Lubrication device and linear actuator equipped therewith

Abstract

The present invention provides a lubrication device capable of supplying lubricant to the lubrication passage of a moving member and cushioning the impact on the moving member, and a linear actuator equipped therewith. [Solution] The lubrication device 50 comprises a fixed cylinder housing a piston, a piston spring positioned between the fixed cylinder and the piston, a stopper member fixed to the open end of the fixed cylinder and having a communication hole, a valve slidably mounted in a through hole provided in a movable cylinder slidably mounted relative to the fixed cylinder, and a valve spring positioned between the stopper member and the valve. The fixed cylinder, piston, and stopper member form a sub-chamber, and the movable cylinder and stopper member form a main chamber. The communication holes of the sub-chamber, main chamber, and stopper member are filled with lubricant.

Description

Technical Field

[0001] The present invention relates to a lubricating device and a linear actuator provided with a lubricating device using a linear motion device such as a ball screw.

Background Art

[0002] In a linear actuator using a ball screw, it is necessary to supply a lubricant regularly due to the characteristics of the ball screw. Generally, the lubricant is supplied into the actuator through a lubricating member such as a grease nipple. However, when the linear actuator has to be installed in a narrow space, the lubrication work may be difficult or the grease nipple may not be provided at all.

[0003] Therefore, in Patent Documents 1 and 2, it is known that a lubricating mechanism is provided inside the actuator to eliminate the need for manual lubrication work. In the ball screw device described in Patent Document 1, a room filled with a lubricant is provided inside the actuator, and the lubricant is dropped into the ball screw by gravity from there. In addition, in the screw mechanism described in Patent Document 2, an oil-impregnated resin member is provided on the end face of the ball screw nut, and the lubricating oil is configured to ooze out from the resin member.

[0004] Furthermore, in the linear guide device described in Patent Document 3, a lubricant receiving port is provided at the end of the slider body in the moving direction. When the lubricant receiving port is pressed against the lubricant supply port of the lubricant tank as the slider body moves, it is described that the lubricant supply pores are provided to supply the lubricant in the lubricant tank to the lubricant receiving port.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

[0006] Incidentally, in linear actuators and the like, an excessive external input exceeding the torque that the electric motor can generate can unexpectedly cause the ball screw nut to reverse, leading to internal collisions and damage to the nut itself or the collision components. None of the mechanisms described in Patent Documents 1 to 3 recognize this problem, and further improvements are needed.

[0007] Furthermore, the structure described in Patent Document 1 has several drawbacks, including limitations on the mounting direction of the actuator, changes in the amount of lubricant dispensed when the viscosity of the lubricant changes due to changes in ambient temperature, and the inability to dispense lubricants with high viscosity or consistency. In addition, the structure described in Patent Document 2 has several drawbacks, including limitations on the types of lubricants that can be used because the lubricant must be impregnated into the resin, and the inability to control the amount of lubricant that seeps out.

[0008] The present invention has been made in view of the aforementioned problems, and its object is to provide a lubrication device and a linear actuator equipped therewith that can supply lubricant to the lubrication passage of a moving member and can cushion the impact caused by the unexpected movement of the moving member. [Means for solving the problem]

[0009] The above objective of the present invention is achieved by the following configuration. [1] A lubrication device that supplies lubricant to a movable member that is movable in the axial direction, having a receiving port for a lubrication passage on its axial end face, A fixed cylinder housing a piston that has an opening on one axial side and is slidable in the axial direction, A piston spring is positioned between the bottom of the fixed cylinder and the piston, A stopper member is fixed to the opening end of the fixed cylinder, cooperates with the piston to form a first chamber within the fixed cylinder, and has a communication hole that penetrates axially, A movable cylinder is provided on the opening side of the fixed cylinder so as to be slidable relative to the fixed cylinder and cooperates with the stopper member to form a second chamber, A valve is slidably mounted in a through hole provided at the bottom of the movable cylinder, and has an orifice that connects or blocks the second chamber from the outside depending on the sliding position. A valve spring is positioned between the stopper member and the valve and biases the tip of the valve so that it protrudes from the through hole of the movable cylinder, Equipped with, The first chamber and the second chamber are connected through the communication hole, The communication holes of the first chamber, the second chamber, and the stopper member are filled with the lubricant. As the moving member moves, the valve slides within the through hole against the biasing force of the valve spring, thereby enabling the supply port of the orifice provided at the tip of the valve to communicate with the receiving port of the lubrication passage of the moving member, and supplying the lubricant to the lubrication passage. Greasing device. [Effects of the Invention]

[0010] According to the lubrication device of the present invention, lubricant can be supplied to the lubrication passage of the moving member, and shocks caused by the unexpected movement of the moving member can be absorbed. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view of a linear actuator according to the first embodiment of the present invention. [Figure 2] This is a cross-sectional view along line AA in Figure 1. [Figure 3] This is a cross-sectional view of the lubrication device. [Figure 4]It is a cross-sectional view showing a state where a ball screw nut contacts and presses against a valve of a lubricant supply device. [Figure 5] It is a cross-sectional view for explaining a process of replenishing a lubricant to the lubricant supply device. [Figure 6] It is a cross-sectional view showing a state where a piston is pulled by a piston pin when replenishing a lubricant to the lubricant supply device. [Figure 7] It is a cross-sectional view showing a state where an air vent hole provided in a fixed-side cylinder of the lubricant supply device is closed by a plug. [Figure 8] It is a cross-sectional view of a lubricant supply device of a linear actuator according to a second embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, a linear actuator including a lubricant supply device according to an embodiment of the present invention will be described in detail based on the drawings.

[0013] As shown in FIG. 1, the linear actuator [1] of the present embodiment mainly includes an electric motor [2], a rolling bearing [3], a sliding bearing [4], a rod [5], a ball screw

[10] , a housing

[20] , a rotation prevention mechanism

[30] , and a lubricant supply device

[50] . In the present embodiment, as shown in FIG. 1, the direction in which the rod [5] moves away from the electric motor [2] is defined as one axial side, and the direction in which the rod [5] moves closer to the electric motor [2] is defined as the other axial side.

[0014] The ball screw

[10] includes a ball screw shaft

[11] having a spiral thread groove [11a] formed on its outer peripheral surface, a ball screw nut

[12] having a spiral thread groove [12a] formed on its inner peripheral surface, and a plurality of balls

[13] that roll on a load track formed by the thread groove [11a] of the ball screw shaft

[11] and the thread groove [12a] of the ball screw nut

[12] . The ball screw shaft

[11] is fixed to the motor shaft [2a] of the electric motor [2] and is rotatably supported with respect to the housing

[20] via the rolling bearing [3]. The ball screw

[10] converts the rotational motion of the electric motor [2] into a linear motion of the ball screw nut

[12] via the ball screw shaft

[11] .

[0015] The housing 20 includes a motor mount 21 to which the electric motor 2 is fixed, a bearing holder 22 connected to the motor mount 21 and supporting a portion of the rolling bearing 3, and a main housing 23 connected to the bearing holder 22 and housing the rod 5, ball screw 10, and lubrication device 50. The motor mount 21, bearing holder 22, and main housing 23 are all formed in a cylindrical shape.

[0016] The rolling bearing 3 has an inner ring that is fitted and fixed to the outer surface of the ball screw shaft 11 by a nut 6, and an outer ring that is fitted and fixed to the inner surface of the motor mount 21 and the bearing holder 22.

[0017] The rod 5 is fixed to the ball screw nut 12 and extends and retracts from the opening 23a at one axial end of the main housing 23 as the ball screw nut 12 moves axially. The rod 5 is slidably supported by a sliding bearing 4 fixed to one axial end of the main housing 23.

[0018] The anti-rotation mechanism 30 has an anti-rotation groove 31 formed in the circumferential direction of a part of the inner surface of the main housing 23, which extends along the axial direction. An anti-rotation member 32 fixed to the ball screw nut 12 slides along the anti-rotation groove 31, causing the ball screw nut 12 to move in a straight line.

[0019] The ball screw nut 12 has a lubrication passage 40 formed therein, which extends axially from the other end face on its axial side, penetrates radially to the inner and outer circumferential surfaces, and communicates with the lubrication passage of the anti-rotation member 32 from the outer circumferential surface.

[0020] Furthermore, inside the main housing 23, a lubrication device 50 is fixed to one axial side of the bearing holder 22 around the ball screw shaft 11.

[0021] As shown in Figure 3, the lubrication device 50 mainly comprises a fixed cylinder 51, a piston 52, a piston spring 53, a stopper member 54, a movable cylinder 60, a valve 61, a valve spring 62, and a main spring 70.

[0022] The stationary cylinder 51 has a U-shaped cross-section with an opening on one axial side, is formed in a ring shape around the ball screw shaft 11, and is fixed to the bearing holder 22 by a bolt 55 provided at the bottom 51a. Inside the stationary cylinder 51, a ring-shaped piston 52 having seals 56 on its outer and inner circumferential surfaces is housed so as to be slidable in the axial direction.

[0023] The piston spring 53 is positioned between the bottom 51a of the fixed cylinder 51 and the piston 52, biasing the piston 52 in one axial direction.

[0024] The stopper member 54 is fixed to the opening end of the fixed cylinder 51 by a fixing pin 57. The stopper member 54 cooperates with the piston 52 to form a sub-chamber 58, which is a first chamber, within the fixed cylinder 51, and has a plurality of communication holes 59 that penetrate in the axial direction (plate thickness direction).

[0025] The movable cylinder 60 has a U-shaped cross-section with an opening on the other axial side and is formed in a ring shape around the ball screw shaft 11. The movable cylinder 60 is slidably mounted on the opening side of the fixed cylinder 51 so as to slide against the outer and inner cylindrical portions of the fixed cylinder 51, and forms a second chamber, the main chamber 63, between the stopper member 54 fixed to the fixed cylinder 51 and the inside of the movable cylinder 60.

[0026] Therefore, the sub-chamber 58 and the main chamber 63 are in communication with each other through multiple communication holes 59 in the stopper member 54.

[0027] Furthermore, seals 64 are provided on the outer surface of the outer cylindrical portion and the inner surface of the inner cylindrical portion of the fixed cylinder 51, on which the movable cylinder 60 slides, thereby sealing the main chamber 63.

[0028] Furthermore, a groove 65 is formed along the axial direction on the outer surface of the outer cylindrical portion of the fixed cylinder 51, and the tip of the stopper pin 66, which is press-fitted into the movable cylinder 60, moves within the groove 65, thereby restricting the amount of movement of the movable cylinder 60 relative to the fixed cylinder 51.

[0029] The valve 61 is slidably mounted in a through hole 67 located in the bottom 60a of the movable cylinder 60, at a position in the circumferential direction opposite to the lubrication port 40a of the lubrication passage 40 of the ball screw nut 12. The valve 61 also has an orifice 61a that connects or blocks the main chamber 63 to the outside (in this embodiment, the inside of the main housing 23) depending on its sliding position.

[0030] The valve spring 62 is positioned between the recess 54a formed in the stopper member 54 and the flange portion 61b of the valve 61, so that the flange portion 61b abuts against the bottom portion 60a of the movable cylinder 60 and biases the tip of the valve 61 to protrude from the through hole 60a of the movable cylinder 60.

[0031] Furthermore, a main spring 70 is positioned between the other axial end face of the movable cylinder 60 and the bearing holder 22 to which the fixed cylinder 51 is attached, around the outer cylindrical portion of the fixed cylinder 51, thereby biasing the movable cylinder 60 to one axial side.

[0032] In the lubrication device 50 configured in this way, when supplying lubricant such as grease, as shown in Figure 5, the pressurizing nozzle 81 of the lubricant pressurizing device 80 is inserted into the through hole 60a of the movable cylinder 60, and the valve 61 is also pushed toward the main chamber 63, so that the orifice 68 inside the valve 61 communicates with the main chamber 63. When lubricant is supplied from the pressurizing nozzle 81 through the orifice 61a, the sub-chamber 58, which communicates with the main chamber 63, is filled with lubricant. As filling continues, the piston 52 supported by the piston spring 53 gradually slides inside the fixed cylinder 51, the volume inside the sub-chamber 58 increases, and the piston spring 53 is compressed, resulting in a pressurized state inside both the main chamber 63 and the sub-chamber 58.

[0033] Furthermore, as shown in Figure 6, the lubricant may be filled while the portion of the piston pin 82 provided on the piston 52 that protrudes from the stationary cylinder 51 is being pulled. After filling is complete, releasing the pull on the piston pin 82 causes the piston 52 to be pushed by the piston spring 53, resulting in a pressurized state inside. Furthermore, as shown in Figure 7, an air vent hole 83 may be provided in the fixed cylinder 51 to facilitate the removal of internal air. After the piston pin 82 is pulled and lubricant is filled, the air vent hole 83 is closed by a plug 84.

[0034] Then, when the supply of lubricant from the orifice 61a is stopped and the valve 61 is no longer pushed in, the valve 61 returns to its protruding state from the movable cylinder 60, and the orifice 61a and the main chamber 63 are blocked off. As a result, the lubricant is held under pressure in the main chamber 63 and the sub-chamber 58. At this time, the stopper pin 66, which is press-fitted into the movable cylinder 60, catches in the groove 65 formed in the fixed cylinder 51, preventing the movable cylinder 60, which is slidably fitted with the fixed cylinder 51, from falling out.

[0035] As shown in Figure 4, when the ball screw nut 12 contacts the valve 61 of the lubrication device 50 and the valve 61 is pushed in, the main chamber 63 and the orifice 61a are connected, lubricant is discharged from the pressurized main chamber 63, passes through the orifice 61a and is supplied to the lubrication passage 40 of the ball screw nut 12. As a result, the lubricant already filled in the lubrication passage 40 is pushed out and lubricant is supplied to the inner diameter of the ball screw nut 12 and both sides of the anti-rotation member 32. When the ball screw nut 12 is separated from the valve 61, the valve spring 62 returns the valve 61 to its original position and the discharge of lubricant stops.

[0036] Repeated discharge reduces the internal lubricant, causing the piston spring 53 to stretch completely. This releases the pressurized state in the main chamber 63 and sub-chamber 58, and the lubricant can no longer be discharged by simply pushing in the valve 61. However, pushing in the movable cylinder 60 along with the valve 61 reduces the volume of the main chamber 63, allowing the lubricant to be discharged. At the same time, the piston 52 is pushed, expanding the volume of the sub-chamber 58, and the lubricant attempts to move into the sub-chamber 58. However, the piston 52 and the protrusions inside the fixed cylinder 51 come into contact, stopping the volume expansion in the sub-chamber 58 at a certain point. As a result, the lubricant is discharged through the orifice 61a.

[0037] It is not always necessary to switch to a discharge mode in which the movable cylinder 60 is pushed after a discharge mode in which only the valve 61 is pushed; it is also possible to use the discharge mode in which the movable cylinder 60 is pushed from the beginning.

[0038] To avoid the ball screw nut 12 frequently contacting the lubrication device 50 and discharging lubricant, it is desirable to operate the electric motor 2 using position control. This allows for the creation of an operation program that moves the ball screw nut 12 in a position that normally does not contact the lubrication device 50, and only makes contact at the time of lubrication. Examples of operation programs include one that automatically moves to the lubrication position after a predetermined number of operations, or one that automatically moves to the lubrication position immediately after the power is turned on and the servo of the electric motor 2 is switched on.

[0039] Furthermore, if an external force exceeding the torque that the electric motor 2 can generate is applied through the rod 5 and the ball screw 10, the electric motor 2 is typically de-energized by the higher-level motor driver, and the actuator is unable to generate thrust. As a result, the ball screw nut 12 collides with the movable cylinder 60. As the movable cylinder 60 is pushed in, the ball screw nut 12 gradually receives the repulsive force of the main spring 70, thus mitigating the impact force.

[0040] Furthermore, when the movable cylinder 60 is pressed, lubricant is discharged, but resistance is generated as the lubricant is discharged through the orifice 61a, which acts like an oil damper, resulting in a damping effect.

[0041] As described above, the lubrication device 50 of this embodiment supplies lubricant to the lubrication passage 40 provided in the ball screw nut 12 only when the ball screw nut 12, which moves in a straight line due to the rotation of the electric motor 2, is brought into contact with it. Furthermore, if the ball screw nut 12 unexpectedly reverses direction and collides with the lubrication device 50 due to an excessive input exceeding the torque that the electric motor 2 can generate, the device also has a function to dampen the impact force. The load at the time of impact is absorbed by the spring, and a damping effect is obtained by the resistance as the lubricant passes through the narrow passage.

[0042] (Second Embodiment) As shown in Figure 8, in the second embodiment, the lubrication device 50 is configured without a main spring, unlike in the first embodiment. This reduces the spring's repulsive force acting on the movable cylinder 60, allowing the lubricant to be discharged with less force. While the shock-absorbing effect of the main spring is eliminated, the damping effect from the lubricant discharge remains unchanged.

[0043] Furthermore, the present invention is not limited to the embodiments described above, and can be modified, improved, etc., as appropriate. For example, in the above embodiment, the piston 52, fixed cylinder 51, movable cylinder 60, and stopper member 54 that constitute the lubrication device 50 are all formed in a ring shape around the ball screw shaft 11, but the present invention is not limited to this. For example, a plurality of lubrication devices 50 having a bottomed cylindrical fixed cylinder 51 and movable cylinder 60, a disc-shaped piston 52, and a stopper member 54 may be arranged around the ball screw shaft 11, and at least one lubrication device 50 may be provided such that the valve 61 faces the receiving port 40a of the lubrication passage 40 of the ball screw nut 12.

[0044] Furthermore, in the above embodiment, the rotational motion of the electric motor is converted into linear motion of the nut via the screw shaft, but the present invention is not limited to this, and the electric motor may be connected to the nut and converted into linear motion of the screw shaft. In this case as well, by arranging a lubrication device at the stroke end of the screw shaft having a lubrication passage as a moving member, lubricant can be supplied and collision forces due to the unexpected movement of the moving member can be mitigated.

[0045] As described above, the following matters are disclosed in this specification: (1) A lubrication device that supplies lubricant to a movable member that is movable in the axial direction, having a receiving port for a lubrication passage on its axial end face, A fixed cylinder housing a piston that has an opening on one axial side and is slidable in the axial direction, A piston spring is positioned between the bottom of the fixed cylinder and the piston, A stopper member is fixed to the opening end of the fixed cylinder, cooperates with the piston to form a first chamber within the fixed cylinder, and has a communication hole that penetrates axially, A movable cylinder is provided on the opening side of the fixed cylinder so as to be slidable relative to the fixed cylinder and cooperates with the stopper member to form a second chamber, A valve is slidably mounted in a through hole provided at the bottom of the movable cylinder, and has an orifice that connects or blocks the second chamber from the outside depending on the sliding position. A valve spring is positioned between the stopper member and the valve and biases the tip of the valve so that it protrudes from the through hole of the movable cylinder, Equipped with, The first chamber and the second chamber are connected through the communication hole, The communication holes of the first chamber, the second chamber, and the stopper member are filled with the lubricant. As the moving member moves, the valve slides within the through hole against the biasing force of the valve spring, thereby enabling the supply port of the orifice provided at the tip of the valve to communicate with the receiving port of the lubrication passage of the moving member, and supplying the lubricant to the lubrication passage. Greasing device. This configuration allows lubricant to be supplied to the lubrication passage of the moving member, and also allows for the cushioning of impacts caused by unexpected movements of the moving member.

[0046] (2) The piston, the fixed cylinder, the movable cylinder, and the stopper member are formed in a ring shape, The aforementioned piston springs are arranged in multiples at equal intervals in the circumferential direction. (1) The lubrication device described above. This configuration allows the lubrication device to be configured in a ring shape.

[0047] (3) A spring is placed between the axial end face of the movable cylinder and the fixed member to which the fixed cylinder is attached. (1) The lubrication device described above. With this configuration, the spring can better cushion the impact caused by the unexpected movement of the moving member.

[0048] (4) A lubrication device as described in any of (1) to (3), Electric motor and, A ball screw comprising a screw shaft with a helical screw groove formed on its outer circumference, a nut with a helical screw groove formed on its inner circumference, and a plurality of balls that roll along a load track formed by the screw groove of the screw shaft and the screw groove of the nut, wherein the rotational motion of the electric motor is converted into linear motion of the moving member of either the screw shaft or the nut, A linear actuator equipped with the following features. This configuration allows lubricant to be supplied to the lubrication passage of the moving member, and also allows for the cushioning of impacts caused by unexpected movements of the moving member.

[0049] (5) The screw shaft is fixed to the motor shaft of the electric motor and is rotatably supported relative to the housing via a rolling bearing, The ball screw converts the rotational motion of the electric motor into linear motion of the nut via the screw shaft. A rod that moves linearly together with the nut is fixed to the nut, and a lubrication passage is formed therein through which a lubricant for lubricating the plurality of balls passes. In the lubrication device, the piston, the fixed cylinder, the movable cylinder, and the stopper member are formed in a ring shape around the ball screw shaft, and the piston springs are arranged in multiples at equal intervals in the circumferential direction. (4) A linear actuator as described above. This configuration allows the lubrication device to be arranged in a ring shape around the ball screw shaft. [Explanation of symbols]

[0050] 1 Linear Actuator 2 Electric motor 3 Rolling bearings 4. Plain bearings 5 rods 10 Ball screws 11 Ball screw shaft 11a, 12a Screw groove 12 Ball screw nuts 13 Balls 20 Housing 21 Motor Mount 22 Bearing holder 23 Main Housing 30. Anti-rotation mechanism 31 Anti-rotation groove 32 Anti-rotation member 40 Greasing communication passage 50 Greasing device 51 Fixed side cylinder 52 pistons 53 Piston Springs 54 Stopper member 58 Sub-chamber (First chamber) 59 Communication hole 60 Movable side cylinder 61 valves 61a Orifice 62 Valve Springs 63 Main Chamber (Second Chamber) 70 Mainspring

Claims

1. A lubrication device that supplies lubricant to a movable member that is movable in the axial direction, having a receiving port for a lubrication passage on its axial end face, A fixed cylinder housing a piston that has an opening on one axial side and is slidable in the axial direction, A piston spring is positioned between the bottom of the fixed cylinder and the piston, A stopper member is fixed to the opening end of the fixed cylinder, cooperates with the piston to form a first chamber within the fixed cylinder, and has a communication hole that penetrates axially, A movable cylinder is provided on the opening side of the fixed cylinder so as to be slidable relative to the fixed cylinder and cooperates with the stopper member to form a second chamber, A valve is slidably mounted in a through hole provided at the bottom of the movable cylinder, and has an orifice that connects or blocks the second chamber from the outside depending on the sliding position. A valve spring is positioned between the stopper member and the valve and biases the tip of the valve so that it protrudes from the through hole of the movable cylinder, Equipped with, The first chamber and the second chamber are connected through the communication hole, The communication holes of the first chamber, the second chamber, and the stopper member are filled with the lubricant. As the moving member moves, the valve slides within the through hole against the biasing force of the valve spring, thereby enabling the supply port of the orifice provided at the tip of the valve to communicate with the receiving port of the lubrication passage of the moving member, and supplying the lubricant to the lubrication passage. Greasing device.

2. The piston, the fixed cylinder, the movable cylinder, and the stopper member are formed in a ring shape. The aforementioned piston springs are arranged in multiples at equal intervals in the circumferential direction. The lubrication device according to claim 1.

3. A spring is positioned between the axial end face of the movable cylinder and the fixing member to which the fixed cylinder is attached. The lubrication device according to claim 1.

4. A lubrication device according to any one of claims 1 to 3, Electric motor and, A ball screw comprising a screw shaft with a helical screw groove formed on its outer circumference, a nut with a helical screw groove formed on its inner circumference, and a plurality of balls that roll along a load track formed by the screw groove of the screw shaft and the screw groove of the nut, wherein the rotational motion of the electric motor is converted into linear motion of the moving member of either the screw shaft or the nut, A linear actuator equipped with the following features.

5. The screw shaft is fixed to the motor shaft of the electric motor and is rotatably supported in relation to the housing via a rolling bearing. The ball screw converts the rotational motion of the electric motor into linear motion of the nut via the screw shaft. A rod that moves linearly together with the nut is fixed to the nut, and a lubrication passage is formed therein through which a lubricant for lubricating the plurality of balls passes. In the lubrication device, the piston, the fixed cylinder, the movable cylinder, and the stopper member are formed in a ring shape around the ball screw shaft, and the piston springs are arranged in multiples at equal intervals in the circumferential direction. The linear actuator according to claim 4.

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