2 Abstract In this paper, the sliding shoe pair is divided into kinds of contact modes according to the radius error, and the influence of each contact mode on the static pressure bearing performance is discussed. It is pointed out that the existing calculation model is incomplete due to the neglect of the dimensional error, especially when the error is large.
The friction pair between the connecting rod and the crankshaft is called the key friction pair in the crankshaft connecting rod hydraulic motor. Because of the large contact pressure, there is relative sliding, and the friction and wear are more serious. According to the relevant statistics, the contact on both sides 02, 02 is the half angle of the slider. According to the above method, the mechanical loss occurring here accounts for about 50% of the total mechanical loss of the motor. At present, the sliding shoe pair is designed as a static pressure bearing type, which can theoretically achieve liquid friction. However, the shoe wear phenomenon often occurs in the application. . The existing design method is to equivalent the cylindrical contact to the plane rectangle projected along the axis of the link, and it is considered that the shoe is in an ideal contact state, that is, the thickness of the oil film is equal, which simplifies the analysis and calculation, but Introduce the error on the object model. Machining and assembly errors are unavoidable, although this error is negligible compared to the basic structural dimensions, but is 10,30 compared to the design film thickness of the hydrostatic support, and its effect cannot be ignored.
1The sliding radius of the sliding pair is open, according to the error size, when the oil film has not been formed, there is a possibility that the contact of the sliding shoe pair can be completely contacted = 2; 2 completely = when the pressure oil slides from the plunger cavity When the oil chamber is at the bottom of the block, an oil film is formed between the pair of shoes to indicate the design thickness. The thickness distribution of the oil film under the contact mode can reach the higher order infinity compared with the other two, and can be omitted, so there is the same reason to omit the right side of the equation, there are nine =, 8 +28, The middle item on the right is the effect of radius error on the film thickness distribution.
2 Contact mode The calculation of the color leakage leakage flow of the static pressure bearing performance assumes that the oil is an incompressible fluid, the dynamic viscosity is, the flow between the pair of shoes is laminar, the length of the connecting rod, the motor oil supply pressure is 9, the oil chamber pressure For example, 16 is the angle between the oil chamber and the axial sealing band along the axial direction of the axial seal with the axial seal, and the team can be obtained by the model.
The leakage of the circumferential sealing band is æ¡, the circumferential sealing band gap is changed, the pressure distribution is dp + number for the intermediate contact, the number is used for the contact on both sides, or the pressure distribution is obtained by integrating the upper formula, and the pressure is obtained. After the distribution, the leakage amount of the circumferential sealing band can be obtained. The effect of the frictional torque on the ball joint and the viscous friction force of the oil at the bottom of the slider, the connecting rod tilts around the center of the ball head, when tilting to the side When the side of the block is in contact with the crank surface, the inclination angle of the connecting rod reaches the maximum allowable value. At 5 o'clock, the larger the 5 is, the less the risk of solid friction occurs. The 5-legged style corresponding to the type of contact is given below.
Full contact 2. The maximum inclination angle is calculated as +6+3 into=03. The cosine theorem can be used to find the middle contact of the same heart. There are 3 examples and the relevant parameters of the sliding shoe pair of a crankshaft connecting rod motor are as follows. A curve obtained by a simplified rectangular model is obtained. In the middle contact, since the oil wedge of the circumferential seal band of the slider is in the shape of an outer shape, the pressure drop coefficient is reduced at the same design oil film thickness; when the two sides are in contact, although the circumferential seal oil wedge is convergent The pressure drop is slower, but the thickness of the axial seal with the oil wedge is more significant. The combined result is that the leakage increases, so the pressure drop coefficient is greatly reduced. 4 When the leakage flow and the contact radius of the sliding table are given, the cylindrical model and the simplified rectangular model have good properties. The radius error causes the leakage of the static pressure bearing to increase and the bearing capacity to decrease. It can be seen from 5 that the maximum inclination angle is linear with the film thickness. When the design oil film thickness is the same, the full contact has the same maximum inclination angle as the two sides, and the intermediate contact allows a larger inclination angle of the connecting rod.
4 Conclusion When the sliding shoe pair is ideal contact, the simplified rectangular model and the cylindrical model have good properties. The dimensional error causes the bearing capacity of the sliding shoe secondary static bearing to decrease, which cannot be ignored when the error is large. From the perspective of the anti-rolling performance of the sliding shoe pair, the intermediate contact method is better.
Chen Zhuoru. Theoretical calculation and design of low speed and high torque hydraulic motor. Mechanical Industry Press, 1989 Sheng Jingchao. Hydraulic fluid mechanics. Mechanical Industry Press, 1980 connected to the voltage automatic adjustment circuit of the 27th source, so that the voltage of the DC power supply rises and is output to the two poles of the electrorheological fluid damper, so the viscosity of the electrorheological fluid changes, the electrorheological fluid changes. The damping value increases, and the dynamic stiffness of the main shaft increases, causing the amplitude of the main shaft to decrease. The principle of the spindle amplitude real-time control system is shown in 2.
5 Performance prediction The flutter generated during the cutting process is the main factor affecting the dynamic stability of the machine tool. The main vibration system that generates the flutter is the spindle component of the machine tool. In addition to the reasonable design of the spindle assembly to make it have a high static stiffness, the spindle Adding a damper is an important way to improve the anti-vibration of the main shaft. The use of a damper and amplitude real-time control system is an effective way to control the vibration of the spindle assembly or machine tool. The electro-rheological damper has a large damping range and a fast response. The advantages of good performance are unmatched by other dampers. The damping effect of the electrorheological fluid damper is related to the current-varying effect of the electrorheological fluid and the installation position on the electric field. Reasonable selection of the relevant parameters of the damper and the correct design of the amplitude real-time control system are expected to reduce the machine tool amplitude. An order of magnitude; the electrorheological fluid damper can also be used to eliminate the critical speed of the spindle system. It is advantageous for those spindle systems that need to work above the critical speed to reach their command speed smoothly. For the principle, please refer to Reference 1.
Huang Yijian, etc., current change. Hunan Normal University Press, 19.10 Yang Su, Tang Hengling, Liao Boyu. Machine Tool Dynamics 1. Mechanical Industry Press, 1983.6 Zheng Weizhong. The vibration of the machine tool and its prevention. Science Press, 1981.10 F. Königberg and others. Machine structure. Mechanical Industry Press, Dai Wei. Metal cutting machine tools. Mechanical Industry Press, 1994.10 Huang Changyi, Yan Puqiang. Mechanical, process testing technology foundation. The mechanical industry is Gao Zhongyu, Wang Yongjiang. Mechanical and electrical equipment control engineering. Tsinghua University Press, 1994.9 Received 1999
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