hydrostatic transmission

Abstract

Provided is a small and low-cost hydraulic transmission.　When a fluid pressure is applied to a left driving pressure chamber 36, an internal piston 31 moves right, an operational fluid L2 in a right pressure chamber 35 is pushed out to a left pressure chamber 44 of a hydraulic actuator 4 at high pressure by the area ratio of the piston 31 and a rod 33, and an operational fluid L5 is returned from a right pressure chamber 45 to a left pressure chamber 34 of the hydraulic actuator 4. The reverse is the same. Accordingly, even without preparing conventional first and second empty liquid converters, it is possible to drive the hydraulic actuator 4 at high pressure, and thus the present invention is suitable for a high-load hydraulic robot. In addition, by solely measuring the position of the piston 31 and the pressures of the left and right pressure chambers with sensors, the position and force of the actuator can be remotely controlled without any additional sensors attached to the actuator placed in a remote unit.

Description

[Technical Field]

[0001] The present invention relates to a hydraulic transmission that drives a hydraulic actuator. [Background technology]

[0002] As a hydraulic drive method using tap water or the like as the hydraulic fluid, for example, a hydrostatic transmission consisting of a pair of master and slave cylinders is known, as described in Non-Patent Documents 1 and 2. Using tap water makes it possible to realize a completely harmless remote-controlled robot. When using this in an automatically controlled hydraulic drive robot, the issue becomes how to configure the master cylinder. [Prior art documents] [Patent documents]

[0003] [Non-Patent Document 1] G. Ganesh, R. Gassert, E. Burdet, and H. Bleuler, “Dynamics and control of an MRI compatible master-slave system with hydrostatic transmission,” IEEE International Conference on Robotics and Automation, 2004, pp. 1288-1294. [Non-patent document 2] JP Whitney, MF Glisson, EL Brockmeyer, and JK Hodgins, “A low-friction passive fluid transmission and fluid-tendon soft actuator,” IEEE / RSJ International Conference on Intelligent Robots and Systems, 2014, pp. 2801-2808. [Patent Document 1] International Publication No. 2021 / 070828 Summary of the Invention [Problem to be solved by the invention]

[0004] Non-Patent Documents 1 and 2 use an electric actuator as a master cylinder, but electric actuators capable of generating a large force sufficient for use in robots and the like are expensive. Patent Document 1, on the other hand, discloses a method for obtaining high hydraulic pressure by configuring a master cylinder with an air-hydraulic intensifier. The hydraulic drive system described in Patent Document 1 includes first and second air-hydraulic intensifiers that convert air pressure supplied from an air pressure source into hydraulic pressure, a hydraulic actuator having first and second pressure chambers, an operating status acquisition unit that acquires the operating status of the hydraulic actuator, and first and second air pressure valves provided in first and second air supply passages that supply air from the air pressure source to the first and second air-hydraulic intensifiers, respectively. The control device controls the first and second air pressure valves based on the results acquired by the operating status acquisition unit. However, the use of two air-hydraulic intensifiers and two air pressure servo valves not only increases the size of the drive system but also increases costs.

[0005] In view of the above problems, the present invention aims to provide a hydraulic transmission that is smaller and less expensive than conventional transmissions and that can easily control various high-load hydraulic actuators, such as water hydraulic actuators. [Means for solving the problem]

[0006] The above object of the present invention can be achieved by the following means: Note that the parentheses indicate reference symbols of embodiments to be described later, but the present invention is not limited to these.

[0007] The hydraulic transmission according to claim 1 comprises a drive means (drive unit 3) driven by fluid pressure (for example, air pressure or hydraulic pressure); a hydraulic actuator (4) driven by pressure fluid supplied from the driving means (driving unit 3); supply paths (first supply path 13, second supply path 14) connected to the hydraulic actuator (4) and the drive means (drive unit 3); A predetermined mechanism (e.g., a pump 15, a tank T) provided in the supply path (first supply path 13, second supply path 14), and The driving means (3) A hollow cylinder chamber (30), a piston (31) provided reciprocally within the cylinder chamber (30); and rods (left rod 32, right rod 33) provided on the piston (31), The rod (left rod 32) has one end (left end 32a) filled with a liquid (hydraulic liquid L1). in advance a first pressure chamber (left pressure chamber 34) in which the pressure is sealed; The other end (right end 33a) of the rod (right rod 33) is filled with a liquid (working liquid L2). in advance a second pressure chamber (right pressure chamber 35) in which the pressure is sealed; The piston (31) divides the cylinder chamber (30) into a first drive pressure chamber (left drive pressure chamber 36) and a second drive pressure chamber (right drive pressure chamber 37), the area of the ends (left end 31a, right end 31b) of the piston (31) is larger than the area of the ends (left end 32a, right end 33a) of the rods (left rod 32, right rod 33); When the fluid pressure is supplied to the first driving pressure chamber (left driving pressure chamber 36), the piston (piston 31) moves, and the liquid (working liquid L2) in the first pressure chamber (right pressure chamber 35) is pushed out, so that the liquid (working liquid L2) is supplied to the hydraulic actuator (4). Through the supply path (second supply path 14) Further, the hydraulic actuator (4) supplies the liquid (operating liquid L5) to the second pressure chamber (left pressure chamber 34). Through the supply path (second supply path 14) It was returned, When the fluid pressure is supplied to the second driving pressure chamber (right driving pressure chamber 37), the piston (31) moves, and the liquid (working liquid L1) in the second pressure chamber (left pressure chamber 34) is pushed out, so that the liquid (working liquid L1) is supplied to the hydraulic actuator (4). Through the supply path (first supply path 13) Further, the hydraulic actuator (4) supplies the liquid (operating liquid L4) to the first pressure chamber (right pressure chamber 35). Through the supply path (first supply path 13) It's been returned the law of nature, The predetermined mechanism (e.g., pump 15, tank T) By applying a constant pressure to the supply paths (first supply path 13, second supply path 14) so that the liquids (hydraulic liquids L1, L2) do not become negative pressure, the preload can be adjusted according to the state of the hydraulic actuator (4). The liquid can be supplied to compensate for the amount of external leakage of the liquid (hydraulic liquid L1) previously sealed in the first pressure chamber (left pressure chamber 34) and / or the liquid (hydraulic liquid L2) previously sealed in the second pressure chamber (right pressure chamber 35), or the amount of internal leakage between the liquid (hydraulic liquid L1) previously sealed in the first pressure chamber (left pressure chamber 34) and the liquid (hydraulic liquid L2) previously sealed in the second pressure chamber (right pressure chamber 35). It is characterized by the following.

[0009] Claim 2 The hydraulic transmission according to the claim 1 In the hydraulic transmission (1B) described in The above The supply paths (first supply path 13, second supply path 14) are characterized in that a hydraulic cylinder (4B) or a rotary pump is provided in each of the supply paths. [Effects of the Invention]

[0010] Next, the effects of the present invention will be described with reference to the drawings. Note that the reference symbols in parentheses are those of the embodiments described below, but the present invention is not limited to these.

[0011] According to the invention of claim 1, the hydraulic actuator (4) can be driven simply by driving the drive means (drive unit 3) using fluid pressure (e.g., air pressure or hydraulic pressure). Furthermore, the hydraulic actuator (4) can be driven by the drive means (drive unit 3) alone, without the need for first and second air-liquid converters as in the prior art. Furthermore, by making the area of the ends (left end 31a, right end 31b) of the piston (31) larger than the area of the ends (left end 32a, right end 33a) of the rods (left rod 32, right rod 33), the pressure of the liquid (working fluids L1, L2) supplied to the hydraulic actuator (4) can be increased. As a result, according to the present invention, it is possible to easily control various high-load hydraulic actuators and, further, to make them smaller and less expensive than conventional hydraulic actuators.

[0012] Furthermore, request 1 According to the invention, The supply paths (first supply path 13, second supply path 14) are provided with predetermined mechanisms (e.g., pump 15, tank T). The predetermined mechanisms (e.g., pump 15, tank T) apply a constant pressure to the supply paths (first supply path 13, second supply path 14) so that the liquid (working liquids L1, L2) does not become negative pressure, thereby adjusting the preload in accordance with the state of the hydraulic actuator (4). Furthermore, the predetermined mechanisms can supply liquid to compensate for the amount of external leakage of the liquid (working liquid L1) previously sealed in the first pressure chamber (left pressure chamber 34) and / or the liquid (working liquid L2) previously sealed in the second pressure chamber (right pressure chamber 35), or the amount of internal leakage between the liquid (working liquid L1) previously sealed in the first pressure chamber (left pressure chamber 34) and the liquid (working liquid L2) previously sealed in the second pressure chamber (right pressure chamber 35).

[0013] Claim 2 According to the invention , supplyThe supply paths (first supply path 13, second supply path 14) are provided with hydraulic cylinders 4B or rotary pumps, which facilitates precise control of the hydraulic actuators 4. Furthermore, by operating the hydraulic cylinders 4B or rotary pumps with another actuator or by human power, bilateral control or power assist control can be realized. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram of a hydraulic transmission according to an embodiment of the present invention; [Figure 2] FIG. 4 is a schematic diagram of a hydraulic transmission according to another embodiment of the present invention. [Figure 3] FIG. 4 is a schematic diagram of a hydraulic transmission according to another embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram of a hydraulic transmission according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of a hydraulic transmission according to the present invention will be described in detail with reference to the drawings. In the following description, up, down, left, and right directions refer to up, down, left, and right directions when viewed from the front of the illustration.

[0016] The hydraulic transmission of this embodiment is used for underwater work in fisheries, ports, rivers, dams, etc., high-pressure washing, sewage treatment, pharmaceuticals, cosmetics, food processing, sinks in restaurants, markets, toilets, hospitals, nursing homes, agriculture, forestry, livestock farming, power generation facilities, firefighting equipment, etc. Specifically, as shown in Figure 1, the hydraulic transmission 1 is mainly composed of a servo valve 2, a drive unit 3, and a hydraulic actuator 4. Each component will be described in detail below.

[0017] <Servo valve explanation> As shown in FIG. 1, the servo valve 2 is a three-position, five-port servo valve, with the supply port 2a connected to an air pressure source 10 such as a compressor that supplies air pressure, the control port 2b connected to a first control path 11, the control port 2c connected to a second control path 12, and the discharge ports 2d and 2e connected to the outside.

[0018] Although not shown in detail, the servo valve 2 is equipped with a spool driven by a solenoid, and the supply and cut-off of air pressure can be changed responsively and steplessly depending on the position of the spool. That is, when the spool is positioned on the left side as shown in Figure 1, the supply port 2a is connected to the first control path 11, and the discharge port 2e is connected to the second control path 12. As a result, air pressure supplied from the air pressure source 10 is supplied to the first control path 11.

[0019] 1, the supply port 2a is connected to the second control path 12, and the discharge port 2d is connected to the first control path 11. As a result, the air pressure supplied from the air pressure source 10 is supplied to the second control path 12.

[0020] Furthermore, when the spool is positioned in the center as shown in Figure 1, the supply port 2a is blocked so as not to communicate with the first control path 11 or the second control path 12. As a result, the air pressure supplied from the air pressure source 10 is not supplied to either the first control path 11 or the second control path 12. It is known that such a servo valve 2 can be incorporated into a feedback control system to control the position and force of a hydraulic actuator with good responsiveness.

[0021] <Explanation of the drive unit> As shown in FIG. 1, the drive unit 3 includes a hollow cylinder chamber 30, a piston 31 reciprocally disposed within the cylinder chamber 30, a left rod 32 disposed at a left end 31a of the piston 31, and a right rod 33 disposed at a right end 31b of the piston 31. As shown in FIG. 1, a left pressure chamber 34 is provided on the left end 32a side of the left rod 32, within which the left rod 32 can freely move. A hydraulic fluid L1, such as water, is sealed in the left pressure chamber 34. As shown in FIG. 1, a right pressure chamber 35 is provided on the right end 33a side of the right rod 33, within which the right rod 33 can freely move. A hydraulic fluid L2, such as water, is sealed in the right pressure chamber 35. As shown in FIG. 1, a first supply path 13 connected to the hydraulic actuator 4 is connected to the left pressure chamber 34, and a second supply path 14 connected to the hydraulic actuator 4 is connected to the right pressure chamber 35.

[0022] 1, the inside of the cylinder chamber 30 is divided by the piston 31 into a left driving pressure chamber 36 and a right driving pressure chamber 37, with the left driving pressure chamber 36 connected to the first control path 11 and the right driving pressure chamber 37 connected to the second control path 12. The left driving pressure chamber 36 and the right driving pressure chamber 37 are filled with air, with a left rod 32 disposed and fixed in the left driving pressure chamber 36 as shown in FIG. 1, and a right rod 33 disposed and fixed in the right driving pressure chamber 37 as shown in FIG.

[0023] Thus, in the drive unit 3, when air pressure is supplied to the first control path 11, the piston 31 moves to the right as shown in FIG. 1, and accordingly, the right rod 33 moves to the right as shown in FIG. 1. As a result, the right rod 33 enters the right pressure chamber 35, thereby pushing out the hydraulic fluid L2 sealed in the right pressure chamber 35, and the hydraulic fluid L2 is supplied to the hydraulic actuator 4 through the second supply path 14. Note that as the piston 31 moves to the right as shown in FIG. 1, a portion of the air that had filled the right drive pressure chamber 37 is discharged into the second control path 12. As a result, the air passes through the second control path 12 and is discharged to the outside from the discharge port 2e.

[0024] Furthermore, when air pressure is supplied to the second control path 12, the piston 31 moves leftward as shown in FIG. 1, and accordingly, the left rod 32 moves leftward as shown in FIG. 1. As a result, the left rod 32 enters the left pressure chamber 34, which pushes out the hydraulic fluid L1 sealed in the left pressure chamber 34 and supplies it to the hydraulic actuator 4 through the first supply path 13. Note that as the piston 31 moves leftward as shown in FIG. 1, some of the air that had filled the left drive pressure chamber 36 is discharged into the first control path 11. As a result, the air passes through the first control path 11 and is discharged to the outside from the discharge port 2d.

[0025] When the hydraulic fluids L1 and L2 are supplied to the hydraulic actuator 4, the hydraulic fluid L1 is compressed by the left rod 32, and the hydraulic fluid L2 is compressed by the right rod 33, thereby increasing the pressure and supplying them as pressurized fluid.

[0026] That is, the static pressure relation equation when the piston 31 tries to move in the right direction shown in Figure 1 is expressed as area of the right end 31b of the piston 31 x (pressure in the first control path 11 - pressure in the second control path 12) = area of the right end 33a of the right rod 33 x (pressure in the second supply path 14 - pressure in the first supply path 13).

[0027] Furthermore, the static pressure relationship equation when the piston 31 tries to move in the left direction shown in Figure 1 is expressed as area of the left end 31a of the piston 31 x (pressure in the second control path 12 - pressure in the first control path 11) = area of the left end 32a of the left rod 32 x (pressure in the first supply path 13 - pressure in the second supply path 14).

[0028] Therefore, from the above, the pressure increase ratio of the hydraulic fluid L1 is expressed by the area of the left end 31a of the piston 31 / the area of the left end 32a of the left rod 32, and the pressure increase ratio of the hydraulic fluid L2 is expressed by the area of the right end 31b of the piston 31 / the area of the right end 33a of the right rod 33. Therefore, the pressures of the hydraulic fluids L1 and L2 will not be increased unless the following relationships are satisfied: area of the left end 31a of the piston 31 > area of the left end 32a of the left rod 32, and area of the right end 31b of the piston 31 > area of the right end 33a of the right rod 33. Therefore, to increase the pressures of the hydraulic fluids L1 and L2, it is only necessary to satisfy the relationships: area of the left end 31a of the piston 31 > area of the left end 32a of the left rod 32, and area of the right end 31b of the piston 31 > area of the right end 33a of the right rod 33. Therefore, the pressures of the hydraulic fluids L1 and L2 can be increased simply and easily according to the application of the hydraulic actuator 4.

[0029] On the other hand, as shown in FIG. 1, as a mechanism for adjusting the preload, hydraulic fluid L3, such as water stored in a tank T, is discharged at a constant pressure (for example, pressure P0) by a pump 15. The hydraulic fluid L3 is then supplied to the first supply path 13 via a check valve 16 and to the second supply path 14 via a check valve 17. This prevents the hydraulic fluids L1 and L2 from becoming negative pressure. That is, when the right rod 33 enters the right pressure chamber 35 and the hydraulic fluid L2 sealed in the right pressure chamber 35 is supplied to the hydraulic actuator 4 through the second supply path 14, the hydraulic fluid L1 in the left pressure chamber 34 is pulled by a vacuum effect, which tends to cause the hydraulic fluid L1 to become negative pressure. Also, when the left rod 32 enters the left pressure chamber 34 and the hydraulic fluid L1 sealed in the left pressure chamber 34 is supplied to the hydraulic actuator 4 through the first supply path 13, the hydraulic fluid L2 in the right pressure chamber 35 is pulled by a vacuum effect, which tends to cause the hydraulic fluid L2 to become negative pressure. If negative pressure were to occur, the hydraulic fluids L1 and L2 would suck in external air, causing cavitation, which could result in malfunction.

[0030] Therefore, in this embodiment, a constant pressure (e.g., pressure P0) is applied to the first supply path 13 and the second supply path 14 as a preload. As a result, the pressure of the working fluid L1 flowing through the first supply path 13 fluctuates up and down based on this constant pressure (e.g., pressure P0), and the pressure of the working fluid L2 flowing through the second supply path 14 fluctuates up and down. Therefore, by applying this constant pressure (e.g., pressure P0), it is possible to prevent the working fluids L1 and L2 from becoming negative pressure. In this way, the preload can be easily adjusted, and therefore it is possible to prevent the working fluids L1 and L2 from becoming negative pressure. The check valve 16 prevents the working fluid L1 flowing through the first supply path 13 from flowing toward the pump 15, and the check valve 17 prevents the working fluid L2 flowing through the second supply path 14 from flowing toward the pump 15.

[0031] <Explanation of hydraulic actuator> As shown in FIG. 1, the hydraulic actuator 4 has a hollow cylinder chamber 40, a piston 41 reciprocally disposed within the cylinder chamber 40, a left rod 42 disposed at a left end 41a of the piston 41, and a right rod 43 disposed at a right end 41b of the piston 41. As shown in FIG. 1, the interior of the cylinder chamber 40 is divided by the piston 41 into a left pressure chamber 44 and a right pressure chamber 45. The left pressure chamber 44 is connected to a second supply path 14, and the right pressure chamber 45 is connected to a first supply path 13. The left pressure chamber 44 is filled with a hydraulic fluid L4, such as water, and the right pressure chamber 45 is filled with a hydraulic fluid L5, such as water. The left rod 42 is disposed and fixed in the left pressure chamber 44, as shown in FIG. 1, and the right rod 43 is disposed and fixed in the right pressure chamber 45, as shown in FIG. 1.

[0032] Thus, in this hydraulic actuator 4, when hydraulic fluid L2 is supplied to the left pressure chamber 44 from the second supply path 14, the amount of hydraulic fluid L4 sealed in the left pressure chamber 44 increases. This causes the piston 41 to move rightward in FIG. 1 by that amount, and therefore the right rod 43 and the left rod 42 move rightward in FIG. 1. At this time, hydraulic fluid L5 sealed in the right pressure chamber 45 is discharged into the first supply path 13 by the amount of rightward movement of the piston 41, and therefore hydraulic fluid L5 passes through the first supply path 13 and is supplied to the left pressure chamber 34. Note that the check valve 16 prevents hydraulic fluid L5 passing through the first supply path 13 from flowing toward the pump 15.

[0033] On the other hand, when the hydraulic fluid L1 is supplied to the right pressure chamber 45 from the first supply path 13, the amount of hydraulic fluid L5 sealed in the right pressure chamber 45 increases. This causes the piston 41 to move leftward in FIG. 1 by that amount, and therefore the right rod 43 and the left rod 42 move leftward in FIG. 1. At this time, the hydraulic fluid L4 sealed in the left pressure chamber 44 is discharged into the second supply path 14 by the amount of leftward movement of the piston 41, and therefore the hydraulic fluid L4 passes through the second supply path 14 and is supplied to the right pressure chamber 35. Note that the check valve 17 prevents the hydraulic fluid L4 passing through the second supply path 14 from flowing toward the pump 15.

[0034] In the hydraulic transmission 1 configured as described above, as shown in Fig. 1, a first pressure sensor P1 for detecting the pressure of the air flowing through the first control path 11 is connected to the first control path 11, and a second pressure sensor P2 for detecting the pressure of the air flowing through the second control path 12 is connected to the second control path 12. In addition, as shown in Fig. 1, a fourth pressure sensor P b is connected to the second supply passage 14, and a third pressure sensor P a1, a fifth pressure sensor P0 that detects the pressure of the discharged hydraulic fluid L3 is connected to the discharge side of the pump 15. Meanwhile, as shown in FIG. 1, the hydraulic actuator 4 is provided with a position detection sensor 18 that detects the position of the piston 41.

[0035] <Explanation of hydraulic transmission operation> Thus, the hydraulic transmission 1 configured as above is used as follows.

[0036] For example, as shown in FIG. 1, when a load N is connected to the right rod 43 of the hydraulic actuator 4 and it is desired to move the load N to the right, the following operation is performed.

[0037] That is, first, the servo valve 2 is controlled to connect the supply port 2a to the first control path 11, and air pressure is supplied to the first control path 11 from the air pressure source 10. This causes the piston 31 to move rightward as shown in FIG. 1, and the right rod 33 also moves rightward as shown in FIG. 1. This causes the right rod 33 to enter the right pressure chamber 35, thereby pushing out the hydraulic fluid L2 sealed in the right pressure chamber 35 and supplying it to the left pressure chamber 44 through the second supply path 14. When the hydraulic fluid L2 is then supplied to the left pressure chamber 44 from the second supply path 14, the amount of hydraulic fluid L4 sealed in the left pressure chamber 44 increases, and the piston 41 moves rightward as shown in FIG. 1. This causes the right rod 43 and the left rod 42 to move rightward as shown in FIG. 1, and the load N moves rightward. Furthermore, as the piston 41 moves to the right, the hydraulic fluid L5 sealed in the right pressure chamber 45 is discharged into the first supply path 13, and thus the hydraulic fluid L5 passes through the first supply path 13 and is supplied to the left pressure chamber 34.

[0038] On the other hand, when it is desired to move the load N leftward, first, the servo valve 2 is controlled to connect the supply port 2a to the second control path 12, and air pressure is supplied to the second control path 12 from the air pressure source 10. This causes the piston 31 to move leftward as shown in FIG. 1, and the left rod 32 to move leftward as shown in FIG. 1. This causes the left rod 32 to enter the left pressure chamber 34, thereby pushing out the hydraulic fluid L1 sealed in the left pressure chamber 34 and supplying it to the right pressure chamber 45 through the first supply path 13. When the hydraulic fluid L1 is then supplied to the right pressure chamber 45 from the first supply path 13, the amount of hydraulic fluid L5 sealed in the right pressure chamber 45 increases, and the piston 41 moves leftward as shown in FIG. 1. This causes the right rod 43 and the left rod 42 to move leftward as shown in FIG. 1, and the load N moves leftward. Furthermore, as the piston 41 moves to the left, the hydraulic fluid L4 sealed in the left pressure chamber 44 is discharged into the second supply path 14, and thus the hydraulic fluid L4 passes through the second supply path 14 and is supplied to the right pressure chamber 35.

[0039] The above-described series of operations are executed by a control unit (not shown). Specifically, first, a user or a higher-level controller sets arbitrary target values (or trajectories) for the position, speed, and force of the piston 41 of the hydraulic actuator 4. The sensors (position detection sensor 18, third pressure sensor P a , the fourth pressure sensor P b The control unit (not shown) controls the servo valve 2 and performs feedback control on the drive unit 3 so that the error between the actual value detected by the fifth pressure sensor 13 and the estimated value becomes small. At this time, the control unit (not shown) monitors the fifth pressure sensor P0 so that a constant pressure (for example, pressure P0) is applied to the first supply path 13 and the second supply path 14 as a preload.

[0040] Each estimated value is calculated by a control unit (not shown). First, the estimation of force will be described. The thrust of the piston 41 is calculated by multiplying the pressure difference by the pressure-receiving area of the piston 41. Here, the pressure difference is calculated by multiplying the pressure difference by the pressure-receiving area of the third pressure sensor P a Detected value detected by 4th pressure sensor Pb The detected value is a value detected by the third pressure sensor P1, and can be a positive or negative value. This calculation can also be performed by multiplying the differential pressure of the air pressure sensor (i.e., the detected value detected by the first pressure sensor P1 - the detected value detected by the second pressure sensor P2) by the pressure boost ratio (the value obtained by dividing the area of the left end 31a of the piston 31 by the area of the left end 32a of the left rod 32, as explained above). In this case, a , the fourth pressure sensor P b Next, the estimation of the position will be described. Instead of the position detection sensor 18 that detects the position of the piston 41, a position detection sensor 19 that detects the position of the piston 31 may be provided in the drive unit 3 as shown in FIG. 2. This makes it possible to estimate the position of the piston 41 by detecting the position of the piston 31. In this way, there is no need to attach a separate sensor to the hydraulic actuator 4, and furthermore, there is no need to install the third pressure sensor P a , the fourth pressure sensor P b Therefore, the position and force of the hydraulic actuator 4 can be remotely controlled without using a hydraulic actuator.

[0041] In this embodiment, for convenience of explanation, the hydraulic fluids are designated as L1 to L5 and are given different reference numerals, but they are all the same hydraulic fluid.

[0042] According to the present embodiment described above, the hydraulic actuator 4 can be driven simply by driving the drive unit 3 using air pressure. Furthermore, it is possible to drive the hydraulic actuator 4 using only the drive unit 3, without the need for first and second air-liquid converters as in the prior art. Furthermore, by making the areas of the left end 31a and right end 31b of the piston 31 larger than the areas of the left end 32a and right end 33a of the left rod 32 and right rod 33, it is possible to increase the pressure of the hydraulic fluids L1 and L2 supplied to the hydraulic actuator 4. As a result, according to the present embodiment, it is possible to easily realize control of various high-load hydraulic actuators, and furthermore, it is possible to make the hydraulic actuator more compact and less expensive than conventional actuators.

[0043] In the above explanation, only the preload mechanism that applies a constant pressure (for example, pressure P0) to the first supply path 13 and the second supply path 14 has been exemplified, but it is also possible to not only ensure the preload but also compensate for the amount of leakage. That is, since it is difficult to completely seal the fluid, if the fluids L1 and L2 leak to the outside for some reason, it is possible to provide a function to compensate for the amount of external leakage that has leaked to the outside and the amount of internal leakage that has leaked between the fluids L1 and L2 via the piston 41.

[0044] If these leakage amounts are left unchecked, the relative positional relationship between the piston 31 of the drive unit 3 and the piston 41 of the hydraulic actuator 4 will be shifted, making it impossible to control the position of the piston 41 of the hydraulic actuator 4 using only the position detection sensor 19 that detects the position of the piston 31 shown in Figure 2, or the piston 41 of the hydraulic actuator 4 may lean too far to one side and not function properly.

[0045] Therefore, in this embodiment, the leakage amount is compensated for as follows. That is, to determine the correspondence, for example, a magnetic sensor is disposed on the piston 41 of the hydraulic actuator 4, and the switch is set to turn on at a certain reference position. This allows the positional relationship with the piston 31 of the drive unit 3 (e.g., whether it is to the left or right) to be determined. Therefore, the pump 15 temporarily supplies hydraulic fluid L3, such as water, stored in the tank T so that the piston 41 of the hydraulic actuator 4 returns to the desired position (to the right if it is to the left, or to the left if it is to the right). To achieve this, the higher the differential pressure, the greater the supply amount. Therefore, the preload can be temporarily increased to create a pressure difference across the check valves 16 and 17. This allows the leakage amount to be compensated for. Note that if a sensor that can continuously acquire the position of the piston 41 side of the hydraulic actuator 4 is available, such leakage compensation can be more easily achieved.

[0046] The shapes and the like shown in this embodiment are merely examples, and various modifications and changes are possible within the scope of the gist of the present invention as set forth in the claims. For example, in this embodiment, an example is shown in which air pressure is supplied using one servo valve 2, but this is not limiting, and air pressure may be supplied to the drive unit 3 using two servo valves.

[0047] In addition, in this embodiment, an example is shown in which the first supply path 13 is connected to the right pressure chamber 45 and the second supply path 14 is connected to the left pressure chamber 44 in order to synchronize the movement of the piston 31 of the drive unit 3 with the movement of the piston 41 of the hydraulic actuator 4, but this is not limiting, and the first supply path 13 may be connected to the left pressure chamber 44 and the second supply path 14 may be connected to the right pressure chamber 45.

[0048] Furthermore, in this embodiment, an example has been shown in which air pressure is supplied by the air pressure source 10, but the invention is not limited to this, and oil pressure may be supplied by a hydraulic source such as a hydraulic unit instead of the air pressure source 10. In this case, the left drive pressure chamber 36 and the right drive pressure chamber 37 may be filled with oil instead of air, and a hydraulic servo valve may be used instead of the air servo valve 2.

[0049] Furthermore, in this embodiment, an example using the pump 15 and the tank T has been shown, but they may not be provided if unnecessary. However, providing them is preferable because it prevents the hydraulic fluids L1 and L2 from becoming negative pressure and also compensates for leakage. Note that the pump 15 and the tank T illustrated in this embodiment are merely examples, and they may also be driven by a hand pump, an electric pump, an air-hydro converter, an air-hydro booster, or the like.

[0050] Furthermore, in this embodiment, an example in which the check valves 16 and 17 are provided has been shown, but these are not essential and may be provided as needed.

[0051] Furthermore, in this embodiment, an example has been shown in which the servo valve 2 is used to drive the drive unit 3, but this is not limiting, and a bidirectional rotary pump may be used instead of the servo valve 2. A specific example of this point is the configuration shown in FIG. 3. Below, a hydraulic transmission 1A shown in FIG. 3 will be described. In describing the hydraulic transmission 1A shown in FIG. 3, the same components as those of the hydraulic transmission 1 shown in FIG. 1 will be assigned the same reference numerals, and description thereof will be omitted.

[0052] The hydraulic transmission 1A shown in Fig. 3 has the same configuration as the hydraulic transmission 1A shown in Fig. 1, except that the servo valve 2 is replaced with a bi-directional rotary pump 2A, which may be a fixed displacement or variable displacement pump. However, the type of pump that can be used is not limited to this.

[0053] The bidirectional rotary pump 2A is a fluid pressure pump that can be rotated in the direction of arrow Y1 (left and right in the figure) by a servo motor SM, as shown in FIG. 3 . More specifically, when the servo motor SM is rotated leftward in the figure using a control unit (not shown), fluid is pressure-fed to the first control path 11. At this time, because the left drive pressure chamber 36 is filled with fluid, the piston 31 moves rightward in FIG. 3 , and accordingly, the right rod 33 moves rightward in FIG. 3 . As a result, the right rod 33 enters the right pressure chamber 35, and the hydraulic fluid L2 sealed in the right pressure chamber 35 is pressure-fed to the hydraulic actuator 4 through the second supply path 14. As the piston 31 moves rightward in FIG. 3 , the fluid filling the right drive pressure chamber 37 is discharged into the second control path 12. As a result, the fluid is discharged through the second control path 12 to the bidirectional rotary pump 2A.

[0054] On the other hand, when the servo motor SM is rotated in the right direction in the figure using a control unit (not shown), fluid is pressure-fed to the second control path 12. At this time, because the right drive pressure chamber 37 is filled with fluid, the piston 31 moves leftward as shown in FIG. 2, and accordingly, the left rod 32 moves leftward as shown in FIG. 3. As a result, the left rod 32 enters the left pressure chamber 34, thereby pushing out the hydraulic fluid L1 sealed in the left pressure chamber 34, and the hydraulic fluid L1 is pressure-fed to the hydraulic actuator 4 through the first supply path 13. Note that as the piston 31 moves leftward as shown in FIG. 3, the fluid filling the left drive pressure chamber 36 is discharged into the first control path 11. As a result, the fluid is discharged through the first control path 11 to the bidirectional rotary pump 2A.

[0055] Even in this configuration, the hydraulic actuator 4 can be driven simply by driving the drive unit 3 using fluid. Furthermore, the hydraulic actuator 4 can be driven using only the drive unit 3, without the need for first and second air-liquid converters as in the prior art. Furthermore, by making the areas of the left end 31a and right end 31b of the piston 31 larger than the areas of the left end 32a and right end 33a of the left rod 32 and right rod 33, the pressure of the hydraulic fluids L1 and L2 supplied to the hydraulic actuator 4 can be increased. Therefore, even in this configuration, it is possible to easily control various high-load hydraulic actuators, and furthermore, the device can be made smaller and less expensive than conventional devices. Furthermore, when a liquid is used as the fluid, the use of the bidirectional rotary pump 2A circulates the liquid as described above, eliminating the need for a tank for storing the liquid.

[0056] On the other hand, a hydraulic transmission 1B shown in Fig. 4 may also be used. That is, the hydraulic transmission 1B shown in Fig. 4 has the same configuration as the hydraulic transmission 1 shown in Fig. 1 except that a small hydraulic cylinder 4B is newly provided between the first supply path 13 and the second supply path 14. Therefore, the other configurations are given the same reference numerals and descriptions thereof will be omitted.

[0057] As shown in FIG. 4, the compact hydraulic cylinder 4B includes a hollow cylinder chamber 40B, a piston 41B reciprocally disposed within the cylinder chamber 40B, and a rod 42B attached to the piston 41B. The interior of the cylinder chamber 40B is divided by the piston 41B into a left fluid chamber 43B and a right fluid chamber 44B. The left fluid chamber 43B is filled with hydraulic fluid L6B, such as water, and the right fluid chamber 44B is filled with hydraulic fluid L7B, such as water. The left fluid chamber 43B is connected to a left pressure chamber 44 of the hydraulic actuator 4 via the second supply path 14, and the right fluid chamber 44B is connected to a right pressure chamber 45 of the hydraulic actuator 4 via the first supply path 13. As a result, when the piston 41B is moved by the rod 42B, hydraulic fluid L6B is supplied to the left pressure chamber 44, and hydraulic fluid L7B is supplied to the right pressure chamber 45. Therefore, it is possible to drive the hydraulic actuator 4 using this small hydraulic cylinder 4B. Therefore, if the rod 42B is driven by an electric actuator, precise control by minute volume movement becomes easy, and if a person manually operates the rod 42B, bilateral control becomes possible while the person feels the reaction force acting on the hydraulic actuator 4 to be controlled. Furthermore, if the drive unit 3 is driven in response to human operation, it becomes possible to simultaneously achieve power assist control like that of an automobile's power steering. Note that, for convenience of explanation, different reference numerals are used for the hydraulic fluids L6B and L7B, but they are the same hydraulic fluid as the hydraulic fluids L1 to L5.

[0058] Needless to say, although Fig. 4 shows a modified example of the hydraulic transmission 1 shown in Fig. 1, it is also applicable to the hydraulic transmission 1 shown in Fig. 2 and the hydraulic transmission 1A shown in Fig. 3. Furthermore, Fig. 4 shows an example in which a small hydraulic cylinder 4B is provided, but this may be changed to a small rotary motor instead. [Explanation of symbols]

[0059] 1,1A,1B Hydrostatic Transmission 3. Drive unit (drive means) 15 Pump (mechanism) 30 Cylinder chamber 31 Piston 31a Left end (end) 31b Right end (end) 32 Left Rod (Rod) 32a Left end (one end, end) 33 Right Rod (Rod) 33a Right end (other end, end) 34 Left pressure chamber (first pressure chamber) 35 Right pressure chamber (second pressure chamber) 36 Left driving pressure chamber (first driving pressure chamber) 37 Right driving pressure chamber (second driving pressure chamber) 4 Hydraulic Actuators 40 Cylinder chamber 41 Piston 42 Left Rod 43 Right Rod 44 Left pressure chamber 45 Right pressure chamber 13 1st supply route (supply route) 14 2nd supply route (supply route) 4B Hydraulic Cylinder 16,17 Check valve L1,L2,L4,L5 Hydraulic fluid (liquid) T Tank (mechanism)

Claims

1. a driving means driven by fluid pressure; a hydraulic actuator driven by the hydraulic fluid supplied from the driving means; a supply line connected to the hydraulic actuator and the drive means; a predetermined mechanism provided in the supply path, The driving means A hollow cylinder chamber; a piston reciprocally disposed within the cylinder chamber; a rod provided on the piston, a first pressure chamber in which a liquid is sealed in advance is provided at one end of the rod; a second pressure chamber in which a liquid is sealed in advance is provided at the other end of the rod; The piston divides the cylinder chamber into a first drive pressure chamber and a second drive pressure chamber, The area of the end of the piston is larger than the area of the end of the rod, When the fluid pressure is supplied to the first drive pressure chamber, the piston moves and the liquid in the first pressure chamber is pushed out, whereby the liquid is supplied to the hydraulic actuator through the supply path, and further the liquid is returned from the hydraulic actuator to the second pressure chamber through the supply path, when the fluid pressure is supplied to the second driving pressure chamber, the piston moves and the liquid in the second pressure chamber is pushed out, whereby the liquid is supplied to the hydraulic actuator through the supply path, and further the liquid is returned from the hydraulic actuator to the first pressure chamber through the supply path, The predetermined mechanism is By applying a constant pressure to the supply path so that the liquid does not become negative pressure, the preload can be adjusted according to the state of the hydraulic actuator, and A hydraulic transmission that can supply liquid to compensate for an external leakage amount of the liquid pre-sealed in the first pressure chamber and / or the liquid pre-sealed in the second pressure chamber, or an internal leakage amount of the liquid pre-sealed in the first pressure chamber and the liquid pre-sealed in the second pressure chamber.

2. A hydraulic transmission as described in claim 1, wherein the supply path is provided with a hydraulic cylinder or a rotary pump.

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