Vibration Characteristics and Vibration Reduction of Hinge-type Tilt-shaft Pumps

The vibration characteristics of the hingeless axial-shaft pump and the vibration reduction and suppression of it, Qi Xueyun (Department of Mechanical Engineering, Huainan Institute of Technology, Huainan 232001) The rotational speed of the shaft changed and changed, and it increased with the increase of the swing angle. Torsional vibration is caused by the uneven driving of the cylinder rod by the piston rod, which is strengthened by the biasing moment and causes resonance. Torsional vibration can damage the pump's working performance and reduce its use reliability. Possible measures for vibration reduction were discussed, and the structural principles and design points of a dry friction damper with good damping effect were introduced.

1:A Article ID: The non-hinge inclined-axis pump has the advantages of impact resistance, reliable operation, long life, large swing angle, and strong anti-pollution ability, thus it has been widely used in mines and construction machinery. However, this kind of pump has obvious vibration phenomenon in the work, and the vibration increases with the increase of the swing angle. Vibration damages the pump's performance and reduces reliability. It has also become a major obstacle to the development of large-angle swing pumps with high power density. Therefore, we must fully understand the characteristics and mechanism of the pump vibration, try to reduce vibration and reduce hazards.

In the form of vibration, there is a difference in the angle of rotation between the cylinder and the spindle disc of the inclined shaft pump. During the operation of the pump, this rotation angle changes with the change of the spindle disk rotation angle and the rotation angle difference 4> is the measured change curve of the rotation angle difference of a hingeless inclined shaft pump. During test, the speed of the spindle disk is continuously changed. At the beginning of operation, the difference in rotation angle allowed by the structural clearance between the connecting rod and the inner wall of the plunger (hereinafter referred to as the structure rotation angle difference) immediately follows the operation of the spindle disk, and the rotation angle difference changes according to the hatched boundary of the upper part (). After the increase, the difference in the angle of rotation also increases, and changes in the form indicated by the thick solid line (). As the rotational speed continues to increase, the change in the rotational angle difference increases. When the rotation speed increases to *600i/min, the difference in the rotation angle changes according to the form shown in (b). The cylinder lags behind and sometimes leads the spindle-disc operation with a distinct resonance characteristic. When the rotational speed increases again, the difference in the rotational angle decreases again, and changes according to the thick solid line in (). This change in the rotational angle difference indicates that the cylinder does not follow the spindle disk at a fixed rotational speed, ie, the cylinder produces torsional vibration with respect to the spindle disk 3 Spindle disk rotation angle difference Spindle disk rotation angle difference* (called resonance a The low-speed rotation angle difference and its change are the average amplitude changes of the torsional vibration amplitude of the hingeless inclined-axis pump. From the figure, it can be seen that the average amplitude in the low-speed area is small, and with the increase of the rotation speed, the torsional vibration experiences a comparison. The wide resonant region, with multiple increases and decreases in its value, has no significant periodicity, and this change in amplitude indicates that the cylinder torsional vibration system is a multi-degree-of-freedom system in the form of aperiodic forced torsion. Vibration 3 Rotational speed The pump's structure and motion analysis shows that the cylinder of the inclined shaft pump is toggled by the contact between the connecting rod and the inner wall of the plunger.At each instant, there is only one (or two) connecting rod and column. The inner walls of the plug are in contact with each other and are in working condition. After the current one (or two) connecting rods are out of operation, the rear connecting rod enters the work and there is an interval between the two. The connecting rods entering the work have an impact on the cylinder block. Increase the rotational speed of the cylinder and reduce the rotational angle small.

When the previous connecting rod withdraws from work and the next connecting rod has not been put into operation, the rotational speed of the cylinder decreases, and the difference in the rotational angle increases. The above process will be repeated in the future so that the difference in the rotation angle increases and decreases repeatedly. It can also be seen from the change curve of the speed of the cylinder that there is a sudden change in the rotational speed at the alternate point where the connecting rod enters and exits the work. This shows that the driving of the connecting rod to the cylinder is not uniform, it is this uneven driving that causes the torsional vibration of the cylinder relative to the spindle disk.

From the force analysis of the pump, it can be known that under the action of the plunger pressure, a force F along the axis of the connecting rod will be generated at the hinge point of the connecting rod and the plunger. Because the connecting rod axis has an off angle with respect to the cylinder bore axis. a The force F can be further decomposed into a component force F along the axis of the cylinder bore and a component force Ft along the direction of the tangential line of the cylinder bore distribution circle (see). Ft acts on the cylinder by the plunger, creating a moment opposite to the direction of rotation of the cylinder on the axis of rotation of the cylinder.

Because this moment is caused by the deflection of the connecting rod, it is called the skew moment.

Its production principle is as shown. In the figure, Y is the spindle disc yaw angle, R is the radial distance between the cylinder bore axis and the cylinder axis, the difference in the rotation angle between the cylinder block and the spindle disc, and a is the declination angle of the connecting rod axis with respect to the cylinder bore axis. Spindle disk angle is fluid pressure. The figure shows the situation when the cylinder is lagging. The direction of the biasing moment and the direction of rotation of the cylinder are opposite to each other, so that the difference in the rotation angle tends to increase. When the cylinder forward tilted into a backward X: Hou Bo male 1958 income * 1982 1 Hefei Industrial University, Department of Mechanical Engineering now Huai Nan Industrial Li oblique. The direction of the biasing moment becomes the same as the direction of rotation of the cylinder, which also tends to increase the difference in the angle of rotation. Because the connecting rods have certain elasticity, the connecting rod in working condition will produce bending deformation under the effect of the biasing moment, so that the actual rotation angle difference is greater than the structural corner difference. When the bent connecting rod is withdrawn from operation, the stored elastic energy is released again, and a restoring torque is applied to the cylinder body in the same direction as the rotation.

This moment causes the cylinder to gain the acceleration of the forward acceleration movement, and the rotation angle difference decreases again. If the number of plungers is Z, the above process will repeat 2Z times within one rotation of the cylinder, so that the rotation angle will increase and decrease repeatedly. As a result, the change in the angle of rotation is increased, and the torsional vibration of the cylinder is enhanced, which is an incentive for the cylinder torsion.

The generation of skew moments is not true. The magnitude of the single-link skew moment is: the working pressure of a pump, MPa; a - the declination of the connecting rod; R - the half-angle of the cylinder distribution, m; d - the diameter of the plunger , m. Because of the connecting rod declination angle, "increases with the increase of the oscillating angle of the main shaft disk (or cylinder), resulting in Mp; it also increases as the oscillating angle increases. Therefore, the larger the swing angle, the stronger the effect of Mp on the torsional vibration of the cylinder and the more severe the torsional vibration.

The change period of the skew moment is also the same as the difference in the angle of rotation. When the odd number of plungers is: Cycle angle: 9=n/Z Since all the connecting rods are deflected due to the difference in the angle of rotation, the skew moment acting on the cylinder should be The superposition of Mp produced by the root bar in the pressure zone means that the resulting deflection moment acting on the cylinder increases, and the connecting rod in working state generates a large bending deformation, thus strengthening the The cylinder torsional vibration excitation. From (4), we can see that the frequency of change of Mp is proportional to the spindle disk speed. Therefore, in the process of increasing the speed, when the change frequency of Mp is close to a certain natural frequency of the torsional vibration system of the cylinder, resonance will be aroused.

Although the change of Mp is periodic, the change of the average amplitude does not have periodicity. This shows that the cylinder torsional vibration system is a nonlinear system 3 (with a nonlinear damping force, such as structural damping, friction damping system is a multi-degree-of-freedom system, if the vibration equation is established according to the simplified mechanical model, then the vibration characteristics are solved The parameters will appear to be very complicated and inaccurate, but the shock absorbers are used to generate relative movement between the cylinders, resulting in a friction between the contact surfaces of the two cylinders that is always opposite to the vibration of the cylinders. The resistance torque consumes the energy of the torsional vibration and reduces the amplitude.The magnitude of friction generated is related to the quality of the sleeve and the friction coefficient between the contact surfaces.The friction generated should be greater than the critical value to effectively suppress the internal of the resonant sleeve A wear-resistant bush made of a non-metallic material with a large friction coefficient should be installed to increase the friction, reduce the wear on the cylinder surface, and reduce noise.

The structural principle of the dry friction damper is shown in Figure 4. The township 4 is the comparison of the amplitude change curve before and after the dry friction damper installed in the hingeless axial pump. It can be seen from the figure that when the spindle disk rotates at a high speed of n2000r/min, the vibration reduction effect is poor. This is due to the poor vibration isolation of the friction damper against high frequency vibrations. Therefore, for a large-swing oscillating axial-axis pump equipped with a friction damper, the operating speed should be limited to compensate for the lack of a shock absorber.

Vibration amplitude change curve before (A) and after (B) When the structure design of the pump is performed, various measures described above should be comprehensively used in an effort to obtain the best vibration reduction effect.

4 Conclusions The following conclusions can be drawn from the previous analysis: (1) When the hingeless axial pump is operated, its cylinder will produce acyclically forced torsional vibration. The amplitude varies with the spindle disk speed and increases with the increase of the swing angle. The cylinder torsional vibration system is a multi-degree-of-freedom nonlinear system.

1 Li Changxi. Mining machinery hydraulic transmission. Beijing: Coal Industry Press, 2 Taniguchi (Japan) * Vibration Engineering Encyclopedia. Beijing: Mechanical Industry Press, 3 Ichimachi (Japanese) * Mechanical vibration. Beijing: Science Press, 1974: (Continued from Page) Indicates the feed direction of the stepper motor 5 Subroutines for the control process (parts) Subroutines for the initial feed of position signals 4 Concluding remarks Since PC programming is convenient, The operation is simple and the system development cycle is short. Under the condition that the price of middle and low-end PCs keeps declining, the numerical control system designed in this paper adopts a PC to perform digital control to meet the needs of industrial development; its structure is simple and flexible, and it has certain Value. The test shows that the system has good dynamic response characteristics and the control accuracy can meet the requirements of the crimping parts.

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