JP7803822B2 - Hydraulic Drive System - Google Patents

Description

The present invention relates to the configuration of a hydraulic drive system. More specifically, the present invention relates to the configuration of a hydraulic drive cylinder actuator system that can automatically remove air from the fluid even if the attitude or position of the cylinder changes within the system.

Hydraulic drive systems are considered to have the high power and durability required for work in harsh environments. Hydraulic cylinders are often used as actuators in construction machinery systems to lift heavy loads, braking systems to transmit high power, and robots for remote work. However, heavy-duty operations can cause other issues such as wear on fittings and parts, as well as the generation of bubbles in the hydraulic oil due to high-pressure cavitation.

To ensure the performance of hydraulic systems, regular maintenance operations to remove air bubbles from hydraulic cylinders are necessary. However, for systems operating in remote areas, it is inconvenient to return the system just for the air removal process. Also, in many applications where cylinders are used as actuators, the cylinders themselves are not necessarily mounted in a fixed position or attitude. Therefore, a remotely operable method for bleeding air from hydraulic systems that works regardless of the cylinder's position or attitude is required.

As background technology in this technical field, there is, for example, technology such as Patent Document 1, which discloses a self-bleeding/deaeration method for a double-acting cylinder actuator system. The cylinder consists of two ports for actuation and another two ports for exhaust, which are configured with sleeves to form channels connecting the upper and lower regions of the cylinder.

Patent Document 2 also proposes a method for removing foreign matter such as air bubbles and small solids from hydraulic cylinders, regardless of the cylinder's fixed attitude or position. This system consists of a cylinder, an additional passage for discharging fluid using a removable maintenance hose, and a mechanism for switching fluids. In the air bleeding process, the maintenance hose is manually connected to the fluid switching mechanism, allowing fluid and air to flow out of the cylinder system.

US Patent Application Publication No. 2011/0072962 Japanese Patent Application Laid-Open No. 2017-155931

The technology described in Patent Document 1 allows air inside a cylinder to be automatically removed by normal piston operation. However, this method relies on the cylinder being fixed in position so that air can be automatically removed from the upper region of the cylinder. This limits the use of cylinder actuators when it is necessary to change the attitude or position of the cylinder itself.

In the technology described in Patent Document 2, the fluid flow and air venting method are determined by the connection of the maintenance hose. This connection must be made manually by an operator, which is not possible in systems operating in remote areas.

The object of the present invention is to provide a hydraulic drive system that can automatically remove air from the fluid while allowing automatic operation regardless of the posture or position of the cylinder actuator.

To solve this problem, the present invention provides a hydraulic drive system including a three-port cylinder actuator having a piston, at least two actuating valves including a first actuating valve and a second actuating valve, an exhaust valve, a tank for storing fluid, a motor pump for supplying the fluid from the tank to the actuating valve, and a control device for controlling all of the actuating valves and the exhaust valve and the motor pump, wherein the first actuating valve is connected to the bottom port of the three-port cylinder actuator, the second actuating valve is connected to the rod port of the three-port cylinder actuator, the exhaust valve is connected to the exhaust port of the three-port cylinder actuator, the rod port and the bottom port are located at each end of the three-port cylinder actuator, and the exhaust port is located at the rod port. and the bottom port, and removes air from the bottom side of the three-port cylinder actuator by controlling the piston to move to the rod side of the three-port cylinder actuator, setting the second operating valve of the rod port to OFF, setting the second operating valve of the rod port to ON to open the exhaust valve of the exhaust port, setting the first operating valve of the bottom port to ON, and allowing air to flow to the tank, and removes air from the rod side of the three-port cylinder actuator by controlling the piston to move to the bottom side of the three-port cylinder actuator, setting the first operating valve of the bottom port to OFF, setting the first operating valve of the bottom port to ON to open the exhaust valve of the exhaust port, setting the second operating valve of the rod port to ON, and allowing air to flow to the tank.

The present invention also provides a hydraulic drive system including a four-port cylinder actuator having a piston, at least two actuating valves including a first actuating valve and a second actuating valve, two exhaust valves including a first exhaust valve and a second exhaust valve, a tank for storing fluid, a motor pump for supplying the fluid from the tank to the actuating valves, and a control device for controlling all of the actuating valves and the exhaust valves and the motor pump, wherein the first actuating valve is connected to a bottom port of the four-port cylinder actuator, the second actuating valve is connected to a rod port of the four-port cylinder actuator, and the first a hydraulic drive system in which the exhaust valve is connected to a first exhaust port of the four-port cylinder actuator, the second exhaust valve is connected to a second exhaust port of the four-port cylinder actuator, the rod port and the bottom port are located at each end of the four-port cylinder actuator, the first exhaust port and the second exhaust port are located at any position between the rod port and the bottom port, and the operating valve and the exhaust valve are set to ON, causing air to flow from the bottom port and the rod port to each exhaust port, thereby removing air from both the bottom side and the rod side.

The present invention makes it possible to realize a hydraulic drive system that can automatically remove air from the fluid while still allowing automatic operation in any cylinder actuator posture or position.

This makes it possible to improve the reliability and availability of robots and manipulators that use hydraulic drive systems.

Other issues, configurations, and advantages will become clear from the description of the following embodiments.

1 is a diagram showing a schematic configuration of a hydraulic drive system according to a first embodiment; FIG. 10 is a diagram showing a schematic configuration of a hydraulic drive system according to a second embodiment. FIG. 10 is a diagram showing a schematic configuration of a hydraulic drive system according to a third embodiment. FIG. 10 is a diagram showing a schematic configuration of a hydraulic drive system according to a fourth embodiment. FIG. 10 is a diagram showing a schematic configuration of a hydraulic drive system according to a fifth embodiment. FIG. 10 is a diagram showing a schematic configuration of a hydraulic drive system according to a sixth embodiment. FIG. 13 is a diagram showing a schematic configuration of a hydraulic drive system according to a seventh embodiment. FIG. 13 is a diagram showing a schematic configuration of a hydraulic drive system according to an eighth embodiment. FIG. 13 is a diagram showing a schematic configuration of a hydraulic drive system according to a ninth embodiment. FIG. 16 is a diagram showing a schematic configuration of a hydraulic drive system according to a tenth embodiment. FIG. 16 is a diagram showing a schematic configuration of a hydraulic drive system according to an eleventh embodiment.

Embodiments of the present invention will be described below using the drawings. Note that identical components in each drawing will be assigned the same reference numerals, and detailed descriptions of overlapping parts will be omitted.

The following description is an example of a proposed embodiment and does not limit the scope of the claims. The operating principle of the air removal method is also an example provided to enable those skilled in the art to implement it, and is not limited to the claims. In this disclosure, air refers to foreign objects trapped in a hydraulic system, such as bubbles, gas, or small solid objects.

Referring to Figure 1, a hydraulic drive system according to a first embodiment of the present invention will be described.

The main components of Example 1 of the present invention are shown in Figure 1. This example is composed of a three-port cylinder actuator 1, in which a first port (bottom port 11) is connected to a bottom hose 21, a second port (rod port 12) is connected to a rod hose 22, and a third port (exhaust port 13) is connected to an exhaust hose 23. The bottom hose 21 is connected to an actuated valve (two-way valve) 31, and the rod hose 22 is connected to an actuated valve (two-way valve) 32. The exhaust hose 23 is connected to an exhaust valve (one-way valve) 33, which connects it to a tank 8.

The motor pump 7 supplies fluid from the tank 8 to each of the actuated valves 31, 32 and connects each of the actuated valves 31, 32 to the tank 8, allowing fluid to flow from the bottom port 11 to the tank 8 or from the rod port 12 to the tank 8. In other words, each of the actuated valves 31, 32 is a type of two-way valve. A control device 100 is used to control the signals of all of the valves 31, 32, 33 and operate the motor pump 7 accordingly.

Generally, the rod port 12 and bottom port 11 are configured at each end of the cylinder, either on the same side or on opposite sides. However, the exhaust port 13 can be located anywhere between the locations of the rod port 12 and bottom port 11, either on the same side or on the opposite side. The example in Figure 1 shows the rod port 12 and bottom port 11 configured on the same side at each end of the cylinder, and the exhaust port 13 configured on the opposite side.

Air is removed by controlling the actuation valves 31 and 32 to move the piston 15, allowing fluid to flow from the bottom port 11 to the exhaust port 13 or from the rod port 12 to the exhaust port 13. For example, actuation valve 31 is set to ON (pump) to connect the fluid supplied by the motor pump 7 to the bottom port 11, actuation valve 32 is set to ON (tank) to connect the rod port 12 to the tank 8, and exhaust valve 33 is set to OFF. In this state, the piston 15 moves to the rod side of the cylinder until it reaches the end.

Next, the operating valve 32 is set to OFF and the exhaust valve 33 is set to ON (tank) so that the fluid containing air 200 flows from the bottom port 11 to the exhaust port 13 and reaches the tank 8. The air 200 on the rod side can then be removed using a similar procedure. First, the piston 15 is moved to the bottom side, and the operating valve 31 is turned OFF on the bottom side to stop the movement of the piston 15, allowing the fluid containing air 200 to flow from the rod port 12 to the exhaust port 13.

When moving the piston 15 to either the rod side or the bottom side, it does not necessarily have to be moved to the end of the three-port cylinder actuator 1. The position of the piston 15 can be determined by the opening time of the operating valves 31, 32, depending on the position of the exhaust port 13. Therefore, the time it takes for the piston 15 to move and stop near the left or right side of the exhaust port 13 can be shortened. Furthermore, both orders for removing air from the bottom port 11 to the exhaust port 13 or from the rod port 12 to the exhaust port 13 are included in this disclosure.

The hydraulic drive system and air removal method of this embodiment can be applied to either direct contact or remote applications. Direct contact applications mean that all components can be directly contacted by a human/operator, while remote applications mean that some components are located close to the human/operator and other components are located remotely.

For example, in remote applications, typically at least the three-port cylinder actuator 1 is located on the remote side for operation and is connected by long hoses 21, 22, and 23, with the other components located on the operator side. Other possible component arrangements are also included in this disclosure, such as locating the three-port cylinder actuator 1 and exhaust valve 33 on the remote side, locating all valves 31, 32, and 33 on the remote side, or locating all components except the control device 100 on the remote side.

In Figure 1, the supply fluid is stored in the same tank 8 as the removal fluid. However, this is not necessary, and separate tanks 8 for the supply fluid and removal fluid are possible. The removed fluid can be first filtered before being returned to the same tank 8. Also, depending on the environment and type of fluid, air can be discharged directly to the environment rather than returned to tank 8. For example, if the working fluid is water and the hydraulic actuator is intended for deep-sea operations, there is no problem if the fluid and air are removed to the environment. Also, seawater can be used as the fluid, as in tank 8.

Although it has been described that only the motor pump 7 is used to supply fluid, this is not a limitation. It is also possible to add relief valves, regulators, check valves, or other components that can help the motor pump 7 supply a stable fluid pressure or flow. Furthermore, each of the operating valves 31 and 32 is not limited to a single valve with a three-port structure, but can also be configured to function as a three-port two-way valve by combining two one-way valves. The exhaust valve 33 is also not limited to a one-way valve type, but can be any ON-OFF valve that can allow or stop fluid flow.

The system configuration is not limited to a single three-port cylinder actuator 1; multiple three-port cylinder actuator systems are also possible. One configuration example is to use multiple components except for the tank 8. It is also possible to connect multiple valves and cylinder actuators using a single tank 8 and a single motor pump 7.

This key configuration allows the exhaust port 13 and piston position to be used to remove trapped air within the hydraulically driven cylinder actuator system, even when the cylinder body is set to any position.

Referring to Figure 2, a hydraulic drive system according to a second embodiment of the present invention will be described.

An exhaust port arrangement is provided to improve air removal performance for air that may still be trapped at a location distant from either the exhaust port 13, the rod port 12, or the bottom port 11. The rod port 12 and the bottom port 11 are configured to be on the same side and end of the three-port cylinder actuator 1, and the exhaust port 13 is configured to be opposite both the rod port 12 and the bottom port 11. The exhaust port 13 is also located very close to one of the three-port cylinder actuator 1, rather than at the end. For example, the exhaust port 13 is located opposite the bottom port 11, offset in horizontal displacement by at least the width of the piston 15. The decision to locate the exhaust port 13 near the bottom port 11 or the rod port 12 can be adapted depending on the primary application of the system.

The air removal process is similar to the basic main configuration of Example 1. However, to remove air from the bottom side, it is sufficient to move the piston 15 toward the rod side by a distance approximately twice the width of the piston 15. By doing so, since the bottom port 11 and the exhaust port 13 are located very close to each other, it is expected that the air remaining on the bottom side of the three-port cylinder actuator 1 will be significantly reduced. It is also recommended that the air be removed from the rod side first, followed by the bottom side. This allows the movement of the piston 15 over a specific length to be more effectively controlled by a specific valve opening time due to the reduction in air on the rod side.

Consider a three-port cylinder actuator 1 at the remote end, connected by hoses 21 and 22 for actuation. If an exhaust valve 33 connected to exhaust port 13 is located on the human/operator end, hose 23 adds to the total number of hoses 21, 22, and 23 running along the system. Some applications require a reduction in the total number of hoses in remote applications. For example, the number of hoses required can be reduced by attaching the exhaust valve 33 directly to the three-port cylinder actuator 1 or by locating it closer to the cylinder actuator system and not near the tank 8. The exhaust valve 33 can be a solenoid-operated valve that can be controlled with thin wiring. The fluid can then be vented to the environment. This configuration reduces the total number of hoses and the total combined length of hoses and cables running along the system.

Referring to Figure 3, a hydraulic drive system according to a third embodiment of the present invention will be described.

Air removal performance can be further improved by changing the exhaust valve 33 on the exhaust port 13 to a two-way valve type, as shown in Figure 3. This configuration can be used to move fluid in a patterned movement command, such as back and forth at a predetermined time, creating a viscous force that rubs against air trapped at the end of the cylinder or hose. Frictional movement can also be combined with the movement of the piston 15 to further increase the viscous force of the fluid.

For example, to remove air from the bottom side, first move the piston 15 toward the rod. Next, set the rod-side operating valve 32 to OFF. Then, set the operating valve 31 to ON (pump) and the exhaust valve 35 to ON (tank) to allow fluid to flow from the bottom port 11 to the exhaust port 13. For a certain period of time, change the orientation of the operating valve 31 and the exhaust valve 35 to allow fluid to flow from the exhaust port 13 to the bottom port 11.

This switching control over a given period of time creates patterned fluid movement. Similarly, air can be removed from the rod side by appropriately controlling the valve.

To further improve air removal performance, it is preferable to set the piston 15 to a precise position to the right or left of the exhaust port 13. The piston position characteristic based on the valve opening time only functions when there is no load on the tip of the cylinder rod 16.

By adding a flow sensor on either the rod side or bottom side, the amount of fluid can be detected more accurately, and that information can be used to estimate the position of the piston 15. The flow sensor is not limited to traditional flow sensors, but can be any other sensor capable of measuring either the amount of fluid movement or the movement of the piston. An example of such a sensor is a linear encoder sensor placed on the piston 15, or if the piston is a separate cylinder with a linear encoder sensor attached, the amount of fluid can be calculated from the piston displacement and the cylinder diameter.

Referring to Figure 4, a hydraulic drive system according to a fourth embodiment of the present invention will be described.

Example 1 of the present disclosure (Figure 1) is applicable not only to single-cylinder actuator systems, but also to multiple-cylinder actuator systems. Figure 4 shows a configuration that enables an air removal method for multiple cylinder actuators, allowing the pistons to return to their initial positions without increasing the number of motor pumps 7. In this figure, adding a pressure sensor 53 to the output of the motor pump 7 is useful for storing the operating status of each of the different three-port cylinder actuators 1a, 1b, so that the pistons 15a, 15b can return to their initial positions after the air removal process.

During the air removal process for multiple cylinder actuators, each cylinder can assume any position relative to the others. To remove air from three-port cylinder actuator 1a, the operating valves 31b and 32b and exhaust valve 33b of three-port cylinder actuator 1b, as well as the other cylinders, are set to OFF. The bottom side pressure of three-port cylinder actuator 1a is detected by pressure sensor 51a and set to P1a, and the pressure of the motor pump 7 is set to that value. This value is saved as the pressure state of three-port cylinder actuator 1a. The position of piston 15a near rod port 12a or bottom port 11a can be detected from the value of flow sensor 41a. Once the position of piston 15a is known, the air removal process similar to that in Example 1 can be performed from that side without moving piston 15a of three-port cylinder actuator 1a.

To remove air from the opposite side, the piston 15a can be moved with minimal movement due to feedback from the flow sensor 41a, and the air removal process is similar, but using the same pressure P1a. After air removal from both sides has been performed, the three-port cylinder actuator 1a can be returned to its initial position. After the first cylinder (three-port cylinder actuator 1a) is completed, air removal from the next cylinder actuator (three-port cylinder actuator 1b) can proceed.

Referring to Figure 5, a hydraulic drive system according to a fifth embodiment of the present invention will be described.

To further improve the air removal capability with multiple cylinder actuators, a relief valve can be added to each set of cylinder actuators.

5, by adding relief valves 61a and 61b and setting the relief valve upper limit pressure equal to the pressure sensors 51a and 51b attached near the bottom ports 11a and 11b or the rod ports 12a and 12b, air removal can be performed simultaneously for all cylinder actuators. Although the process is simultaneous, it is not necessarily completed simultaneously for all cylinders because the initial state of each cylinder is different.

Referring to Figure 6, a hydraulic drive system according to a sixth embodiment of the present invention will be described.

The basic configuration is the same as in Example 1, but the cylinder actuator uses a four-port cylinder actuator 2, and the exhaust ports 13 and 14 are located anywhere between the bottom port 11 and the rod port 12. The exhaust ports 13 and 14 are controlled by exhaust valves 33 and 34, respectively. With this configuration, when the piston 15 is located anywhere between the rod port 12 and the bottom port 11, the operating valve 31 is switched to allow air to flow from the bottom port 11 to the exhaust port 13, and the operating valve 32 is switched to allow air to flow from the rod port 12 to the exhaust port 14, thereby simultaneously removing air from both the rod side and the bottom side.

As with Example 3 (Figure 3), it is also possible to use two-way valves for the exhaust valves 33 and 34.

Referring to Figure 7, a hydraulic drive system according to a seventh embodiment of the present invention will be described.

To further improve air removal capabilities, the exhaust ports 13, 14 are positioned exactly opposite the respective rod port 12 and bottom port 11. This placement is expected to allow air to travel directly to the exhaust ports 13, 14 in a straight line.

Examples 6 and 7, using the four-port cylinder actuator 2, are further improved by sequentially performing the air removal process from the bottom side or the rod side. To remove air from one side, for example the rod side, the piston 15 is first moved to a position very close to the end of the rod port 12, allowing the fluid to flow in a straight line from the rod port 12 to the exhaust port 14. After the fluid has flowed on the rod side, the same operation is performed on the bottom side by first moving the piston 15 to a position very close to the end of the bottom port 11.

One way to move the piston 15 very close to the end of the rod port 12 is to first set both exhaust valves (solenoid valves) 33, 34 to OFF, then set the actuation valve 31 to ON (pump) to connect the motor pump 7 to the bottom port 11, and set the actuation valve 32 to ON (tank) to connect the rod port 12 to the tank 8. The piston 15 will move to the end of the cylinder at the rod port 12. In this state, the fluid movement can be reversed slightly by setting the actuation valve 32 to connect the motor pump 7 to the rod port 12 and the actuation valve 31 to connect to the tank 8, for a very short period of time based on the characteristics of the cylinder's movement.

Because the exhaust valves 33 and 34 for the exhaust ports are located on the human/operator side, adding hoses 23 and 24 increases the total number of hoses 21, 22, 23 and 24. By attaching the exhaust valves 33 and 34 directly to the four-port cylinder actuator 2 and removing the air to the environment, the number of hoses required can be reduced. The exhaust valves 33 and 34 can be electromagnetic on-off valves controlled by thin wiring.

The basic configurations of Examples 6 and 7 (Figures 6 and 7) are further improved by changing the exhaust valves 33, 34 at the exhaust ports 13, 14 from one-way solenoid valves to two-way valves. Using this configuration, fluid can be moved in patterned movement commands, creating viscous forces that scrub any trapped air anywhere in the system. An example of patterned movement would be controlling the exhaust valve 33 and the actuated valve (two-way valve) 31 to flow fluid from the exhaust port 13 to the bottom port 11 for time t1, and then controlling the exhaust valve 33 and the actuated valve (two-way valve) 31 to flow fluid from the bottom port 11 to the exhaust port 13 for time t2. Here, t1 < t2, thus creating a pulsed pattern of fluid movement that results in the removal of air from the exhaust port 13 after time t3.

The process of moving the piston 15 can be improved by adding a flow sensor on either the rod or bottom side to not only control the valve in the short term, but also to more precisely adjust the piston position. If the piston 15 can be placed very close to the exhaust port 13 or 14, the fluid can be expected to move in a linear motion, preventing air from being trapped in the cylinder.

Furthermore, the air removal capability of a multi-cylinder system can be improved by adding a pressure sensor to either the rod or bottom side of the cylinder and one pressure sensor to the motor pump 7. The process of removing air and returning the piston 15 to its initial position is similar to that of Example 1, particularly when removing air from the rod and bottom sides sequentially. This configuration also allows air to be removed from both the rod and bottom sides simultaneously without moving the piston's initial position.

Referring to Figure 8, a hydraulic drive system according to Example 8 of the present invention will be described.

To reduce the total number of hoses 21, 22, 23, and 24 in the system of Example 7 (Figure 7), a single two-way exhaust valve 37 can be used to remove air from both the rod side and bottom side to the tank 8. Air is sequentially removed by setting one actuated valve (e.g., actuated valve 31) to OFF and allowing fluid to flow through the other actuated valve (e.g., actuated valve 32) and its exhaust valve 37. The piston position can be maintained during air removal by either keeping it stationary or by first stopping the piston 15 as close as possible to each exhaust port 13 and 14. In some circumstances, air and fluid can be removed to the environment instead of the tank 8.

Referring to Figure 9, a hydraulic drive system according to a ninth embodiment of the present invention will be described.

To further reduce the total number of hoses without removing air to the environment, a one-way type exhaust valve 38 can be used, with a single valve port connected to both exhaust ports 13 and 14 of the four-port cylinder actuator 2. While this configuration allows air to be removed from both sides simultaneously, it does not keep the piston 15 constant during the process. Therefore, the process of returning the piston 15 to the other side must be repeated.

An example of an air removal method is as follows: First, move the piston 15 to the end of the cylinder at the bottom port 11. Next, by setting the exhaust valve 38 ON, the operating valve 31 ON (pump), and the operating valve 32 ON (tank), fluid moves from the bottom port 11 to the exhaust port 13 and from the exhaust port 14 to the rod port 12. Air on both sides is removed simultaneously with fewer exhaust valve components. However, due to the pressure difference, the piston 15 is expected to move slowly to the end of the cylinder at the rod port 12. Therefore, after the piston 15 reaches the rod port 12, the exhaust valve 38 is set OFF, and the piston 15 returns to the bottom port 11 in the normal manner. The air removal process can then be repeated.

This configuration can also be used to remove air from multiple cylinder actuator systems by increasing the set of components from the cylinder actuator to its operating valve control device. The process is similar, with each cylinder actuator being bled sequentially.

This configuration can be further improved by adding flow sensors on both the rod and bottom sides. The piston 15 is initially set at the end of the cylinder at the bottom port 11. Then, by setting the actuation valve 31 ON (pump), the actuation valve 32 ON (tank), and the exhaust valve 38 ON, fluid flows from the bottom port 11 to the exhaust port 13 and from the exhaust port 14 to the rod port 12. In this case, the piston 15 moves along with it to the rod side. After the piston 15 reaches the end of the cylinder at the rod port 12, the fluid volume is stored from the data of the flow sensor 41. The piston 15 returns to the other end of the cylinder at the bottom port 11 by switching the exhaust valve 38 OFF, while simultaneously storing the fluid volume from the flow sensor 42. The difference in volume data determines the number of times the process is repeated until the air is completely removed from the tank 8.

This configuration allows for both sequential and simultaneous air removal. For example, in a simultaneous process, the pistons of all cylinders are first moved to the bottom side, and then the air removal process is performed. Because the initial cylinder position and rod load differ for each cylinder, the timing at which each piston reaches the rod side differs. The timing at which the piston reaches the rod side is monitored by each pair of flow sensors 41, 42 in each cylinder set. If the flow sensor data indicates that the piston 15 has reached the rod side, its respective actuating valve 31, 32 is controlled to return the piston 15 to the bottom side, while the other actuating valve of the other cylinder continues to move normally. This configuration allows air to be removed simultaneously even if the piston movement is not always the same for each cylinder.

Referring to Figure 10, a hydraulic drive system according to a tenth embodiment of the present invention will be described.

Generally, the tubes (hoses) used in the system are made of rubber material, which allows the interior to expand at a certain rate when pressure is applied. This internal hose expansion can lead to inaccurate generation and estimation of small fluid movements. The discrepancy in small measurements will be further increased by differences in hydraulic pressure caused by the position of the cylinder within the system and the different areas of the plates of the piston 15 on both sides at the same pressure magnitude applied by the motor pump 7. To improve accuracy, it is necessary to add a flow sensor 42 and a pressure sensor 52 on the rod side, as well as relief valves 61 and 62, all controlled by the control device 109, which can separately adjust the pressure on the rod side and bottom side.

In this embodiment, the air removal process utilizes internal tube expansion. To remove air from the rod side, the piston 15 is first moved to the end of the four-port cylinder actuator 2 at the rod port 12. After the piston 15 has completely stopped and there is no pressure change on the bottom side, the fluid pressure P1 is stored from the data of the pressure sensor 51. Then, the operating valve 31 and exhaust valve 35 are set to OFF to eliminate fluid movement on the bottom side. The weight of the load connected to the cylinder rod 16 then pushes the piston 15 to the bottom side, causing the internal hoses (bottom hose 21 and exhaust hose 23) to expand until they reach equilibrium at pressure P1'. Next, the relief valve 61 is adjusted to adjust the pressure at P1', and the piston moves again until it reaches the end of the cylinder at the rod port 12.

Second, by setting the limit pressure of the relief valve 62 to P1', the piston 15 moves with a small amount of fluid displacement. Instead of turning the actuation valve 31 and exhaust valve 35 to the OFF position, the actuation valve 31 and exhaust valve 35 can be set to ON to keep the bottom side pressure constant at P1' without internal expansion of the hose. The rod side pressure is gradually increased by controlling the limit of the relief valve 62 until the flow sensor 42 begins to move. This pressure is monitored by the pressure sensor 52 and stored as P2.

Finally, after the air on the rod side has been removed, the bottom side pressure is lowered below P1' to remove the air on the bottom side. After the piston 15 reaches the end of the cylinder at the bottom port 11, a small amount of fluid is replaced by gradually increasing the pressure limit of the relief valve 61 above P1'. After the flow sensor 41 detects the movement of fluid, the process is complete. These processes allow for a more accurate air removal method to be performed even with random attitudes of the cylinder system.

Referring to Figure 11, a hydraulic drive system according to an eleventh embodiment of the present invention will be described.

By utilizing relief valves on both sides, the air removal capability on both sides can be further improved without changing the position of the piston 15. This process can be considered as follows: When the piston 15a is stopped by setting all valves to OFF, the pressure data detected on either the rod side 52a or the bottom side 51a contains the expansion state of the tube (hose). Data from the flow sensors 41a and 42a on both sides also determine the initial position of the piston, and the difference between them is set, for example, as a constant parameter Qd. Because these pressures are necessary to maintain the piston stability, the relief valves 61 and 62 are set according to the pressure limits obtained from the pressure sensors 51a and 52a. Then, valves 31a and 32a are set to ON (pump) and valves 35a and 36a are set to ON (tank), allowing fluid to flow from the bottom port 11a to the exhaust port 13a and from the rod port 12a to the exhaust port 14a. During this air removal process, the total fluid flowing from the bottom side minus the total fluid flowing from the rod side is maintained constant as Qd by adjusting the pressure limits of the relief valves 61 and 62 to prevent piston 15a from moving.

Finally, this embodiment can also be used in multiple cylinder actuator systems. By having each cylinder have the same components, from pressure sensors to flow sensors, valves, and relief valves, air can be removed from all cylinders simultaneously. Furthermore, as shown in Figure 11, it is possible to use only two relief valves 61 and 62 for all cylinder actuators by performing the air removal sequentially.

The present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

1, 1a, 1b: 3-port cylinder actuator 2, 2a, 2b: 4-port cylinder actuator 7: Motor pump 8: Tank 11, 11a, 11b: Bottom port 12, 12a, 12b: Rod port 13, 13a, 13b, 14, 14a, 14b: Exhaust port 15, 15a, 15b: Piston 16, 16a, 16b: Cylinder rod 21: Bottom hose 22: Rod hose 23, 24, 25: Exhaust hose 31, 31a, 31b, 32, 32a, 32b: Actuating valve (two-way valve)
33, 33a, 33b, 34, 35, 35a, 35b, 36, 36a, 36b, 37, 38: Exhaust valves 41, 41a, 41b, 42, 42a, 42b: Flow rate sensors 51, 51a, 51b, 52, 52a, 52b, 53: Pressure sensors 61, 61a, 61b, 62: Relief valves 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110: Control device 200: Air or foreign matter

Claims (21)

a three-port cylinder actuator having a piston;
at least two actuated valves including a first actuated valve and a second actuated valve;
An exhaust valve;
a tank for storing a fluid;
a motor pump for supplying the fluid from the tank to the actuation valve;
a control device for controlling all of the operating valves and the exhaust valves and the motor pump;
A hydraulic drive system comprising:
the first operating valve is connected to a bottom port of the three-port cylinder actuator, the second operating valve is connected to a rod port of the three-port cylinder actuator, and the exhaust valve is connected to an exhaust port of the three-port cylinder actuator;
the rod port and the bottom port are located at each end of the three-port cylinder actuator, and the exhaust port is located anywhere between the rod port and the bottom port;
removing air from the bottom side of the three-port cylinder actuator by controlling the piston to move to the rod side of the three-port cylinder actuator, setting the second operating valve of the rod port to OFF, setting the exhaust valve of the exhaust port to ON to open it, and setting the first operating valve of the bottom port to ON, and allowing air to flow to the tank;
a hydraulic drive system for removing air from a rod side of the three-port cylinder actuator by controlling the piston to move to the bottom side of the three-port cylinder actuator, setting the first operating valve of the bottom port to OFF, setting the exhaust valve of the exhaust port to ON to open it, setting the second operating valve of the rod port to ON, and allowing air to flow to the tank. 2. The hydraulic drive system of claim 1,
A hydraulic drive system wherein the exhaust port is located opposite both the rod port and the bottom port and is horizontally offset from either the rod port or the bottom port by at least the width of the piston. 2. The hydraulic drive system of claim 1,
A hydraulic drive system in which the exhaust valve is attached to the three-port cylinder actuator. 2. The hydraulic drive system of claim 1,
A hydraulically actuated system wherein the exhaust valve is a one-way valve. 2. The hydraulic drive system of claim 1,
the exhaust valve is a two-way valve;
removing air from the bottom side of the three-port cylinder actuator by controlling the piston to move to the rod side, setting the second actuation valve of the rod port to OFF, simultaneously setting the exhaust valve and the first actuation valve of the bottom port to ON to allow the fluid to flow from the bottom port to the exhaust port, switching the direction of the fluid from the exhaust port to the bottom port in a shorter time than the previous direction, and repeating the above process until all the air is purged from the bottom side;
a hydraulic drive system for removing air from the rod side of the three-port cylinder actuator by controlling the piston to move to the bottom side, setting the first actuation valve of the bottom port to OFF, simultaneously setting the exhaust valve and the second actuation valve of the rod port to ON to flow the fluid from the rod port to the exhaust port, switching the direction of the fluid from the exhaust port to the rod port in a shorter time than the previous direction, and repeating the above process until all the air is purged from the rod side. 2. The hydraulic drive system of claim 1,
The hydraulic drive system further includes a flow sensor for detecting the flow or volume of said fluid on either said rod side or said bottom side. 7. The hydraulic drive system according to claim 6,
a first pressure sensor for detecting pressure on either the rod side or the bottom side;
a second pressure sensor that detects the pressure on the motor pump side;
Further comprising at least two sets of a three-port cylinder actuator, an actuation valve, an exhaust valve, a flow sensor, and a pressure sensor;
the configurations of the three-port cylinder actuator, the operating valve, the exhaust valve, the flow sensor, and the pressure sensor in the first set are the same as those in the second set;
reading the initial pressure state and piston position of the cylinder by the pressure sensor and the flow sensor, moving the piston to a position close to the exhaust port, removing air on either the rod side or the bottom side, moving the piston by a short movement to the opposite side, removing air on the other side, setting all operating valves to OFF, controlling the pressure of the motor pump to the initially stored pressure state by feedback from the pressure sensor on the motor pump side, and opening the operating valves so that the piston returns to the initial position stored by the pressure sensor and flow sensor on the rod side or the bottom side, thereby removing the air in the first cylinder;
A hydraulic drive system that removes air in the second cylinder in a similar process to the first cylinder by controlling and reading the sensor status of each component. 7. The hydraulic drive system according to claim 6,
a first pressure sensor for detecting pressure on either the rod side or the bottom side;
A relief valve on the motor pump side;
Further including at least two sets of a three-port cylinder actuator, an operating valve, an exhaust valve, a relief valve, a flow sensor, and a pressure sensor;
the configurations of the three-port cylinder actuator, the operating valve, the exhaust valve, the relief valve, the flow sensor, and the pressure sensor in the first set are the same as those in the second set;
A hydraulic drive system that simultaneously removes air on both sides of all three-port cylinder actuators by setting each relief valve upper limit pressure to pressure sensor data from each of the rod ports or bottom ports of the three-port cylinder actuators. a four-port cylinder actuator having a piston;
at least two actuated valves including a first actuated valve and a second actuated valve;
two exhaust valves including a first exhaust valve and a second exhaust valve;
a tank for storing a fluid;
a motor pump for supplying the fluid from the tank to the actuation valve;
a control device for controlling all of the operating valves and the exhaust valves and the motor pump;
A hydraulic drive system comprising:
the first operating valve is connected to a bottom port of the four-port cylinder actuator, the second operating valve is connected to a rod port of the four-port cylinder actuator, the first exhaust valve is connected to a first exhaust port of the four-port cylinder actuator, and the second exhaust valve is connected to a second exhaust port of the four-port cylinder actuator;
the rod port and the bottom port are located at each end of the four-port cylinder actuator, and the first exhaust port and the second exhaust port are located anywhere between the rod port and the bottom port;
A hydraulically driven system that removes air from both the bottom side and the rod side by setting the actuation valve and the exhaust valve to ON and forcing air from the bottom port and the rod port to the respective exhaust ports. 10. The hydraulic drive system of claim 9,
A hydraulically driven system in which each exhaust port is located exactly opposite the respective rod port or bottom port. 10. The hydraulic drive system of claim 9,
A hydraulic drive system in which the exhaust valve is attached to the four-port cylinder actuator. 10. The hydraulic drive system of claim 9,
A hydraulically actuated system wherein each of said exhaust valves is a one-way valve. 10. The hydraulic drive system of claim 9,
One two-way valve is used as two exhaust valves,
a first exhaust port of the four-port cylinder actuator connected to a first port of the two-way valve, a second exhaust port of the four-port cylinder actuator connected to a second port of the two-way valve, and a third port of the two-way valve connected to the tank. 10. The hydraulic drive system of claim 9,
One one-way valve is used as two exhaust valves,
A hydraulic drive system, wherein a first exhaust port of the four-port cylinder actuator is connected to a first port of the one-way valve, and a second exhaust port of the four-port cylinder actuator is connected to a second port of the one-way valve. 10. The hydraulic drive system of claim 9,
Each of the two exhaust valves is a two-way valve;
setting the operating valve and the exhaust valve to ON and removing air from both the bottom side and the rod side by flowing air from the bottom port and the rod port to each exhaust port;
switching the direction of the fluid from the exhaust port to each of the bottom port and the rod port in a shorter time than in the previous direction;
The hydraulic drive system repeats the above process until air is evacuated from both the bottom side and the rod side. 10. The hydraulic drive system of claim 9,
The hydraulic drive system further includes a flow sensor for detecting the flow or volume of said fluid on either said rod side or said bottom side. 15. The hydraulic drive system of claim 14,
The hydraulic drive system further includes flow sensors for detecting the flow or volume of said fluid on both said rod side and said bottom side. 18. The hydraulic drive system of claim 17,
Further including at least two sets of a four-port cylinder actuator, an actuation valve, an exhaust valve, and a flow sensor;
The configuration of the first set of the four-port cylinder actuator, the operating valve, the exhaust valve, and the flow sensor is the same as the configuration of the second set;
The air on both sides of all four-port cylinder actuators is first removed by controlling all pistons to be as close as possible to the bottom port,
setting the exhaust valve to ON to open and connect both exhaust ports, and controlling the operating valve to flow the fluid from the bottom port to the rod port while detecting the position of the piston from each flow sensor;
closing each exhaust valve to return the piston to a position near the bottom end;
A hydraulically driven system that repeats the above process until the fluid moving from the bottom port to the rod port meets a calculated fixed amount to remove air from the system. 17. The hydraulic drive system of claim 16,
a first pressure sensor for detecting pressure on either the rod side or the bottom side;
a second pressure sensor that detects the pressure on the motor pump side;
Further including at least two sets of a four-port cylinder actuator, an actuation valve, an exhaust valve, a flow sensor, and a pressure sensor;
the first set of the four-port cylinder actuator, the operating valve, the exhaust valve, the flow sensor, and the pressure sensor have the same configuration as the second set;
reading the initial pressure state and piston position of the cylinder by the pressure sensor and the flow sensor, removing the air on either the rod side or the bottom side, setting all operating valves to OFF, controlling the pressure of the motor pump to the initially stored pressure state by feedback from the pressure sensor on the motor pump side, and opening the operating valves to return the piston to the initial position stored by the pressure sensor and flow sensor on the rod side or the bottom side, thereby removing the air in the first cylinder;
A hydraulic drive system that removes air in the second cylinder in a similar process to the first cylinder by controlling and reading the sensor status of each component. 17. The hydraulic drive system of claim 16,
flow sensors on both the rod side and the bottom side;
pressure sensors on both the rod side and the bottom side;
two relief valves connected to the rod side and the bottom side, respectively;
The exhaust port is connected to a two-way valve in a hydraulically actuated system. 21. The hydraulic drive system of claim 20,
Further including at least two sets of a four-port cylinder actuator, an actuation valve, an exhaust valve, a flow sensor, and a pressure sensor;
the first set of the four-port cylinder actuator, the operating valve, the exhaust valve, the flow sensor, and the pressure sensor have the same configuration as the second set;
A hydraulic drive system in which a first relief valve is connected to the bottom side of every four-port cylinder actuator and a second relief valve is connected to the rod side of every four-port cylinder actuator.