A Structure and Working Method for Improving the Shearing Force of a Servo Valve Spool

Abstract

The present invention discloses a structure and a working method for improving the shearing force of a servo valve spool. The spool is slidably arranged in the valve sleeve, and end plates are respectively arranged at both ends of the valve sleeve. The end plate, the valve sleeve and the left end face of the spool form a left control chamber, and the end plate, the valve sleeve and the right end face of the spool form a right control chamber. One end of the first spring contacts the end part, and the other end contacts the left end face of the spool. One end of the second spring contacts the end plate, and the other end contacts the right end face of the spool. Left and right annular grooves are arranged on the surface of the spool along the circumferential direction, and a first channel and a second channel are arranged on the surface of the spool along the axial direction. The first channel communicates with the right annular groove, and the second channel communicates with the left annular groove. An annular oil return window is arranged in the middle of the valve sleeve, and an oil through hole is arranged at the left end of the valve sleeve, so that the left control chamber communicates with the left control chamber of the pre-stage and the left control chamber of the spool of the amplification stage. An oil through hole is arranged at the right end of the valve sleeve, so that the right control chamber communicates with the right control chamber of the pre-stage and the right control chamber of the spool of the amplification stage.

Description

Technical Field

[0001] The present invention relates to the field of hydraulic components, and relates to a structure and working method for improving the shearing force of a servo valve spool. Background Art

[0002] The electro-hydraulic servo valve is a key component in electro-hydraulic servo control. It is a hydraulic control valve that, after receiving an analog electrical signal, correspondingly outputs a modulated flow rate and pressure. The electro-hydraulic servo valve has the advantages of fast dynamic response, high control accuracy, long service life, etc., and has been widely used in electro-hydraulic servo control systems in the fields of aviation, aerospace, ships, metallurgy, chemical engineering, etc.

[0003] The electro-hydraulic servo valve is sensitive to the oil pollution degree. There is data indicating that 80% of the failures of the electro-hydraulic servo valve are related to the oil pollution degree. In order to improve the anti-pollution ability of the electro-hydraulic servo valve, various techniques have been developed for improving the shearing force of the spool stage:

[0004] For example, increasing the pressure gain of the pre-stage of the electro-hydraulic servo valve, while being limited by the power of the torque motor and the ability of the hydraulic amplification stage.

[0005] For example, increasing the diameter of the spool stage, which brings a reduction in the dynamics of the servo valve and is also limited by the product volume. Summary of the Invention

[0006] Object of the Invention: The present invention provides a structure and working method for improving the shearing force of a servo valve spool, which is installed between the pre-stage and the amplification stage of the servo valve and can further improve the shearing driving force of the spool.

[0007] The technical solution of the present invention is as follows:

[0008] A structure for improving the shearing force of a servo valve spool includes a valve sleeve and a spool. The spool is slidably arranged in the valve sleeve. End plates are respectively arranged at both ends of the valve sleeve. The end plate, the valve sleeve and the left end face of the spool form a left control cavity, and the end plate, the valve sleeve and the right end face of the spool form a right control cavity. A first spring is arranged in the left control cavity. One end of the first spring contacts the end plate, and the other end contacts the left end face of the spool. A second spring is arranged in the right control cavity. One end of the second spring contacts the end plate, and the other end contacts the right end face of the spool. Left and right annular grooves are arranged on the surface of the spool along the circumferential direction. A first channel and a second channel are arranged on the surface of the spool along the axial direction. The first channel communicates with the right annular groove, and the second channel communicates with the left annular groove. An annular oil return window is arranged in the middle of the valve sleeve. An oil passage hole is arranged at the left end of the valve sleeve, so that the left control cavity communicates with the left control cavity of the pre-stage and the left control cavity of the spool of the amplification stage. An oil passage hole is arranged at the right end of the valve sleeve, so that the right control cavity communicates with the right control cavity of the pre-stage and the right control cavity of the spool of the amplification stage.

[0009] Further, the spool and the valve sleeve are in clearance fit.

[0010] Furthermore, the clearance between the spool and the valve sleeve is 2 μm to 5 μm.

[0011] Furthermore, the oil return window communicates with the oil return.

[0012] Furthermore, the valve sleeve is made of bearing stainless steel material.

[0013] Furthermore, the spool is made of bearing stainless steel material.

[0014] Furthermore, the structure for increasing the shearing force of the spool of the servo valve is installed between the pre-stage and the amplification stage of the servo valve.

[0015] The working method of the structure for increasing the shearing force of the spool of the servo valve:

[0016] When the input current of the torque motor of the electro-hydraulic servo valve is zero, the pressures in the left control chamber and the right control chamber of the pre-stage are equal. At this time, the spool is kept in the middle position under the action of the pressures in the left control chamber, the right control chamber, the first spring and the second spring. At this time, there is a covering distance Lz between the annular groove on the valve sleeve and the left annular groove on the spool, and there is a covering distance Ly between the annular groove on the valve sleeve and the right annular groove on the spool. The left control chamber, the right control chamber and the oil return window do not communicate.

[0017] When a positive current is given to the input of the torque motor of the electro-hydraulic servo valve, the baffle of the servo valve starts to deflect. Under the throttling effect, the pressure Pz in the left control chamber increases, and the pressure Py in the right control chamber decreases. At this time, the pressure difference △P between the left and right control chambers = Pz - Py. At this time, the spool moves to the right under the action of the pressure difference, compressing the second spring, and at the same time the covering distance Lz decreases and Ly increases. When the positive current continues to increase, when Lz decreases to 0, the right control chamber communicates with the oil return window, and there is a pressure drop △Pr. At this time, the pressure in the right control chamber further decreases on the basis of the original pressure, and the pressure in the right control chamber at this time is Py * , Py * = Py - △Pr; Therefore, the pressure difference between the left control chamber and the right control chamber increases by △Pr on the basis of the original pressure difference, that is, △P = Pz - Py * = Pz - Py + △Pr, then the driving force for the spool to move to the right increases, and the shearing force of the spool of the servo valve is increased;

[0018] When a negative current is input to the torque motor of the electro-hydraulic servo valve, the baffle of the servo valve starts to deflect. Under the throttling effect, the pressure Pz in the left control chamber decreases, and the pressure Py in the right control chamber increases. At this time, the pressure difference ΔP between the left and right control chambers is ΔP = Pz - Py. At this time, the spool moves to the left under the action of the pressure difference, compressing the first spring. At the same time, the covering distance Ly decreases and Lz increases. When the negative current continues to increase, when Ly decreases to 0, the left control chamber communicates with the oil return window, and a pressure drop ΔPr occurs. At this time, the pressure in the left control chamber further decreases on the basis of the original pressure, and the pressure in the left control chamber at this time is Pz * , Pz * = Pz - ΔPr; Therefore, the pressure difference between the right control chamber and the left control chamber increases by ΔPr on the basis of the original pressure difference, that is, ΔP = Pz * - Py = Pz - Py - ΔPr, then the driving force for the spool to move to the left increases, and the shearing force of the servo valve spool is increased.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] The present invention provides a structure and working method for improving the shearing force of a servo valve spool. It is installed between the pre-stage and the amplification stage of the servo valve, can improve the shearing force of the servo valve spool, is applicable to nozzle baffle and jet pre-stage two-stage electro-hydraulic servo valves, and can be applied to projects with high reliability and anti-pollution requirements in aviation and aerospace, having broad prospects and economic benefits. Brief Description of the Drawings

[0021] Figure 1 is a schematic diagram of the device for improving the shearing force of the servo valve spool of the present invention in the servo valve;

[0022] Figure 2a is a schematic diagram of the state when the spool is in the middle position;

[0023] Figure 2b is a schematic diagram of the state when the spool moves to the right;

[0024] Figure 2c is a schematic diagram of the state when the spool moves to the left;

[0025] Figure 3 is a schematic diagram of the pressure difference between the left and right control chambers before installing the structure of the present invention;

[0026] Figure 4 is a schematic diagram of the pressure change in the left and right control chambers after installing the structure of the present invention;

[0027] Figure 5 is a schematic diagram of the pressure difference between the left and right control chambers after installing the structure of the present invention;

[0028] Wherein: 1 valve sleeve, 2 valve core, 3 first spring, 4 second spring, 5 oil return window, 6 first channel, 7 second channel, 8 left control cavity, 9 right control cavity, 10 end plate. Detailed implementation mode

[0029] The following further describes the present invention in conjunction with the embodiments shown in the accompanying drawings.

[0030] A structure for improving the shearing force of the spool of a servo valve proposed by the present invention is applied in a two-stage electro-hydraulic servo valve, and the pre-stage can be a nozzle flapper or a jet structure. As Figure 1 shown, the device for improving the shearing force of the spool of the servo valve provided by the present invention is located between the pre-stage and the amplification stage. The left side of the device is connected to the left control cavity of the pre-stage and is also connected to the left end face cavity of the amplification stage to form an overall left control cavity; the right side of the device is connected to the right control cavity of the pre-stage and is also connected to the right end face cavity of the amplification stage to form an overall right control cavity.

[0031] As Figures 2a - 2c shown, the main body of the device for improving the shearing force of the spool of the servo valve is composed of a valve sleeve 1, a valve core 2 and two springs, namely a first spring 3 and a second spring 4. An end cover 10 can be used to fix the valve sleeve 1 and support the first spring 3 and the second spring 4. The valve core 2 and the valve sleeve 1 are in clearance fit. The first spring 3 and the second spring 4 are on both sides of the valve core 2 to provide restoring and balancing elastic forces. There are two annular grooves and two channels on the valve core 2, namely a first channel 6 and a second channel 7. The left annular groove communicates with the second channel 7, and the right annular groove communicates with the first channel 6. The valve sleeve 1 and both ends of the valve core 2 form a left control cavity 8 and a right control cavity 9, which are respectively communicated with the left and right control cavities of the pre-stage and the amplification stage through the oil holes on the valve sleeve 1. The left control cavity 8 can communicate with the right annular groove through the first channel 6, and correspondingly, the right control cavity 9 can communicate with the left annular groove through the second channel 7. There is an oil return window 5 in the middle of the valve sleeve 1 for communicating with the oil return. There is a covering distance Lz between the left annular groove on the valve core 2 and the oil return window 5. There is a covering distance Ly between the right annular groove and the oil return window 5.

[0032] The materials of the valve sleeve 1 and the valve core 2 are usually bearing stainless steel, and the fit clearance is generally about 2 μm to 5 μm. Bearing steel has the characteristics of high hardness, small deformation and wear resistance; the fit clearance of 2 μm to 5 μm has the characteristic of small leakage, and at the same time prevents excessive contamination from entering the clearance and causing jamming.

[0033] The working method of the structure for improving the shearing force of the spool of the servo valve of the present invention is as follows:

[0034] When the input current of the torque motor of the electro-hydraulic servo valve is zero, the pressures in the left control chamber and the right control chamber of the pre-stage are equal. At this time, the spool 2 is held in the middle position under the action of the pressures in the left control chamber 8, the right control chamber 9, the first spring 3, and the second spring 4. Due to the covering distances Lz and Ly, the left control chamber 8, the right control chamber 9, and the oil return port 5 are isolated, as Figure 2a shown.

[0035] When a positive current is given as the input to the torque motor of the electro-hydraulic servo valve, the servo valve baffle starts to deflect. Under the throttling effect, the pressure Pz in the left control chamber 8 increases, and the pressure Py in the right control chamber 9 decreases. At this time, the pressure difference ΔP between the left and right control chambers is ΔP = Pz - Py. At this time, the spool 2 moves to the right under the action of the pressure difference, compressing the second spring 4. At the same time, the covering distance Lz decreases and Ly increases. When the positive current continues to increase, as Figure 2b shown, when Lz decreases to 0, the right control chamber 9 communicates with the oil return port 5, and a pressure drop ΔPr occurs. At this time, the pressure in the right control chamber 9 further decreases on the original basis. At this time, Py * = Py - ΔPr. The original pressure difference between the left control chamber 8 and the right control chamber 9 increases by ΔPr, and ΔP = Pz - Py * = Pz - Py + ΔPr, as Figure 4 , Figure 5 shown.

[0036] As a comparison, when the device for improving the shearing force of the servo valve spool is not installed, the pressures and the pressure difference in the left and right control chambers of a common two-stage electro-hydraulic servo valve are as Figure 3 shown.

[0037] It can be seen that after the structure of the present invention is installed, the driving force for the spool 1 to move to the right increases, and the shearing force of the spool 1 is improved.

[0038] When a negative current is given as the input to the torque motor of the electro-hydraulic servo valve, the servo valve baffle starts to deflect. Under the throttling effect, the pressure Pz in the left control chamber 8 decreases, and the pressure Py in the right control chamber 9 increases. At this time, the pressure difference ΔP between the left and right control chambers is ΔP = Pz - Py. At this time, the spool 2 moves to the left under the action of the pressure difference, compressing the first spring 3. At the same time, the covering distance Ly decreases and Lz increases. When the negative current continues to increase, as Figure 2c shown, when Ly decreases to 0, the left control chamber 8 communicates with the oil return port 5, and a pressure drop ΔPr occurs. At this time, the pressure in the left control chamber 8 further decreases on the original basis. At this time, Pz * = Pz - ΔPr. The original pressure difference between the right control chamber 9 and the left control chamber 8 increases by ΔPr, and ΔP = Pz * - Py = Pz - Py - ΔPr, as Figure 4 , Figure 5 shown.

[0039] It can be seen that after the structure of the present invention is installed, the driving force for the valve core 1 to move to the right increases, and the shearing force of the valve core 1 is improved.

[0040] The above description of the embodiments is to enable those of ordinary skill in the art to understand and apply the present invention. Obviously, those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the embodiments herein, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A structure for improving the shearing force of a servo valve spool, characterized in that, It includes a valve sleeve and a valve core. The valve core is slidably arranged in the valve sleeve. End plates are respectively arranged at both ends of the valve sleeve. The end plate, the valve sleeve and the left end face of the valve core form a left control cavity, and the end plate, the valve sleeve and the right end face of the valve core form a right control cavity. A first spring is arranged in the left control cavity. One end of the first spring contacts the end plate, and the other end contacts the left end face of the valve core. A second spring is arranged in the right control cavity. One end of the second spring contacts the end plate, and the other end contacts the right end face of the valve core. Left and right annular grooves are arranged on the surface of the valve core along the circumferential direction. A first channel and a second channel are arranged on the surface of the valve core along the axial direction. The first channel communicates with the right annular groove, and the second channel communicates with the left annular groove. An annular oil return window is arranged in the middle of the valve sleeve. An oil through hole is arranged at the left end of the valve sleeve, so that the left control cavity communicates with the left control cavity of the pre-stage and the left control cavity of the spool of the amplification stage. An oil through hole is arranged at the right end of the valve sleeve, so that the right control cavity communicates with the right control cavity of the pre-stage and the right control cavity of the spool of the amplification stage.

2. The structure for improving the shearing force of the spool of a servo valve according to claim 1, characterized in that, The valve core and the valve sleeve are in clearance fit.

3. The structure for improving the shearing force of the spool of a servo valve according to claim 2, characterized in that, The clearance between the valve core and the valve sleeve is 2μm to 5μm.

4. The structure for improving the shearing force of the servo valve spool according to claim 1, characterized in that, The oil return window communicates with the oil return.

5. A structure for improving the shearing force of a servo valve spool according to claim 1, characterized in that, The valve sleeve is made of bearing stainless steel material.

6. A structure for improving the shearing force of a servo valve spool according to claim 1, characterized in that, The valve core is made of bearing stainless steel material.

7. A structure for improving the shearing force of a servo valve spool according to claim 1, wherein, The structure for improving the shearing force of the spool of the servo valve is installed between the pre-stage and the amplification stage of the servo valve.

8. The working method of the structure for improving the shearing force of the spool of the servo valve according to any one of claims 1-7, characterized in that: When the input current of the torque motor of the electro-hydraulic servo valve is zero, the pressures in the left and right control cavities of the pre-stage are equal. At this time, the valve core is kept in the middle position under the action of the pressures in the left and right control cavities and the first and second springs. At this time, there is a covering distance Lz between the annular groove on the valve sleeve and the left annular groove on the valve core, and there is a covering distance Ly between the annular groove on the valve sleeve and the right annular groove on the valve core. The left control cavity, the right control cavity and the oil return window do not communicate. When a positive current is input to the torque motor of the electro-hydraulic servo valve, the baffle of the servo valve starts to deflect. Under the throttling effect, the pressure Pz in the left control chamber increases, and the pressure Py in the right control chamber decreases. At this time, the pressure difference ΔP between the left and right control chambers is ΔP = Pz - Py. At this time, the spool moves to the right under the action of the pressure difference, compressing the second spring. At the same time, the covering distance Lz decreases and Ly increases. When the positive current continues to increase, when Lz decreases to 0, the right control chamber communicates with the oil return window, and there is a pressure drop ΔPr. At this time, the pressure in the right control chamber further decreases on the basis of the original pressure, and the pressure in the right control chamber at this time is Py * , Py * = Py - ΔPr; Therefore, the pressure difference between the left control chamber and the right control chamber increases by ΔPr on the basis of the original pressure difference, that is, ΔP = Pz - Py * = Pz - Py + ΔPr, then the driving force for the spool to move to the right increases, and the shearing force of the servo valve spool is increased; When a negative current is input to the torque motor of the electro-hydraulic servo valve, the servo valve baffle begins to deflect. Under the throttling effect, the pressure Pz in the left control chamber decreases, and the pressure Py in the right control chamber increases. At this time, the pressure difference ΔP between the left and right control chambers is ΔP = Pz - Py. At this time, the spool moves to the left under the action of the pressure difference, compressing the first spring. At the same time, the covering distance Ly decreases and Lz increases. When the negative current continues to increase, when Ly decreases to 0, the left control chamber communicates with the oil return window, and a pressure drop ΔPr occurs. At this time, the pressure in the left control chamber further decreases on the basis of the original pressure, and the pressure in the left control chamber at this time is Pz * , Pz * = Pz - ΔPr; Therefore, the pressure difference between the right control chamber and the left control chamber increases by ΔPr on the basis of the original pressure difference, that is, ΔP = Pz * - Py = Pz - Py - ΔPr, then the driving force for the spool to move to the left increases, and the shear force of the servo valve spool is increased.

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