CN114517802A

CN114517802A - Electro-hydraulic servo valve with stroke braking controlled by servo motor

Info

Publication number: CN114517802A
Application number: CN202210023435.2A
Authority: CN
Inventors: 范文豹
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-01-10
Filing date: 2022-01-10
Publication date: 2022-05-20

Abstract

The invention belongs to the technical field of hydraulic reversing valves, and particularly relates to an electro-hydraulic servo valve with stroke braking controlled by a servo motor. The device comprises a servo motor, a PT valve, an AB valve, a valve body and a feedback device; the servo motor is arranged at one end of the valve body and is connected with the outer side end of the PT valve arranged in the inner cavity of the valve body through a coupler; the AB valve is arranged in the inner cavity of the valve body and is opposite to the end face of the PT valve; bearings for limiting are respectively arranged between the AB valve and the PT valve and the valve body; the PT valve and the AB valve are end face rotary valves; and the outer side end of the AB valve is connected with a feedback device arranged at the other end of the valve body. The hydraulic servo valve solves the problem of quickly and accurately controlling the hydraulic oil cylinder with large motion and reversing stable thrust, is expected to be used for numerical control machines by replacing a ball screw with the oil cylinder, and particularly can be used for controlling the numerical control machine of large machinery by using a small servo motor through the hydraulic servo valve.

Description

Electro-hydraulic servo valve with stroke braking controlled by servo motor

Technical Field

The invention belongs to the technical field of hydraulic reversing valves, and particularly relates to an electro-hydraulic servo valve with stroke braking controlled by a servo motor.

Background

At present, the traditional theory at home and abroad considers that the travel brake can only be used in the low-speed range of the workbench, and the travel brake is applied in the low-speed range at present.

In the existing electro-hydraulic stepping motor, a hydraulic valve is a slide valve, a stepping motor rotates, and the rotation motion is converted into axial motion through threads, so that the precision is reduced, the reverse idle stroke is increased, and the application is few.

The existing numerical control machine tool cannot leave a ball screw, the ball screw is complex in structure, the requirement on installation accuracy is high, the heating capacity of a nut is large, and the heat is transferred to the screw to enable the temperature of the screw to rise and extend to influence the accuracy. When the rolling screw stops rotating, the temperature is rapidly reduced, and the precision is greatly influenced.

The hydraulic transmission uses an oil cylinder to drive a workbench, has the advantages of stable movement and reversing, large driving force and the like, but has poor reversing precision and slow reversing speed, and is considered to be impossible to be used for a numerical control machine tool.

Disclosure of Invention

The invention provides the electro-hydraulic servo valve with the stroke brake controlled by the servo motor, and the oil cylinder is accurately and quickly controlled by the servo motor. The hydraulic transmission system with stable movement and reversing and larger driving force realizes the effect that the starting speed and the braking stop position can be accurately and quickly controlled.

In order to realize the technical problem, the invention provides an electro-hydraulic servo valve with a servo motor controlling stroke braking, which comprises a servo motor, a PT valve, an AB valve, a valve body and a feedback device, wherein the servo motor is connected with the PT valve; the servo motor is arranged at one end of the valve body and is connected with the outer side end of the PT valve arranged in the inner cavity of the valve body through a coupler; the AB valve is arranged in the inner cavity of the valve body and is opposite to the end face of the PT valve; the outer ends of the AB valve and the PT valve and the opening part of the valve body are respectively provided with a bearing for limiting; four slotted holes are arranged on the inner side wall of the valve body; the four slotted holes are inwards connected with P, T, A, B valve ports on the end faces of the PT valve and the AB valve respectively, and are outwards communicated with a P oil way, a T oil way, an A oil way and a B oil way respectively; the PT valve and the AB valve are end face rotary valves; and the outer end of the AB valve is connected with a feedback device arranged at the other end of the valve body.

Furthermore, the port A and the port B of the AB valve are waist-shaped and are oppositely arranged; the T valve port of the PT valve is a waist-shaped notch, and the P valve port of the PT valve is circular; and a small valve port is arranged at the position where the T valve port is firstly contacted with the A valve port and the B valve port in the rotating process of the PT valve, and the small valve port is a 60-degree notch.

Furthermore, a small kidney-shaped groove is formed in the end face, opposite to the PT valve, of the AB valve, and the small kidney-shaped groove is matched with a cylindrical pin on the end face, opposite to the PT valve, of the PT valve so as to limit the moving range of the two valves.

Further, the feedback device is a feedback gear, and the AB valve is connected with the feedback gear through a flat key; the feedback gear realizes feedback through meshing with a rack at the bottom of the workbench.

Furthermore, the AB valve is connected with the hydraulic motor into a whole through a shaft, and the hydraulic motor rotates to directly drive the AB valve to realize feedback.

Further, the feedback device comprises a feedback servo motor and a linear encoder; the feedback servo motor is connected with the AB valve and then connected with a linear encoder arranged on the workbench to realize feedback.

Compared with the prior art, the invention has the beneficial effects that: simple structure, control accuracy is higher. The hydraulic oil cylinder provides strong thrust for the workbench, and the electro-hydraulic servo valve controls the precision of the workbench, so that the thrust is provided and the precision is controlled separately, and the control precision is not influenced by the hydraulic oil cylinder.

Drawings

FIG. 1 is a vertical cross-sectional view of an electro-hydraulic servo valve with stroke braking controlled by a servo motor according to the present invention.

FIG. 2 is a schematic diagram of the relationship between the motion of the working table and the motion of the oil cylinder when the gear and the rack are used for feedback.

FIG. 3 is a diagram showing the relationship between the ports of the AB valve and the PT valve when the electro-hydraulic servo valve for controlling the stroke brake by the servo motor is in different working states.

Description of reference numerals: 1. a servo motor; 2. a coupling; 3. a PT valve; 3.1, cylindrical pins; p, P valve port; t, T valve port; 4. an AB valve; 4.1, a small waist-shaped groove; A. a valve port; B. valve port B; 5. a valve body; 5.1, a first bearing; 5.2, a second bearing; 6. a feedback gear; 7. a slot; 8. a rack; 9. a work table; 10. a small valve port.

Detailed Description

According to the embodiment of the invention, the electro-hydraulic servo valve (hereinafter referred to as the 'present valve') controlled by the servo motor and used for stroke braking can quickly and accurately control the whole process of starting, speed, braking and stopping of actuating mechanisms such as oil cylinders or hydraulic motors. In particular, the device can perform quick stroke braking and stop at various speeds in the same place on the premise of no impact. The oil cylinder is expected to replace a ball screw to control the numerical control machine tool, and a low-power servo motor can be used for controlling a large numerical control machine tool.

According to the embodiment of the invention, the hydraulic valve is controlled by utilizing the servo motor which has high precision and can accurately control the rotating speed and the rotating angle, the control on the hydraulic actuating element is implemented, and the function and the precision of the hydraulic machine are improved. Because the servo motor rotates, the hydraulic valve also adopts two rotary valves, one is a radial rotary valve, and the rotary valve is very hard to rotate, so the valve adopts a newly designed end face rotary valve which rotates easily and uniformly, and valve ports with different shapes are designed on the end face, thereby leading a plurality of problems in hydraulic transmission to be solved.

In order to solve the problem that the oil cylinder cannot be numerically controlled in the prior art, the invention provides an electro-hydraulic servo valve with a servo motor for controlling stroke braking. The scheme is explained in detail below with reference to the drawings.

Embodiment 1, as shown in fig. 1, 2 and 3, the electro-hydraulic servo valve with stroke braking controlled by a servo motor comprises a servo motor 1, a PT valve 3, an AB valve 4, a valve body 5 and a feedback gear 6, wherein the AB valve 4 is connected with the feedback gear 6 through a flat key; the servo motor 1 is arranged on the outer side of one end of the valve body 5 and is connected with the outer side end of the PT valve 3 arranged in the inner cavity of the valve body 5 through a coupler 2; the AB valve 4 is arranged in the inner cavity of the valve body 5 and is opposite to the end face of the PT valve 3; a second bearing 5.2 is arranged between the outer side end of the AB valve 4 and the valve body 5, and a first bearing 5.1 is arranged between the outer side end of the PT valve 3 and the valve body 5 and used for limiting the PT valve 3 and the AB valve 4; four circular ring groove holes 7 are formed in the inner side wall of the valve body 5, two circular ring groove holes 7 are formed in the inner side wall of the valve body 5 corresponding to the specific PT valve 3 and the AB valve 4 respectively, the groove holes 7 are communicated with P, T, A, B in the end faces of the PT valve 3 and the AB valve 4 inwards respectively, strip grooves in the excircle of the PT valve and the AB valve are aligned with grooves in the inner hole of the valve body respectively, and oil paths are always kept communicated in the rotating process of the PT valve and the AB valve. The PT valve 3 and the AB valve 4 are end face circular rotary valves. The opposite end surfaces of the AB valve 4 and the PT valve 3 are provided with a small kidney-shaped groove 4.1, and the small kidney-shaped groove 4.1 is matched with a cylindrical pin 3.1 arranged on the opposite end surfaces of the PT valve 3 to limit the relative moving range of the two valves.

On the basis of the technical scheme, further, in order to enable the electro-hydraulic servo valve controlled by the servo motor to brake in a stroke mode to be higher in control precision, the opening and closing regulation keeps consistency on flow control, and meanwhile blocking is effectively prevented; as shown in fig. 3, the port a and the port B of the AB valve 4 are waist-shaped and are oppositely arranged; the T-port T of the PT valve 3 is also waist-shaped, and the T-port T is firstly contacted with the small ports 10 arranged on the A-port A and the B-port B in the rotating process of the PT valve 3.

In the embodiment of the invention, the shapes of the valve ports on the end surfaces of the AB valve 4 and the PT valve 3 can be designed by technicians according to the requirements of the hydraulic mechanical functions.

Illustratively, the small valve port 10 is a 60 ° notch. The minimum speed of the cylindrical grinder in the prior art is 0.1m/min, the area of the valve port is very small when the cylindrical grinder operates at the minimum speed, and foreign matters in hydraulic oil can block the small holes to enable the speed of the workbench to be continuously reduced or even stopped. The shape of the valve port at the lowest speed is related to the probability of blockage, and the valve port is most easily blocked in the same area and the shape of the gap. The circle is least prone to clogging, but the size adjustment is less easily controlled. The regular triangle is not easy to block, and the area can be adjusted by moving one side. Therefore, the valve adopts a 60-degree triangular small valve port 10 at the lowest speed, and the valve port of the valve is in a regular triangle regardless of the size.

Besides the gear and rack feedback, the valve has a plurality of feedback methods:

in one embodiment of the invention, the feedback device 6 comprises a feedback servo motor and a linear encoder; the feedback servo motor is connected with the AB valve and then connected with a linear encoder arranged on the workbench to realize feedback.

Illustratively, the AB valve 4 is connected with a hydraulic motor shaft into a whole, and the rotation of the hydraulic motor directly drives the AB valve 4 to realize feedback.

Preferably, when the servo motor 1 moves in the reverse direction, the rotation angle is larger than the corresponding rotation angle of the moving distance of the workbench 9 by a required idle stroke angle.

In one embodiment of the invention, the electro-hydraulic servo valve controlled by the servo motor to brake the stroke comprises a valve body 5, a P oil passage and a T oil passage on a PT valve 3, and a valve body 5, an A oil passage and a B oil passage on an AB valve 4, which form throttling; when the PT valve 3 is positioned at a station a in the figure 3, the workbench 9 stops moving, when the PT valve 3 is anticlockwise rotated at a station B, high-pressure oil enters a right cavity of the oil cylinder from the oil duct P through the oil duct B, a triangular small valve port between the oil duct A and the oil duct T is used for controlling the speed, the oil cylinder pushes the workbench 9 and the rack 8 to move leftwards, meanwhile, the rack 8 drives the feedback gear 6 to anticlockwise rotate so as to drive the AB valve 4 to anticlockwise rotate, the AB valve 4 closes the valve port T and the valve port P of the PT valve 3, and the workbench 9 stops; how much distance the workbench 9 needs to move leftward only by controlling the corresponding counterclockwise rotation angle of the servo motor 1, how much distance the workbench 9 needs to move rightward only by controlling the corresponding clockwise rotation angle of the servo motor 1.

The working principle of the machine tool working table fed back by a gear and a rack is taken as an example: when the PT valve 3 is at P, A, B, T (fig. 3a) not communicating with each other, the table is stopped. When the servo motor 1 drives the PT valve 3 to rotate at a constant speed in a counterclockwise direction, the AB valve does not move, the motion of the PT valve 3 enables high-pressure oil to enter a right cavity of the oil cylinder through an oil path B, the piston is pushed to move leftwards, oil in a left cavity of the piston flows back to an oil tank from an oil path T through an oil path A, the workbench 9 also moves leftwards simultaneously and is fed back to the AB valve 4 through a rack 8 and a feedback gear 6 to rotate anticlockwise, the area of an oil return valve port is gradually increased due to the fact that the workbench is started at a later speed, the speed of the workbench 9 is increased continuously until the workbench 9 is increased to enable the rotating speed of the AB valve 4 to be the same as that of the PT valve 3, the valve port area formed by the AB valve 4 and the PT valve 3 is fixed (fig. 3B), and the workbench 9 starts to change from accelerated motion to constant motion. If the servo motor and the PT valve stop at a certain position, at the moment of stopping, the valve port is still the original size, the AB valve is delayed for a certain distance, the workbench 9 continues to move leftwards at the original speed, the movement is fed back to the AB valve 4 and also rotates anticlockwise, the area of the oil return valve port is gradually reduced from fast to slow, and the workbench stops (in the process of stroke braking) until the AB valve rotates to a position which is not communicated with P, A, B, T of the PT valve (in fig. 3 c). In the process of the movement, the angle degree of the PT valve 3 driven by the servo motor is the same as the angle degree of the AB valve 4 driven by the workbench 9, so that the workbench can move by the corresponding angle number only by the servo motor. Since the valve has reverse idle stroke, the value of the reverse idle stroke is added to the first time the workbench is reversed.

The oil return port of the valve is formed by the kidney-shaped groove of the AB valve 4 and the kidney-shaped notch of the PT valve 3, and is a circular arc-shaped gap (shown in figure 3b) in detail, and the maximum area of the valve can meet the area required by the highest speed of a workbench. Its width determines the speed of braking, its width is small, and its braking speed is slow, braking distance is long and stopping speed is slow. The width is large, the braking speed is high, the braking distance is short, and the stopping speed is high. But a certain degree of width would give rise to an impact, which is not allowed. The optimum width is the maximum width that does not produce an impact.

The pitch circle radius of the feedback gear is also related to the braking speed, the pitch circle radius is large, the braking speed is low, and the braking distance is long; the pitch circle has small radius, high braking speed and short braking distance, but the impact can be generated when the radius is too small and the braking speed is too high. And the pitch circle radius of the feedback gear is increased. And reducing the width of the oil return opening can eliminate the impact.

If the servo motor 1 always rotates in a certain direction, the workbench 9 also moves in a certain direction, when the workbench is low in speed, the area of the oil return valve port is increased from small to large, the speed of the workbench 9 is increased all the time, until the oil return valve port is increased to a rotating speed corresponding to the workbench speed and the servo motor 1, at the moment, the workbench 9 moves at a constant speed along with the servo motor 1, the excrement and urine of the valve port are fixed, only a distance is reserved after the workbench 9, the length of the distance is related to the speed of the workbench, the speed of the workbench is high, the distance after the delay is large, the area opened by the valve port is also large, the speed of the workbench is low, the distance after the delay is small, and the area opened by the valve port is also small. When the servo motor 1 stops at a certain position, the PT valve 3 stops rotating, the oil return valve port is opened at the moment, so that the workbench can also move forward, the workbench 9 moves forward, the feedback gear 6 drives the AB valve 4 to rotate, the valve port is reduced, the delay amount is also reduced, when the delay amount is reduced to zero, the valve port is also closed at the same time, and the workbench 9 stops. The process of stopping the working table 9 is a perfect process of stroke braking. The current hydraulic control box for stroke braking has the advantages that the flow area of a valve port is very large at the beginning of stroke braking, even larger than the flow area of an oil pipe of a machine tool, for example, an M9120 multipurpose grinding machine is taken, the whole braking process workbench needs to travel by 14mm, but the actual braking distance is only less than 3mm at the highest speed. When the workbench operates at the lowest speed of 0.1m/min, the actual braking distance is only 0.1 mm. But the table takes a 14mm stroke per brake reading. The vast majority of the braking stroke is the ineffective braking stroke, so the braking distance is long and the reversing speed is slow. This valve can accomplish through the feedback process, and the size of valve port is unanimous with workstation speed, and in case servo motor 1 stall, actual braking begins immediately. There is no ineffective braking stroke at all speeds, so the commutation speed is extremely fast.

Meanwhile, when the workbench 9 moves at a constant speed, the delay of the workbench 9 is related to the speed. The valve port with large delay amount is opened more, and the valve port with small delay amount with low speed is opened less, so that the high-speed braking stroke is long, the low-speed braking stroke is short, and the high-speed braking, the medium-speed braking and the low-speed braking are stopped at the same point of the closing of the oil return valve port finally. Therefore, the punching amount of the time brake does not exist, and the differential speed of the travel brake does not exist.

If the workbench 9 moves leftwards for multiple times of stay, the left surface of the teeth of the rack 8 is abutted against the feedback gear 9, and the stay position is the position that the AB valve 4 closes the oil return valve port from the counterclockwise direction, so the distance of each walking of the workbench is the same as the pitch arc length of a section of the feedback gear with the same rotating angle of the servo motor 1. The same is true if the table is moved to the right. However, a certain error exists between the leftward movement and the rightward movement, which is caused by the clearance of the gear and the rack and the covering amount of the valve port, and the error is added in the process only during reversing, so that the error is easy to realize in numerical control. There are also many ways to reduce the above error.

The servo motor 1 of the valve only gives an instruction to the movement of the workbench 9, and the workbench 9 is pushed by oil pressure. The rack 8 is only used for pushing the feedback gear 6, and the transmission torque is small. The heat generated by the whole transmission is very small. The hydraulic pressure of the valve only plays a role of pushing the workbench and does not participate in the control of precision. Neither the change in oil temperature nor a small amount of leakage has an effect on accuracy. For example, when the workbench moves leftwards, a small amount of leakage exists at the position B on the right side of the oil cylinder, the speed of the workbench is reduced, the feedback speed is reduced, the area of an oil return valve port is increased, and the workbench can be accelerated to the speed corresponding to the servo motor. If a small amount of leakage exists at the oil pipe A on the left side of the oil cylinder, the speed of the workbench is accelerated, the feedback speed is accelerated, the area of an oil return valve port is reduced, and the workbench is decelerated to the speed corresponding to the servo motor 1. The hydraulic pressure does not affect the motion accuracy. The stop position of the workbench and the closed position of the oil return valve port are determined. Regardless of the oil pressure, the oil temperature, and the small amount of oil leakage. Therefore, the moving speed and the stop position of the worktable 9 are determined only by the servo motor 1, and the precision is reliable. The valve is expected to replace a ball screw with the oil cylinder for a numerical control machine tool, and the hard rail can be completely used due to the large thrust of the oil cylinder, so that the precision of the machine tool can be further improved. The valve can also be used for controlling a large numerical control machine tool by using a low-power servo motor.

Compared with the prior art, the technical scheme of the invention has the advantages of simple structure, small heat productivity in the operation process and higher control precision, the precision of the workbench is controlled by the electro-hydraulic servo valve, and the thrust of the workbench is controlled by the hydraulic oil cylinder, so that the thrust and the precision are controlled separately, and the control precision is not influenced by the hydraulic oil cylinder; through the setting of structure make, the size of valve port is unanimous with workstation moving speed is correlated with, and servo motor stall, and the braking is immediately started, has effectively eliminated invalid braking stroke, and the speed of switching-over is faster.

Claims

1. An electro-hydraulic servo valve with stroke braking controlled by a servo motor, characterized in that: the device comprises a servo motor, a PT valve, an AB valve, a valve body and a feedback device; the servo motor is arranged at one end of the valve body and is connected with the outer side end of the PT valve arranged in the inner cavity of the valve body through a coupler; the AB valve is arranged in the inner cavity of the valve body and is opposite to the end face of the PT valve; the outer ends of the AB valve and the PT valve and the opening part of the valve body are respectively provided with a bearing for limiting; four slotted holes are formed in the inner side wall of the valve body; the four slotted holes are inwards connected with P, T, A, B valve ports on the end faces of the PT valve and the AB valve respectively, and are outwards communicated with a P oil way, a T oil way, an A oil way and a B oil way respectively; the PT valve and the AB valve are end face rotary valves; and the outer side end of the AB valve is connected with a feedback device arranged at the other end of the valve body.

2. The electro-hydraulic servo valve for stroke braking controlled by a servo motor of claim 1 wherein: the valve port A and the valve port B of the AB valve are in a kidney shape which is arranged oppositely; the T valve port of the PT valve is a waist-shaped notch, and the P valve port of the PT valve is circular; and a small valve port is arranged at the position where the T valve port is firstly contacted with the A valve port and the B valve port in the rotating process of the PT valve, and the small valve port is a 60-degree notch.

3. The electro-hydraulic servo valve for stroke braking controlled by a servo motor of claim 2 wherein: and the opposite end surfaces of the AB valve and the PT valve are provided with a small kidney-shaped groove which is matched with a cylindrical pin on the opposite end surfaces of the PT valve so as to limit the moving range of the two valves.

4. Electro-hydraulic servo valve with stroke braking controlled by a servo motor according to any of claims 1 to 3, characterized in that: the feedback device is a feedback gear, and the AB valve is connected with the feedback gear through a flat key; the feedback gear realizes feedback through meshing with a rack at the bottom of the workbench.

5. Electro-hydraulic servo valve with stroke braking controlled by a servo motor according to any of claims 1 to 3, characterized in that: the AB valve is connected with the hydraulic motor shaft into a whole, and the hydraulic motor rotates to directly drive the AB valve to realize feedback.

6. Electro-hydraulic servo valve with stroke braking controlled by a servo motor according to any of claims 1 to 3, characterized in that: the feedback device comprises a feedback servo motor and a linear encoder; the feedback servo motor is connected with the AB valve and then connected with a linear encoder arranged on the workbench to realize feedback.