Flow controller with outlet pressure feedback effect

Abstract

The invention discloses a flow controller with an outlet pressure feedback effect. A first capillary tube is arranged in the center of the top of a shell, the shell is provided with a cylindrical cavity with an opening in the lower end, a sliding valve and a circular truncated cone are installed in the cavity, a second capillary tube is arranged in the center of the sliding valve, and annular grooves are formed in the lower end of the sliding valve and the upper end of the circular truncated cone. An elastic element is installed in an inner cavity formed by the two annular grooves, an oil outlet through hole is formed in the center of the circular truncated cone, an annular oil inlet groove with an oil inlet hole is formed in the inner side wall of the lower section of the cylindrical cavity, and a throttling gap is formed between the lower end face of the sliding valve and the upper end face of the circular truncated cone and communicated with the annular oil inlet groove. According to the flow controller, under the condition that the outlet pressure is increased, the compression amount of the spring is changed through hydraulic pressure changes at the two ends of the sliding valve, the flow passing through a throttling gap is still obviously increased, and the oil film rigidity of a guide rail static pressure bearing is obviously improved. The radial size and length of the flow controller are small, and the flow controller can be directly installed in the structure of the oil cavity unit and has good practicability.

Description

Technical Field

[0001] The invention relates to the technical field of throttles, and in particular to a flow controller with outlet pressure feedback effect. Background Art

[0002] Liquid hydrostatic bearings, a type of sliding bearing, are sliding bearings that use a pressure pump to force pressurized lubricants into the tiny gap between the bearing and the shaft. Liquid hydrostatic bearings have a unique "error averaging effect" and their motion accuracy is much higher than that of rolling bearings and surface contact bearings. At the same time, since the bulk elastic modulus of the liquid medium is much greater than that of gas, its stiffness and load-bearing capacity are much higher than those of gas hydrostatic bearings. Therefore, liquid hydrostatic bearings have been widely used in ultra-precision machine tools that require large load-bearing capacity and high motion accuracy.

[0003] With the rapid development of aviation, aerospace and national defense construction, the precision requirements for high-end manufacturing equipment are getting higher and higher. Ultra-precision linear motion slides are key basic components for realizing the feed motion and feed accuracy of ultra-precision CNC machine tools, and are key components of ultra-precision CNC machine tools. Ultra-high rigidity and ultra-precision linear motion slides all use liquid hydrostatic support. The LODTM diamond lathe, which represents the world's highest level of precision processing, uses hydrostatic support for its guide rails and spindles. Therefore, how to further improve the rigidity and motion accuracy of liquid hydrostatic support has become the core issue for the future development of ultra-precision machine tools.

[0004] The most important performance indicators of hydrostatic guides are load-bearing capacity and oil film stiffness, whose characteristics directly affect the working performance of liquid hydrostatic guides. Since load changes during the working process are inevitable, in order to minimize the changes in oil film gap caused by load changes, it is particularly important to improve the oil film stiffness of the guide hydrostatic support.

[0005] The high-performance flow controller that is currently widely recognized is a pre-pressure pre-adjusted single-sided film feedback throttle developed by Hyprostatik in Germany, called a PM flow controller. The PM flow controller uses pressure difference to cause the deformation of the film inside the controller, and at the same time causes the gap between the film and the throttling cone and the throttling liquid resistance to change, thereby compensating and correcting the pressure and flow at the outlet of the PM controller. The PM controller is a spontaneous, active compensation element that can achieve excellent performance without an external pressure or flow monitor, and is wear-free, has no inertia lag, and has good dynamics.

[0006] However, PM flow controllers are much larger than traditional thin-walled small hole throttles and capillary throttles. Generally, PM flow controllers cannot be directly installed in the structure of the oil chamber unit. Using PM flow controllers in hydrostatic bearing applications will bring many inconveniences. Summary of the invention

[0007] The present invention aims to provide a flow controller with an outlet pressure feedback effect, in which the flow through the throttling gap is still significantly increased when the outlet pressure is increased, significantly improving the oil film stiffness of the guide rail hydrostatic support, and the controller is small in size and can be directly installed in the structure of the oil chamber unit.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] It comprises an outer shell, a first capillary is arranged at the top center of the outer shell, a cylindrical chamber with an opening at the lower end is arranged in the outer shell, a sliding valve and a frustum are installed in the cylindrical chamber, a second capillary is arranged at the center of the sliding valve, an upper annular groove is arranged at the lower end of the sliding valve, a lower annular groove is arranged at the upper end of the frustum, an elastic element is installed in the inner cavity formed by the upper annular groove and the lower annular groove, an oil outlet through hole is arranged at the center of the frustum, an annular oil inlet groove with an oil inlet hole is arranged on the inner side wall of the lower section of the cylindrical chamber, a throttling gap is arranged between the sliding valve and the frustum, and the throttling gap is communicated with the annular oil inlet groove.

[0010] Furthermore, the sliding valve is matched with the cylindrical chamber with a small clearance, and the frustum is matched with the cylindrical chamber with a small interference.

[0011] Furthermore, a groove is provided at the upper end of the sliding valve, and openings are symmetrically provided on both sides of the groove.

[0012] Furthermore, the elastic element is a spring or a disc spring.

[0013] Furthermore, a limiting ring groove is provided on the inner side wall of the cylindrical chamber, a limiting ring is installed in the limiting ring groove, and the limiting ring is tightly connected to the lower end of the truncated cone.

[0014] Furthermore, the flow controller can be directly installed in the body of the hydrostatic bearing or hydrostatic guide rail oil chamber unit.

[0015] The beneficial effects of the present invention are:

[0016] The flow controller of the present invention is small in size and can be directly installed in the structure of the oil chamber unit, and has good practicality. At the same time, the flow controller uses the effect of the outlet pressure to adjust the height of its throttling gap. When the outlet pressure increases, the height of the throttling gap increases accordingly, thereby significantly reducing the liquid resistance of the throttling gap. As a result, the flow through the throttling gap still increases significantly when the outlet pressure increases. The results of the preferred embodiment show that within the range of the oil chamber pressure being less than 70% of the oil supply pressure, the liquid hydrostatic support of the flow controller using the present invention has a higher oil film stiffness than that of the German PM flow controller, and is not affected by the viscosity of the hydraulic oil, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of the flow controller provided by the present invention;

[0018] Figure 2 A cross-sectional view of a flow controller provided by the present invention;

[0019] Figure 3 A schematic diagram of the structure and dimensions of the flow controller provided by the present invention;

[0020] Figure 4 A schematic diagram of pressure distribution on the upper and lower end surfaces of the slide valve of the flow controller provided by the present invention;

[0021] Figure 5 A schematic diagram of calculation and analysis of the hydraulic pressure exerted on the lower end surface of the slide valve of the flow controller provided by the present invention;

[0022] Figure 6 The flow-outlet pressure relationship curve diagram of the two flow controllers provided by the present invention;

[0023] Figure 7 An integrated structural diagram of a flow controller and a rectangular oil chamber support unit provided by the present invention;

[0024] Figure 8 Oil film stiffness curves of the oil chamber support units of the two flow controllers provided by the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0026] The figure marks in the drawings of the specification include: 1. shell; 2. cylindrical chamber; 3. sliding valve; 4. cone; 5. groove; 6. first capillary; 7. second capillary; 8. upper ring groove; 9. lower ring groove; 10. spring; 11. oil outlet hole; 12. annular oil inlet groove; 13. throttling gap; 14. opening; 15. limit ring.

[0027] like Figure 1 and Figure 2As shown, a flow controller with outlet pressure feedback effect comprises a housing 1, a first capillary 6 is provided at the top center of the housing 1, the housing 1 is provided with a cylindrical chamber 2 with an opening at the lower end, a slide valve 3 and a round table 4 are installed in the cylindrical chamber 2, the slide valve 3 and the cylindrical chamber 2 are matched with a small clearance, the round table 4 and the cylindrical chamber 2 are matched with a small interference, a groove 5 is provided at the upper end of the slide valve 3, the first capillary 6 is connected to the groove 5, and openings 14 are symmetrically provided on both sides of the groove 5 to ensure that the pressure oil reaches the slide valve 3 The entire upper end surface of the cylindrical chamber 2 is provided with a second capillary 7 in the center of the groove 5, an upper annular groove 8 is provided at the lower end of the slide valve 3, a lower annular groove 9 is provided at the upper end of the truncated cone 4, a spring 10 is installed in the inner cavity formed by the upper annular groove 8 and the lower annular groove 9, an oil outlet hole 11 is provided in the center of the truncated cone 4, the second capillary 7 is connected to the oil outlet hole 11, an annular oil inlet groove 12 with an oil inlet hole is provided on the inner side wall of the cylindrical chamber 2, a throttling gap 13 is provided between the slide valve 3 and the truncated cone 4, and the throttling gap 13 is connected to the annular oil inlet groove 12. A limiting ring groove is provided on the inner side wall of the cylindrical chamber 2, and a limiting ring 15 is installed at the limiting ring groove, and the limiting ring 15 is tightly connected to the lower end of the truncated cone 4.

[0028] Design principle:

[0029] Assume that the lower end surface of the flow controller's slide valve 3 is always parallel to the upper end surface of the truncated cone 4, and the oil inlet (inlet) pressure of the flow controller is p s In a certain state, the outlet pressure of the flow controller is p0, and the liquid pressure on the upper end surface of the slide valve 3 is p s1 The hydraulic pressure on the annular groove of the lower end surface of the slide valve 3 is p s2 , the viscosity of the hydraulic oil is μ, the diameter of the first capillary 6 is d1, the length is l1, the diameter of the second capillary 8 is d2, the length is l2, the radius of the oil outlet hole 11 is r1, the inner radius of the upper ring groove 8 and the lower ring groove 9 is r2, the outer radius of the upper ring groove 8 and the lower ring groove 9 is r3, the outer radius of the slide valve 3 is r4, and the relevant structural dimensions of the flow controller are as follows: Figure 3 Under this condition, the flow rate of the pressure oil entering the outlet of the flow controller after two capillary throttling is Q1, and the flow rate of the pressure oil entering the outlet of the control valve after two throttling gaps 13 is Q2, and the following equation can be obtained:

[0030]

[0031]

[0032] From the above formulas (1) and (2), we can respectively obtain:

[0033]

[0034]

[0035] Figure 4 The force distribution diagram of the hydraulic pressure on the upper and lower end surfaces of the flow controller slide valve 3 is shown in Figure 1. The hydraulic pressure on the upper end surface of the slide valve 3 is:

[0036] F1=πr4 2 p s1 (5)

[0037] like Figure 5 As shown, the hydraulic pressure on the lower end surface of the slide valve 3 can be divided into four parts for calculation. The oil outlet hole 11 (oil outlet) and the corresponding area of ​​the ring groove are respectively subjected to uniform pressure p0 and p s2 The pressures on the annular surfaces corresponding to the outer ring and the inner ring of the throttling gap 13 are:

[0038]

[0039]

[0040] The hydraulic pressure F2 on the lower end surface of the slide valve 3 is:

[0041] F2=F 21 +F 22 +F 23 +F 24 (8)

[0042] F 21 =πr1 2 p0 (8.1)

[0043]

[0044] F 23 =π(r3 2 -r2 2 ) s2 (8.3)

[0045]

[0046] Substituting equation (8.1) - equation (8.4) into equation (8) and rearranging it, we obtain:

[0047]

[0048] The resultant force of the hydraulic pressure on the slide valve 3 is (downward is positive):

[0049] F=F1-F2 (10)

[0050] Assume that the stiffness coefficient of the spring 10 is K (see Figure 2 ), then the downward displacement of the sliding valve 3 under the action of the hydraulic pressure is:

[0051] s=F / K=(F1-F2) / K (11)

[0052] Assuming that the oil inlet pressure of the flow controller is 0, the spring 10 is in a free extension state (that is, the spring 10 is not pre-compressed). At this time, the gap between the lower end surface of the slide valve 3 and the round table 4 is h0. When the oil inlet pressure of the flow controller is p s , When the outlet pressure is p0, the height of the throttling gap 13 is:

[0053] h c =h0-s=h0-(F1-F2) / K (12)

[0054] It can be seen from the combined formulas (1)-(5) and (8)-(11) that when the structural dimensions of the flow controller and the stiffness of the spring 10 are determined, the outlet flow of the control valve can be calculated given the inlet pressure and outlet pressure. The flow controller of the present invention can achieve that the combined force of the hydraulic pressure on both ends of the slide valve 3 is always downward by selecting appropriate capillary throttle parameters (d1 / l1, d2 / l2) and the radius parameters of the cone 4 (r1, r2, r3, r4). Moreover, as the outlet pressure of the control valve increases, the combined force of the hydraulic pressure on the slide valve 3 decreases accordingly. Under the action of the spring force, the height of the throttling gap 13 can be increased accordingly, thereby achieving an increase in the outlet flow. In practical applications, it is necessary to select and match the relevant structural parameters of the flow controller according to the constraints such as the oil supply pressure of the hydraulic system, the load of the static oil chamber, and the initial gap, so as to achieve the desired feedback effect. The flow controller adopts secondary capillary throttling and secondary throttling gap 13 throttling, and its purpose is to increase the number of throttling parameters (variables) so as to find a suitable parameter match and realize a more ideal outlet pressure-flow curve.

[0055] Example 1

[0056] For example Figure 3 After trial calculation and size parameter adjustment, the parameter values ​​of the flow controller shown in this calculation example are determined as shown in Table 1:

[0057] Table 1 Structural dimensions and oil supply parameters of flow controller

[0058]

[0059] To calculate the outlet flow rate of the flow controller under different outlet pressure conditions at a given oil supply pressure, different outlet pressure values ​​can be set first, and then p can be obtained by equations (3) and (4): s1 and p s2 , and then calculate h by equation (5), equation (9) and equation (12) c , h cSubstituting into equation (2) can determine Q2, and using equation (1) to determine Q1, we can obtain the total outlet flow rate of the controller: Q = Q1 + Q2. The calculation results of the outlet pressure-flow rate of this example are listed in Table 2.

[0060] Table 2 Flow rate of flow controller under different outlet pressure conditions

[0061]

[0062] The data in Table 2 is not convenient for judging the quality of the pressure-flow characteristics of the flow controller of the present invention, so the data of the PM flow controller are introduced for comparison. The outlet pressure-flow data of the PM flow controller can be generated according to the flow formula (13) given by Hyprostatik. The flow characteristic equation of the PM controller given by the company is:

[0063]

[0064] Where P p ——Pump pressure (MPa);

[0065] P——Oil chamber pressure under a certain load (MPa), its value is 0~0.9P p ;

[0066] Q0——initial flow (L / min), that is, the flow through the PM controller when the oil chamber pressure is 0;

[0067] Q——Flow rate through PM controller when oil chamber pressure is P (L / min);

[0068] K r ——Specific flow rate, which is the maximum theoretical flow rate Q p The ratio to the initial flow rate Q0 usually ranges from 2.5 to 3.0, with a maximum value of 3.5.

[0069] For comparison, the oil supply pressure of the PM flow controller is assumed to be the same as that in Table 1 (P p =2.5MPa), K r Take the maximum value of 3.5, and assume that the PM flow controller has an oil chamber pressure of P = 0.7P p = The flow rate at 1.75 MPa is equal to the flow rate at the corresponding pressure in Table 2, that is, Q 0.7 =1.63 (L / min), the flow rates at other pressures are calculated by formula (12), as shown in Table 3.

[0070] Table 3 Flow rate of PM flow controller under different oil chamber pressure conditions

[0071]

[0072]

[0073] The data in Table 2 and Table 3 are plotted into a pressure-flow curve, such as Figure 5 shown.

[0074] Depend on Figure 6 It can be seen that the outlet pressure-flow curve of the flow controller of the present invention changes nonlinearly, but when the outlet pressure changes in the range of 0.1-0.6 times the oil supply pressure, its pressure-flow curve is close to linear change, and the flow rate increase rate is greater than that of the PM controller. 5 The flow rate starts to drop after the oil supply pressure is doubled. In order to explore the static characteristics of this flow controller in the application of liquid hydrostatic support and its advantages and disadvantages compared with PM controller, the following takes the rectangular plane oil chamber support unit as an example and analyzes it by comparing its oil film stiffness.

[0075] Figure 7 This is a structural schematic diagram of a rectangular plane oil chamber support unit using the flow controller of the present invention. The outer diameter of the flow controller is 14 mm, so the controller can be directly installed in the oil chamber body. It is only necessary to install the oil inlet pipe joint at the oil inlet. Therefore, this flow controller has good practicality.

[0076] The structural dimensions of the rectangular plane oil chamber are shown in Table 4.

[0077] Table 4 Rectangular plane oil chamber structure dimensions

[0078]

[0079] right Figure 7 When calculating the static performance of the planar oil chamber support unit shown in the figure, the following assumptions can be made: ① The external load always points to the geometric center of the lower oil pad; ② Only the slider above the planar oil chamber is considered to move up and down, without tilting and lateral movement, so the gap heights of the four-way oil sealing edges of the oil chamber are equal; ③ The lubricating oil flows steadily and the flow state is laminar; ④ The area enclosed by the center line of the oil chamber sealing edge is taken as the effective bearing area of ​​the oil pad; ⑤ The friction force when the throttle slide valve moves is ignored.

[0080] The bearing capacity of the rectangular plane oil cavity is:

[0081] W=p0A e (14)

[0082] In the formula, A e =(Bb)(Ll), the effective bearing area of ​​the oil chamber unit.

[0083] When the oil chamber pressure is p0, the flow rate of the rectangular plane oil chamber is:

[0084]

[0085] Tables 2 and 3 show the oil supply flow rates of the flow controller and the PM flow controller of the present invention under different oil chamber pressures. The bearing capacity and oil film thickness of the oil chamber under the corresponding oil chamber pressures can be calculated by equations (14) and (15), respectively. The calculation results are listed in Tables 5 and 6.

[0086] Table 5 Load-bearing capacity and oil film thickness of the oil chamber unit of the flow controller of the present invention

[0087]

[0088] Table 6 Load capacity and oil film thickness of the oil chamber unit using PM flow controller

[0089]

[0090] Analysis of the oil film thickness data in Table 5 and Table 6 shows that when the oil chamber pressure is from 2.5kgf / cm 2 Increase to 20kgf / cm 2 During the process, the oil film thickness of the oil chamber support unit of the flow controller of the present invention is reduced by about 11μm, and the oil film thickness of the oil chamber support unit of the PM flow controller is reduced by about 14μm. In this variation range, the average oil film stiffness of the former is about 30% higher than that of the latter. When the oil chamber pressure changes from 7.5kgf / cm 2 Increased to 17.5kgf / cm 2 In the process, the oil film thickness of the oil chamber support unit of the flow controller using the present invention is reduced by 2.7μm, and the oil film thickness of the oil chamber support unit of the PM flow controller is reduced by 4μm. In this range, the average oil film stiffness of the former is more than 40% higher than that of the latter; in the range where the oil chamber pressure is 70%-90% greater than the oil supply pressure, the oil film stiffness of the latter is significantly greater than that of the former, but the hydrostatic bearing is generally in the condition where the oil chamber pressure is less than 75% of the oil supply pressure in actual production. The performance advantage of the PM flow controller in this range is not very meaningful in practical applications. Therefore, the flow controller of the present invention has great advantages when used under the condition where the oil chamber pressure is less than 75% of the oil supply pressure.

[0091] Figure 8 The oil film stiffness variation curves of the oil chamber support units of the two flow controllers at different oil chamber pressures. It can be seen that the maximum value of the oil film stiffness of the oil chamber support unit of the flow controller using the present invention appears near the oil chamber pressure of 50% of the oil supply pressure value, and the oil film stiffness of the oil chamber support unit using the PM flow controller increases with the increase of the oil chamber pressure. Therefore, the oil chamber pressure ranges of the best oil film stiffness of the oil chamber support units using these two flow controllers are very different, and can be reasonably designed and selected according to needs in practical applications.

[0092] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the technical solution of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection claimed by the present invention application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A flow controller with outlet pressure feedback effect, characterized in that: The invention comprises a shell (1), wherein a first capillary (6) is provided at the top center of the shell (1), a cylindrical chamber (2) with an opening at the lower end is provided in the shell (1), a sliding valve (3) and a truncated cone (4) are installed in the cylindrical chamber (2), a second capillary (7) is provided at the center of the sliding valve (3), an upper annular groove (8) is provided at the lower end of the sliding valve (3), a lower annular groove (9) is provided at the upper end of the truncated cone (4), an elastic element is installed in the inner cavity formed by the upper annular groove (8) and the lower annular groove (9), an oil outlet hole (11) is provided at the center of the truncated cone (4), an annular oil inlet groove (12) with an oil inlet hole is provided on the inner side wall of the lower section of the cylindrical chamber (2), a throttling gap (13) is provided between the sliding valve (3) and the truncated cone (4), and the throttling gap (13) is communicated with the annular oil inlet groove (12).

2. The flow controller according to claim 1, characterized in that: The slide valve (3) is fitted with the cylindrical chamber (2) with a small clearance, and the frustum (4) is fitted with the cylindrical chamber (2) with a small interference fit.

3. The flow controller according to claim 2, characterized in that: A groove (5) is provided at the upper end of the slide valve (3), and openings (14) are symmetrically provided on both sides of the groove (5).

4. The flow controller according to claim 3, characterized in that: The elastic element (10) is a spring or a disc spring.

5. The flow controller according to claim 4, characterized in that: The inner side wall of the cylindrical chamber (2) is provided with a limiting ring groove, a limiting ring (15) is installed in the limiting ring groove, and the limiting ring (15) is tightly connected to the lower end of the truncated table (4).

6. The flow controller according to any one of claims 1 to 5, characterized in that: The flow controller can be directly installed in the body of the hydrostatic bearing or hydrostatic guide rail oil chamber unit.

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