Hydraulic pressure generating device and hydraulic working device

Abstract

A hydraulic pressure generating device includes: a hollow housing having a cylinder chamber into which working oil is injectable; a screw shaft having an external thread groove; a nut supported so as to be movable in an axial direction within the housing and having an internal thread groove; a plurality of balls housed in a rolling path formed by the opposed external thread groove and the internal thread groove; and a piston disposed so as to be slidable within the cylinder chamber and coupled to the nut, the volume of a space in the cylinder chamber into which the working oil is storable being increased or decreased by rotating the screw shaft to move the nut and the piston together in the axial direction.

Description

Technical Field

[0001] This invention relates to hydraulic generating devices and hydraulic working devices. Background Technology

[0002] In hydraulic equipment, such as hydraulic cylinders, hydraulic pumps are generally used as the driving source to generate hydraulic pressure. In contrast, in recent years, pneumatic-hydraulic boosters that use compressed air to generate hydraulic pressure, as shown in Patent Document 1, have also been widely used.

[0003] A hydraulic cylinder is a device that generates output by displacing a piston within the cylinder using hydraulic pressure, which in turn causes a stroke in the components connected to the piston. In typical hydraulic cylinders, a hydraulic pump is generally used as the drive source for generating hydraulic pressure. In contrast, as shown in Patent Document 2, a fluid pressure device that combines a motor and a ball screw to generate hydraulic pressure has also been developed.

[0004] The fluid pressure device shown in Patent Document 2 includes: an actuator having a first pressure chamber and a second pressure chamber; a first fluid pressure control cylinder connected to the first pressure chamber of the actuator, having a first plunger driven by an electric motor; a second fluid pressure control cylinder connected to the second pressure chamber of the actuator, having a second plunger driven by an electric motor; and a fluid pressure control unit that causes the first plunger and the second plunger to operate independently or simultaneously, moving in opposite directions to supply and discharge working fluid relative to the actuator. The first plunger and the second plunger each have a servo motor and a ball screw controlled by the fluid pressure control unit.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-076877

[0008] Patent Document 2: Japanese Patent Application Publication No. 11-270503 Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] However, the pneumatic-hydraulic booster shown in Patent Document 1 requires an air compressor, a solenoid valve for controlling the air compressor, and piping for air delivery to generate air pressure, resulting in a relatively large structure. Furthermore, the pneumatic-hydraulic booster has an inherent problem: it takes time to generate hydraulic pressure using the compressibility of air.

[0011] The hydraulic generating device disclosed herein was made in view of the above-mentioned problems, and its purpose is to provide a hydraulic generating device with a relatively small structure and capable of shortening the time until hydraulic pressure is generated.

[0012] In Patent Document 2, the actuator includes: a cylinder; a piston disposed within the cylinder, sandwiching a first pressure chamber and a second pressure chamber, capable of displacement in the axial direction; and a rod connected to the piston. The rod extends from the piston to the outside of the cylinder via a pressure chamber in the axial direction. Therefore, relative to the pressure chamber on the opposite side of the rod, the cross-sectional area of ​​the pressure chamber on the rod side in the orthogonal direction is reduced by an amount equivalent to the cross-sectional area of ​​the rod in the orthogonal direction.

[0013] To move the piston along its axial direction, working fluid needs to be supplied to one pressure chamber and discharged from the other. However, the cross-sectional area of ​​the pressure chamber on the rod side, orthogonal to the axis, is smaller than that of the pressure chamber on the opposite side of the rod. Therefore, when the piston moves along its axial direction, the amount of working fluid supplied to the pressure chamber on the rod side for discharge needs to be less than the amount supplied to the pressure chamber on the opposite side of the rod for discharge.

[0014] Therefore, in the fluid pressure device of Patent Document 2, the rotational speed of two servo motors is adjusted by a fluid pressure control unit, thereby ensuring that the amount of working fluid supplied to the pressure chamber on the opposite side of the piston during displacement is less than the amount supplied to the pressure chamber on the opposite side of the piston. However, according to this technology, the control of the servo motors becomes complex, and sensors for detecting the pressure in each pressure chamber are required to achieve particularly high-precision control. Furthermore, two expensive servo motors are also required, resulting in a significant increase in cost.

[0015] The hydraulic working device disclosed herein was made in view of this problem, and its purpose is to provide a motor-driven hydraulic working device with relatively low cost and simple structure.

[0016] Technical means to solve technical problems

[0017] The hydraulic generating device of the present invention is characterized by having:

[0018] A hollow housing having a cylinder chamber capable of being injected with working oil;

[0019] A lead screw shaft having an external threaded groove;

[0020] A nut, which is supported to be axially movable within the housing and has an internal threaded groove;

[0021] A plurality of balls, wherein the plurality of balls are received within a rolling path formed by opposing external threaded grooves and internal threaded grooves; and

[0022] A piston, which is slidably disposed within the cylinder chamber and connected to the nut.

[0023] By rotating the lead screw, the piston and the nut move axially together, thereby increasing or decreasing the volume of the space in the cylinder chamber that can store working oil.

[0024] The hydraulic working device of the present invention is characterized in that it includes the aforementioned hydraulic generating device, driving device, motor, and driving system.

[0025] The hydraulic generating device includes a first hydraulic generating device and a second hydraulic generating device.

[0026] The first hydraulic generating device includes:

[0027] A hollow first housing, the first housing having a first cylinder chamber capable of being injected with working oil;

[0028] A first ball screw, comprising: a screw shaft having an external threaded groove; a nut having an internal threaded groove; and a plurality of balls capable of rolling along a rolling path between the external threaded groove and the internal threaded groove; and

[0029] A first piston is slidably disposed within the first cylinder chamber and connected to a nut of the first ball screw.

[0030] The second hydraulic generating device includes:

[0031] A hollow second housing, the second housing having a second cylinder chamber capable of being injected with working oil;

[0032] A second ball screw, comprising: a screw shaft having an external threaded groove; a nut having an internal threaded groove; and a plurality of balls capable of rolling along a rolling path between the external threaded groove and the internal threaded groove; and

[0033] The second piston is slidably disposed within the second cylinder chamber and connected to the nut of the second ball screw.

[0034] The driving device has:

[0035] A cylindrical outer shell;

[0036] The first pressure chamber inside the outer casing is connected to the first cylinder chamber;

[0037] The second pressure chamber inside the outer casing is connected to the second cylinder chamber;

[0038] A drive piston that separates the first pressure chamber from the second pressure chamber; and

[0039] A drive rod that extends axially from the drive piston via the second pressure chamber.

[0040] The first ball screw and the second ball screw share a common axis, and the first cylinder chamber and the second cylinder chamber are arranged opposite each other.

[0041] The rotational force of the motor is transmitted via the drive system to the screw shafts of the first and second ball screws, thereby enabling the nut and piston of the first ball screw and the nut and piston of the second ball screw to move in the same direction relative to the first and second cylinder chambers, respectively.

[0042] The lead of the internal and external thread grooves of the first ball screw is smaller than the lead of the internal and external thread grooves of the second ball screw by a specified value.

[0043] The hydraulic working device of the present invention is characterized by comprising a drive device, a motor, and a drive system.

[0044] The hydraulic generating device includes a first hydraulic generating device and a second hydraulic generating device.

[0045] The first hydraulic generating device includes:

[0046] A hollow first housing, the first housing having a first cylinder chamber capable of injecting working oil;

[0047] A first ball screw, comprising: a screw shaft having an external threaded groove; a nut having an internal threaded groove; and a plurality of balls capable of rolling along a rolling path between the external threaded groove and the internal threaded groove; and

[0048] A first piston is slidably disposed within the first cylinder chamber and connected to a nut of the first ball screw.

[0049] The second hydraulic generating device includes:

[0050] A hollow second housing, the second housing having a second cylinder chamber capable of being injected with working oil;

[0051] A second ball screw, comprising: a screw shaft having an external threaded groove; a nut having an internal threaded groove; and a plurality of balls capable of rolling along a rolling path between the external threaded groove and the internal threaded groove; and

[0052] The second piston is slidably disposed within the second cylinder chamber and connected to the nut of the second ball screw.

[0053] The driving device has:

[0054] A cylindrical outer shell;

[0055] The first pressure chamber inside the outer casing is connected to the first cylinder chamber;

[0056] The second pressure chamber inside the outer casing is connected to the second cylinder chamber;

[0057] A drive piston that separates the first pressure chamber from the second pressure chamber; and

[0058] A drive rod that extends axially from the drive piston via the second pressure chamber.

[0059] The first ball screw and the second ball screw share a common axis, and the first cylinder chamber and the second cylinder chamber are arranged opposite each other.

[0060] The rotational force of the motor is transmitted via the drive system to the screw shafts of the first and second ball screws, thereby enabling the nut and piston of the first ball screw and the nut and piston of the second ball screw to move in the same direction relative to the first and second cylinder chambers, respectively.

[0061] The drive system includes: a first belt connecting a pulley to the rotating shaft of the motor and a pulley to the screw shaft of the first ball screw; and a second belt connecting a pulley to the rotating shaft of the motor and a pulley to the screw shaft of the second ball screw.

[0062] The pulley ratio between the two pulleys engaged by the first belt is smaller than the pulley ratio between the two pulleys engaged by the second belt by a specified value.

[0063] Invention Effects

[0064] According to the hydraulic generating apparatus disclosed herein, it is possible to provide a hydraulic generating apparatus with a relatively small structure and a shortened time until hydraulic pressure is generated.

[0065] According to the hydraulic working device of the present invention, a motor-driven hydraulic working device with relatively low cost and simple structure can be provided. Attached Figure Description

[0066] Figure 1A This is an axial sectional view of the hydraulic generating device according to the first embodiment.

[0067] Figure 1BThis is an axial sectional view of a modified hydraulic generator.

[0068] Figure 2A This is an axial sectional view of the hydraulic generating device according to the second embodiment.

[0069] Figure 2B This is an axial sectional view of a modified hydraulic generator.

[0070] Figure 3A This is an axial sectional view of the hydraulic generating device according to the third embodiment.

[0071] Figure 3B This is an axial sectional view of a modified hydraulic generator.

[0072] Figure 4A This is an axial sectional view of the hydraulic working device according to the first embodiment.

[0073] Figure 4B This is an axial sectional view of the hydraulic working device of the first modified example.

[0074] Figure 4C This is an axial sectional view of the hydraulic working device of the second variation.

[0075] Figure 5A This is an axial sectional view of the hydraulic working device according to the second embodiment.

[0076] Figure 5B This is an axial sectional view of the hydraulic working device of the first modified example.

[0077] Figure 5C This is an axial sectional view of the hydraulic working device of the second variation. Detailed Implementation

[0078] Hereinafter, embodiments of the hydraulic generating apparatus of this disclosure will be described with reference to the accompanying drawings.

[0079] (Hydraulic generating device of the first embodiment)

[0080] Figure 1A This is an axial sectional view of the hydraulic generating device according to the first embodiment.

[0081] The hydraulic generating device 100 of this embodiment includes a ball screw 1 used to convert the rotary motion of the electric motor 40, which serves as a drive source, into the linear motion of the piston 5. The axis of the ball screw 1 is defined as L.

[0082] The hydraulic generating device 100 of this embodiment includes: a ball screw 1 having a screw shaft 2, a nut 3, and a plurality of balls 4; a piston 5; a bottomed cylindrical hollow housing 6 having a cylinder chamber 6a; an anti-rotation device 20; and an electric motor 40. The housing 6 is a bottomed cylindrical shape and has an inner flange 6b at its open end. Furthermore, the inner flange 6b is formed separately from the housing 6 and is mounted to the open end of the housing 6 by means of bolts or the like after the piston 5 and the nut 3 are inserted into the housing 6.

[0083] The lead screw shaft 2 is rotatably supported on the housing 6 via a ball bearing 7. More specifically, the inner ring of the ball bearing 7 is press-fitted into the cylindrical shaft portion 2a extending axially from the lead screw shaft 2. The outer ring of the ball bearing 7 is fixed to the inner flange portion 6b formed at the end of the housing 6 by a bearing cage 8. By sealing the open end of the housing 6 with the ball bearing 7, foreign objects can be prevented from entering the housing 6 from the outside. Any rolling bearing, such as a roller bearing, can also be used instead of the ball bearing 7. The electric motor 40 is fixed to the housing 6 by means of the bearing cage 8 facing the inner flange portion 6b.

[0084] An opening with a spline groove on its inner circumference is formed at the end of the cylindrical shaft portion 2a. The rotating shaft of the electric motor 40, i.e., the spline shaft 40a, is inserted into the opening in a manner that engages with the spline groove. Therefore, when the electric motor 40 drives the spline shaft 40a to rotate, the lead screw 2 rotates integrally with it.

[0085] The lead screw shaft 2 is inserted into the inside of the nut 3 disposed inside the housing 6, and is coaxially arranged with the nut 3. In the ball screw 1 of this embodiment, the nut 3 is used as a linear motion element. Therefore, the relative rotation of the nut 3 with respect to the housing 6 is prevented by the anti-rotation device 20. The anti-rotation device 20 consists of a pin 20a protruding from the outer periphery of the housing 6 toward the inner periphery and a straight groove 5b formed on the outer periphery of the piston 5 parallel to the axis L. After the piston 5 is disposed inside the housing 6, the pin 20a can be inserted into the hole of the housing 6 while keeping the phase aligned, so that its inner end engages with the straight groove 5b. Thus, the piston 5 can move relative to the housing 6 in the direction of the axis L, but relative rotation is prevented.

[0086] The nut 3 and the inner flange 6b of the housing 6 are opposite each other and have an outer flange 3a at the distal end. A connecting part 9, such as a bolt, used for connecting with the piston 5 is installed on the outer flange 3a.

[0087] An internal thread groove 3b is formed on the inner circumference of the nut 3, and an external thread groove 2b is formed on the outer circumference of the lead screw 2. A plurality of balls 4 are housed in a spiral rolling groove formed between the internal thread groove 3b and the external thread groove 2b, allowing them to roll. When the lead screw 2 and the nut 3 rotate relative to each other, the balls 4 that reach one end of the rolling path return to the other end via a circulation path (not shown). This continues the relative rotation of the lead screw 2 and the nut 3. In this embodiment, the circulation method of the balls 4 can employ tubular, gyro-type, end-guided, or end-cap type designs, which are known technologies and therefore omitted from description.

[0088] The piston 5 has a bottomed cylindrical shape and is slidably disposed within the cylinder chamber 6a along its axial direction. The outer diameter of the outer flange 3a of the piston 5 and nut 3 is slightly smaller than the inner diameter of the housing 6. The outer flange 3a of the nut 3 is connected to the open end of the piston 5 via a connecting member 9, thereby allowing the piston 5 and nut 3 to move linearly together. The lead screw 2 extends inside the piston 5. A circumferential groove 5a is formed on the outer periphery near the bottom wall of the piston 5. An annular sealing member SL is disposed within the circumferential groove 5a to seal between the outer periphery of the piston 5 and the inner periphery of the housing 6. The space enclosed by the bottom wall end of the piston 5, the inner periphery of the housing 6, and the bottom wall constitutes a variable volume space SP in the cylinder chamber 6a capable of storing working oil. That is, a portion of the internal space of the housing 6 becomes the cylinder chamber 6a, and at least a portion of the cylinder chamber 6a becomes a variable volume space SP whose volume increases or decreases according to the displacement of the piston 5.

[0089] An opening 6c is formed to connect the exterior of the housing 6 to the variable volume space SP. A piping TB is connected to the opening 6c to connect to an external hydraulic device (not shown).

[0090] <Operating Instructions for the Hydraulic Generator>

[0091] Working oil is injected into the variable volume space SP. If the electric motor 40 rotates the spline shaft 40a according to the control from a control device (not shown), the lead screw shaft 2 rotates integrally with the spline shaft 40a. Thus, the nut 3, whose relative rotation with respect to the housing 6 has been prevented by the anti-rotation device 20, moves along with the piston 5 inside the cylinder chamber 6a. Figure 1A The piston moves to the right in a straight line. As the piston 5 moves toward the bottom wall of the housing 6, the volume of the variable volume space SP decreases, so the working oil in the variable volume space SP is discharged through the opening 6c and pumped to the hydraulic equipment (not shown) through the pipe TB.

[0092] Conversely, if the electric motor 40 reverses the spline shaft 40a according to the control from a control device (not shown), then in Figure 1AThe piston 5 moves to the left, thus expanding the volume of the variable volume space SP. The external working oil is drawn into the variable volume space SP through the opening 6c and the pipe TB.

[0093] According to this embodiment, the ball screw 1's screw shaft 2 is rotated by the electric motor 40, causing the piston 5 to move linearly, thereby reducing the volume of the variable volume space SP and generating hydraulic pressure. Therefore, the only required equipment is the equipment and wiring for driving and controlling the electric motor 40, which enables the miniaturization and low cost of the hydraulic generating device 100.

[0094] Furthermore, in this embodiment, the ball screw 1 is directly driven by the operation of the electric motor 40, which also has the advantage of a short time until hydraulic pressure is generated. The reason for this is that, since a structure is adopted in which the screw shaft 2 rotates and the nut 3 connected to the piston 5 moves directly, the inertial torque can be suppressed less compared to the case where the nut 3 is rotated, thereby shortening the time until hydraulic pressure is generated.

[0095] The hydraulic generating device 100 of this embodiment (and the embodiments described below) is preferably used for driving hydraulic cylinders, and is particularly suitable for hydraulic cylinders with low oil volume and short stroke. In hydraulic devices using hydraulic generating units based on conventional hydraulic pumps, devices such as valves for hydraulic switching and pressure regulating valves for adjusting cylinder operating speed and hydraulic pressure are required. In contrast, the hydraulic generating device 100 of this embodiment (and the embodiments described below) allows for easy modification of the piston's movement speed and stroke, and the speed and pressure of the hydraulic cylinder can be adjusted by changing the piston stroke of the hydraulic generating device 100, thus simplifying the component structure of the hydraulic device.

[0096] Furthermore, the hydraulic generator 100 of this embodiment (and the embodiments described later) can supply hydraulic pressure to one side of the hydraulic cylinder, making it suitable for single-acting cylinders, but also for double-acting hydraulic cylinders. In the case of a double-acting hydraulic cylinder, the hydraulic generator 100 of this embodiment (and the embodiments described later) can be connected to each pressure chamber separated from the piston of the hydraulic cylinder (not shown). Alternatively, hydraulic pressure can be supplied to one pressure chamber by connecting the hydraulic generator 100 of this embodiment (and the embodiments described later), and air pressure can be supplied to the other pressure chamber via air piping, etc., to reset the position of the cylinder operated by the hydraulic generator 100.

[0097] In order to shorten the time from the start of the action to the generation of hydraulic pressure (by reducing inertia through weight reduction), the screw shaft 2 of the ball screw 1 used in the hydraulic generating device 100 of this embodiment (and the embodiments described later) may also be formed in a hollow shape.

[0098] In this embodiment (and the embodiments described later), a single-row deep groove ball bearing 7 is used to support the lead screw shaft 2. However, the number and arrangement of bearings can be appropriately changed as long as they can support the axial and radial loads of the lead screw shaft 2. For example, two angular contact ball bearings can be used in a face-to-face or back-to-back configuration. Alternatively, two tapered roller bearings can be used in a face-to-face or back-to-back configuration.

[0099] (A modified hydraulic generating device)

[0100] Figure 1B This is an axial sectional view of a hydraulic generating device according to a variation of the first embodiment. This variation is similar to... Figure 1A The difference in this embodiment is that a shallow peripheral groove 5e is formed on the outer peripheral surface between the peripheral groove 5a and the straight groove 5b of the piston 5', and a sliding bearing PB is disposed in the peripheral groove 5e. The structure otherwise is the same as in the first embodiment, and therefore, repeated descriptions are omitted.

[0101] The sliding bearing PB is a thin-walled cylindrical component installed in the circumferential groove 5e formed on the outer circumferential surface of the piston 5' and in sliding contact with the inner circumferential surface of the housing 6, achieving low-friction sliding. By providing the sliding bearing PB, the direct sliding between the outer circumferential surface of the piston 5' and the inner circumferential surface of the housing 6 is prevented, thus avoiding wear on both sides. The material of the sliding bearing PB can be a metal or resin material that is softer and has good sliding properties than the piston 5' and the housing 6. As a metal material, copper alloys such as brass, aluminum alloys, and white metals can be used. On the other hand, as a resin material, PTFE, epoxy resin, polyacetal, nylon, polyethylene, and phenolic resin can be used. The sliding bearing PB is preferably installed near the variable volume space SP side of the piston 5'. Alternatively, the sliding bearing PB can also be configured to be installed on multiple circumferential grooves formed axially separately on the piston 5'.

[0102] (Hydraulic generating device according to the second embodiment)

[0103] Figure 2A This is an axial sectional view of the hydraulic generating device according to the second embodiment.

[0104] The hydraulic generating device 100 of this embodiment includes a ball screw 11 used to convert the rotary motion of an electric motor 40, which serves as a drive source, into the linear motion of a piston 15. The axis of the ball screw 11 is defined as L.

[0105] The hydraulic generating device 100 of this embodiment includes: a ball screw 11 having a screw shaft 12, a nut 13, and a plurality of balls 14; a piston 15; a bottomed cylindrical hollow housing 16 having a cylinder chamber 16a; an anti-rotation device 20; and an electric motor 40. In this embodiment, the housing 16 is a bottomed cylindrical shape, with an expanded-diameter cylindrical portion 16f forming the cylinder chamber 16a and a reduced-diameter cylindrical portion 16e with an inner diameter smaller than the expanded-diameter cylindrical portion 16f arranged axially. An inner flange portion 16b is disposed adjacent to the expanded-diameter cylindrical portion 16f at the open end. Furthermore, the inner flange portion 16b is formed separately from the housing 16, and after the piston 15 and the nut 13 are inserted into the housing 16, it is mounted to the open end of the housing 16 using bolts or the like.

[0106] The lead screw shaft 12 is rotatably supported on the housing 16 via a ball bearing 17. More specifically, the inner ring of the ball bearing 17 is press-fitted into the cylindrical shaft portion 12a extending axially from the lead screw shaft 12, and the outer ring of the ball bearing 17 is fixed to the inner flange portion 16b formed at the end of the housing 16 by a bearing cage 18. By sealing the open end of the housing 16 with the ball bearing 17, foreign objects can be prevented from entering the housing 16 from the outside. Any rolling bearing, such as a roller bearing, can also be used instead of the ball bearing 17. The electric motor 40 is fixed to the housing 16 by means of the bearing cage 18, which is opposed to the inner flange portion 16b.

[0107] An opening with a spline groove on its inner circumference is formed at the end of the cylindrical shaft portion 12a. The rotating shaft of the electric motor 40, i.e., the spline shaft 40a, is inserted into the opening in a manner that engages with the spline groove. Therefore, when the electric motor 40 drives the spline shaft 40a to rotate, the lead screw shaft 12 rotates integrally with it.

[0108] The lead screw 12 is inserted into the inside of the nut 13 disposed inside the housing 16 and is coaxially arranged with the nut 13. Relative rotation of the nut 13 relative to the housing 16 is prevented by an anti-rotation device 20. The anti-rotation device 20 consists of a pin 20a protruding from the outer periphery of the housing 16 toward the inner periphery and a straight groove 15d formed on the outer periphery of the piston 15 parallel to the axis L. After the piston 15 is disposed within the housing 16, the pin 20a can be inserted into the hole in the housing 16 while maintaining phase alignment, so that its inner end engages with the straight groove 15d. Thus, the piston 15 can move relative to the housing 16 in the direction of the axis L, but relative rotation is prevented.

[0109] The nut 13 has an outer flange 13a near its end opposite the inner flange 16b of the housing 16. A connecting element 19, such as a bolt, for connection with the piston 15 is installed on the outer flange 13a.

[0110] An internal threaded groove 13b is formed on the inner circumference of the nut 13, and an external threaded groove 12b is formed on the outer circumference of the lead screw 12. A plurality of balls 14 are housed in a helical rolling groove formed between the internal and external threaded grooves 13b and 12b, allowing them to roll. When the lead screw 12 and nut 13 rotate relative to each other, the balls 14 that reach one end of the rolling path return to the other end via a circulation path (not shown). This continues the relative rotation of the lead screw 12 and nut 13. In this embodiment, the circulation method for the balls 14 can also be a tubular type, a gyroscope type, an end-guided type, or an end-cap type.

[0111] The piston 15 is continuously formed by a thin-walled cylindrical portion 15c and a thick-walled cylindrical portion 15b, the thick-walled cylindrical portion 15b being thicker than the thin-walled cylindrical portion 15c and continuously arranged coaxially with the thin-walled cylindrical portion 15c. The thick-walled cylindrical portion 15b is disposed radially inside the expanded-diameter cylindrical portion 16f, and its outer diameter is the same as or slightly smaller than the inner diameter of the expanded-diameter cylindrical portion 16f. Additionally, the outer diameter of the outer flange portion 13a of the nut 13 is the same as or slightly smaller than the inner diameter of the expanded-diameter cylindrical portion 16f. A portion of the thin-walled cylindrical portion 15c is disposed radially inside the reduced-diameter cylindrical portion 16e, and its outer diameter is the same as or slightly smaller than the inner diameter of the reduced-diameter cylindrical portion 16e. The piston 15 abuts the thick-walled cylindrical portion 15b against the outer flange portion 13a, and the outer periphery of the piston 15 is relatively movable and fitted into the inner periphery of the expanded-diameter cylindrical portion 16f. The inner peripheries of the thin-walled cylindrical portion 15c and the thick-walled cylindrical portion 15b are fitted into the outer periphery of the nut 13 in a manner that prevents relative rotation. Together with the nut 13, they are slidably disposed within the cylinder chamber 16a along the axial direction. Preferably, the end of the reduced-diameter cylindrical portion 16e of the piston 15 and the end of the reduced-diameter cylindrical portion 16e of the nut 13 are axially aligned and coplanar.

[0112] A circumferential groove 15a is formed on the outer periphery near the end of the thick-walled cylindrical portion 15b, which is close to the thin-walled cylindrical portion 15c. An annular first sealing member SL1 is disposed within the circumferential groove 15a. The first sealing member SL1 seals the outer periphery of the thick-walled cylindrical portion 15b with the inner periphery of the expanded-diameter cylindrical portion 16f of the housing 16. On the other hand, a circumferential groove 16d is formed on the inner periphery near the end of the reduced-diameter cylindrical portion 16e, which is close to the expanded-diameter cylindrical portion 16f of the housing 16. An annular second sealing member SL2 is disposed within the circumferential groove 16d. The second sealing member SL2 seals the outer periphery of the thin-walled cylindrical portion 15c of the piston 15 with the inner periphery of the reduced-diameter cylindrical portion 16e of the housing 16. Alternatively, a sealing groove can be provided on the outer periphery of the piston 15 to accommodate the second sealing member. Between the axially separated thick-walled cylindrical portion 15b and the reduced-diameter cylindrical portion 16e, the space enclosed by the outer periphery of the piston 15 (thin-walled cylindrical portion 15c) and the inner periphery of the housing 16 (expanded-diameter cylindrical portion 16f) constitutes a variable-volume space SP in the cylinder chamber 16a capable of storing working oil. That is, a portion of the internal space of the housing 16 becomes the cylinder chamber 16a, and at least a portion of the cylinder chamber 16a becomes a variable-volume space SP whose volume increases or decreases according to the displacement of the piston 15.

[0113] The piston 15 has: a clearance groove 15g formed on the inner circumference of the thin-walled cylindrical portion 15c and the thick-walled cylindrical portion 15b and extending straight along the axis L; and a connecting hole 15h connecting the inner and outer circumferences of the thick-walled cylindrical portion 15b. One end of the clearance groove 15g opens into the space inside the reduced-diameter cylindrical portion 16e, and the other end of the clearance groove 15g communicates with the inner end of the connecting hole 15h. The clearance groove 15g and the connecting hole 15h constitute an air passage.

[0114] Near the reduced-diameter cylindrical portion 16e of the expanded-diameter cylindrical portion 16f, an opening 16c is formed to connect the exterior of the housing 16 with the variable volume space SP. A piping TB is connected to the opening 16c to connect to an external hydraulic device (not shown).

[0115] <Operating Instructions for the Hydraulic Generator>

[0116] Working oil is injected into the variable volume space SP. If the electric motor 40 rotates the spline shaft 40a under the control of a control device (not shown), the lead screw shaft 12 rotates integrally with the spline shaft 40a. Thus, the nut 13, whose relative rotation with respect to the housing 16 has been prevented by the anti-rotation device 20, moves along with the piston 15 inside the cylinder chamber 16a. Figure 2AThe piston moves linearly to the right. At this time, the thick-walled cylindrical portion 15b of the piston 15 slides relative to the expanding cylindrical portion 16f, and the thin-walled cylindrical portion 15c slides relative to the contracting cylindrical portion 16e. Either portion can also slide relative to the other. Due to the movement of the piston 15, the thick-walled cylindrical portion 15b displaces towards the stepped portion of the expanding cylindrical portion 16f and the contracting cylindrical portion 16e, thereby reducing the volume of the variable volume space SP. Therefore, the working oil in the variable volume space SP is discharged through the opening 16c and pressurized to a hydraulic device (not shown) via the piping TB.

[0117] Conversely, if the electric motor 40 reverses the spline shaft 40a according to the control from a control device (not shown), then in Figure 2A The piston 5 moves to the left, thus expanding the volume of the variable volume space SP. The external working oil is drawn into the variable volume space SP through the opening 16c and the pipe TB.

[0118] In this embodiment, an electric motor 40 is used to rotate the ball screw shaft 12, causing the piston 15 to move linearly and reducing the volume of the variable volume space SP, thereby generating hydraulic pressure. Therefore, only the equipment and wiring for driving and controlling the electric motor 40 are required, enabling miniaturization and cost reduction of the hydraulic generating device 100. Furthermore, because a structure is adopted where the screw shaft 12 rotates and the nut 13 connected to the piston 15 moves linearly, the inertial torque can be suppressed less compared to the case where the nut is rotated, thereby shortening the time until hydraulic pressure is generated. Additionally, compared to… Figure 1A Compared to the previous implementation, by providing a cylinder chamber 16a on the radially outer side of the thin-walled cylindrical portion 15c of the piston 15, the axial length of the hydraulic generating device 100 can be shortened.

[0119] Furthermore, in this embodiment, when the piston 15 travels axially, the air in the air chamber AP (within the reduced-diameter cylindrical portion 16e) is pressurized or depressurized, thus the handling of the air in the air chamber AP becomes a problem. According to this embodiment, for example, when the air in the air chamber AP is pressurized, the air moves towards the ball bearing 17 side via the clearance groove 15g and the connecting hole 15h, through the gap between the inner circumference of the housing 16 and the outer circumference of the thick-walled cylindrical portion 15b and the outer circumference of the outer flange portion 13a. Conversely, when the air in the air chamber AP is depressurized, the air on the ball bearing 17 side returns to the air chamber AP via the clearance groove 15g and the connecting hole 15h. Therefore, when the piston 15 travels axially, the resistance caused by the pressurization or depressurization of the air in the air chamber AP can be suppressed, and the piston 15 can move smoothly.

[0120] (A modified hydraulic generating device)

[0121] Figure 2BThis is an axial sectional view of the hydraulic generating device 100 of a modified example of the second embodiment. This modified example is... Figure 2A The difference in this embodiment is that a shallow circumferential groove 15e is formed on the outer circumferential surface between the circumferential groove 15a and the straight groove 15d of the piston 15', and a sliding bearing PB is disposed in the circumferential groove 15e. The structure otherwise is the same as in the second embodiment, and therefore, repeated descriptions are omitted.

[0122] The sliding bearing PB is a thin-walled cylindrical component installed in the circumferential groove 15e formed on the outer circumferential surface of the piston 15' and in sliding contact with the inner circumferential surface of the housing 16, achieving low-friction sliding. By providing the sliding bearing PB, the direct sliding between the outer circumferential surface of the piston 15' and the inner circumferential surface of the housing 16 is prevented, thus avoiding wear between them. The material of the sliding bearing PB is the same as in the modified example described above.

[0123] (Hydraulic generating device according to the third embodiment)

[0124] Figure 3A This is an axial sectional view of the hydraulic generating device according to the third embodiment.

[0125] The hydraulic generating device 100 of this embodiment differs from the second embodiment in that it has a piston nut 23 that integrates the piston and nut. That is, the hydraulic generating device 100 of this embodiment includes: a ball screw 21 having a screw shaft 12, a piston nut 23, and a plurality of balls 14; a bottomed cylindrical hollow housing 16 having a cylinder chamber 16a; an anti-rotation device 20; and an electric motor 40. The structure other than the piston nut 23 is the same as in the above embodiment, therefore, some repetitive descriptions are omitted.

[0126] The piston nut 23 is continuously formed by a thin-walled cylindrical portion 23c and a thick-walled cylindrical portion 23b, the thick-walled cylindrical portion 23b being thicker than the thin-walled cylindrical portion 23c and continuously arranged coaxially with the thin-walled cylindrical portion 23c. The outer diameter of the thick-walled cylindrical portion 23b is the same as or slightly smaller than the inner diameter of the expanded-diameter cylindrical portion 16f of the housing 16. The anti-rotation device 20 consists of a pin 20a protruding from the outer periphery of the housing 16 toward the inner periphery and a straight groove 23d formed on the outer periphery of the piston nut 23 parallel to the axis L.

[0127] An internal thread groove 23k is formed on the inner circumference of the piston nut 23, and an external thread groove 12b is formed on the outer circumference of the lead screw shaft 12. A plurality of balls 14 are accommodated in a spiral rolling groove formed between the internal thread groove 23k and the external thread groove 12b in a rolling manner.

[0128] In this embodiment, end caps 30 are installed at both ends of the piston nut 23 as the circulation path for the ball bearings 14. The end caps 30 function to return the ball bearings 14, which have rolled to one end along one of two through holes (not shown) extending along the axis L inside the piston nut 23, to the end of the other through hole. By providing the end caps 30, the outer diameter of the piston nut 23 can be suppressed, providing an elongated hydraulic generator 100. Note that end guides can be provided instead of end caps 30.

[0129] A peripheral groove 23a is formed on the outer periphery near the end of the thick-walled cylindrical portion 23b, which is close to the thin-walled cylindrical portion 23c. An annular first sealing member SL1 is disposed within the peripheral groove 23a. The first sealing member SL1 seals the outer periphery of the thick-walled cylindrical portion 23b with the inner periphery of the housing 16. On the other hand, a peripheral groove 16d is formed on the inner periphery near the end of the reduced-diameter cylindrical portion 16e, which is close to the expanded-diameter cylindrical portion 16f, of the housing 16. An annular second sealing member SL2 is disposed within the peripheral groove 16d. The second sealing member SL2 seals the outer periphery of the thin-walled cylindrical portion 23c of the piston nut 23 with the inner periphery of the housing 16. Alternatively, a sealing groove can be provided on the outer periphery of the piston nut 23 to accommodate the second sealing member. Between the axially separated thick-walled cylindrical portion 23b and the reduced-diameter cylindrical portion 16e, the space enclosed by the outer periphery of the piston nut 23 (thin-walled cylindrical portion 23c) and the inner periphery of the housing 16 (expanded-diameter cylindrical portion 16f) constitutes a variable-volume space SP in the cylinder chamber 16a capable of storing working oil. That is, a portion of the internal space of the housing 16 becomes the cylinder chamber 16a, and at least a portion of the cylinder chamber 16a becomes a variable-volume space SP whose volume increases or decreases according to the displacement of the piston nut 23.

[0130] <Operating Instructions for the Hydraulic Generator>

[0131] Working oil is injected into the variable volume space SP. If the electric motor 40 rotates the spline shaft 40a under the control of a control device (not shown), the lead screw shaft 12 rotates integrally with the spline shaft 40a. As a result, the piston nut 23, whose relative rotation with respect to the housing 16 has been prevented by the anti-rotation device 20, moves linearly to the right in Figure 3 inside the cylinder chamber 16a. At this time, the thick-walled cylindrical portion 23b of the piston nut 23 slides relative to the expanding cylindrical portion 16f, and the thin-walled cylindrical portion 23c slides relative to the reducing cylindrical portion 16e. Either side can also slide relative to each other. By moving the piston nut 23, the thick-walled cylindrical portion 23b displaces toward the stepped portion of the expanding cylindrical portion 16f and the reducing cylindrical portion 16e, thereby reducing the volume of the variable volume space SP. Therefore, the working oil in the variable volume space SP is discharged through the opening 16c and pumped to a hydraulic device (not shown) via the piping TB.

[0132] Conversely, if the electric motor 40 reverses the spline shaft 40a according to the control from a control device (not shown), then in Figure 3A The piston nut 23 moves to the left, thus expanding the volume of the variable volume space SP. External working oil is drawn into the variable volume space SP through the opening 16c and the pipe TB.

[0133] In this embodiment, an air passage 23i is formed that connects the outer periphery of the thick-walled cylindrical portion 23b of the piston nut 23 to the air chamber side end face of the thin-walled cylindrical portion 23c. However, since end caps 30 are installed at both ends of the piston nut 23, the open end of the air passage 23i is blocked by the end caps 30. Therefore, a vent hole 30a is provided in the end cap 30 disposed in the air chamber AP at a position that does not interfere with the internal circulation path, connecting the air chamber side end of the air passage 23i to the outside. As a result, when the piston nut 23 is in motion, air can move between the air chamber AP (inside the reduced-diameter cylindrical portion 16e) and the outside of the piston nut 23 via the vent hole 30a and the air passage 23i.

[0134] (A modified hydraulic generating device)

[0135] Figure 3B This is an axial sectional view of the hydraulic generating device of a modified example of the third embodiment. This modified example is... Figure 3A The difference in this embodiment is that a shallow peripheral groove 25e is formed on the outer peripheral surface between the peripheral groove 23a and the straight groove 23d of the piston nut 23', and a sliding bearing PB is disposed in the peripheral groove 25e. The structure is otherwise the same as in the third embodiment, and therefore, repeated descriptions are omitted.

[0136] The sliding bearing PB is a thin-walled cylindrical component mounted in the circumferential groove 25e formed on the outer circumferential surface of the piston nut 23' and slidably contacting the inner circumferential surface of the housing 16, thus achieving low-friction sliding. By providing the sliding bearing PB, the direct sliding between the outer circumferential surface of the piston nut 23' and the inner circumferential surface of the housing 16 is prevented, thus avoiding wear between them. The material of the sliding bearing PB is the same as in the modified example described above.

[0137] This invention is not limited to the embodiments described above. Within the scope of this invention, any modifications to the constituent elements of the above embodiments are possible. Furthermore, any constituent elements can be added or omitted in the above embodiments. For example, in the connection between the electric motor 40 and the lead screw shaft 12, a coupling or the like can be used instead of the spline shaft 40a.

[0138] Hereinafter, embodiments of the hydraulic working device of the present invention will be described with reference to the accompanying drawings.

[0139] (The hydraulic working device of the first embodiment)

[0140] Figure 4A This is an axial sectional view of the hydraulic working device according to the first embodiment.

[0141] The hydraulic working device of this embodiment includes a hydraulic generating device 100 and a drive device 200. The hydraulic generating device 100 includes a first hydraulic generating device 110, a second hydraulic generating device 120, an electric motor 140, and a drive system 150 that transmits the rotational force of the electric motor 140 to the first hydraulic generating device 110 and the second hydraulic generating device 120. The first hydraulic generating device 110 and the second hydraulic generating device 120 share a common axis L1. Therefore, a compact hydraulic working device can be provided.

[0142] (First hydraulic generating device)

[0143] The first hydraulic generating device 110 includes a first ball screw 111, a first piston 115, a hollow first housing 116 having a first cylinder chamber 116a, and an anti-rotation device 117. The first ball screw 111 includes a screw shaft 112, a nut 113, and a plurality of balls 114. The first housing 116 is a bottomed cylindrical shape, with an open end side (…). Figure 4A The left side of the first housing 116 has an inner flange portion 116b. In addition, the inner flange portion 116b is formed separately from the first housing 116 and is installed at the open end of the first housing 116 by means of bolts or the like after the first piston 115 and nut 113 are inserted into the first housing 116.

[0144] The lead screw 112 is rotatably supported on the first housing 116 via a first ball bearing 118. More specifically, the inner ring of the first ball bearing 118 is press-fitted into the cylindrical shaft portion 112a extending axially from the lead screw 112. The outer ring of the first ball bearing 118 is fixed to the inner flange portion 116b formed at the end of the first housing 116 by a motor cage 141. By using the first ball bearing 118 to close the open end of the first housing 116, the intrusion of foreign objects into the first housing 116 from the outside can be prevented. Any rolling bearing, such as a roller bearing, can also be used instead of the first ball bearing 118.

[0145] The motor cage 141 extends radially outward toward the first ball bearing 118, and the electric motor 140 is mounted in such a manner that the rotation axis of the electric motor 140 is parallel to the axis L1.

[0146] A first driven pulley 151 is mounted on the end of a cylindrical shaft portion 112a that protrudes from the driven side opening 141a formed in the motor retainer 141, and rotates integrally with the cylindrical shaft portion 112a.

[0147] Furthermore, a first drive pulley 152 is mounted at the end of the rotating shaft 140a of the electric motor 140, which protrudes from the driven side opening 141b formed in the motor holder 141, and rotates integrally with the rotating shaft 140a. A first belt 153 is wound between the first driven pulley 151 and the first drive pulley 152. Therefore, the rotational force of the rotating shaft 140a is transmitted to the cylindrical shaft portion 112a, i.e., the lead screw shaft 112, via the first drive pulley 152, the first belt 153, and the first driven pulley 151.

[0148] The lead screw shaft 112 is inserted into the inner side of the nut 113 disposed inside the first housing 116 and is coaxially disposed with the nut 113. In the first ball screw 111 of this embodiment, the nut 113 is used as a linear motion element. The relative rotation of the nut 113 with respect to the first housing 116 is prevented by an anti-rotation device 117. The anti-rotation device 117 consists of a pin 117a protruding from the outer periphery of the first housing 116 toward the inner periphery and a straight groove 115b formed on the outer periphery of the first piston 115 parallel to the axis L1. After the first piston 115 is disposed in the first housing 116, the pin 117a can be inserted into the hole of the first housing 116 while keeping the phase aligned, so that its inner end engages with the straight groove 115b. Thus, the first piston 115 can move relative to the first housing 116 in the direction of the axis L1, but relative rotation is prevented. Furthermore, as described later, the nut 113 is fixed to the first piston 115 by the connecting member 119, thus preventing relative rotation of the nut 113 relative to the first housing 116.

[0149] The nut 113 has an outer flange 113a at its distal end opposite the inner flange 116b of the first housing 116. A connecting element 119, such as a bolt, for connection with the first piston 115 is installed on the outer flange 113a.

[0150] An internal thread groove 113b is formed on the inner circumference of the nut 113, and an external thread groove 112b is formed on the outer circumference of the lead screw shaft 112. The lead of the internal thread groove 113b and the external thread groove 112b is LD1.

[0151] A plurality of balls 114 are housed in a helical rolling groove formed between the internal thread groove 113b and the external thread groove 112b, in a manner that allows them to roll. When the lead screw 112 and the nut 113 rotate relative to each other, the balls 114 that reach one end of the rolling path return to the other end of the rolling path via a circulation path (not shown). Thus, the relative rotation of the lead screw 112 and the nut 113 continues. In this embodiment, the circulation method of the balls 114 can be a tubular type, a gyro type, an end guide type, an end cap type, etc., which are known technologies and therefore are omitted from description.

[0152] The first piston 115 has a bottomed cylindrical shape and is configured within the first cylinder chamber 116a to slide along its axial direction. The outer diameter of the outer flange 113a of the first piston 115 and the nut 113 is slightly smaller than the inner diameter of the first housing 116. The outer flange 113a of the nut 113 is connected to the open end of the first piston 115 via a connecting member 119, thereby allowing the first piston 115 and the nut 113 to move linearly together.

[0153] The lead screw 112 can enter the inner side of the first piston 115. A peripheral groove 115a is formed on the outer periphery near the bottom wall of the first piston 115. An annular first sealing member SL1' is disposed in the peripheral groove 115a to seal the outer periphery of the first piston 115 with the inner periphery of the first housing 116. The space enclosed by the end of the first piston 115 on the bottom wall side and the inner periphery and bottom wall of the first housing 116 constitutes a first variable volume space SP1 in the first cylinder chamber 116a that can store working oil. That is, a portion of the internal space of the first housing 116 becomes the first cylinder chamber 116a, and at least a portion of the first cylinder chamber 116a becomes the first variable volume space SP1 whose volume increases or decreases according to the displacement of the first piston 115.

[0154] An opening 116c is formed to connect the exterior of the first housing 116 to the first variable volume space SP1. A first pipe TB1 connected to the drive unit 200 is connected to the opening 116c.

[0155] (Second hydraulic generator)

[0156] The second hydraulic generating device 120 includes: a second ball screw 121; a second piston 125; a hollow second housing 126 having a second cylinder chamber 126a; and an anti-rotation device 27. The second ball screw 121 includes a screw shaft 122, a nut 123, and a plurality of balls 124. The second cylinder chamber 126a is positioned opposite the first cylinder chamber 116a, with its open ends facing each other. The second housing 126 is a bottomed cylindrical shape, with the open end side (…). Figure 4A The right side of the second housing 126 has an inner flange 126b. In addition, the inner flange 126b is formed separately from the second housing 126 and is installed at the open end of the second housing 126 by means of bolts or the like after the second piston 125 and nut 123 are inserted into the second housing 126.

[0157] The lead screw shaft 122 shares an axis L1 with the lead screw shaft 112 of the first ball screw 111, but is separate from and not connected to the lead screw shaft 112. The lead screw shaft 122 is rotatably supported on the second housing 126 via a second ball bearing 128. More specifically, the inner ring of the second ball bearing 128 is press-fitted into the cylindrical shaft portion 122a extending axially from the lead screw shaft 122. The outer ring of the second ball bearing 128 is fixed to the inner flange portion 126b formed at the end of the second housing 126 by a plate retainer 146 mounted on the inner flange portion 126b formed at the end of the second housing 126. By using the second ball bearing 128 to close the open end of the second housing 126, it is possible to prevent foreign objects from entering the second housing 126 from the outside. Any rolling bearing, such as a roller bearing, can also be used instead of the second ball bearing 128.

[0158] Plate cage 146 extends radially outward from the second ball bearing 128 in parallel with motor cage 141. The outer edges of motor cage 141 and plate cage 146 are connected to each other via frame-shaped spacer 148, which seals the space between motor cage 141 and plate cage 146 for the configuration of drive system 150.

[0159] A second driven pulley 154 is mounted on the end of the cylindrical shaft portion 122a that protrudes from the driven side opening 146a formed in the plate retainer 146, and rotates integrally with the cylindrical shaft portion 122a.

[0160] Furthermore, the end of the rotating shaft 140a of the electric motor 140, which enters the driven-side opening 146b formed in the plate holder 146, is supported by a ball bearing 147 (and a bearing built into the electric motor 140) within the driven-side opening 146b, allowing it to rotate. Additionally, a second drive pulley 155 is mounted between the first drive pulley 152 and the ball bearing 147 on the rotating shaft 140a, rotating integrally with the rotating shaft 140a.

[0161] A second belt 156 is wound between the second driven pulley 154 and the second drive pulley 155. Therefore, the rotational force of the rotating shaft 140a is transmitted to the cylindrical shaft portion 122a, i.e., the lead screw shaft 122, via the second drive pulley 155, the second belt 156, and the second driven pulley 154. In this embodiment, the drive system 150 is constituted by the first drive pulley 152, the first belt 153 and the first driven pulley 151, the second drive pulley 155, the second belt 156, and the second driven pulley 154. It should be noted that the pulley ratio of the first drive pulley 152 and the first driven pulley 151 is equal to the pulley ratio of the second drive pulley 155 and the second driven pulley 154.

[0162] The lead screw shaft 122 is inserted into the inner side of the nut 123 disposed inside the second housing 126 and is coaxially disposed with the nut 123. In the second ball screw 121 of this embodiment, the nut 123 is used as a linear motion element. The relative rotation of the nut 123 with respect to the second housing 126 is prevented by an anti-rotation device 127. The anti-rotation device 127 consists of a pin 127a protruding from the outer periphery of the second housing 126 toward the inner periphery and a straight groove 125b formed on the outer periphery of the second piston 125 parallel to the axis L1. After the second piston 125 is disposed in the second housing 126, the pin 127a can be inserted into the hole of the second housing 126 while keeping the phase aligned, so that its inner end engages with the straight groove 125b. Thus, the second piston 125 can move relative to the second housing 126 in the direction of the axis L1, but relative rotation is prevented. Furthermore, as described later, the nut 123 is fixed to the second piston 125 by the connecting member 129, thus preventing relative rotation of the nut 123 with respect to the second housing 126.

[0163] The nut 123 and the inner flange 126b of the second housing 126 are opposite each other and have an outer flange 123a at their distal ends. A connecting member 129, such as a bolt, for connection with the second piston 125 is installed on the outer flange 123a.

[0164] An internal thread groove 123b is formed on the inner circumference of the nut 123, and an external thread groove 122b is formed on the outer circumference of the lead screw shaft 122. The lead of both the internal thread groove 123b and the external thread groove 122b is LD2, which is different from the lead LD1 of the first ball screw 111. The relationship between the leads LD1 and LD2 will be described later.

[0165] A plurality of balls 124 are housed in a helical rolling groove formed between the internal thread groove 123b and the external thread groove 122b, in a manner that allows them to roll. When the lead screw 122 and the nut 123 rotate relative to each other, the balls 124 that reach one end of the rolling path return to the other end of the rolling path via a circulation path (not shown). Thus, the relative rotation of the lead screw 122 and the nut 123 continues. In this embodiment, the circulation method of the balls 124 can be a tubular type, a gyro type, an end guide type, an end cap type, etc., which are known technologies and therefore are omitted from description.

[0166] The second piston 125 has a bottomed cylindrical shape and is configured to slide along the axial direction within the second cylinder chamber 126a. The outer diameter of the outer flange 123a of the second piston 125 and the nut 123 is slightly smaller than the inner diameter of the second housing 126. The outer flange 123a of the nut 123 is connected to the open end of the second piston 125 via a connecting member 129, thereby allowing the second piston 125 and the nut 123 to move linearly together.

[0167] The lead screw 122 can enter the inner side of the second piston 125. A circumferential groove 125a is formed on the outer periphery near the bottom wall of the second piston 125. An annular second sealing member SL2' is disposed in the circumferential groove 125a to seal between the outer periphery of the second piston 125 and the inner periphery of the second housing 126. The space surrounded by the end of the bottom wall side of the second piston 125 and the inner periphery and bottom wall of the second housing 126 constitutes a second variable volume space SP2 in the second cylinder chamber 126a capable of storing working oil. That is, a portion of the internal space of the second housing 126 becomes the second cylinder chamber 126a, and at least a portion of the second cylinder chamber 126a becomes the second variable volume space SP2 whose volume increases or decreases according to the displacement of the second piston 125.

[0168] An opening 126c is formed to connect the exterior of the second housing 126 to the second variable volume space SP2. A second pipe TB2, which is connected to the drive unit 200, is connected to the opening 126c.

[0169] (Drive unit)

[0170] The drive unit 200 has a hollow cylindrical shell 201 closed at both ends, a solid cylindrical drive piston 202 capable of displacement along the axial direction within the shell 201, and a drive rod 203 connected to the drive piston 202. The axis of the shell 201 is defined as L2.

[0171] The outer diameter of the drive piston 202 is approximately equal to the inner diameter of the housing 201. A solid cylindrical drive rod 203 is connected to the center of the end face on one side of the drive piston 202 along the axial direction, passes through the second pressure chamber PC2 (described later) along the axis L2, and protrudes outward from the opening 201a formed on one end face of the housing 201. A mechanical element (not shown) driven by the drive device 200 is connected to the end of the drive rod 203.

[0172] The interior of the housing 201 is divided by the drive piston 202 into a second pressure chamber PC2 on the side of the drive rod 203 and a first pressure chamber PC1 on the side opposite to the drive rod 203. An opening 201b is formed on the peripheral wall of the housing 201 on the side of the first pressure chamber PC1, and the first pressure chamber PC1 is connected to the first variable volume space SP1 via a first pipe TB1 whose end is connected to the opening 201b.

[0173] Furthermore, an opening 201c is formed on the peripheral wall of the outer casing 201 on the side of the second pressure chamber PC2, and the second pressure chamber PC2 is connected to the second variable volume space SP2 via a second pipe TB2 whose end is connected to the opening 201c.

[0174] Here, the relationship between the lead LD1 of the first ball screw 111 and the lead LD2 of the second ball screw 121 will be explained. The drive piston 202 in the drive unit 200 is actuated by the pressure difference between the first pressure chamber PC1 and the second pressure chamber PC2 located on either side of it. Since the working oil is an incompressible fluid, for example, in order to move the drive piston 202 in the direction of the axis L2, the amount of working fluid entering or exiting the first pressure chamber PC1 with the displacement of the drive piston 202 needs to be equal to the amount of working fluid entering or exiting the second pressure chamber PC2.

[0175] However, a drive rod 203 is connected to one end face of the drive piston 202. Therefore, for each unit axial displacement of the drive piston 202, the amount of working fluid supplied and discharged relative to the first pressure chamber PC1 is greater than the amount of working fluid supplied and discharged from the second pressure chamber PC2. Specifically, when the inner diameter of the housing 201 is set as ΦA, the outer diameter of the drive rod 203 is set as ΦB, and the displacement of the drive piston 202 is set as X, the amount C of working fluid supplied and discharged relative to the first pressure chamber PC1 with the displacement of the drive piston 202 is C = Xπ(ΦA). 2 / 4 indicates that the amount D of the working fluid supplied and discharged relative to the second pressure chamber PC2 is given by D=Xπ((ΦA)). 2 -(ΦB) 2 ) / 4 represents this. Since CD = Xπ(ΦB) 2 / 4, therefore, as the displacement X of the drive piston 202 increases, the amount of working fluid entering or exiting the first pressure chamber PC1 needs to increase by Xπ (ΦB) relative to the amount of working fluid entering or exiting the second pressure chamber PC2. 2 / 4.

[0176] Therefore, in this embodiment, the lead LD1 of the first ball screw 111 is made larger than the lead LD2 of the second ball screw 121. Even when the rotation angles of the screw shaft 112 and the screw shaft 122 are equal, the axial displacement of the nut 113 is larger than the axial displacement of the nut 123.

[0177] Specifically, assuming that the inner diameter of the first cylinder chamber 116a is equal to the inner diameter of the second cylinder chamber 126a, and LD1:LD2=(ΦA) 2 :((ΦA) 2 -(ΦB) 2 The relationship between the guide is set.

[0178] <Operating Instructions for Hydraulic Working Devices>

[0179] Working oil is injected into the first variable volume space SP1, the second variable volume space SP2, the first pressure chamber PC1, the second pressure chamber PC2, the first piping TB1, and the second piping TB2. If the electric motor 140 rotates the rotating shaft 140a under the control of a control device (not shown), then via the drive system 150, the lead screw shafts 112 and 122 rotate in the same direction at the same angle. Thus, the nut 113, whose relative rotation with respect to the first housing 116 has been prevented by the anti-rotation device 117, moves together with the first piston 115 inside the first cylinder chamber 116a. Figure 4A The nut 123, moving linearly to the right and whose relative rotation with respect to the second housing 126 is prevented by the anti-rotation device 127, moves together with the second piston 125 inside the second cylinder chamber 126a. Figure 4A It moves in a straight line to the right.

[0180] As the first piston 115 moves toward the bottom wall of the first housing 116, the volume of the first variable volume space SP1 decreases. Therefore, a predetermined amount of working oil in the first variable volume space SP1 is discharged through the opening 116c and pumped into the first pressure chamber PC1 of the drive unit 200 via the first pipe TB1. Conversely, as the second piston 125 moves away from the bottom wall of the second housing 126, the volume of the second variable volume space SP2 increases. Therefore, the predetermined amount of working oil in the second pressure chamber PC2 of the drive unit 200 is drawn into the second variable volume space SP2 via the second pipe TB2. Thus, the drive piston 202 of the drive unit 200... Figure 4A The displacement to the left enables the drive rod 203 to perform work.

[0181] According to this embodiment, the lead LD1 of the first ball screw 111 is made larger than the lead LD2 of the second ball screw 121 by a predetermined value. Therefore, the amount of working oil pumped from the first variable volume space SP1 to the first pressure chamber PC1 is more than the amount of working oil discharged from the second pressure chamber PC2 to the second variable volume space SP2 by a predetermined amount, thereby ensuring the smooth operation of the drive device 200.

[0182] Conversely, when the electric motor 140 reverses the rotation shaft 140a according to the control from a control device (not shown), the lead screw shafts 112 and 122 rotate in the opposite direction at the same angle via the drive system 150. Thus, the nut 113 and the first piston 115 move together... Figure 4A The nut 123 moves linearly to the left, and the second piston 125 moves together with it. Figure 4AThe piston moves linearly to the left. As a result, the working oil in the first pressure chamber PC1 of the drive unit 200 is drawn in a predetermined amount through the first pipe TB1 to the first variable volume space SP1, and the working oil in the second variable volume space SP2 is pumped in the predetermined amount through the second pipe TB2 to the second pressure chamber PC2. Therefore, the drive piston 202 of the drive unit 200 moves in a straight line to the left. Figure 4A It shifts to the right and is pulled into the outer shell 201.

[0183] According to this embodiment, the first ball screw 111 of the first hydraulic generator 110 and the second ball screw 121 of the second hydraulic generator 120 can be driven simultaneously by the output of a single motor 400 to make the drive device 200 operate, thus reducing the number of parts and eliminating the need for complex control.

[0184] In addition to using pulleys and belts as the drive system 150, synchronous belts, timing chains, gear systems that mesh multiple gears, etc., can also be used. However, using pulleys and belts as the drive system 150 has the following advantages: when the amount of working oil supplied from the hydraulic generator 100 deviates due to the backlash of the ball screw, etc., this deviation can be absorbed by the slippage between the pulleys and the belt.

[0185] The hydraulic generating device of this embodiment (and the embodiments described below) is preferably used for driving hydraulic cylinders, and is particularly suitable for hydraulic cylinders with low oil volume and short stroke. In hydraulic devices that use hydraulic generating units based on conventional hydraulic pumps, devices such as valves for hydraulic switching and pressure regulating valves for adjusting the cylinder's operating speed and hydraulic pressure are required. In contrast, the hydraulic generating device of this embodiment (and the embodiments described below) allows for easy modification of the piston's movement speed and stroke. The speed and pressure of the hydraulic cylinder can be adjusted by changing the piston stroke of the hydraulic generating device, thus simplifying the component structure of the hydraulic device.

[0186] The screw shafts 112 and 122 of the ball screws 111 and 121 used in the hydraulic generating device of this embodiment (and the embodiments described later) may also be formed into a hollow shape in order to shorten the time from the start of the action to the generation of hydraulic pressure (based on the reduction of inertia due to lightweight).

[0187] In this embodiment (and the embodiments described later), single-row deep groove ball bearings 118 and 128 are used to support the lead screw shafts 112 and 122. However, the number and arrangement of bearings can be appropriately changed as long as they can support the axial and radial loads of the lead screw shafts 112 and 122. For example, two angular contact ball bearings can be used in a face-to-face or back-to-back configuration. Alternatively, two tapered roller bearings can be used in a face-to-face or back-to-back configuration.

[0188] (The hydraulic working device of the first modification)

[0189] Figure 4B This is an axial sectional view of the hydraulic generating device of the first variation of the first embodiment. This variation is similar to... Figure 4A The difference in this embodiment lies in that a shallow peripheral groove 115e is formed on the outer peripheral surface between the peripheral groove 115a and the straight groove 115b of the first piston 115', and a sliding bearing PB1 is disposed within the peripheral groove 115e. Similarly, a shallow peripheral groove 125e is formed on the outer peripheral surface between the peripheral groove 125a and the straight groove 125b of the second piston 125', and a sliding bearing PB2 is disposed within the peripheral groove 125e. The structure otherwise is the same as in the first embodiment, and therefore, a repetition of the description is omitted.

[0190] The sliding bearing PB1 is a thin-walled cylindrical component installed in the circumferential groove 115e formed on the outer circumferential surface of the first piston 115' and arranged to slide in contact with the inner circumferential surface of the first housing 116, thereby achieving low-friction sliding. By providing the sliding bearing PB1, the direct sliding between the outer circumferential surface of the first piston 115' and the inner circumferential surface of the first housing 116 is prevented from causing wear on both surfaces.

[0191] The sliding bearing PB2 is a thin-walled cylindrical component installed in the circumferential groove 125e formed on the outer circumferential surface of the second piston 125' and arranged to slide in contact with the inner circumferential surface of the second housing 126, thereby achieving low-friction sliding. By providing the sliding bearing PB2, the direct sliding between the outer circumferential surface of the second piston 125' and the inner circumferential surface of the second housing 126 is prevented from causing wear on both surfaces.

[0192] The sliding bearings PB1 and PB2 can be made of metal or resin materials that are softer and have good sliding properties than the piston and housing. As metal materials, copper alloys such as brass, aluminum alloys, and white metals can be used. As resin materials, PTFE, epoxy resin, polyacetal, nylon, polyethylene, and phenolic resin can be used. The sliding bearings PB1 and PB2 are preferably installed near the variable volume spaces SP1 and SP2 of the piston. Alternatively, the sliding bearings PB1 and PB2 can be configured to be installed in multiple peripheral grooves formed separately along the axial direction of the piston.

[0193] (The hydraulic working device of the second variation)

[0194] Figure 4C This is an axial sectional view of the hydraulic generating device in a second variation of the first embodiment. Figure 4AIn this embodiment, to drive the multi-body hydraulic cylinder, the driving force of an electric motor 140 is distributed and supplied to the first hydraulic generator 110 and the second hydraulic generator 120. Therefore, based on the difference in the cross-sectional area of ​​the second pressure chamber PC2 on the drive rod 203 side of the drive device 200 and the first pressure chamber PC1 on the opposite side of the rod in the orthogonal direction, the lead LD1 of the first hydraulic generator 110 and the lead LD2 of the second hydraulic generator 120 are different.

[0195] In contrast, in this modified example, instead of making the lead LD1 of the first hydraulic generating device 110' (the screw shaft 112' and nut 113' of the first ball screw 111') equal to the lead LD2 of the second hydraulic generating device 120' (the screw shaft 122' and nut 123' of the second ball screw 121'), the pulley ratio of the second drive pulley 155 and the second driven pulley 154' is different from the pulley ratio of the first drive pulley 152 and the first driven pulley 151' of the drive system 150' (by increasing the specified value) based on the difference in the cross-sectional area in the orthogonal direction of the aforementioned axes. Other than this, the structure is the same as in the first embodiment, therefore, repeated descriptions are omitted.

[0196] In addition, Figure 4C Only the diameter of the driven pulley is changed, but it is also possible to make the diameters of one driven pulley and the driving pulley different from the diameters of the other driven pulley and the driving pulley. Alternatively, the first and second modifications can be combined.

[0197] (Hydraulic working device according to the second embodiment)

[0198] Figure 5A This is an axial sectional view of the hydraulic working device according to the second embodiment.

[0199] The hydraulic working device of this embodiment includes a hydraulic generating device 100A and a drive device 200. The hydraulic generating device 100A includes a first hydraulic generating device 110A, a second hydraulic generating device 120A, an electric motor 140, and a drive system 150 that transmits the rotational force of the electric motor 140 to the first hydraulic generating device 110A and the second hydraulic generating device 120A. The first hydraulic generating device 110A and the second hydraulic generating device 120A share a common axis L1. Therefore, a compact hydraulic working device can be provided.

[0200] In this embodiment, the first hydraulic generating device 110A and the second hydraulic generating device 120A of the hydraulic generating device 100A differ from those in the first embodiment described above. Therefore, the electric motor 140, drive system 150, and drive device 200, which are common to the first embodiment, are labeled with the same reference numerals, and repeated descriptions are omitted. Furthermore, in the first hydraulic generating device 110A and the second hydraulic generating device 120A, parts with the same basic structure are also labeled with the same reference numerals, and repeated descriptions are omitted.

[0201] (First hydraulic generating device)

[0202] The first hydraulic generating device 110A includes a first ball screw 111A, a first piston 115A, a bottomed cylindrical hollow first housing 116A having a first cylinder chamber 116Aa, and an anti-rotation device 117. The first ball screw 111A has a screw shaft 112, a nut 113, and a plurality of balls 114. In this embodiment, the first housing 116A is a bottomed cylindrical shape, and an expanded-diameter cylindrical portion 116Af having the first cylinder chamber 116Aa and a reduced-diameter cylindrical portion 16Ae having an inner diameter smaller than the expanded-diameter cylindrical portion 116Af are arranged axially. An inner flange portion 116b is disposed adjacent to the expanded-diameter cylindrical portion 116Af at the open end. In addition, the inner flange portion 116b is formed separately from the first housing 116A, and after the first piston 115A and the nut 113 are inserted into the first housing 116A, it is mounted to the open end of the first housing 116A by means of bolts or the like.

[0203] The lead screw 112 is rotatably supported on the first housing 116A via a first ball bearing 118. More specifically, the inner ring of the first ball bearing 118 is press-fitted into the cylindrical shaft portion 112a extending axially from the lead screw 112, and the outer ring of the first ball bearing 118 is fixed to the inner flange portion 116b formed at the end of the first housing 116A by a motor cage 141. By sealing the open end of the first housing 116A with the first ball bearing 118, the intrusion of foreign objects into the first housing 116A from the outside can be prevented. Any rolling bearing, such as a roller bearing, can also be used instead of the first ball bearing 118.

[0204] The motor cage 141 extends radially outward toward the first ball bearing 118, and the electric motor 140 is mounted such that the rotation axis of the electric motor 140 is parallel to the axis L1. The rotational force of the rotation axis 140a of the electric motor 140 is transmitted to the lead screw 112 via the drive system 150.

[0205] The lead screw 112 is inserted into the inner side of the nut 113 disposed inside the first housing 116A and is coaxially disposed with the nut 113. Relative rotation of the nut 113 relative to the first housing 116A is prevented by an anti-rotation device 117. The anti-rotation device 117 consists of a pin 117a protruding from the outer periphery of the first housing 116A toward the inner periphery and a straight groove 115b formed on the outer periphery of the first piston 115A parallel to the axis L. After the first piston 115A is disposed inside the first housing 116A, the pin 117a can be inserted into the hole of the first housing 116A while maintaining phase alignment, so that its inner end engages with the straight groove 115b. Thus, the first piston 115A can move relative to the first housing 116A in the direction of the axis L, but relative rotation is prevented. Furthermore, as described later, the nut 113 is fixed to the first piston 115A by a connecting member 119, therefore relative rotation of the nut 113 relative to the first housing 116A is prevented.

[0206] The nut 113 has an outer flange 113a near its end opposite the inner flange 116b of the first housing 116A. A connecting element 119, such as a bolt, for connection with the first piston 115A is installed on the outer flange 113a.

[0207] An internal thread groove 113b is formed on the inner circumference of the nut 113, and an external thread groove 112b is formed on the outer circumference of the lead screw 112. A plurality of balls 114 are housed in a helical rolling groove formed between the internal thread groove 113b and the external thread groove 112b, allowing them to roll. When the lead screw 112 and the nut 113 rotate relative to each other, the balls 114 that reach one end of the rolling path return to the other end of the rolling path via a circulation path (not shown). This continues the relative rotation of the lead screw 112 and the nut 113. In this embodiment, the circulation method for the balls 114 can also be a tubular type, a gyroscope type, an end-guided type, or an end-cap type.

[0208] The first piston 115A is formed by continuously arranging a thin-walled cylindrical portion 115Ac and a thick-walled cylindrical portion 115Ab. The thick-walled cylindrical portion 115Ab is thicker than the thin-walled cylindrical portion 115Ac and is continuously arranged coaxially with the thin-walled cylindrical portion 115Ac. The thick-walled cylindrical portion 115Ab is disposed radially inside the expanded-diameter cylindrical portion 116Af, and its outer diameter is the same as or slightly smaller than the inner diameter of the expanded-diameter cylindrical portion 116Af. In addition, the outer diameter of the outer flange portion 113a of the nut 113 is the same as or slightly smaller than the inner diameter of the expanded-diameter cylindrical portion 116Af. A portion of the thin-walled cylindrical portion 115Ac is disposed radially inside the reduced-diameter cylindrical portion 116Ae, and its outer diameter is the same as or slightly smaller than the inner diameter of the reduced-diameter cylindrical portion 116Ae.

[0209] The first piston 115A abuts the thick-walled cylindrical portion 115Ab with the outer flange portion 113a, and the outer periphery of the first piston 115A is fitted into the inner periphery of the expanded-diameter cylindrical portion 116Af in a relatively movable manner. In addition, the inner peripheries of the thin-walled cylindrical portion 115Ac and the thick-walled cylindrical portion 115Ab are fitted into the outer periphery of the nut 113 in a non-rotatable manner, and are configured to slide along the axial direction together with the nut 113 in the first cylinder chamber 116Aa.

[0210] A peripheral groove 115Aa is formed on the outer periphery near the end of the thick-walled cylindrical portion 115Ab, which is close to the thin-walled cylindrical portion 115Ac. An annular central sealing member SL3 is disposed within the peripheral groove 115Aa. The central sealing member SL3 seals the outer periphery of the thick-walled cylindrical portion 115Ab with the inner periphery of the expanded-diameter cylindrical portion 116Af of the first housing 116A. On the other hand, a peripheral groove 116Ad is formed on the inner periphery near the end of the reduced-diameter cylindrical portion 116Ae, which is close to the expanded-diameter cylindrical portion 116Af of the first housing 116A. An annular outer sealing member SL4 is disposed within the peripheral groove 116Ad. The outer sealing member SL4 seals the outer periphery of the thin-walled cylindrical portion 115Ac of the first piston 115A with the inner periphery of the reduced-diameter cylindrical portion 116Ae of the first housing 116A. Alternatively, a sealing groove can be provided on the outer periphery of the first piston 115A to accommodate a second sealing member.

[0211] Between the axially separated thick-walled cylindrical portion 115Ab and the reduced-diameter cylindrical portion 116Ae, the space enclosed by the outer periphery of the first piston 115A (thin-walled cylindrical portion 115Ac) and the inner periphery of the first housing 116A (expanded-diameter cylindrical portion 116Af) constitutes a first variable-volume space SP1 in the first cylinder chamber 116Aa capable of storing working oil. That is, a portion of the internal space of the first housing 116A becomes the first cylinder chamber 116Aa, and at least a portion of the first cylinder chamber 116Aa becomes the first variable-volume space SP1, whose volume increases or decreases according to the displacement of the first piston 115A. Therefore, the overall length of the first hydraulic generating device 110A can be shortened.

[0212] The first piston 115A has: a clearance groove 115Ag formed on the inner circumference of the thin-walled cylindrical portion 115Ac and the thick-walled cylindrical portion 115Ab and extending straight along the axis L1; and a connecting hole 115Ah connecting the inner and outer circumferences of the thick-walled cylindrical portion 115Ab. One end of the clearance groove 115Ag opens into the space inside the reduced-diameter cylindrical portion 116Ae, and the other end of the clearance groove 115Ag communicates with the inner end of the connecting hole 115Ah. The clearance groove 115Ag and the connecting hole 115Ah constitute an air passage.

[0213] Near the reduced-diameter cylindrical portion 116Ae of the expanded-diameter cylindrical portion 116Af, an opening 116c is formed to connect the exterior of the first housing 116A with the first variable volume space SP1. A first piping TB1 connected to the drive unit 200 is connected to the opening 116c.

[0214] (Second hydraulic generator)

[0215] The second hydraulic generating device 120A includes a second ball screw 121A, a second piston 125A, a bottomed cylindrical hollow second housing 126A with a second cylinder chamber 126Aa, and an anti-rotation device 127. The second ball screw 121A has a screw shaft 122, a nut 123, and a plurality of balls 124. The second cylinder chamber 126Aa is arranged opposite to the first cylinder chamber 116Aa, with their open ends facing each other. In this embodiment, the second housing 126A is a bottomed cylindrical shape, and is formed by axially arranging an expanded-diameter cylindrical portion 126Af where the second cylinder chamber 126Aa is formed and a reduced-diameter cylindrical portion 126Ae with an inner diameter smaller than that of the expanded-diameter cylindrical portion 126Af. The inner flange portion 126b is disposed adjacent to the expanded-diameter cylindrical portion 126Af at the open end. In addition, the inner flange portion 126b is formed separately from the second housing 126A. After the second piston 125A and nut 123 are inserted into the second housing 126A, they are installed at the open end of the second housing 126A by means of bolts or the like.

[0216] The lead screw shaft 122 shares an axis L1 with the lead screw shaft 112 of the first ball screw 111A, but is separate from and not connected to the lead screw shaft 112. The lead screw shaft 122 is rotatably supported on the second housing 126A via a second ball bearing 128. More specifically, the inner ring of the second ball bearing 128 is press-fitted into the cylindrical shaft portion 122a extending axially from the lead screw shaft 122, and the outer ring of the second ball bearing 128 is fixed to the inner flange portion 126b by a plate retainer 146 mounted on the inner flange portion 126b formed at the end of the second housing 126A. By sealing the open end of the second housing 126A with the second ball bearing 128, foreign objects can be prevented from entering the second housing 126A from the outside. Any rolling bearing, such as a roller bearing, can also be used instead of the second ball bearing 128.

[0217] Plate cage 146 extends radially outward from the second ball bearing 128, parallel to motor cage 141. The outer edges of motor cage 141 and plate cage 146 are connected to each other via a frame-like spacer 148, which seals the space between motor cage 141 and plate cage 146 containing the drive system 150. The rotational force of the rotating shaft 140a of the electric motor 140 is transmitted to the lead screw shaft 122 via the drive system 150.

[0218] The lead screw shaft 122 is inserted into the inner side of the nut 123 disposed inside the second housing 126A and is coaxially arranged with the nut 123. Relative rotation of the nut 123 relative to the second housing 126A is prevented by an anti-rotation device 127. The anti-rotation device 127 consists of a pin 127a protruding from the outer periphery of the second housing 126A toward the inner periphery and a straight groove 125b formed on the outer periphery of the second piston 125A parallel to the axis L. After the second piston 125A is disposed within the second housing 126A, the pin 127a can be inserted into the hole of the second housing 126A while maintaining phase alignment, so that its inner end engages with the straight groove 125b. Thus, the second piston 125A can move relative to the second housing 126A in the direction of the axis L, but relative rotation is prevented. Furthermore, as described later, the nut 123 is fixed to the second piston 125A by a connecting member 129, therefore relative rotation of the nut 123 relative to the second housing 126A is prevented.

[0219] The nut 123 has an outer flange 123a near its end opposite the inner flange 126b of the second housing 126A. A connecting element 129, such as a bolt, for connection with the second piston 125A is installed on the outer flange 123a.

[0220] An internal threaded groove 123b is formed on the inner circumference of the nut 123, and an external threaded groove 122b is formed on the outer circumference of the lead screw 122. A plurality of balls 124 are housed in a helical rolling groove formed between the internal and external threaded grooves 123b and 122b, allowing them to roll. When the lead screw 122 and the nut 123 rotate relative to each other, the balls 124 that reach one end of the rolling path return to the other end via a circulation path (not shown). This continues the relative rotation of the lead screw 122 and the nut 123. In this embodiment, the circulation method for the balls 124 can also be a tubular type, a gyroscope type, an end-guided type, or an end-cap type.

[0221] The second piston 125A is formed by continuously arranging a thin-walled cylindrical portion 125Ac and a thick-walled cylindrical portion 125Ab. The thick-walled cylindrical portion 125Ab is thicker than the thin-walled cylindrical portion 125Ac and is continuously arranged coaxially with the thin-walled cylindrical portion 125Ac. The thick-walled cylindrical portion 125Ab is disposed radially inside the expanded-diameter cylindrical portion 126Af, and its outer diameter is the same as or slightly smaller than the inner diameter of the expanded-diameter cylindrical portion 126Af. In addition, the outer diameter of the outer flange portion 123a of the nut 123 is the same as or slightly smaller than the inner diameter of the expanded-diameter cylindrical portion 126Af. A portion of the thin-walled cylindrical portion 125Ac is disposed radially inside the reduced-diameter cylindrical portion 126Ae, and its outer diameter is the same as or slightly smaller than the inner diameter of the reduced-diameter cylindrical portion 126Ae.

[0222] The second piston 125A abuts the thick-walled cylindrical portion 125Ab against the outer flange portion 123a, and the outer periphery of the second piston 125A is fitted into the inner periphery of the expanded-diameter cylindrical portion 126Af in a relatively movable manner. Furthermore, the inner peripheries of the thin-walled cylindrical portion 125Ac and the thick-walled cylindrical portion 125Ab are fitted into the outer periphery of the nut 123 in a non-rotatable manner, and are configured to slide along the axial direction together with the nut 123 within the second cylinder chamber 126Aa. The end portion of the second piston 125A on the reduced-diameter cylindrical portion 126Ae side and the end portion of the nut 123 on the reduced-diameter cylindrical portion 126Ae side are preferably axially aligned and coplanar.

[0223] A peripheral groove 125Aa is formed on the outer periphery near the end of the thick-walled cylindrical portion 125Ab, which is close to the thin-walled cylindrical portion 125Ac. An annular central sealing member SL5 is disposed within the peripheral groove 125Aa. The central sealing member SL5 seals the outer periphery of the thick-walled cylindrical portion 125Ab with the inner periphery of the expanded-diameter cylindrical portion 126Af of the second housing 126A. On the other hand, a peripheral groove 126Ad is formed on the inner periphery near the end of the reduced-diameter cylindrical portion 126Ae, which is close to the expanded-diameter cylindrical portion 126Af of the second housing 126A. An annular outer sealing member SL6 is disposed within the peripheral groove 126Ad. The outer sealing member SL6 seals the outer periphery of the thin-walled cylindrical portion 125Ac of the second piston 125A with the inner periphery of the reduced-diameter cylindrical portion 126Ae of the second housing 126A. Alternatively, a sealing groove can be provided on the outer periphery of the second piston 125A to accommodate the second sealing member.

[0224] Between the axially separated thick-walled cylindrical portion 125Ab and the reduced-diameter cylindrical portion 126Ae, the space enclosed by the outer periphery of the second piston 125A (thin-walled cylindrical portion 125Ac) and the inner periphery of the second housing 126A (expanded-diameter cylindrical portion 126Af) constitutes a second variable-volume space SP2 in the second cylinder chamber 126Aa capable of storing working oil. That is, a portion of the internal space of the second housing 126A becomes the second cylinder chamber 126Aa, and at least a portion of the second cylinder chamber 126Aa becomes the second variable-volume space SP2, whose volume increases or decreases according to the displacement of the second piston 125A. Therefore, the overall length of the second hydraulic generator 120A can be shortened.

[0225] The second piston 125A has: a clearance groove 125Ag formed on the inner circumference of the thin-walled cylindrical portion 125Ac and the thick-walled cylindrical portion 125Ab and extending straight along the axis L; and a connecting hole 125Ah connecting the inner and outer circumferences of the thick-walled cylindrical portion 125Ab. One end of the clearance groove 125Ag opens into the space inside the reduced-diameter cylindrical portion 126Ae, and the other end of the clearance groove 125Ag communicates with the inner end of the connecting hole 125Ah. The clearance groove 125Ag and the connecting hole 125Ah constitute an air passage.

[0226] Near the reduced-diameter cylindrical portion 126Ae of the expanded-diameter cylindrical portion 126Af, an opening 126c is formed to connect the exterior of the second housing 126A with the second variable volume space SP2. A second pipe TB2 connected to the drive unit 200 is connected to the opening 126c.

[0227] <Operating Instructions for Hydraulic Working Devices>

[0228] Working oil is injected into the first variable volume space SP1, the second variable volume space SP2, the first pressure chamber PC1, the second pressure chamber PC2, the first piping TB1, and the second piping TB2. If the electric motor 140 rotates the rotating shaft 140a under the control of a control device (not shown), then via the drive system 150, the lead screw shafts 112 and 122 rotate in the same direction at the same angle. Thus, the nut 113, whose relative rotation with respect to the first housing 116A is prevented by the anti-rotation device 117, moves together with the first piston 115A inside the first cylinder chamber 116Aa. Figure 5A The nut 123, which moves linearly to the right and whose relative rotation with respect to the second housing 126A has been prevented by the anti-rotation device 127, moves together with the second piston 125A inside the second cylinder chamber 126Aa. Figure 5A It moves in a straight line to the right.

[0229] At this time, the thick-walled cylindrical portion 115Ab of the first piston 115A slides relative to the expanding cylindrical portion 116Af, and the thin-walled cylindrical portion 115Ac slides relative to the contracting cylindrical portion 116Ae. Either side can also slide relative to the other. Through the movement of the first piston 115A, the thick-walled cylindrical portion 115Ab displaces towards the stepped portions of the expanding and contracting cylindrical portions 116Af and 116Ae, thereby reducing the volume of the first variable volume space SP1. The working oil in the first variable volume space SP1 is then pumped to the first pressure chamber PC1 of the drive unit 200 via the first pipe TB1.

[0230] Simultaneously, the thick-walled cylindrical portion 125Ab of the second piston 125A slides relative to the expanding cylindrical portion 126Af, and the thin-walled cylindrical portion 125Ac slides relative to the contracting cylindrical portion 126Ae. Either can also slide relative to the other. Through the movement of the second piston 125A, the thick-walled cylindrical portion 125Ab is displaced by separating from the stepped portion of the expanding cylindrical portion 126Af and the contracting cylindrical portion 126Ae, thereby increasing the volume of the second variable volume space SP2. Therefore, the working oil in the first pressure chamber PC1 of the drive device 200 is drawn into the second variable volume space SP2 via the second pipe TB2. Thus, the drive piston 202 of the drive device 200... Figure 5A The displacement to the left enables the drive rod 203 to perform work.

[0231] Furthermore, in this embodiment, when the first piston 115A and the second piston 125A generate a stroke along the axial direction, the air in the first air chamber AP1 (within the reduced diameter cylindrical portion 116Ae) disposed between the first piston 115A and the bottom wall of the first housing 116A and the second air chamber AP2 (within the reduced diameter cylindrical portion 126Ae) disposed between the second piston 125A and the bottom wall of the second housing 126A is pressurized or depressurized. Therefore, the treatment of the air in the first air chamber AP1 and the second air chamber AP2 becomes a problem.

[0232] According to this embodiment, for example, when the air in the first air chamber AP1 is pressurized, the air moves to one side through the gap between the inner periphery of the first housing 116A and the outer periphery of the thick-walled cylindrical portion 115Ab and the outer periphery of the outer flange portion 113a via the clearance groove 115Ag and the connecting hole 115Ah. Conversely, when the air in the first air chamber AP1 is depressurized, the air on the ball bearing 118 side returns to the first air chamber AP1 via the clearance groove 115Ag and the connecting hole 115Ah. Therefore, when the first piston 115A travels axially, the resistance generated by the pressurization or depressurization of the air in the first air chamber AP1 can be suppressed, allowing the first piston 115A to operate smoothly.

[0233] Furthermore, for example, when the air in the second air chamber AP2 is pressurized, the air moves towards the second ball bearing 128 through the gap between the inner circumference of the second housing 126A and the outer circumference of the thick-walled cylindrical portion 125Ab and the outer circumference of the outer flange portion 123a via the clearance groove 125Ag and the connecting hole 125Ah. Conversely, when the air in the second air chamber AP2 is depressurized, the air on the ball bearing 128 side returns to the second air chamber AP2 via the clearance groove 125Ag and the connecting hole 125Ah. Therefore, when the second piston 125A travels axially, the resistance generated by the pressurization or depressurization of the air in the second air chamber AP2 can be suppressed, allowing the second piston 125A to operate smoothly.

[0234] In this embodiment, similar to the first embodiment, the lead of the first ball screw 111A is made larger than the lead of the second ball screw 121A by a predetermined value. Therefore, the amount of working oil pumped from the first variable volume space SP1 to the first pressure chamber PC1 is more than the amount of working oil discharged from the second pressure chamber PC2 to the second variable volume space SP2 by a predetermined amount, thereby ensuring the smooth operation of the drive device 200.

[0235] Conversely, when the electric motor 140 reverses the rotation shaft 140a according to the control from a control device (not shown), the lead screw shafts 112 and 122 rotate in the opposite direction at the same angle via the drive system 150. Thus, the nut 113, together with the first piston 115A, moves... Figure 5AIt moves in a straight line to the left. Additionally, nut 123 and the second piston 125A move together... Figure 5A The piston moves linearly to the left. As a result, the working oil in the first pressure chamber PC1 of the drive unit 200 is drawn in a predetermined amount through the first pipe TB1 to the first variable volume space SP1, and the working oil in the second variable volume space SP2 is pumped in the predetermined amount through the second pipe TB2 to the second pressure chamber PC2. Therefore, the drive piston 202 of the drive unit 200 moves in a straight line to the left. Figure 5A It shifts to the right and is pulled into the outer shell 201.

[0236] (The hydraulic working device of the first modification)

[0237] Figure 5B This is an axial sectional view of the hydraulic generating device of the first variation of the second embodiment. This variation is similar to... Figure 5A The difference in this embodiment lies in that a shallow peripheral groove 115Ae is formed on the outer peripheral surface between the peripheral groove 115a and the straight groove 115b of the first piston 115A', and a sliding bearing PB1 is disposed within the peripheral groove 115Ae. Similarly, a shallow peripheral groove 125Ae is formed on the outer peripheral surface between the peripheral groove 125Aa and the straight groove 125b of the second piston 125A', and a sliding bearing PB2 is disposed within the peripheral groove 125Ae. The structure is otherwise the same as in the second embodiment, and therefore, a repetition of the description is omitted.

[0238] The sliding bearing PB1 is a thin-walled cylindrical component installed in the circumferential groove 115Ae formed on the outer circumferential surface of the first piston 115A' and arranged to slide in contact with the inner circumferential surface of the first housing 116A, thereby achieving low-friction sliding. By providing the sliding bearing PB1, the outer circumferential surface of the first piston 115A' and the inner circumferential surface of the first housing 116A are prevented from sliding directly and causing wear between them.

[0239] The sliding bearing PB2 is a thin-walled cylindrical component installed in the circumferential groove 125Ae formed on the outer circumferential surface of the second piston 125A' and arranged to slide in contact with the inner circumferential surface of the second housing 126A, thereby achieving low-friction sliding. By providing the sliding bearing PB2, the direct sliding between the outer circumferential surface of the second piston 125A' and the inner circumferential surface of the second housing 126A is prevented from causing wear on both surfaces. The materials of the sliding bearings PB1 and PB2 are the same as those in the modified example of the first embodiment described above.

[0240] (The hydraulic working device of the second variation)

[0241] Figure 5C This is an axial sectional view of the hydraulic generating device of the second variation of the second embodiment. Figure 5AIn this embodiment, to drive the multi-body hydraulic cylinder, the driving force of an electric motor 140 is distributed and supplied to the first hydraulic generator 110A and the second hydraulic generator 120A. Therefore, based on the difference in the cross-sectional area of ​​the second pressure chamber PC2 on the drive rod 203 side of the drive device 200 and the first pressure chamber PC1 on the opposite side of the rod in the orthogonal direction, the thread lead of the first hydraulic generator 110A is different from that of the second hydraulic generator 120A.

[0242] In contrast, in this modified example, instead of making the thread lead of the first hydraulic generating device 110A' (the screw shaft 112' and nut 113' of the first ball screw 111A') equal to that of the second hydraulic generating device 120A' (the screw shaft 122' and nut 123' of the second ball screw 121A'), the pulley ratio of the second drive pulley 155 and the second driven pulley 154' is different from the pulley ratio of the first drive pulley 152 and the first driven pulley 151' of the drive system 150' (by increasing the specified value) based on the difference in the cross-sectional area in the orthogonal direction of the aforementioned axes. Other than this, the structure is the same as in the second embodiment, and therefore, repeated descriptions are omitted.

[0243] In addition, Figure 5C Only the diameter of the driven pulley is changed, but it is also possible to make the diameters of one driven pulley and the driving pulley different from the diameters of the other driven pulley and the driving pulley. Alternatively, the first and second modifications can be combined.

[0244] Various embodiments have been described above with reference to the accompanying drawings, but the present invention is not limited to these examples. It will be apparent to those skilled in the art that various modifications or alterations will occur within the scope of the claims, and these modifications or alterations are also within the technical scope of the present invention. Furthermore, the constituent elements of the above embodiments can be combined arbitrarily without departing from the spirit of the invention.

[0245] It should be noted that this application is based on Japanese patent applications filed on November 6, 2023 (Japanese Patent Application No. 2023-189183) and November 6, 2023 (Japanese Patent Application No. 2023-189184), the contents of which are incorporated herein by reference.

[0246] Explanation of reference numerals in the attached figures

[0247] 1, 11, 21 Ball screw

[0248] 2.12 lead screw shaft

[0249] 3.13 Nuts

[0250] 5, 5', 15, 15' pistons

[0251] 6, 16 Shell

[0252] 7.17 Ball Bearings

[0253] 8, 18 bearing cage

[0254] 9 Connectors

[0255] 20 Anti-rotation device

[0256] 23, 23' Piston Nut

[0257] 100, 100A hydraulic generator

[0258] 110, 110A, 110', 110A' First hydraulic generating unit

[0259] 120, 120A, 120', 120A' Second hydraulic generating unit

[0260] 111, 111A, 111', 111A' First ball screw

[0261] 121, 121A, 121', 121A' Second ball screw

[0262] 112, 112' lead screw shaft

[0263] 113, 113' Nut

[0264] 114 Ball bearings

[0265] 115, 115A, 115', 115A' First Piston

[0266] 125, 125A, 125', 125A' Second Piston

[0267] 116, 116A First Shell

[0268] 126, 126A Second Shell

[0269] 117, 127 Anti-rotation devices

[0270] 118 and 128 ball bearings

[0271] 119, 129 Connectors

[0272] 150, 150' drive system

[0273] 200 drive unit

[0274] 202 Drive Piston

[0275] 203 Drive lever

[0276] PB sliding bearings

[0277] PB1 and PB2 sliding bearings

[0278] SL sealing components

[0279] SL1 First sealing component

[0280] SL2 Second Sealing Component

[0281] SL1' First sealing component

[0282] SL2' Second sealing component

[0283] SL3 middle side sealing component

[0284] SL4 outer sealing component

[0285] SL5 middle side sealing component

[0286] SL6 outer sealing component

[0287] SP Variable Volume Space

[0288] SP1 First Variable Volume Space

[0289] SP2 Second Variable Volume Space

Claims

1. A hydraulic generating device, characterized in that, have: A hollow housing having a cylinder chamber capable of being injected with working oil; A lead screw shaft having an external threaded groove; A nut, which is supported to be axially movable within the housing and has an internal threaded groove; Multiple balls are housed within a rolling path formed by opposing external and internal threaded grooves; as well as A piston, which is slidably disposed within the cylinder chamber and connected to the nut. By rotating the lead screw, the piston and the nut move axially together, thereby increasing or decreasing the volume of the space in the cylinder chamber that can store working oil.

2. The hydraulic generating device according to claim 1, characterized in that, A sealing component is disposed between the outer periphery of the piston and the inner periphery of the housing. The space enclosed by the inner periphery and bottom wall of the housing and the piston is the space in the cylinder chamber that can store working oil.

3. The hydraulic generating device according to claim 1, characterized in that, The housing has an expanded-diameter cylindrical portion and a reduced-diameter cylindrical portion with an inner diameter smaller than that of the expanded-diameter cylindrical portion. The piston, fitted onto the outer periphery of the nut, has: a thick-walled cylindrical portion disposed radially inside the expanded-diameter cylindrical portion; and a thin-walled cylindrical portion, at least a portion of which is disposed radially inside the reduced-diameter cylindrical portion. A first sealing member is disposed between the outer periphery of the thick-walled cylindrical portion and the inner periphery of the expanded-diameter cylindrical portion. A second sealing member is disposed between the outer periphery of the thin-walled cylindrical portion and the inner periphery of the reduced-diameter cylindrical portion. The space between the thick-walled cylindrical portion and the reduced-diameter cylindrical portion, and between the outer periphery of the thin-walled cylindrical portion and the inner periphery of the expanded-diameter cylindrical portion, is the space in the cylinder chamber capable of storing working oil.

4. The hydraulic generating device according to claim 3, characterized in that, The piston is provided with an air passage that connects an air chamber formed within the housing between the second sealing member and the bottom wall of the housing to the outside of the piston.

5. The hydraulic generating device according to claim 3, characterized in that, The piston and the nut are integrated.

6. The hydraulic generating device according to claim 1, characterized in that, The hydraulic generating device has an anti-rotation device to prevent relative rotation between the piston and the housing.

7. The hydraulic generating device according to claim 1, characterized in that, A sliding bearing is disposed between the piston and the housing.

8. The hydraulic generating device according to any one of claims 1 to 7, characterized in that, The housing is a bottomed cylindrical shape, and a bearing is provided at the open end of the housing to support the lead screw shaft so that it can rotate.

9. A hydraulic working device, characterized in that, Equipped with the hydraulic generating device, driving device, motor, and driving system as described in claim 1, The hydraulic generating device includes a first hydraulic generating device and a second hydraulic generating device. The first hydraulic generating device includes: A hollow first housing, the first housing having a first cylinder chamber capable of being injected with working oil; A first ball screw, comprising: a screw shaft having an external threaded groove; a nut having an internal threaded groove; and a plurality of balls capable of rolling along a rolling path between the external threaded groove and the internal threaded groove; and A first piston is slidably disposed within the first cylinder chamber and connected to a nut of the first ball screw. The second hydraulic generating device includes: A hollow second housing, the second housing having a second cylinder chamber capable of being injected with working oil; The second ball screw comprises: a screw shaft having an external threaded groove; a nut having an internal threaded groove; and a plurality of balls capable of rolling along a rolling path between the external threaded groove and the internal threaded groove. as well as The second piston is slidably disposed within the second cylinder chamber and connected to the nut of the second ball screw. The driving device has: A cylindrical outer shell; The first pressure chamber inside the outer casing is connected to the first cylinder chamber; The second pressure chamber inside the outer casing is connected to the second cylinder chamber; A drive piston that separates the first pressure chamber from the second pressure chamber; as well as A drive rod that extends axially from the drive piston via the second pressure chamber. The first ball screw and the second ball screw share a common axis, and the first cylinder chamber and the second cylinder chamber are arranged opposite each other. The rotational force of the motor is transmitted via the drive system to the screw shafts of the first and second ball screws, thereby enabling the nut and piston of the first ball screw and the nut and piston of the second ball screw to move in the same direction relative to the first and second cylinder chambers, respectively. The lead of the internal and external thread grooves of the first ball screw is smaller than the lead of the internal and external thread grooves of the second ball screw by a specified value.

10. A hydraulic working device, characterized in that, Equipped with the hydraulic generating device, driving device, motor, and driving system as described in claim 1, The hydraulic generating device includes a first hydraulic generating device and a second hydraulic generating device. The first hydraulic generating device includes: A hollow first housing, the first housing having a first cylinder chamber capable of injecting working oil; A first ball screw, comprising: a screw shaft having an external threaded groove; a nut having an internal threaded groove; and a plurality of balls capable of rolling along a rolling path between the external threaded groove and the internal threaded groove; and A first piston is slidably disposed within the first cylinder chamber and connected to a nut of the first ball screw. The second hydraulic generating device includes: A hollow second housing, the second housing having a second cylinder chamber capable of being injected with working oil; The second ball screw comprises: a screw shaft having an external threaded groove; a nut having an internal threaded groove; and a plurality of balls capable of rolling along a rolling path between the external threaded groove and the internal threaded groove. as well as The second piston is slidably disposed within the second cylinder chamber and connected to the nut of the second ball screw. The driving device has: A cylindrical outer shell; The first pressure chamber inside the outer casing is connected to the first cylinder chamber; The second pressure chamber inside the outer casing is connected to the second cylinder chamber; A drive piston that separates the first pressure chamber from the second pressure chamber; as well as A drive rod that extends axially from the drive piston via the second pressure chamber. The first ball screw and the second ball screw share a common axis, and the first cylinder chamber and the second cylinder chamber are arranged opposite each other. The rotational force of the motor is transmitted via the drive system to the screw shafts of the first and second ball screws, thereby enabling the nut and piston of the first ball screw and the nut and piston of the second ball screw to move in the same direction relative to the first and second cylinder chambers, respectively. The drive system includes: a first belt connecting a pulley to the rotating shaft of the motor and a pulley to the screw shaft of the first ball screw; and a second belt connecting a pulley to the rotating shaft of the motor and a pulley to the screw shaft of the second ball screw. The pulley ratio between the two pulleys engaged by the first belt is smaller than the pulley ratio between the two pulleys engaged by the second belt by a specified value.

11. The hydraulic working device according to claim 9 or 10, characterized in that, A first sealing component is disposed between the outer periphery of the first piston and the inner periphery of the first cylindrical shell with a bottom. The space enclosed by the inner periphery and bottom wall of the first housing and the first piston is the space in the first cylinder chamber capable of storing working oil. A second sealing component is disposed between the outer periphery of the second piston and the inner periphery of the bottomed cylindrical second housing. The space enclosed by the inner periphery and bottom wall of the second housing and the second piston is the space in the second cylinder chamber that can store working oil.

12. The hydraulic working device according to claim 9 or 10, characterized in that, The first housing is a bottomed cylindrical shape, having an expanded diameter cylindrical portion and a reduced diameter cylindrical portion with an inner diameter smaller than the expanded diameter cylindrical portion. The first piston, fitted onto the outer periphery of the nut of the first ball screw, has: a thick-walled cylindrical portion disposed radially inside the expanded-diameter cylindrical portion of the first housing; and a thin-walled cylindrical portion, at least a portion of which is disposed radially inside the reduced-diameter cylindrical portion. A center-side sealing component is disposed between the outer periphery of the thick-walled cylindrical portion and the inner periphery of the expanded-diameter cylindrical portion. An outer sealing member is disposed between the outer periphery of the thin-walled cylindrical portion and the inner periphery of the reduced-diameter cylindrical portion. The space between the thick-walled cylindrical portion and the reduced-diameter cylindrical portion, and between the outer periphery of the thin-walled cylindrical portion and the inner periphery of the expanded-diameter cylindrical portion, is the space in the first cylinder chamber capable of storing working oil.

13. The hydraulic working device according to claim 12, characterized in that, A first air chamber is provided between the first piston and the bottom wall of the first housing. The first piston is provided with an air passage that connects the first air chamber to the outside of the first piston.

14. The hydraulic working device according to claim 9 or 10, characterized in that, The second housing is a bottomed cylindrical shape, having an expanded diameter cylindrical section and a reduced diameter cylindrical section with an inner diameter smaller than the expanded diameter cylindrical section. The second piston, fitted onto the outer periphery of the nut of the second ball screw, has: a thick-walled cylindrical portion disposed radially inside the expanded-diameter cylindrical portion of the second housing; and a thin-walled cylindrical portion, at least a portion of which is disposed radially inside the reduced-diameter cylindrical portion. A center-side sealing component is disposed between the outer periphery of the thick-walled cylindrical portion and the inner periphery of the expanded-diameter cylindrical portion. An outer sealing member is disposed between the outer periphery of the thin-walled cylindrical portion and the inner periphery of the reduced-diameter cylindrical portion. The space between the thick-walled cylindrical portion and the reduced-diameter cylindrical portion, and between the outer periphery of the thin-walled cylindrical portion and the inner periphery of the expanded-diameter cylindrical portion, is the space in the second cylinder chamber capable of storing working oil.

15. The hydraulic working device according to claim 14, characterized in that, A second air chamber is provided between the second piston and the bottom wall of the second housing. The second piston is provided with an air passage that connects the second air chamber to the outside of the second piston.

16. The hydraulic working device according to claim 9 or 10, characterized in that, It has: an anti-rotation device that prevents relative rotation between the first piston and the first housing; and an anti-rotation device that prevents relative rotation between the second piston and the second housing.

17. The hydraulic working device according to claim 9 or 10, characterized in that, A sliding bearing is disposed between the first piston and the first housing, and a sliding bearing is disposed between the second piston and the second housing.

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