CN103352917B - Integrated type air-float guide rail under unbalance loading etc. gap design method - Google Patents

Abstract

The invention relates to the technical field of air-floating guide rails, in particular to an equal clearance design method for integral air-floating guide rails under eccentric loads. The invention aims to overcome the problems of low guiding precision and poor stability of the guide rail under partial load in the prior art. In order to overcome the problems existing in the prior art, the technical solution provided by the present invention is: a design method for equal clearance of the integral air-floating guide rail under partial load, which is characterized in that: changing the inner diameter of each orifice to realize the alignment of the guide rail Leveling due to deflection angle caused by eccentric load. Compared with the prior art, the advantage brought by the method of the present invention is that the motion error caused by the eccentric load with the guide rail in the vertical direction is eliminated in design theory, that is, there is only manufacturing error, compared with the prior art In terms of performance, the present invention has high operating precision and good stability.

Description

Equal clearance design method of integral air bearing guide rail under eccentric load

technical field

The invention relates to the technical field of air-floating guide rails, in particular to an equal clearance design method for integral air-floating guide rails under eccentric loads.

Background technique

When assembling moving guide rails with multiple air bearing pads, the air bearing pads are supported by ball joints, so that the balance position can be self-aligned and the air film gaps are kept equal. However, a carriage is required, and the moving guide rails are large in size and have a small carrying capacity. . When the integral guide rail is used to assemble the moving guide rail, the moving guide rail has a small volume and a large carrying capacity, and the more parallel the working gap of the integral air bearing guide rail is, the higher the running accuracy is. However, in the actual work process, it is found that the existing integral air-floating guide rails still have the following problems: due to the effect of load or inertial force, the integral air-floating guide rails will inevitably produce unbalanced loads during use. If the gap is equal, the eccentric load will inevitably lead to unequal gaps in the guide rails, which will affect the running accuracy. And because the thickness of the air film is very small, a small deflection angle may cause scratches, affect the stability of the bearing, and reduce the service life of the bearing. In the past, the design method for the integral air bearing guideway was to supply the air film with equal inner diameter orifices. Such a design method would inevitably cause deflection problems during the operation of the guideway, reducing the running accuracy and stability of the guideway.

Contents of the invention

The present invention provides an equal clearance design method for an integral air-floating guide rail under eccentric loads, so as to overcome the problems of low running precision and poor stability of the guide rail in the prior art.

In order to overcome the problems existing in the prior art, the technical solution provided by the present invention is: an equal clearance design method of an integral air-floating guide rail under partial load, which is characterized in that the inner diameter of each orifice is changed to realize the adjustment of the guide rail due to The deflection angle brought by the eccentric load is leveled. the

The equal-gap design method of the above integral air-floating guide rail under partial load includes the following steps:

1. Taking the plane of the long guide rail as the XY coordinate plane to calculate the outlet pressure of each orifice of the air-floating guide rail under the eccentric load state, the bearing capacity of the gas film, and the moment of the gas pressure of the gas film to the X-axis and to the Y-axis;

2. Using the Reynolds equation and heavy integrals, calculate the gas film bearing capacity and the moment of gas on the X-axis and Y-axis under the equal gap state;

3. Taking the gas film bearing capacity and eccentric load moment in the equal clearance state as the convergence condition as the non-equal clearance state, adjust the orifice outlet pressure to obtain a set of orifice outlet pressure values that meet the convergence conditions;

4. Select the inner diameter of the original orifice as the initial value of the inner diameter of the orifice after leveling, divide the XY plane into multiple areas according to the number of orifices, and use the gas flow conservation equation to perform nested coupling respectively, that is, to satisfy each The convergence condition is that the gas flow in and out of the area is equal and the total gas flow in and out of the entire gas film is equal. If the gas flow in and out of a certain area is not conserved during the calculation process, the inner diameter of the orifice is adjusted in small steps until the convergence condition is met.

In the above step 2, when the thickness of the air film after the guide rail is adjusted to equal clearance is required to be the thickness of the center point of the stress slope before adjustment, in the above step 3, when adjusting the initial value of the orifice outlet pressure, increase the corresponding position at the same time The orifice outlet pressure at which the gas film thickness becomes higher and the orifice outlet pressure value at the corresponding position where the gas film thickness becomes lower are obtained to obtain a set of orifice outlet pressure values that satisfy the torque convergence condition and meet the thickness requirements.

In the above step 3, the outlet pressure of the orifice is adjusted to meet the torque convergence condition. When the obtained set of data meets the torque convergence requirement but not the bearing capacity convergence requirement, the The orifice outlet pressure value is added or subtracted to change the bearing capacity, and then return to readjust the torque convergence, and so forth, to a set of orifice outlet pressure values, so that the torque and bearing capacity meet the convergence.

When increasing or decreasing the outlet pressure value above, choose an unequal step size for each orifice, that is, the step size of the outlet pressure of each orifice is given according to the proportional relationship between the change of the gas film thickness at the corresponding position .

In the above step 2, it is not required that the thickness of the gas film after the guide rail is adjusted to equal clearance is the thickness of the center point of the stressed slope under the partial load state, that is, the initial value of the gas film thickness can be higher or lower than the value of the center point thickness of the original inclined bearing surface , in step 3, adjust the outlet pressure values of all orifices at the same time, or only adjust the outlet pressure of the orifice with a larger increase in the corresponding gas film thickness at some orifice positions to meet the convergence condition of the torque.

In the above step 3, when adjusting the outlet pressure values of all orifices at the same time, the specific method is to first adjust the outlet pressure of the orifice to meet the torque convergence condition. Small step adjustment, change the bearing capacity, and then return to readjust the torque convergence, in this way, a set of orifice outlet pressure values can be obtained, so that the torque and bearing capacity meet the convergence.

Compared with the prior art, the advantages of the present invention are: using the method of the present invention, there is no movement error generated in the vertical direction of the guide rail in theory, and even due to processing reasons, only a very small error will be produced, relatively Compared with the prior art, the present invention has high operating precision and good stability.

Description of drawings

Figure 1 is a schematic diagram of an eccentric load bearing surface of the integral air bearing guide rail in the non-equal gap state;

Figure 2 is a schematic diagram of the force-bearing surface of the equal-gap air-floating guide rail obtained after adjustment.

Detailed ways

In the prior art, after the integral air-floating guide rail bears an eccentric load, the gap between the guide rails will be unequal, thereby affecting the working accuracy. Due to the small thickness of the air film, a small deflection angle may cause scratches and affect the stability of the bearing. The principle of the present invention is as follows: if a pre-deflection angle can be added to the guide rail, the deflection angle generated by the eccentric load of the guide rail during the working process can be offset to restore the parallel or equal gap state, and the stability and working accuracy can be improved. The equal clearance design principle of the integral air bearing guideway is to aim at the equal clearance of the integral air bearing guideway. Under the control of the Reynolds equation and through the principle of mass conservation, find a set of orifice diameters that meet the target and meet the constraints.

The present invention will be described in detail below with reference to the drawings and embodiments.

Embodiment 1: The design method of the equal clearance of the integral air-floating guide rail under partial load, including the following steps:

step one:

When the 8-throttle integrated air bearing guide rail is subjected to an eccentric load, it will produce a deflection angle as shown in Figure 1. The eccentric load of the air bearing guide rail can be simplified as the resultant force F of the center point of the inclined plane, and the eccentric load moment Mx of the two coordinates , My. In the figure, n1 and n2 are the normals of the two slopes, and the included angle is , which is the declination angle to be discussed in this article. It can be seen from the figure that the external load is perpendicular to the slope, not vertically downward. Therefore, F can be decomposed into the resultant force of horizontal force and vertical force Fz. The horizontal force will not produce an eccentric load here, therefore, to offset the eccentric load and make the guide rail return to the level, only the vertical force Fz can be discussed. It can be seen from statics that the bearing capacity provided by the air film pressure should be equal to Fz. And the total torque of the gas pressure on the X-axis and the Y-axis should be equal to Mx and My respectively. Using the continuous condition determined by the principle of gas mass conservation, the X and Y planes are divided into 8 areas according to the positions of 8 orifices. By nesting and coupling the flow balance of the gas in and out of the 8 areas, the throttling under partial load can be calculated. The outlet pressure of the hole can be obtained by the Reynolds equation to obtain the pressure distribution under eccentric load. Points can get Fz, Mx, My.

Step two:

When it is required that the air film thickness of the air-floating guide rail is adjusted to the equal clearance to be the thickness of the center point of the long guide rail under the eccentric load state, then the thickness is the same after the equal clearance is adjusted, as shown in Figure 2. Apply this thickness as a constant in the Reynolds equation, assign the outlet pressure value of each orifice obtained when there is a deflection angle to the corresponding orifice outlet pressure after equal clearance and leveling to calculate the gas pressure distribution at this time, and calculate this by integral When air film bearing capacity F1 and eccentric load moment Mx1, My1.

Step three:

After equal clearance leveling, except for the thickness of the center point of the plane, the thickness of the gas film at other positions changes, which will inevitably lead to changes in the pressure distribution. At this time, F1, Mx1, and My1 must not be equal to Fz, Mx, and My in the non-equal gap state. At this time, different step lengths can be given to each orifice according to the variation of the gas film thickness at the position of each orifice, and the outlet pressure of each orifice can be adjusted at the same time. That is, increase the outlet pressure of the orifice where the gas film thickness at the corresponding position becomes higher, and decrease the outlet pressure of the orifice where the gas film thickness becomes lower at the corresponding position. Thus the convergence condition that the two moments Mx1, My1 are equal to the two moments Mx, My when the gap is not equal is achieved.

Calculate F1 based on the orifice outlet pressure obtained at this time, and compare it with Fz under the condition that F1 and Fz are equal. If F1 is less than Fz, increase the outlet pressure of 8 orifices at the same time with equal steps. to increase F1; if F1 is greater than Fz, reduce the outlet pressure of 8 orifices at the same time with equal steps, and then calculate Mx1 and My1 with the increased outlet pressure, and readjust the outlet pressure of the orifice to make Mx1 , My1 reach the convergence condition, repeat this cycle, and finally obtain a set of orifice outlet pressure values that make Mx1, My1, and F1 all meet the convergence condition after adjustment.

Step four:

The outlet pressure values of the 8 orifices obtained in Step 3 can be used to obtain the pressure distribution at this time through the Reynolds equation. Select the inner diameter of the original orifice as the initial value of the inner diameter of the orifice after leveling, divide the XY plane into 8 areas according to the number of orifices, to ensure that each area has only one orifice, and then use the gas in each area The inflow and outflow gas flow is equal to the convergence condition, and the inner diameter of each orifice is adjusted. That is, if the inflow flow rate of the area is greater than the outflow flow rate, the inner diameter value will be reduced in small steps; if the inflow flow rate is smaller than the outflow flow rate, the inner diameter value will be increased in a small step size until the inflow and outflow gas flow rates are equal. In this way, a set of inner diameter values of the orifice can be obtained, which can satisfy the equal clearance of the air film thickness.

Embodiment 2, the equal clearance design method of the integral air-floating guide rail under partial load, includes the following steps:

step one:

When the 8-throttle integrated air bearing guide rail is subjected to an eccentric load, it will produce a deflection angle, which can simplify the eccentric load of the air bearing guide rail to the resultant force F of the center point of the inclined plane, and the eccentric load moments Mx, My of the two coordinates. In the figure, n1 and n2 are the normals of the two slopes, and the included angle is , which is the declination angle to be discussed in this article. It can be seen from the figure that the external load is perpendicular to the slope, not vertically downward. Therefore, F can be decomposed into the resultant force of horizontal force and vertical force Fz. The horizontal force will not produce an eccentric load here, therefore, to offset the eccentric load and make the guide rail return to the level, only the vertical force Fz can be discussed. It can be seen from statics that the bearing capacity provided by the air film pressure should be equal to Fz. And the total torque of the gas pressure on the X-axis and the Y-axis should be equal to Mx and My respectively. Using the continuous condition determined by the principle of gas mass conservation, the X and Y planes are divided into 8 areas according to the positions of 8 orifices. By nesting and coupling the flow balance of the gas in and out of the 8 areas, the throttling under partial load can be calculated. The outlet pressure of the hole can be obtained by the Reynolds equation when the pressure distribution is eccentrically loaded, and the integral can be used to obtain Fz, Mx, My.

Step two:

When the air bearing guide rail is not required to be adjusted to equal clearance, the thickness of the air film is the thickness of the center point of the long guide rail under the partial load state, that is, the initial value of the air film thickness can be higher or lower than the value of the center point thickness of the original inclined bearing surface. Apply this thickness as a constant in the Reynolds equation, assign the outlet pressure value of each orifice obtained when there is a deflection angle to the corresponding orifice outlet pressure after equal clearance and leveling to calculate the gas pressure distribution at this time, and calculate this by integral When air film bearing capacity F1 and eccentric load moment Mx1, My1.

Step three:

After equal clearance leveling, except for the thickness of the center point of the plane, the thickness of the gas film at other positions changes, which will inevitably lead to changes in the pressure distribution. At this time, F1, Mx1, and My1 must not be equal to Fz, Mx, and My in the non-equal gap state. At this time, different step lengths can be given to each orifice according to the variation of the gas film thickness at the position of each orifice, and the outlet pressure of each orifice can be adjusted at the same time. That is, increase the outlet pressure of the orifice where the gas film thickness at the corresponding position becomes higher, and decrease the outlet pressure of the orifice where the gas film thickness becomes lower at the corresponding position. Thus the convergence condition that the two moments Mx1, My1 are equal to the two moments Mx, My when the gap is not equal is achieved.

Calculate F1 based on the orifice outlet pressure obtained at this time, and compare it with Fz under the condition that F1 and Fz are equal. If F1 is less than Fz, increase the outlet pressure of 8 orifices at the same time with equal steps. to increase F1; if F1 is greater than Fz, reduce the outlet pressure of 8 orifices at the same time with equal steps, and then calculate Mx1 and My1 with the increased outlet pressure, and readjust the outlet pressure of the orifice to make Mx1 , My1 reach the convergence condition, repeat this cycle, and finally obtain a set of orifice outlet pressure values that make Mx1, My1, and F1 all meet the convergence condition after adjustment.

Step four:

The outlet pressure values of the 8 orifices obtained in Step 3 can be used to obtain the pressure distribution at this time through the Reynolds equation. Select the inner diameter of the original orifice as the initial value of the inner diameter of the orifice after leveling, and divide the XY plane into 8 areas according to the number of orifices to ensure that each area has only one orifice. The inflow and outflow gas flow is equal to the convergence condition, and the inner diameter of each orifice is adjusted. That is, if the inflow flow rate of the area is greater than the outflow flow rate, then reduce the inner diameter value in small steps; if the inflow flow rate is smaller than the outflow flow rate, increase the inner diameter value in small step sizes until the inflow and outflow gas flow rates are equal. In this way, a set of inner diameter values of the orifice can be obtained, which can satisfy the equal clearance of the air film thickness.

Example 3:

The equal-gap design method of integral air-floating guide rail under partial load is characterized by the following steps:

1. Taking the plane of the long guide rail as the XY coordinate plane to calculate the outlet pressure of each orifice of the air-floating guide rail under the eccentric load state, the bearing capacity of the gas film, and the moment of the gas pressure of the gas film to the X-axis and to the Y-axis;

2. Using the Reynolds equation and heavy integrals, calculate the bearing capacity of the air film and the moment of the gas on the X-axis and Y-axis in the state of equal clearance: it is not required that the thickness of the air film after the guide rail is adjusted to the equal clearance is the force slope under the partial load state When the center point thickness is used, that is, the initial value of the air film thickness can be higher or lower than the value of the center point thickness of the original inclined bearing surface;

3. Taking the air film bearing capacity and eccentric load moment in the equal clearance state as the convergence condition as the non-equal clearance state, adjust the outlet pressure of the orifice to obtain a set of orifice outlet pressure values that meet the convergence conditions: adjust at the same time The outlet pressure values of all orifices meet the convergence conditions of the torque. The specific method of adjustment at the same time is to adjust the outlet pressure of the orifices to meet the convergence conditions of the torque. When a set of data obtained does not meet the convergence requirements of the bearing capacity, the Adjust the thickness in small steps, change the bearing capacity, and then return to readjust the torque convergence, and reciprocate in this way, a set of orifice outlet pressure values can be obtained, so that the torque and bearing capacity meet the convergence;

4. Select the inner diameter of the original orifice as the initial value of the inner diameter of the orifice after leveling, divide the XY plane into multiple areas according to the number of orifices, and use the gas flow conservation equation to perform nested coupling respectively, that is, to satisfy each The convergence condition is that the gas flow in and out of the area is equal and the total gas flow in and out of the entire gas film is equal. If the gas flow in and out of a certain area is not conserved during the calculation process, the inner diameter of the orifice is adjusted in small steps until the convergence condition is met.

Example 4:

The equal-gap design method of integral air-floating guide rail under partial load is characterized by the following steps:

1. Taking the plane of the long guide rail as the XY coordinate plane to calculate the outlet pressure of each orifice of the air-floating guide rail under the eccentric load state, the bearing capacity of the gas film, and the moment of the gas pressure of the gas film to the X-axis and to the Y-axis;

2. Using the Reynolds equation and heavy integrals, calculate the bearing capacity of the air film and the moment of the gas on the X-axis and Y-axis in the state of equal clearance: it is not required that the thickness of the air film after the guide rail is adjusted to the equal clearance is the force slope under the partial load state When the center point thickness is used, that is, the initial value of the air film thickness can be higher or lower than the value of the center point thickness of the original inclined bearing surface;

3. Taking the air film bearing capacity and eccentric load moment in the equal clearance state as the convergence condition as the non-equal clearance state, adjust the outlet pressure of the orifice to obtain a set of orifice outlet pressure values that meet the convergence conditions: only adjust Part of the orifice position corresponding to the gas film thickness increases a lot to meet the convergence condition of the torque. When a set of data obtained does not meet the bearing capacity convergence requirements, the gas film thickness is adjusted in small steps, changing Bearing capacity, and then return to readjust the torque convergence, and reciprocate in this way, a set of orifice outlet pressure values can be obtained, so that the torque and bearing capacity meet the convergence;

4. Select the inner diameter of the original orifice as the initial value of the inner diameter of the orifice after leveling, divide the XY plane into multiple areas according to the number of orifices, and use the gas flow conservation equation to perform nested coupling respectively, that is, to satisfy each The convergence condition is that the gas flow in and out of the area is equal and the total gas flow in and out of the entire gas film is equal. If the gas flow in and out of a certain area is not conserved during the calculation process, the inner diameter of the orifice is adjusted in small steps until the convergence condition is met.

Claims (6)

1. A method for equal clearance design of an integral air-floating guide rail under eccentric load, by changing the inner diameter of each orifice to achieve leveling the deflection angle of the guide rail due to eccentric load, characterized in the following steps: 1. Taking the plane of the long guide rail as the XY coordinate plane to calculate the outlet pressure of each orifice of the air-floating guide rail under the partial load state, the bearing capacity of the gas film, and the moment of the gas pressure of the gas film to the X-axis and to the Y-axis; 2. Using the Reynolds equation and heavy integrals, calculate the gas film bearing capacity and the moment of gas on the X-axis and Y-axis under the equal gap state; 3. Taking the gas film bearing capacity and eccentric load moment in the equal clearance state as the convergence condition as the non-equal clearance state, adjust the orifice outlet pressure to obtain a set of orifice outlet pressure values that meet the convergence conditions; 4. The original orifice inner diameter is selected as the initial value of the orifice inner diameter after leveling, and the XY plane is divided into multiple regions according to the number of orifices, and the gas flow conservation equation is used for nested coupling, that is, to satisfy The convergence condition is that the gas flow in and out of each area is equal and the total gas flow in and out of the entire gas film is equal. If the gas flow in and out of a certain area is not conserved during the calculation process, the inner diameter of the orifice is adjusted in small steps until the convergence condition is met. 2. The design method for equal gaps of integral air-floating guide rails under eccentric loads according to claim 1, characterized in that: in the second step, the thickness of the air film after the guide rails are adjusted to equal gaps is required to be the force before adjustment When the thickness of the center point of the slope is thicker, in the step three, when adjusting the initial value of the orifice outlet pressure, increase the orifice outlet pressure at the corresponding position where the gas film thickness becomes higher and decrease the corresponding position where the gas film thickness becomes higher. A low orifice outlet pressure value is used to obtain a set of orifice outlet pressure values that satisfy the torque convergence conditions and meet the thickness requirements. 3. The equal clearance design method of integral air-floating guide rail under eccentric load according to claim 2, characterized in that: in step 3, the outlet pressure of the orifice is adjusted so that it meets the torque convergence condition, when the obtained set of data When the torque convergence requirement is met but the bearing capacity convergence requirement is not satisfied, the bearing capacity can be changed by adding or subtracting the outlet pressure value of each orifice according to the smaller or larger bearing capacity, and then returning to readjust the torque convergence to This reciprocation can reach a set of pressure values at the outlet of the orifice, so that the torque and bearing capacity are all satisfied. 4. According to claim 2 or 3, the equal clearance design method of integral air bearing guide rail under eccentric load is characterized in that, when increasing or decreasing the outlet pressure value, unequal valves are selected for each orifice. The step size, that is, the step size of the outlet pressure of each orifice is given according to the proportional relationship between the change of the gas film thickness at each corresponding position. 5. The method for designing the equal clearance of the integral air-floating guide rail under partial load according to claim 1, characterized in that: in the second step, the thickness of the air film after the guide rail is adjusted to the equal clearance is not required to be in the partial load state When the thickness of the center point of the lower stressed inclined surface, that is, the initial value of the air film thickness can be higher or lower than the value of the center point thickness of the original inclined bearing surface, in step 3, adjust the outlet pressure values of all orifices at the same time, or only adjust part of the throttle. The position of the orifice corresponds to the gas film thickness and the outlet pressure of the orifice increases more to meet the convergence condition of the moment. 6. The equal-gap design method of integral air-floating guide rail under eccentric load according to claim 5, characterized in that: in step 3, when adjusting the outlet pressure values of all orifices at the same time, the specific method is to first adjust the throttling The outlet pressure of the hole makes it meet the torque convergence condition. When the obtained set of data does not meet the load-bearing capacity convergence requirement, adjust the gas film thickness in small steps to change the load-bearing capacity, and then return to readjust the torque convergence. In this way, a Set the outlet pressure value of the orifice to make the moment and bearing capacity meet the convergence.