Motor-driven hydraulic pressure generation device

Abstract

To provide a motor-driven hydraulic pressure generation device capable of mechanically holding a pressure in a hydraulic cylinder without using an electrically operating valve such as a solenoid valve.SOLUTION: A motor-driven hydraulic pressure generation device includes an electric motor, a ball screw including a screw shaft having a spiral screw groove formed in the outer peripheral face, a nut having a spiral screw groove formed in the inner peripheral face, and a plurality of balls for rolling on a load raceway formed by the screw groove of the screw shaft and the screw groove of the nut, for converting the rotating motion of the electric motor into the linear motion of either the screw shaft or the nut, a piston for moving together with either the screw shaft or the nut, and having a pressure chamber filled with working oil and constructed together with a housing, and a pressure holding valve mechanism provided on a hydraulic pressure circuit communicated from the pressure chamber, for mechanically actuating a rod extending to the pressure chamber with the piston to selectively open / close the valve.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electric hydraulic generator (also referred to as a "hydro booster") that generates hydraulic pressure using a ball screw.

Background Art

[0002] An electric hydraulic generator transmits the torque of a motor to a ball screw shaft, linearly moves a ball screw nut, compresses hydraulic oil with a piston screwed to the ball screw nut, and generates hydraulic pressure. Further, the hydraulic oil is pumped to a hydraulic cylinder via, for example, a hydraulic circuit to operate the hydraulic cylinder.

[0003] In the core control device of a molding machine described in Patent Document 1, an electric actuator combining a servo motor and a ball screw is provided. By driving a piston fixed to the ball screw, the suction and discharge operation of hydraulic oil from a hydraulic oil tank can be performed in a cylinder housing the piston, and hydraulic oil can be supplied from the hydraulic oil tank to the core cylinder. Further, a direction switching valve for switching the oil path is disposed between the electric actuator and the core cylinder, and the supply and discharge of hydraulic oil are performed between the actuator and the core cylinder via the oil path by switching the direction switching valve.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, when configuring a hydraulic circuit for operating a hydraulic cylinder, generally a solenoid valve is provided in the circuit, and the pressure in the hydraulic cylinder is maintained by operating the solenoid valve. Since a controller and an electric circuit are required to drive the solenoid valve, the configuration becomes complicated. Also in the core control device described in Patent Document 1, the direction switching valve uses a solenoid valve, and the above problems exist.

[0006] The present invention has been made in view of the above-described problems, and an object thereof is to provide an electro-hydraulic generator capable of mechanically maintaining the pressure in a hydraulic cylinder without using an electrically acting valve such as a solenoid valve.

Means for Solving the Problems

[0007] The above object of the present invention is achieved by the following configuration. [1] An electric motor, A screw shaft having a spiral screw groove formed on the outer peripheral surface, a nut having a spiral screw groove formed on the inner peripheral surface, and a plurality of balls that roll on a load track formed by the screw groove of the screw shaft and the screw groove of the nut, and converts the rotational motion of the electric motor into a linear motion of either the screw shaft or the nut. A ball screw, A piston that moves together with either the screw shaft or the nut and forms a pressure chamber filled with hydraulic oil together with a housing, A pressure holding valve mechanism provided on a hydraulic circuit communicating with the pressure chamber, and mechanically operating a rod extending into the pressure chamber by the piston to switch between valve opening and valve closing, Comprising, When the pressure holding valve mechanism opens the valve, the upstream circuit of the hydraulic circuit on the pressure chamber side with respect to the valve mechanism and the downstream circuit of the hydraulic circuit on the side opposite to the pressure chamber with respect to the valve mechanism are communicated, and the hydraulic oil is supplied to the downstream circuit of the hydraulic circuit. And when the valve is closed, the upstream circuit of the hydraulic circuit and the downstream circuit of the hydraulic circuit are blocked, and the pressure of the downstream circuit of the hydraulic circuit is maintained. An electro-hydraulic generator.

Effects of the Invention

[0008] According to the electro-hydraulic generating device of the present invention, it is possible to hold the pressure of a hydraulic cylinder or the like located downstream of the hydraulic circuit mechanically without using an electrically acting valve such as a solenoid valve.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0010] Hereinafter, the electro-hydraulic generating device according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0011] As shown in FIG. 1, the electro-hydraulic generating device 1 mainly includes an electric motor 2, a ball screw 10, a housing 20, a piston 30, and a pressure holding valve mechanism 40. The electro-hydraulic generating device 1 is connected to a hydraulic cylinder 81 via a hydraulic circuit 80, and the hydraulic oil in the hydraulic circuit 80 is supplied to and discharged from the hydraulic cylinder 81 to operate a piston 82 in the hydraulic cylinder 81. In the present embodiment, the hydraulic circuit 80 is composed of a hole formed in the housing 20 and a pipe 100 connecting the hole and the hydraulic cylinder 81.

[0012] The motor shaft 3 of the electric motor 2 and the input shaft portion 11b of the screw shaft 11 of the ball screw 10 are connected via a coupling 4. The screw shaft 11 is supported by the housing 20 via a bearing 14 at a portion between a screw groove 11a and the input shaft portion 11b, which will be described later.

[0013] The ball screw 10 includes a screw shaft 11 having a spiral screw groove 11a formed on the outer peripheral surface, a nut 12 having a spiral screw groove 12a formed on the inner peripheral surface, and a plurality of balls 13 that roll on a load track formed by the screw groove 11a of the screw shaft 11 and the screw groove 12a of the nut 12. A circulation component (not shown) is attached to the outer peripheral surface of the nut 12, and the ball 13 scooped up at one end of the load track passes through the circulation component and is returned to the other end of the load track, thereby forming an infinite circulation path.

[0014] A piston 30 is fastened and fixed to one axial end portion (the right end portion in the figure) of the nut 12 by a bolt 15. The piston 30 is prevented from rotating together with the nut 12 by the tip of another bolt 16 fixed to the housing 20 entering the axial groove 31. Thereby, the rotational motion of the electric motor 2 is transmitted to the ball screw 10 by the ball screw 10 and converted into a linear motion of the nut 12.

[0015] The piston 30 is formed in a bottomed cylindrical shape so as to cover one axial end of the screw shaft 11. Further, the housing 20 that covers the ball screw 10 and the piston 30 is also formed in a bottomed cylindrical shape. The piston 30 and the housing 20 together constitute a pressure chamber 21 filled with hydraulic oil, and the piston 30 slides inside the cylindrical surface of the housing 20. Note that the housing 20 is configured by connecting a plurality of housing members, and the electric motor 2 is fixed to the other axial end that opens. Further, the housing 20 may be configured by combining a plurality of housing members of other shapes.

[0016] A seal 17 is attached to the annular groove 32 formed on the outer peripheral surface of the piston 30 to prevent the hydraulic oil in the pressure chamber 21 from leaking between the piston 30 and the housing 20.

[0017] On the bottom 22 of the housing 20, a hydraulic circuit 80 that opens to the pressure chamber 21 extends along the central axis of the housing 20, bends at one axial end, and extends radially so as to open to the outer peripheral surface of the housing 20.

[0018] As shown in FIGS. 2 to 5, the pressure holding valve mechanism 40 is similar to a knock-type ballpoint pen structure and is disposed inside the accommodation space 23 and the rod insertion hole 24 formed in the bottom 22 of the housing 20. The accommodation space 23 is formed in a cylindrical shape along the axial direction of the housing 20, and the rod insertion hole 24 is formed in a cylindrical shape concentric with the accommodation space 23 adjacent to the accommodation space 23 so as to open to the pressure chamber 21. The accommodation space 23 has a stepped portion 23a with respect to the rod insertion hole 24 and is enlarged in diameter, and is connected to the hydraulic circuit 80 at one axial end side, dividing the hydraulic circuit 80 into an upstream circuit 80a and a downstream circuit 80b. The upstream circuit 80a opens to one axial end surface of the accommodation space 23, and the downstream circuit 80b opens to the inner peripheral surface of one axial end side of the accommodation space 23.

[0019] The pressure maintaining valve mechanism 40 includes a rod 41 disposed across from the rod insertion hole 24 to the accommodation space 23, and a stopper 50, a valve seat 60, a spring seat 70, a spring 71, and a valve 72 that are sequentially accommodated in the accommodation space 23 from the rod insertion hole 24 side.

[0020] The rod 41 is disposed so as to be axially movable within the accommodation space 23 and the rod insertion hole 24, and the other axial end (the left end in the figure) of the rod 41 extends from the rod insertion hole 24 into the pressure chamber 21. An annular groove 24a is formed on the inner peripheral surface of the rod insertion hole 24, and an O-ring 42 that slidably contacts the outer peripheral surface of the rod 41 is disposed in the annular groove 24a.

[0021] In addition, a convex portion 43 that fits into a slit 53 of a stopper 50 described later is provided on the outer peripheral surface of the rod 41. Also, as shown in FIG. 3, on the end surface on one axial end side of the rod 41, there is a first engaging portion 46 composed of a plurality of zigzag-shaped first inclined surfaces 45 that connect ridges and valleys provided at equal intervals in the circumferential direction. The ridges of the first inclined surfaces 45 are located at the circumferential center of the slit 53 of the stopper 50, and the valleys of the first inclined surfaces 45 are located outside the circumferential side surface of the slit 53 in the circumferential direction.

[0022] Furthermore, the rod 41 has a small-diameter shaft portion 47 that extends further axially on one side than the first engaging portion 46 on the inner diameter side of the first engaging portion 46 and passes through the valve seat 60, the spring seat 70, and the spring 71.

[0023] The stopper 50 is formed in a cylindrical shape with an inner diameter equal to the inner diameter of the rod insertion hole 24 so that the rod 41 can be inserted therethrough, and the other axial end abuts against a step 23a in the accommodation space 23 and is disposed in the accommodation space 23.

[0024] Further, as shown in FIG. 5, the stopper 50 has a plurality (four in this embodiment) of slits 53 formed at equal intervals in the circumferential direction on the end face at one axial end, and extending axially from the one axial end. Also, on the end face at the one axial end of the stopper 50, between adjacent slits 53, there is a second engaging portion 52 composed of a second inclined surface 51a that inclines from the peak portion toward one side in the circumferential direction to the valley portion, and a wall surface 51b that extends from the valley portion toward the peak portion along the axial direction, and a guide surface 54 that inclines parallel to the second inclined surface 51a from the wall surface 51b of the second engaging portion 52 toward the slit 53 in the circumferential direction. Note that the second inclined surface 51a and the first inclined surface 45 of the rod 41 have substantially equal inclination angles.

[0025] As shown in FIG. 4, the valve seat 60 has an annular portion 62 through which the small-diameter shaft portion 47 of the rod 41 can be inserted, and a plurality of shaft portions 61 having a width that allows for advancing and retreating within the slit 53 and extending axially from the annular portion 62. The shaft portion 61 has an engaged surface 61a that can contact the first inclined surface 45 and the second inclined surface 51a and whose tip is cut obliquely.

[0026] The valve 72 is formed in a frustum shape at one axial end side, receives the spring 71 at the other axial end side, and is biased by this spring 71 in a direction to block the upstream circuit 80a that opens at the axial end of the accommodation space 23 and the accommodation space 23. Note that the spring seat 70 provided between the valve seat 60 and the spring 71 is rotatable with respect to the valve seat 60.

[0027] The pressure holding valve mechanism 40 configured as described above switches between valve opening and valve closing when the rod 41 extending into the pressure chamber 21 is mechanically actuated by the piston 30.

[0028] Specifically, as shown in FIG. 2(a), when the pressure holding valve mechanism 40 is in the valve open state and the piston 30 starts to be stroked to increase the pressure in the pressure chamber 21 filled with hydraulic oil by the hydro booster 1, the hydraulic oil is supplied from the pressure chamber 21 to the hydraulic cylinder 81 through the hydraulic circuit 80.

[0029] As the piston 30 strokes, the pressure in the hydraulic circuit 80 continues to rise. At a certain position, the piston 30 contacts the rod 41 and then pushes the rod 41 from there. The movement of the rod 41 in the rotational direction is restricted by the convex portion 43 sliding within the slit 53 of the stopper 50. Also, the shaft portion 61 having the engaged surface 61a of the valve seat 60 slides within the slit 51 of the stopper 50.

[0030] When the stroke of the piston 30 further progresses, the valve seat 60 is pushed by the rod 41. At a certain point, the valve 72 closes the upstream circuit 80a, and the internal pressures of the downstream circuit 80b and the hydraulic cylinder 81 are maintained. When the rod 41 is pushed from there, the engaged surface 61a of the valve seat 60 reaches the second engaging portion 52 of the stopper 50. Further, it climbs over the mountain-shaped portion along the second inclined surface 51a of the stopper 50, and the valve seat 60 moves while rotating, and the engaged surface 61a of the valve seat 60 engages with the second engaging portion 52 of the stopper 50. Thereby, as shown in FIG. 2(b), the position of the valve 72 is fixed, and the upstream circuit 80a remains blocked even without applying a force via the rod 41. For this reason, even if the piston 30 is retracted by the electric motor 2, the internal pressure below the downstream circuit 80b can be maintained.

[0031] Also, by pushing the rod 41 again with the piston 30, the engaged surface 61a of the valve seat 60 held in engagement with the first engaging portion of the stopper 50 can move onto the guide surface 54 and slide on the guide surface 54 to move the shaft portion 61 into the next slit 53. Thereby, the valve seat 60 becomes movable, and the valve 72 can be opened.

[0032] That is, the pressure holding valve mechanism 40, when opening the valve, communicates the upstream circuit 80a of the hydraulic circuit 80 on the pressure chamber side with respect to the valve mechanism 40 and the downstream circuit 80b of the hydraulic circuit 80 on the side opposite to the pressure chamber with respect to the valve mechanism 40, and supplies the hydraulic oil to the downstream circuit 80a of the hydraulic circuit 80. Also, the pressure holding valve mechanism 40, when closing the valve, shuts off the upstream circuit 80a of the hydraulic circuit 80 and the downstream circuit 80b of the hydraulic circuit 80, and holds the pressure of the downstream circuit 80b of the hydraulic circuit 80.

[0033] As described above, in the hydro booster (electro-hydraulic generator) 1 that generates hydraulic pressure using the ball screw 12, by providing a mechanically operating pressure holding valve mechanism 40 between the pressure chamber 21 and the hydraulic cylinder 81 which is the pumping destination of the hydraulic oil, the pressure of the hydraulic cylinder 81 can be held without using a solenoid valve. As a result, it is not necessary to continuously generate motor torque while the pressure in the hydraulic circuit 80 is being held, or a brake mechanism for restraining the rotation of the ball screw 10 is also not required.

[0034] Note that the present invention is not limited to the above-described embodiments, and can be appropriately modified, improved, etc. For example, as shown in FIG. 6, the rod insertion hole 24 of the housing 20 may be formed by a rod support member 90 that is screwed and fixed to the female screw portion 25a of the opening hole 25 formed in the housing 20. Also in this case, the rod support member 90 forms a step 23a of the accommodation space 23, and an annular groove 24a for accommodating the O-ring 42 is formed on the inner peripheral surface of the rod insertion hole 24.

[0035] Further, the pressure holding valve mechanism of the present invention is not limited to that of the above-described embodiment, and may be provided on a hydraulic circuit communicating from the pressure chamber, and may be configured to switch between valve opening and valve closing by mechanically operating a rod extending into the pressure chamber with a piston. Furthermore, in the above embodiment, the piston is connected to the nut of the ball screw and moves together with the nut. However, for example, an electric motor may drive the nut, and the piston may be connected to the screw shaft of the ball screw and move together with the screw shaft.

[0036] As described above, the following matters are disclosed in this specification. (1) An electric motor, A ball screw comprising a screw shaft having a helical thread groove formed on its outer peripheral surface, a nut having a helical thread groove formed on its inner peripheral surface, and a plurality of balls that roll on a load path formed by the thread groove of the screw shaft and the thread groove of the nut, and converting the rotational motion of the electric motor into linear motion of either the screw shaft or the nut. A piston that moves together with either the screw shaft or the nut and forms a pressure chamber filled with hydraulic oil together with a housing. A pressure holding valve mechanism provided on a hydraulic circuit communicating with the pressure chamber, and switching between valve opening and valve closing by mechanically operating a rod extending into the pressure chamber by the piston. Comprising By opening the pressure holding valve mechanism, the upstream circuit of the hydraulic circuit on the pressure chamber side with respect to the valve mechanism and the downstream circuit of the hydraulic circuit on the side opposite to the pressure chamber with respect to the valve mechanism are communicated, the hydraulic oil is supplied to the downstream circuit of the hydraulic circuit, and by closing the valve, the upstream circuit of the hydraulic circuit and the downstream circuit of the hydraulic circuit are blocked, and the pressure of the downstream circuit of the hydraulic circuit is held. An electro-hydraulic generator. According to this configuration, it is possible to mechanically hold the pressure in the downstream circuit of the hydraulic circuit without using an electrically acting valve such as a solenoid valve.

[0037] (2) A hydraulic cylinder is provided in the downstream circuit of the hydraulic circuit. The electro-hydraulic generator according to (1). According to this configuration, it is possible to mechanically hold the pressure in the hydraulic cylinder without using an electrically acting valve such as a solenoid valve.

[0038] (3) In the housing, a cylindrical accommodation space that opens to the hydraulic circuit, the upstream circuit and the downstream circuit of the hydraulic circuit, and accommodates the pressure holding valve mechanism, and a rod insertion hole that is provided adjacent to the accommodation space so as to open to the pressure chamber and through which the rod is inserted are formed. The electro-hydraulic generator according to (1) or (2). According to this configuration, a hydraulic circuit having a mechanical pressure holding valve mechanism can be arranged in the housing.

[0039] (4) The pressure holding valve mechanism includes a rod disposed across the rod insertion hole into the accommodation space, and a stopper, a valve seat, a spring seat, a spring, and a valve sequentially accommodated in the accommodation space from the rod insertion hole side. The stopper is formed in a cylindrical shape with a plurality of slits extending axially from an end face at an axial end thereof at equal intervals in the circumferential direction. The valve seat has an engaged surface with a tip cut obliquely, and has an axial portion extending axially and capable of advancing and retreating within the slit. The valve is biased by the spring in a direction to block the upstream circuit opening at an axial end of the accommodation space and the accommodation space. The rod is insertable into the stopper, and has a first engaging portion with a slope on an end face at an axial end thereof that can engage with the engaged surface of the valve seat. The stopper has, at an end face at the axial end, a second engaging portion having a slope that can engage with the engaged surface of the valve seat and a wall surface along the axial direction between adjacent slits, and a guide surface formed between the wall surface and the slit. The electro-hydraulic generating device according to (3). According to this configuration, the valve opening and closing of the pressure holding valve mechanism can be switched with a compact configuration.

Explanation of Reference Numerals

[0040] 1 Electro-hydraulic generating device 2 Electric motor 3 Motor shaft 4 Coupling 10 Hydro booster 11 Screw shaft 11a, 12a Thread groove 11b Input shaft portion 12 Nut 13 Ball 14 Bearing 15, 16 Bolt 17 Seal 20 Housing 21 Pressure chamber 22 Bottom 23 Accommodation space 23a Step 24 Rod insertion hole 30, 82 Piston 31 Axial groove 32 Annular groove 40 Pressure holding valve mechanism 41 Rod 42 O-ring 43 Protrusion 45 First inclined surface 46 First engaging portion 50 Stopper 51a Second inclined surface 52 Second engaging portion 53 Slit 54 Guide surface 60 Valve seat 61 Shaft portion 61a Engaged surface 70 Spring seat 72 Valve 80 Hydraulic circuit 80a Upstream circuit 80b Downstream circuit 81 Hydraulic cylinder

Claims

1. An electric motor, a screw shaft having a spiral thread groove formed on its outer peripheral surface, a nut having a spiral thread groove formed on its inner peripheral surface, and a plurality of balls that roll on a load path formed by the thread groove of the screw shaft and the thread groove of the nut, the ball screw that converts the rotational motion of the electric motor into linear motion of either the screw shaft or the nut, a piston that moves together with either the screw shaft or the nut and forms a pressure chamber filled with hydraulic oil together with a housing, a pressure holding valve mechanism provided on a hydraulic circuit communicating with the pressure chamber, and mechanically operating a rod extending into the pressure chamber by the piston to switch between valve opening and valve closing, and the pressure holding valve mechanism communicates, by opening the valve, an upstream circuit of the hydraulic circuit on the pressure chamber side with respect to the valve mechanism and a downstream circuit of the hydraulic circuit on the side opposite to the pressure chamber with respect to the valve mechanism, supplies the hydraulic oil to the downstream circuit of the hydraulic circuit, and by closing the valve, shuts off the upstream circuit and the downstream circuit of the hydraulic circuit and holds the pressure of the downstream circuit of the hydraulic circuit. An electro-hydraulic generator.

2. A hydraulic cylinder is provided in the downstream circuit of the hydraulic circuit. The electro-hydraulic generator according to claim 1.

3. In the housing, there are formed a cylindrical accommodation space in which the hydraulic circuit, the upstream circuit and the downstream circuit of the hydraulic circuit each open and that accommodates the pressure holding valve mechanism, and a rod insertion hole that is provided adjacent to the accommodation space so as to open into the pressure chamber and through which the rod is inserted. The electro-hydraulic generator according to claim 1 or 2.

4. The pressure holding valve mechanism includes a rod disposed across the rod insertion hole into the accommodation space, and a stopper, a valve seat, a spring seat, a spring, and a valve that are accommodated in the accommodation space in order from the rod insertion hole side. The stopper is formed in a cylindrical shape with a plurality of slits extending axially from the end face of its axial end at equal circumferential intervals, The valve seat has an engaged surface with a slanted tip, and has an axially extending shaft portion that can advance and retreat within the slit. The valve is biased by the spring in a direction to block the upstream circuit that opens at the axial end of the accommodation space and the accommodation space. The rod is insertable into the stopper, and has a first engaging portion with a slope on the end face of its axial end that can engage with the engaged surface of the valve seat. The stopper has, at the end face of the axial end, a second engaging portion having a slope that can engage with the engaged surface of the valve seat and a wall surface along the axial direction between adjacent slits, and a guide surface formed between the wall surface and the slit. The electro-hydraulic generating device according to claim 3.

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