21, that is, the oil box 27, through infrared light to monitor and feedback to the frequency conversion system to control the rotational speed; the load sensor 26 senses the load applied by the loading system to the lower ball set 23; the contact friction force sensor 20 senses the change in the friction force generated by the contact friction between the upper ball 19 and the lower ball set 23 in real time to monitor and feedback to the human-machine interaction interface; the timing system records the time nodes of the test process according to the set regular interval time. Since under normal lubrication conditions of the grease, the friction force between the upper ball 19 and the lower ball set 23 will not fluctuate greatly and is relatively stable, and when the lubricity of the grease significantly decreases resulting in insufficient lubrication, the friction force of the lower ball set 23 on the upper ball 19 will suddenly increase. Therefore, during the test process, observe the change in the friction force sensed by the contact friction force sensor in the human-machine interaction interface. If the friction force suddenly increases at a certain time point, record this time point, and the time difference between this time point and the initial time point is the ultimate life time of the grease.

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Those of ordinary skill in the art should understand that the specific implementation manners of the present invention can be modified or equivalently replaced by referring to the above embodiments. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention is within the scope of the claims pending for approval.

Claims

1. A ball bearing grease life tester, comprising a loading system, a drive system, and a control system, characterized in that: The loading system is connected to the clamping body, and the upper ball is clamped by the clamping head of the clamping body. The loading system is used to move the clamping body in space and axially load the lower ball group in the oil box; the driving system is connected to the oil box to drive the oil box to rotate at a set speed. The oil box contains grease and a lower ball group immersed in the grease. The lower ball group includes three lower balls that are close together in a herringbone shape, and the lower ball group is fixed in the oil box by a clamping positioning device; the control system includes a controller and a temperature sensor, a load sensor, a speed sensor and a contact friction sensor connected to the controller signal. The temperature sensor is used to measure the grease temperature, the load sensor is used to measure the axial loading force on the lower ball group, the speed sensor is used to measure the oil box speed, and the contact friction sensor is used to measure the static friction of the upper ball. The loading system and the driving system are controlled by the controller; The clamp body is threadedly connected to the clamp head, and a locking threaded pin is provided in the clamp head for tightening the upper ball to the lower opening of the clamp head. The upper ball is exposed from the lower opening of the clamp head and contacts the lower ball group. The contact friction force sensor is provided between the clamp head and the upper ball.

2. A ball bearing grease life testing machine according to claim 1, characterized in that: The load sensor is fixed on the lower surface of the oil box, and the lower ball group is supported on the load sensor.

3. The ball bearing grease life testing machine according to claim 1, characterized in that: The rotation speed sensor is mounted on the clamp body, and the infrared light of the sensor is irradiated on the pressing and positioning device of the oil box.

4. The ball bearing grease life testing machine according to claim 1, characterized in that: The oil box is also covered with a heating device.

5. The ball bearing grease life testing machine according to claim 1, characterized in that: The clamping and positioning device is composed of a locking nut and a steel ball pressure ring. The steel ball pressure ring is located in the oil box. The inner hole of the steel ball pressure ring is a tapered hole that can be pressed on the lower ball group. The locking nut is threadedly connected to the upper opening of the oil box and is pressed on the upper end face of the steel ball pressure ring. The upper end face of the locking nut is provided with a through hole concentric with the tapered hole. The aperture of the through hole and the diameter of the small end of the tapered hole are both larger than the outer diameter of the chuck.

6. A ball bearing grease life testing machine according to claim 5, characterized in that: An oil retaining ring surrounding the through hole is provided on the upper end surface of the locking nut.

7. The ball bearing grease life testing machine according to claim 1, characterized in that: The loading system includes a vertical sliding mechanism, a front-back sliding mechanism and a left-right sliding mechanism; the left-right sliding mechanism is connected to the clamping body to drive the clamping body to move horizontally left and right; the left-right sliding mechanism is installed on the secondary slider, and the secondary slider moves horizontally back and forth under the drive of the front-back sliding mechanism. The secondary slider is slidably arranged on the primary slider, and the front-back sliding mechanism is arranged on the primary slider; the primary slider is slidably arranged in the vertical guide rail groove of the testing machine, and is driven up and down by the vertical sliding mechanism, and the vertical sliding mechanism is arranged on the testing machine body.

8. The ball bearing grease life testing machine according to claim 7, characterized in that: A transverse guide groove is provided on the first-level sliding block, and both the transverse guide groove and the vertical guide groove are dovetail grooves.

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