Power transmission device

Abstract

The present disclosure provides a power transmission device capable of suppressing the occurrence of a jerking phenomenon and reducing a torque required for unlocking. The power transmission device includes a fixing member, an output shaft having a concave surface, an input shaft having a pressing portion, a pair of first rotating bodies disposed on both sides of the pressing portion in a circumferential direction, and a pair of second rotating bodies disposed between the first rotating bodies and the pressing portion. The concave surface has a bottom surface and a pair of pressed surfaces. The bottom surface has: a cam surface on which the first rotating body is disposed radially outward; and a guide surface on which the second rotating body is disposed radially outward. The distance between the cam surface and the inner peripheral surface increases as the cam surface approaches the pressed surface. A distance between a portion of the cam surface close to the guide surface and the inner peripheral surface is smaller than a diameter of the first rotating body. The second rotating body is sandwiched between the first rotating body, the guide surface, and the pressing portion. The pressing portion presses the second rotating body between the first rotating body and the guide surface when the pressing portion moves outward in the circumferential direction from a state in which the pressing portion is disposed in the central portion in the circumferential direction.

Description

Technical Field

[0001] This disclosure relates to power transmission devices. Background Technology

[0002] A power transmission device is a device that transmits torque generated by a motor or the like. Such a power transmission device is used, for example, to drive the arm of an industrial robot. The power transmission device has an input shaft for receiving torque and an output shaft for outputting torque. An object to be driven is connected to the output shaft. Therefore, sometimes the weight of the object (hereinafter referred to as an external force) acts on the output shaft. In this case, when the output shaft rotates due to the external force, the position of the object is not maintained. Therefore, in the power transmission device of Patent Document 1, even if an external force acts on the output shaft, the output shaft will not rotate.

[0003] Details of the power transmission device in Patent Document 1 will be described below. The power transmission device in Patent Document 1 includes: an annular fixed member; an output shaft having a cam surface facing the inner circumference of the fixed member; a cylindrical roller disposed between the fixed member and the cam surface; and an input shaft having a pressing portion disposed circumferentially along the cylindrical roller. When an external force is applied to the output shaft, causing it to rotate, the cylindrical roller is clamped between the fixed member and the cam surface, restricting the rotation of the output shaft. Furthermore, when torque is input to the input shaft, the pressing portion presses against the cylindrical roller. This causes the cylindrical roller clamped between the fixed member and the cam surface to move, releasing the locking state.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 4621156

[0007] Furthermore, at the start of torque input to the input shaft, an external force in the same direction as the torque sometimes acts on the output shaft. Therefore, even if the cylindrical roller clamped between the fixed member and the cam surface is pressed and moved by the pressing part, there is a possibility that the cam surface will move in the same direction, causing the cylindrical roller to be clamped between the fixed member and the cam surface again. That is, there is a possibility that the unlocked and locked states alternate repeatedly, making the rotation of the input and output members intermittent. Therefore, it is desirable to develop a power transmission device in which the phenomenon of repeated unlocking and locking states (hereinafter referred to as "jerkiness") is less likely to occur. In addition, it has been desirable to reduce the torque used for unlocking. Summary of the Invention

[0008] This disclosure is made in view of the above, and its object is to provide a power transmission device that can suppress the occurrence of jerking and reduce the torque required for unlocking.

[0009] Solution for solving the problem

[0010] To achieve the above objectives, a power transmission device according to one embodiment of this disclosure comprises: an annular fixed member having an inner circumferential surface; an output shaft having an outer circumferential surface facing the inner circumferential surface and a concave surface recessed radially inward from the outer circumferential surface; an input shaft having a pressing portion accommodated within the concave surface; a pair of first rotating bodies accommodated within the concave surface and disposed on opposite sides of the pressing portion in the circumferential direction; and a pair of second rotating bodies with a diameter smaller than that of the first rotating bodies and disposed between the first rotating bodies and the pressing portion. The concave surface has: a bottom surface extending circumferentially and facing the inner circumferential surface radially; and a pair of pressed surfaces extending radially outward from both ends of the bottom surface in the circumferential direction. The bottom surface has: a pair of cam surfaces for the first rotating bodies to be disposed radially outward; and a pair of guide surfaces for the second rotating bodies to be disposed radially outward. The distance between the cam surfaces and the inner circumferential surface gradually increases as they approach the pressed surfaces. The distance between the portion of the cam surface approaching the guide surface and the inner circumferential surface is smaller than the diameter of the first rotating body. The distance between the portion of the cam surface near the pressed surface and the inner circumferential surface is greater than the diameter of the first rotating body. The second rotating body is sandwiched between the first rotating body, the guide surface, and the pressing portion. When the pressing portion moves circumferentially outward from its position at the center of the concave surface, it presses the second rotating body between the first rotating body and the guide surface.

[0011] Invention Effects

[0012] According to the power transmission device disclosed herein, the occurrence of jerking is suppressed, and the torque required for unlocking is also reduced. Attached Figure Description

[0013] Figure 1 This is a schematic diagram obtained by viewing the power transmission device of Embodiment 1 from the axial direction.

[0014] Figure 2 yes Figure 1 Sectional view along line II-II.

[0015] Figure 3 It is Figure 1 The magnified image is obtained by magnifying one of the concave surfaces.

[0016] Figure 4 It is Figure 3 An enlarged image obtained by magnifying a portion of it.

[0017] Figure 5 This is a diagram illustrating the operating state of the power transmission device in Embodiment 1, specifically a diagram showing the start time of torque input.

[0018] Figure 6 This is a diagram illustrating the operating state of the power transmission device in Embodiment 1, specifically a diagram showing the time point at which the locked state is released.

[0019] Figure 7 This is a diagram illustrating the operating state of the power transmission device in Embodiment 1, specifically a diagram showing the state in which the first roller contacts the pressed surface.

[0020] Figure 8 This is a diagram illustrating the operating state of the power transmission device in Embodiment 1, specifically a diagram showing the time point at which the first roller begins to return in the second rotational direction.

[0021] Figure 9 This is a diagram showing the time point at which torque (first rotation direction) begins to be input to the input shaft in the power transmission device of Embodiment 1 when an external force (first rotation direction) acts on the output shaft.

[0022] Figure 10 This is a diagram showing the time point at which torque (in the first rotation direction) begins to be input to the input shaft in the power transmission device of Embodiment 1 when an external force (in the second rotation direction) acts on the output shaft.

[0023] Figure 11 This is an enlarged view obtained by magnifying one of the concave surfaces of the power transmission device in Modified Example 1.

[0024] Figure 12 This is a diagram showing the state in which the pressing part presses the pressed surface through the first roller in the power transmission device of Modified Example 1.

[0025] Figure 13 This is an enlarged view obtained by magnifying one of the concave surfaces of the power transmission device in Modified Example 2.

[0026] Figure 14 This is a diagram showing the state in which the pressing part presses the pressed surface through the second roller and the first roller in the power transmission device of Modified Example 2.

[0027] Figure 15 This is a partial cross-sectional view obtained by magnifying the area near the pressed surface in the power transmission device of Modified Example 3.

[0028] Figure 16 This is an enlarged view obtained by magnifying one of the concave surfaces of the power transmission device in Modified Example 4.

[0029] Figure 17 This is a schematic diagram illustrating the configuration of the drive unit in Embodiment 2.

[0030] Figure 18 This is a schematic diagram illustrating the structure of the drive unit in Modified Example 5.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1: Fixed component; 2: Output shaft; 3: Input shaft; 4: First roller (first rotating body); 5: Second roller (second rotating body); 10: Inner circumferential surface; 20: Inner ring portion; 23: Concave surface; 24: Bottom surface; 25: Pressed surface; 26: Central surface; 27: Cam surface; 28, 28B: Guide surface; 30: Torque transmission part; 34: Pressing part; 35, 35A: Side surface; 37: Pressing surface for the second rotating body; 50: Helical spring; 51, 51C: Hole; 100, 100A, 100B, 100C, 100D: Power transmission device; 351: Inner side surface; 352: Outer side surface. Detailed Implementation

[0033] The embodiments for implementing this disclosure will be described in detail with reference to the accompanying drawings. This disclosure is not limited to the contents described below. Furthermore, the constituent elements described below include those readily conceived by those skilled in the art, and substantially the same constituent elements. Moreover, the constituent elements described below can be appropriately combined.

[0034] (Implementation Method 1)

[0035] Figure 1 This is a schematic diagram obtained by viewing the power transmission device of Embodiment 1 from the axial direction. Figure 2 yes Figure 1 Sectional view along line II-II. (See example) Figure 1 As shown, the power transmission device 100 of Embodiment 1 includes a fixed member 1, an output shaft 2, an input shaft 3, a plurality of first rollers (first rotating bodies) 4, and a plurality of second rollers (second rotating bodies) 5.

[0036] The fixing member 1 is an annular member. The inner circumferential surface 10 and the outer circumferential surface 11 of the fixing member 1 are formed into a circle centered on the central axis X. Hereinafter, the direction parallel to the central axis X of the inner circumferential surface 10 will be called the axial direction. The direction orthogonal to the central axis X will be called the radial direction. The direction of rotation centered on the central axis X will be called the circumferential direction.

[0037] like Figure 2 As shown, the output shaft 2 includes an inner ring portion 20 disposed inside the fixing member 1, and an output shaft body 21 protruding axially from the inner ring portion 20. Furthermore, the input shaft 3 includes a torque transmission portion 30 disposed inside the fixing member 1, and an input shaft body 31 protruding axially from the torque transmission portion 30.

[0038] Regarding the axial direction, the direction in which the input shaft body 31 protrudes when viewed from the torque transmission section 30 is referred to as the first direction X1. The direction in which the output shaft body 21 protrudes when viewed from the inner ring section 20 is referred to as the second direction X2. Furthermore, regarding the circumferential direction, such as... Figure 1 As shown, the explanation is based on the view observed from the second direction X2. Furthermore, the left-hand (counterclockwise) direction when viewed from the second direction X2 is referred to as the first rotation direction L1. The right-hand (clockwise) direction when viewed from the second direction X2 is referred to as the second rotation direction L2.

[0039] like Figure 1 As shown, the outer peripheral surface 22 of the inner ring portion 20 faces the inner peripheral surface 10 of the fixing member 1. The diameter of the outer peripheral surface 22 is approximately the same as the diameter of the inner peripheral surface 10 of the fixing member 1. Furthermore, the inner ring portion 20 is rotatably disposed on the inner peripheral side of the fixing member 1.

[0040] Three concave surfaces 23 are formed on the outer peripheral surface 22 of the inner ring portion 20, which are recessed radially inward. The pressing portion 34 of the input shaft 3 (described later), two (pair) first rollers 4 and two (pair) second rollers 5 are accommodated inside one of the concave surfaces 23.

[0041] like Figure 2 As shown, the outer diameter of the torque transmission section 30 is approximately the same as the diameter of the inner circumferential surface 10 of the fixing member 1. Furthermore, the torque transmission section 30 is rotatably disposed on the inner circumferential side of the fixing member 1. Additionally, the torque transmission section 30 has a disc-shaped disc portion 33 disposed relative to the inner ring portion 20 in a first direction X1, and a pressing portion 34 protruding from the disc portion 33 in a second direction X2.

[0042] like Figure 1 As shown, the first roller 4 and the second roller 5 are both cylindrical rollers formed in a cylindrical shape. The diameter of the first roller 4 is H1 (refer to...). Figure 1 The diameter of the second roller 5 is H2 (refer to...). Figure 1 (), which is smaller than the diameter of the first roller 4.

[0043] Figure 1 The three imaginary lines W1, W2, and W3 shown are straight lines extending radially from the central axis X, arranged at 120° intervals. The internal shape of the fixing member 1 is thus three times rotationally symmetric about the central axis X. That is, when the fixing member 1 is divided into three parts circumferentially along the imaginary lines W1, W2, and W3, the shape of one of the resulting parts is identical to the other parts. The following description will focus on one of the three parts obtained from this division.

[0044] Figure 3 It is Figure 1 The magnified image is obtained by magnifying one of the concave surfaces. Figure 3An imaginary line W4 originates from the central axis X and passes through the circumferential center of the concave surface 23. The concave surface 23 is formed as a line symmetrical about the imaginary line W4. In more detail, the concave surface 23 has a bottom surface 24 and a pair of pressed surfaces 25. The bottom surface 24 has a central surface 26 located at the circumferential center of the bottom surface 24, a pair of cam surfaces 27 located at both ends of the bottom surface 24 in the circumferential direction, and a pair of guide surfaces 28 located between the central surface 26 and the cam surfaces 27. Hereinafter, the circumferential direction in which the cam surfaces 27 are arranged when viewed from the central surface 26 is referred to as the circumferential outer direction. Furthermore, the circumferential direction in which the central surface 26 is arranged when viewed from the cam surfaces 27 is referred to as the circumferential inner direction.

[0045] The first roller 4 is positioned radially outward from the cam surface 27. The diameter M1 from the central axis X to the cam surface 27 gradually decreases as it approaches the pressed surface 25. Therefore, the distance M2 between the inner circumferential surface 10 of the fixing member 1 and the cam surface 27 gradually increases as it approaches the pressed surface 25.

[0046] When the first roller 4 moves close to the guide surface 28, it is clamped between the cam surface 27 and the inner circumferential surface 10, and the output shaft 2 is locked. That is, the distance M2 from the portion of the cam surface 27 close to the guide surface 28 to the inner circumferential surface 10 is less than the diameter H1 of the first roller 4 (refer to...). Figure 1 ).

[0047] On the other hand, when the first roller 4 moves close to the pressed surface 25, it enters a state where it is gap-fitted between the cam surface 27 and the inner circumferential surface 10, rather than being clamped between them (unlocked state). That is, the distance M2 from the portion of the cam surface 27 close to the pressed surface 25 to the inner circumferential surface 10 is greater than the diameter H1 of the first roller 4 (refer to...). Figure 1 ).

[0048] It should be noted that, in detail regarding the locked state, when the first roller 4, positioned in the first rotation direction L1, is clamped by the pressing part 34, the rotation of the output shaft 2 in the first rotation direction L1 is restricted. On the other hand, when the first roller 4, positioned in the second rotation direction L2, is clamped by the pressing part 34, the rotation of the output shaft 2 in the second rotation direction L2 is restricted.

[0049] like Figure 3 As shown, the central surface 26 is formed as a straight line orthogonal to the imaginary line W4. It should be noted that, for this disclosure, the central surface 26 may also be formed as an arc centered on the central axis X instead of a straight line.

[0050] Figure 4 It is Figure 3This is an enlarged view obtained by magnifying a portion of the image. The second roller 5 is positioned radially outward from the guide surface 28, and the second roller 5 is in contact with the guide surface 28. The guide surface 28 is located radially inward as it tends to move circumferentially outward. Therefore, as the second roller 5 moves circumferentially outward along the guide surface 28, the amount of downward sinking radially inward increases.

[0051] In addition, the shortest distance between the first roller 4 in the locked state and the guide surface 28 (refer to...) Figure 4 The shortest distance H3 is less than the diameter H2 of the second roller 5 (refer to...). Figure 1 Furthermore, the center X5 of the second roller 5 is positioned radially outward from the line representing the shortest distance H3. Additionally, when the first roller 4 moves circumferentially outward, the shortest distance H3 is as follows: Figure 4 As indicated by arrow Y, it moves radially inward (circumferentially outward). That is to say, the second roller 5 can move radially inward (circumferentially outward).

[0052] The pressed surface 25 is the surface that contacts the first roller 4. The pressed surface 25 is a straight line extending radially from its inner end 25a to its outer end 25b. Furthermore, the outer end 25b is positioned circumferentially outward than the imaginary line W5 drawn from the central axis X to the inner end 25a. That is, the pressed surface 25 is inclined circumferentially outward.

[0053] A helical spring 50, which acts as an elastic body, is provided between the pressed surface 25 and the first roller 4. The helical spring 50 is configured in a state that is shorter than its natural length. The first roller 4 is always subjected to a circumferential inward force by the helical spring 50. Therefore, even if no external force is input to the output shaft 2, the first roller 4 will be in a state (locked state) between the inner circumferential surface 10 and the cam surface 27.

[0054] A hole 51 is formed in the pressed surface 25. A portion of the coil spring 50 is accommodated in the hole 51. Furthermore, when the first roller 4 moves circumferentially outward, the coil spring 50, accommodated in the hole 51, contacts the pressed surface 25 (see reference). Figure 7 In addition, such as Figure 1 As shown, hole 51 penetrates the pressed surfaces 25 of other concave surfaces 23 located on the back side of the pressed surface 25. That is, hole 51 connects the interiors of adjacent concave surfaces 23 in the circumferential direction. A helical spring 50 applies force to the two first rollers 4.

[0055] like Figure 4 As shown, the pressing part 34 has a pair of side surfaces 35 facing outward in a circumferential direction, an inner surface 36 facing inward in a radial direction, and a pair of second rotating body pressing surfaces 37 formed at the corner where the side surfaces 35 and the inner surface 36 intersect.

[0056] The side surface 35 has an inner side surface 351 disposed radially inward with reference to the central portion of the side surface 35 in the radial direction, and an outer side surface 352 disposed radially outward. The outer side surface 352 is disposed circumferentially outward as it tends to be radially outward, and protrudes circumferentially outward than the inner side surface 351.

[0057] Figure 4 The imaginary line W6 shown is the same as the imaginary line W4 (see reference). Figure 3 The inner surface 36 extends along the imaginary line W6. The second rotating body is formed into a straight line by the pressing surface 37. With the pressing part 34 positioned at the center of the circumferential direction, the second rotating body abuts against the second roller 5 by the pressing surface 37. When the pressing part 34 moves outward in the circumferential direction, the second rotating body presses the second roller 5 by the pressing surface 37. Furthermore, the pressed second roller 5 is pressed between the first roller 4 and the guide surface 28.

[0058] Furthermore, the orientation of the pressing surface 37 of the second rotating body is such that the pressed second roller 5 moves between the first roller 4 and the guide surface 28. In this embodiment, the pressing surface 37 of the second rotating body is gradually positioned radially outward as it tends to move circumferentially outward, and is inclined relative to the imaginary line W6.

[0059] Next, the operation of the power transmission device according to Embodiment 1 will be explained. First, the initial state of the power transmission device 100 (the state in which no torque or external force is input) will be explained.

[0060] like Figure 3 As shown, a pair of first rollers 4 are pressed inward by a helical spring 50. Furthermore, the first rollers 4 are clamped between the inner circumferential surface 10 and the cam surface 27. That is to say, in the initial state, the output shaft 2 is in a locked state.

[0061] Furthermore, in the initial state, the side 35 of the pressing part 34 does not contact the first roller 4. The second rotating body of the pressing part 34 contacts the second roller 5 with the pressing surface 37. In addition, the second roller 5 abuts against the first roller 4 and the guide surface 28 respectively.

[0062] Next, the input shaft body 31 of the power transmission device 100, which is in its initial state, is used to input torque. Figure 2 The following explanation will first describe the situation where no external force is applied to the output shaft 2. Furthermore, the same operation will be performed whether the direction of the input torque is the first rotational direction L1 or the second rotational direction L2. Therefore, the following explanation will focus on the case where the torque is directed in the first rotational direction L1.

[0063] Figure 5This is a diagram illustrating the operating state of the power transmission device in Embodiment 1, specifically a diagram showing the start time of torque input. For example... Figure 5 As shown, when the torque in the first rotational direction L1 is directed towards the input shaft body 31 (refer to...) Figure 2 When the torque is input, the load A in the first rotational direction L1 is transmitted to the pressing part 34. In the initial state, the side 35 of the pressing part 34 does not abut against the first roller 4. Therefore, at the start of the torque input, the pressing part 34 does not press the first roller 4.

[0064] On the other hand, the pressing part 34 abuts against the second roller 5. Therefore, the pressing part 34 presses the second roller 5 with the pressing surface 37 via the second rotating body, and the second roller 5 receives the load B from the pressing part 34. As a result, the second roller 5 is pressed between the first roller 4 and the guide surface 28. Then, loads B1 and B2 are applied to the first roller 4 and the guide surface 28 such that they are separated from each other. When the load B1 component acting on the first roller 4 is considered, in addition to the radially outward component, a component in the first rotational direction L1 is also included.

[0065] Figure 6 This is a diagram illustrating the operating state of the power transmission device in Embodiment 1, specifically a diagram showing the time points at which the locked state is released. Therefore, as... Figure 6 As shown, the first roller 4 moves in the first rotation direction L1, thereby releasing the state (locked state) between the inner circumferential surface 10 and the cam surface 27.

[0066] In addition, the load B2 acting on the guide surface 28 (refer to) Figure 5 The load B2 includes a component in the second rotational direction L2, and the torque in the second rotational direction L2 acts on the output shaft 2. Furthermore, this torque is a load that moves the cam surface 27 relative to the first roller 4 in the second rotational direction L2. Based on the above, the load B2 includes the torque required for unlocking, thus reducing the torque required for unlocking.

[0067] Then, when the locking state is released, the pressing part 34 begins to move in the first rotational direction L1. Furthermore, the second roller 5 begins to move radially inward along the guide surface 28. Here, as the second roller 5 moves radially inward, the distance between the first roller 4 and the pressing part 34 decreases, as... Figure 6 As shown, the side 35 of the pressing part 34 abuts against the first roller 4. Therefore, after the locking state is released, the first roller 4 receives a load C from the pressing part 34, compressing the coil spring 50 while moving in the first rotational direction L1. It should be noted that for a brief period of time after the locking state is released, the first roller 4 receives a load B1 from the second roller 5 (see reference). Figure 5 ).

[0068] Figure 7This diagram illustrates the operating state of the power transmission device in Embodiment 1, specifically the state in which the first roller contacts the pressed surface. Figure 7 As shown, when the first roller 4 moves to a certain extent in the first rotational direction L1, it comes into contact with the pressed surface 25. After the first roller 4 makes contact, the pressing part 34 presses the pressed surface 25 through the first roller 4 (see reference). Figure 7 (See arrows D1 and D2). Thus, the torque in the first rotational direction L1 is transmitted to the output shaft 2, and the output shaft 2 rotates in the first rotational direction L1.

[0069] Furthermore, when the pressing part 34 presses the pressed surface 25 across the first roller 4, the portion of the side surface 35 that contacts the first roller 4 is not the inner side surface 351, but the outer side surface 352. The outer side surface 352 is formed to be approximately parallel to the pressed surface 25. Therefore, the load D1 acting on the first roller 4 from the outer side surface 352 is the normal vector of the pressed surface 25. As a result, the torque loss transmitted from the pressing part 34 to the output shaft 2 is minimal, and the torque is transmitted efficiently.

[0070] Furthermore, because the pressed surface 25 is inclined, the first roller 4 presses against the pressed surface 25 and moves radially outward (see reference). Figure 7 (arrow E). Therefore, the gap between the inner circumferential surface 10 of the fixing member 1 and the first roller 4 is small.

[0071] In addition, such as Figure 7 As shown, when the amount of downward sinking of the second roller 5 in the radial direction increases, it moves away from the pressing surface 37 of the second rotating body. Therefore, when the pressing part 34 presses the pressed surface 25 through the first roller 4, the second roller 5 does not receive a load from the pressing part 34.

[0072] Figure 8 This is a diagram illustrating the operating state of the power transmission device in Embodiment 1, specifically a diagram showing the time points at which the first roller begins to return in the second rotational direction. For example... Figure 8 As shown, when the torque input to the input shaft body 31 is released, the first roller 4 is pressed by the helical spring 50 and moves in the second rotational direction L2 (see reference). Figure 8 (arrow F). Then, when the first roller 4 moves to a certain extent in the second rotational direction L2, as... Figure 3 As shown, it is sandwiched between the cam surface 27 and the inner circumferential surface 10 (locked state).

[0073] Furthermore, an oil film of a certain thickness is formed on the inner circumferential surface 10 of the fixing member 1. That is, the oil film is also sandwiched between the inner circumferential surface 10 of the fixing member 1 and the first roller 4. Here, in order to lock the output shaft 2, the first roller 4 needs to shear the oil film. Assuming that the thickness of the oil film between the inner circumferential surface 10 and the first roller 4 is large, there is a possibility that the first roller 4 cannot easily shear the oil film, and the output shaft 2 will not be locked.

[0074] like Figure 7 As shown, when the first roller 4 presses against the pressed surface 25, the gap between the inner circumferential surface 10 and the first roller 4 decreases. That is, the thickness of the oil film sandwiched between the inner circumferential surface 10 and the first roller 4 decreases. Therefore, according to this embodiment, the first roller 4 can easily shear the oil film sandwiched between itself and the inner circumferential surface 10, and the output shaft 2 is reliably locked.

[0075] Furthermore, when the first roller 4 moves in the second rotational direction L2, the second roller 5, which abuts against the first roller 4, receives the load in the second rotational direction L2. The second roller 5 is lifted radially outward along the guide surface 28 (see reference). Figure 8 Arrow G). Thus, the second roller 5 abuts against the second rotating body of the pressing part 34 via the pressing surface 37 (see arrow G). Figure 3 ).

[0076] Figure 9 This is a diagram showing the time point at which torque (in the first rotation direction) begins to be input to the input shaft in the power transmission device of Embodiment 1 when an external force (in the first rotation direction) acts on the output shaft. Next, the case where an external force in the same direction (first rotation direction L1) acts on the output shaft 2 at the time point at which torque begins to be input to the input shaft 3 will be explained. It should be noted that the jerking phenomenon occurs because at the time when the locking state of the first roller 4 is released due to its movement in the first rotation direction L1, the output shaft 2 also rotates in the first rotation direction L1 by an external force (see reference). Figure 9 Arrow J1), the first roller 4 is again clamped by the inner circumferential surface 10 and the cam surface 27.

[0077] like Figure 9 As shown, at the start of torque input to the input shaft 3, when the pressing part 34 presses the second roller 5 between the first roller 4 and the guide surface 28, load B2 acts on the guide surface 28. This load B2 includes a component in the second rotational direction L2. Therefore, rotation of the output shaft 2 in the first rotational direction L1 is suppressed. That is, the first roller 4 is prevented from being clamped between the inner circumferential surface 10 and the cam surface 27 again, avoiding the occurrence of jerking.

[0078] Figure 10This is a graph showing the time point at which torque (in the first rotation direction) begins to be input to the input shaft in the power transmission device of Embodiment 1, under the condition that an external force (in the second rotation direction) acts on the output shaft. On the other hand, as... Figure 10 As shown, with an external force acting on the output shaft 2 in the opposite direction (second rotation direction L2), when torque (first rotation direction L1) is input to the input shaft 3, the pressing part 34 presses the first roller 4 across the second roller 5 (refer to arrows B and B1). Then, the first roller 4 moves and presses the pressed surface 25 towards the first rotation direction L1. As a result, the output shaft 2 rotates in the first rotation direction L1 (refer to arrow J2). Based on the above, the first roller 4 will not be caught between the inner circumferential surface 10 and the cam surface 27, and no jerking phenomenon occurs.

[0079] The power transmission device 100 of Embodiment 1 has been described above, but this disclosure is not limited to the examples described in Embodiment 1. For example, in Embodiment 1, an example using cylindrical rollers as the rotating body is given, but in this disclosure, ball bearings may also be used. Next, a modified example obtained by modifying a part of the power transmission device 100 of Embodiment 1 will be described. Furthermore, in the following description, the differences from the previously described power transmission device 100 will be emphasized.

[0080] (Variation Example 1)

[0081] Figure 11 This is an enlarged view obtained by magnifying one of the concave surfaces of the power transmission device of Modified Example 1. The point where the entire side surface 35A of the pressing part 34 of the power transmission device 100A of Modified Example 1 is planar differs from that of Embodiment 1. That is, the side surface 35A of Modified Example 1 does not have an outer side surface 352 that protrudes outward from the inner side surface 351.

[0082] Even in the power transmission device 100A of Modified Example 1, when the torque is input to the input shaft 3, the pressing part 34 presses the second roller 5 (refer to arrow B). Then, loads B1 and B2 are applied to the first roller 4 and the guide surface 28, such as causing them to peel apart. Therefore, even if an external force in the same direction as the torque input to the input shaft 3 is applied to the output shaft 2, the rotation of the output shaft 2 in the first rotation direction L1 is suppressed. Based on the above, the power transmission device 100A of Modified Example 1, like Embodiment 1, suppresses the first roller 4 from being clamped again by the inner circumferential surface 10 and the cam surface 27, avoiding the occurrence of jerking. Furthermore, according to Modified Example 1, like Embodiment 1, the torque required for unlocking can be reduced.

[0083] Figure 12This is a diagram showing the state in which the pressing part presses against the pressed surface through the first roller in the power transmission device of Modified Example 1. It should be noted that, according to the power transmission device 100A of Modified Example 1, the side surface 35A of the pressing part 34, which presses against the pressed surface through the first roller 4, is not parallel to the pressed surface 25. That is, the load K acting on the first roller 4 from the side surface 35A is not a normal vector to the pressed surface 25. Therefore, compared to Embodiment 1, the torque loss transmitted from the pressing part 34 to the output shaft 2 is greater.

[0084] (Variation Example 2)

[0085] Figure 13 This is an enlarged view obtained by magnifying one of the concave surfaces of the power transmission device in Modified Example 2. For example... Figure 13 As shown, the power transmission device 100B in Modification 2 differs from that in Modification 1 in the shape of the guide surface 28B. In Modification 2, the guide surface 28B is formed as an arc centered on the central axis X. It should be noted that the imaginary line W7 is the extension line of the load B2 acting on the guide surface 28B. Even in Modification 2, the load B2 acting on the guide surface 28B includes the second rotation direction L2, suppressing the rotation of the output shaft 2 towards the first rotation direction L1. That is, in Modification 2, jerking is less likely to occur. Furthermore, according to Modification 2, similar to Embodiment 1, the torque required for unlocking can be reduced.

[0086] It should be noted that if the load B2 of modified example 2 (refer to...) Figure 13 ) and the load B2 of Implementation Method 1 (refer to Figure 5 Comparing the two embodiments, the load B2 in Embodiment 1 is more circumferential. That is, compared with Modification 2, the torque acting on the second rotational direction L2 of the output shaft 2 in Embodiment 1 is greater. Therefore, Embodiment 1 is less prone to jerking and can reduce the torque required for unlocking, and is therefore preferred.

[0087] Figure 14 This is a diagram showing the state in which the pressing part presses the pressed surface across the second roller and the first roller in the power transmission device of Modified Example 2. Furthermore, according to the guide surface 28B of Modified Example 2, even if the second roller 5, pressed by the pressing surface 37 of the second rotating body, moves outward circumferentially, it does not sink (move) radially inward. That is, the distance between the pressing part 34 and the first roller 4 does not decrease, therefore, the side surface 35A does not contact the first roller 4. Therefore, as... Figure 14 As shown, the pressing part 34 presses the first roller 4 through the second roller 5, thereby transmitting torque to the output shaft 2.

[0088] (Modified Example 3, Modified Example 4)

[0089] Figure 15This is a partial cross-sectional view obtained by magnifying the area near the pressed surface in the power transmission device of Modified Example 3. Figure 16 This is an enlarged view obtained by magnifying one of the concave surfaces of the power transmission device in Modified Example 4. For example... Figure 15 As shown, the power transmission device 100C in Modified Example 3 differs from that in Embodiment 1 at the point where the hole 51C is not through. Furthermore, as... Figure 16 As shown, the power transmission device 100D in Modification 4 differs from Embodiment 1 in that it does not have a helical spring 50. Even in Modifications 3 and 4, the occurrence of jerking phenomena is avoided, just like in Embodiment 1.

[0090] The above descriptions of various modifications have been provided. In addition, the output shaft 2 in Embodiment 1 has three concave surfaces 23, but this disclosure does not specifically limit the number of concave surfaces 23. Furthermore, in Embodiment 1, the pressing portion 34 is separated from the first roller 4 in the initial state, but in this disclosure, the pressing portion 34 can also abut against the first roller 4. Accordingly, the first roller 4 receives the load B1 (refer to...) acting from the second roller 5. Figure 5 (etc.), and also receives load from the pressing part 34 and moves outward in a circumferential direction, and the locking state is released.

[0091] Next, the drive unit 5000 of the power transmission device 100 of Embodiment 1 will be described.

[0092] (Implementation Method 2)

[0093] Figure 17 This is a schematic diagram illustrating the configuration of the drive unit in Embodiment 2. (As shown...) Figure 17 As shown, the drive unit 5000 includes a motor 5001 and the aforementioned power transmission device 100. The motor 5001 is a device for generating torque. The output shaft (not shown) of the motor 5001 is connected to the input shaft body 31 of the power transmission device 100 (in... Figure 17 Not illustrated. See reference. Figure 2 )link.

[0094] Such a drive unit 5000 is used, for example, in electric sliders, robotic arms, lifting devices, conveying robots, electric mobility scooters, electric-assisted bicycles, electric mobile devices, trolleys, and strollers. In other words, the electric slider, etc., is connected to the output shaft body 21 of the power transmission device 100. Then, driven by the motor 5001 of the drive unit 500, torque is transmitted to the electric slider, etc., via the power transmission device 100.

[0095] On the other hand, even if an external force is applied to the electric slider, the output shaft 2 will not rotate, even if the force is transmitted to it. Therefore, the electric slider connected to the output shaft 2 will not rotate, move, or change its posture due to external forces. Therefore, according to the drive unit 5000, there is no need for an electromagnetic brake that limits rotation caused by external forces, thus reducing the amount of electricity used.

[0096] The above describes Embodiment 2. The drive unit 5000 of Embodiment 2 includes the power transmission device 100 described in Embodiment 1, but this disclosure may also include the power transmission device described in Modifications 1 to 4.

[0097] Figure 18 This is a schematic diagram illustrating the configuration of the drive unit in Modified Example 5. Furthermore, the drive unit 5000 of Embodiment 2 includes a motor 5001 and a power transmission device 100, but as... Figure 18 As shown, this disclosure can also be a drive unit 5000A of Modified Example 5, which includes a motor 5001, a power transmission device 100, a reducer 5002, and a sensor 5003 that detects the rotation angle of the output shaft of the motor 5001. The reducer 5002 is a device for increasing torque. Furthermore, in Modified Example 5, an electric slider or the like is connected to the output shaft 5004 of the reducer 5002.

[0098] It should be noted that this disclosure may also be a combination of the following.

[0099] (1) A power transmission device comprising: A ring-shaped fixing member having an inner circumferential surface; The output shaft has an outer peripheral surface facing the inner peripheral surface and a concave surface recessed radially inward from the outer peripheral surface. An input shaft having a pressing portion accommodated within the concave surface; A pair of first rotating bodies, housed within the concave surface, are arranged on opposite sides in the circumferential direction relative to the pressing portion; and A pair of second rotating bodies, with a diameter smaller than that of the first rotating body, are disposed between the first rotating body and the pressing part. The concave surface has: The bottom surface, extending circumferentially, is radially opposed to the inner circumferential surface; and A pair of pressed surfaces extend radially outward from both ends of the bottom surface in the circumferential direction. The bottom surface has: A pair of cam surfaces, for the first rotating body to be disposed radially outward; and A pair of guide surfaces for the second rotating body to be positioned radially outward. The distance between the cam surface and the inner circumferential surface gradually increases as the cam surface approaches the pressed surface. The distance between the portion of the cam surface near the guide surface and the inner circumferential surface is less than the diameter of the first rotating body. The distance between the portion of the cam surface near the pressed surface and the inner circumferential surface is greater than the diameter of the first rotating body. The second rotating body is sandwiched between the first rotating body, the guide surface, and the pressing part. When the pressing part moves from the central part in the circumferential direction of the concave surface to the outer side in the circumferential direction, the pressing part presses the second rotating body between the first rotating body and the guide surface.

[0100] (2) The power transmission device according to (1), wherein, The guide surface is positioned radially inward as it approaches the cam surface.

[0101] (3) The power transmission device according to (2), wherein, The pressing part has a side facing outward in a circumferential direction. At least a portion of the side surface is parallel to the pressed surface when the pressed surface is pressed through the first rotating body.

[0102] (4) The power transmission device according to (1), wherein, The guiding surface is formed as an arc centered on the central axis of the inner circumferential surface.

[0103] (5) The power transmission device according to any one of (1) to (4), wherein, The outer radial end of the pressed surface is positioned circumferentially outside the imaginary line drawn from the central axis of the inner circumferential surface to the inner radial end of the pressed surface, and the pressed surface is inclined circumferentially outward.

[0104] (6) The power transmission device according to any one of (1) to (5) comprises: An elastomer is disposed between the pressed surface and the first rotating body, and applies force to the pressing portion by the first rotating body.

Claims

1. A power transmission device, comprising: A ring-shaped fixing member having an inner circumferential surface; The output shaft has an outer peripheral surface facing the inner peripheral surface and a concave surface recessed radially inward from the outer peripheral surface. An input shaft having a pressing portion accommodated within the concave surface; A pair of first rotating bodies, housed within the concave surface, are arranged on opposite sides in the circumferential direction relative to the pressing portion; and A pair of second rotating bodies, with a diameter smaller than that of the first rotating body, are disposed between the first rotating body and the pressing part. The concave surface has: The bottom surface, extending circumferentially, is radially opposed to the inner circumferential surface; and A pair of pressed surfaces extend radially outward from both ends of the bottom surface in the circumferential direction. The bottom surface has: A pair of cam surfaces, for the first rotating body to be disposed radially outward; and A pair of guide surfaces for the second rotating body to be positioned radially outward. The distance between the cam surface and the inner circumferential surface gradually increases as the cam surface approaches the pressed surface. The distance between the portion of the cam surface near the guide surface and the inner circumferential surface is less than the diameter of the first rotating body. The distance between the portion of the cam surface near the pressed surface and the inner circumferential surface is greater than the diameter of the first rotating body. The second rotating body is sandwiched between the first rotating body, the guide surface, and the pressing part. When the pressing part moves from the central part in the circumferential direction of the concave surface to the outer side in the circumferential direction, the pressing part presses the second rotating body between the first rotating body and the guide surface.

2. The power transmission device according to claim 1, wherein, The guide surface is positioned radially inward as it approaches the cam surface.

3. The power transmission device according to claim 2, wherein, The pressing part has a side facing outward in a circumferential direction. At least a portion of the side surface is parallel to the pressed surface when the pressed surface is pressed through the first rotating body.

4. The power transmission device according to claim 1, wherein, The guiding surface is formed as an arc centered on the central axis of the inner circumferential surface.

5. The power transmission device according to any one of claims 1 to 4, wherein, The outer radial end of the pressed surface is positioned circumferentially outward from an imaginary line drawn from the central axis of the inner circumferential surface to the inner radial end of the pressed surface, and the pressed surface is inclined circumferentially outward.

6. The power transmission device according to any one of claims 1 to 4, comprising: An elastomer is disposed between the pressed surface and the first rotating body, and applies force to the pressing portion by the first rotating body.

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