Linear actuator

Abstract

To provide a linear actuator that reliably maintains the position of the output shaft when not in operation. [Solution] The linear actuator 1 comprises a drive force transmission unit 30 that transmits the driving force of a motor, a ball screw that moves linearly by the driving force transmitted by the drive force transmission unit 30, a drive stop unit 60 coupled to the drive force transmission unit 30 that stops the driving of the drive force transmission unit 30, and a case that houses the motor, the drive force transmission unit 30, the ball screw, and the drive stop unit 60. The drive force transmission unit 30 has a motor rotation shaft, a drive gear 31 provided on the rotation shaft, and a group of transmission gears 32 connected to the drive gear 31 that transmits the rotational driving force of the drive gear 31 to the ball screw. When not in operation, the drive stop unit 60 stops the driving of the drive force transmission unit 30.

Description

Technical Field

[0001] This invention relates to a linear actuator.

Background Art

[0002] As a configuration of a conventional linear actuator, the one described in Patent Document 1 is known. The linear actuator described in this Patent Document 1 includes a motor, a ball screw nut connected to the rotation shaft of the motor, a ball screw which is an output shaft screwed to the ball screw nut, a rotation brake disk fixed to the rotation shaft, and a fixed brake disk that is pressed against the rotation brake disk to stop the rotation of the rotation shaft. The rotation brake disk and the fixed brake disk constitute a friction brake device. And, when this linear actuator is in a non-operating state where power is not supplied, the fixed brake disk is pressed against the rotation brake disk, so that the rotation of the rotation shaft of the motor stops, and the ball screw, which is the output shaft, is held at a certain position.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the linear actuator described in Patent Document 1, since the rotation shaft is braked by the frictional force between the rotation brake disk and the fixed brake disk of the friction brake device when not in operation, due to the decrease in the frictional force caused by the secular change of the rotation brake disk and the fixed brake disk, when the braking force of the friction brake device decreases, there is a problem that the position of the ball screw, which is the output shaft, cannot be sufficiently held when not in operation.

[0005] This invention was made to solve these problems and aims to provide a linear actuator that reliably maintains the position of the output shaft when not in operation. [Means for solving the problem]

[0006] To solve the above problems, the linear actuator according to the present invention comprises a motor, a drive force transmission unit that transmits the driving force of the motor, a linear motion mechanism unit that moves in a straight line by the driving force transmitted by the drive force transmission unit, a drive stop unit coupled to the drive force transmission unit that stops the driving of the drive force transmission unit, and a case unit that houses the motor, the drive force transmission unit, the linear motion mechanism unit, and the drive stop unit. The drive force transmission unit has a rotating shaft of the motor, a drive gear provided on the rotating shaft, and a group of transmission gears connected to the drive gear that transmit the rotational driving force of the drive gear to the linear motion mechanism unit. When not in operation, the drive stop unit stops the driving of the drive force transmission unit.

[0007] Furthermore, the drive stop unit may include a gear member provided in the drive force transmission unit and a key member provided to mesh with the gear member, thereby fixing the gear member when the gear member and the key member mesh, and stopping the drive of the drive force transmission unit. Furthermore, the drive stop unit may include a disk member having an insertion hole and a pin member provided in the drive force transmission unit, wherein the pin member is inserted into the insertion hole of the disk member to fix the disk member and stop the drive of the drive force transmission unit. Furthermore, the drive stop unit may have a movable disc member provided in the drive force transmission unit and a fixed disc member provided opposite to the movable disc member and capable of contacting the movable disc member, wherein the movable disc member has a plurality of convex portions on the surface facing the fixed disc member, and the fixed disc member has concave portions on the surface facing the movable disc member into which the convex portions can be fitted, and the convex portions of the movable disc member fit into the concave portions of the fixed disc member, fixing the movable disc member and stopping the drive of the drive force transmission unit. [Effects of the Invention]

[0008] The linear actuator according to this invention comprises a drive force transmission unit that transmits the driving force of a motor, a linear motion mechanism unit that moves in a straight line by the driving force transmitted by the drive force transmission unit, and a drive stop unit coupled to the drive force transmission unit that stops the driving of the drive force transmission unit. The drive force transmission unit has a motor rotation shaft, a drive gear provided on the rotation shaft, and a group of transmission gears connected to the drive gear that transmit the rotational driving force of the drive gear to the linear motion mechanism unit. When not in operation, the drive stop unit stops the driving of the drive force transmission unit, so the position of the output shaft of the linear motion mechanism unit can be reliably maintained when not in operation. [Brief explanation of the drawing]

[0009] [Figure 1] This is a front cross-sectional view of a linear actuator according to Embodiment 1 of the present invention. [Figure 2] Figure 1 is a schematic diagram of the drive force transmission section when the linear actuator shown is cut along line AA. [Figure 3] Figure 2 is a schematic diagram of the drive stop unit. [Figure 4] This is a schematic diagram of the drive stop unit of Embodiment 2 of the present invention. [Figure 5] This is a schematic diagram showing the drive stop unit of Embodiment 3 of the present invention in the release position. [Figure 6] This is a schematic diagram showing the drive stop unit of Embodiment 3 of the present invention in a fixed position. [Modes for carrying out the invention]

[0010] Embodiment 1. Hereinafter, Embodiment 1 of the present invention will be described with reference to the accompanying drawings. Figure 1 is a front cross-sectional view of the linear actuator of Embodiment 1. The linear actuator 1 is provided with a ball screw 20 having an output shaft 21 that is extendable and retractable along the axial direction indicated by arrow X, a nut 22 connected to the output shaft 21, and a screw shaft 23 that is screwed into the nut 22 and mounted so as to be rotatable about the axis. The ball screw 20 constitutes a linear motion mechanism, and as the screw shaft 23 rotates about the axis, the nut 22 moves along the axial direction, and the output shaft 21 connected to the nut 22 moves linearly along the axial direction.

[0011] Furthermore, the linear actuator 1 is equipped with a drive force transmission unit 30 that transmits driving force to the screw shaft 23, a motor 40 that generates driving force, and a control board 50 that supplies and controls driving power to the motor 40 and a drive stop unit 60 (described later), all of which are provided parallel to the axial direction of the ball screw 20. The motor 40 incorporates a brake shoe and a friction brake device (not shown) having a brake shoe and a friction member, and can brake the rotating shaft 41 by pressing the brake shoe against the friction member.

[0012] The control board 50 is connected to an external power supply unit (not shown). The drive force transmission unit 30 has a rotating shaft 41 of the motor 40, a drive gear 31 provided on the rotating shaft 41, and a group of transmission gears 32 which consists of multiple gears and transmits the driving force transmitted from the drive gear 31 to the screw shaft 23 of the ball screw 20 at an appropriate rotational speed and torque. A drive stop unit 60 is also provided at the location where the drive force transmission unit 30 is located to stop the drive of the drive force transmission unit 30. The ball screw 20, drive force transmission unit 30, motor 40, control board 50, and drive stop unit 60 are housed in the case 10.

[0013] Figure 2 is a schematic diagram of the drive force transmission section 30 when the linear actuator 1 shown in Figure 1 is cut along line AA. In Figure 2, details such as the teeth of each gear, the shaft, and a part of the screw shaft 23 are omitted. The drive force transmission section 30 includes the rotating shaft 41 (not shown) of the motor 40, a drive gear 31, and a transmission gear group 32.

[0014] The transmission gear group 32 includes a first gear 33 meshing with the drive gear 31, a second gear 34 coaxially connected to the first gear 33 via a shaft, a third gear 35 meshing with the second gear 34, a fourth gear 36 coaxially connected to the third gear 35 via a shaft, and a fifth gear 37 meshing with the fourth gear. The fifth gear 37 meshes with a screw shaft gear 23a formed on the outer diameter portion of the reduced diameter section of the screw shaft 23 of the ball screw 20.

[0015] The drive stop unit 60 has a lock gear 61 coaxially connected to the fourth gear 36 via a shaft, and a key 62 formed to engage with the teeth of the lock gear 61. The lock gear 61 constitutes a gear member, and the key 62 constitutes a key member.

[0016] Figure 3 is a schematic diagram of the drive stop unit 60 shown in Figure 2. The lock gear 61 has teeth 63 and tooth grooves 64 between each tooth of the teeth 63. The key 62 has a rod-like shape that can rotate along the direction of arrow B around a key shaft 66 provided at one end. The key 62 also has a hook portion 65 at the other end. Furthermore, the key 62 is biased by a spring 67 to rotate to a fixed position C in which the hook portion 65 is inserted into the tooth groove 64. That is, when the key 62 is in the fixed position C, the hook portion 65 and the teeth 63 can engage. A key drive motor 68 that drives the key 62 is connected to the key shaft 66. When driven, the key drive motor 68 rotates the key 62 to the release position D shown by the dashed line. In the release position D, the hook portion 65 is separated from the teeth 63. For example, a stepping motor or the like can be used as the key drive motor 68.

[0017] The hook portion 65 is inserted into the tooth groove 64 and meshes therewith, so that the locking gear 61 is fixed (locked) by the key 62 and stops rotating. Then, when the locking gear 61 is fixed, the fourth gear 36 (see FIG. 2) connected to the locking gear 61 via a shaft is fixed and stops rotating. As a result, the transmission gear group 32 including the fourth gear 36 is fixed and stops rotating, so that the screw shaft 23 having the screw shaft gear 23a shown in FIG. 1 does not rotate, and the drive of the ball screw 20 of the linear actuator 1 stops.

[0018] Next, the operation of the linear actuator 1 according to the first embodiment will be described. First, the connection between the external power supply device and the control board 50 of the linear actuator 1 is disconnected, and the operation in the non-operating state where no power is supplied to the linear actuator 1 will be described. When the linear actuator 1 shown in FIG. 1 is in the non-operating state, the friction brake device built in the motor 40 brakes the rotating shaft 41 of the motor 40.

[0019] Also, at this time, the key drive motor 68 of the drive stop portion 60 shown in FIG. 3 is in a non-driven state. Therefore, the key 62 is biased by the spring 67 provided on the key shaft 66 in the direction in which the hook portion 65 abuts against the tooth portion 63 and is located at the fixed position C, and the hook portion 65 of the key 62 is inserted into the tooth groove 64, and the hook portion 65 of the key 62 and the tooth portion 63 of the locking gear 61 are meshed.

[0020] In this state, since the locking gear 61 is fixed by the key 62 so as not to rotate, the fourth gear 36 connected to the locking gear 61 via a shaft is fixed. As a result, the first gear 33, the second gear 34, the third gear 35, and the fifth gear 37 that mesh directly or indirectly with the fourth gear 36 of the transmission gear group 32 shown in FIG. 2 are fixed and do not rotate. Therefore, the screw shaft 23 (see FIG. 1) having the screw shaft gear 23a of the ball screw 20 is also fixed and does not rotate, and the output shaft 21 is held at the current position and locked.

[0021] Next, we will describe the operation when the linear actuator 1 is powered by connecting an external power supply to the control board 50 of the linear actuator 1. When the linear actuator 1 is operated, the control board 50 drives the key drive motor 68 shown in Figure 3 to move the key 62 to the release position D. As a result, the hook portion 65 of the key 62 separates from the teeth portion 63 of the lock gear 61, releasing the lock gear 61 from its fixed position and making it rotatable. Therefore, the fourth gear 36, which is connected to the lock gear 61 via a shaft as shown in Figure 2, also becomes rotatable.

[0022] Next, with the lock gear 61 rotatable, the control board 50 releases the friction brake on the motor 40 and drives the motor 40. The driving force of the motor 40 is transmitted from the drive gear 31 to the first gear 33, second gear 34, third gear 35, fourth gear 36, and fifth gear 37 of the transmission gear group 32, causing the screw shaft gear 23a, which is meshed with the fifth gear 37, to rotate. As a result, the screw shaft 23 shown in Figure 1 rotates, the output shaft 21 extends and retracts, and the linear actuator 1 operates.

[0023] Next, when the linear actuator 1 has finished operating and the connection between the external power supply and the control board 50 is disconnected to return it to a non-operating state, the rotation shaft 41 is braked by the friction brake device of the motor 40. Next, the key drive motor 68 shown in Figure 3 becomes non-operating. As a result, the hook portion 65 of the key 62, which is biased to the fixed position C by the spring 67, engages with the tooth groove 64 of the lock gear 61, fixing the lock gear 61. Also, if the hook portion 65 contacts the peaks of the teeth 63 of the lock gear 61, the lock gear 61 then rotates, causing the hook portion 65 to engage with the tooth groove 64 and fix the lock gear 61. Thus, the fourth gear 36 is fixed, and the first gear 33, second gear 34, third gear 35, and fifth gear 37 are also fixed, and the screw shaft 23 and output shaft 21 (see Figure 1) are held in their current positions and locked.

[0024] Conventional linear actuators used friction brakes installed on the motor's rotating shaft or the transmission gear group to brake the motor's rotating shaft or the transmission gear group when not in operation, thereby holding the ball screw's output shaft in its current position. However, due to aging or other factors affecting the brake disc, brake shoe, or friction members of the friction brake system, the braking force of the friction brake system may decrease, making it impossible to reliably hold the output shaft in its current position against external forces or gravity.

[0025] In another example of a conventional linear actuator, a worm gear was used in the drive force transmission section that transmits the motor's driving force to the screw shaft of a ball screw, and the output shaft was held in place when not in operation by self-locking due to the frictional force of the worm gear. In yet another example of a conventional linear actuator, a jackscrew mechanism was used to extend and retract the output shaft instead of a ball screw, and the output shaft was held in place when not in operation by the frictional force of the jackscrew mechanism. However, linear actuators using worm gears or jackscrew mechanisms had the problem of reduced efficiency in transmitting the motor's driving force to the output shaft, resulting in reduced energy efficiency during normal operation.

[0026] In contrast, the linear actuator 1 of this embodiment 1 has the advantage that even if the braking force of the friction brake device of the motor 40 decreases, or if a large external force is applied to the output shaft 21 and a torque greater than the braking force of the friction brake is applied to the rotating shaft 41 of the motor 40, causing the friction brake device to slip, the key 62 engages with the lock gear 61 when not in operation, fixing the lock gear 61, thereby fixing each gear of the transmission gear group 32 and the screw shaft 23, and ensuring that the output shaft 21 is reliably held in its current position. Furthermore, the linear actuator 1 of this embodiment 1 does not use mechanisms with low transmission efficiency such as worm gears or jackscrew mechanisms, thus having the advantage of avoiding a decrease in energy efficiency during normal operation.

[0027] As described above, the linear actuator 1 of this embodiment 1 comprises a drive force transmission unit 30 that transmits the driving force of a motor 40, a ball screw 20 that moves linearly by the driving force transmitted by the drive force transmission unit 30, a drive stop unit 60 coupled to the drive force transmission unit 30 that stops the driving of the drive force transmission unit 30, and a case 10 that houses the motor 40, the drive force transmission unit 30, the ball screw 20, and the drive stop unit 60. The drive force transmission unit 30 has a rotating shaft 41 of the motor 40, a drive gear 31 provided on the rotating shaft 41, and a group of transmission gears 32 connected to the drive gear 31 that transmit the rotational driving force of the drive gear 31 to the ball screw 20. When not in operation, the drive stop unit 60 stops the driving of the drive force transmission unit 30, so the position of the output shaft 21 of the ball screw 20 can be reliably maintained when not in operation.

[0028] Furthermore, the drive stop unit 60 has a lock gear 61 provided on the drive force transmission unit 30 and a key 62 provided so as to be able to mesh with the lock gear 61. When the lock gear 61 and the key 62 mesh, the lock gear 61 is fixed and the drive of the drive force transmission unit 30 is stopped. Thus, with a simple configuration, the position of the output shaft 21 can be reliably maintained when not in operation.

[0029] In this embodiment 1, the key drive motor 68 is a stepping motor, but other types of motors may be used. Alternatively, a drive element such as a solenoid may be used instead of the key drive motor 68.

[0030] Furthermore, in this embodiment 1, the lock gear 61 was coaxially connected to the fourth gear 36 via a shaft, but it is not limited to this. The lock gear 61 may be provided via a shaft to at least one of the drive gear 31, the first gear 33, the second gear 34, the third gear 35, the fourth gear 36, and the fifth gear 37, or it may be provided to mesh with at least one of the drive gear 31, the first gear 33, the second gear 34, the third gear 35, the fourth gear 36, and the fifth gear 37, or it may be provided on the rotating shaft 41 of the motor 40 and further arranged to mesh with and be fixed to the key 62.

[0031] Embodiment 2. Next, a linear actuator according to Embodiment 2 of the present invention will be described. In the embodiments described below, the same reference numerals as those in Figures 1 to 3 are for the same or similar components as those in Embodiment 1, so a detailed explanation of them will be omitted. The lever device according to Embodiment 2 is configured with a lock disk and a lock pin as the drive stop unit, compared to Embodiment 1. Figure 4 is a schematic diagram of the drive stop unit 70 of this second embodiment. The drive stop unit 70 has a disc-shaped lock disc 71 and a cylindrical lock pin 72 that are coaxially connected to the fourth gear 36 (see Figure 2) via a shaft (not shown). The lock disc 71 is an elongated hole that bends and extends along the circumferential direction and has a total of five disc holes 73 provided at equal angular intervals. The radial width of the disc holes 73 is formed to be slightly larger than the diameter of the lock pin 72.

[0032] The lock pin 72 is positioned along a direction parallel to the central axis of the lock disk 71 so as to be able to be inserted into or removed from the disk hole 73. A solenoid (not shown) is provided as a driving means to move the lock pin 72 to a fixed position, which is the position in which it is inserted into the disk hole 73, and to a released position, which is the position in which it is removed from the disk hole 73. The lock disk 71 constitutes a disk member, the lock pin 72 constitutes a pin member, and the disk hole 73 constitutes an insertion hole. The other configurations are the same as in Embodiment 1.

[0033] Next, the operation of the linear actuator 1 according to this second embodiment will be described. First, we will describe the operation when the connection between the external power supply and the control board 50 of the linear actuator 1 is disconnected and the linear actuator 1 is in a non-operating state. When the linear actuator 1 shown in Figure 1 is in a non-operating state, the rotation shaft 41 is braked by the friction brake device of the motor 40, and the lock pin 72 shown in Figure 4 is in a fixed position inserted into the disk hole 73, and the lock pin 72 fixes the lock disk 71 so that it does not rotate more than the circumferential length of the disk hole 73.

[0034] In this state, the locking pin 72 fixes the locking disk 71 so that it can only rotate a short distance equal to the circumferential length of the disk hole 73, and the fourth gear 36 (see Figure 2), which is connected to the locking disk 71 via a shaft, is substantially fixed. As a result, the first gear 33, second gear 34, third gear 35, and fifth gear 37 are substantially fixed and do not rotate, and the screw shaft 23, which has the screw shaft gear 23a, is also substantially fixed and does not rotate, so the screw shaft 23 and output shaft 21 of the ball screw 20 shown in Figure 1 are held in their current positions and locked.

[0035] Next, the operation when the external power supply and the control board 50 are connected and the linear actuator 1 is operated will be described. When the linear actuator 1 is driven, the control board 50 drives a solenoid to move the lock pin 72 shown in Figure 4 to the release position. As a result, the lock pin 72 is removed from the disk hole 73, the lock disk 71 is released, and the lock disk 71 becomes rotatable. Therefore, the fourth gear 36 connected to the lock disk 71 via a shaft also becomes rotatable.

[0036] Next, with the lock disk 71 rotatable, the control board 50 releases the friction brake device of the motor 40 and drives it. The driving force of the motor 40 is transmitted from the drive gear 31 shown in Figure 2 to the first gear 33, second gear 34, third gear 35, fourth gear 36, and fifth gear 37 of the transmission gear group 32, causing the screw shaft gear 23a, which is meshed with the fifth gear 37, to rotate. As a result, the screw shaft 23 shown in Figure 1 rotates, the output shaft 21 extends and retracts, and the linear actuator 1 operates.

[0037] Next, when the linear actuator 1 has finished operating and the connection between the external power supply and the control board 50 is disconnected, the rotation shaft 41 is braked by the friction brake device of the motor 40. Then, the solenoid is no longer driven, and the lock pin 72 shown in Figure 4 is inserted into the disk hole 73, and the lock disk 71 is substantially fixed. Also, if the lock pin 72 comes into contact with the portion of the lock disk 71 between adjacent disk holes 73, the lock disk 71 rotates thereafter, causing the lock pin 72 to be inserted into the disk hole 73, and the lock disk 71 is substantially fixed. As a result, the first gear 33, second gear 34, third gear 35, and fifth gear 37 are substantially fixed, and the screw shaft 23 and output shaft 21 of the ball screw 20 are held in their current positions and locked.

[0038] Thus, in this embodiment 2, the linear actuator 1 has a drive stop unit 70 which includes a lock disk 71 having a disk hole 73 and a lock pin 72 that is insertable into the disk hole 73, provided in the drive force transmission unit 30. When the lock pin 72 is inserted into the disk hole 73 of the lock disk 71, the lock disk 71 is fixed and the drive of the drive force transmission unit 30 is stopped. Therefore, similar to embodiment 1, the position of the output shaft 21 can be reliably maintained when not in operation with a simple configuration.

[0039] In this embodiment 2, the lock disk 71 has five disk holes 73 and one lock pin 72, but it is not limited to this, and the number of disk holes 73 and the number of lock pins may be any appropriate number.

[0040] Furthermore, in this second embodiment, a solenoid was used as the driving means for the lock pin 72, but the driving means for the lock pin 72 is not limited to this, and various known motors and actuators may be used.

[0041] Furthermore, in this embodiment 2, the lock disk 71 was coaxially connected to the fourth gear 36 via a shaft, but it is not limited to this. The lock disk 71 may be attached via a shaft to at least one of the drive gear 31, the first gear 33, the second gear 34, the third gear 35, the fourth gear 36, and the fifth gear 37, or at least to the rotating shaft 41 of the motor 40, and further arranged so that a lock pin 72 can be inserted and fixed to it.

[0042] Embodiment 3. Next, Embodiment 3 of the present invention will be described. In Embodiment 3, the drive stop unit is formed by two lock disks, compared to Embodiment 1. Figure 5 is a schematic diagram showing the drive stop unit of Embodiment 3 of the present invention in the release position. The drive stop unit 80 includes a first lock disk 81 and a second lock disk 82 provided opposite the first lock disk 81. The first lock disk 81 has a plurality of teeth 83 that protrude axially along one surface and are arranged at equal angular intervals along the outer diameter, and tooth grooves 84 formed between each tooth 83. The second lock disk 82 has the same shape as the first lock disk 81, and the first lock disk 81 and the second lock disk 82 are arranged with their surfaces having teeth 83 facing each other.

[0043] The teeth 83 of the first lock disc 81 and the second lock disc 82 are formed in a columnar shape with a taper, where the radially outer and inner sides are arc-shaped when viewed from a direction perpendicular to the surface having the teeth 83, and the width narrows from the radially outer side to the inner side. The teeth 83 and tooth grooves 84 of the first lock disc 81 are formed to mesh with the tooth grooves 84 and teeth 83 of the second lock disc 82, respectively.

[0044] The first lock disc 81 is coaxially connected to the fourth gear 36 (see Figure 2) via a shaft 85. The second lock disc is connected to a solenoid (not shown) via a shaft 85. Figure 6 is a schematic diagram showing the drive stop unit 80 of Embodiment 3 in a fixed position. The solenoid connected to the second lock disc 82 moves the second lock disc 82 along the direction in which the shaft 85 extends, from a release position where the first lock disc 81 and the second lock disc 82 are separated, to a fixed position where the teeth 83 of the first lock disc 81 and the teeth 83 of the second lock disc 82 mesh. The first lock disc 81 is a movable disc member that can rotate in the circumferential direction, and the second lock disc 82 is a fixed disc member that does not rotate in the circumferential direction. The teeth 83 constitute a convex portion, and the tooth grooves 84 constitute a concave portion. The second lock disc 82 is fixed so as not to rotate in the circumferential direction. The other configurations are the same as in Embodiment 1.

[0045] Next, the operation of the linear actuator 1 according to this third embodiment will be described. First, we will describe the operation when the connection between the external power supply and the control board 50 of the linear actuator 1 is disconnected and the linear actuator 1 is in a non-operating state. When the linear actuator 1 shown in Figure 1 is in a non-operating state, the rotation shaft 41 is braked by the friction brake device of the motor 40, and as shown in Figure 6, the second lock disk 82 is pushed out by the solenoid towards the first lock disk 81 to a fixed position, and the teeth 83 of the second lock disk 82 mesh with the teeth 83 of the first lock disk. That is, the teeth 83 of the second lock disk 82 are inserted into the tooth grooves 84 of the first lock disk 81, and the teeth 83 of the first lock disk 81 are inserted into the tooth grooves 84 of the second lock disk 82.

[0046] In this state, the second lock disk 82 is fixed so that it cannot rotate in the circumferential direction, and the first lock disk 81 is fixed in place by the second lock disk 82 so that it cannot rotate. As a result, the fourth gear 36 (see Figure 2), which is connected to the first lock disk 81 via the shaft 85, is fixed. As a result, the first gear 33, second gear 34, third gear 35, and fifth gear 37 are fixed and do not rotate, and the screw shaft 23 having the screw shaft gear 23a is also fixed and does not rotate, so the output shaft 21 of the ball screw 20 is held in its current position and locked.

[0047] Next, we will describe the operation when the linear actuator 1 is operated after the external power supply is connected to the control board 50 of the linear actuator 1. When the linear actuator 1 is operated, the control board 50 drives a solenoid to move the second lock disk 82 to the release position along the direction of arrow E, which is along the axial direction of the shaft 85, as shown in Figure 5. As a result, the first lock disk 81 is released from its fixed position and becomes rotatable. Therefore, the fourth gear 36, which is connected to the first lock disk 81 via the shaft, also becomes rotatable.

[0048] Next, with the first lock disk 81 rotatable, the control board 50 releases the friction brake device of the motor 40 and drives it. The driving force of the motor 40 is transmitted from the drive gear 31 shown in Figure 2 to the first gear 33, second gear 34, third gear 35, fourth gear 36, and fifth gear 37 of the transmission gear group 32, causing the screw shaft gear 23a, which is meshed with the fifth gear 37, to rotate. As a result, the screw shaft 23 shown in Figure 1 rotates, the output shaft 21 extends and retracts, and the linear actuator 1 operates.

[0049] When the linear actuator 1 is no longer driven and the connection between the external power supply and the control board 50 is disconnected, the rotation shaft 41 is braked by the friction brake device of the motor 40. Next, as shown in Figure 6, the solenoid moves the second lock disk 82 in the opposite direction to the direction of arrow E, and the teeth 83 of the first lock disk 81 are inserted into the tooth grooves 84 of the second lock disk 82. As the teeth 83 of the second lock disk 82 are inserted into the tooth grooves 84 of the first lock disk 81, the teeth 83 of the first lock disk 81 and the teeth 83 of the second lock disk 82 mesh, and the first lock disk 81 is fixed in place. Furthermore, when the tips of the teeth 83 of the first lock disk 81 and the second lock disk 82 come into contact with each other, the first lock disk 81 rotates, causing the teeth 83 of the first lock disk 81 to be inserted into the tooth grooves 84 of the second lock disk 82, and the teeth 83 of the second lock disk 82 to be inserted into the tooth grooves 84 of the first lock disk 81, thereby fixing the first lock disk 81 in place. As a result, the screw shaft 23 and output shaft 21 of the ball screw 20 are held in their current positions and locked.

[0050] As described above, in this embodiment 3, the linear actuator has a drive stop unit 80 which includes a first lock disk 81 provided on the drive force transmission unit 30 and a second lock disk 82 provided opposite to the first lock disk 81 and capable of contacting the first lock disk 81. The first lock disk 81 has a plurality of teeth 83 on the side facing the second lock disk 82, and the second lock disk 82 has tooth grooves 84 on the side facing the first lock disk 81 into which the teeth 83 can be fitted. When the teeth 83 of the first lock disk 81 are fitted into the tooth grooves 84 of the second lock disk 82, the first lock disk 81 is fixed and the drive of the drive force transmission unit 30 is stopped. Thus, similar to embodiment 1, the position of the output shaft 21 can be reliably maintained when not in operation with a simple configuration.

[0051] In this embodiment 3, the teeth 83 of the first lock disc 81 and the second lock disc 82 had a columnar shape with an arc shape on the radially outer and inner sides, and a taper that narrows from the radially outer side to the inner side when viewed from a direction perpendicular to the surface having the teeth 83. However, the shape of the teeth is not limited to this, and may be any shape that can fit into the tooth groove. For example, the teeth may have a triangular shape when viewed from the radial direction of the first lock disc 81 and the second lock disc 82.

[0052] Furthermore, in this embodiment 3, a solenoid was used as the means of moving the second lock disk 82, but the means of moving the second lock disk 82 is not limited to this, and various known motors and actuators may be used.

[0053] Furthermore, in this embodiment 3, the first lock disk 81 was coaxially connected to the fourth gear 36 via a shaft, but it is not limited to this. The first lock disk 81 may be attached via a shaft to at least one of the drive gear 31, first gear 33, second gear 34, third gear 35, fourth gear 36, and fifth gear 37, or at least attached to the rotating shaft 41 of the motor 40 and arranged to be further fixed by the second lock disk 82. [Explanation of Symbols]

[0054] 10 Case (Case part) 20. Ball screw (linear motion mechanism) 30 Power transmission section 31 Drive Gear 32 Transmission gear group 40 motors 41 Rotation axis 60 Drive stop unit 61 Locking gear (gear component) 62 keys (key components) 70 Drive stop unit 71. Lock disc (disc component) 72 Lock pin (pin component) 73 Disc holes (insertion holes) 80 Drive stop unit 81. First locking disk (movable disk component) 82 Second lock disk (fixed disk component) 83 Tooth part (convex part) 84 Tooth groove (concave part)

Claims

1. Motor (40) and A drive force transmission unit (30) that transmits the driving force of the motor (40), A linear motion mechanism (20) that moves in a straight line by the driving force transmitted by the driving force transmission unit (30), A drive stop unit (60) is coupled to the drive force transmission unit (30) and stops the driving of the drive force transmission unit (30), The motor (40), the drive force transmission unit (30), the linear motion mechanism unit (20), and the drive stop unit (60) are housed in a case (10) Equipped with, The aforementioned drive force transmission unit (30) is The rotating shaft (41) of the motor (40) and The drive gear (31) provided on the rotating shaft (41), A group of transmission gears (32) connected to the drive gear (31) transmits the rotational driving force of the drive gear (31) to the linear motion mechanism. A linear actuator having

2. The drive stop unit (60) is A gear member (61) provided in the aforementioned drive force transmission unit (30), A key member (62) is provided so as to be able to mesh with the gear member (61) and It has, The linear actuator according to claim 1, wherein the gear member (61) and the key member (62) mesh together, fixing the gear member (61) and stopping the driving of the drive force transmission unit (30).

3. The drive stop unit (70) is A disk member (71) having an insertion hole (73) is provided in the drive force transmission unit (30), A pin member (72) is provided so as to be insertable into the insertion hole (73) and It has, The linear actuator according to claim 1, wherein the pin member (72) is inserted into the insertion hole (73) of the disk member (71) to fix the disk member (71), and the driving of the drive force transmission unit (30) is stopped.

4. The drive stop unit (80) is, A movable disc member (81) is provided in the drive force transmission section, A fixed disk member (82) is provided opposite to the movable disk member (81) and is capable of contacting the movable disk member (81). It has, The movable disk member (81) has a plurality of convex portions (83) on the surface facing the fixed disk member (82), The fixed disk member (82) has a concave portion (84) on the side facing the movable disk member (81) into which the convex portion (83) can be fitted. The linear actuator according to claim 1, wherein the convex portion (83) of the movable disk member (81) fits into the concave portion (84) of the fixed disk member (82), fixing the movable disk member (81) and stopping the driving of the drive force transmission unit (30).

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