Hydraulic Drive Circuit

Abstract

To provide a hydraulic drive circuit capable of realizing the high accuracy of a hydraulic actuator, and high speed and high efficiency during high-load operation.SOLUTION: A first module portion 3A has a sub pump 30A that boosts pressure liquid supplied through a low pressure supply channel 10 by a predetermined amount and supplies it, a sub pump channel 37A and a branch channel 38A through which the pressure liquid boosted by the predetermined amount by the sub pump 30A, a high pressure supply channel 39A through which the pressure liquid boosted by the predetermined amount by the sub pump 30A, a first switch valve 31A that switches whether the high pressure supply channel 39A, the sub pump channel 37A, and the branch channel 38A are communicated or not, a second switch valve 32A that switches whether an actuator supply channel 11A, and the sub pump channel 37A are communicated or not, and a bypass channel 35A that is connected to the low pressure supply channel 10 and the actuator supply channel 11A so that the low pressure supply channel 10 and the actuator supply channel 11A are communicated without passing through the sub pump 30A.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydraulic drive circuit used in a hydraulic (oil or water) driven machine. [Background technology]

[0002] In recent years, hydraulic systems have been widely used in machinery and equipment requiring large power output, such as general industrial manipulators, robots such as hydraulic excavators and robotic arms for special-purpose vehicles, aircraft, spacecraft, and moving vehicles such as agricultural machinery like tractors.

[0003] Known examples of such hydraulic systems include the one described in Patent Document 1. The invention described in Patent Document 1 includes a cylinder, which is a type of hydraulic actuator, and a servo valve that supplies hydraulic oil discharged from a pump to the cylinder to cause the cylinder to expand and contract. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-41649 [Non-patent literature]

[0005] [Non-Patent Document 1] Nishiumi, Takao, Tanaka, Yutaka, et al., Special Feature: "Technological Trends in Hydraulic Hybrids," Journal of the Japan Society for Fluid Power, Vol. 41, No. 4, pp. 182-253, 2010. Summary of the Invention [Problem to be solved by the invention]

[0006] However, when applying such a hydraulic system to a robot, since robots today tend to have multiple axes, it is necessary to provide a cylinder and servo valve for each axis. In this case, the hydraulic oil discharged from the main pump is branched and supplied to the cylinders and servo valves provided for each axis. Therefore, the main pump must be able to provide all the required pressure and flow rate, which increases the size and cost of the main pump. Furthermore, when used with multiple axes, the maximum expected pressure must be set, which increases energy consumption on axes with low load pressure, and this impact increases in proportion to the number of hydraulic actuators.

[0007] Meanwhile, there is also known a technology such as that shown in Non-Patent Document 1. The technology shown in Non-Patent Document 1 is equipped with an electrohydrostatic actuator (EHA) that has a one-to-one pump-to-actuator relationship. This completely solves the problem of energy loss due to valves because no valves are used, and supplies the required flow rate appropriately, enabling highly efficient distributed power management.

[0008] However, the technology described in Non-Patent Document 1 has problems such as slower response than the servo valve drive method, and the pump and servo motor must be made larger in proportion to the required power and flow rate, resulting in an increase in size and cost in proportion to the number of hydraulic actuators.

[0009] The applicant has also filed a patent application, Patent Application No. 2020-161592, which has not yet been published. This application proposes a hydraulic circuit that connects a main pump, four low-cost valves, and a sub-pump to the inlet and outlet ports of a cylinder. This invention achieves a hybrid of high speed and high precision at low cost. However, there are still issues that need improvement, such as the increased size due to the large number of valves, the slow responsiveness due to the use of low-cost valves, and the low speed during high-load operation due to the small volume of the sub-pump.

[0010] In view of the above problems, the present invention aims to provide a hydraulic drive circuit that can achieve high precision of a hydraulic actuator, high speed during high load operation, and high efficiency. [Means for solving the problem]

[0011] 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.

[0012] The hydraulic drive circuit according to claim 1 comprises a main pump (2) that discharges pressurized liquid; a low-pressure supply flow path (10) through which pressurized liquid discharged from the main pump (2) passes; a module section (first module section 3A, 3AA) connected to the low-pressure supply flow path (10); an actuator supply flow path (11A) that supplies the pressure liquid supplied from the module portion (first module portion 3A, 3AA) to the hydraulic actuator (5); The module unit (first module unit 3A, 3AA) is a sub-pump (30A) that increases the pressure of the pressurized liquid supplied through the low-pressure supply flow path (10) by a predetermined amount and supplies the increased pressure; a sub-pump flow path (37A, branch flow path 38A) through which pressure liquid discharged from the sub-pump (30A) passes; a high-pressure supply flow path (39A) through which pressurized liquid, the pressure of which has been increased by a predetermined amount by the sub-pump (30A), passes; a first switching valve (31A, switching valve 31AA) that switches whether or not the high-pressure supply channel (39A) and the sub-pump channel (37A, branch channel 38A) are connected to each other; a second selector valve (32A, selector valve 31AA) for switching whether or not the actuator supply flow path (11A) and the sub-pump flow path (37A) are connected to each other; a bypass flow path (35A) connected to the low-pressure supply flow path (10) and the actuator supply flow path (11A) so that the low-pressure supply flow path (10) and the actuator supply flow path (11A) can communicate with each other without passing through the sub-pump (30A); The bypass flow path (35A) is provided with a check valve (second check valve 34A). the law of nature, There are a plurality of hydraulic actuators (5), the module units (first module units 3A, 3AA) are provided for the plurality of hydraulic actuators (5), the low-pressure supply flow paths (10) are connected to the plurality of module units, and the high-pressure supply flow paths (39A) of the plurality of module units are also connected to each other; When the discharge flow rate for operating the hydraulic actuator (5) is insufficient only by boosting the pressure by the sub-pump (30A) of one of the plurality of module sections, the first switching valve (31A, switching valve 31AA) and the second switching valve (32A, switching valve 31AA) of another module section among the plurality of module sections are switched, and the flow rates discharged from the sub-pumps of the other module sections are joined via the high-pressure supply flow path (39A), thereby enabling the hydraulic actuator (5) to operate. It is characterized by the following.

[0014] Claim 2 The hydraulic drive circuit according to the present invention is 1 In the hydraulic drive circuit (1, 1A) described above, the module section is a first module section (3A, 3AA), preparing a second module unit (3B) different from the first module unit (3A, 3AA); The second module portion (3B) is the low-pressure supply flow path (10) is connected to the actuator supply flow path (11B) via a check valve (30B); a switching valve (31B) is provided for switching whether or not the high-pressure supply channel (39A) and the actuator supply channel (11B) are connected to each other; When a plurality of the hydraulic actuators (5) are used, the first module parts (3A, 3AA) or the second module parts (3B) are arranged in parallel with respect to the plurality of hydraulic actuators (5), and the low-pressure supply flow paths (10) are connected to the first module parts (3A, 3AA) and the second module parts (3B), and the high-pressure supply flow paths (39A) of the first module parts (3A, 3AA) and the second module parts (3B) are also connected to each other. [Effects of the Invention]

[0015] 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.

[0016] According to the invention of claim 1, when the pressure of the pressurized liquid supplied to the hydraulic actuator (5) is within a predetermined pressure (P0), the sub pump (30A) is stopped or idled, and only the main pump (2) is driven. This makes it possible to achieve high response and high speed operation by, for example, the servo valve (4), and therefore the hydraulic actuator (5) can exhibit performance equivalent to that of known hydraulic servo technology.

[0017] Furthermore, if the pressure of the pressurized liquid supplied to the hydraulic actuator (5) is equal to or higher than a predetermined pressure (P0), the sub-pump (30A) is used to increase the pressure. Thus, when applying to a plurality of hydraulic actuators (5), by connecting a plurality of module units (first module units 3A, 3AA) to the low-pressure supply flow path (10), the predetermined pressure (P0) becomes a common pressure. Therefore, even if the pressure of the pressurized liquid is locally increased by the sub-pump (30A), there is no interference with the other hydraulic actuators (5), and therefore it is possible to avoid energy loss as in the conventional technology.

[0018] Furthermore, when applied to a plurality of hydraulic actuators (5), the high-pressure supply flow paths (39A) of the plurality of module parts (first module parts 3A, 3AA) are connected to each other. By doing so, During high load operation, Module 1 Sub pump (30A) Pressure increase by Not just for operating the hydraulic actuator (5) If the discharge flow rate is insufficient, Other module parts The flow rates of the discharged fluids from the sub-pumps (30A) are joined through a high-pressure supply flow path (39A), liquid This can be used in the pressure actuator (5), which solves the problem of insufficient flow rate caused by the small size of the sub-pump (30A), thereby realizing high speed and high efficiency during high load operation.

[0019] Therefore, according to the present invention, it is possible to realize high precision of the hydraulic actuator (5), high speed during high load operation, and high efficiency.

[0021] Claim 2 According to the invention, when a plurality of hydraulic actuators (5) are used, if the first module units (3A, 3AA) and the second module units (3B) are used together, it becomes unnecessary to provide a sub-pump (30A) even in the hydraulic actuators (5) that do not require the sub-pump (30A). As a result, it becomes possible to minimize the number of sub-pumps (30A), thereby achieving higher efficiency. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a circuit diagram of a hydraulic drive circuit according to an embodiment of the present invention. [Figure 2] FIG. 10 is a circuit diagram of a hydraulic drive circuit according to another embodiment of the present invention. [Figure 3] FIG. 10A is an explanatory diagram for explaining a case where the hydraulic drive circuit according to the embodiment is applied to a two-joint serial manipulator, and FIG. 10B is a diagram showing the trajectory of the tip position of the two-joint serial manipulator. [Figure 4] 3(a) is a diagram showing the trajectory of the angle of the first joint J1 shown in FIG. 3(a), and FIG. 3(b) is a diagram showing the trajectory of the angle of the second joint J2 shown in FIG. 3(a). [Figure 5] FIG. 10 is a diagram showing the relationship between flow rate and pressure at the first joint. DETAILED DESCRIPTION OF THE INVENTION

[0023] An embodiment of a hydraulic drive circuit according to the present invention will now be described in detail with reference to the drawings. In the following description, when directions such as up, down, left, and right are indicated, they refer to up, down, left, and right when viewed from the front of the illustration.

[0024] The hydraulic drive circuit of this embodiment is used in general industrial manipulators, robots such as hydraulic excavators and robot arms of specially equipped vehicles, aircraft, spacecraft, and traveling vehicles such as agricultural machinery such as tractors. Specifically, as shown in Fig. 1, the hydraulic drive circuit 1 is mainly composed of a main pump 2, a first module unit 3A, a second module unit 3B, a servo valve 4, and a hydraulic actuator 5. Each component will be described in detail below.

[0025] <Main pump description> The main pump 2 is driven by a servo motor M1 shown in FIG. 1 and discharges low-pressure fluid to a low-pressure supply flow path 10 connected to the main pump 2. This pressure fluid is made of, for example, hydraulic oil and is stored in a tank T shown in FIG. 1. When the main pump 2 is driven by the servo motor M1, it draws pressure fluid from the tank T and discharges the low-pressure pressure fluid to the low-pressure supply flow path 10.

[0026] <Explanation of the first module> As shown in FIG. 1, the first module section 3A is mainly composed of a sub-pump 30A, a first switching valve 31A, a second switching valve 32A, a first check valve 33A, and a second check valve 34A. The sub-pump 30A is driven by a servo motor M2 shown in FIG. 1 and is capable of increasing the pressure of the pressurized liquid discharged from the main pump 2 by a predetermined amount. More specifically, as shown in FIG. 1, a bypass flow path 35A is connected to the low-pressure supply flow path 10 via a connection point 10a. A branch flow path 36A is connected to the bypass flow path 35A via a branch point 35Aa. Because the branch flow path 36A is connected to the sub-pump 30A, the pressurized liquid discharged from the main pump 2 passes through the low-pressure supply flow path 10, the bypass flow path 35A, and further the branch flow path 36A before being supplied to the sub-pump 30A. As a result, when the sub-pump 30A is driven by the servo motor M2, the pressure of the pressurized fluid supplied through the low-pressure supply flow path 10, the bypass flow path 35A, and the branch flow path 36A is increased and discharged to a sub-pump flow path 37A connected to the sub-pump 30A. As shown in Fig. 1, the sub-pump flow path 37A is connected to a branch flow path 38A via a branch point 37Aa and is also connected to a second selector valve 32A. A first check valve 33A is provided in the sub-pump flow path 37A between the branch point 37Aa and the sub-pump 30A.

[0027] The first switching valve 31A is a two-position, two-port switching valve, and as shown in FIG. 1, its supply port 31Aa is connected to the branch flow path 38A and its output port 31Ab is connected to the high-pressure supply flow path 39A. Although not shown in detail, the first switching valve 31A is equipped with a spool driven by a solenoid, and can be switched between a supply position and a shutoff position depending on the position of the spool. In the supply position, the branch flow path 38A is connected to the high-pressure supply flow path 39A via a connection point 39Aa, and in the shutoff position, the connection between the branch flow path 38A and the high-pressure supply flow path 39A is shut off. This allows the first switching valve 31A to switch between communicating the branch flow path 38A and the high-pressure supply flow path 39A and between communicating and not communicating the branch flow path 38A and the high-pressure supply flow path 39A.

[0028] The second switching valve 32A is a two-position, two-port switching valve, and as shown in FIG. 1, its supply port 32Aa is connected to the sub-pump flow path 37A and its output port 32Ab is connected to the actuator supply flow path 11A. Although not shown in detail, the second switching valve 32A is equipped with a spool driven by a solenoid, and can be switched between a supply position and a shut-off position depending on the position of the spool. In the supply position, the sub-pump flow path 37A is connected to the actuator supply flow path 11A, and in the shut-off position, the connection between the sub-pump flow path 37A and the actuator supply flow path 11A is shut off. This makes it possible to switch between communicating the sub-pump flow path 37A and the actuator supply flow path 11A using the second switching valve 32A.

[0029] On the other hand, the bypass flow path 35A is connected to the actuator supply flow path 11A via a connection point 11Aa, as shown in Fig. 1. A second check valve 34A is provided in the bypass flow path 35A between the connection point 11Aa and a branch point 35Aa.

[0030] Thus, the first module unit 3A configured as described above operates as follows. That is, when the main pump 2 is driven by the servo motor M1 shown in FIG. 1, the pressurized liquid discharged from the main pump 2 passes through the low-pressure supply flow path 10, the bypass flow path 35A, and the branch flow path 36A, and is supplied to the sub-pump 30A. When the sub-pump 30A is idling or stopped, the supplied pressurized liquid remains stagnant there. Therefore, the pressurized liquid discharged from the main pump 2 that has passed through the bypass flow path 35A flows into the actuator supply flow path 11A.

[0031] On the other hand, when the sub-pump 30A is driven by the servo motor M2 shown in Fig. 1, the accumulated pressure liquid is discharged by the sub-pump 30A into the sub-pump flow path 37A. At this time, if the first switching valve 31A is positioned in the supply position, the pressure liquid discharged into the sub-pump flow path 37A flows through the branch flow path 38A into the high-pressure supply flow path 39A. Furthermore, at this time, pressure liquid generated by another first module unit 3A may also flow into the sub-pump flow path 37A through the high-pressure supply flow path 39A. This point will be described in detail later.

[0032] Furthermore, if the second switching valve 32A is located in the supply position, the pressure fluid discharged to the sub-pump flow path 37A flows into the actuator supply flow path 11A.

[0033] When the second switching valve 32A is in the supply position, the pressurized fluid discharged to the sub-pump flow path 37A flows into the actuator supply flow path 11A for the following reason. That is, when the sub-pump 30A discharges pressurized fluid into the sub-pump flow path 37A, a differential pressure (Pbst) is generated, and the discharge pressure (P0+Pbst) always exceeds the pressure (P0) discharged from the main pump 2. Therefore, when the second switching valve 32A is in the supply position, the pressure of the pressurized fluid discharged to the sub-pump flow path 37A is greater than the pressure of the pressurized fluid discharged from the main pump 2 via the bypass flow path 35A. Therefore, the pressurized fluid discharged from the main pump 2 is blocked, and the pressurized fluid discharged to the sub-pump flow path 37A flows into the actuator supply flow path 11A. At this time, a first check valve 33A is provided to prevent the pressurized liquid discharged from the blocked main pump 2 from flowing into the sub-pump 30A side and backflowing into the main pump 2, and a second check valve 34A is further provided to prevent backflow from the bypass flow path 35A side to the main pump 2.

[0034] 1 denotes a third check valve, which serves to direct the pressurized liquid flowing through the common discharge flow path 13 (described later) to the low-pressure supply flow path 10. This allows the sub-pump 30A to suck up the pressurized liquid from the common discharge flow path 13 when the main pump 2 is unavailable.

[0035] <Explanation of the second module> The second module section 3B has a conventionally well-known configuration and is mainly composed of a check valve 30B and a switching valve 31B, as shown in Fig. 1. As shown in Fig. 1, an actuator supply flow path 11B is connected to the low-pressure supply flow path 10 via a connection point 10b, and a branch flow path 32B is connected to this actuator supply flow path 11B via a branch point 11Ba. A check valve 30B is provided in this actuator supply flow path 11B between the branch point 11Ba and the connection point 10b.

[0036] The switching valve 31B is a two-position, two-port switching valve, and as shown in FIG. 1, its supply port 31Ba is connected to the branch flow path 32B and its output port 31Bb is connected to the high-pressure supply flow path 39A. Although not shown in detail, this switching valve 31B is equipped with a spool driven by a solenoid, and can be switched between a supply position and a shutoff position depending on the position of the spool. In the supply position, the branch flow path 32B is connected to the high-pressure supply flow path 39A via a connection point 39Ab, and in the shutoff position, the connection between the branch flow path 32B and the high-pressure supply flow path 39A is shut off. This allows the switching valve 31B to switch between communicating the branch flow path 32B and the high-pressure supply flow path 39A and not communicating them.

[0037] <Servo valve explanation> As shown in Fig. 1, the servo valve 4 is a three-position, four-port servo valve, with the supply port 4a communicating with actuator supply flow paths 11A and 11B, the discharge port 4b communicating with a discharge flow path 12, the control port 4c communicating with a contraction-side chamber 5a of the hydraulic actuator 5, and the control port 4d communicating with an extension-side chamber 5b of the hydraulic actuator 5. As shown in Fig. 1, the discharge flow path 12 is connected to a common discharge flow path 13, which is connected to a tank T. This allows the discharged pressure liquid to be returned to the tank T.

[0038] Although not shown in detail, the servo valve 4 is equipped with a spool driven by a solenoid, and the flow passages and opening areas can be changed continuously and with high response depending on the position of the spool from the extension-side supply position to the compression-side supply position. In the extension-side supply position, the servo valve 4 connects the contraction-side chamber 5a to the exhaust flow passage 12 and the extension-side chamber 5b to the actuator supply flow passages 11A and 11B. In the compression-side supply position, the contraction-side chamber 5a connects to the actuator supply flow passages 11A and 11B and the extension-side chamber 5b connects to the exhaust flow passage 12. Furthermore, in the shutoff position, the contraction-side chamber 5a and the extension-side chamber 5b are blocked from communication with both the actuator supply flow passages 11A and 11B and the exhaust flow passage 12. The servo valve 4 is capable of adjusting the flow rate at each of the extension-side supply position and the compression-side supply position. Such a servo valve 4 is known to have good responsiveness, and is capable of releasing pressure fluid or applying brakes even when a load is suddenly applied.

[0039] <Explanation of hydraulic actuator> 1, the hydraulic actuator 5 is made up of, for example, a cylinder, and includes a tube 50, a piston 51 movably inserted into the tube 50 and dividing the inside of the tube 50 into a contraction-side chamber 5a and an extension-side chamber 5b, and a rod 52 movably inserted into the tube 50 and connected to the piston 51. The hydraulic actuator 5 configured as above expands and contracts when pressure fluid is supplied through the actuator supply passages 11A and 11B into the tube 50. Specifically, when the pressure fluid supplied through the actuator supply passages 11A and 11B is supplied to the contraction-side chamber 5a and the extension-side chamber 5b is connected to the discharge passage 12 by control of the servo valve 4, the hydraulic actuator 5 contracts. Conversely, when the pressure fluid supplied through the actuator supply passages 11A and 11B is supplied to the extension-side chamber 5b by the control of the servo valve 4, and the contraction-side chamber 5a is connected to the discharge passage 12, the hydraulic actuator 5 performs an extension operation.

[0040] 1, when a plurality of hydraulic actuators 5 configured as described above are used, a servo valve 4 and a first module unit 3A are prepared for each of the plurality of hydraulic actuators 5, and a servo valve 4 and a second module unit 3B are prepared for one of the plurality of hydraulic actuators 5. Then, after arranging such servo valves 4, first module unit 3A, and second module unit 3B in parallel, the plurality of first module units 3A and second module units 3B are each connected to the low-pressure supply flow path 10 and to the high-pressure supply flow path 39A.

[0041] Thus, the hydraulic drive circuit 1 shown in FIG. 1 is configured in this manner.

[0042] <Explanation of hydraulic drive circuit operation> The hydraulic drive circuit 1 configured as above is used as follows. That is, the hydraulic drive circuit 1 operates in five operation modes. Each operation mode will be explained below.

[0043] <Explanation of N-mode> Position the first switching valve 31A of the first module unit 3A in the cutoff position, and position the second switching valve 32A in the supply position or the cutoff position. Then, stop or idle the drive of the sub-pump 30A. As a result, the pressurized liquid discharged from the main pump 2 that has passed through the bypass flow path 35A flows into the actuator supply flow path 11A. This is called the Nomal Mode (N-mode).

[0044] In such an N-mode, when the load on the hydraulic actuator 5 is low, high responsiveness can be ensured, similar to a general servo valve drive circuit. Also, when the flow rate of the main pump 2 is sufficient, each hydraulic actuator 5 can operate at high speed within the maximum flow rate range of the servo valve 4. Although there are various guidelines for setting the pressure (P0) discharged from the main pump 2, for example, it may be set to a value necessary to compensate for the gravity of the robot arm.

[0045] By the way, as shown in FIG. 1, since the sub-pump 30A does not exist in the second module unit 3B, the pressurized liquid discharged from the main pump 2 flows into the actuator supply flow path 11B.

[0046] <Explanation of DB-mode> Position the first switching valve 31A of the first module unit 3A in the cutoff position, and position the second switching valve 32A in the supply position.Then, drive the sub-pump 30A by the servo motor M2. As a result, as described above, the pressurized liquid discharged into the sub-pump flow path 37A (having a high pressure equal to or higher than the pressure (P0) discharged from the main pump 2) flows into the actuator supply flow path 11A. Therefore, if the discharge pressure of the sub-pump 30A is set to different values for each first module unit 3A, it is possible to set independent pressures. Therefore, this is called the Decoupled Boost Mode (DB-Mode).

[0047] In such a DB-mode, it is effective when the load of the hydraulic actuator 5 is high. However, as described above, since the pressure fluid discharged from the main pump 2 passing through the bypass flow path 35A side is blocked, unlike the N-mode described above, the flow rate supplied to the servo valve 4 is limited to the maximum discharge flow rate of each sub-pump 30A.

[0048] Note that, as shown in FIG. 1, since the sub-pump 30A does not exist in the second module unit 3B, the operation in the DB-mode cannot be performed.

[0049] <Explanation of SB-mode> Position the first switching valve 31A of the first module unit 3A at the supply position and position the second switching valve 32A at the supply position. Then, drive the sub-pump 30A by the servo motor M2. As a result, the pressure fluid discharged into the sub-pump flow path 37A flows into the actuator supply flow path 11A and also flows into the high-pressure supply flow path 39A through the branch flow path 38A. At this time, the pressure fluid flowing into the high-pressure supply flow path 39A flows into the sub-pump flow path 37A through the branch flow path 38A of another first module unit 3A depending on the state of the other first module unit 3A, and thus flows into the actuator supply flow path 11A. The state of the other first module unit 3A refers to a state where the first switching valve 31A is positioned at the supply position, the second switching valve 32A is positioned at the supply position, and the sub-pump 30A is driven by the servo motor M2. Needless to say, in this other first module unit 3A as well, the pressure fluid discharged into the sub-pump flow path 37A flows into the actuator supply flow path 11A and also flows into the high-pressure supply flow path 39A through the branch flow path 38A.

[0050] However, if such an operation is performed, it becomes possible to supply the total flow rate of the plurality of sub-pumps 30A connected to the high-pressure supply passage 39A to one or more servo valves 4. Therefore, since the high-pressure flow rate discharged by the plurality of sub-pumps 30A can be shared with other first module units 3A, this is called the Shared Boost Mode (SB-mode). However, the pressure in the high-pressure supply passage 39A will be uniquely determined to the maximum pressure. That is, it is not possible to realize two or more different pressures. Therefore, when two or more pressures are required, the first module unit 3A may be divided into two or more groups, and plugs may be inserted into the high-pressure supply passages 39A between the groups to block them. By doing so, it becomes possible to easily realize two or more different pressures without changing the system size or piping.

[0051] On the other hand, which hydraulic actuator 5 the pressure liquid merged as described above is used for will be determined by the opening degree of each servo valve 4 connected to each hydraulic actuator 5.

[0052] Note that, as shown in FIG. 1, since there is no sub-pump 30A in the second module unit 3B, it is not possible to operate in the SB-mode.

[0053] <Explanation of AB-mode> Position the first switching valve 31A of the first module unit 3A in the supply position and the second switching valve 32A in the blocking position. Then, drive the sub-pump 30A by the servo motor M2. As a result, all the pressure liquid discharged into the sub-pump passage 37A flows through the branch passage 38A and into the high-pressure supply passage 39A. This is called the Assisted Boost Mode (AB-mode). This mode is effective when supplying high-pressure and large-flow-rate pressure liquid to a specific hydraulic actuator 5.

[0054] By the way, since the second switching valve 32A of the first module unit 3A set to the AB-mode is in the cutoff position, the hydraulic fluid discharged from the main pump 2 that has passed through the bypass flow path 35A flows into the actuator supply flow path 11A.

[0055] Incidentally, as shown in FIG. 1, since the sub-pump 30A does not exist in the second module unit 3B, the operation in the AB-mode cannot be performed.

[0056] <Explanation of PTO-mode> Position the first switching valve 31A of the first module unit 3A at the supply position and position the second switching valve 32A at the supply position. Then, stop or idle the drive of the sub-pump 30A. That is, in the SB-mode, what stops or idles the drive of the sub-pump 30A is the Power-Take-Off Mode (PTO-mode). At this time, if the switching valve 31B of the second module unit 3B is positioned at the supply position, the high-pressure hydraulic fluid flowing into the high-pressure supply flow path 39A of the first module unit 3A set to the PTO-mode will flow into the branch flow path 32B. At this time, since the pressure of the high-pressure hydraulic fluid flowing into the branch flow path 32B is more dominant than the hydraulic fluid discharged from the main pump 2, the hydraulic fluid discharged from the main pump 2 is blocked, and the high-pressure hydraulic fluid flowing into the branch flow path 32B flows into the actuator supply flow path 11B. At this time, a check valve 30B is provided so that the hydraulic fluid discharged from the blocked main pump 2 does not flow back into the main pump 2.

[0057] Thus, the second module unit 3B basically operates with low-pressure hydraulic fluid and is useful when it is desired to operate with high-pressure hydraulic fluid very rarely.

[0058] According to the present embodiment described above, in N-mode, when the load is within the pressure P0 range, the sub pump 30A is stopped or idled and only the main pump 2 is driven, thereby achieving high response and high speed operation by the servo valve 4. This allows the hydraulic actuator 5 to exhibit performance equivalent to that of known hydraulic servo technology.

[0059] Furthermore, according to this embodiment, in DB-mode, the sub-pump 30A is used to increase the pressure for a load equal to or greater than the pressure P0. As a result, when applied to multiple hydraulic actuators 5, the multiple first module units 3A are each connected to the low-pressure supply flow path 10, and the discharge flow path 12 is connected to the common discharge flow path 13, so that the pressure P0 is a common pressure. Therefore, even if the pressure of the pressurized liquid is locally increased by the sub-pump 30A, there is no interference with the other hydraulic actuators 5, making it possible to avoid energy loss as in the conventional system.

[0060] Furthermore, according to this embodiment, when the discharge flow rate from only one sub-pump 30A is insufficient during high-load operation, the SB-mode or AB-mode can be used to merge the flow rates discharged from multiple sub-pumps 30A through the high-pressure supply flow path 39A, and this merged flow can be used by multiple hydraulic actuators 5. This solves the problem of insufficient flow rate caused by the small size of the sub-pump 30A, thereby making it possible to achieve high speed and high efficiency during high-load operation.

[0061] Therefore, according to this embodiment, it is possible to achieve high precision of the hydraulic actuator 5, high speed during high load operation, and high efficiency.

[0062] Furthermore, according to this embodiment, the first module unit 3A has a structure that is upwardly compatible with the conventional second module unit 3B, in that it is only necessary to incorporate the first switching valve 31A or the second switching valve 32A and the sub-pump 30A. Furthermore, the first module unit 3A has a modular structure. This allows for compactness, making it suitable as a drive source for a multi-axis robot. That is, when a typical servo valve drive circuit or EHA is applied to a serial manipulator, the proximal hydraulic actuator is often larger than the distal hydraulic actuator. Therefore, if pumps and motors of different sizes are mixed accordingly, the overall system tends to become large. Therefore, in this embodiment, the first module unit 3A has a modular structure, thereby achieving compactness.

[0063] It should be noted that 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 servo motors M1 and M2 are used, but the present invention is not limited to this, and any motor may be used.

[0064] Furthermore, in this embodiment, the servo valve 4 is exemplified, but the present invention is not limited to this, and any valve such as a proportional valve, a directional control valve, or a throttle valve may be used.

[0065] In this embodiment, the hydraulic drive circuit 1 is configured with multiple first module units 3A and one second module unit 3B. However, the first module units 3A and the second module units 3B can be combined and arranged in any order. For example, the hydraulic drive circuit 1 may be configured with only multiple first module units 3A, or multiple second module units 3B can be provided. However, at least one first module unit 3A must be provided. The provision of a second module unit 3B is useful when the hydraulic drive circuit 1 primarily operates with low-pressure hydraulic fluid and, in rare cases, operates with high-pressure hydraulic fluid. Furthermore, the provision of a second module unit 3B eliminates the need to provide a sub-pump 30A in hydraulic actuators 5 where a sub-pump 30A is not required. This allows the number of sub-pumps 30A to be minimized, thereby achieving higher efficiency.

[0066] Furthermore, in this embodiment, an example has been shown in which the first check valve 33A is provided, but it may not be provided if there is a means for reliably stopping the rotation of the sub-pump 30A.

[0067] Furthermore, in this embodiment, when multiple hydraulic actuators 5 are used, a servo valve 4 and a first module unit 3A are provided for each of the multiple hydraulic actuators 5, and a servo valve 4 and a second module unit 3B are provided for one of the multiple hydraulic actuators 5. Then, such servo valves 4, first module units 3A, and second module units 3B are arranged in parallel, and the multiple first module units 3A and second module units 3B are each connected to the low-pressure supply flow path 10 and the high-pressure supply flow path 39A. However, this is not limited to this, and any arrangement is possible as long as the five operating modes described above can be performed. However, the arrangement as in this embodiment is preferable because it allows for efficient arrangement.

[0068] Although the present embodiment illustrates an example in which the third check valve 40A is provided, this is not limiting and the third check valve 40A may not be provided. However, when the hydraulic drive circuit 1 is applied to a modular robot in which each axis operates independently, providing the third check valve 40A is preferable. That is, although the first module sections 3A in this embodiment are stacked into a single unit, they can of course be placed in separate locations and connected by piping. This is effective when incorporating the hydraulic drive circuit 1 into a modular robot in which each axis operates independently, as shown, for example, in "Sugimoto Junichi, Uekura Sadayuki, Saito Yasushi, and Gen Soho, Development of a Hydraulic Robot with Easy Disassembly and Assembly Using Single-Joint Modules," 37th Annual Conference of the Robotics Society of Japan (September 3-7, 2019)." In this case, providing the third check valve 40A in the hydraulic drive circuit 1 is preferable for independent operation.

[0069] Furthermore, in this embodiment, the flow paths are switched using the first selector valve 31A and the second selector valve 32A, but the same functions may be achieved by using a three-position four-port selector valve instead of the first selector valve 31A and the second selector valve 32A. A specific example is the configuration shown in FIG. 2. The hydraulic drive circuit 1A shown in FIG. 2 will be described below. In describing the hydraulic drive circuit 1A shown in FIG. 2, the same components as those in the hydraulic drive circuit 1 shown in FIG. 1 will be assigned the same reference numerals and description thereof will be omitted.

[0070] The first module section 3AA of the hydraulic drive circuit 1A shown in Fig. 2 uses a switching valve 31AA instead of the first switching valve 31A and the second switching valve 32A of the first module section 3A. Apart from this difference, the rest of the configuration is the same.

[0071] The switching valve 31AA is a three-position, four-port switching valve and includes a spool driven by a solenoid (not shown in detail), allowing the flow paths to be switched depending on the position of the spool. Specifically, when the spool is positioned in the center as shown in FIG. 2, the sub-pump flow path 37A is connected to the actuator supply flow path 11A and also to the high-pressure supply flow path 39A. Furthermore, when the spool is positioned on the right side as shown in FIG. 2, the sub-pump flow path 37A is connected to the actuator supply flow path 11A, and the connection to the high-pressure supply flow path 39A is cut off. Furthermore, when the spool is positioned on the left side as shown in FIG. 2, the sub-pump flow path 37A is connected to the high-pressure supply flow path 39A, and the connection to the actuator supply flow path 11A is cut off.

[0072] Thus, even when a three-position four-port switching valve is used in this manner, it is possible to achieve the same functions as the first switching valve 31A and the second switching valve 32A.

[0073] <Example> Here, the present invention will be described in more detail using examples. Fig. 3(a) illustrates a two-joint serial manipulator J, which includes a first joint J1 corresponding to a shoulder joint and a second joint J2 corresponding to an elbow. In this example, two first module units 3A are used as the hydraulic drive circuit 1 to operate the first joint J1 and the second joint J2.

[0074] In this embodiment, an example of an operation in which the workpiece W shown in FIG. 3(a) is lifted in the direction of arrow Y1 for five seconds will be described. This operation can be divided into five phases, Phases 1 to 5, as shown in FIG. 3(b) and FIG. 4. Note that FIG. 3(b) shows the trajectory of the tip position of the two-joint serial manipulator J, FIG. 4(a) shows the trajectory of the angle of the first joint J1, and FIG. 4(b) shows the trajectory of the angle of the second joint J2. Phases 1 to 5 will be described in detail below.

[0075] <Regarding Phase 1 (0 to 1 second)> In Phase 1, as shown in Fig. 4(a), the angle of the first joint J1 narrows, and as shown in Fig. 4(b), the angle of the second joint J2 widens. Therefore, high pressure is required for both the first joint J1 and the second joint J2. For this reason, both the first module unit 3A corresponding to the hydraulic actuator 5 that operates the first joint J1 and the first module unit 3A corresponding to the hydraulic actuator 5 that operates the second joint J2 operate in DB-mode. That is, the first switching valve 31A of the first module unit 3A is positioned at the cutoff position, and the second switching valve 32A is positioned at the supply position. Then, the sub-pump 30A is driven by the servo motor M2. As a result, the pressurized liquid discharged into the sub-pump flow path 37A (having a high pressure equal to or higher than the pressure (P0) discharged from the main pump 2) flows into the actuator supply flow path 11A. Specifically, the pressurized liquid in the pressure P0+Pbst and flow rate ΔQ range shown in Fig. 5 flows into the actuator supply flow path 11A. In Phase 1, the sub-pump 30A and the servo valve 4 cooperate to control the position of the hydraulic actuator 5, thereby minimizing throttling discard. Specifically, the sub-pump 30A generates the necessary inlet flow rate to achieve the desired speed of the hydraulic actuator 5, and then the servo valve 4 controls the outlet flow rate using the actual pressure drop. Fig. 5 shows the relationship between the flow rate and pressure at the first joint J1.

[0076] <Regarding Phase 2 (1 to 2 seconds)> In Phase 2, as shown in Figure 4(a), the angle of the first joint J1 further narrows, and as shown in Figure 4(b), the angle of the second joint J2 narrows. Therefore, the first joint J1 requires a high positive power, and the second joint J2 requires negative power. Therefore, the first joint J1 cannot obtain a sufficient flow rate with the sub-pump 30A alone, so the first module unit 3A corresponding to the hydraulic actuator 5 that operates the first joint J1 is operated in SB-mode. On the other hand, the second joint J2 receives power from the main pump 2, and back pressure can be easily generated by throttling the servo valve 4. Therefore, the first module unit 3A corresponding to the hydraulic actuator 5 that operates the second joint J2 is operated in AB-mode.

[0077] That is, in SB-mode, the first switching valve 31A of the first module unit 3A is placed in the supply position, and the second switching valve 32A is placed in the supply position. The sub-pump 30A is then driven by the servomotor M2. Meanwhile, in AB-mode, the first switching valve 31A of the first module unit 3A is placed in the supply position, and the second switching valve 32A is placed in the shut-off position. The sub-pump 30A is then driven by the servomotor M2. Therefore, in the first module unit 3A corresponding to the hydraulic actuator 5 that operates the second joint J2, all of the pressure fluid discharged to the sub-pump flow path 37A flows through the branch flow path 38A to the high-pressure supply flow path 39A. Therefore, the pressure fluid that flows into the high-pressure supply flow path 39A flows through the branch flow path 38A of the first module unit 3A corresponding to the hydraulic actuator 5 that operates the first joint J1 into the sub-pump flow path 37A, and thereby into the actuator supply flow path 11A. Therefore, the hydraulic actuator 5 that operates the first joint J1 receives pressurized fluid discharged from the sub-pump 30A of the first module unit 3A corresponding to the hydraulic actuator 5 that operates the second joint J2 in addition to the pressurized fluid discharged from the sub-pump 30A of the first module unit 3A corresponding to the hydraulic actuator 5 that operates the first joint J1. Specifically, pressurized fluid within the range of pressure P0+Pbst and flow rate 2ΔQ shown in FIG. 5 flows into the actuator supply flow path 11A.

[0078] On the other hand, for the first module unit 3A corresponding to the hydraulic actuator 5 that operates the second joint J2, the pressure fluid discharged from the main pump 2 that has passed through the bypass flow path 35A side will flow into the actuator supply flow path 11A.

[0079] <Regarding Phase3 (2 to 3 seconds)> In Phase3, as shown in Fig. 3(b), the tip position of the two-joint serial manipulator J is at the highest position. Further, as shown in Fig. 4(a), the angle of the first joint J1 is held, and as shown in Fig. 4(b), the angle of the second joint J2 is also held. Therefore, high pressure is required for both the first joint J1 and the second joint J2. For this reason, both the first module unit 3A corresponding to the hydraulic actuator 5 that operates the first joint J1 and the first module unit 3A corresponding to the hydraulic actuator 5 that operates the second joint J2 operate in DB-mode. As a result, the pressure fluid discharged into the sub-pump flow path 37A (having a high pressure not less than the pressure (P0) discharged from the main pump 2) will flow into the actuator supply flow path 11A.Specifically, the pressure fluid within the range of the pressure P0+Pbst and the flow rate ΔQ shown in Fig. 5 will flow into the actuator supply flow path 11A.

[0080] <Regarding Phase4 (3 to 4 seconds)> In Phase 4, as shown in Fig. 4(a), the angle of the first joint J1 is reversed compared to Phase 2, and as shown in Fig. 4(b), the angle of the second joint J2 is also reversed compared to Phase 2. Therefore, the first module unit 3A corresponding to the hydraulic actuator 5 that operates the first joint J1 operates in AB-mode by reversing the operation method of Phase 2, and the first module unit 3A corresponding to the hydraulic actuator 5 that operates the second joint J2 operates in SB-mode. As a result, for the first module unit 3A corresponding to the hydraulic actuator 5 that operates the first joint J1, the pressure fluid discharged from the main pump 2 passing through the bypass flow path 35A side flows into the actuator supply flow path 11A. Specifically, the pressure fluid within the range of the pressure P0 and flow rate Q0 shown in Fig. 5 flows into the actuator supply flow path 11A.

[0081] On the other hand, in addition to the pressure fluid discharged by the sub-pump 30A of the first module unit 3A corresponding to the hydraulic actuator 5 that operates the second joint J2, the pressure fluid discharged by the sub-pump 30A of the first module unit 3A corresponding to the hydraulic actuator 5 that operates the second joint J2 is added and flows.

[0082] <Regarding Phase 5 (4 to 5 seconds)> In Phase 5, as shown in FIG. 3(b), the tip of the two-joint serial manipulator J is at its lowest position (original position), and therefore both the first joint J1 and the second joint J2 are under low load. Therefore, both the first module unit 3A corresponding to the hydraulic actuator 5 that operates the first joint J1 and the first module unit 3A corresponding to the hydraulic actuator 5 that operates the second joint J2 are operated in N-mode. Therefore, the first switching valve 31A of the first module unit 3A is placed in the shutoff position, and the second switching valve 32A is placed in the supply position or shutoff position. Then, the sub-pump 30A is stopped or idled. As a result, the pressurized fluid discharged from the main pump 2 through the bypass flow path 35A flows into the actuator supply flow path 11A. Specifically, the pressurized fluid within the pressure P0 and flow rate Q0 ranges shown in FIG. 5 flows into the actuator supply flow path 11A.

[0083] As explained in the above examples, in this embodiment, the operating mode can be switched depending on the operating conditions, thereby achieving high precision of the hydraulic actuator 5, high speed during high load operation, and high efficiency. [Explanation of symbols]

[0084] 1.1A hydraulic drive circuit 2 Main pump 3A, 3AA 1st module part 3B Second module section 4 Servo valves 5 Hydraulic Actuators 10 Low pressure supply passage 11A, 11B Actuator supply flow path 30A sub pump 31A First switching valve 31AA Switching valve (1st switching valve, 2nd switching valve) 32A Second switching valve 33A First check valve 34A Second check valve (check valve) 35A Detour flow path 37A Sub-pump flow path 38A Branch flow path (sub-pump flow path) 39A High pressure supply line 30B check valve

Claims

1. a main pump that discharges pressurized liquid; a low-pressure supply flow path through which pressurized liquid discharged from the main pump passes; a module portion connected to the low-pressure supply flow path; an actuator supply flow path that supplies the pressure liquid supplied from the module portion to the hydraulic actuator, The module unit includes: a sub-pump that increases the pressure of the pressurized liquid supplied through the low-pressure supply flow path by a predetermined amount and supplies the increased pressure; a sub-pump flow path through which pressurized liquid discharged from the sub-pump passes; a high-pressure supply flow path through which pressurized liquid whose pressure has been increased by a predetermined amount by the sub-pump passes; a first switching valve that switches whether or not the high-pressure supply passage and the sub-pump passage are connected to each other; a second switching valve that switches whether or not the actuator supply flow path and the sub-pump flow path are connected to each other; a bypass flow path connected to the low-pressure supply flow path and the actuator supply flow path so that the low-pressure supply flow path and the actuator supply flow path can communicate with each other without passing through the sub-pump; The bypass flow path is provided with a check valve, There are a plurality of hydraulic actuators, the module units are provided for the plurality of hydraulic actuators, and the low-pressure supply flow paths are connected to the plurality of module units, and the high-pressure supply flow paths of the plurality of module units are also connected to each other; a hydraulic drive circuit that, when the discharge flow rate required to operate the hydraulic actuator is insufficient due to pressure increase by the sub-pump of one of the plurality of module sections alone, switches the first switching valve and the second switching valve of another of the plurality of module sections, and merges the flow rates discharged from the sub-pumps of the other module sections via the high-pressure supply flow path, thereby enabling the hydraulic actuator to operate.

2. the module unit is a first module unit, preparing a second module unit different from the first module unit; The second module portion is the low-pressure supply line is connected to the actuator supply line via a check valve; a switching valve is provided that switches whether or not the high-pressure supply flow path and the actuator supply flow path are connected to each other, 2. The hydraulic drive circuit according to claim 1, wherein, when a plurality of the hydraulic actuators are used, the first module unit or the second module unit is arranged in parallel with respect to the plurality of hydraulic actuators, and the low-pressure supply flow path is connected to the first module unit and the second module unit, and the high-pressure supply flow paths of the first module unit and the second module unit are also connected to each other.

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