A load flow closed-loop control servo valve and working method

Abstract

The present invention belongs to the field of mechanical hydraulics, and specifically relates to a load flow closed-loop control servo valve and a working method. The servo valve comprises a torque motor part, a hydraulic amplifier part, a flow feedback mechanism, and a power stage slide valve part; wherein the torque motor part comprises an upper magnetic conductor, a coil, a permanent magnet, an armature, a lower magnetic conductor, and a spring tube; the hydraulic amplifier part comprises a left nozzle, a baffle, a right nozzle, a left throttle hole component, an oil filter, and a right throttle hole component; the flow feedback mechanism comprises a left flow meter spring, a left cone valve core, a left check valve plate, a left check valve spring, a left feedback spring, a right feedback spring, a right check valve spring, a right check valve plate, a right throttle hole component, and a right cone valve core; the power stage slide valve part comprises a valve sleeve and a power valve core; the present invention solves the problems of jitter, creeping, low dynamics, low efficiency, etc. of the system caused by indirect control of the output flow, and reduces the processing accuracy of the power slide valve.

Description

Technical Field

[0001] The present invention belongs to the field of mechanical hydraulics, and in particular relates to a load flow closed-loop control servo valve and a working method thereof. Background Art

[0002] Currently, electro-hydraulic servovalves are widely used in a variety of important fields, including advanced civil aircraft, steel, and power generation. Primarily used in servomechanism control systems, they account for over one-third of all systems and strongly support the development of weaponry. The main servovalves currently available include the traditional nozzle-fender, jet-tube, deflector-jet, linear direct-drive, and rotary direct-drive types. Their common characteristic is that the output valve spool displacement is directly proportional to the input command signal, or has a relatively good linear relationship. The spool displacement, in turn, outputs a proportional no-load flow rate, ultimately demonstrating a no-load flow rate proportional to the input command signal. In applications where flow output precision is critical, flow control through servovalve spool control is difficult and susceptible to external torque disturbances. Controllers are typically used for closed-loop control. However, in harsh environments, such as those characterized by high temperature, high pressure, humidity, and high vibration, controllers are less adaptable. In these situations, a mechanical structure is required to implement a closed-loop load-flow control loop for precise load-flow control. Currently, no such products exist. Summary of the Invention

[0003] Purpose of the present invention:

[0004] In order to solve the shortcomings of the existing servo valve in achieving no-load flow control by controlling the valve core displacement, such as poor control flow accuracy and poor load interference resistance, the present invention proposes a flow feedback mechanism, a load flow feedback servo valve and a working method.

[0005] The technical solutions of the present invention are as follows:

[0006] On one hand, the present invention designs a load flow closed-loop control servo valve, which includes a torque motor part, a hydraulic amplification stage part, a flow feedback mechanism, and a power stage slide valve part;

[0007] The torque motor part includes an upper magnetic conductor, a coil, a permanent magnet, an armature, a lower magnetic conductor, and a spring tube; the hydraulic amplifier stage part includes a left nozzle, a baffle, a right nozzle, a left throttle orifice component, an oil filter, and a right throttle orifice component; the flow feedback mechanism includes a left flow meter spring, a left cone valve core, a left one-way valve plate, a left one-way valve spring, a left feedback spring, a right feedback spring, a right one-way valve spring, a right one-way valve plate, a right throttle orifice component, and a right cone valve core; the power stage slide valve part includes a valve sleeve and a power valve core;

[0008] In the flow feedback mechanism, the left cylindrical portion and the right cylindrical portion of the left cone valve core are respectively in corresponding holes of the housing; the left flowmeter spring and the left one-way valve spring are respectively sleeved on the left and right cylindrical portions of the left cone valve core; the left feedback spring is installed in the corresponding hole of the housing, with one end in contact with the left cone valve core and the other end in contact with the left end surface of the baffle; the conical surface of the left cone valve core is in contact with a corner of the housing; the left one-way valve plate is sleeved on the circular hole portion of the left cone valve core and in contact with one side of the left cone valve core;

[0009] The left and right cylindrical portions of the right cone valve core are respectively inserted into corresponding holes in the housing. The right flowmeter spring and right check valve spring are respectively sleeved onto the left and right cylindrical portions of the right cone valve core. The right feedback spring is installed in the corresponding hole in the housing, with one end contacting the right cone valve core and the other end contacting the right end face of the baffle. The conical surface of the right cone valve core mates with a corner of the housing. The right check valve plate is sleeved into the circular hole of the right cone valve core and mates with one side of the right cone valve core.

[0010] Furthermore, the hydraulic amplification stage, the left throttle hole component and the right throttle hole component are respectively sleeved on the left and right ends of the oil filter, and the three parts are collectively installed in the corresponding oil filter holes of the housing;

[0011] The left end of the left nozzle, the left end of the left throttle component and the left end of the power valve core are connected through the housing oil passage. The right end of the right nozzle, the right end of the right throttle component and the right end of the power valve core are connected through the housing oil passage.

[0012] The left end face of the left cone valve core is connected to the slide valve chamber B, and the right end is connected to the flow output port 2. The right end of the right cone valve core is connected to the slide valve chamber A, and the left end is connected to the flow output port A.

[0013] Furthermore, the power stage sliding valve part and the power valve core are installed in the valve sleeve and are jointly installed in the valve sleeve hole of the housing.

[0014] Furthermore, in the load flow closed-loop control servo valve as described above, the cylindricity of the left cylindrical surface of the left cone valve core is 0.001mm, the roughness is Ra0.1, the roundness of the working cone surface is 0.001mm, the aperture size of the oil hole is determined according to the flow rate of the servo valve, the flatness of the sealing surface is 0.002mm, and the perpendicularity with the left cylindrical surface is 0.002mm, the cylindricity of the right cylindrical surface is 0.001mm, the roughness is Ra0.1, and the coaxiality with the left cylindrical surface is 0.003mm.

[0015] Furthermore, the coil is sleeved outside the armature and is arranged between the upper and lower magnetic conductors, the permanent magnets are placed on the front and rear sides of the coil, and the baffle is interference-pressed in the center hole of the armature;

[0016] The left nozzle and the right nozzle are respectively installed in corresponding nozzle holes of the shell.

[0017] Furthermore, the left one-way valve plate has a left working surface with a flatness of 0.001 mm, an inner hole with a cylindricity of 0.001 mm and a roughness of Ra0.1, and a coaxiality with the left working surface of 0.003 mm;

[0018] Furthermore, the left feedback spring has the same stiffness as the right one-way valve spring, and the stiffness selection needs to be moderate. Too small will result in low valve dynamics, and too large will cause valve oscillation; the left and right end faces of the left feedback spring are perpendicular to the inner hole at 0.05mm.

[0019] Furthermore, the preload force of the left one-way valve spring is the left one-way valve plate multiplied by the acceleration value that the valve can withstand, with a 20% margin.

[0020] Furthermore, the perpendicularity between the left and right end faces of the left flow meter spring and the inner hole is 0.05 mm, and the stiffness design criterion is: when the servo valve flow is maximum, the valve plate displacement is guaranteed to be 0.4 mm.

[0021] Furthermore, the shell has a maximum fillet angle of R0.005mm and a roundness of 0.001mm with respect to the working conical surface, an inner hole in contact with the left cylindrical surface and the right cylindrical surface has a cylindricity of 0.001mm and a roughness of Ra0.1, and the coaxiality between the two holes is 0.003mm;

[0022] Furthermore, the stiffness of the baffle is 20 to 30 times that of the spring tube.

[0023] Another aspect of the present invention is the specific operating method of the load-flow closed-loop control servo valve designed as described above. When a positive current is input to the coil, the armature, acting under the electromagnetic force, moves counterclockwise around the center of rotation of the spring tube, causing the baffle to deflect to the right. This causes the power valve core to move leftward, and high-pressure oil enters the lower chamber of the bidirectional motor through the power valve core and the left check valve plate, causing the piston to move counterclockwise. At this time, the left flow feedback mechanism does not function to detect flow. The low-pressure oil in the upper chamber of the bidirectional motor pushes open the right cone valve core of the right flow meter and then returns to the oil tank through the power valve core. The left flow feedback mechanism now detects the output flow of the servo valve and converts the detected flow into a feedback force that acts on the baffle through the right feedback spring, creating a balance between the flow feedback torque and the torque generated by the input current. Therefore, the output load flow of the servo valve is proportional to the input signal current. Because the flow feedback mechanism feeds the load flow back to the servo valve baffle, the output load flow of the servo valve is essentially unaffected by interfering load pressure changes. Similarly, when a negative current is input to the coil, the movement direction of the internal components of the servo valve is opposite to that described above.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) The invention of a flow feedback mechanism with a small size and simple structure solves the problem of large feedback volume or slow dynamics of traditional flow meters;

[0026] 2) The invention of a load flow feedback servo valve solves the problem of poor flow control accuracy and poor load interference resistance caused by the traditional servo valve controlling the valve core displacement to achieve no-load flow and convert the load flow;

[0027] 3) A method for load flow feedback in a servo valve was invented. According to this method, the load flow can be fed back to the armature, spring tube, orifice, valve core and other positions to achieve closed-loop load flow feedback;

[0028] 4) The load flow servo valve of the present invention uses mechanical parts to realize a load flow closed loop, and outputs a load flow with high accuracy, avoiding the shortcomings of the traditional method of using a controller to control the flow and being unable to withstand high temperature, high pressure, humidity, strong vibration and other environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of a flow feedback mechanism and a load flow feedback servo valve according to an embodiment of the present invention;

[0030] Figure 2 This is a structural diagram of the left cone valve core according to an embodiment of the present invention;

[0031] Among them, the upper magnetic conductor 1, the coil 2, the permanent magnet 3, the armature 4, the lower magnetic conductor 5, the spring tube 6, the left nozzle 7, the baffle 8, the right nozzle 9, the left flowmeter spring 10, the left cone valve core 11, the left one-way valve plate 12, the left one-way valve spring 13, the left feedback spring 14, the left throttle orifice component 15, the oil filter 16, the valve sleeve 17, the power valve core 18, the right feedback spring 19, the right one-way valve spring 20, the right one-way valve plate 21, the right throttle orifice component 22, the right cone valve core 23, the right flowmeter spring 24, the housing 25, the left cylindrical surface 11A, the working cone surface 11B, the oil hole 11C, the sealing surface 11D, and the right cylindrical surface 11E. DETAILED DESCRIPTION

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings or specific implementation cases. It should be noted that some but not all of the disclosed examples are shown in the drawings. In fact, many different examples can be described and these examples should not be understood as being limited to the examples set forth herein. On the contrary, describing these examples makes the positive effects of the present invention more apparent, and any parts not detailed herein are considered to be well-known techniques or conventional technical means in the art.

[0033] See attached Figure 1The present invention specifically designs a load flow closed-loop control servo valve, whose functional structure includes a torque motor part, a hydraulic amplifier stage part, a flow feedback mechanism, and a power stage slide valve part. The torque motor part includes an upper magnetic conductor 1, a coil 2, a permanent magnet 3, an armature 4, a lower magnetic conductor 5, and a spring tube 6. The hydraulic amplifier stage part includes a left nozzle 7, a baffle 8, a right nozzle 9, a left throttle orifice component 15, an oil filter 16, and a right throttle orifice component 22. The flow feedback mechanism includes a left flowmeter spring 10, a left cone valve core 11, a left one-way valve plate 12, a left one-way valve spring 13, a left feedback spring 14, a right feedback spring 19, a right one-way valve spring 20, a right one-way valve plate 21, a right throttle orifice component 22, and a right cone valve core 23. The power stage slide valve part includes a valve sleeve 17 and a power valve core 18.

[0034] The coil 2 is sleeved on the armature 4 and is set between the upper magnetic conductor 1 and the lower magnetic conductor 5. The permanent magnet 3 is placed on the front and back sides of the coil 2. The baffle 7 is interference pressed in the center hole of the armature 4.

[0035] The left nozzle 7 and the right nozzle 9 are respectively installed in corresponding nozzle holes of the housing 25.

[0036] In the servo valve designed by the present invention, the flow feedback mechanism is the core design technology point, which can feed back the load flow to the armature, spring tube, throttle hole, valve core and other positions to achieve closed-loop feedback of the load flow;

[0037] In the attached Figure 1 In the figure (the inlet and outlet ports 1 and 2 of the torque motor section indicate the bidirectional movement of oil in the oil passage, which can enter and exit the oil passage), the specific structure is as follows: the left cylindrical portion and the right cylindrical portion of the left cone valve core 11 are respectively inserted into corresponding holes in the housing 25. The left flowmeter spring 10 and the left check valve spring 13 are respectively sleeved in the left and right cylindrical portions of the left cone valve core 11. The left feedback spring 14 is installed in the corresponding hole in the housing 25, with one end contacting the left cone valve core 11 and the other end contacting the left end surface of the baffle 8. The conical surface of the left cone valve core 11 is aligned with a corner of the housing 25. The left check valve plate 12 is sleeved in the circular hole portion of the left cone valve core 11 and is in contact with one side of the left cone valve core 11.

[0038] The left and right cylindrical portions of the right cone valve core 23 are respectively positioned within corresponding holes in the housing 25. The right flowmeter spring 24 and the right check valve spring 20 are respectively sleeved within the left and right cylindrical portions of the right cone valve core 23. The right feedback spring 19 is installed within the corresponding hole in the housing 25, with one end contacting the right cone valve core 23 and the other end contacting the right end surface of the baffle 8. The conical surface of the right cone valve core 23 is aligned with a corner of the housing 25. The right check valve plate 21 is sleeved within the circular hole of the right cone valve core 23 and is also aligned with one side of the right cone valve core 23.

[0039] The left throttle hole component 15 and the right throttle hole component 22 are respectively sleeved on the left and right ends of the oil filter 16 , and the three parts are collectively installed in the corresponding oil filter holes of the housing 25 .

[0040] The power valve core 18 is installed in the valve sleeve 17 and is installed together in the valve sleeve hole of the housing 25 .

[0041] The left end of the left nozzle 7, the left end of the left throttle component 15 and the left end of the power valve core 18 are connected through the oil passage of the housing 25. The right end of the right nozzle 9, the right end of the right throttle component 22 and the right end of the power valve core 18 are connected through the oil passage of the housing 25.

[0042] The left end surface of the left cone valve core 11 is connected to the slide valve chamber B, and the right end is connected to the flow output port 2. The right end of the right cone valve core 23 is connected to the slide valve chamber A, and the left end is connected to the flow output port A.

[0043] See attached Figure 2 In the servo valve designed by the present invention, the cone valve core is an important component, and the left and right cone valve cores are arranged symmetrically. Taking the left cone valve core design as an example, the left cylindrical surface 11A of the left cone valve core 11 has a cylindricity of 0.001mm and a roughness of Ra0.1. The roundness of the working cone surface 11B is 0.001mm. The aperture size of the oil hole 11C is determined according to the flow rate of the servo valve. The flatness of the sealing surface 11D is 0.002mm and the perpendicularity with the left cylindrical surface 11A is 0.002mm. The right cylindrical surface 11E has a cylindricity of 0.001mm, a roughness of Ra0.1, and a coaxiality of 0.003mm with the left cylindrical surface 11A.

[0044] In the one-way valve plate matched with the cone valve core designed as above, the left one-way valve plate 12 has a flatness of 0.001mm on the left working surface, a cylindricity of 0.001mm on the inner hole, a roughness of Ra0.1, and a coaxiality of 0.003mm with the left working surface;

[0045] In the cone valve core designed as above, the left feedback spring 14 has the same stiffness as the right one-way valve spring 20. The stiffness selection needs to be moderate. Too small will result in low valve dynamics, and too large will cause valve oscillation. The left and right end faces of the left feedback spring 14 are perpendicular to the inner hole at 0.05mm.

[0046] In the case of the cone valve core designed as above, the preload force of the left one-way valve spring 13 is the left one-way valve plate 12 multiplied by the acceleration value that the valve can withstand, with a 20% margin.

[0047] In the case of the cone valve core designed as above, the left and right end faces of the left flow meter spring 10 are perpendicular to the inner hole by 0.05 mm, and the stiffness design principle is: to ensure that the valve plate displacement is 0.4 mm when the servo valve flow is maximum.

[0048] In the case of the cone valve core designed as above, the housing 25 has an edge radius of R0.005mm (max) and a roundness of 0.001mm with respect to the working cone surface 11B. The inner hole contacting the left cylindrical surface 11A and the right cylindrical surface 11E has a cylindricity of 0.001mm and a roughness of Ra0.1. The coaxiality between the two holes is 0.003mm.

[0049] In the case of the cone valve core designed as above, the stiffness of the baffle 8 is 20 to 30 times that of the spring tube.

[0050] The load-flow closed-loop control servo valve specifically designed by the present invention operates as follows: when a positive current is input to coil 2, armature 4 is acted upon by electromagnetic force, causing it to move counterclockwise around the center of rotation of spring tube 6, driving baffle 8 to deflect rightward. This causes power valve core 18 to move leftward, and high-pressure oil enters the lower chamber of the bidirectional motor through power valve core 18 and left check valve plate 12, causing the piston to move counterclockwise. At this point, the left flow feedback mechanism no longer functions to detect flow. Low-pressure oil in the upper chamber of the bidirectional motor pushes open the right cone valve core 23 of the right flow meter and then returns to the oil tank through power valve core 18. The left flow feedback mechanism now detects the servo valve output flow and converts the detected flow into a feedback force that acts on the baffle via right feedback spring 19, creating a balance between the flow feedback torque and the torque generated by the input current. Therefore, the servo valve's output load flow is proportional to the input signal current. Because the flow feedback mechanism feeds the load flow back to the servo valve baffle, the servo valve's output load flow is essentially unaffected by interfering load pressure variations. Similarly, when a negative current is input to coil 2, the movement direction of the internal parts of the servo valve is opposite to that described above.

[0051] The above specific implementation methods or cases are only used to explain the technical solutions of the present invention and are not intended to limit the present application. Any parts not described in detail are regarded as conventional technical means or common knowledge in the field. It can be understood by ordinary technicians in this field that: based on the design concept of the present application, it should be possible to adaptively modify the technical solutions recorded in the aforementioned implementation methods, or replace some or all of the technical features therein with equivalents. These modifications, equivalent replacements, and adaptively improved technical solutions do not deviate from the technical essence of the present invention and should all be covered within the scope of protection of the present application.

Claims

1. A load flow closed-loop control servo valve, characterized in that: The servo valve comprises a torque motor part, a hydraulic amplifier stage part, a flow feedback mechanism, and a power stage slide valve part; The torque motor part includes an upper magnetic conductor (1), a coil (2), a permanent magnet (3), an armature (4), a lower magnetic conductor (5), and a spring tube (6); the hydraulic amplifier part includes a left nozzle (7), a baffle (8), a right nozzle (9), a left throttle component (15), an oil filter (16), and a right throttle component (22); the flow feedback mechanism includes a left flow meter spring (10), a left cone valve core (11), a left check valve plate (12), a left check valve spring (13), a left feedback spring (14), a right feedback spring (19), a right check valve spring (20), a right check valve plate (21), a right throttle component (22), and a right cone valve core (23); and the power stage slide valve part includes a valve sleeve (17) and a power valve core (18); In the flow feedback mechanism, the left cylindrical part and the right cylindrical part of the left cone valve core (11) are respectively in the corresponding holes of the housing (25); the left flow meter spring (10) and the left check valve spring (13) are respectively sleeved on the left and right cylindrical parts of the left cone valve core (11); the left feedback spring (14) is installed in the corresponding hole of the housing (25), one end of which contacts the left cone valve core (11) and the other end contacts the left end surface of the baffle (8); the cone surface of the left cone valve core (11) is in contact with a corner of the housing (25); the left check valve plate (12) is sleeved on the circular hole part of the left cone valve core (11) and is in contact with one side of the left cone valve core (11); The left cylindrical part and the right cylindrical part of the right cone valve core (23) are respectively in the corresponding holes of the housing (25); the right flow meter spring (24) and the right check valve spring (20) are respectively sleeved on the left and right cylindrical parts of the right cone valve core (23); the right feedback spring (19) is installed in the corresponding hole of the housing (25), one end of which contacts the right cone valve core (23) and the other end contacts the right end surface of the baffle (8); the cone surface of the right cone valve core (23) is fitted with a corner of the housing (25); the right check valve plate (21) is sleeved on the circular hole part of the right cone valve core (23) and is fitted with one side of the right cone valve core (23).

2. A load flow closed-loop control servo valve as claimed in claim 1, characterized in that: The hydraulic amplification stage part, the left throttle hole component (15) and the right throttle hole component (22) are respectively sleeved on the left and right ends of the oil filter (16), and the three parts are installed together in the corresponding oil filter hole of the housing (25); The left end of the left nozzle (7), the left end of the left throttle hole component (15) and the left end of the power valve core (18) are connected through the oil passage of the housing (25); the right end of the right nozzle (9), the right end of the right throttle hole component (22) and the right end of the power valve core (18) are connected through the oil passage of the housing (25); The left end surface of the left cone valve core (11) is connected to the slide valve cavity B, and the right end is connected to the flow output port 2. The right end of the right cone valve core (23) is connected to the slide valve cavity A, and the left end is connected to the flow output port A.

3. A load flow closed-loop control servo valve as claimed in claim 1, characterized in that: The power stage slide valve part and the power valve core (18) are installed in the valve sleeve (17) and are installed together in the valve sleeve hole of the housing (25).

4. A load flow closed-loop control servo valve as claimed in claim 1, characterized in that: In the flow feedback mechanism, The left cylindrical surface (11A) of the left cone valve core (11) has a cylindricity of 0.001 mm and a roughness of Ra0.1, the roundness of the working cone surface (11B) is 0.001 mm, the diameter of the oil hole (11C) is determined according to the flow rate of the servo valve, the flatness of the sealing surface (11D) is 0.002 mm, and the perpendicularity with the left cylindrical surface (11A) is 0.002 mm, the cylindricity of the right cylindrical surface (11E) is 0.001 mm, the roughness is Ra0.1, and the coaxiality with the left cylindrical surface (11A) is 0.003 mm.

5. A load flow closed-loop control servo valve as claimed in claim 4, characterized in that: The left one-way valve plate (12) has a left working surface with a flatness of 0.001 mm, an inner hole with a cylindricity of 0.001 mm and a roughness of Ra0.1, and a coaxiality with the left working surface of 0.003 mm.

6. A load flow closed-loop control servo valve as claimed in claim 5, characterized in that: The left feedback spring (14) and the right one-way valve spring (20) have the same stiffness. The stiffness should be moderate. If it is too small, the valve dynamics will be low, and if it is too large, it will cause valve oscillation. The left and right end faces of the left feedback spring (14) have a perpendicularity of 0.05mm to the inner hole.

7. A load flow closed-loop control servo valve as claimed in claim 6, characterized in that: The preload force of the left one-way valve spring (13) is the left one-way valve plate (12) multiplied by the acceleration value that the valve can withstand, with a 20% margin.

8. A load flow closed-loop control servo valve as claimed in claim 7, characterized in that: The left and right end faces of the left flow meter spring (10) are perpendicular to the inner hole by 0.05 mm, and the rigidity design criterion is: when the flow rate of the servo valve is maximum, the valve plate displacement is guaranteed to be 0.4 mm.

9. A load flow closed-loop control servo valve as claimed in claim 8, characterized in that: The shell (25) has a maximum value of R0.005mm and a roundness of 0.001mm at the edge fillet of the working conical surface (11B). The inner hole contacting the left cylindrical surface (11A) and the right cylindrical surface (11E) has a cylindricality of 0.001mm and a roughness of Ra0.

1. The coaxiality between the two holes is 0.003mm.

10. The operating method of the load flow closed-loop control servo valve according to any one of claims 1 to 9, characterized in that: The working method of the servo valve is as follows: when the coil (2) inputs a positive current, the armature (4) is acted upon by the electromagnetic force and moves counterclockwise around the rotation center of the spring tube (6), driving the baffle plate (8) to deflect to the right, and then the power valve core (18) moves to the left, and the high-pressure oil enters the lower chamber of the bidirectional motor through the power valve core (18) and the left one-way valve plate (12), causing the piston to move counterclockwise. At this time, the left flow feedback mechanism does not play a role in detecting the flow, and the low-pressure oil in the upper chamber of the bidirectional motor pushes open the right cone valve core (23) of the right flow meter, and then returns to the oil tank through the power valve core (18); at this time, the left flow feedback mechanism plays a role in detecting the output flow of the servo valve, and converts the detected flow into feedback force to act on the baffle plate through the right feedback spring (19), forming a balance between the flow feedback torque and the torque generated by the input current; When a negative current is input to the coil (2), the movement direction of the internal parts of the servo valve is opposite to the above movement direction.

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