Pilot-operated proportional cartridge valve based on servo motor drive

Abstract

The present invention discloses a pilot-operated proportional cartridge valve driven by a servo motor, comprising: a servo motor, a cover plate, a pilot spool, a main spool and a valve sleeve. The servo motor drives the pilot spool to rotate, and a hydraulic half-bridge formed by a fixed damping orifice and a variable damping orifice converts the rotation angle of the pilot spool into the pressure of a control oil chamber to drive the main spool to move. A follow-up control is achieved between the main spool and the pilot spool through the negative feedback of the hydraulic half-bridge. The servo motor driving the pilot spool only needs to overcome relatively small inertial forces, frictional forces and hydraulic unbalance forces, which is beneficial to selecting a servo motor with a relatively small power. The rotation angle of the pilot spool for the full stroke is relatively small, which is beneficial to shortening the step response time of the pilot spool. The driving force of the main spool is not restricted by the power of the servo motor, and the stroke of the main spool is not restricted by the stroke of the pilot spool, which is beneficial to increasing the maximum working pressure and the maximum working flow rate of the main valve.

Description

Technical Field

[0001] The present invention relates to a pilot-operated proportional cartridge valve driven by a servo motor. Background Art

[0002] Traditional proportional cartridge valves use electro-hydraulic servo valves as the pilot stage. Electro-hydraulic servo valves have complex manufacturing processes, high costs, and high requirements for oil cleanliness, resulting in high usage costs and difficult maintenance, which hinder their wider application. In addition, for proportional cartridge valves that directly drive the main spool using a servo motor and a ball screw, although the structure is simplified compared to traditional proportional cartridge valves, since the motor power is inversely proportional to the response speed, it is impossible to balance the driving force and response speed required by the main spool in applications with high pressure and large flow rates. Summary of the Invention

[0003] To solve the deficiencies of the prior art, the present invention provides a pilot-operated proportional cartridge valve driven by a servo motor that can solve the above problems.

[0004] To achieve the above objectives, the present invention adopts the following technical solutions:

[0005] A pilot-operated proportional cartridge valve driven by a servo motor, the structure of which includes: a servo motor, a cover plate, a pilot spool, a main spool, and a valve sleeve. The outer shell of the servo motor is fixedly connected to the cover plate; the cover plate is fixedly connected to the valve sleeve; the output shaft of the servo motor is fixedly connected to the pilot spool, and the pilot spool rotates around its axis; the pilot spool is installed in the inner hole of the main spool, and the outer circle of the pilot spool is in clearance fit with the inner hole of the main spool; the main spool is installed in the inner hole of the valve sleeve, and the outer circle of the main spool is in clearance fit with the inner hole of the valve sleeve; a variable damping hole is formed between the pilot spool and the main spool, and the flow area of the variable damping hole changes with the rotation angle of the pilot spool and the axial displacement of the main spool; a control oil chamber is formed at the top of the main spool; the control oil chamber is communicated with the second main valve port through the variable damping hole; the control oil chamber is communicated with the first main valve port through an oil inlet passage including a fixed damping hole.

[0006] Optionally, a guiding device is provided between the main spool and the valve sleeve, which prevents the main spool from rotating around its axis and allows the main spool to move linearly along its axis.

[0007] Optionally, the pilot spool can only rotate around its axis.

[0008] Optionally, the control oil chamber is surrounded by the cover plate, the pilot spool, the main spool, and the valve sleeve.

[0009] Optionally, the oil inlet passage between the control oil chamber and the first main valve port is located inside the main spool.

[0010] Optionally, a pilot oil passage is provided inside the cover plate. The pilot oil passage is communicated with the first main valve port through an external oil passage. The pilot oil passage and the external oil passage together constitute an oil inlet passage between the control oil chamber and the first main valve port.

[0011] The beneficial effects of the present invention are as follows:

[0012] The provided servo-motor-driven pilot-operated proportional cartridge valve drives the rotation of the pilot valve core by a servo motor. The variable damping orifice formed between the pilot valve core and the main valve core and the fixed damping orifice on the pilot oil inlet passage together form a hydraulic half-bridge. The high-pressure oil output by the hydraulic half-bridge drives the movement of the main valve core. At the same time, follow-up control is achieved between the main valve core and the pilot valve core through hydraulic negative feedback. The servo motor driving the pilot valve core only needs to overcome the influence of smaller inertial force, friction force and hydraulic unbalance force, which is beneficial to selecting a servo motor with a smaller power, thereby improving the response speed of the servo motor. The full-stroke rotation angle of the pilot valve core is smaller, which is beneficial to shortening the step response time of the pilot valve core. The above two characteristics are beneficial to improving the response speed of the main valve core; the hydraulic half-bridge converts the rotation angle of the pilot valve core into the pressure of the control oil chamber, which can provide sufficient driving force for the main valve core, and the driving force of the main valve core is not restricted by the power of the servo motor. The stroke of the main valve core is only related to the lead of the pilot valve core and is not restricted by the stroke of the pilot valve core. The above two characteristics are beneficial to improving the maximum working pressure and maximum working flow rate of the main valve port. Description of the Drawings

[0013] FIG. 1(a) and FIG. 1(b) are schematic cross-sectional structural views of the servo-motor-driven pilot-operated proportional cartridge valve according to two embodiments of the present invention installed on a valve block;

[0014] Figure 2 is a schematic cross-sectional structural view of the servo-motor-driven pilot-operated proportional cartridge valve according to an embodiment of the present invention;

[0015] Figure 3 is an external view of the servo-motor-driven pilot-operated proportional cartridge valve according to an embodiment of the present invention;

[0016] Figure 4 is a schematic view of different working positions of the pilot valve core relative to the main valve core according to an embodiment of the present invention.

[0017] Cover plate 1, cover plate sealing ring 2, return spring 3, mounting hole 4, first stepped hole 5, second stepped hole 6, third stepped hole 7, bearing outer ring locking nut 8, motor base 9, coupling 10, servo motor 11, pilot valve core 12, bearing inner ring locking nut 13, angular contact ball bearing 14, Gleitring pressing plate 15, rotating shaft Gleitring 16, first channel 17, fixed damping hole 18, process hole 19, process plug 20, second channel 21, pilot oil circuit 22, pilot oil circuit sealing ring 23, control oil chamber 24, guide screw 25, guide bearing 26, fifth channel 27, guide groove 28, third channel 29, first main valve port 30, second O-ring 31, fourth channel 32, second main valve port 33, mounting counterbore 34, main valve core 35, valve sleeve 36, first O-ring 37, valve block 38, variable damping hole 39, valve sleeve fixing screw 40. Detailed implementation mode

[0018] The present invention will be specifically introduced below in conjunction with the accompanying drawings and specific embodiments.

[0019] As shown in Fig. 1(a), a pilot-operated proportional cartridge valve driven by a servo motor 11 includes: a servo motor 11, a cover plate 1, a pilot valve core 12, a main valve core 35, and a valve sleeve 36. The servo motor 11 is fixedly installed on the cover plate 1 through a motor base 9. The cover plate 1 is formed with a mounting hole 4. One end of the pilot valve core 12 passes through the mounting hole 4 and is fixedly connected to the output shaft of the servo motor 11. The other end of the pilot valve core 12 is slidably disposed in the inner hole of the main valve core 35 in a clearance fit manner. A variable damping hole 39 with a variable flow area is formed between the pilot valve core 12 and the main valve core 35. The main valve core 35 is slidably disposed in the inner hole of the valve sleeve 36 in a clearance fit manner. The valve sleeve 36 is formed with a first main valve port 30 and a second main valve port 33 for connecting an application system. A control oil chamber 24 is jointly formed among the cover plate 1, the pilot valve core 12, the main valve core 35, and the valve sleeve 36. The control oil chamber 24 communicates with the second main valve port 33 through the variable damping hole 39.

[0020] As a preferred embodiment, as shown in Fig. 1(a), fixing damping holes 18 are formed on the cover plate 1, a first passage 17 for connecting the control oil chamber 24 and the fixing damping holes 18, and a second passage 21 for connecting the fixing damping holes 18 and the pilot oil passage 22. In specific applications, the valve sleeve 36 is installed in the mounting counterbore 34 of the valve block 38. The valve block 38 is formed with a third passage 29 for connecting the system and the first main valve port 30, a fourth passage 32 for connecting the system and the second main valve port 33, and a fifth passage 27 for connecting the third passage 29 and the pilot oil passage 22. After the high-pressure oil flows into from the third passage 29, it is divided into two branches. The first branch flows through the first main valve port 30 and the second main valve port 33 to the fourth passage 32, and the second branch passes through the fifth passage 27 in the valve block 38, the pilot oil passage 22, the second passage 21 in the cover plate 1, the fixing damping holes 18, the first passage 17 in the cover plate 1, the control oil chamber 24, the variable damping hole 39, and the second main valve port 33 and finally flows to the fourth passage 32 in the valve block 38.

[0021] As another preferred embodiment, as shown in Fig. 1(b), fixing damping holes 18' are formed on the main spool 35, a first passage 17' for connecting the control oil chamber 24 and the fixing damping holes 18', and a second passage 21' for connecting the fixing damping holes 18' and the first main valve port 30. In specific applications, the valve sleeve 36 is installed in the mounting counterbore 34 of the valve block 38. The valve block 38 is formed with a third passage 29 for connecting the system and the first main valve port 30 and a fourth passage 32 for connecting the system and the second main valve port 33. After the high-pressure oil flows into the first main valve port 30 from the third passage 29 in the valve block 38, it is divided into two branches. The first branch flows through the first main valve port 30 and the second main valve port 33 to the fourth passage 32 in the valve block 38, and the second branch passes through the second passage 21' in the main spool 35, the fixing damping holes 18', the first passage 17' in the main spool 35, the control oil chamber 24, the variable damping hole 39, and the second main valve port 33 and finally flows to the fourth passage 32 in the valve block 38.

[0022] As a preferred embodiment, the fixing damping holes can be installed on the oil passage by a plug with a through hole of a fixed diameter or directly machined on the oil passage.

[0023] As a preferred embodiment, a guiding groove 28 is formed on the outer wall of the main spool 35 along the axial direction of the main spool 35. The valve sleeve 36 is provided with a guiding screw 25 for cooperating with the guiding groove 28 to guide the movement of the main spool 35.

[0024] As a preferred embodiment, a guiding bearing 26 is sleeved on one end of the guiding screw 25 that cooperates with the guiding groove 28.

[0025] As a preferred embodiment, an external thread is formed at the upper end of the pilot spool 12 for installing a bearing inner ring locking nut 13 that axially presses the pilot spool 12 and the bearing inner ring together.

[0026] As a preferred embodiment, the valve sleeve 36 is formed with a plurality of first main valve ports 30. The first main valve ports 30 are evenly distributed in the circumferential direction of the valve sleeve 36.

[0027] As a preferred embodiment, a return spring 3 is installed at the upper end of the main spool 35. The return spring 3 exerts a downward pre-tightening force on the main spool 35 to ensure that the main spool 35 is in the lowermost position when the pilot oil pressure provided by the first main valve port 30 is insufficient.

[0028] As a preferred embodiment, the cover plate 1 is formed with a first stepped hole 5, a second stepped hole 6, and a third stepped hole 7. An axial rotating Gland ring 16 is provided in the first stepped hole 5. A Gland plate 15 and an angular contact ball bearing 14 are provided in the second stepped hole 6. A bearing outer ring locking nut 8 is provided in the third stepped hole 7. The axial rotating Gland ring 16, the Gland plate 15, the angular contact ball bearing 14, and the bearing outer ring locking nut 8 are arranged in sequence from bottom to top in the vertical direction. The bearing outer ring locking nut 8 presses the bearing outer ring and the Gland plate 15 together against the cover plate 1. The bearing inner ring locking nut 13 presses the pilot spool 12 and the inner ring of the angular contact ball bearing 14 together. In this way, the pilot spool 12 can only rotate around its axis and cannot translate along its axis direction. The angular contact ball bearing 14 can reduce the frictional resistance when the pilot valve rotates and enable the pilot spool 12 to bear a certain axial unbalanced force. The axial rotating Gland ring 16 prevents the high-pressure oil in the control oil chamber 24 from overflowing through the gap between the pilot spool 12 and the cover plate 1.

[0029] In this solution, a cover plate seal ring 2 and a pilot oil circuit seal ring 23 are provided between the cover plate 1 and the valve block 22. The cover plate seal ring 2 and the pilot oil circuit seal ring 23 are respectively used to prevent the high-pressure oil in the control oil chamber 24 and the pilot oil circuit 22 from overflowing through the gap between the cover plate 1 and the valve block 22. Specifically, the cover plate seal ring 2 is sleeved on the outer periphery of the valve sleeve 36, and the pilot oil circuit seal ring 23 is arranged in a seal groove on the cover plate 1 that is coaxial with the pilot oil circuit 22. A first O-ring 37 and a second O-ring 31 are provided between the valve block 22 and the valve sleeve 36. The first O-ring 37 and the second O-ring 31 are respectively used to prevent the high-pressure oil of the first main valve port 30 and the second main valve port 33 from overflowing through the gap between the valve block 22 and the valve sleeve 36. Specifically, the first O-ring 37 and the second O-ring 31 are respectively arranged at both ends of the valve sleeve 36.

[0030] Based on the above structure, the main spool 35 can only move linearly along the axial direction under the cooperation of the guiding screw 25 and the guiding groove 28, and cannot rotate. Further, a guiding bearing 26 provided at one end of the guiding screw 25 forms a rolling fit with the guiding groove 28, thereby reducing the wear and frictional force on the contact surfaces of the two.

[0031] From Figure 4 It can be seen the variation relationship of the flow area of the variable throttle orifice with the rotation angle of the pilot spool 12 and the displacement of the main spool 35. The lower end of the pilot spool 12 is inserted into the inner hole at the upper end of the main spool 35 in a clearance fit manner. A spiral notch is formed along the circumference at the lower end of the pilot spool 12, and a rectangular notch is opened at the upper end of the main spool 35. The relative position of the overlapping part between the spiral notch at the lower end of the pilot valve and the rectangular throttle notch at the upper end of the main spool 35 determines the size of the flow area of the variable throttle orifice. The movement of the main spool 35 along the axial direction or the rotation of the pilot spool 12 around the axis will change the flow area of the variable throttle orifice.

[0032] The main function of the present invention is to drive the pilot spool 12 to rotate by the servo motor 11, changing the flow area of the variable damping orifice 39. Furthermore, high-pressure oil is output through the hydraulic half-bridge composed of the fixed damping orifice 18 and the variable damping orifice 39 to drive the main spool 35 to move relative to the valve sleeve 36, and finally change the flow area of the main valve variable throttle port.

[0033] The action sequence for controlling the main spool 35 to move away from the second main valve port 33 along its axis is as follows:

[0034] The servo motor 11 drives the pilot spool 12 to rotate clockwise. The flow area of the variable damping orifice 39 increases, the pressure in the control oil chamber 24 decreases, and the main spool 35 moves in the direction away from the second main valve port 33 under the action of the axial hydraulic unbalanced force. At this time, the flow area of the main valve port of the cartridge valve gradually increases. As the main spool 35 moves, the flow area of the variable damping orifice 39 gradually decreases, the pressure in the control oil chamber 24 increases, until the axial force on the main spool 35 reaches a new balance state again, and the flow area of the main valve port of the cartridge valve remains stable.

[0035] The action sequence for controlling the main spool 35 to move towards the second main valve port 33 along its axis is as follows:

[0036] The servo motor 11 drives the pilot spool 12 to rotate counterclockwise. The flow area of the variable damping orifice 39 decreases, the pressure in the control oil chamber 24 increases, and the main spool 35 moves in the direction towards the second main valve port 33 under the action of the axial hydraulic unbalanced force. At this time, the flow area of the main valve port of the cartridge valve gradually decreases. As the main spool 35 moves, the flow area of the variable damping orifice 39 gradually increases, the pressure in the control oil chamber 24 decreases, until the axial force on the main spool 35 reaches a new balance state again, and the flow area of the valve port of the cartridge valve remains stable.

[0037] In summary, by driving the pilot valve core 12 to rotate a certain angle by the servo motor 11, the main valve core 35 can be proportionally controlled to move a certain distance along the axial direction, so as to realize the proportional control of the opening degree of the main valve port by the rotation angle of the servo motor 11.

[0038] The cartridge valve mentioned above is the pilot-operated proportional cartridge valve provided by the present invention based on the drive of the servo motor 11.

[0039] The pilot-operated proportional cartridge valve provided by the present invention drives the pilot valve core 12 to rotate through the servo motor 11. The variable damping hole 39 formed between the pilot valve core 12 and the main valve core 35 and the fixed damping hole 18 on the pilot oil inlet channel together form a hydraulic half-bridge. The high-pressure oil output by the hydraulic half-bridge drives the main valve core 35 to move. At the same time, the main valve core 35 and the pilot valve core 12 achieve follow-up control through hydraulic negative feedback. The servo motor 11 only needs to overcome the influence of smaller inertia force, friction force and hydraulic unbalance force to drive the pilot valve core 12, which is beneficial to selecting a servo motor 11 with a smaller power, thereby improving the response speed of the servo motor 11. The full stroke rotation angle of the pilot valve core 12 is smaller, which is beneficial to shortening the step response time of the pilot valve core 12. The above two characteristics are beneficial to improving the response speed of the main valve core 35; the hydraulic half-bridge converts the rotation angle of the pilot valve core 12 into the pressure of the control oil chamber 24, which can provide sufficient driving force for the main valve core 35, and the driving force of the main valve core 35 is not restricted by the power of the servo motor 11. The stroke of the main valve core 35 is only related to the lead of the pilot valve core 12 and is not restricted by the stroke of the pilot valve core 12. The above two characteristics are beneficial to improving the maximum working pressure and maximum working flow of the main valve port.

[0040] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form. Any technical solutions obtained by using equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A pilot-operated proportional cartridge valve driven by a servo motor, the structure of which includes: A servo motor, a cover plate, a pilot spool, a main spool and a valve sleeve, characterized in that: the outer shell of the servo motor is fixedly connected to the cover plate; the cover plate is fixedly connected to the valve sleeve; the output shaft of the servo motor is fixedly connected to the pilot spool, and the pilot spool can rotate around its axis; the pilot spool is installed in the inner hole of the main spool, and the outer circle of the pilot spool is in clearance fit with the inner hole of the main spool; the main spool is installed in the inner hole of the valve sleeve, and the outer circle of the main spool is in clearance fit with the inner hole of the valve sleeve; a variable damping hole is formed between the pilot spool and the main spool, and the flow area of the variable damping hole changes with the rotation angle of the pilot spool and the axial displacement of the main spool; a control oil chamber is formed at the top of the main spool; the control oil chamber is communicated with the second main valve port through the variable damping hole; the control oil chamber is communicated with the first main valve port through an oil inlet passage including a fixed damping hole; The control oil chamber is surrounded by the cover plate, the pilot spool, the main spool and the valve sleeve; The cover plate has a pilot oil passage, and the pilot oil passage is communicated with the first main valve port through an external oil passage. The pilot oil passage and the external oil passage together form an oil inlet passage between the control oil chamber and the first main valve port; The cover plate is formed with the fixed damping hole, a first passage for connecting the control oil chamber and the fixed damping hole, and a second passage for connecting the fixed damping hole and the pilot oil passage; the valve sleeve is installed in the installation counterbore of the valve block; the valve block is formed with a third passage for connecting the external oil passage and the first main valve port, a fourth passage for connecting the oil using system and the second main valve port, and a fifth passage for connecting the third passage and the pilot oil passage; The lower end of the pilot spool is inserted into the inner hole of the upper end of the main spool in a clearance fit manner. The lower end of the pilot spool is formed with a spiral notch along the circumference, and a rectangular notch is opened at the upper end of the main spool.

2. The pilot-operated proportional cartridge valve driven by a servo motor according to claim 1, characterized in that: A guiding device is provided between the main spool and the valve sleeve. The guiding device prevents the main spool from rotating around its axis and allows the main spool to move linearly along its axis.

3. The pilot-operated proportional cartridge valve driven by a servo motor according to claim 1, characterized in that: The pilot spool can only rotate around its axis.

Images