Electro-hydraulic hybrid actuator

Abstract

This invention provides an electro-hydraulic hybrid actuator capable of maintaining balance of moments between parallel-arranged electric actuators and hydraulic actuators. [Solution] An electro-hydraulic hybrid actuator comprising a hydraulic drive unit 1, electric drive units 2a, 2b, a thrust connection unit 3 that receives thrust from the hydraulic drive unit and the electric drive unit, and an operating output unit 5a operated by the thrust connection unit, characterized in that at least two of the electric drive units are symmetrically arranged based on the arrangement of the hydraulic drive unit. By arranging the multiple electric drive units symmetrically around the axis of the hydraulic drive unit, an electro-hydraulic hybrid actuator is obtained that can maintain a balance of moments between each drive unit.

Description

Technical Field

[0001] The present invention relates to an electro-hydraulic hybrid actuator that combines an electric actuator and a hydraulic actuator.

Background Art

[0002] In recent years, with the decline of the working population, the automation of work by robots has been promoted. For automation to replace human work, robots with the same size as humans and output equal to or greater than that of humans are required. To realize such robots, a small and high-output actuator is necessary. Although hydraulic actuators have the characteristics of being small and having high output, when applied to robots that replace human work, there is a problem of slow responsiveness. In order to improve the responsiveness of this hydraulic actuator, as an example of a combination of a hydraulic actuator and an electric actuator, for example, the technology of Patent Document 1 is known.

[0003] Patent Document 1 describes that when driving an injection molding machine including an electric drive unit that drives a screw, which is a movable body, forward by an electric actuator and an auxiliary hydraulic drive unit that drives the movable body forward by a hydraulic actuator, first, the movable body is driven forward by controlling the electric drive unit, and at the same time, the load pressure Po during forward driving is detected to calculate an assist pressure of a predetermined ratio (assist ratio) with respect to the load pressure Po, and the screw is pressurized by the assist pressure by controlling the hydraulic drive unit.

[0004] Thereby, if the electric drive unit is controlled to drive the movable body forward, the control function unit detects the load pressure during forward driving and calculates the assist pressure based on a preset assist ratio. Then, the auxiliary hydraulic drive unit is controlled by the control function unit to pressurize the movable body with the assist pressure. That is, the movable body is driven forward by the electric drive unit and at the same time pressurized by the assist pressure from the auxiliary hydraulic drive unit. At this time, the pressures of the main electric drive unit and the auxiliary hydraulic drive unit are shared by the optimum assist ratio set for each control region. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-138597 [Overview of the project] [Problems that the invention aims to solve]

[0006] By the way, in an electro-hydraulic hybrid actuator, such as the one described in Patent Document 1, where an electric drive unit is the main drive unit and hydraulic drive units are arranged on both sides of the electric drive unit as auxiliary drive units, the thrust of the electric drive unit is not very large, so it is necessary to enlarge the electric drive unit. As a result, there is a problem that the electro-hydraulic hybrid actuator becomes large and unsuitable for mounting on robots and the like.

[0007] The present invention aims to provide a small electro-hydraulic hybrid actuator that can be mounted on robots and the like. [Means for solving the problem]

[0008] The present invention relates to an electro-hydraulic hybrid actuator comprising a hydraulic drive unit, an electric drive unit, a thrust connection unit that receives the thrust of the hydraulic drive unit and the electric drive unit, and an operating output unit operated by the thrust connection unit, characterized in that at least two electric drive units are symmetrically arranged based on the arrangement of the hydraulic drive unit. [Effects of the Invention]

[0009] According to the present invention, by primarily using thrust from a hydraulic drive unit that is small but has high thrust, the thrust of the electric drive unit can be reduced, and as a result, the electro-hydraulic hybrid actuator can be miniaturized. [Brief explanation of the drawing]

[0010] [Figure 1]This is a configuration diagram showing the open state of an electro-hydraulic hybrid actuator according to an embodiment of the present invention. [Figure 2] This is a diagram showing the configuration of an electro-hydraulic hybrid actuator in the closed state, according to an embodiment of the present invention. [Figure 3] This figure shows the arrangement of one hydraulic drive unit and two electric drive units in an embodiment of the present invention. [Figure 4] This diagram shows the arrangement of one hydraulic drive unit and three electric drive units in an embodiment of the present invention. [Figure 5] This diagram shows the arrangement of one hydraulic drive unit and four electric drive units in an embodiment of the present invention. [Figure 6] This is a functional block diagram showing the configuration of a control device for an electro-hydraulic hybrid actuator according to an embodiment of the present invention. [Figure 7] Figure 6 is an explanatory diagram illustrating the operation of the functional block shown. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described in detail below with reference to the drawings, but the present invention is not limited to the embodiments described below, and various modifications and applications are also included within the scope of the technical concept of the present invention.

[0012] The electro-hydraulic hybrid system shown in Figure 1 consists of a linear hydraulic actuator 1 (referred to as a hydraulic drive unit in the claims) with a large thrust, and two linear electric actuators 2a and 2b (referred to as electric drive units in the claims) with a smaller thrust than the hydraulic actuator 1, arranged in parallel. Here, "linear" means that the output shaft moves in the axial direction, not in the rotational direction.

[0013] These actuators 1, 2a, and 2b are forcefully connected via a rectangular thrust connection section 3 made of a thick plate. In this embodiment, the thrust connection section 3 is rectangular, but it is not limited to this, and various shapes can be selected. In short, the thrust connection section 3 only needs to be able to receive the thrust from the hydraulic actuator 1 and the electric actuators 2a and 2b and transmit the total thrust to the movable end effector 5a (referred to as the operation output section in the claims).

[0014] The hydraulic actuator 1 and the electric actuators 2a and 2b are arranged such that at least two of the electric actuators 2a and 2b face each other with respect to the axis of the hydraulic actuator 1. This arrangement will be explained using Figure 3.

[0015] The thrust connection unit 3 is connected to the movable end effector 5a via a force sensor 4a (referred to as an operating thrust measuring instrument in the claims). By connecting the thrust connection unit 3 and the movable end effector 5a via the force sensor 4a in this way, the force applied to the movable end effector 5a can be measured by the force sensor 4a. The thrust signal measured by the force sensor 4a is input to the control device 100.

[0016] The hydraulic actuator 1 comprises a cap chamber 1a and a rod chamber 1b, and the thrust output by the rod (referred to as a hydraulic rod in the claims) 1c is determined by the pressure balance between the cap chamber 1a and the rod chamber 1b. The thrust of the hydraulic actuator 1 is transmitted to the thrust connection section 3 via a force sensor 4b (referred to as a hydraulic thrust measuring instrument in the claims). By connecting in this manner, the force applied to the movable end effector 5a can be measured by the force sensor 4b. The thrust signal measured by the force sensor 4b is input to the control device 100.

[0017] Here, the axis of the radial center of the rod 1c intersects perpendicularly with the plane of the thrust connection part 3, and the axis of the rod 1c becomes the axis of the hydraulic actuator 1. Therefore, the thrust of the rod 1c acts perpendicular to the plane of the thrust connection part 3.

[0018] Also, on the extension of the axis of the rod 1c, a force sensor 4a and a force sensor 4b are arranged, whereby the thrust force of the rod 1c is accurately transmitted to the force sensor 4a and the force sensor 4b, so that the detection accuracy can be improved. Further, the thrust force transmitted from the thrust connection portion 3 to the movable end effector 5a is transmitted along the axis of the rod 1c.

[0019] The hydraulic actuator 1 is connected to an oil tank 7 and a pressure source 8 via a hydraulic servo valve 6. The hydraulic servo valve 6 and the cap chamber 1a are connected via a flow path 9. A pressure sensor 13a is arranged in the flow path 9.

[0020] The pressure sensor 13a measures the pressure in the flow path 9 and the cap chamber 1a. The hydraulic servo valve 6 and the rod chamber 1b are connected via a flow path 10. A pressure sensor 13b is arranged in the flow path 10. The pressure sensor 13b measures the pressure in the flow path 10 and the rod chamber 1b. The pressure signals measured by the pressure sensors 13a and 13b are input to the control device 100.

[0021] The hydraulic servo valve 6 and the tank 7 are connected via a flow path 12. The hydraulic servo valve 6 and the pressure source 8 are connected via a flow path 13. When there is no current input from the control device 100, the hydraulic servo valve 6 is in a first state in which none of the flow paths 9, 10, 11, and 12 are connected. Note that the first state is the default state, and substantially, the end effector 5 is in the state shown in FIG. 1. However, it may be a state different from the state shown in FIG. 1.

[0022] On the other hand, when there is a positive current input from the control device 100, the hydraulic servo valve 6 is in a second state shown in the closing operation of FIG. 2 in which the flow path 11 and the flow path 9 are connected and the flow path 10 and the flow path 12 are connected. In the second state, the hydraulic oil flows from the pressure source 8 into the cap chamber 1a, and the hydraulic oil flows out from the rod chamber 1b to the tank 7, so that the rod 1c generates a force in the direction in which the movable end effector 5a closes via the thrust connection portion 3.

[0023] Furthermore, when the hydraulic servo valve 6 receives a negative current input from the control device 100, it enters a third state as shown in the opening operation of Figure 1, where flow path 11 and flow path 10 are connected and flow path 9 and flow path 12 are connected. In this third state, hydraulic fluid flows from the pressure source 8 into the rod chamber 1b and flows out from the cap chamber 1a to the tank 7, causing the rod to generate a force via the thrust connection part 3 in the direction that opens the movable end effector 5a.

[0024] As the current flowing from the control device 100 to the hydraulic servo valve 6 increases, the cross-sectional area of ​​the openings in the hydraulic servo valve 6 connecting the respective flow paths in the second and third states increases. This increase in opening area increases the inflow / outflow rates to each section, causing the pressure in the cap chamber 1a or rod chamber 1b to increase integrally, up to the supply pressure of the pressure source 8, and the thrust of the rod to increase integrally. These operations are well known.

[0025] Next, the electric actuators 2a and 2b consist of a coil section (not shown), a movable element (not shown), and a rod (referred to as an electric rod in the claims) 2c fixed to the movable element. When current is passed through the coil section, thrust is generated in the movable element. The movement of the movable element is transmitted to the rod 2c and then to the thrust connection section 3 via force sensors 4c and 4d (referred to as electric thrust measuring instruments in the claims).

[0026] Here, the axis of the radial center of the rod 2c intersects perpendicularly with the plane of the thrust connection section 3, and the axis of the rod 2c becomes the axis of the electric actuators 2a and 2b. Therefore, the thrust of the rod 2c acts perpendicular to the plane of the thrust connection section 3.

[0027] Furthermore, force sensors 4c and 4d are positioned on the extension of the axis of each rod 2c, so that the thrust of each rod 2c is accurately transmitted to force sensors 4c and 4d, thereby improving detection accuracy. By connecting in this manner, the force applied to the movable end effector 5a can be measured by force sensors 4c and 4d. The thrust signals measured by force sensors 4c and 4d are input to the control device 100.

[0028] When the coil section receives a positive current input from the control device 100, the movable element acts on the rod 2c, generating a force via the thrust connection 3 that closes the movable end effector 5a. When the coil section receives a negative current input from the control device 100, the movable element acts on the rod 2c, generating a force via the thrust connection 3 that opens the movable end effector 5a. As the amount of current from the control device 100 increases, the force generated by the movable element increases proportionally.

[0029] The control device 100 controls the input current to the electric actuators 2a, 2b and the hydraulic servo valve 6 based on the measurement results of the force sensors 4a, 4b, 4c, and 4d and the pressure sensors 13a and 13b.

[0030] According to this embodiment, the hydraulic drive unit is used as the main drive unit, and the electric drive units are used as auxiliary drive units on both sides of the hydraulic drive unit, allowing for a compact electro-hydraulic hybrid actuator. In other words, by primarily using the thrust from the hydraulic drive unit, which has a large thrust even when small, the thrust of the electric drive unit can be reduced, resulting in a more compact electro-hydraulic hybrid actuator.

[0031] Next, the positional relationship between the hydraulic actuator 1, the electric actuators 2a and 2b, and the thrust connection part 3 will be explained.

[0032] Figure 3 shows a cross-section of rods 1c and 2c in a plane perpendicular to the axial direction, and further viewed in the axial direction towards the thrust connection section 3. Figure 3 is a diagram showing the arrangement of an electro-hydraulic hybrid actuator system equipped with one hydraulic actuator and two electric actuators.

[0033] The rods 2c of the electric actuators 2a and 2b are positioned on either side of the rod 1c of the hydraulic actuator 1. A force sensor 4b is positioned between the rod 1c and the thrust connection part 3. As mentioned earlier, the operating axis of the movable end effector 5a is located on the extension of the axis of the rod 1c, and the thrust from the rod 1c acts along the axis.

[0034] Furthermore, force sensors 4c and 4d are positioned between the rod 2c and the thrust connection part 3. The thrust from the rod 2c acts on the operating axis of the movable end effector 5a via the thrust connection part 3. The center C of the rod 1c and the centers C of the two rods 2c are aligned on the same line Lh on the plane of the thrust connection part 3 in a direction perpendicular to the axes of the rods 1c and 2c.

[0035] In other words, the two rods 2c are arranged in a circle with the position of rod 1c as the center. To put it another way, the two rods 2c are positioned at an angle of 180° with respect to the position of rod 1c, with rod 1c as the boundary. To put it another way, with respect to the position of rod 1c, the two rods 2c are positioned opposite each other with rod 1c in between.

[0036] Furthermore, the length L1 from the center C of rod 1c to the center C of one rod 2c on the same line Lh, and the length L2 from the center C of rod 1c to the center C of the other rod 2c, are considered to be the same length. For this reason, the two rods 2c are considered to be symmetrical with respect to rod 1c, both in terms of the line and point. In other words, the distances between the position of rod 1c and each rod 2c are equal. Here, "equal spacing" does not necessarily mean that the intervals (distances) are exactly the same, but rather that they are approximately the same.

[0037] Thus, the length L1 from the rod 1c of hydraulic actuator 1 to the rod 2c of one of the electric actuators 2a is the same as the length L2 from the rod 1c of hydraulic actuator 1 to the rod 2c of one of the electric actuators 2b. Therefore, the thrust from electric actuators 2a and 2b acts on the movable end effector 5a via the thrust connection part 3 as a moment due to lengths L1 and L2. Also, if the thrust from electric actuators 2a and 2b is the same, their respective moments will be the same value (however, the direction of action is opposite).

[0038] Therefore, in this state, even if the electric actuators 2a and 2b operate before the hydraulic actuator, the shape of the thrust connection part 3 can be maintained in its current state. In other words, tilting of the thrust connection part 3 can be suppressed. With this configuration, deformation of the seal ring due to the tilting of the rod 1c of the hydraulic actuator 1 is suppressed, and thus the phenomenon of oil leaking from the seal ring into the hydraulic actuator 1 can be suppressed.

[0039] Figure 4 shows the arrangement of an electro-hydraulic hybrid actuator system, which has one hydraulic actuator and three electric actuators. Figure 4 is a cross-sectional view of rods 1c and 2c in a plane perpendicular to the axial direction, and further viewed in the axial direction towards the thrust connection part 3.

[0040] Three electric actuator rods 2c are arranged on a circle centered on the hydraulic actuator rod 1c, with L1 being the length from the center C of rod 1c to the center C of rod 2c1, L2 being the length from the center C of rod 1c to the center C of rod 2c2, and L3 being the length from the center C of rod 1c to the center C of rod 2c3.

[0041] Here, the distances between the hydraulic actuators and each electric actuator are equal (L1=L2=L3). Furthermore, "equal spacing" here does not necessarily mean exactly the same distance; it simply means approximately the same distance.

[0042] Furthermore, the arrangement of rod 1c and the rods 2c of each electric actuator is such that the angle formed by rod 2c1, rod 1c, and rod 2c2 is θ1, the angle formed by rod 2c2, rod 1c, and rod 2c3 is θ2, and the angle formed by rod 2c3, rod 1c, and rod 2c1 is θ3.

[0043] In other words, with the hydraulic actuator as the axis, the internal angle of each electric actuator is 120° (θ1=θ2=θ3). The internal angle does not need to be a perfect 120°, but it is sufficient if it is approximately 120°. In this embodiment, the configuration is on a circle centered on the rod 1c of the hydraulic actuator, but it is sufficient if multiple electric actuators are arranged on a circle with the hydraulic actuator as the axis.

[0044] Furthermore, from the perspective of maintenance and piping management, it is best to position the electric actuator slightly off-center from directly below the hydraulic actuator. This prevents the electric actuator from being exposed to the hydraulic actuator's oil.

[0045] Figure 5 shows a cross-section of rods 1c and 2c in a plane perpendicular to the axial direction, and further viewed in the axial direction towards the thrust connection section 3. Figure 5 shows the arrangement of an electro-hydraulic hybrid actuator system equipped with one hydraulic actuator and four electric actuators.

[0046] Four electric actuator rods 2c are arranged on a circle centered on the hydraulic actuator rod 1c, with the length from the center C of rod 1c to the center C of rod 2c1 being L1, the length from the center C of rod 1c to the center C of rod 2c2 being L2, the length from the center C of rod 1c to the center C of rod 2c3 being L3, and the length from the center C of rod 1c to the center C of rod 2c4 being L4.

[0047] Here, the distances between the hydraulic actuators and each electric actuator are equal (L1=L2=L3=L4). Furthermore, "equal spacing" here does not necessarily mean exactly the same distance; it simply means approximately the same distance.

[0048] Furthermore, the arrangement of rod 1c and the rods 2c of each electric actuator is such that the angle formed by rod 2c1, rod 1c, and rod 2c2 is θ1, the angle formed by rod 2c2, rod 1c, and rod 2c3 is θ2, the angle formed by rod 2c3, rod 1c, and rod 2c4 is θ3, and the angle formed by rod 2c4, rod 1c, and rod 2c1 is θ4.

[0049] In other words, with the hydraulic actuator rod 1c as the axis, the internal angle of each electric actuator is 90° (θ1=θ2=θ3=θ4). The internal angle does not need to be a perfect 90°, but it is sufficient if it is approximately 90°.

[0050] In this embodiment, the arrangement is based on a circle centered on the rod 1c of the hydraulic actuator, but it is sufficient if multiple electric actuators are arranged on a circle with the hydraulic actuator as the axis. Also, although four electric actuators are shown on the same circle, it is sufficient if at least two opposing electric actuators are on the same circle.

[0051] Furthermore, from the perspective of maintenance and piping management, it is best to position the electric actuator slightly off-center from directly below the hydraulic actuator. This prevents the electric actuator from being exposed to the hydraulic actuator's oil.

[0052] In summary, a hydraulic-electric actuator comprising one hydraulic actuator and multiple electric actuators preferably has at least two electric actuators arranged on a circle with the hydraulic actuator as its axis, and the distance between the hydraulic actuator and the at least two electric actuators arranged on the circle is equal.

[0053] Furthermore, it is desirable from the perspective of maintaining thrust balance that all electric actuators are arranged on the same circle with the hydraulic actuator as the axis, and that the distance between each electric actuator and the hydraulic actuator is equal.

[0054] Furthermore, from the perspective of maintaining thrust balance, it is even more desirable to arrange the contact points between at least two electric actuators and the thrust connection part 3 on a circle centered on the contact point between the hydraulic actuator and the thrust connection part 3, and to arrange the contact points between each electric actuator and the thrust connection part 3 on the circle at equal intervals. The center referred to here does not necessarily have to be exactly the same center, but it is sufficient if it is approximately the center.

[0055] For example, in Figures 1 and 3, if we assume a configuration in which the electric actuator 2b is not provided, in the electro-hydraulic hybrid actuator, the electric actuator 2a is arranged in parallel with the hydraulic actuator 1, and the driving force from both drive units is transmitted to the thrust connection unit 3.

[0056] In this case, when generating thrust in the electro-hydraulic hybrid actuator, the thrust rate of the electric actuator 2a is set to be faster than the thrust rate of the hydraulic actuator 1 in order to improve responsiveness. Consequently, the thrust balance of both actuators at the thrust connection section 3 may be disrupted, and there is a risk that the balance of moments between the actuators may be disrupted.

[0057] When the balance of moments between actuators is disrupted, the thrust connection part 3 tilts. In conjunction with this, the rod 1c of the hydraulic actuator 1 also tilts, causing the liquid-tight sealing ring positioned around the rod 1c to deform from its normal sealing state, resulting in oil leaking from this part of the hydraulic actuator 1.

[0058] In contrast, in this embodiment, the two electric actuators 2a and 2b are arranged so that they face each other with the hydraulic actuator 1 as the boundary, thereby maintaining a balance of moments between each actuator. As a result, deformation of the seal ring due to the tilting of the rod 1c of the hydraulic actuator 1 is suppressed, and the phenomenon of oil leaking from the seal ring into the hydraulic actuator 1 can be suppressed.

[0059] Next, the functional blocks of the control device 100 of the electro-hydraulic hybrid system will be explained based on Figure 6.

[0060] As shown in Figure 6, the control device 100 is connected to force sensors 4a, 4b, 4c, 4d, pressure sensors 13a, 13b, electric actuators 2a, 2b, and hydraulic servo valve 6.

[0061] As shown in Figure 1, force sensors 4a, 4b, 4c, and 4d are mounted between the electric actuators 2a and 2b and the thrust connection part 3, between the hydraulic actuator 1 and the thrust connection part 3, and between the thrust connection part 3 and the movable end effector 5a to measure the thrust of the electric hydraulic hybrid actuator. Each force sensor 4a, 4b, 4c, and 4d inputs an electrical signal (thrust signal) corresponding to the thrust to the control device 100.

[0062] The control device 100 includes an interface 20, a controller 101, and an amplifier 30. The interface 20 includes a target thrust input unit 21 for setting the thrust output by the electro-hydraulic hybrid actuator. The target thrust set in the target thrust input unit 21 is input to the overall output thrust calculator F6 in the controller 101.

[0063] The controller 101 includes a total thrust calculator F1, an electric thrust calculator F2, an electric thrust calculator F3, a hydraulic thrust calculator F4, a hydraulic calculator F5, a total output thrust calculator F6, an electric output calculator F7, an electric output calculator F8, a hydraulic output thrust calculator F9, and a servo valve opening command calculator F10.

[0064] The overall thrust calculator F1 calculates the thrust of the electro-hydraulic hybrid actuator from the electrical signal corresponding to the thrust measured by the force sensor 4a. The calculated result is input to the overall output thrust calculator F6.

[0065] The electric thrust calculator F2 calculates the thrust of the electric actuator 2a from the electrical signal corresponding to the thrust measured by the force sensor 4c. The calculated result is input to the electric output calculator F7. Similarly, the electric thrust calculator F3 calculates the thrust of the electric actuator 2a from the electrical signal corresponding to the thrust measured by the force sensor 4d. The calculated result is input to the electric output calculator F8.

[0066] The hydraulic thrust calculator F4 calculates the thrust of the hydraulic actuator 1 from the electrical signal corresponding to the thrust measured by the force sensor 4b. The calculated result is input to the hydraulic output thrust calculator F9.

[0067] The hydraulic calculator F5 calculates the pressure inside the hydraulic actuator 1 from the electrical signals corresponding to the pressures measured by the pressure sensors 13a and 13b. The calculated result is input to the servo valve opening command calculator F10.

[0068] The overall thrust calculator F6 calculates the thrust that should be output by the hydraulic actuator 1 and the electric actuators 2a and 2b, respectively, based on the target thrust set in the target thrust input unit 21 and the thrust calculated by the overall thrust calculator F1.

[0069] The motor output calculator F7 calculates the thrust required by the motor actuator 2a from the thrust that the motor actuator 2a should output, which is output from the overall thrust calculator F1. The calculated result is input to the motor servo amplifier 31a.

[0070] Furthermore, the electric power calculator F8 calculates the thrust required by the electric actuator 2b from the thrust that the electric actuator 2b should output, which is output from the overall thrust calculator F1. The calculated result is input to the electric servo amplifier 31b.

[0071] The hydraulic output thrust calculator F9 calculates the thrust required by the hydraulic actuator 1 from the thrust that the hydraulic actuator 1 should output, which is output from the overall output thrust calculator F6. The calculated result is input to the servo valve opening command calculator F10.

[0072] The servo valve opening command calculator F10 calculates the opening of the hydraulic servo valve 6 based on the pressure value input from the hydraulic calculator F5 and the required thrust value input from the hydraulic output thrust calculator F9. The calculated result is input to the hydraulic servo amplifier F32.

[0073] The electric servo amplifiers F31a and F31b control the current input to the electric actuators 2a and 2b based on the target current values ​​calculated by the electric output calculators F7 and F8. The hydraulic servo amplifier F32 controls the current input to the hydraulic servo valve 6 based on the opening degree of the hydraulic servo valve calculated by the servo valve opening command calculator F10.

[0074] Figure 7 shows the time-series changes in the target thrust, the opening degree of the hydraulic servo valve 6, the thrust of the hydraulic actuator 1, the thrust of the electric actuators 2 (2a, 2b), and the total thrust of the hydraulic actuator 1 and electric actuators 2 (2a, 2b) when the target thrust is changed in steps.

[0075] Here, the target thrust is assumed to be thrust f1 from time t0 to time t1, and then change in a stepwise manner from thrust f1 to thrust f2 at time t1.

[0076] During this time, the opening degree of the hydraulic servo valve is kept at "0" from time t0 to time t1. As the target thrust changes in a stepwise manner at time t1, the opening degree of the hydraulic servo valve 6 is increased from time t1 to time t2. From time t2 to time t3, as the thrust of the hydraulic actuator 1 increases and approaches the target thrust f2, the opening degree of the hydraulic servo valve 6 approaches "0" and is kept at "0" from time t3 onward.

[0077] The thrust of the hydraulic actuator 1 is maintained at thrust f1 from time t0 to time t2, and increases from time t2 to time t3 as the opening degree of the hydraulic servo valve 6 increases.

[0078] At this time, the thrust of the hydraulic actuator 1 increases slightly later than the opening degree of the hydraulic servo valve 6 due to the typical lag effect of the hydraulic actuator 1. From time t2 to time t3, the thrust continues to increase until the opening degree of the hydraulic servo valve 6 becomes "0". At time t3, the target thrust f2 is reached and maintained at the target thrust f2 from time t3 onward.

[0079] Meanwhile, the thrusts of electric actuators 2a and 2b are kept at "0" from time t0 to time t1. Then, as the target thrust changes in a stepwise manner at time t1, the thrust increases through proportional control based on the difference between the target thrust and the total thrust. This increase in thrust is faster than the increase in thrust of hydraulic actuator 1.

[0080] Furthermore, since the hydraulic actuator 1 outputs thrust f1 until time t2, the electric actuator 2 only needs to compensate for the thrust difference between the target thrust f2 and the total thrust f1. In other words, if the fluctuation of the target thrust is small, the required thrust of the electric actuators 2 (2a, 2b) can be small, and the electric actuators 2 (2a, 2b) can be made smaller. From time t2 to time t3, as the thrust of the hydraulic actuator 1 increases and approaches the target thrust f2, the thrust of the electric actuators 2 (2a, 2b) becomes "0".

[0081] As can be seen from the figure, the thrusts of electric actuators 2a and 2b are set to the same value. Therefore, as shown in Figure 3, the same thrust acts on the thrust connection section 3 at positions L1 and L2 from the center of the rod 1c. In other words, opposite moments of the same value act on the rod 1c at the thrust connection section 3, canceling each other out.

[0082] Therefore, the thrust connection section 3 can maintain its normal state without tilting due to the opposing moments of the two electric actuators 2a and 2b. In this way, by arranging the electric actuators 2a and 2b symmetrically with respect to the axis of the hydraulic actuator 1, the shear moment acting between the hydraulic actuator 1 and the electric actuator 2 as shown in Figure 6 can be canceled out.

[0083] The total thrust increases from time t1 to time t2, with the thrusts of electric actuators 2a and 2b becoming dominant, and then increases from time t2 to time t3, with the thrust of hydraulic actuator 1 becoming dominant, changing the total thrust from f1 to f2. From time t3 onward, the total thrust remains constant at f2.

[0084] With the above configuration, compared to controlling thrust with hydraulic actuator 1 alone, the thrust rise time immediately after the target thrust changes due to the thrust of electric actuator 2 can be shortened.

[0085] Since the final target thrust is output by hydraulic actuator 1, the steady thrust of electric actuator 2 is "0," resulting in energy savings. Furthermore, if the steadily output thrust is large and the thrust fluctuation range is small, the thrust of electric actuator 2 can be smaller than that of hydraulic actuator 1, allowing for miniaturization of electric actuator 2. In addition, increasing the number of electric actuators reduces the thrust per electric actuator, thus enabling further miniaturization.

[0086] By the way, in the above explanation, the distances L1 and L2 between the center C of rod 1c and the centers C of the two rods 2c were the same length, but distances L1 and L2 may be different lengths. In this case, the thrusts of the two electric actuators 2a and 2b should be set to correspond to the different lengths, and the electric actuators 2a and 2b should be controlled so that the same moment value is obtained.

[0087] The arrangement of force sensors in this embodiment is not limited to this embodiment, and it is possible to reduce the number of force sensors. For example, the sensor configuration can be made with the value of force sensor 4b that measures the thrust of hydraulic actuator 1, and force sensors 4c and 4d that measure the thrust of electric actuators 2a and 2b, and the total thrust can be calculated by adding up the values ​​of each force sensor. This makes it possible to omit force sensor 4a.

[0088] Furthermore, it is possible to configure the system with only a force sensor 4a that measures the overall thrust and a force sensor 4c or force sensor 4d that measures the thrust of the electric actuator 2. By taking the difference between the value of force sensor 4a that measures the overall thrust and the value of force sensor 4c or force sensor 4d that measures the thrust of the electric actuator 2, the thrust of the hydraulic actuator 1 can be calculated. This allows for the omission of force sensor 4b.

[0089] In this case, the force sensor 4a, which measures the total thrust, is configured to measure a higher thrust than the force sensor 4c or force sensor 4d provided on the electric actuator 2. Since the thrust measured by force sensors 4c and 4d is smaller than that measured by 4a, the apparent resolution of the force sensors 4c and 4d can be reduced.

[0090] Furthermore, a configuration consisting only of force sensor 4a, which measures the overall thrust, and force sensor 4b, which measures the thrust of hydraulic actuator 1, is also possible. By taking the difference between the value of force sensor 4a, which measures the overall thrust, and the value of force sensor 4b, which measures the thrust of hydraulic actuator 1, the thrust of electric actuator 2 can be calculated. This allows force sensors 4c and 4d to be omitted.

[0091] As described above, the present invention relates to an electro-hydraulic hybrid actuator comprising a hydraulic drive unit, an electric drive unit, a thrust connection unit that receives the thrust of the hydraulic drive unit and the electric drive unit, and an operating output unit operated by the thrust connection unit, characterized in that at least two electric drive units are arranged facing each other with the hydraulic drive unit as the boundary.

[0092] According to this, the hydraulic drive unit is the main drive unit, and the electric drive units are auxiliary drive units on both sides of the hydraulic drive unit, which allows for a compact design of the electro-hydraulic hybrid actuator. In other words, by primarily using the thrust from the hydraulic drive unit, which has a large thrust even when small, the thrust of the electric drive unit can be reduced, resulting in a smaller electro-hydraulic hybrid actuator.

[0093] Furthermore, the present invention is not limited to the embodiments described above, but includes various modifications. The embodiments described above are explained in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. In addition, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace other configurations for the configuration of each embodiment. [Explanation of symbols]

[0094] 1...Hydraulic actuator, 1c...Rod, 2a, 2b...Electric actuator, 2c...Rod, 3...Thrust connection, 4a, 4b, 4c, 4d...Force sensor, 5a...End effector, 6...Hydraulic servo valve, 7...Tank, 8...Pressure source, 9...Flow path, 10...Flow path, 11...Flow path, 12...Flow path, 13a, 13b...Pressure sensor, 20...Interface, 21...Target thrust input, F1...Total thrust calculator, F2...Electric thrust calculator, F3...Electric thrust calculator, F4...Hydraulic thrust calculator, F5...Hydraulic calculator, F6...Total output thrust calculator, F7...Electric output calculator, F8...Electric output calculator, F9...Hydraulic output thrust calculator, F10...Servo valve opening command calculator, F30...Amplifier, F31...Electric servo amplifier, F32...Hydraulic servo amplifier, 100...Control device.

Claims

1. Hydraulic drive unit, Multiple electric drive units, The hydraulic drive unit and the thrust connection unit to which the thrust of the electric drive unit acts, In an electro-hydraulic hybrid actuator equipped with an operating output unit operated by the thrust connection unit, At least two of the electric drive units are arranged on a circle with the hydraulic drive unit as its axis, and the distance between the hydraulic drive unit and each of the electric drive units arranged on the circle is equal. An electro-hydraulic hybrid actuator characterized by the following features.

2. In the electro-hydraulic hybrid actuator according to claim 1, The two electric drive units are positioned opposite each other, with the hydraulic drive unit in between. An electro-hydraulic hybrid actuator characterized by the following features.

3. In the electro-hydraulic hybrid actuator according to claim 2, The two electric drive units are positioned at an angle of 180° with respect to the hydraulic drive unit. An electro-hydraulic hybrid actuator characterized by the following features.

4. In the electro-hydraulic hybrid actuator according to claim 1, The axial center of the hydraulic drive unit and the axial centers of the two electric drive units are located on the same line perpendicular to the axis of each drive unit. The distance from the center of the hydraulic drive unit to the center of one of the electric drive units, and the distance from the center of the hydraulic drive unit to the center of the other electric drive unit, are the same. An electro-hydraulic hybrid actuator characterized by the following features.

5. In the electro-hydraulic hybrid actuator according to claim 1, The multiple electric drive units consist of three units. Three of the aforementioned electric drive units are arranged on a circle with the aforementioned hydraulic drive unit as its axis. The distance between the hydraulic drive unit and each of the three electric drive units arranged in a circle is equal. An electro-hydraulic hybrid actuator characterized by the following features.

6. In the electro-hydraulic hybrid actuator according to claim 1, There are four of the aforementioned electric drive units. Four of the aforementioned electric drive units are arranged on a circle with the aforementioned hydraulic drive unit as its axis. An electro-hydraulic hybrid actuator characterized in that the distance between the hydraulic drive unit and each of the four electric drive units arranged in a circle is equally spaced.

7. In the electro-hydraulic hybrid actuator according to claim 1, The operating shaft of the control output unit is located in the direction of the axis of the hydraulic drive unit. An electro-hydraulic hybrid actuator characterized by the following features.

8. In the electro-hydraulic hybrid actuator according to claim 1, The hydraulic drive unit is A linear hydraulic actuator, A first flow path connecting the cap chamber of the hydraulic actuator and the proportional valve, A second flow path connecting the rod chamber of the hydraulic actuator and the proportional valve, A third flow path connecting the proportional valve and the pressure source, A fourth flow path connecting the proportional valve and the tank, The system is equipped with a hydraulic thrust measuring instrument for measuring the thrust of the hydraulic actuator, The aforementioned electric drive unit is Linear-acting electric actuators, The system is equipped with an electric thrust measuring instrument for measuring the thrust of the aforementioned electric actuator, The electric rod of the electric actuator and the hydraulic rod of the hydraulic actuator are connected to the thrust connection section. An electro-hydraulic hybrid actuator characterized by the following features.

9. In the electro-hydraulic hybrid actuator according to claim 8, The hydraulic thrust measuring instrument is positioned between the tip of the hydraulic rod of the hydraulic actuator and the thrust connection portion. The electric thrust measuring device is positioned between the tip of the electric rod of at least one of the electric actuators and the thrust connection portion. An electro-hydraulic hybrid actuator characterized by the following features.

10. In the electro-hydraulic hybrid actuator according to claim 8, The electric thrust measuring device is positioned between the tip of the electric rod of at least one of the electric actuators and the thrust connection portion. The thrust connection unit is fitted with the control output unit, and a control thrust measuring instrument is positioned between the thrust connection unit and the control output unit. Instead of using the aforementioned hydraulic thrust measuring instrument, the thrust of the hydraulic actuator is determined based on the difference in thrust from the operating thrust measuring instrument and the electric thrust measuring instrument. An electro-hydraulic hybrid actuator characterized by the following features.

11. In the electro-hydraulic hybrid actuator according to claim 8, The hydraulic thrust measuring instrument is positioned between the tip of the hydraulic rod of the hydraulic actuator and the thrust connection portion. The thrust connection unit is fitted with the control output unit, and a control thrust measuring instrument is positioned between the thrust connection unit and the control output unit. Instead of using the aforementioned electric thrust measuring device, the thrust of the electric actuator is determined based on the difference in thrust from the operating thrust measuring device and the hydraulic thrust measuring device. An electro-hydraulic hybrid actuator characterized by the following features.

12. In the electro-hydraulic hybrid actuator according to claim 9, The thrust connection unit is fitted with the control output unit. An operating thrust measuring instrument is provided between the thrust connection unit and the operating output unit. A hydraulic hybrid actuator characterized by the following features.

13. In the hydraulic hybrid actuator according to claim 8, The first and second flow paths are equipped with pressure sensors for measuring the pressure in the cap chamber and rod chamber of the hydraulic actuator. An electro-hydraulic hybrid actuator characterized by [this feature].

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