A digital hydraulic cylinder

Abstract

The present invention discloses a digital hydraulic cylinder, which comprises a digital servo hydraulic control valve and a hydraulic cylinder. The digital servo hydraulic control valve includes a valve body, a digital motor, a bushing, a valve core, a sensor and a transmission assembly. An inner cavity is provided in the upper part of the valve body, an axial hole communicating with the inner cavity is provided in the lower part, and oil passage through holes respectively communicating with the rod chamber and the rodless chamber are formed in the valve body; the valve core is movably arranged in the axial hole through a bearing, the upper end of the valve core penetrates out of the inner cavity and is connected with the sensor, and the lower end penetrates out of the valve body and is connected with a lead screw; the bushing is threadedly connected to the valve core, and the upper part of the bushing is located in the inner cavity; the digital motor is fixed on the side surface of the upper part of the valve body, one end of the transmission assembly is connected with the upper part of the bushing, and the other end extends out of the valve body and is connected with the digital motor. The digital motor can drive the bushing to move up and down on the valve core through the transmission assembly. The present invention effectively solves the technical problems of small torque, easy breakage of the lead screw and difficult realization of signal feedback in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of digital cylinders, and particularly to a digital hydraulic cylinder. Background Art

[0002] A digital hydraulic cylinder refers to a new product that combines a stepper or servo motor, a hydraulic slide valve, and a closed-loop position feedback design on a hydraulic cylinder. When the hydraulic oil source is connected, all functions are directly completed by digital pulse signals sent by a digital hydraulic cylinder controller, a computer, or a programmable logic controller to achieve length vector control at different speeds. Due to its high control precision and convenient use, it is increasingly widely used.

[0003] Existing digital hydraulic cylinders basically directly drive and control the movement of the spool of the hydraulic valve by a stepper or servo motor, and are equipped with a mechanical feedback structure in which a ball screw is directly connected to the spool. For example, the patent document with the publication number CN207297964U discloses a mechanically feedback digital hydraulic cylinder with a follow-up valve sleeve. The main shaft of its servo motor is connected to a screw, the other end of the screw is in threaded fit with the internal thread of the spool, the spool is embedded in the valve sleeve, the screw drives the spool to slide axially along the valve sleeve, the valve sleeve is embedded in the valve body, multiple bosses are provided on the outer side wall of the spool, and flow control windows corresponding to the bosses of the spool are provided on the inner side wall of the valve sleeve. The spool and the valve sleeve cooperate to form a three-position four-way hydraulic valve. An oil passage through hole corresponding to the three-position four-way hydraulic valve is provided radially on the side wall of the valve body. The valve sleeve is provided with an internal thread at the end close to the cylinder block to be in threaded fit with the external thread of the ball screw. The valve sleeve can slide axially along the valve body under the drive of the ball screw. The other end of the ball screw is embedded in the hollow piston rod, and the screw nut is arranged on the piston of the piston rod. Although this technology can achieve dynamic position feedback of the hydraulic cylinder through the follow-up of the valve sleeve and improve the controllability of the spool. However, in practical applications, this technology still has the following technical problems:

[0004] 1. In this technology, the up and down movement of the servo hydraulic control valve bushing is driven by the rotation of the screw installed inside the piston rod of the hydraulic cylinder. However, due to the long stroke and limited diameter of the screw, the output torque is small. And the diameter of the bushing is small, and the internal and external friction forces on it by the valve body and the spool are large, resulting in limited output flow. Thus, this technology is only applicable to occasions with small flow rates, such as small hydraulic cylinders, short piston rod strokes, and slow piston rod movement speeds. On the contrary, if it is applied to occasions with large flow rates, such as large hydraulic cylinders, long piston rod strokes, and fast piston rod movement speeds, it is easy to cause the screw to break.

[0005] 2. The servo hydraulic control valve in this technology only has mechanical feedback and does not have electrical feedback. In the case where the external structure is limited and there is no installation position for the electrical feedback sensor, it cannot be applied to occasions with electrical feedback. Summary of the Invention

[0006] The object of the present invention is to overcome the above-mentioned technical problems existing in the prior art, and provide a digital hydraulic cylinder. By increasing the torque of the motor, the digital cylinder can be applied to occasions with large flow rates, such as larger hydraulic cylinders, longer piston rod strokes, and faster piston rod movement speeds. By providing a position for the installation of the electrical feedback sensor, the digital cylinder has both mechanical feedback function and electrical feedback function; at the same time, the valve core is directly connected to the lead screw as feedback, with a smaller required torque, a larger optional range of the valve core diameter, and it is not easy to cause the lead screw to break. Compared with the prior art structure of directly driving the valve core by a motor and using a bushing as the lead screw feedback, the technical problems of small torque, easy breakage of the lead screw, and difficult signal feedback in the prior art are effectively solved.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A digital hydraulic cylinder, characterized in that it includes a digital servo hydraulic control valve and a hydraulic cylinder;

[0009] The hydraulic cylinder includes a cylinder block, a piston rod, a lead screw and a lead screw nut. One end of the piston rod is located outside the cylinder block, and the other end is located inside the cylinder block for separating the cylinder block into a rod chamber and a rodless chamber. The lead screw is nested in the piston rod through the lead screw nut;

[0010] The digital servo hydraulic control valve includes a valve body, a digital motor, a bushing, a valve core, a sensor and a transmission component. The upper part of the valve body is provided with an inner cavity, the lower part is provided with an axial hole communicating with the inner cavity, and the valve body is provided with oil passage through holes respectively communicating with the rod chamber and the rodless chamber; the valve core is movably arranged in the axial hole through a bearing. The upper end of the valve core passes through the inner cavity and is connected to the sensor, and the lower end passes through the valve body and is connected to the lead screw; the bushing is threadedly connected to the valve core, and the upper part of the bushing is located in the inner cavity; the digital motor is fixed on the side of the upper part of the valve body, one end of the transmission component is connected to the upper part of the bushing, and the other end extends out of the valve body and is connected to the digital motor. The digital motor can drive the bushing to move up and down on the valve core through the transmission component.

[0011] The upper part of the bushing is provided with driving teeth. The transmission component includes a first bevel gear and a second bevel gear. The second bevel gear meshes with the driving teeth. One end of the first bevel gear meshes with the second bevel gear, and the other end extends out of the valve body and is connected to the digital motor.

[0012] The number of the transmission components is at least one set.

[0013] The oil passage through holes include an oil inlet and outlet hole, an oil inlet hole and an oil outlet hole. The bushing is provided with flow control windows corresponding to the oil passage through holes respectively. The valve core is integrally formed with protrusions corresponding to the flow control windows. The valve body is respectively connected to the rod chamber and the rodless chamber through the oil inlet and outlet hole.

[0014] An upper cover plate for sealing the inner cavity is fixed to the upper end of the valve body, and the hydraulic cylinder is fixed to the lower end of the valve body for sealing the axial hole.

[0015] A through hole for the valve core to pass through is provided on the upper cover plate.

[0016] The advantages of adopting the present invention are as follows:

[0017] 1. The key improvement of the digital hydraulic cylinder of the present invention lies in the use of a digital servo hydraulic control valve with a specific structure to control the hydraulic cylinder. In the digital servo hydraulic control valve, the present invention fixes the digital motor on the side of the valve body and directly drives the bushing to lift by the digital motor to realize the control of the valve, and uses a valve core with a larger diameter as the feedback of the lead screw. Compared with the existing structure of directly driving the valve core by the motor and using the bushing as the lead screw feedback, on the one hand, the torque of the digital motor can be increased through the transmission component, so that the valve can be applied to occasions with larger flow rates such as larger hydraulic cylinders, longer piston rod strokes, and faster piston rod movement speeds, and at the same time, it is not easy to cause the lead screw to break. On the other hand, a position is provided for the installation of the electrical feedback sensor. Specifically, the sensor can be directly installed on the end face of the valve body to test the position of the valve core, so that the valve has both mechanical feedback function and electrical feedback function, which is beneficial to adapting to different occasions. In addition, the present invention can also meet the accurate control of position, stroke, speed, and pressure, and has the advantage of high control accuracy.

[0018] 2. The present invention uses a bevel gear to cooperate with a driving tooth to drive the bushing, which has the advantages of increasing torque, stable force transmission, simple structure, and high control efficiency.

[0019] 3. The number of transmission components in the present invention is at least one set, and can be set to multiple sets in actual use, so that other components can be externally connected through the transmission components to realize expansion functions such as manual drive, power-off protection, and redundant drive.

[0020] 4. The present invention can form a three-position four-way valve through the cooperation of a flow control window, a convex platform, and an oil passage through hole to control the hydraulic cylinder, which is beneficial to realizing the accurate control and stable control of the hydraulic cylinder.

[0021] 5. The present invention seals the inner cavity and the axial hole through the upper cover plate and the hydraulic cylinder respectively. First, it is beneficial to the installation and later maintenance of each component. Second, directly using the hydraulic cylinder to seal the axial hole can reduce the number of cover plates, which is beneficial to reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic structural diagram of the present invention.

[0023] The labels in the figure are: 1. Sensor, 2. First bevel gear, 3. Upper cover plate, 4. Second bevel gear, 5. Digital motor, 6. Valve body, 7. Bushing, 8. Spool valve, 9. Cylinder block, 10. Piston rod, 11. Lead screw, 12. Lead screw nut. Detailed implementation mode

[0024] The present invention provides a digital hydraulic cylinder, as Figure 1 shown. This digital hydraulic cylinder includes a digital servo hydraulic control valve and a hydraulic cylinder, and their structures are as follows:

[0025] The hydraulic cylinder includes a cylinder block 9, a piston rod 10, a lead screw 11 and a lead screw nut 12. One end of the piston rod 10 is located outside the cylinder block 9, and the other end is located inside the cylinder block 9 to divide the cylinder block 9 into a rod chamber and a rodless chamber. A central counterbore is provided on the piston rod 10, and the lead screw nut 12 is fixed at the opening of the central counterbore. The lead screw 11 is nested in the central counterbore of the piston rod 10 through the lead screw nut 12. After connection, the lead screw 11 can only make rotational motion, and the piston rod 10 can only move up and down in the illustrated direction under the action of internal friction and external load and cannot rotate.

[0026] The digital servo hydraulic control valve includes a valve body 6, a digital motor 5, a bushing 7, a spool valve 8, a sensor 1, a transmission component and an upper cover plate 3. Among them,

[0027] An inner cavity is provided in the upper part of the valve body 6. The inner cavity can be a circular structure or a square structure, and can be specifically opened downward from the upper end surface of the valve body 6.

[0028] A cylindrical central hole is provided in the lower part of the valve body 6, and the central hole communicates with the inner cavity.

[0029] In addition, a plurality of oil passage through holes are provided on the valve body 6, specifically including oil inlet and outlet holes AB, an oil inlet hole P and an oil outlet hole T. The valve body 6 can communicate with the rod chamber through the oil inlet and outlet hole A and with the rodless chamber through the oil inlet and outlet hole B.

[0030] The upper cover plate 3 is fixed to the upper end of the valve body 6 to block the inner cavity, and the hydraulic cylinder is fixed to the lower end of the valve body 6 and can be used as a lower cover plate to block the central hole, thereby reducing the amount of cover used and lowering the cost. In addition, through holes for the spool valve 8 to pass through are provided on both the upper cover plate 3 and the upper end of the hydraulic cylinder.

[0031] The spool valve 8 is movably arranged in the central hole through a bearing. The upper end of the spool valve 8 sequentially passes through the inner cavity and the upper cover plate 3 and then is connected to the sensor 1. The sensor 1 can collect the rotation angle of the spool valve 8, so as to provide an electrical feedback signal for the control system. The lower end of the spool valve 8 passes through the upper end of the hydraulic cylinder and then extends out of the valve body 6 and extends into the cylinder block 9 and is connected to the lead screw 11, and the spool valve 8 can only rotate in the valve body 6 and cannot move up and down.

[0032] The bushing 7 is threadedly connected to the spool 8. The upper part of the bushing 7 is located in the inner cavity, and the outer surface of the upper part of the bushing 7 is provided with driving teeth that cooperate with the transmission assembly.

[0033] The digital motor 5 is fixed to the side of the upper part of the valve body 6. One end of the transmission assembly is meshed and connected to the driving teeth, and the other end extends out of the valve body 6 and is connected to the digital motor 5. The transmission assembly drives the bushing 7 through the driving teeth, and the digital motor 5 can drive the bushing 7 to move up and down on the spool 8 through the transmission assembly.

[0034] In addition, flow control windows corresponding to the oil passage through holes are provided on the bushing 7 of the present invention. A boss corresponding to the flow control window is integrally formed on the spool 8. The cooperation of the spool 8, the bushing 7 and the valve body 6 can form a three-position four-way valve with a rotary spool structure (having oil passage through holes P\A\B\T). Figure 1 It shows that the present invention constitutes a three-position four-way valve with oil passage through holes P\A\B\T. In actual application, by changing the relative positions of the bushing 7 and the spool 8, the pressure direction and flow rate of the oil inlet and outlet holes can be changed, so as to control the movement direction, speed and position of the hydraulic cylinder.

[0035] It should be noted that the structure in which the spool 8, the bushing 7 and the valve body 6 cooperate to form a three-position four-way valve is a conventional existing technology and will not be elaborated here.

[0036] Preferably, the transmission assembly includes a first bevel gear 2 and a second bevel gear 4. The second bevel gear 4 is meshed with the driving teeth. One end of the first bevel gear 2 is meshed with the second bevel gear 4, and the other end extends out of the valve body 6 and is connected to the digital motor 5. The present invention uses the first bevel gear 2 and the second bevel gear 4 as the transmission assembly, which can not only increase the transmission torque of the digital motor 5, but also enable the digital motor 5 to be arranged on the side of the valve body 6, thereby providing an installation position for the sensor 1. In actual use, the digital motor 5 can drive the bushing 7 to rotate on the spool 8 through the first bevel gear 2 and the second bevel gear 4, open the flow control window between the bushing 7 and the spool 8, and the oil inlet and outlet holes A / B respectively output pressure oil / return oil or return oil / pressure oil to control the action of the hydraulic cylinder. After the hydraulic cylinder acts, it is connected to the spool 8 through the provided lead screw 11 in a closed-loop manner, driving the spool 8 to rotate, reducing the window between the bushing 7 and the spool 8. When the window between the bushing 7 and the spool 8 is completely closed, the hydraulic cylinder stops moving, and the position of the hydraulic cylinder can be accurately controlled.

[0037] In addition, the present invention can collect the rotation angle of the spool 8 through the sensor 1 to provide an electrical feedback signal for the control system. Specifically, the digital motor 5 is controlled to rotate in the reverse direction through electrical feedback, and the pressure direction and flow rate of the output oil are controlled by controlling the rotation speed of the motor and the time difference of opening / closing the window, so as to control the position, movement direction and speed of the hydraulic cylinder.

[0038] Preferably, since the present invention uses a specific side digital motor 5 to directly drive the lifting of the bushing 7 to achieve valve control, the number of transmission components can also be set to at least one set according to needs. For example, the number of transmission components can be set to two sets or three sets according to needs, so as to externally connect other structures to achieve extended functions such as manual drive, power-off protection, and redundant drive.

[0039] Generally speaking, the present invention adopts mechanisms such as gears and threads, which can effectively amplify the output torque of the digital motor 5, and only requires one-stage hydraulic amplification with a wide flow application range. In addition, traditional servo valves require electrical feedback, while the present invention can adopt either electrical feedback or mechanical closed-loop feedback, with high control precision, and the protection function can be conveniently set, and the position of the controlled object can be accurately maintained even when the control power supply disappears.

[0040] The above is only the specific implementation manner of the present invention. Any feature disclosed in this specification, unless specifically described, can be replaced by other equivalent or similar-purpose alternative features; all the features disclosed, or all the steps in any method or process, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A digital hydraulic cylinder, characterized in that: It includes a digital servo hydraulic control valve and a hydraulic cylinder; The hydraulic cylinder includes a cylinder block (9), a piston rod (10), a lead screw (11) and a lead screw nut (12). One end of the piston rod (10) is located outside the cylinder block (9), and the other end is located inside the cylinder block (9) for dividing the cylinder block (9) into a rod chamber and a rodless chamber. The lead screw (11) is nested in the piston rod (10) through the lead screw nut (12); The digital servo hydraulic control valve includes a valve body (6), a digital motor (5), a bushing (7), a valve core (8), a sensor (1) and a transmission assembly. An inner cavity is provided in the upper part of the valve body (6), and an axial hole communicating with the inner cavity is provided in the lower part. Oil passage through holes respectively communicating with the rod chamber and the rodless chamber are opened on the valve body (6); the valve core (8) is movably arranged in the axial hole through a bearing. The upper end of the valve core (8) passes through the inner cavity and is connected to the sensor (1), and the lower end passes through the valve body (6) and is connected to the lead screw (11); the bushing (7) is threadedly connected to the valve core (8), and the upper part of the bushing (7) is located in the inner cavity; the digital motor (5) is fixed on the side of the upper part of the valve body (6). One end of the transmission assembly is connected to the upper part of the bushing (7), and the other end extends out of the valve body (6) and is connected to the digital motor (5). The digital motor (5) can drive the bushing (7) to move up and down on the valve core (8) through the transmission assembly.

2. The digital hydraulic cylinder according to claim 1, wherein: A driving tooth is provided on the upper part of the bushing (7). The transmission assembly includes a first bevel gear (2) and a second bevel gear (4). The second bevel gear (4) meshes with the driving tooth. One end of the first bevel gear (2) meshes with the second bevel gear (4), and the other end extends out of the valve body (6) and is connected to the digital motor (5).

3. A digital hydraulic cylinder according to claim 1 or 2, characterized in that: The number of the transmission assemblies is at least one set.

4. A digital hydraulic cylinder according to claim 1, characterized in that: The oil passage through holes include an oil inlet and outlet hole, an oil inlet hole and an oil outlet hole. Flow control windows corresponding to the oil passage through holes are provided on the bushing (7). A boss corresponding to the flow control window is integrally formed on the valve core (8). The valve body (6) is respectively communicated with the rod chamber and the rodless chamber through the oil inlet and outlet hole.

5. A digital hydraulic cylinder according to claim 1, characterized in that: An upper cover plate (3) for blocking the inner cavity is fixed at the upper end of the valve body (6). The hydraulic cylinder is fixed at the lower end of the valve body (6) for blocking the axial hole.

6. The digital hydraulic cylinder according to claim 5, wherein: A through hole for the valve core (8) to pass through is opened on the upper cover plate (3).

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